Materials

Editorial

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32 pages, 6544 KiB

Open AccessEditorial

From Stochastic Foam to Designed Structure: Balancing Cost and Performance of Cellular Metals

by Dirk Lehmhus^1,2,*,†, Matej Vesenjak^3,†, Sven De Schampheleire^4,†

and Thomas Fiedler^5,†

¹ ISIS Sensorial Materials Scientific Centre, University of Bremen, 28359 Bremen, Germany

² MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany

³ Faculty of Mechanical Engineering, University of Maribor, 2000 Maribor, Slovenia

⁴ Department of Flow, Heat and Combustion Mechanics, Ghent University, 9000 Ghent, Belgium

⁵ School of Engineering, The University of Newcastle, Callaghan NSW 2308, Australia

^† These authors contributed equally to this work.

Materials 2017, 10(8), 922; https://doi.org/10.3390/ma10080922 - 8 Aug 2017

Cited by 89 | Viewed by 11715

Abstract

Over the past two decades, a large number of metallic foams have been developed. In recent years research on this multi-functional material class has further intensified. However, despite their unique properties only a limited number of large-scale applications have emerged. One important reason [...] Read more.

Over the past two decades, a large number of metallic foams have been developed. In recent years research on this multi-functional material class has further intensified. However, despite their unique properties only a limited number of large-scale applications have emerged. One important reason for this sluggish uptake is their high cost. Many cellular metals require expensive raw materials, complex manufacturing procedures, or a combination thereof. Some attempts have been made to decrease costs by introducing novel foams based on cheaper components and new manufacturing procedures. However, this has often yielded materials with unreliable properties that inhibit utilization of their full potential. The resulting balance between cost and performance of cellular metals is probed in this editorial, which attempts to consider cost not in absolute figures, but in relation to performance. To approach such a distinction, an alternative classification of cellular metals is suggested which centers on structural aspects and the effort of realizing them. The range thus covered extends from fully stochastic foams to cellular structures designed-to-purpose. Full article

(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)

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Research

Jump to: Editorial, Review

11 pages, 7198 KiB

Open AccessArticle

Characterization of the Micro-Abrasive Wear in Coatings of TaC-HfC/Au for Biomedical Implants

by Pablo Guzmán¹, Luis Yate², Mercy Sandoval¹, Jose Caballero¹ and Willian Aperador^1,*

¹ School of Engineering, Universidad Militar Nueva Granada, Carrera 11 #101-80, 49300 Bogotá, Colombia

² CIC biomaGUNE, Paseo Miramón 182, 20009 Donostia-San Sebastian, Spain

Materials 2017, 10(8), 842; https://doi.org/10.3390/ma10080842 - 25 Jul 2017

Cited by 6 | Viewed by 4606

Abstract

The object of this work was the deposition of a Ta-Hf-C thin film with a gold interlayer on stainless steel, via the physical vapor deposition (PVD) technique, in order to evaluate the properties of different systems subjected to micro-abrasive wear phenomena generated by [...] Read more.

The object of this work was the deposition of a Ta-Hf-C thin film with a gold interlayer on stainless steel, via the physical vapor deposition (PVD) technique, in order to evaluate the properties of different systems subjected to micro-abrasive wear phenomena generated by alumina particles in Ringer's solution. The surface characterization was performed using a scanning electron microscope (SEM) and atomic force microscope (AFM). The crystallographic phases exhibited for each coating were obtained by X-ray diffraction (XRD). As a consequence of modifying the composition of Ta-Hf there was evidence of an improvement in the micro-abrasive wear resistance and, for each system, the wear constants that confirm the enhancement of the surface were calculated. Likewise, these surfaces can be bioactive, generating an alternative to improve the biological fixation of the implants, therefore, the coatings of TaC-HfC/Au contribute in the development of the new generation of orthopedic implants. Full article

(This article belongs to the Section Advanced Materials Characterization)

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14 pages, 4564 KiB

Open AccessArticle

Preparation and Characterization of Soybean Oil-Based Polyurethanes for Digital Doming Applications

by Vincenzo Pantone¹, Amelita Grazia Laurenza², Cosimo Annese³, Roberto Comparelli⁴

, Francesco Fracassi², Paola Fini⁴

, Angelo Nacci^2,3

, Antonella Russo¹, Caterina Fusco^3,*

and Lucia D’Accolti^2,3,*

¹ Greenswitch s.r.l., 71013 Ferrandina (MT), Italy

² Dipartimento di Chimica, Università di Bari “A. Moro”, Via Orabona 4, 70126 Bari, Italy

³ ICCOM-CNR, SS Bari, Via Orabona 4, 70126 Bari, Italy

⁴ IPCF-CNR, SS Bari, Via E. Orabona 4, 70125 Bari, Italy

Materials 2017, 10(8), 848; https://doi.org/10.3390/ma10080848 - 25 Jul 2017

Cited by 17 | Viewed by 5768

Abstract

Polyurethane-resin doming is currently one of the fastest growing markets in the field of industrial graphics and product identification. Semi-rigid bio-based polyurethanes were prepared deriving from soybean oil as a valuable alternative to fossil materials for digital doming and applied to digital mosaic [...] Read more.

Polyurethane-resin doming is currently one of the fastest growing markets in the field of industrial graphics and product identification. Semi-rigid bio-based polyurethanes were prepared deriving from soybean oil as a valuable alternative to fossil materials for digital doming and applied to digital mosaic technology. Bio-resins produced can favorably compete with the analogous fossil polymers, giving high-quality surface coatings (ascertained by SEM analyses). In addition, polyurethane synthesis was accomplished by using a mercury- and tin-free catalyst (the commercially available zinc derivative K22) bringing significant benefits in terms of cost efficiency and eco-sustainability. Full article

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17 pages, 7060 KiB

Open AccessFeature PaperArticle

Nanostructured ZnO in a Metglas/ZnO/Hemoglobin Modified Electrode to Detect the Oxidation of the Hemoglobin Simultaneously by Cyclic Voltammetry and Magnetoelastic Resonance

by Ariane Sagasti¹, Nikolaos Bouropoulos^2,3,*

, Dimitris Kouzoudis⁴, Apostolos Panagiotopoulos²

, Emmanuel Topoglidis²

and Jon Gutiérrez^1,5

¹ BCMaterials, Ibaizabal Bidea, Edificio 500, Parque Tecnológico de Bizkaia, 48160 Derio, Spain

² Department of Materials Science, University of Patras, 26504 Patras, Greece

³ Foundation for Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes, 26504 Patras, Greece

⁴ Department of Chemical Engineering, University of Patras, 26504 Patras, Greece

⁵ Department of Electricity and Electronics, Universidad del País Vasco/Euskal Herriko Unibertsitatea, 48080 Bilbao, Spain

Materials 2017, 10(8), 849; https://doi.org/10.3390/ma10080849 - 25 Jul 2017

Cited by 17 | Viewed by 8888

Abstract

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb’s electrochemical behavior towards hydrogen peroxide. Hb oxidation by H₂O₂ was monitored simultaneously by two different [...] Read more.

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb’s electrochemical behavior towards hydrogen peroxide. Hb oxidation by H₂O₂ was monitored simultaneously by two different techniques: Cyclic Voltammetry (CV) and Magnetoelastic Resonance (MR). The Metglas/ZnO/Hb system was simultaneously used as a working electrode for the CV scans and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The ZnO nanoparticles for the ZnO layer were grown hydrothermally and fully characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and photoluminescence (PL). Additionally, the ZnO layer’s elastic modulus was measured using a new method, which makes use of the Metglas substrate. For the detection experiments, the electrochemical cell was performed with a glass vial, where the three electrodes (working, counter and reference) were immersed into PBS (Phosphate Buffer Solution) solution and small H₂O₂ drops were added, one at a time. CV scans were taken every 30 s and 5 min after the addition of each drop and meanwhile a magnetoelastic measurement was taken by the external coils. The CV plots reveal direct electrochemical behavior of Hb and display good electrocatalytic response to the reduction of H₂O₂. The measured catalysis currents increase linearly with the H₂O₂ concentration in a wide range of 25–350 μM with a correlation coefficient 0.99. The detection limit is 25–50 μM. Moreover, the Metglas/ZnO/Hb electrode displays rapid response (30 s) to H₂O₂, and exhibits good stability and reproducibility of the measurements. On the other hand, the magnetoelastic measurements show a small linear mass increase versus the H₂O₂ concentration with a slope of 152 ng/μM, which is probably due to H₂O₂ adsorption in ZnO during the electrochemical reaction. No such effects were detected during the control experiment when only PBS solution was present for a long time. Full article

(This article belongs to the Special Issue Zinc Oxide Nanostructures: Synthesis and Characterization)

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22 pages, 2003 KiB

Open AccessFeature PaperArticle

Performance of Poly(lactic acid) Surface Modified Films for Food Packaging Application

by Valentina Siracusa^1,*

, Marco Dalla Rosa² and Alexey L. Iordanskii³

¹ Department of Chemical Science, University of Catania, Viale A. Doria 6, 95125 Catania (CT), Italy

² Interdepartmental Centre for Agri-Food Industrial Research, Alma Mater Studiorum, University of Bologna, Piazza Goidanich 60, 47521 Cesena (FC), Italy

³ Semenov Institute of Chemical Physics, Kosygin str. 4, 119991 Moscow, Russia

Materials 2017, 10(8), 850; https://doi.org/10.3390/ma10080850 - 25 Jul 2017

Cited by 17 | Viewed by 5904

Abstract

Five Poly(lactic acid) (PLA) film samples were analyzed to study the gas barrier behavior, thermal stability and mechanical performance for food packaging application. O₂, CO₂, N₂, N₂O, and C₂H₄ pure gases; Air; [...] Read more.

Five Poly(lactic acid) (PLA) film samples were analyzed to study the gas barrier behavior, thermal stability and mechanical performance for food packaging application. O₂, CO₂, N₂, N₂O, and C₂H₄ pure gases; Air; and Modified Atmosphere (MA, 79% N₂O/21% O₂) were used to analyze the influence of the chemical structure, storage temperature and crystalline phase on the gas barrier behavior. The kinetic of the permeation process was investigated at different temperatures, ranging from 5 °C to 40 °C. Annealing thermal treatment on the samples led to the crystalline percentage, influencing especially the gas solubility process. Thermal properties such as T_g and χ_c, and mechanical properties such as tensile strength and modulus were remarkably improved with surface PLA modification. A more pronounced reinforcing effect was noted in the case of metallization, as well as improved gas barrier performance. Tensile testing and tensile cycling tests confirmed the rigidity of the films, with about a 20% loss of elasticity after 25 cycles loading. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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21 pages, 17023 KiB

Open AccessArticle

Effect of Alternating Current on the Cathodic Protection and Interface Structure of X80 Steel

by Huiru Wang¹, Cuiwei Du^1,*, Zhiyong Liu¹, Luntao Wang¹ and De Ding²

¹ Corrosion & Protection Center, University of Science & Technology Beijing, Beijing 100083, China

² Shanxi Electric Power Research Institute, State Grid Corporation of China, Xi’an 710054, China

Materials 2017, 10(8), 851; https://doi.org/10.3390/ma10080851 - 25 Jul 2017

Cited by 44 | Viewed by 6507

Abstract

This study employs potential-monitoring techniques, cyclic voltammetry tests, alternating current (AC) voltammetry methods, and surface characterization to investigate the AC corrosion of cathodically protected X80 pipeline steel. In a non-passive neutral solution at pH 7.2, a sufficiently negative potential completely protects steel at [...] Read more.

This study employs potential-monitoring techniques, cyclic voltammetry tests, alternating current (AC) voltammetry methods, and surface characterization to investigate the AC corrosion of cathodically protected X80 pipeline steel. In a non-passive neutral solution at pH 7.2, a sufficiently negative potential completely protects steel at an AC current density of 100 A/m². In an alkaline solution at pH 9.6, more serious AC corrosion occurs at more negative cathodic protection (CP) potential, whereas without CP the steel suffers negligible corrosion. In addition, the interface capacitance increases with AC amplitude. Based on these results, the AC corrosion mechanisms that function under various conditions are analyzed and described. Full article

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11 pages, 4102 KiB

Open AccessArticle

Evaluation of Toluene Adsorption Performance of Mortar Adhesives Using Porous Carbon Material as Adsorbent

by Seunghwan Wi¹

, Seong Jin Chang¹, Su-Gwang Jeong¹, Jongki Lee¹, Taeyeon Kim², Kyung-Won Park³, Dong Ryeol Lee⁴ and Sumin Kim^1,*

¹ Building Environment & Materials Lab, School of Architecture, Soongsil University, Seoul 06978, Korea

² Department of Architectural Engineering, Yonsei University, Seoul 03722, Korea

³ Department of Chemical Engineering, Soongsil University, Seoul 06978, Korea

⁴ Department of Physics, Soongsil University, Seoul 06978, Korea

Materials 2017, 10(8), 853; https://doi.org/10.3390/ma10080853 - 26 Jul 2017

Cited by 8 | Viewed by 3734

Abstract

Porous carbon materials are advantageous in adsorbing pollutants due to their wide range of specific surface areas, pore diameter, and pore volume. Among the porous carbon materials in the current study, expanded graphite, xGnP, xGnP C-300, xGnP C-500, and xGnP C-750 were prepared [...] Read more.

Porous carbon materials are advantageous in adsorbing pollutants due to their wide range of specific surface areas, pore diameter, and pore volume. Among the porous carbon materials in the current study, expanded graphite, xGnP, xGnP C-300, xGnP C-500, and xGnP C-750 were prepared as adsorbent materials. Brunauer–Emmett–Teller (BET) analysis was conducted to select the adsorbent material through the analysis of the specific surface area, pore size, and pore volume of the prepared porous carbon materials. Morphological analysis using SEM was also performed. The xGnP C-500 as adsorbent material was applied to a mortar adhesive that is widely used in the installation of interior building materials. The toluene adsorption performances of the specimens were evaluated using 20 L small chamber. Furthermore, the performance of the mortar adhesive, as indicated by the shear bond strength, length change rate, and water retention rate, was analyzed according to the required test method specified in the Korean standards. It was confirmed that for the mortar adhesives prepared using the xGnP C-500 as adsorbent material, the toluene adsorption performance was excellent and satisfied the required physical properties. Full article

(This article belongs to the Section Porous Materials)

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16 pages, 6395 KiB

Open AccessArticle

Shallow V-Shape Nanostructured Pit Arrays in Germanium Using Aqua Regia Electroless Chemical Etching

by Ibtihel Chaabane^1,2, Debika Banerjee¹, Oualid Touayar² and Sylvain G. Cloutier^1,*

¹ Department of Electrical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Ouest, Montréal, Québec, QC H3C 1K3, Canada

² Department of Physics and Instrumentation, National Institute of Applied Science and Technologies, Charguia, Tunis 1080, Tunisia

Materials 2017, 10(8), 854; https://doi.org/10.3390/ma10080854 - 26 Jul 2017

Cited by 6 | Viewed by 5045

Abstract

Due to its high refractive index, reflectance is often a problem when using Germanium for optoelectronic devices integration. In this work, we propose an effective and low-cost nano-texturing method for considerably reducing the reflectance of bulk Germanium. To do so, uniform V-shape pit [...] Read more.

Due to its high refractive index, reflectance is often a problem when using Germanium for optoelectronic devices integration. In this work, we propose an effective and low-cost nano-texturing method for considerably reducing the reflectance of bulk Germanium. To do so, uniform V-shape pit arrays are produced by wet electroless chemical etching in a 3:1 volume ratio of highly-concentrated hydrochloridric and nitric acids or so-called aqua regia bath using immersion times ranging from 5 to 60 min. The resulting pit morphology, the crystalline structure of the surface and the changes in surface chemistry after nano-patterning are all investigated. Finally, broadband near-infrared reflectance measurements confirm a significant reduction using this simple wet etching protocol, while maintaining a crystalline, dioxide-free, and hydrogen-passivated surface. It is important to mention that reflectance could be further reduced using deeper pits. However, most optoelectronic applications such as photodetectors and solar cells require relatively shallow patterning of the Germanium to allow formation of a pn-junction close to the surface. Full article

(This article belongs to the Section Advanced Materials Characterization)

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16 pages, 8504 KiB

Open AccessArticle

Effect of Hydroxyapatite on the Mechanical Properties and Corrosion Behavior of Mg-Zn-Y Alloy

by Chun Chiu¹, Chih-Te Lu¹, Shih-Hsun Chen¹

and Keng-Liang Ou^2,3,4,5,*

¹ Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan

² Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan

³ Department of Dentistry, Cathay General Hospital, Taipei 106, Taiwan

⁴ Department of Dentistry, Taipei Medical University-Shuang Ho Hospital, New Taipei City 235, Taiwan

⁵ 3D Global Biotech Inc., New Taipei City 221, Taiwan

Materials 2017, 10(8), 855; https://doi.org/10.3390/ma10080855 - 26 Jul 2017

Cited by 22 | Viewed by 4766

Abstract

Mg-Zn-Y alloys with a long period stacking ordered (LPSO) phase are potential candidates for biodegradable implants; however, an unfavorable degradation rate has limited their applications. Hydroxyapatite (HA) has been shown to enhance the corrosion resistance of Mg alloys. In this study, Mg₉₇ [...] Read more.

Mg-Zn-Y alloys with a long period stacking ordered (LPSO) phase are potential candidates for biodegradable implants; however, an unfavorable degradation rate has limited their applications. Hydroxyapatite (HA) has been shown to enhance the corrosion resistance of Mg alloys. In this study, Mg₉₇Zn₁Y₂-0.5 wt% HA composite was synthesized and solution treated at 500 °C for 10 h. The corrosion behavior of the composite was studied by electrochemical and immersion tests, while the mechanical properties were investigated by a tensile test. Addition of HA particles improves the corrosion resistance of Mg₉₇Zn₁Y₂ alloy without sacrificing tensile strength. The improved corrosion resistance is due to the formation of a compact Ca-P surface layer and a decrease of the volume fraction of the LPSO phase, both resulting from the addition of HA. After solution-treatment, the corrosion resistance of the composite decreases. This is due to the formation of a more extended LPSO phase, which weakens its role as a corrosion barrier in protecting the Mg matrix. Full article

(This article belongs to the Section Biomaterials)

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9 pages, 1550 KiB

Open AccessArticle

Impacts of the Oxygen Precursor on the Interfacial Properties of La_xAl_yO Films Grown by Atomic Layer Deposition on Ge

by Lu Zhao

, Hongxia Liu^*

, Xing Wang, Yongte Wang and Shulong Wang

Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Education, School of Microelectronics, Xidian University, Xi’an 710071, China

Materials 2017, 10(8), 856; https://doi.org/10.3390/ma10080856 - 26 Jul 2017

Cited by 3 | Viewed by 3551

Abstract

Amorphous La_xAl_yO films were grown on n-type Ge substrate by atomic layer deposition using O₃ and H₂O as oxidant, respectively. A comparison of the XPS results indicated that a thicker interfacial layer with the component of [...] Read more.

Amorphous La_xAl_yO films were grown on n-type Ge substrate by atomic layer deposition using O₃ and H₂O as oxidant, respectively. A comparison of the XPS results indicated that a thicker interfacial layer with the component of LaGeO_x and GeO_x was formed at O₃-based La_xAl_yO/Ge interface, causing lower band gap value as well as the conduction band offset (CBO) value relative to Ge substrate for O₃-based La_xAl_yO film, with a concomitant degeneration in the interfacial properties. In contrast, for the H₂O-based film, the leakage current of more than one order of magnitude less than that of O₃-based La_xAl_yO film was obtained. All the results indicated that H₂O is a more appropriate oxidant for improving the interfacial properties in the atomic-layer-deposited La_xAl_yO dielectric on Ge. Full article

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13 pages, 13951 KiB

Open AccessArticle

Decreasing Bio-Degradation Rate of the Hydrothermal-Synthesizing Coated Mg Alloy via Pre-Solid-Solution Treatment

by Dan Song^1,2, Cheng Li¹, Liwen Zhang³, Xiaolong Ma³, Guanghui Guo¹, Fan Zhang^1,4, Jinghua Jiang^1,2,* and Aibin Ma^1,2,*

¹ College of Mechanics and Materials, Hohai University, Nanjing 210098, China

² Suqian Research Institute of Hohai University, Suqian 223800, China

³ Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA

⁴ Department of Materials Science and Engineering, Kyushu University, Fukuoka 819-0395, Japan

Materials 2017, 10(8), 858; https://doi.org/10.3390/ma10080858 - 27 Jul 2017

Cited by 8 | Viewed by 4110

Abstract

In this study, we report an effective approach, pre-solid solution (SS) treatment, to reduce the in-vitro bio-degradation rate of the hydrothermal-synthesizing coated Mg–2Zn–Mn–Ca–Ce alloy in Hanks’ solution. Pre-SS treatment alters the microstructure of alloys, which benefits the corrosion resistances of the substrate itself [...] Read more.

In this study, we report an effective approach, pre-solid solution (SS) treatment, to reduce the in-vitro bio-degradation rate of the hydrothermal-synthesizing coated Mg–2Zn–Mn–Ca–Ce alloy in Hanks’ solution. Pre-SS treatment alters the microstructure of alloys, which benefits the corrosion resistances of the substrate itself and the formed coating as well. The micro-galvanic corrosion between the secondary phase (cathode) and the α-Mg phase (anode) is relieved due to the reduction of the secondary phase. Meanwhile, coating formed on the SS-treated alloy was compacter than that on as-cast alloy, which provides better protection against initial corrosion. Full article

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12 pages, 6828 KiB

Open AccessArticle

Er-Doped LiNi_0.5Mn_1.5O₄ Cathode Material with Enhanced Cycling Stability for Lithium-Ion Batteries

by Shanshan Liu¹, Hongyuan Zhao^1,*, Ming Tan¹, Youzuo Hu¹, Xiaohui Shu¹, Meiling Zhang¹, Bing Chen^1,2,* and Xingquan Liu^1,*

¹ R&D Center for New Energy Materials and Devices, State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China

² Xinyun Electronic Comp. & Dev. Co. Ltd, China Zhenhua Group, Guiyang 550018, China

Materials 2017, 10(8), 859; https://doi.org/10.3390/ma10080859 - 27 Jul 2017

Cited by 21 | Viewed by 5925

Abstract

The Er-doped LiNi_0.5Mn_1.5O₄ (LiNi_0.495Mn_1.495Er_0.01O₄) sample was successfully prepared by citric acid-assisted sol-gel method with erbium oxide as an erbium source for the first time. Compared with the undoped sample, the [...] Read more.

The Er-doped LiNi_0.5Mn_1.5O₄ (LiNi_0.495Mn_1.495Er_0.01O₄) sample was successfully prepared by citric acid-assisted sol-gel method with erbium oxide as an erbium source for the first time. Compared with the undoped sample, the Er-doped LiNi_0.5Mn_1.5O₄ sample maintained the basic spinel structure, suggesting that the substitution of Er³⁺ ions for partial nickel and manganese ions did not change the intrinsic structure of LiNi_0.5Mn_1.5O₄. Moreover, the Er-doped LiNi_0.5Mn_1.5O₄ sample showed better size distribution and regular octahedral morphology. Electrochemical measurements indicated that the Er-doping could have a positive impact on the electrochemical properties. When cycled at 0.5 C, the Er-doped LiNi_0.5Mn_1.5O₄ sample exhibited an initial discharge capacity of 120.6 mAh·g⁻¹, and the capacity retention of this sample reached up to 92.9% after 100 cycles. As the charge/discharge rate restored from 2.0 C to 0.2 C, the discharge capacity of this sample still exhibited 123.7 mAh·g⁻¹ with excellent recovery rate. Since the bonding energy of Er-O (615 kJ·mol⁻¹) was higher than that of Mn-O (402 kJ·mol ⁻¹) and Ni-O (392 kJ·mol⁻¹), these outstanding performance could be attributed to the increased structure stability as well as the reduced aggregation behavior and small charge transfer resistance of the Er-doped LiNi_0.5Mn_1.5O₄. Full article

(This article belongs to the Section Energy Materials)

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7 pages, 3685 KiB

Open AccessArticle

Ion Beam Modification of Carbon Nanotube Yarn in Air and Vacuum

by Jonathan G. Gigax¹, Philip D. Bradford² and Lin Shao^1,*

¹ Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843, USA

² Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695, USA

Materials 2017, 10(8), 860; https://doi.org/10.3390/ma10080860 - 27 Jul 2017

Cited by 9 | Viewed by 4217

Abstract

We studied the effects ion beam irradiation on carbon nanotube (CNT) yarns. CNT yarn was fabricated by drawing and spinning CNT sheets from a vertically aligned CNT forest. The yarn was irradiated by 2.5 MeV protons in either vacuum or air. Irradiation in [...] Read more.

We studied the effects ion beam irradiation on carbon nanotube (CNT) yarns. CNT yarn was fabricated by drawing and spinning CNT sheets from a vertically aligned CNT forest. The yarn was irradiated by 2.5 MeV protons in either vacuum or air. Irradiation in air was achieved by directing the proton beam through a 0.025 mm thick Ti window. Irradiation in vacuum occurred at a pressure of <10⁻⁶ torr at room temperature and at an elevated temperature of 600 °C. Tensile testing revealed that CNT yarn irradiated in air increased in tensile strength with increasing proton fluence. For yarn irradiated in vacuum, however, the strength decreased with increasing fluence. We believe that irradiation-induced excitation and trapping/bonding of gas atoms between tubes may play a role for the mechanical property changes. Full article

(This article belongs to the Special Issue Ion Beam Analysis, Modification, and Irradiation of Materials)

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19 pages, 11702 KiB

Open AccessArticle

Relationship between Microstructure and Corrosion Behavior of Martensitic High Nitrogen Stainless Steel 30Cr15Mo1N at Different Austenitizing Temperatures

by Zhouhua Jiang¹, Hao Feng¹, Huabing Li^1,*

, Hongchun Zhu¹, Shucai Zhang¹, Binbin Zhang¹, Yu Han¹, Tao Zhang² and Dake Xu²

¹ School of Metallurgy, Northeastern University, Shenyang 110819, China

² School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China

Materials 2017, 10(8), 861; https://doi.org/10.3390/ma10080861 - 27 Jul 2017

Cited by 45 | Viewed by 6859

Abstract

The relationship between microstructure and corrosion behavior of martensitic high nitrogen stainless steel 30Cr15Mo1N at different austenitizing temperatures was investigated by microscopy observation, electrochemical measurement, X-ray photoelectron spectroscopy analysis and immersion testing. The results indicated that finer Cr-rich M₂N dispersed more [...] Read more.

The relationship between microstructure and corrosion behavior of martensitic high nitrogen stainless steel 30Cr15Mo1N at different austenitizing temperatures was investigated by microscopy observation, electrochemical measurement, X-ray photoelectron spectroscopy analysis and immersion testing. The results indicated that finer Cr-rich M₂N dispersed more homogeneously than coarse M₂₃C₆, and the fractions of M₂₃C₆ and M₂N both decreased with increasing austenitizing temperature. The Cr-depleted zone around M₂₃C₆ was wider and its minimum Cr concentration was lower than M₂N. The metastable pits initiated preferentially around coarse M₂₃C₆ which induced severer Cr-depletion, and the pit growth followed the power law. The increasing of austenitizing temperature induced fewer metastable pit initiation sites, more uniform element distribution and higher contents of Cr, Mo and N in the matrix. In addition, the passive film thickened and Cr₂O₃, Cr³⁺ and CrN enriched with increasing austenitizing temperature, which enhanced the stability of the passive film and repassivation ability of pits. Therefore, as austenitizing temperature increased, the metastable and stable pitting potentials increased and pit growth rate decreased, revealing less susceptible metastable pit initiation, larger repassivation tendency and higher corrosion resistance. The determining factor of pitting potentials could be divided into three stages: dissolution of M₂₃C₆ (below 1000 °C), dissolution of M₂N (from 1000 to 1050 °C) and existence of a few undissolved precipitates and non-metallic inclusions (above 1050 °C). Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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18 pages, 5237 KiB

Open AccessArticle

Influence of Microencapsulated Phase Change Material (PCM) Addition on (Micro) Mechanical Properties of Cement Paste

by Branko Šavija

, Hongzhi Zhang^*

and Erik Schlangen

Microlab, Delft University of Technology, 2628 CN Delft, The Netherlands

Materials 2017, 10(8), 863; https://doi.org/10.3390/ma10080863 - 27 Jul 2017

Cited by 55 | Viewed by 7336

Abstract

Excessive cracking can be a serious durability problem for reinforced concrete structures. In recent years, addition of microencapsulated phase change materials (PCMs) to concrete has been proposed as a possible solution to crack formation related to temperature gradients. However, the addition of PCM [...] Read more.

Excessive cracking can be a serious durability problem for reinforced concrete structures. In recent years, addition of microencapsulated phase change materials (PCMs) to concrete has been proposed as a possible solution to crack formation related to temperature gradients. However, the addition of PCM microcapsules to cementitious materials can have some drawbacks, mainly related to strength reduction. In this work, a range of experimental techniques has been used to characterize the microcapsules and their effect on properties of composite cement pastes. On the capsule level, it was shown that they are spherical, enabling good distribution in the material during the mixing process. Force needed to break the microcapsules was shown to depend on the capsule diameter and the temperature, i.e., whether it is below or above the phase change temperature. On the cement paste level, a marked drop of compressive strength with increasing PCM inclusion level was observed. The indentation modulus has also shown to decrease, probably due to the capsules themselves, and to a lesser extent due to changes in porosity caused by their inclusion. Finally, a novel micro-cube splitting technique was used to characterize the tensile strength of the material on the micro-meter length scale. It was shown that the strength decreases with increasing PCM inclusion percentage, but this is accompanied by a decrease in measurement variability. This study will contribute to future developments of cementitious composites incorporating phase change materials for a variety of applications. Full article

(This article belongs to the Special Issue Advanced Nanoindentation in Materials)

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19 pages, 4225 KiB

Open AccessArticle

Selective Laser Sintering of Nano Al₂O₃ Infused Polyamide

by Anthony Warnakula and Sarat Singamneni^*

Mechanical Engineering Department, Auckland University of Technology, Auckland 1010, New Zealand

Materials 2017, 10(8), 864; https://doi.org/10.3390/ma10080864 - 27 Jul 2017

Cited by 25 | Viewed by 5200

Abstract

Nano Al₂O₃ polyamide composites are evaluated for processing by selective laser sintering. A thermal characterization of the polymer composite powders allowed us to establish the possible initial settings. Initial experiments are conducted to identify the most suitable combinations of process [...] Read more.

Nano Al₂O₃ polyamide composites are evaluated for processing by selective laser sintering. A thermal characterization of the polymer composite powders allowed us to establish the possible initial settings. Initial experiments are conducted to identify the most suitable combinations of process parameters. Based on the results of the initial trials, more promising ranges of different process parameters could be identified. The post sintering characterization showed evidence of sufficient inter-particle sintering and intra-layer coalescence. While the inter-particle coalescence gradually improved, the porosity levels slightly decreased with increasing laser power. The nano-filler particles tend to agglomerate around the beads along the solid tracks, possibly due to Van der Walls forces. The tensile stress results showed an almost linear increase with increasing nano-filler content. Full article

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21 pages, 1825 KiB

Open AccessArticle

On Critical States, Rupture States and Interlocking Strength of Granular Materials

by Chris M. Szalwinski

302-100 Quebec Avenue, Toronto, ON M6P4B8, Canada

Materials 2017, 10(8), 865; https://doi.org/10.3390/ma10080865 - 27 Jul 2017

Cited by 9 | Viewed by 6682

Abstract

The Mohr-Coulomb theory of strength identifies cohesion and internal friction as the two principal contributions to the shear strength of a granular material. The contribution of cohesion in over-compacted granular materials has been challenged and replacing cohesion with interlocking has been proposed. A [...] Read more.

The Mohr-Coulomb theory of strength identifies cohesion and internal friction as the two principal contributions to the shear strength of a granular material. The contribution of cohesion in over-compacted granular materials has been challenged and replacing cohesion with interlocking has been proposed. A theory of rupture strength that includes interlocking is derived herein. The physics-chemistry concept of critical state is elaborated to accommodate granular materials, based on empirical definitions established in the fields of soil mechanics and bulk solids’ flow. A surface in state space, called the critical compaction surface, separates over-compacted states from lightly compacted states. The intersection of this surface with the Mohr-Coulomb envelope forms the critical state surface for a granular material. The rupture strength of an over-compacted granular material is expressed as the sum of cohesion, internal friction and interlocking strength. Interlocking strength is the shear strength contribution due to over-compaction and vanishes at critical state. The theory allows migrations from one critical state to another. Changes in specific volume during such migrations are related to changes in mean-normal effective stress and uncoupled from changes in shearing strain. The theory is reviewed with respect to two established research programs and underlying assumptions are identified. Full article

(This article belongs to the Special Issue Granular Materials)

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17 pages, 2675 KiB

Open AccessArticle

Output-Based Structural Damage Detection by Using Correlation Analysis Together with Transmissibility

by Yun-Lai Zhou¹

, Hongyou Cao^2,*, Quanmin Liu³ and Magd Abdel Wahab^4,5

¹ Department of Civil and Environmental Engineering, National University of Singapore, Singapore 117576, Singapore

² School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, China

³ Engineering Research Center of Railway Environmental Vibration and Noise of the Ministry of Education, East China Jiaotong University, Nanchang 330013, China

⁴ Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang 550000, Vietnam

⁵ Soete Laboratory, Faculty of Engineering and Architecture, Ghent University, Technologiepark Zwijnaarde 903, B-9052 Zwijnaarde, Belgium

Materials 2017, 10(8), 866; https://doi.org/10.3390/ma10080866 - 27 Jul 2017

Cited by 24 | Viewed by 4798

Abstract

Output-based structural damage detection is becoming increasingly appealing due to its potential in real engineering applications without any restriction regarding excitation measurements. A new transmissibility-based damage detection approach is presented in this study by combining transmissibility with correlation analysis in order to strengthen [...] Read more.

Output-based structural damage detection is becoming increasingly appealing due to its potential in real engineering applications without any restriction regarding excitation measurements. A new transmissibility-based damage detection approach is presented in this study by combining transmissibility with correlation analysis in order to strengthen its performance in discriminating damaged from undamaged scenarios. From this perspective, damage detection strategies are hereafter established by constructing damage-sensitive indicators from a derived transmissibility. A cantilever beam is numerically analyzed to verify the feasibility of the proposed damage detection procedure, and an ASCE (American Society of Civil Engineers) benchmark is henceforth used in the validation for its application in engineering structures. The results of both studies reveal a good performance of the proposed methodology in identifying damaged states from intact states. The comparison between the proposed indicator and the existing indicator also affirms its applicability in damage detection, which might be adopted in further structural health monitoring systems as a discrimination criterion. This study contributed an alternative criterion for transmissibility-based damage detection in addition to the conventional ones. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)

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13 pages, 25126 KiB

Open AccessArticle

Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

by David Van der Heggen¹

, Jonas J. Joos¹

, Diana C. Rodríguez Burbano², John A. Capobianco² and Philippe F. Smet^1,*

¹ Lumilab, Department of Solid State Sciences, Ghent University, Krijgslaan 281 S1, 9000 Gent, Belgium

² Department of Chemistry and Biochemistry and Center for Nanoscience Research, Concordia University, Montreal, QC H4B 1R6, Canada

Materials 2017, 10(8), 867; https://doi.org/10.3390/ma10080867 - 28 Jul 2017

Cited by 56 | Viewed by 8546

Abstract

The performance of a persistent phosphor is often determined by comparing luminance decay curves, expressed in cd/m

^{2}

. However, these photometric units do not enable a straightforward, objective comparison between different phosphors in terms of the total number of emitted photons, as [...] Read more.

The performance of a persistent phosphor is often determined by comparing luminance decay curves, expressed in cd/m

^{2}

. However, these photometric units do not enable a straightforward, objective comparison between different phosphors in terms of the total number of emitted photons, as these units are dependent on the emission spectrum of the phosphor. This may lead to incorrect conclusions regarding the storage capacity of the phosphor. An alternative and convenient technique of characterizing the performance of a phosphor was developed on the basis of the absolute storage capacity of phosphors. In this technique, the phosphor is incorporated in a transparent polymer and the measured afterglow is converted into an absolute number of emitted photons, effectively quantifying the amount of energy that can be stored in the material. This method was applied to the benchmark phosphor SrAl

_{2}

O

_{4}

:Eu,Dy and to the nano-sized phosphor CaS:Eu. The results indicated that only a fraction of the Eu ions (around 1.6% in the case of SrAl

_{2}

O

_{4}

:Eu,Dy) participated in the energy storage process, which is in line with earlier reports based on X-ray absorption spectroscopy. These findings imply that there is still a significant margin for improving the storage capacity of persistent phosphors. Full article

(This article belongs to the Special Issue Techniques and Methods for Advanced Characterization of Luminescent Materials)

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15 pages, 3085 KiB

Open AccessArticle

Construction and Characterization of a Chitosan-Immobilized-Enzyme and β-Cyclodextrin-Included-Ferrocene-Based Electrochemical Biosensor for H₂O₂ Detection

by Wenbo Dong^1,†, Kaiyin Wang^2,†, Yu Chen^1,*, Weiping Li², Yanchun Ye² and Shaohua Jin¹

¹ School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081, China

² School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China

^† These authors contributed equally to this work

Materials 2017, 10(8), 868; https://doi.org/10.3390/ma10080868 - 28 Jul 2017

Cited by 29 | Viewed by 6907

Abstract

An electrochemical detection biosensor was prepared with the chitosan-immobilized-enzyme (CTS-CAT) and β-cyclodextrin-included-ferrocene (β-CD-FE) complex for the determination of H₂O₂. Ferrocene (FE) was included in β-cyclodextrin (β-CD) to increase its stability. The structure of the β-CD-FE was characterized. The inclusion [...] Read more.

An electrochemical detection biosensor was prepared with the chitosan-immobilized-enzyme (CTS-CAT) and β-cyclodextrin-included-ferrocene (β-CD-FE) complex for the determination of H₂O₂. Ferrocene (FE) was included in β-cyclodextrin (β-CD) to increase its stability. The structure of the β-CD-FE was characterized. The inclusion amount, inclusion rate, and electrochemical properties of inclusion complexes were determined to optimize the reaction conditions for the inclusion. CTS-CAT was prepared by a step-by-step immobilization method, which overcame the disadvantages of the conventional preparation methods. The immobilization conditions were optimized to obtain the desired enzyme activity. CTS-CAT/β-CD-FE composite electrodes were prepared by compositing the CTS-CAT with the β-CD-FE complex on a glassy carbon electrode and used for the electrochemical detection of H₂O₂. It was found that the CTS-CAT could produce a strong reduction peak current in response to H₂O₂ and the β-CD-FE could amplify the current signal. The peak current exhibited a linear relationship with the H₂O₂ concentration in the range of 1.0 × 10⁻⁷–6.0 × 10⁻³ mol/L. Our work provided a novel method for the construction of electrochemical biosensors with a fast response, good stability, high sensitivity, and a wide linear response range based on the composite of chitosan and cyclodextrin. Full article

(This article belongs to the Special Issue Functional Conjugated Polymers for Bioimaging and Biosensing)

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8 pages, 3501 KiB

Open AccessArticle

A Cost-Effective Approach to Optimizing Microstructure and Magnetic Properties in Ce₁₇Fe₇₈B₆ Alloys

by Xiaohua Tan^1,*, Heyun Li¹, Hui Xu¹, Ke Han^2,*, Weidan Li¹ and Fang Zhang³

¹ Institute of Materials, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China

² National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA

³ Tescan China, Shanghai 201112, China

Materials 2017, 10(8), 869; https://doi.org/10.3390/ma10080869 - 28 Jul 2017

Cited by 21 | Viewed by 4175

Abstract

Optimizing fabrication parameters for rapid solidification of Re-Fe-B (Re = Rare earth) alloys can lead to nanocrystalline products with hard magnetic properties without any heat-treatment. In this work, we enhanced the magnetic properties of Ce₁₇Fe₇₈B₆ ribbons by engineering [...] Read more.

Optimizing fabrication parameters for rapid solidification of Re-Fe-B (Re = Rare earth) alloys can lead to nanocrystalline products with hard magnetic properties without any heat-treatment. In this work, we enhanced the magnetic properties of Ce₁₇Fe₇₈B₆ ribbons by engineering both the microstructure and volume fraction of the Ce₂Fe₁₄B phase through optimization of the chamber pressure and the wheel speed necessary for quenching the liquid. We explored the relationship between these two parameters (chamber pressure and wheel speed), and proposed an approach to identifying the experimental conditions most likely to yield homogenous microstructure and reproducible magnetic properties. Optimized experimental conditions resulted in a microstructure with homogeneously dispersed Ce₂Fe₁₄B and CeFe₂ nanocrystals. The best magnetic properties were obtained at a chamber pressure of 0.05 MPa and a wheel speed of 15 m·s⁻¹. Without the conventional heat-treatment that is usually required, key magnetic properties were maximized by optimization processing parameters in rapid solidification of magnetic materials in a cost-effective manner. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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9 pages, 2652 KiB

Open AccessArticle

Superplasticity of Annealed H13 Steel

by Zhenxin Duan, Wen Pei, Xuebo Gong and Hua Chen^*

School of Materials Science and Engineering, Changchun University of Technology, Changchun 130012, China

Materials 2017, 10(8), 870; https://doi.org/10.3390/ma10080870 - 28 Jul 2017

Cited by 14 | Viewed by 4509

Abstract

H13 steel is a widely used hot work die material. A new type of hot working method is imperative to develop complex and precise dies. In this paper, the heat treatment of H13 steel (AISI) was carried out by annealing, the final structure [...] Read more.

H13 steel is a widely used hot work die material. A new type of hot working method is imperative to develop complex and precise dies. In this paper, the heat treatment of H13 steel (AISI) was carried out by annealing, the final structure is a point or spherical pearlite, and the grain size is about 30–40 μm. The tensile properties of the annealed microstructure were investigated at 650, 750, and 850 °C with the strain rates of 1 × 10⁻³ s⁻¹, 5 × 10⁻⁴ s⁻¹, and 1 × 10⁻⁴ s⁻¹. The tensile fracture and microstructure were analyzed by SEM and HREM. The results show that the tensile samples reach superplasticity at the strain rate of 1 × 10⁻⁴ s⁻¹ in the temperature range of 750–850 °C. When the temperature is 850 °C, the maximum elongation rate reaches 112.5%. This demonstrates the possibility of making superplastic forming molds. During the tensile process, the refined M₂₃C₆ and other high hardness carbides which are dispersed uniformly in the matrix, effectively inhibits grain growth and hinders dislocation movement, leading to the improvement of plasticity. Full article

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20 pages, 9890 KiB

Open AccessArticle

Synchrotron Microtomography Reveals the Fine Three-Dimensional Porosity of Composite Polysaccharide Aerogels

by Abdul Ghafar^1,*, Kirsti Parikka¹, David Haberthür²

, Maija Tenkanen¹, Kirsi S. Mikkonen¹

and Jussi-Petteri Suuronen³

¹ Department of Food and Environmental Sciences, P.O. Box 66 (Agnes Sjöbergin katu 2), University of Helsinki, FI-0014 Helsinki, Finland

² X-ray Tomography Group, Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, Switzerland

³ ESRF—The European Synchrotron, CS40220, Grenoble CEDEX 9, 38043 Grenoble, France

Materials 2017, 10(8), 871; https://doi.org/10.3390/ma10080871 - 28 Jul 2017

Cited by 3 | Viewed by 5469

Abstract

This study investigates the impact of ice-templating conditions on the morphological features of composite polysaccharide aerogels in relation to their mechanical behavior and aims to get a better insight into the parameters governing these properties. We have prepared polysaccharide aerogels of guar galactomannan [...] Read more.

This study investigates the impact of ice-templating conditions on the morphological features of composite polysaccharide aerogels in relation to their mechanical behavior and aims to get a better insight into the parameters governing these properties. We have prepared polysaccharide aerogels of guar galactomannan (GM) and tamarind seed xyloglucan (XG) by enzymatic oxidation with galactose oxidase (GaO) to form hydrogels, followed by conventional and unidirectional ice-templating (freezing) methods and lyophilization to form aerogels. Composite polysaccharide aerogels were prepared by incorporating nanofibrillated cellulose (NFC) into polysaccharide solutions prior to enzymatic oxidation and gel formation; such a cross linking technique enabled the homogeneous distribution of the NFC reinforcement into the gel matrix. We conducted phase-enhanced synchrotron X-ray microtomography (XMT) scans and visualized the internal microstructure of the aerogels in three-dimensional (3D) space. Volume-weighted pore-size and pore-wall thickness distributions were quantitatively measured and correlated to the aerogels’ mechanical properties regarding ice-templating conditions. Pore-size distribution and orientation depended on the ice-templating methods and the NFC reinforcement that significantly determined the mechanical and shape-recovery behavior of the aerogels. The results obtained will guide the design of the microporous structure of polysaccharide aerogels with optimal morphology and mechanical behavior for life-sciences applications. Full article

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12 pages, 4534 KiB

Open AccessArticle

Use of Almond Shells and Rice Husk as Fillers of Poly(Methyl Methacrylate) (PMMA) Composites

by Alessandra Sabbatini¹, Silvia Lanari², Carlo Santulli^3,*

and Claudio Pettinari¹

¹ General and Inorganic Chemistry Unit, School of Pharmacy, Università degli Studi di Camerino, via S. Agostino 1, 62032 Camerino (MC), Italy

² Teuco S.p.A., via Virgilio Guzzini 2, 62010 Montelupone (MC), Italy

³ School of Architecture and Design, Università degli Studi di Camerino, viale della Rimembranza, 63100 Ascoli Piceno, Italy

Materials 2017, 10(8), 872; https://doi.org/10.3390/ma10080872 - 28 Jul 2017

Cited by 23 | Viewed by 5542

Abstract

In recent years, wood fibres have often been applied as the reinforcement of thermoplastic materials, such as polypropylene, whereas their use in combination with thermosetting resin has been less widespread. This study concerns the production of PMMA-based composites by partly replacing alumina trihydrate [...] Read more.

In recent years, wood fibres have often been applied as the reinforcement of thermoplastic materials, such as polypropylene, whereas their use in combination with thermosetting resin has been less widespread. This study concerns the production of PMMA-based composites by partly replacing alumina trihydrate (ATH) with wood waste fillers, namely rice husks and almond shells, which would otherwise be disposed by incineration. The amount of filler introduced was limited to 10% as regards rice husks and 10 or 15% almond shells, since indications provided by reactivity tests and viscosity measurements did not suggest the feasibility of total replacement of ATH. As a matter of fact, the introduction of these contents of wood waste filler in PMMA-based composite did not result in any significant deterioration of its mechanical properties (Charpy impact, Rockwell M hardness and flexural performance). Some reduction of these properties was only observed in the case of introduction of 15% almond shells. A further issue concerned the yellowing of the organic filler under exposure to UV light. On the other hand, a very limited amount of water was absorbed, never exceeding values around 0.6%, despite the significant porosity revealed by the filler’s microscopic evaluation. These results are particularly interesting in view of the application envisaged for these composites, i.e., wood replacement boards. Full article

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12 pages, 4555 KiB

Open AccessArticle

Thermal Performance Study of Composite Phase Change Material with Polyacrylicand Conformal Coating

by Shin Yiing Kee¹, Yamuna Munusamy^1,*, Kok Seng Ong¹, Hendrik Simon Cornelis Metselaar²

, Swee Yong Chee³ and Koon Chun Lai¹

¹ Faculty of Engineering and Green Technology, Universiti Tunku Abdul Rahman, Kampar 31900, Malaysia

² Department of Mechanical Engineering and Advanced Material Research Center, University of Malaya, Kuala Lumpur 50603, Malaysia

³ Faculty of Science, Universiti Tunku Abdul Rahman, Kampar 31900, Malaysia

Materials 2017, 10(8), 873; https://doi.org/10.3390/ma10080873 - 28 Jul 2017

Cited by 23 | Viewed by 4936

Abstract

The composite PCM was prepared by blending polymethyl methacrylate (PMMA) and myristic acid (MA) in different weight percentages. The MA and PMMA were selected as PCM and supporting material, respectively. As liquid MA may leak out during the phase transition, this study proposes [...] Read more.

The composite PCM was prepared by blending polymethyl methacrylate (PMMA) and myristic acid (MA) in different weight percentages. The MA and PMMA were selected as PCM and supporting material, respectively. As liquid MA may leak out during the phase transition, this study proposes the use of two coatings, namely a polyacrylic coating and a conformal coating to overcome the leakage problem. Both coatings were studied in terms of the leakage test, chemical compatibility, thermal stability, morphology, and reliability. No leakage was found in the PCMs with coatings compared to those without under the same proportions of MA/PMMA, thus justifying the use of coatings in the present study. The chemically compatibility was confirmed by FTIR spectra: the functional groups of PCMs were in accordance with those of coatings. DSC showed that the coatings did not significantly change the melting and freezing temperatures, however, they improved the thermal stability of composite PCMs as seen in TGA analysis. Furthermore, the composite PCMs demonstrated good thermal reliability after 1000 times thermal cycling. The latent heat of melting reduced by only 0.16% and 1.02% for the PCMs coated with conformal coating and polyacrylic coating, respectively. Therefore, the proposed coatings can be considered in preparing fatty acid/PMMA blends attributed to the good stability, compatibility and leakage prevention. Full article

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10 pages, 32281 KiB

Open AccessArticle

Effect of Austenitising Temperature on Mechanical Properties of Nanostructured Bainitic Steel

by Jing Zhao¹, Jiemin Li¹, Honghong Ji¹ and Tiansheng Wang^1,2,*

¹ State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China

² National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004, China

Materials 2017, 10(8), 874; https://doi.org/10.3390/ma10080874 - 28 Jul 2017

Cited by 13 | Viewed by 4236

Abstract

Nanostructured bainite was obtained in high-carbon Si-Al-rich steel by low-temperature (220–260 °C) isothermal transformation after austenitisation at different temperatures (900 °C, 1000 °C, and 1150 °C). Improved strength-ductility-toughness balance was achieved in the nanostructured bainitic steel austenitised at low temperatures (900 °C and [...] Read more.

Nanostructured bainite was obtained in high-carbon Si-Al-rich steel by low-temperature (220–260 °C) isothermal transformation after austenitisation at different temperatures (900 °C, 1000 °C, and 1150 °C). Improved strength-ductility-toughness balance was achieved in the nanostructured bainitic steel austenitised at low temperatures (900 °C and 1000 °C). Increasing the austenitising temperature not only coarsened prior austenite grains and bainite packets, but also increased the size and fraction of blocky retained austenite. High austenitising temperature (1150 °C) remarkably decreased ductility and impact toughness, but had a small effect on strength and hardness. Full article

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10 pages, 3857 KiB

Open AccessArticle

Effect of Abrasive Machining on the Electrical Properties Cu₈₆Mn₁₂Ni₂ Alloy Shunts

by Siti Nabilah Misti^1,*, Martin Birkett¹

, Roger Penlington¹

and David Bell²

¹ Department of Mechanical and Construction Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, UK

² Vice Chancellors Office, Teesside University, Middlesbrough TS1 3BA, UK

Materials 2017, 10(8), 876; https://doi.org/10.3390/ma10080876 - 29 Jul 2017

Viewed by 4477

Abstract

This paper studies the effect of abrasive trimming on the electrical properties of Cu₈₆Mn₁₂Ni₂ Manganin alloy shunt resistors. A precision abrasive trimming system for fine tuning the resistance tolerance of high current Manganin shunt resistors is proposed. The [...] Read more.

This paper studies the effect of abrasive trimming on the electrical properties of Cu₈₆Mn₁₂Ni₂ Manganin alloy shunt resistors. A precision abrasive trimming system for fine tuning the resistance tolerance of high current Manganin shunt resistors is proposed. The system is shown to be capable of reducing the resistance tolerance of 100 μΩ shunts from their standard value of ±5% to <±1% by removing controlled amounts of Manganin material using a square cut trim geometry. The temperature coefficient of resistance (TCR), high current, and high temperature performance of the trimmed shunts was compared to that of untrimmed parts to determine if trimming had any detrimental effect on these key electrical performance parameters of the device. It was shown that the TCR value was reduced following trimming with typical results of +106 ppm/°C and +93 ppm/°C for untrimmed and trimmed parts respectively. When subjected to a high current of 200 A the trimmed parts showed a slight increase in temperature rise to 203 °C, as compared to 194 °C for the untrimmed parts, but both had significant temporary increases in resistance of up to 1.3 μΩ. The results for resistance change following high temperature storage at 200 °C for 168 h were also significant for both untrimmed and trimmed parts with shifts of 1.85% and 2.29% respectively and these results were related to surface oxidation of the Manganin alloy which was accelerated for the freshly exposed surfaces of the trimmed part. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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20 pages, 5381 KiB

Open AccessArticle

Preparation and Application of Immobilized Surfactant-Modified PANi-CNT/TiO₂ under Visible-Light Irradiation

by Ching Yuan^1,*, Chung-Hsuang Hung², Chung-Shin Yuan³ and Huei-Wen Li⁴

¹ Department of Civil and Environmental Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Rd, Nan-Tzu Dist., Kaohsiung 811, Taiwan

² Department of Safety, Health and Environmental Engineering, National Kaohsiung First University of Science and Technology, No. 1, University Rd., Yenchau Dist., Kaohsiung 824, Taiwan

³ Institute of Environmental Engineering, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804 Taiwan

⁴ Department of Civil and Environmental Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Rd, Nan-Tzu Dist., Kaohsiung 811, Taiwan

Materials 2017, 10(8), 877; https://doi.org/10.3390/ma10080877 - 29 Jul 2017

Cited by 23 | Viewed by 6046

Abstract

Hydrothermally and sol-gel-synthesized immobilized surfactant-modified polyaniline-carbon nanotubes/TiO₂ (PANi-CNT/TiO₂) photocatalysts were prepared and their application in the degradation of diethyl phthalate (DEP) under visible light at 410 nm was investigated in this sturdy. To improve the dispersion of nanoparticles and the [...] Read more.

Hydrothermally and sol-gel-synthesized immobilized surfactant-modified polyaniline-carbon nanotubes/TiO₂ (PANi-CNT/TiO₂) photocatalysts were prepared and their application in the degradation of diethyl phthalate (DEP) under visible light at 410 nm was investigated in this sturdy. To improve the dispersion of nanoparticles and the transfer of electrons, the TiO₂ surface was modified with both sodium dodecyl sulfate (SDS) and functionalized carbon nanotubes (CNT-COOH and CNT-COCl). With the addition of PANi, which was increased from 1%–5%, the adsorption edge of the prepared photocatalysts shifted to 442 nm. The SDS linked the PANi polymers to achieve a thickness of coating of the film of up to 314–400 nm and 1301–1600 nm for sol-gel hydrolysis and hydrothermally-synthesized photocatalysts, respectively. An appropriate film thickness would extend the transfer path of the electrons and inhibit the recombination of the electrons and the electron-holes. The photo-degradation performance of DEP by the hydrothermally-synthesized photocatalysts was better than those by sol-gel hydrolysis. The results revealed that the hydroxyl radicals were the key oxidant in the degradation of DEP using hydrothermally-synthesized PANi-CNT/TiO₂ photocatalysts. The morphology and functional groups of the raw materials of photocatalysts were characterized and a comparison of photocatalytic activity with other TiO₂-based photocatalysts was also provided. Full article

(This article belongs to the Special Issue Enhancing the Photocatalytic Activity of TiO2 Photocatalysts)

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10 pages, 3409 KiB

Open AccessArticle

Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging

by Amar Prasad Gupta^1,2, Sangjun Park¹

, Seung Jun Yeo^1,2, Jaeik Jung², Chonggil Cho², Sang Hyun Paik², Hunkuk Park³, Young Chul Cho⁴, Seung Hoon Kim⁴, Ji Hoon Shin⁴, Jeung Sun Ahn^1,* and Jehwang Ryu^1,2,*

¹ Department of Physics, Kyung Hee University, Seoul 02453, Korea

² CAT Beam Tech Co., Ltd., Seoul Biohub, 117-3, Hoegi-ro, Dongdaemun-gu, Seoul 02455, Korea

³ Department of Biomedical Engineering and Healthcare Industry Research Institute, Kyung Hee University, Seoul 02453, Korea

⁴ Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea

Materials 2017, 10(8), 878; https://doi.org/10.3390/ma10080878 - 29 Jul 2017

Cited by 44 | Viewed by 8851

Abstract

We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 [...] Read more.

We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm² through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a gate field of 7.51 V/μm. The 4.5-inch cubic shape open type X-ray system was developed consisting of an X-ray aperture, a vacuum part, an anode high voltage part, and a field emission electron gun including three electrodes with focusing, gate and cathode electrodes. Using this system, we obtained high-resolution X-ray images accelerated at 42–70 kV voltage by digital switching control between emitter and ground electrode. Full article

(This article belongs to the Special Issue Nanomaterials for Biomedical Applications)

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12 pages, 3766 KiB

Open AccessArticle

Preparation of Cationic MOFs with Mobile Anions by Anion Stripping to Remove 2,4-D from Water

by Tao Chen, Cong Zhang, Yuemei Qin, Haiguan Yang, Peng Zhang and Fanggui Ye^*

State Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, College of Chemistry and Pharmaceutical Science of Guangxi Normal University, Guilin 541004, China

Materials 2017, 10(8), 879; https://doi.org/10.3390/ma10080879 - 30 Jul 2017

Cited by 17 | Viewed by 6535

Abstract

A cationic porous framework with mobile anions (MIL-101(Cr)-Cl) was easily and successfully synthesized by utilizing the stronger affinity of F⁻ to Al³⁺ than Cr³⁺ in the charge-balanced framework of MIL-101(Cr). The structure, morphology and porosity of MIL-101(Cr)-Cl were characterized. The [...] Read more.

A cationic porous framework with mobile anions (MIL-101(Cr)-Cl) was easily and successfully synthesized by utilizing the stronger affinity of F⁻ to Al³⁺ than Cr³⁺ in the charge-balanced framework of MIL-101(Cr). The structure, morphology and porosity of MIL-101(Cr)-Cl were characterized. The obtained new materials retain the high surface area, good thermostability, and structure topology of MIL-101(Cr). With the mobile Cl⁻ anion, MIL-101(Cr)-Cl can be used as an ion-exchange material for anionic organic pollutions. In this work, 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model to test the absorption performance of this new material. This new material exhibited improved adsorbability compared to that of the original metal-organic frameworks (MOFs). At the same time, this material also shows high anti-interference performance with changing solution pH. Full article

(This article belongs to the Special Issue Metal Organic Framework Materials)

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11 pages, 3212 KiB

Open AccessFeature PaperArticle

Low-Concentration Indium Doping in Solution-Processed Zinc Oxide Films for Thin-Film Transistors

by Xue Zhang^1,†, Hyeonju Lee^1,†, Jung-Hyok Kwon²

, Eui-Jik Kim²

and Jaehoon Park^1,*

¹ Department of Electronic Engineering, Hallym University, Chuncheon 24252, Korea

² Department of Convergence Software, Hallym University, Chuncheon 24252, Korea

^† These authors contributed equally to this work.

Materials 2017, 10(8), 880; https://doi.org/10.3390/ma10080880 - 31 Jul 2017

Cited by 38 | Viewed by 7259

Abstract

We investigated the influence of low-concentration indium (In) doping on the chemical and structural properties of solution-processed zinc oxide (ZnO) films and the electrical characteristics of bottom-gate/top-contact In-doped ZnO thin-film transistors (TFTs). The thermogravimetry and differential scanning calorimetry analysis results showed that thermal [...] Read more.

We investigated the influence of low-concentration indium (In) doping on the chemical and structural properties of solution-processed zinc oxide (ZnO) films and the electrical characteristics of bottom-gate/top-contact In-doped ZnO thin-film transistors (TFTs). The thermogravimetry and differential scanning calorimetry analysis results showed that thermal annealing at 400 °C for 40 min produces In-doped ZnO films. As the In content of ZnO films was increased from 1% to 9%, the metal-oxygen bonding increased from 5.56% to 71.33%, while the metal-hydroxyl bonding decreased from 72.03% to 9.63%. The X-ray diffraction peaks and field-emission scanning microscope images of the ZnO films with different In concentrations revealed a better crystalline quality and reduced grain size of the solution-processed ZnO thin films. The thickness of the In-doped ZnO films also increased when the In content was increased up to 5%; however, the thickness decreased on further increasing the In content. The field-effect mobility and on/off current ratio of In-doped ZnO TFTs were notably affected by any change in the In concentration. Considering the overall TFT performance, the optimal In doping concentration in the solution-processed ZnO semiconductor was determined to be 5% in this study. These results suggest that low-concentration In incorporation is crucial for modulating the morphological characteristics of solution-processed ZnO thin films and the TFT performance. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)

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13 pages, 3516 KiB

Open AccessFeature PaperArticle

Investigations for Thermal and Electrical Conductivity of ABS-Graphene Blended Prototypes

by Rupinder Singh^1,*

, Gurleen S. Sandhu¹, Rosa Penna² and Ilenia Farina³

¹ Department of Production Engineering, Guru Nanak Dev Engineering College, Ludhiana 141006, India

² Department of Engineering, University of Salerno, 84084 Fisciano, Italy

³ Department of Engineering, University of Naples Parthenope, 80143 Naples, Italy

Materials 2017, 10(8), 881; https://doi.org/10.3390/ma10080881 - 31 Jul 2017

Cited by 79 | Viewed by 7452

Abstract

The thermoplastic materials such as acrylonitrile-butadiene-styrene (ABS) and Nylon have large applications in three-dimensional printing of functional/non-functional prototypes. Usually these polymer-based prototypes are lacking in thermal and electrical conductivity. Graphene (Gr) has attracted impressive enthusiasm in the recent past due to its natural [...] Read more.

The thermoplastic materials such as acrylonitrile-butadiene-styrene (ABS) and Nylon have large applications in three-dimensional printing of functional/non-functional prototypes. Usually these polymer-based prototypes are lacking in thermal and electrical conductivity. Graphene (Gr) has attracted impressive enthusiasm in the recent past due to its natural mechanical, thermal, and electrical properties. This paper presents the step by step procedure (as a case study) for development of an in-house ABS-Gr blended composite feedstock filament for fused deposition modelling (FDM) applications. The feedstock filament has been prepared by two different methods (mechanical and chemical mixing). For mechanical mixing, a twin screw extrusion (TSE) process has been used, and for chemical mixing, the composite of Gr in an ABS matrix has been set by chemical dissolution, followed by mechanical blending through TSE. Finally, the electrical and thermal conductivity of functional prototypes prepared from composite feedstock filaments have been optimized. Full article

(This article belongs to the Special Issue Recycled Materials, Eco-design and 3D Printing)

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17 pages, 5248 KiB

Open AccessArticle

Impact Load Behavior between Different Charge and Lifter in a Laboratory-Scale Mill

by Zixin Yin^1,2, Yuxing Peng^1,2,*

, Zhencai Zhu^1,2, Zhangfa Yu^3,4 and Tongqing Li^1,2

¹ School of Mechatronic Engineering, China University of Mining & Technology, Xuzhou, 221116 China

² Jiangsu Key Laboratory of Mine Mechanical and Electrical Equipment, China University of Mining & Technology, Xuzhou 221116, China

³ Luoyang Mining Machinery Engineering Design Institute Co., Ltd., Luoyang 471039, China

⁴ State Key Laboratory of Mining Heavy Equipment, CITIC Heavy Industries Co., Ltd., Luoyang 471039, China

Materials 2017, 10(8), 882; https://doi.org/10.3390/ma10080882 - 31 Jul 2017

Cited by 23 | Viewed by 6878

Abstract

The impact behavior between the charge and lifter has significant effect to address the mill processing, and is affected by various factors including mill speed, mill filling, lifter height and media shape. To investigate the multi-body impact load behavior, a series of experiments [...] Read more.

The impact behavior between the charge and lifter has significant effect to address the mill processing, and is affected by various factors including mill speed, mill filling, lifter height and media shape. To investigate the multi-body impact load behavior, a series of experiments and Discrete Element Method (DEM) simulations were performed on a laboratory-scale mill, in order to improve the grinding efficiency and prolong the life of the lifter. DEM simulation hitherto has been extensively applied as a leading tool to describe diverse issues in granular processes. The research results shown as follows: The semi-empirical power draw of Bond model in this paper does not apply very satisfactorily for the ball mills, while the power draw determined by DEM simulation show a good approximation for the measured power draw. Besides, the impact force on the lifter was affected by mill speed, grinding media filling, lifter height and iron ore particle. The maximum percent of the impact force between 600 and 1400 N is at 70–80% of critical speed. The impact force can be only above 1400 N at the grinding media filling of 20%, and the maximum percent of impact force between 200 and 1400 N is obtained at the grinding media filling of 20%. The percent of impact force ranging from 0 to 200 N decreases with the increase of lifter height. However, this perfect will increase above 200 N. The impact force will decrease when the iron ore particles are added. Additionally, for the 80% of critical speed, the measured power draw has a maximum value. Increasing the grinding media filling increases the power draw and increasing the lifter height does not lead to any variation in power draw. Full article

(This article belongs to the Special Issue Granular Materials)

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12 pages, 13758 KiB

Open AccessArticle

Microstructure, Tensile and Creep Properties of Ta₂₀Nb₂₀Hf₂₀Zr₂₀Ti₂₀ High Entropy Alloy

by Natalya Larianovsky¹, Alexander Katz-Demyanetz¹, Eyal Eshed¹ and Michael Regev^2,*

¹ Israel Institute of Metals, Foundry Laboratory, Technion-Israel Institute of Technology, Haifa 3200003, Israel

² Mechanical Engineering Department, ORT Braude College of Engineering, Karmiel 2161002, Israel

Materials 2017, 10(8), 883; https://doi.org/10.3390/ma10080883 - 31 Jul 2017

Cited by 21 | Viewed by 5719

Abstract

This paper examines the microstructure and mechanical properties of Ta₂₀Nb₂₀Hf₂₀Zr₂₀Ti₂₀. Two casting processes, namely, gravity casting and suction-assisted casting, were applied, both followed by Hot Isostatic Pressing (HIP). The aim of the current [...] Read more.

This paper examines the microstructure and mechanical properties of Ta₂₀Nb₂₀Hf₂₀Zr₂₀Ti₂₀. Two casting processes, namely, gravity casting and suction-assisted casting, were applied, both followed by Hot Isostatic Pressing (HIP). The aim of the current study was to investigate the creep and tensile properties of the material, since the literature review revealed no data whatsoever regarding these properties. The main findings are that the HIP process is responsible for the appearance of a Hexagonal Close Packed (HCP) phase that is dispersed differently in these two castings. The HIP process also led to a considerable increase in the mechanical properties of both materials under compression, with values found to be higher than those reported in the literature. Contrary to the compression properties, both materials were found to be highly brittle under tension, either during room temperature tension tests or creep tests conducted at 282 °C. Fractography yielded brittle fracture without any evidence of plastic deformation prior to fracture. Full article

(This article belongs to the Special Issue High Entropy Alloys)

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10 pages, 1551 KiB

Open AccessArticle

Mie-Metamaterials-Based Thermal Emitter for Near-Field Thermophotovoltaic Systems

by Alok Ghanekar¹, Yanpei Tian¹, Sinong Zhang², Yali Cui^2,3 and Yi Zheng^1,*

¹ Department of Mechanical, Industrial and Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA

² College of Life Sciences, Northwest University, Xi’an 710069, China

³ National Engineering Research Center for Miniaturized Detection Systems, Northwest University, Xi’an 710069, China

Materials 2017, 10(8), 885; https://doi.org/10.3390/ma10080885 - 31 Jul 2017

Cited by 25 | Viewed by 5797

Abstract

In this work, we theoretically analyze the performance characteristics of a near-field thermophotovoltaic system consisting a Mie-metamaterial emitter and GaSb-based photovoltaic cell at separations less than the thermal wavelength. The emitter consists of a tungsten nanoparticle-embedded thin film of SiO

_{2}

deposited on [...] Read more.

In this work, we theoretically analyze the performance characteristics of a near-field thermophotovoltaic system consisting a Mie-metamaterial emitter and GaSb-based photovoltaic cell at separations less than the thermal wavelength. The emitter consists of a tungsten nanoparticle-embedded thin film of SiO

_{2}

deposited on bulk tungsten. Numerical results presented here are obtained using formulae derived from dyadic Green’s function formalism and Maxwell–Garnett-Mie theory. We show that via the inclusion of tungsten nanoparticles, the thin layer of SiO

_{2}

acts like an effective medium that enhances selective radiative heat transfer for the photons above the band gap of GaSb. We analyze thermophotovoltaic (TPV) performance for various volume fractions of tungsten nanoparticles and thicknesses of SiO

_{2}

. Full article

(This article belongs to the Special Issue Advance in Plasmonics and Metamaterials)

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8 pages, 951 KiB

Open AccessArticle

Microwave-Assisted Pillaring of a Montmorillonite with Al-Polycations in Concentrated Media

by Beatriz González¹, Alba Helena Pérez¹, Raquel Trujillano¹, Antonio Gil²

and Miguel A. Vicente^1,*

¹ Departamento de Química Inorgánica, Universidad de Salamanca, 37008 Salamanca, Spain

² Departamento de Química Aplicada, Universidad Pública de Navarra, 31006 Pamplona, Spain

Materials 2017, 10(8), 886; https://doi.org/10.3390/ma10080886 - 1 Aug 2017

Cited by 18 | Viewed by 4108

Abstract

A montmorillonite has been intercalated with Al³⁺ polycations, using concentrated solutions and clay mineral dispersions. The reaction has been assisted by microwave radiation, yielding new intercalated solids and leading to Al-pillared solids after their calcination at 500 °C. The solids were characterized [...] Read more.

A montmorillonite has been intercalated with Al³⁺ polycations, using concentrated solutions and clay mineral dispersions. The reaction has been assisted by microwave radiation, yielding new intercalated solids and leading to Al-pillared solids after their calcination at 500 °C. The solids were characterized by elemental chemical analysis, X-ray diffraction, FTIR spectroscopy, thermal analyses, and nitrogen adsorption. The evolution of the properties of the materials was discussed as a function of the preparation conditions. Microwave treatment for 2.5 min provided correctly pillared solids. Full article

(This article belongs to the Special Issue Advances in Pillared Clays and Similar Materials: Synthesis, Characterization and Applications)

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14 pages, 4667 KiB

Open AccessArticle

Experimental Investigation on the Joining of Aluminum Alloy Sheets Using Improved Clinching Process

by Chao Chen^1,2,*, Shengdun Zhao^1,*

, Xiaolan Han³, Xuzhe Zhao⁴ and Tohru Ishida²

¹ School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China

² Graduate School of Technology, Industrial and Social Sciences, Tokushima University, Tokushima 770-8506, Japan

³ Mechanical Engineering College, Xi’an Shiyou University, Xi’an 710049, China

⁴ School of Engineering Technology, Purdue University, West Lafayette, IN 47906, USA

Materials 2017, 10(8), 887; https://doi.org/10.3390/ma10080887 - 1 Aug 2017

Cited by 50 | Viewed by 8025

Abstract

Aluminum alloy sheets have been widely used to build the thin-walled structures by mechanical clinching technology in recent years. However, there is an exterior protrusion located on the lower sheet and a pit on the upper sheet, which may restrict the application of [...] Read more.

Aluminum alloy sheets have been widely used to build the thin-walled structures by mechanical clinching technology in recent years. However, there is an exterior protrusion located on the lower sheet and a pit on the upper sheet, which may restrict the application of the clinching technology in visible areas. In the present study, an improved clinched joint used to join aluminum alloy sheets was investigated by experimental method. The improved clinching process used for joining aluminum alloy evolves through four phases: (a) localized deformation; (b) drawing; (c) backward extrusion; and (d) mechanical interlock forming. A flat surface can be produced using the improved clinching process. Shearing strength, tensile strength, material flow, main geometrical parameters, and failure mode of the improved clinched joint were investigated. The sheet material was compressed to flow radially and upward using a punch, which generated a mechanical interlock by producing severe localized plastic deformation. The neck thickness and interlock of the improved clinched joint were increased by increasing the forming force, which also contributed to increase the strength of the clinched joint. The improved clinched joint can get high shearing strength and tensile strength. Three main failure modes were observed in the failure process, which were neck fracture mode, button separation mode, and mixed failure mode. The improved clinched joint has better joining quality to join aluminum alloy sheets on the thin-walled structures. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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16 pages, 4108 KiB

Open AccessArticle

Outdoor Performance Analysis of a Photovoltaic Thermal (PVT) Collector with Jet Impingement and Compound Parabolic Concentrator (CPC)

by Ahed Hameed Jaaz^1,*, Husam Abdulrasool Hasan¹, Kamaruzzaman Sopian^1,*, Abdul Amir H. Kadhum², Tayser Sumer Gaaz^3,4 and Ahmed A. Al-Amiery⁵

¹ Solar Energy Research Institute, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia

² Department of Chemical & Process Engineering, Faculty of Engineering & Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia

³ Department of Mechanical & Materials Engineering, Faculty of Engineering & Built Environment, University Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia

⁴ Department of Machinery Equipment Engineering Techniques, Technical College Al-Musaib, Al-Furat Al-Awsat Technical University, Al-Musaib, Babil 51009, Iraq

⁵ Energy and Renewable Energies Technology Centre, University of Technology, Baghdad 10001, Iraq

Materials 2017, 10(8), 888; https://doi.org/10.3390/ma10080888 - 1 Aug 2017

Cited by 38 | Viewed by 8733

Abstract

This paper discusses the effect of jet impingement of water on a photovoltaic thermal (PVT) collector and compound parabolic concentrators (CPC) on electrical efficiency, thermal efficiency and power production of a PVT system. A prototype of a PVT solar water collector installed with [...] Read more.

This paper discusses the effect of jet impingement of water on a photovoltaic thermal (PVT) collector and compound parabolic concentrators (CPC) on electrical efficiency, thermal efficiency and power production of a PVT system. A prototype of a PVT solar water collector installed with a jet impingement and CPC has been designed, fabricated and experimentally investigated. The efficiency of the system can be improved by using jet impingement of water to decrease the temperature of the solar cells. The electrical efficiency and power output are directly correlated with the mass flow rate. The results show that electrical efficiency was improved by 7% when using CPC and jet impingement cooling in a PVT solar collector at 1:00 p.m. (solar irradiance of 1050 W/m² and an ambient temperature of 33.5 °C). It can also be seen that the power output improved by 36% when using jet impingement cooling with CPC, and 20% without CPC in the photovoltaic (PV) module at 1:30 p.m. The short-circuit current I_SC of the PV module experienced an improvement of ~28% when using jet impingement cooling with CPC, and 11.7% without CPC. The output of the PV module was enhanced by 31% when using jet impingement cooling with CPC, and 16% without CPC. Full article

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10 pages, 1120 KiB

Open AccessCommunication

Micro-Mechanical Viscoelastic Properties of Crosslinked Hydrogels Using the Nano-Epsilon Dot Method

by Giorgio Mattei^1,2,3

, Ludovica Cacopardo^1,4 and Arti Ahluwalia^1,4,*

¹ Research Centre E. Piaggio, University of Pisa, Largo Lucio Lazzarino 1, 56122 Pisa, Italy

² Optics11 B.V., De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands

³ Biophotonics & Medical Imaging and LaserLaB, VU University Amsterdam, De Boelelaan 1105, 1081 HV Amsterdam, The Netherlands

⁴ Department of Information Engineering, University of Pisa, Via Girolamo Caruso 16, 56122 Pisa, Italy

Materials 2017, 10(8), 889; https://doi.org/10.3390/ma10080889 - 2 Aug 2017

Cited by 31 | Viewed by 5632

Abstract

Engineering materials that recapitulate pathophysiological mechanical properties of native tissues in vitro is of interest for the development of biomimetic organ models. To date, the majority of studies have focused on designing hydrogels for cell cultures which mimic native tissue stiffness or quasi-static [...] Read more.

Engineering materials that recapitulate pathophysiological mechanical properties of native tissues in vitro is of interest for the development of biomimetic organ models. To date, the majority of studies have focused on designing hydrogels for cell cultures which mimic native tissue stiffness or quasi-static elastic moduli through a variety of crosslinking strategies, while their viscoelastic (time-dependent) behavior has been largely ignored. To provide a more complete description of the biomechanical environment felt by cells, we focused on characterizing the micro-mechanical viscoelastic properties of crosslinked hydrogels at typical cell length scales. In particular, gelatin hydrogels crosslinked with different glutaraldehyde (GTA) concentrations were analyzed via nano-indentation tests using the nano-epsilon dot method. The experimental data were fitted to a Maxwell Standard Linear Solid model, showing that increasing GTA concentration results in increased instantaneous and equilibrium elastic moduli and in a higher characteristic relaxation time. Therefore, not only do gelatin hydrogels become stiffer with increasing crosslinker concentration (as reported in the literature), but there is also a concomitant change in their viscoelastic behavior towards a more elastic one. As the degree of crosslinking alters both the elastic and viscous behavior of hydrogels, caution should be taken when attributing cell response merely to substrate stiffness, as the two effects cannot be decoupled. Full article

(This article belongs to the Special Issue Advanced Nanoindentation in Materials)

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16 pages, 1963 KiB

Open AccessArticle

Influence of Silica Fume Addition in the Long-Term Performance of Sustainable Cement Grouts for Micropiles Exposed to a Sulphate Aggressive Medium

by José Marcos Ortega^1,2,*

, María Dolores Esteban², Raúl Rubén Rodríguez², José Luis Pastor¹

, Francisco José Ibanco¹, Isidro Sánchez¹

and Miguel Ángel Climent¹

¹ Departamento de Ingeniería Civil, Universidad de Alicante, Ap. Correos 99, 03080 Alacant/Alicante, Spain

² Departamento de Ingeniería Civil, Urbanismo y Aeroespacial, Escuela de Arquitectura, Ingeniería y Diseño, Universidad Europea, c/Tajo s/n, Villaviciosa de Odón, 28670 Madrid, Spain

Materials 2017, 10(8), 890; https://doi.org/10.3390/ma10080890 - 2 Aug 2017

Cited by 18 | Viewed by 5423

Abstract

At present, sustainability is of major importance in the cement industry, and the use of additions such as silica fume as clinker replacement contributes towards that goal. Special foundations, and particularly micropiles, are one of the most suitable areas for the use of [...] Read more.

At present, sustainability is of major importance in the cement industry, and the use of additions such as silica fume as clinker replacement contributes towards that goal. Special foundations, and particularly micropiles, are one of the most suitable areas for the use of sustainable cements. The aim of this research is to analyse the effects in the very long-term (for 600 days) produced by sulphate attack in the microstructure of grouts for micropiles in which OPC (ordinary Portland cement) has been replaced by 5% and 10% silica fume. This line of study is building on a previous work, where these effects were studied in slag and fly ash grouts. Grouts made using a commercial sulphate-resisting Portland cement were also studied. The non-destructive impedance spectroscopy technique, mercury intrusion porosimetry, and Wenner resistivity testing were used. Mass variation and the compressive strength have also been analysed. Apparently, impedance spectroscopy is the most suitable technique for studying sulphate attack development. According to the results obtained, grouts for micropiles with a content of silica fume up to 10% and exposed to an aggressive sulphate medium, have a similar or even better behaviour in the very long-term, compared to grouts prepared using sulphate-resisting Portland cement. Full article

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15 pages, 3717 KiB

Open AccessArticle

Synthesis of Bi₂S₃/BiVO₄ Heterojunction with a One-Step Hydrothermal Method Based on pH Control and the Evaluation of Visible-Light Photocatalytic Performance

by Deqiang Zhao^1,2, Wenwen Wang³, Wenjuan Zong^1,2, Shimin Xiong^1,2, Qian Zhang^1,2, Fangying Ji^1,2,* and Xuan Xu^1,2,*

¹ Key Laboratory of Three Gorges Reservoir Region’s Eco-Environment Ministry of Education and National Centre for International Research of Low-Carbon and Green Buildings, Chongqing University, No. 174 Shazhengjie, Shapingba, Chongqing 400045, China

² National Centre for International Research of Low-Carbon and Green Buildings, Chongqing University, Chongqing 400045, China

³ Faculty of Urban Construction and Environment Engineering, Chongqing 400045, China

Materials 2017, 10(8), 891; https://doi.org/10.3390/ma10080891 - 2 Aug 2017

Cited by 39 | Viewed by 8824

Abstract

The band gaps of bismuth vanadate (BiVO₄) and bismuth sulfide (Bi₂S₃) are about 2.40 eV and 1.30 eV, respectively. Although both BiVO₄ and Bi₂S₃ are capable of strong visible light absorption, electron–hole recombination [...] Read more.

The band gaps of bismuth vanadate (BiVO₄) and bismuth sulfide (Bi₂S₃) are about 2.40 eV and 1.30 eV, respectively. Although both BiVO₄ and Bi₂S₃ are capable of strong visible light absorption, electron–hole recombination occurs easily. To solve this problem, we designed a one-step hydrothermal method for synthesizing a Bismuth sulfide (Bi₂S₃)/Bismuth vanadate (BiVO₄) heterojunction using polyvinylpyrrolidone K-30 (PVP) as a structure-directing agent, and 2-Amino-3-mercaptopropanoic acid (l-cysteine) as a sulfur source. The pH of the reaction solution was regulated to yield different products: when the pH was 7.5, only monoclinic BiVO₄ was produced (sample 7.5); when the pH was 8.0 or 8.5, both Bi₂S₃ and BiVO₄ were produced (samples 8.0 and 8.5); and when the pH was 9.0, only Bi₂S₃ was produced (sample 9.0). In sample 8.0, Bi₂S₃ and BiVO₄ were closely integrated with each other, with Bi₂S₃ particles formed on the surface of concentric BiVO₄ layers, but the two compounds grew separately in a pH solution of 8.5. Visible-light photocatalytic degradation experiments demonstrated that the degradation efficiency of the Bi₂S₃/BiVO₄ heterojunction was highest when prepared under a pH of 8.0. The initial rhodamine B in the solution (5 mg/L) was completely degraded within three hours. Recycling experiments verified the high stability of Bi₂S₃/BiVO₄. The synthesis method proposed in this paper is expected to enable large-scale and practical use of Bi₂S₃/BiVO₄. Full article

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16 pages, 3098 KiB

Open AccessArticle

Mechanical Contact Characteristics of PC3 Human Prostate Cancer Cells on Complex-Shaped Silicon Micropillars

by Brandon B. Seo¹, Zeinab Jahed², Jennifer A. Coggan³, Yeung Yeung Chau⁴, Jacob L. Rogowski¹, Frank X. Gu¹, Weijia Wen⁴, Mohammad R. K. Mofrad²

and Ting Yiu Tsui^1,*

¹ Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada

² Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, 208A Stanley Hall, Berkeley, CA 94720, USA

³ Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada

⁴ Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

Materials 2017, 10(8), 892; https://doi.org/10.3390/ma10080892 - 2 Aug 2017

Cited by 6 | Viewed by 6470

Abstract

In this study we investigated the contact characteristics of human prostate cancer cells (PC3) on silicon micropillar arrays with complex shapes by using high-resolution confocal fluorescence microscopy techniques. These arrays consist of micropillars that are of various cross-sectional geometries which produce different deformation [...] Read more.

In this study we investigated the contact characteristics of human prostate cancer cells (PC3) on silicon micropillar arrays with complex shapes by using high-resolution confocal fluorescence microscopy techniques. These arrays consist of micropillars that are of various cross-sectional geometries which produce different deformation profiles in adherent cells. Fluorescence micrographs reveal that some DAPI (4′,6-diamidino-2-phenylindole)-stained nuclei from cells attached to the pillars develop nanometer scale slits and contain low concentrations of DNA. The lengths of these slits, and their frequency of occurrence, were characterized for various cross-sectional geometries. These DNA-depleted features are only observed in locations below the pillar’s top surfaces. Results produced in this study indicate that surface topography can induce unique nanometer scale features in the PC3 cell. Full article

(This article belongs to the Special Issue Advanced Nanoindentation in Materials)

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25 pages, 9336 KiB

Open AccessArticle

Adsorption of Milk Proteins (β-Casein and β-Lactoglobulin) and BSA onto Hydrophobic Surfaces

by Leonor Pérez-Fuentes¹

, Carlos Drummond^2,3, Jordi Faraudo^4,*

and Delfi Bastos-González¹

¹ Biocolloid and Fluid Physics Group, Department of Applied Physics, University of Granada, Av. Fuentenueva 2, E-18001 Granada, Spain

² CNRS, Centre de Recherche Paul Pascal (CRPP), UPR 8641, F3300 Pessac, France

³ Université de Bordeaux, CRPP, UPR 8641, F-33600 Pessac, France

⁴ Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, E-08193 Bellaterra, Barcelona, Spain

Materials 2017, 10(8), 893; https://doi.org/10.3390/ma10080893 - 2 Aug 2017

Cited by 51 | Viewed by 11189

Abstract

Here, we study films of proteins over planar surfaces and protein-coated microspheres obtained from the adsorption of three different proteins (

β

-casein,

β

-lactoglobulin and bovine serum albumin (BSA)). The investigation of protein films in planar surfaces is performed by combining quartz [...] Read more.

Here, we study films of proteins over planar surfaces and protein-coated microspheres obtained from the adsorption of three different proteins (

β

-casein,

β

-lactoglobulin and bovine serum albumin (BSA)). The investigation of protein films in planar surfaces is performed by combining quartz crystal microbalance (QCM) and atomic force microscopy (AFM) measurements with all-atomic molecular dynamics (MD) simulations. We found that BSA and

β

-lactoglobulin form compact monolayers, almost without interstices between the proteins. However,

β

-casein adsorbs forming multilayers. The study of the electrokinetic mobility of protein-coated latex microspheres shows substantial condensation of ions from the buffer over the complexes, as predicted from ion condensation theories. The electrokinetic behavior of the latex-protein complexes is dominated by the charge of the proteins and the phenomenon of ion condensation, whereas the charge of the latex colloids plays only a minor role. Full article

(This article belongs to the Section Advanced Materials Characterization)

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11 pages, 5046 KiB

Open AccessArticle

Sc-Decorated Porous Graphene for High-Capacity Hydrogen Storage: First-Principles Calculations

by Yuhong Chen^1,2,*, Jing Wang^1,2, Lihua Yuan², Meiling Zhang² and Cairong Zhang^1,2

¹ State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China

² School of Science, Lanzhou University of Technology, Lanzhou 730050, China

Materials 2017, 10(8), 894; https://doi.org/10.3390/ma10080894 - 2 Aug 2017

Cited by 38 | Viewed by 4794

Abstract

The generalized gradient approximation (GGA) function based on density functional theory is adopted to investigate the optimized geometrical structure, electron structure and hydrogen storage performance of Sc modified porous graphene (PG). It is found that the carbon ring center is the most stable [...] Read more.

The generalized gradient approximation (GGA) function based on density functional theory is adopted to investigate the optimized geometrical structure, electron structure and hydrogen storage performance of Sc modified porous graphene (PG). It is found that the carbon ring center is the most stable adsorbed position for a single Sc atom on PG, and the maximum number of adsorbed H₂ molecules is four with the average adsorption energy of −0.429 eV/H₂. By adding a second Sc atom on the other side of the system, the hydrogen storage capacity of the system can be improved effectively. Two Sc atoms located on opposite sides of the PG carbon ring center hole is the most suitable hydrogen storage structure, and the hydrogen storage capacity reach a maximum 9.09 wt % at the average adsorption energy of −0.296 eV/H₂. The adsorption of H₂ molecules in the PG system is mainly attributed to orbital hybridization among H, Sc, and C atoms, and Coulomb attraction between negatively charged H₂ molecules and positively charged Sc atoms. Full article

(This article belongs to the Section Energy Materials)

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26 pages, 9913 KiB

Open AccessArticle

Seismic and Restoration Assessment of Monumental Masonry Structures

by Panagiotis G. Asteris^1,*

, Maria G. Douvika¹, Maria Apostolopoulou² and Antonia Moropoulou²

¹ Computational Mechanics Laboratory, School of Pedagogical and Technological Education, Heraklion, 14121 Athens, Greece

² Laboratory of Materials Science and Engineering, School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece

Materials 2017, 10(8), 895; https://doi.org/10.3390/ma10080895 - 2 Aug 2017

Cited by 21 | Viewed by 6218

Abstract

Masonry structures are complex systems that require detailed knowledge and information regarding their response under seismic excitations. Appropriate modelling of a masonry structure is a prerequisite for a reliable earthquake-resistant design and/or assessment. However, modelling a real structure with a robust quantitative (mathematical) [...] Read more.

Masonry structures are complex systems that require detailed knowledge and information regarding their response under seismic excitations. Appropriate modelling of a masonry structure is a prerequisite for a reliable earthquake-resistant design and/or assessment. However, modelling a real structure with a robust quantitative (mathematical) representation is a very difficult, complex and computationally-demanding task. The paper herein presents a new stochastic computational framework for earthquake-resistant design of masonry structural systems. The proposed framework is based on the probabilistic behavior of crucial parameters, such as material strength and seismic characteristics, and utilizes fragility analysis based on different failure criteria for the masonry material. The application of the proposed methodology is illustrated in the case of a historical and monumental masonry structure, namely the assessment of the seismic vulnerability of the Kaisariani Monastery, a byzantine church that was built in Athens, Greece, at the end of the 11th to the beginning of the 12th century. Useful conclusions are drawn regarding the effectiveness of the intervention techniques used for the reduction of the vulnerability of the case-study structure, by means of comparison of the results obtained. Full article

(This article belongs to the Special Issue Modeling and Simulation of Advanced Composite Materials)

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22 pages, 4110 KiB

Open AccessArticle

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling

by Jan Eike Schnabel^1,*

and Swantje Bargmann²

¹ Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Max-Planck-str. 1, 21502 Geesthacht, Germany

² Chair of Solid Mechanics, University of Wuppertal, Gaussstr. 20, 42119 Wuppertal, Germany

Materials 2017, 10(8), 896; https://doi.org/10.3390/ma10080896 - 3 Aug 2017

Cited by 16 | Viewed by 7367

Abstract

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments [...] Read more.

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall–Petch coefficient

K_{C}

experimentally requires a sufficient number of specimens with different colony sizes

λ_{C}

but constant lamella thickness

λ_{L}

and domain size

λ_{D}

, difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient

K_{C}

as a function of lamella thickness

λ_{L}

. The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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10 pages, 1862 KiB

Open AccessArticle

Luminescent Properties of Zn and Mg Complexes on N-(2-Carboxyphenyl)salicylidenimine Basis

by Alexey Gusev¹, Elena Braga¹, Victor Shul’gin¹, Konstantin Lyssenko², Igor Eremenko³

, Lybov Samsonova⁴, Konstantin Degtyarenko⁴, Tatiana Kopylova⁴ and Wolfgang Linert^5,*

¹ General and Physical Chemistry Department, Crimean Federal University, Simferopol 295007, Russia

² A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia

³ N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow 119991, Russia

⁴ Laboratory of Organic Electronics, Tomsk State University, Tomsk 634050, Russia

⁵ Institute of Applied Synthetic Chemistry, Vienna University of Technology, A-1060 Vienna, Austria

Materials 2017, 10(8), 897; https://doi.org/10.3390/ma10080897 - 3 Aug 2017

Cited by 21 | Viewed by 4269

Abstract

New zinc and magnesium complexes of N-(2-carboxyphenyl)salicylidenimine) were synthesized and structurally characterized by elemental analysis, FT-IR, and X-ray single-crystal analysis. These complexes exhibit tuneable luminescence in the solid state from blue to green by varying by metal ion and composition. Moreover, the quantum [...] Read more.

New zinc and magnesium complexes of N-(2-carboxyphenyl)salicylidenimine) were synthesized and structurally characterized by elemental analysis, FT-IR, and X-ray single-crystal analysis. These complexes exhibit tuneable luminescence in the solid state from blue to green by varying by metal ion and composition. Moreover, the quantum yields range from 0.11 to 0.41, while lifetimes were determined to be in the nanosecond timescale. Thermal analysis shows that these complexes exhibit good thermal stability and can therefore well be used as electroluminescent materials. Full article

(This article belongs to the Section Advanced Materials Characterization)

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18 pages, 8447 KiB

Open AccessArticle

The Quantified Characterization Method of the Micro-Macro Contacts of Three-Dimensional Granular Materials on the Basis of Graph Theory

by Yanpeng Guan^1,2

, Enzhi Wang^1,2, Xiaoli Liu^1,2,*, Sijing Wang^1,2 and Hebing Luan^1,2

¹ The State Key Laboratory of Hydro-Science and Engineering, Tsinghua University, Beijing 100084, China

² Sanjiangyuan Collaborative Innovation Center, Tsinghua University, Beijing 100084, China

Materials 2017, 10(8), 898; https://doi.org/10.3390/ma10080898 - 3 Aug 2017

Cited by 7 | Viewed by 4324

Abstract

We have attempted a multiscale and quantified characterization method of the contact in three-dimensional granular material made of spherical particles, particularly in cemented granular material. Particle contact is defined as a type of surface contact with voids in its surroundings, rather than a [...] Read more.

We have attempted a multiscale and quantified characterization method of the contact in three-dimensional granular material made of spherical particles, particularly in cemented granular material. Particle contact is defined as a type of surface contact with voids in its surroundings, rather than a point contact. Macro contact is a particle contact set satisfying the restrictive condition of a two-dimensional manifold with a boundary. On the basis of graph theory, two dual geometrical systems are abstracted from the granular pack. The face and the face set, which satisfies the two-dimensional manifold with a boundary in the solid cell system, are extracted to characterize the particle contact and the macro contact, respectively. This characterization method is utilized to improve the post-processing in DEM (Discrete Element Method) from a micro perspective to describe the macro effect of the cemented granular material made of spherical particles. Since the crack has the same shape as its corresponding contact, this method is adopted to characterize the crack and realize its visualization. The integral failure route of the sample can be determined by a graph theory algorithm. The contact force is assigned to the weight value of the face characterizing the particle contact. Since the force vectors can be added, the macro contact force can be solved by adding the weight of its corresponding faces. Full article

(This article belongs to the Special Issue Granular Materials)

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10 pages, 2168 KiB

Open AccessArticle

Characterization of OT4-1 Alloy by Multi-Dome Forming Test

by Ivan Zakhariev^1,*

, Sergey Aksenov¹, Anton Kotov¹ and Aleksey Kolesnikov²

¹ National Research University Higher School of Economics, Moscow 101000, Russia

² Institute of Aircraft Machine Engineering and Transport, National Research Irkutsk State Technical University, Irkutsk 664074, Russia

Materials 2017, 10(8), 899; https://doi.org/10.3390/ma10080899 - 3 Aug 2017

Cited by 2 | Viewed by 4558

Abstract

In this study, the rheological characteristics of a titanium alloy have been obtained by multi-dome bulging test. Free bulging process is an experimental technique that can be used to characterize material in conditions of biaxial tension during superplastic, as well as conventional, hot [...] Read more.

In this study, the rheological characteristics of a titanium alloy have been obtained by multi-dome bulging test. Free bulging process is an experimental technique that can be used to characterize material in conditions of biaxial tension during superplastic, as well as conventional, hot forming. The constitutive constants are calculated on a base of the information about the bulge geometry, applied pressure, and forming time. A multi-dome forming test allows one to reduce the number of the experiments required for the characterization, since every multi-dome test produces several domes of different size. In this study, a specific die for multi-dome test was used. The die has six holes with different radiuses of 20, 25, 30, 35, 40, and 45 mm. During a test, the specimen is clamped between blank holder and die holder, heated to a specific temperature, and formed by applying constant gas pressure. The experiments were conducted at different temperatures for OT4-1 titanium alloy. The constitutive constants were obtained by processing the experimental data using two different techniques and compared with tensile test results. In order to estimate the influence of friction on the experimental results and to verify obtained material characteristics, finite element (FE) simulation was performed. Finally, the results of FE simulation were compared with the experimental data. The results of the simulation show the advantage of material characterization based on multi dome tests and its interpretation by inverse analysis. The deviations produced by the effect of friction are more significant when the direct approach is applied instead of inverse analysis with a semi analytical model of the bulging process. Full article

(This article belongs to the Special Issue Wear-Corrosion Synergy, Nanocoating and Control of Materials)

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18 pages, 2934 KiB

Open AccessArticle

Effect of Calcium Carbonate Fineness on Calcium Sulfoaluminate-Belite Cement

by Yeonung Jeong¹

, Craig W. Hargis², Sungchul Chun^3,* and Juhyuk Moon^1,*

¹ Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576, Singapore

² Department of Construction Management, University of North Florida, 1 UNF Dr., Jacksonville, FL 32224, USA

³ Division of Architecture and Urban Design, Incheon National University, Incheon 22012, Korea

Materials 2017, 10(8), 900; https://doi.org/10.3390/ma10080900 - 3 Aug 2017

Cited by 63 | Viewed by 8134

Abstract

This study investigated the hydration characteristics and strength development of calcium sulfoaluminate-belite (CSAB) cements incorporating calcium carbonate (CC) powders with various particle size distributions and different gypsum amounts. In general, the CSAB hydration was accelerated by the CC powder, but the acceleration and [...] Read more.

This study investigated the hydration characteristics and strength development of calcium sulfoaluminate-belite (CSAB) cements incorporating calcium carbonate (CC) powders with various particle size distributions and different gypsum amounts. In general, the CSAB hydration was accelerated by the CC powder, but the acceleration and resulting strength improvement were more effective with finer CC powder. Regardless of the fineness of the CC powder, it took part in the hydration of CSAB cement, forming hemicarboaluminate and monocarboaluminate phases. These hydration and nucleation effects compensated for the strength reduction from decreased cementing components (i.e., dilution effect) when finer CC powders were used, while they did not overcome the strength reduction when coarser CC powder was used. On the other hand, increasing the amount of gypsum for a given CC content improved the strength. The strength of CSAB cement had a clear inverse relationship with its total pore volume measured by mercury intrusion porosimetry (MIP). Thermodynamic modeling for CSAB cement hydration showed that the use of CC powder increased total volume of solid phases up to 6 wt % at a given amount of gypsum. Full article

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7 pages, 876 KiB

Open AccessCommunication

Organosilica Membrane with Ionic Liquid Properties for Separation of Toluene/H₂ Mixture

by Yuichiro Hirota^1,*

, Yohei Maeda¹, Yusuke Yamamoto¹, Manabu Miyamoto² and Norikazu Nishiyama¹

¹ Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan

² Department of Chemistry and Biomolecular Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan

Materials 2017, 10(8), 901; https://doi.org/10.3390/ma10080901 - 3 Aug 2017

Cited by 16 | Viewed by 5248

Abstract

In this study, we present a new concept in chemically stabilized ionic liquid membranes: an ionic liquid organosilica (ILOS) membrane, which is an organosilica membrane with ionic liquid-like properties. A silylated ionic liquid was used as a precursor for synthesis. The permselectivity, permeation [...] Read more.

In this study, we present a new concept in chemically stabilized ionic liquid membranes: an ionic liquid organosilica (ILOS) membrane, which is an organosilica membrane with ionic liquid-like properties. A silylated ionic liquid was used as a precursor for synthesis. The permselectivity, permeation mechanism, and stability of the membrane in the H₂/toluene binary system were then compared with a supported ionic liquid membrane. The membrane showed a superior separation factor of toluene/H₂ (>17,000) in a binary mixture system based on a solution–diffusion mechanism with improved durability over the supported ionic liquid membrane. Full article

(This article belongs to the Section Porous Materials)

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18 pages, 9217 KiB

Open AccessArticle

Hot Press as a Sustainable Direct Recycling Technique of Aluminium: Mechanical Properties and Surface Integrity

by Nur Kamilah Yusuf

, Mohd Amri Lajis^* and Azlan Ahmad

Sustainable Manufacturing and Recycling Technology, Advanced Manufacturing and Materials Center (SMART-AMMC), Universiti Tun Hussein Onn Malaysia (UTHM), Parit Raja 86400, BatuPahat, Johor, Malaysia

Materials 2017, 10(8), 902; https://doi.org/10.3390/ma10080902 - 3 Aug 2017

Cited by 38 | Viewed by 8699

Abstract

Meltless recycling technique has been utilized to overcome the lack of primary resources, focusing on reducing the usage of energy and materials. Hot press was proposed as a novel direct recycling technique which results in astoundingly low energy usage in contrast with conventional [...] Read more.

Meltless recycling technique has been utilized to overcome the lack of primary resources, focusing on reducing the usage of energy and materials. Hot press was proposed as a novel direct recycling technique which results in astoundingly low energy usage in contrast with conventional recycling. The aim of this study is to prove the technical feasibility of this approach by characterizing the recycled samples. For this purpose, AA6061 aluminium chips were recycled by utilizing hot press process under various operating temperature (T_s= 430, 480, and 530 °C) and holding times (t_s= 60, 90, and 120 min). The maximum mechanical properties of recycled chip are Ultimate tensile strength (UTS) = 266.78 MPa, Elongation to failure (ETF) = 16.129%, while, for surface integrity of the chips, the calculated microhardness is 81.744 HV, exhibited at T_s = 530 °C and t_s = 120 min. It is comparable to theoretical AA6061 T4-temper where maximum UTS and microhardness is increased up to 9.27% and 20.48%, respectively. As the desired mechanical properties of forgings can only be obtained by means of a final heat treatment, T5-temper, aging after forging process was employed. Heat treated recycled billet AA6061 (T5-temper) are considered comparable with as-received AA6061 T6, where the value of microhardness (98.649 HV) at 175 °C and 120 min of aging condition was revealed to be greater than 3.18%. Although it is quite early to put a base mainly on the observations in experimental settings, the potential for significant improvement offered by the direct recycling methods for production aluminium scrap can be clearly demonstrated. This overtures perspectives for industrial development of solid state recycling processes as environmentally benign alternatives of current melting based practices. Full article

(This article belongs to the Special Issue Recycled Materials, Eco-design and 3D Printing)

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21 pages, 15664 KiB

Open AccessArticle

Pitting Corrosion Behaviour of New Corrosion-Resistant Reinforcement Bars in Chloride-Containing Concrete Pore Solution

by Jin-yang Jiang^1,2,*, Yao Liu^1,2, Hong-yan Chu^1,2, Danqian Wang^1,2, Han Ma³ and Wei Sun^1,2

¹ School of Materials Science and Engineering, Southeast University, Nanjing 211189, China

² Jiangsu Key Laboratory of Construction Materials, Nanjing 211189, China

³ Research Institute of Jiangsu Shasteel Iron and Steel, Zhangjiagang 215625, China

Materials 2017, 10(8), 903; https://doi.org/10.3390/ma10080903 - 4 Aug 2017

Cited by 26 | Viewed by 6855

Abstract

In this study, the pitting behaviour of a new corrosion-resistant alloy steel (CR) is compared to that of low-carbon steel (LC) in a simulated concrete pore solution with a chloride concentration of 5 mol/L. The electrochemical behaviour of the bars was characterised using [...] Read more.

In this study, the pitting behaviour of a new corrosion-resistant alloy steel (CR) is compared to that of low-carbon steel (LC) in a simulated concrete pore solution with a chloride concentration of 5 mol/L. The electrochemical behaviour of the bars was characterised using linear polarisation resistance (LPR) and electrochemical impedance spectroscopy (EIS). The pitting profiles were detected by reflective digital holographic microscopy (DHM), scanning electron microscopy (SEM), and the chemical components produced in the pitting process were analysed by X-ray energy dispersive spectroscopy (EDS). The results show that the CR bars have a higher resistance to pitting corrosion than the LC bars. This is primarily because of the periodic occurrence of metastable pitting during pitting development. Compared to the pitting process in the LC bars, the pitting depth grows slowly in the CR bars, which greatly reduces the risk of pitting. The possible reason for this result is that the capability of the CR bars to heal the passivation film helps to restore the metastable pits to the passivation state. Full article

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15 pages, 1935 KiB

Open AccessArticle

Mechanical Performance Evaluation of Self-Compacting Concrete with Fine and Coarse Recycled Aggregates from the Precast Industry

by Sara A. Santos¹, Pedro R. Da Silva^2,*

and Jorge De Brito³

¹ Civil Engineering Master, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal

² CERIS, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, 1959-007 Lisbon, Portugal

³ CERIS, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal

Materials 2017, 10(8), 904; https://doi.org/10.3390/ma10080904 - 4 Aug 2017

Cited by 55 | Viewed by 5063

Abstract

This paper intends to evaluate the feasibility of reintroducing recycled concrete aggregates in the precast industry. The mechanical properties of self-compacting concrete (SCC) with incorporation of recycled aggregates (RA) (coarse recycled aggregates (CRA) and fine recycled aggregates (FRA)) from crushed precast elements were [...] Read more.

This paper intends to evaluate the feasibility of reintroducing recycled concrete aggregates in the precast industry. The mechanical properties of self-compacting concrete (SCC) with incorporation of recycled aggregates (RA) (coarse recycled aggregates (CRA) and fine recycled aggregates (FRA)) from crushed precast elements were evaluated. The goal was to evaluate the ability of producing SCC with a minimum pre-established performance in terms of mechanical strength, incorporating variable ratios of RA (FRA/CRA%: 0/0%, 25/25%, 50/50%, 0/100% and 100/0%) produced from precast source concretes with similar target performances. This replication in SCC was made for two strength classes (45 MPa and 65 MPa), with the intention of obtaining as final result concrete with recycled aggregates whose characteristics are compatible with those of a SCC with natural aggregates in terms of workability and mechanical strength. The results enabled conclusions to be established regarding the SCC’s produced with fine and coarse recycled aggregates from the precast industry, based on its mechanical properties. The properties studied are strongly affected by the type and content of recycled aggregates. The potential demonstrated, mainly in the hardened state, by the joint use of fine and coarse recycled aggregate is emphasized. Full article

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10 pages, 2717 KiB

Open AccessArticle

Spectral Selectivity of Plasmonic Interactions between Individual Up-Converting Nanocrystals and Spherical Gold Nanoparticles

by Dawid Piątkowski^1,*, Mikołaj K. Schmidt², Magdalena Twardowska¹, Marcin Nyk³

, Javier Aizpurua² and Sebastian Maćkowski¹

¹ Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun, Poland

² Centro de Física de Materiales (MPC, CSIC-UPV/EHU) and Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián, Spain

³ Advanced Materials Engineering and Modelling Group, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland

Materials 2017, 10(8), 905; https://doi.org/10.3390/ma10080905 - 4 Aug 2017

Cited by 4 | Viewed by 4500

Abstract

We experimentally demonstrate strong spectral selectivity of plasmonic interaction that occurs between α-NaYF₄:Er³⁺/Yb³⁺ nanocrystals, which feature two emission bands, and spherical gold nanoparticles, with plasmon frequency resonant with one of the emission bands. Spatially–resolved luminescence intensity maps acquired [...] Read more.

We experimentally demonstrate strong spectral selectivity of plasmonic interaction that occurs between α-NaYF₄:Er³⁺/Yb³⁺ nanocrystals, which feature two emission bands, and spherical gold nanoparticles, with plasmon frequency resonant with one of the emission bands. Spatially–resolved luminescence intensity maps acquired for individual nanocrystals, together with microsecond luminescence lifetime images, show two qualitatively different effects that result from the coupling between plasmon excitations in metallic nanoparticles and emitting states of the nanocrystals. On the one hand, we observe nanocrystals, whose emission intensity is strongly enhanced for both resonant and non-resonant bands with respect to the plasmon resonance. Importantly, this increase is accompanied with shortening of luminescence decays times. In contrast, a significant number of nanocrystals exhibits almost complete quenching of the emission resonant with the plasmon resonance of gold nanoparticles. Theoretical analysis indicates that such an effect can occur for emitters placed at distances of about 5 nm from gold nanoparticles. While under these conditions, both transitions experience significant increases of the radiative emission rates due to the Purcell effect, the non-radiative energy transfer between resonant bands results in strong quenching, which in that situation nullifies the enhancement. Full article

(This article belongs to the Special Issue Advance in Plasmonics and Metamaterials)

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14 pages, 4985 KiB

Open AccessArticle

Influence of Thermal Contact Resistance of Aluminum Foams in Forced Convection: Experimental Analysis

by Stefano Guarino^*

, Giovanni Di Ilio

and Simone Venettacci

Department of Engineering, University of Rome ‘Niccolò Cusano’, Via Don Carlo Gnocchi 3, 00166 Roma, Italy

Materials 2017, 10(8), 907; https://doi.org/10.3390/ma10080907 - 5 Aug 2017

Cited by 16 | Viewed by 7309

Abstract

In this paper, the heat transfer performances of aluminum metal foams, placed on horizontal plane surface, was evaluated in forced convection conditions. Three different types of contacts between the sample and the heated base plate have been investigated: simple contact, brazed contact and [...] Read more.

In this paper, the heat transfer performances of aluminum metal foams, placed on horizontal plane surface, was evaluated in forced convection conditions. Three different types of contacts between the sample and the heated base plate have been investigated: simple contact, brazed contact and grease paste contact. First, in order to perform the study, an ad hoc experimental set-up was built. Second, the value of thermal contact resistance was estimated. The results show that both the use of a conductive paste and the brazing contact, realized by means of a copper electro-deposition, allows a great reduction of the global thermal resistance, increasing de facto the global heat transfer coefficient of almost 80%, compared to the simple contact case. Finally, it was shown that, while the contribution of thermal resistance is negligible for the cases of brazed and grease paste contact, it is significantly high for the case of simple contact. Full article

(This article belongs to the Section Porous Materials)

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18 pages, 8110 KiB

Open AccessArticle

Finite Element Modeling of Multilayer Orthogonal Auxetic Composites under Low-Velocity Impact

by Lili Jiang and Hong Hu^*

Institute of Textile and Clothing, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

Materials 2017, 10(8), 908; https://doi.org/10.3390/ma10080908 - 5 Aug 2017

Cited by 24 | Viewed by 7694

Abstract

The multilayer orthogonal auxetic composites have been previously developed and tested to prove that they own excellent energy absorption and impact protection characteristics in a specific strain range under low-velocity impact. In this study, a three dimensional finite element (FE) model in ANSYS [...] Read more.

The multilayer orthogonal auxetic composites have been previously developed and tested to prove that they own excellent energy absorption and impact protection characteristics in a specific strain range under low-velocity impact. In this study, a three dimensional finite element (FE) model in ANSYS LS-DYNA was established to simulate the mechanical behavior of auxetic composites under low-velocity drop-weight impact. The simulation results including the Poisson’s ratio versus compressive strain curves and the contact stress versus compressive strain curves were compared with those in the experiments. The clear deformation pictures of the FE models have provided a simple and effective way for investigating the damage mechanism and optimizing the material, as well as structure design. Full article

(This article belongs to the Special Issue Auxetic Materials 2017-2018)

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13 pages, 7269 KiB

Open AccessArticle

Failure Behavior of Unidirectional Composites under Compression Loading: Effect of Fiber Waviness

by Swaroop Narayanan Nair^1,2

, Aravind Dasari^3,*

, Chee Yoon Yue² and Srikanth Narasimalu⁴

¹ Energy Research Institute at NTU/Interdisciplinary Graduate School, Nanyang Technological University, block S2-B3a-01, 50 Nanyang Avenue, Singapore 639798, Singapore

² School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, 50 Nanyang Avenue, Singapore 639798, Singapore

³ School of Materials Science & Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

⁴ Energy Research Institute at NTU, Nanyang Technological University, Cleantech One, 1 Cleantech loop, #06-04, Singapore 637141, Singapore

Materials 2017, 10(8), 909; https://doi.org/10.3390/ma10080909 - 5 Aug 2017

Cited by 25 | Viewed by 7707

Abstract

The key objective of this work is to highlight the effect of manufacturing-induced fiber waviness defects on the compressive failure of glass fiber-reinforced unidirectional specimens. For this purpose, in-plane, through-thickness waviness defects (with different waviness severities) are induced during the manufacturing of the [...] Read more.

The key objective of this work is to highlight the effect of manufacturing-induced fiber waviness defects on the compressive failure of glass fiber-reinforced unidirectional specimens. For this purpose, in-plane, through-thickness waviness defects (with different waviness severities) are induced during the manufacturing of the laminate. Numerical and experimental results show that the compressive strength of the composites decreases as the severity of the waviness defects increases. A reduction of up to 75% is noted with a wave severity of 0.075. Optical and scanning electron microscopy observations of the failed specimens reveal that kink-bands are created in the wavy regions and lead to failure. Full article

(This article belongs to the Section Advanced Composites)

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12 pages, 5970 KiB

Open AccessArticle

Incorporation of Collagen in Calcium Phosphate Cements for Controlling Osseointegration

by Ming-Hsien Hu^1,2,3,†, Pei-Yuan Lee^1,2,†, Wen-Cheng Chen^4,*

and Jin-Jia Hu^1,5,*

¹ Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan

² Department of Orthopedics, Show-Chwan Memorial Hospital, Changhua 50544, Taiwan

³ Department of Orthopedic Surgery, Faculty of Medicine, National Yang-Ming University, Taipei 112, Taiwan

⁴ Department of Fiber and Composite Materials, College of Engineering, Feng Chia University, Taichung 40724, Taiwan

⁵ Medical Device Innovation Center, National Cheng Kung University, Tainan 701, Taiwan

^† Ming-Hsien Hu and Pei-Yuan Lee had equal contribution to this study.

Materials 2017, 10(8), 910; https://doi.org/10.3390/ma10080910 - 6 Aug 2017

Cited by 16 | Viewed by 5645

Abstract

In this study, we investigated the effect of supplementing a non-dispersive dicalcium phosphate-rich calcium phosphate bone cement (DCP-rich CPC) with type I collagen on in vitro cellular activities and its performance as a bone graft material. Varying amounts of type I collagen were [...] Read more.

In this study, we investigated the effect of supplementing a non-dispersive dicalcium phosphate-rich calcium phosphate bone cement (DCP-rich CPC) with type I collagen on in vitro cellular activities and its performance as a bone graft material. Varying amounts of type I collagen were added during the preparation of the DCP-rich CPC. In vitro cell adhesion, morphology, viability, and alkaline phosphatase (ALP) activity were evaluated using progenitor bone cells. Bone graft performance was evaluated via a rat posterolateral lumbar fusion model and osteointegration of the implant. New bone formations in the restorative sites were assessed by micro-computed tomography (micro-CT) and histological analysis. We found that the incorporation of collagen into the DCP-rich CPC was associated with increased cell adhesion, cell viability, and ALP activity in vitro. The spinal fusion model revealed a significant increase in bone regeneration. Additionally, better osseointegration was observed between the host bone and graft with the DCP-rich CPC supplemented with collagen than with the collagen-free DCP-rich CPC control graft. Furthermore, compared to the control graft, the results of micro-CT showed that a smaller amount of residual material was observed with the collagen-containing DCP-rich CPC graft compared with the control graft, which suggests the collagen supplement enhanced new bone formation. Of the different mixtures evaluated in this study (0.8 g DCP-rich CPC supplemented with 0.1, 0.2, and 0.4 mL type I collagen, respectively), DCP-rich CPC supplemented with 0.4 mL collagen led to the highest level of osteogenesis. Our results suggest that the DCP-rich CPC supplemented with collagen has potential to be used as an effective bone graft material in spinal surgery. Full article

(This article belongs to the Special Issue Biocompatibility of Materials)

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15 pages, 5294 KiB

Open AccessArticle

Influence of Partially Debonded Interface on Elasticity of Syntactic Foam: A Numerical Study

by Yi Je Cho¹

, Youngjeong Kang², Young Cheol Lee², Yongho Park¹ and Wookjin Lee^2,*

¹ Department of Materials Science and Engineering, Pusan National University, Busandaehak-ro 63beon-gil 2, Busan 46241, Korea

² Korea Institute of Industrial Technology (KITECH), Namyangsan 1-gil 14, Yangsan 50635, Korea

Materials 2017, 10(8), 911; https://doi.org/10.3390/ma10080911 - 8 Aug 2017

Cited by 13 | Viewed by 5252

Abstract

The effect of interfacial bonding of glass hollow microspheres and a polymer matrix on the elastic properties of syntactic foam was investigated using representative volume element (RVE) models, including partially debonded interfaces. Finite element analysis, with models having different debonding geometries, was performed [...] Read more.

The effect of interfacial bonding of glass hollow microspheres and a polymer matrix on the elastic properties of syntactic foam was investigated using representative volume element (RVE) models, including partially debonded interfaces. Finite element analysis, with models having different debonding geometries, was performed to numerically estimate the elastic behavior of the models. The models consisted of bonded and debonded regions of interfaces; the bonded region was treated as the perfectly bonded interface, while the Coulomb friction model was used to describe the debonded region with a small friction coefficient. The changes in the tensile and compressive moduli of the foams were investigated in terms of the degree of interfacial debonding and debonding geometry. Full article

(This article belongs to the Special Issue Syntactic Foams: Microstructural Characterisation and Effective Properties)

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14 pages, 3267 KiB

Open AccessArticle

Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations

by Zhenyang Ma^*, Xuhong Liu, Xinhai Yu, Chunlei Shi and Dayun Wang

Tianjin Key Laboratory for Civil Aircraft Airworthiness and Maintenance, Civil Aviation University of China, Tianjin 300300, China

Materials 2017, 10(8), 912; https://doi.org/10.3390/ma10080912 - 8 Aug 2017

Cited by 4 | Viewed by 5944

Abstract

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca-XN (X = C, Si, Ge) are investigated in this work using the Perdew–Burke–Ernzerhof (PBE) functional, Perdew–Burke–Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA–PZ) functional in [...] Read more.

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca-XN (X = C, Si, Ge) are investigated in this work using the Perdew–Burke–Ernzerhof (PBE) functional, Perdew–Burke–Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA–PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca-CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca-XN (X = C, Si, Ge) show that Pbca-SiN and Pbca-GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca-XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson’s ratio, bulk modulus, shear modulus, Young’s modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca-CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young’s modulus than the (100) plane. Full article

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17 pages, 10253 KiB

Open AccessFeature PaperArticle

Hydrophobic Coatings by Thiol-Ene Click Functionalization of Silsesquioxanes with Tunable Architecture

by Sandra Dirè^1,*

, Davide Bottone^1,*

, Emanuela Callone¹

, Devid Maniglio¹

, Isabelle Génois² and François Ribot²

¹ Department of Industrial Engineering, University of Trento, via Sommarive 9, 30123 Trento, Italy

² Sorbonne Universités, UPMC University Paris 06—CNRS—College de France, UMR 7574, Laboratoire de Chimie de la Matière Condensée de Paris, 4 place Jussieu, 75005 Paris, France

Materials 2017, 10(8), 913; https://doi.org/10.3390/ma10080913 - 8 Aug 2017

Cited by 4 | Viewed by 5033

Abstract

The hydrolysis-condensation of trialkoxysilanes under strictly controlled conditions allows the production of silsesquioxanes (SSQs) with tunable size and architecture ranging from ladder to cage-like structures. These nano-objects can serve as building blocks for the preparation of hybrid organic/inorganic materials with selected properties. The [...] Read more.

The hydrolysis-condensation of trialkoxysilanes under strictly controlled conditions allows the production of silsesquioxanes (SSQs) with tunable size and architecture ranging from ladder to cage-like structures. These nano-objects can serve as building blocks for the preparation of hybrid organic/inorganic materials with selected properties. The SSQs growth can be tuned by simply controlling the reaction duration in the in situ water production route (ISWP), where the kinetics of the esterification reaction between carboxylic acids and alcohols rules out the extent of organosilane hydrolysis-condensation. Tunable SSQs with thiol functionalities (SH-NBBs) are suitable for further modification by exploiting the simple thiol-ene click reaction, thus allowing for modifying the wettability properties of derived coatings. In this paper, coatings were prepared from SH-NBBs with different architecture onto cotton fabrics and paper, and further functionalized with long alkyl chains by means of initiator-free UV-induced thiol-ene coupling with 1-decene (C10) and 1-tetradecene (C14). The coatings appeared to homogeneously cover the natural fibers and imparted a multi-scale roughness that was not affected by the click functionalization step. The two-step functionalization of cotton and paper warrants a stable highly hydrophobic character to the surface of natural materials that, in perspective, suggests a possible application in filtration devices for oil-water separation. Furthermore, the purification of SH-NBBs from ISWP by-products was possible during the coating process, and this step allowed for the fast, initiator-free, click-coupling of purified NBBs with C10 and C14 in solution with a nearly quantitative yield. Therefore, this approach is an alternative route to get sol-gel-derived, ladder-like, and cage-like SSQs functionalized with long alkyl chains. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry Applied to Materials Science)

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12 pages, 10844 KiB

Open AccessArticle

Load-Deflection and Friction Properties of PEEK Wires as Alternative Orthodontic Wires

by Yoshifumi Tada^1,*, Tohru Hayakawa² and Yoshiki Nakamura¹

¹ Department of Orthodontics, Tsurumi University School of Dental Medicine, Yokohama 230-8501, Japan

² Department of Dental Engineering, Tsurumi University School of Dental Medicine, Yokohama 230-8501, Japan

Materials 2017, 10(8), 914; https://doi.org/10.3390/ma10080914 - 9 Aug 2017

Cited by 23 | Viewed by 5937

Abstract

Polyetheretherketone (PEEK) is now attracting attention as an alternative to metal alloys in the dental field. In the present study, we evaluated the load-deflection characteristics of PEEK wires in addition to their frictional properties. Three types of PEEK wires are used: two sizes [...] Read more.

Polyetheretherketone (PEEK) is now attracting attention as an alternative to metal alloys in the dental field. In the present study, we evaluated the load-deflection characteristics of PEEK wires in addition to their frictional properties. Three types of PEEK wires are used: two sizes of rectangular shape, 0.016 × 0.022 in² and 0.019 × 0.025 in² (19-25PEEK), and rounded shape, diameter 0.016 in (16PEEK). As a control, Ni-Ti orthodontic wire, diameter 0.016 in, was used. The three-point bending properties were evaluated in a modified three-point bending system for orthodontics. The static friction between the orthodontic wire and the bracket was also measured. The load-deflection curves were similar among Ni-Ti and PEEK wires, except for 16PEEK with slot-lid ligation. The bending force of 19-25PEEK wire was comparable with that of Ni-Ti wire. 19-25PEEK showed the highest load at the deflection of 1500 μm (p < 0.05) in the case of slot-lid ligation. No significant differences were seen in the permanent deformation between Ni-Ti and all three PEEK wires (p > 0.05). No significant difference was seen in static friction between all three PEEK wires and Ni-Ti wire (p > 0.05). It is suggested that 19-25PEEK will be applicable for orthodontic treatment with the use of slot-lid ligation. Full article

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17 pages, 2715 KiB

Open AccessArticle

Short-Term Behavior of Slag Concretes Exposed to a Real In Situ Mediterranean Climate Environment

by José Marcos Ortega^1,*

, Isidro Sánchez¹

, Marta Cabeza²

and Miguel Ángel Climent¹

¹ Departamento de Ingeniería Civil, Universidad de Alicante, Ap. Correos 99, 03080 Alacant/Alicante, Spain

² Grupo ENCOMAT, Escola de Enxeñaría Industrial, Universidade de Vigo, Campus Universitario, 36310 Vigo, Spain

Materials 2017, 10(8), 915; https://doi.org/10.3390/ma10080915 - 8 Aug 2017

Cited by 12 | Viewed by 3876

Abstract

At present, one of the most suitable ways to get a more sustainable cement industry is to reduce the CO₂ emissions generated during cement production. In order to reach that goal, the use of ground granulated blast-furnace slag as clinker replacement is [...] Read more.

At present, one of the most suitable ways to get a more sustainable cement industry is to reduce the CO₂ emissions generated during cement production. In order to reach that goal, the use of ground granulated blast-furnace slag as clinker replacement is becoming increasingly popular. Although the effects of this addition in the properties of cementitious materials are influenced by their hardening conditions, there are not too many experimental studies in which slag concretes have been exposed to real in situ environments. Then, the main objective of this research is to study the short-term effects of exposure to real Mediterranean climate environment of an urban site, where the action of airborne chlorides from sea water and the presence of CO₂ are combined, in the microstructure and service properties of a commercial slag cement concrete, compared to ordinary Portland cement (OPC). The microstructure was studied with mercury intrusion porosimetry. The effective porosity, capillary suction coefficient, chloride migration coefficient, carbonation front depth, and compressive strength were also analyzed. Considering the results obtained, slag concretes exposed to a real in situ Mediterranean climate environment show good service properties in the short-term (180 days), in comparison with OPC. Full article

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18 pages, 3742 KiB

Open AccessArticle

Characteristics of Carrier Transport and Crystallographic Orientation Distribution of Transparent Conductive Al-Doped ZnO Polycrystalline Films Deposited by Radio-Frequency, Direct-Current, and Radio-Frequency-Superimposed Direct-Current Magnetron Sputtering

by Junichi Nomoto^1,*, Katsuhiko Inaba², Shintaro Kobayashi², Takeshi Watanabe³, Hisao Makino¹ and Tetsuya Yamamoto¹

¹ Research Institute, Kochi University of Technology, Kochi 782-8502, Japan

² X-Ray Research Laboratory, Rigaku Corporation, Tokyo 196-8666, Japan

³ Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Hyogo 679-5198, Japan

Materials 2017, 10(8), 916; https://doi.org/10.3390/ma10080916 - 9 Aug 2017

Cited by 17 | Viewed by 12063

Abstract

We investigated the characteristics of carrier transport and crystallographic orientation distribution in 500-nm-thick Al-doped ZnO (AZO) polycrystalline films to achieve high-Hall-mobility AZO films. The AZO films were deposited on glass substrates at 200 °C by direct-current, radio-frequency, or radio-frequency-superimposed direct-current magnetron sputtering at [...] Read more.

We investigated the characteristics of carrier transport and crystallographic orientation distribution in 500-nm-thick Al-doped ZnO (AZO) polycrystalline films to achieve high-Hall-mobility AZO films. The AZO films were deposited on glass substrates at 200 °C by direct-current, radio-frequency, or radio-frequency-superimposed direct-current magnetron sputtering at various power ratios. We used sintered AZO targets with an Al₂O₃ content of 2.0 wt. %. The analysis of the data obtained by X-ray diffraction, Hall-effect, and optical measurements of AZO films at various power ratios showed that the complex orientation texture depending on the growth process enhanced the contribution of grain boundary scattering to carrier transport and of carrier sinks on net carrier concentration, resulting in the reduction in the Hall mobility of polycrystalline AZO films. Full article

(This article belongs to the Special Issue Advances in Transparent Conducting Materials)

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23 pages, 39469 KiB

Open AccessArticle

Modeling Adhesive Anchors in a Discrete Element Framework

by Marco Marcon¹, Jan Vorel^1,2, Krešimir Ninčević¹ and Roman Wan-Wendner^1,*

¹ Christian Doppler Laboratory LiCRoFast, Department of Civil Engineering and Natural Hazards, University of Natural Resources and Life Sciences (BOKU), 1190 Vienna, Austria

² Department of Mechanics, Faculty of Civil Engineering, Czech Technical University in Prague, 16629 Prague, Czech Republic

Materials 2017, 10(8), 917; https://doi.org/10.3390/ma10080917 - 8 Aug 2017

Cited by 42 | Viewed by 6044

Abstract

In recent years, post-installed anchors are widely used to connect structural members and to fix appliances to load-bearing elements. A bonded anchor typically denotes a threaded bar placed into a borehole filled with adhesive mortar. The high complexity of the problem, owing to [...] Read more.

In recent years, post-installed anchors are widely used to connect structural members and to fix appliances to load-bearing elements. A bonded anchor typically denotes a threaded bar placed into a borehole filled with adhesive mortar. The high complexity of the problem, owing to the multiple materials and failure mechanisms involved, requires a numerical support for the experimental investigation. A reliable model able to reproduce a system’s short-term behavior is needed before the development of a more complex framework for the subsequent investigation of the lifetime of fasteners subjected to various deterioration processes can commence. The focus of this contribution is the development and validation of such a model for bonded anchors under pure tension load. Compression, modulus, fracture and splitting tests are performed on standard concrete specimens. These serve for the calibration and validation of the concrete constitutive model. The behavior of the adhesive mortar layer is modeled with a stress-slip law, calibrated on a set of confined pull-out tests. The model validation is performed on tests with different configurations comparing load-displacement curves, crack patterns and concrete cone shapes. A model sensitivity analysis and the evaluation of the bond stress and slippage along the anchor complete the study. Full article

(This article belongs to the Section Advanced Materials Characterization)

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9 pages, 4252 KiB

Open AccessArticle

320-nm Flexible Solution-Processed 2,7-dioctyl[1] benzothieno[3,2-b]benzothiophene Transistors

by Hang Ren, Qingxin Tang^*, Yanhong Tong and Yichun Liu

Centre for Advanced Optoelectronic Functional Materials Research and Key Laboratory of UV-Emitting Materials and Technology, Northeast Normal University, Ministry of Education, Changchun 130024, China

Materials 2017, 10(8), 918; https://doi.org/10.3390/ma10080918 - 9 Aug 2017

Cited by 21 | Viewed by 6099

Abstract

Flexible organic thin-film transistors (OTFTs) have received extensive attention due to their outstanding advantages such as light weight, low cost, flexibility, large-area fabrication, and compatibility with solution-processed techniques. However, compared with a rigid substrate, it still remains a challenge to obtain good device [...] Read more.

Flexible organic thin-film transistors (OTFTs) have received extensive attention due to their outstanding advantages such as light weight, low cost, flexibility, large-area fabrication, and compatibility with solution-processed techniques. However, compared with a rigid substrate, it still remains a challenge to obtain good device performance by directly depositing solution-processed organic semiconductors onto an ultrathin plastic substrate. In this work, ultrathin flexible OTFTs are successfully fabricated based on spin-coated 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) films. The resulting device thickness is only ~320 nm, so the device has the ability to adhere well to a three-dimension curved surface. The ultrathin C8-BTBT OTFTs exhibit a mobility as high as 4.36 cm² V⁻¹ s⁻¹ and an on/off current ratio of over 10⁶. These results indicate the substantial promise of our ultrathin flexible C8-BTBT OTFTs for next-generation flexible and conformal electronic devices. Full article

(This article belongs to the Special Issue Highly Ordered Organic Thin Films)

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13 pages, 10287 KiB

Open AccessArticle

Grain Refinement and Mechanical Properties of Cu–Cr–Zr Alloys with Different Nano-Sized TiC_p Addition

by Dongdong Zhang, Fang Bai, Yong Wang, Jinguo Wang^* and Wenquan Wang^*

Key Laboratory of Automobile Materials of Ministry of Education, Department of Materials Science and Engineering, Jilin University, Changchun 130025, China

Materials 2017, 10(8), 919; https://doi.org/10.3390/ma10080919 - 8 Aug 2017

Cited by 13 | Viewed by 4800

Abstract

The TiC_p/Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiC_p/Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu–Cr–Zr alloys to fabricate the nano-sized TiC_p-reinforced Cu–Cr–Zr composites. Results show that [...] Read more.

The TiC_p/Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiC_p/Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu–Cr–Zr alloys to fabricate the nano-sized TiC_p-reinforced Cu–Cr–Zr composites. Results show that nano-sized TiC_p can effectively refine the grain size of Cu–Cr–Zr alloys. The morphologies of grain in Cu–Cr–Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiC_p. The grain size decreased from 82 to 28 μm with the nano-sized TiC_p content. Compared with Cu–Cr–Zr alloys, the ultimate compressive strength (σ_UCS) and yield strength (σ_0.2) of 4 wt% TiC_p-reinforced Cu–Cr–Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu–Cr–Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiC_p-reinforced Cu–Cr–Zr composites decreased with the increasing TiC_p content under abrasive particles. The eletrical conductivity of Cu–Cr–Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu–Cr–Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively. Full article

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16 pages, 16140 KiB

Open AccessArticle

Interfacial Reaction and Mechanical Properties of Sn-Bi Solder joints

by Fengjiang Wang^1,*

, Ying Huang¹, Zhijie Zhang¹ and Chao Yan^2,*

¹ Key Laboratory of Advanced Welding Technology of Jiangsu Province, Jiangsu University of Science and Technology, Zhenjiang 212003, China

² School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China

Materials 2017, 10(8), 920; https://doi.org/10.3390/ma10080920 - 9 Aug 2017

Cited by 91 | Viewed by 10117

Abstract

Sn-Bi solder with different Bi content can realize a low-to-medium-to-high soldering process. To obtain the effect of Bi content in Sn-Bi solder on the microstructure of solder, interfacial behaviors in solder joints with Cu and the joints strength, five Sn-Bi solders including Sn-5Bi [...] Read more.

Sn-Bi solder with different Bi content can realize a low-to-medium-to-high soldering process. To obtain the effect of Bi content in Sn-Bi solder on the microstructure of solder, interfacial behaviors in solder joints with Cu and the joints strength, five Sn-Bi solders including Sn-5Bi and Sn-15Bi solid solution, Sn-30Bi and Sn-45Bi hypoeutectic and Sn-58Bi eutectic were selected in this work. The microstructure, interfacial reaction under soldering and subsequent aging and the shear properties of Sn-Bi solder joints were studied. Bi content in Sn-Bi solder had an obvious effect on the microstructure and the distribution of Bi phases. Solid solution Sn-Bi solder was composed of the β-Sn phases embedded with fine Bi particles, while hypoeutectic Sn-Bi solder was composed of the primary β-Sn phases and Sn-Bi eutectic structure from networked Sn and Bi phases, and eutectic Sn-Bi solder was mainly composed of a eutectic structure from short striped Sn and Bi phases. During soldering with Cu, the increase on Bi content in Sn-Bi solder slightly increased the interfacial Cu₆Sn₅ intermetallic compound (IMC)thickness, gradually flattened the IMC morphology, and promoted the accumulation of more Bi atoms to interfacial Cu₆Sn₅ IMC. During the subsequent aging, the growth rate of the IMC layer at the interface of Sn-Bi solder/Cu rapidly increased from solid solution Sn-Bi solder to hypoeutectic Sn-Bi solder, and then slightly decreased for Sn-58Bi solder joints. The accumulation of Bi atoms at the interface promoted the rapid growth of interfacial Cu₆Sn₅ IMC layer in hypoeutectic or eutectic Sn-Bi solder through blocking the formation of Cu₆Sn₅ in solder matrix and the transition from Cu₆Sn₅ to Cu₃Sn. Ball shear tests on Sn-Bi as-soldered joints showed that the increase of Bi content in Sn-Bi deteriorated the shear strength of solder joints. The addition of Bi into Sn solder was also inclined to produce brittle morphology with interfacial fracture, which suggests that the addition of Bi increased the shear resistance strength of Sn-Bi solder. Full article

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10 pages, 2272 KiB

Open AccessArticle

A Unique 3D Nitrogen-Doped Carbon Composite as High-Performance Oxygen Reduction Catalyst

by Ramesh Karunagaran¹, Tran Thanh Tung¹, Cameron Shearer³

, Diana Tran¹

, Campbell Coghlan², Christian Doonan^2,* and Dusan Losic^1,*

¹ School of Chemical Engineering, University of Adelaide, SA 5005, Australia

² School of Chemistry, University of Adelaide, SA 5005, Australia

³ School of Chemical and Physical Sciences, Flinders University, SA 5005, Australia

Materials 2017, 10(8), 921; https://doi.org/10.3390/ma10080921 - 9 Aug 2017

Cited by 14 | Viewed by 6327

Abstract

The synthesis and properties of an oxygen reduction catalyst based on a unique 3-dimensional (3D) nitrogen doped (N-doped) carbon composite are described. The composite material is synthesised via a two-step hydrothermal and pyrolysis method using bio-source low-cost materials of galactose and melamine. Firstly, [...] Read more.

The synthesis and properties of an oxygen reduction catalyst based on a unique 3-dimensional (3D) nitrogen doped (N-doped) carbon composite are described. The composite material is synthesised via a two-step hydrothermal and pyrolysis method using bio-source low-cost materials of galactose and melamine. Firstly, the use of iron salts and galactose to hydrothermally produceiron oxide (Fe₂O₃) magnetic nanoparticle clusters embedded carbon spheres. Secondly, magnetic nanoparticles diffused out of the carbon sphere when pyrolysed in the presence of melamine as nitrogen precursor. Interestingly, many of these nanoparticles, as catalyst-grown carbon nanotubes (CNTs), resulted in the formation of N-doped CNTs and N-doped carbon spheres under the decomposition of carbon and a nitrogen environment. The composite material consists of integrated N-doped carbon microspheres and CNTs show high ORR activity through a predominantly four-electron pathway. Full article

(This article belongs to the Section Advanced Composites)

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15 pages, 2523 KiB

Open AccessArticle

Multiaxial Fatigue Damage Parameter and Life Prediction without Any Additional Material Constants

by Zheng-Yong Yu¹, Shun-Peng Zhu^1,2,*

, Qiang Liu¹ and Yunhan Liu¹

¹ Center for System Reliability & Safety, University of Electronic Science and Technology of China, Chengdu 611731, China

² Key Laboratory of Deep Earth Science and Engineering, Ministry of Education, Sichuan University, Chengdu 610065, China

Materials 2017, 10(8), 923; https://doi.org/10.3390/ma10080923 - 9 Aug 2017

Cited by 94 | Viewed by 6760

Abstract

Based on the critical plane approach, a simple and efficient multiaxial fatigue damage parameter with no additional material constants is proposed for life prediction under uniaxial/multiaxial proportional and/or non-proportional loadings for titanium alloy TC4 and nickel-based superalloy GH4169. Moreover, two modified Ince-Glinka fatigue [...] Read more.

Based on the critical plane approach, a simple and efficient multiaxial fatigue damage parameter with no additional material constants is proposed for life prediction under uniaxial/multiaxial proportional and/or non-proportional loadings for titanium alloy TC4 and nickel-based superalloy GH4169. Moreover, two modified Ince-Glinka fatigue damage parameters are put forward and evaluated under different load paths. Results show that the generalized strain amplitude model provides less accurate life predictions in the high cycle life regime and is better for life prediction in the low cycle life regime; however, the generalized strain energy model is relatively better for high cycle life prediction and is conservative for low cycle life prediction under multiaxial loadings. In addition, the Fatemi–Socie model is introduced for model comparison and its additional material parameter k is found to not be a constant and its usage is discussed. Finally, model comparison and prediction error analysis are used to illustrate the superiority of the proposed damage parameter in multiaxial fatigue life prediction of the two aviation alloys under various loadings. Full article

(This article belongs to the Special Issue The Life of Materials at High Temperatures)

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13 pages, 4558 KiB

Open AccessArticle

Histological and Immunohistochemical Analyses of Repair of the Disc in the Rabbit Temporomandibular Joint Using a Collagen Template

by Kuo-Hwa Wang^1,†, Wing P. Chan^2,†, Li-Hsuan Chiu³, Yu-Hui Tsai⁴, Chia-Lang Fang⁵, Charn-Bing Yang¹, Kuan-Chou Chen¹, Hung-Li Tsai^4,‡ and Wen-Fu Lai^1,3,6,*

¹ Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei 11031, Taiwan

² Department of Radiology, School of Medicine, College of Medicine, Taipei Medical Univesity, Taipei 110, Taiwan

³ McLean Imaging Center, Harvard Medical School, Belmont, MA 02478, USA

⁴ Graduate Institute of Medical Sciences, Taipei Medical University, Taipei 11031, Taiwan

⁵ Department of Pathology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 11031, Taiwan

⁶ School of Dentistry, College of Dentistry, Taipei Medical University, Taipei 11031, Taiwan

^† Co-first authors contributed equally to this article.

^‡ Co-corresponding author.

Materials 2017, 10(8), 924; https://doi.org/10.3390/ma10080924 - 9 Aug 2017

Cited by 15 | Viewed by 5918

Abstract

A previous study demonstrated that the reconstituted type I collagen matrix extracted from rabbit tendons enabled the TMJ disc to regenerate in the rabbit. The aim of this study was to investigate changes in the extracellular matrix (ECM) and mechanisms of regeneration in [...] Read more.

A previous study demonstrated that the reconstituted type I collagen matrix extracted from rabbit tendons enabled the TMJ disc to regenerate in the rabbit. The aim of this study was to investigate changes in the extracellular matrix (ECM) and mechanisms of regeneration in the TMJ disc. In 36 New Zealand rabbits that underwent a partial discectomy, discs were replaced with reconstituted collagen templates for 3 months. A histological analysis showed that moderate to severe degeneration appeared in partially discectomized joints without implantation. In contrast, discs experienced regeneration of reconstituted collagen template implantation and the joint returned to normal function. Cells in the regenerative tissue expressed ECM, and fibers became regular and compact due to tissue remodeling over time. Reparative cells differentiated into chondroblasts, and showed highly dense pericellular fibers. The morphology and collagen composition of the disc and condyle in the 3-month experimental group were similar to those of normal tissues. In conclusion, the reconstituted collagen template facilitated the regeneration of surgically discectomized discs. Type I and type II collagens play a crucial role in the regeneration of articular discs. Full article

(This article belongs to the Section Biomaterials)

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29 pages, 6986 KiB

Open AccessArticle

Health State Monitoring of Bladed Machinery with Crack Growth Detection in BFG Power Plant Using an Active Frequency Shift Spectral Correction Method

by Weifang Sun¹, Bin Yao¹, Yuchao He¹, Binqiang Chen^1,*

, Nianyin Zeng¹ and Wangpeng He²

¹ Institute of Intelligent Equipment and Smart Manufacturing, School of Aerospace Engineering, Xiamen University, Xiamen 361005, China

² School of Aerospace Science and Technology, Xi’an 710075, China

Materials 2017, 10(8), 925; https://doi.org/10.3390/ma10080925 - 9 Aug 2017

Cited by 5 | Viewed by 5183

Abstract

Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG) in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety [...] Read more.

Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG) in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information) belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)

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12 pages, 1823 KiB

Open AccessArticle

The Effect of Temperature on Moisture Transport in Concrete

by Yao Wang^1,* and Yunping Xi²

¹ Department of Civil, Environmental and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA

² Department of Civil, Environmental and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA

Materials 2017, 10(8), 926; https://doi.org/10.3390/ma10080926 - 9 Aug 2017

Cited by 21 | Viewed by 4243

Abstract

Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature [...] Read more.

Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter D_HT, which can be determined by the present test data. The test results indicated that D_HT is not a constant but increases linearly with the temperature variation. A material model was developed for D_HT based on the experimental results obtained in this study. Full article

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12 pages, 2142 KiB

Open AccessArticle

Dehydrothermally Cross-Linked Collagen Membrane with a Bone Graft Improves Bone Regeneration in a Rat Calvarial Defect Model

by Yin-Zhe An¹

, Young-Ku Heo², Jung-Seok Lee¹, Ui-Won Jung¹ and Seong-Ho Choi^1,*

¹ Department of Periodontology, Research Institute for Periodontal Regeneration, College of Dentistry, Yonsei University, Seoul 03722, Korea

² Global Academy of Osseointegration, Neobiotech Co., Ltd., Seoul 06072, Korea

Materials 2017, 10(8), 927; https://doi.org/10.3390/ma10080927 - 10 Aug 2017

Cited by 18 | Viewed by 6541

Abstract

In this study, the bone regeneration efficacy of dehydrothermally (DHT) cross-linked collagen membrane with or without a bone graft (BG) material was evaluated in a critical-sized rat model. An 8-mm-diameter defect was created in the calvaria of 40 rats, which were randomized into [...] Read more.

In this study, the bone regeneration efficacy of dehydrothermally (DHT) cross-linked collagen membrane with or without a bone graft (BG) material was evaluated in a critical-sized rat model. An 8-mm-diameter defect was created in the calvaria of 40 rats, which were randomized into four groups: (1) control; (2) DHT; (3) BG; and, (4) DHT + BG. Evaluations were made at 2 and 8 weeks after surgery using micro-computed tomographic (micro-CT), histological, and histomorphometric analyses. Micro-CT analysis showed an increase in the new bone volume (NBV) of the BG and DHT + BG groups at 2 weeks after surgery, representing a significant difference (p < 0.05). At 8 weeks after surgery, the NBV increased in all four groups. However, larger NBVs were observed in the BG and DHT + BG groups, and a significant difference was no longer observed between the two groups. Histologic analysis demonstrated that the graft materials sustained the center of the defect in the BG and DHT + BG groups, which was shown in histomorphometric analysis as well. These results suggest that DHT membrane is a safe biomaterial with adequate tissue integration, and has a positive effect on new bone formation. Moreover, the best effects were achieved when DHT was used in conjunction with BG materials. Full article

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14 pages, 7962 KiB

Open AccessArticle

Tribological Properties of Aluminium Alloy Composites Reinforced with Multi-Layer Graphene—The Influence of Spark Plasma Texturing Process

by Marek Kostecki^*, Jarosław Woźniak, Tomasz Cygan, Mateusz Petrus and Andrzej Olszyna

Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska St. 141, 02-507 Warsaw, Poland

Materials 2017, 10(8), 928; https://doi.org/10.3390/ma10080928 - 10 Aug 2017

Cited by 25 | Viewed by 4690

Abstract

Self-lubricating composites are designed to obtain materials that reduce energy consumption, improve heat dissipation between moving bodies, and eliminate the need for external lubricants. The use of a solid lubricant in bulk composite material always involves a significant reduction in its mechanical properties, [...] Read more.

Self-lubricating composites are designed to obtain materials that reduce energy consumption, improve heat dissipation between moving bodies, and eliminate the need for external lubricants. The use of a solid lubricant in bulk composite material always involves a significant reduction in its mechanical properties, which is usually not an optimal solution. The growing interest in multilayer graphene (MLG), characterised by interesting properties as a component of composites, encouraged the authors to use it as an alternative solid lubricant in aluminium matrix composites instead of graphite. Aluminium alloy 6061 matrix composite reinforced with 2–15 vol % of MLG were synthesised by the spark plasma sintering process (SPS) and its modification, spark plasma texturing (SPT), involving deformation of the pre-sintered body in a larger diameter matrix. It was found that the application of the SPT method improves the density and hardness of the composites, resulting in improved tribological properties, particularly in the higher load regime. Full article

(This article belongs to the Section Energy Materials)

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9 pages, 3274 KiB

Open AccessArticle

Energy Transfer Efficiency from ZnO-Nanocrystals to Eu³⁺ Ions Embedded in SiO₂ Film for Emission at 614 nm

by Vivek Mangalam¹ and Kantisara Pita^1,2,*

¹ OPTIMUS, Centre for OptoElectronics and Biophotonics, School of Electrical and Electronic Engineering, Nanyang Technological University (NTU), Block S2, 50 Nanyang Avenue, Singapore 639798, Singapore

² CINTRA, CNRS-NTU-Thales UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 6, Singapore 637553, Singapore

Materials 2017, 10(8), 930; https://doi.org/10.3390/ma10080930 - 10 Aug 2017

Cited by 15 | Viewed by 4735

Abstract

In this work, we study the energy transfer mechanism from ZnO nanocrystals (ZnO-nc) to Eu³⁺ ions by fabricating thin-film samples of ZnO-nc and Eu³⁺ ions embedded in a SiO₂ matrix using the low-cost sol-gel technique. The time-resolved photoluminescence (TRPL) measurements [...] Read more.

In this work, we study the energy transfer mechanism from ZnO nanocrystals (ZnO-nc) to Eu³⁺ ions by fabricating thin-film samples of ZnO-nc and Eu³⁺ ions embedded in a SiO₂ matrix using the low-cost sol-gel technique. The time-resolved photoluminescence (TRPL) measurements from the samples were analyzed to understand the contribution of energy transfer from the various ZnO-nc emission centers to Eu³⁺ ions. The decay time obtained from the TRPL measurements was used to calculate the energy transfer efficiencies from the ZnO-nc emission centers, and these results were compared with the energy transfer efficiencies calculated from steady-state photoluminescence emission results. The results in this work show that high transfer efficiencies from the excitonic and Zn defect emission centers is mostly due to the energy transfer from ZnO-nc to Eu³⁺ ions which results in the radiative emission from the Eu³⁺ ions at 614 nm, while the energy transfer from the oxygen defect emissions is most probably due to the energy transfer from ZnO-nc to the new defects created due to the incorporation of the Eu³⁺ ions. Full article

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14 pages, 2064 KiB

Open AccessArticle

Longitudinal Mechano-Sorptive Creep Behavior of Chinese Fir in Tension during Moisture Adsorption Processes

by Hui Peng^1,2, Jianxiong Lu¹, Jiali Jiang^1,* and Jinzhen Cao²

¹ State Key Laboratory of Tree Genetics and Breeding, Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China

² College of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China

Materials 2017, 10(8), 931; https://doi.org/10.3390/ma10080931 - 10 Aug 2017

Cited by 9 | Viewed by 3867

Abstract

To provide comprehensive data on creep behaviors at relative humidity (RH) isohume conditions and find the basic characteristics of mechano-sorptive (MS) creep (MSC), the tensile creep behaviors, “viscoelastic creep (VEC)” at equilibrium moisture content and MSC during adsorption process, were performed on Chinese [...] Read more.

To provide comprehensive data on creep behaviors at relative humidity (RH) isohume conditions and find the basic characteristics of mechano-sorptive (MS) creep (MSC), the tensile creep behaviors, “viscoelastic creep (VEC)” at equilibrium moisture content and MSC during adsorption process, were performed on Chinese fir in the longitudinal direction under 20%, 40%, 60% and 80% RH (25 °C) and at 1, 1.3, and 1.6 MPa, respectively. The free swelling behavior was also measured, where the climate conditions corresponded with MSC tests. Based on the databases of free swelling, VEC, and MSC, the existence of MS effect was examined, and the application of the rheological model under the assumption of partitioned strain was investigated. The results revealed that both VEC and MSC increased with magnitude of applied stress, and the increasing RH level. Under all RH isohume conditions, the total strain of MSC was greater than that of VEC. The influence of RH level on VEC was attributed to the water plasticization effect, whereas that on MSC was presumed to be the effect of water plasticization and unstable state in the wood cell wall. In addition, the RH level promoted the relaxation behavior in MSC, while it slightly affected the relaxation behavior in VEC. In the future, the rheological model could consider the link between load configuration and the anatomic structural feature of wood. Full article

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16 pages, 5227 KiB

Open AccessArticle

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

by Yuxin Wang^1,2

, Guang Cheng^3,*

, See Leng Tay², Yunxia Guo¹, Xin Sun⁴ and Wei Gao²

¹ School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, Jiangsu, China

² Department of Chemical & Materials Engineering, the University of Auckland, PB 92019, Auckland 1142, New Zealand

³ Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA

⁴ Energy and Transportation Science Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37830, USA

Materials 2017, 10(8), 932; https://doi.org/10.3390/ma10080932 - 10 Aug 2017

Cited by 12 | Viewed by 5352

Abstract

In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid [...] Read more.

In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomic percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts. Full article

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12 pages, 3662 KiB

Open AccessArticle

Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses

by Stephan Gräf^*

, Clemens Kunz

and Frank A. Müller

Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena, Germany

Materials 2017, 10(8), 933; https://doi.org/10.3390/ma10080933 - 10 Aug 2017

Cited by 70 | Viewed by 9019

Abstract

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength [...] Read more.

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications. Full article

(This article belongs to the Special Issue Nanoscale Structure Resulting from Ultrafast Laser Interaction with Matter)

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13 pages, 8271 KiB

Open AccessArticle

Fabrication and Characterization of 3D-Printed Highly-Porous 3D LiFePO₄ Electrodes by Low Temperature Direct Writing Process

by Changyong Liu¹

, Xingxing Cheng¹, Bohan Li², Zhangwei Chen¹, Shengli Mi^2,* and Changshi Lao^1,*

¹ Additive Manufacturing Research Institute, College of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China

² Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Beijing 518000, China

Materials 2017, 10(8), 934; https://doi.org/10.3390/ma10080934 - 10 Aug 2017

Cited by 74 | Viewed by 10093

Abstract

LiFePO₄ (LFP) is a promising cathode material for lithium-ion batteries. In this study, low temperature direct writing (LTDW)-based 3D printing was used to fabricate three-dimensional (3D) LFP electrodes for the first time. LFP inks were deposited into a low temperature chamber and [...] Read more.

LiFePO₄ (LFP) is a promising cathode material for lithium-ion batteries. In this study, low temperature direct writing (LTDW)-based 3D printing was used to fabricate three-dimensional (3D) LFP electrodes for the first time. LFP inks were deposited into a low temperature chamber and solidified to maintain the shape and mechanical integrity of the printed features. The printed LFP electrodes were then freeze-dried to remove the solvents so that highly-porous architectures in the electrodes were obtained. LFP inks capable of freezing at low temperature was developed by adding 1,4 dioxane as a freezing agent. The rheological behavior of the prepared LFP inks was measured and appropriate compositions and ratios were selected. A LTDW machine was developed to print the electrodes. The printing parameters were optimized and the printing accuracy was characterized. Results showed that LTDW can effectively maintain the shape and mechanical integrity during the printing process. The microstructure, pore size and distribution of the printed LFP electrodes was characterized. In comparison with conventional room temperature direct ink writing process, improved pore volume and porosity can be obtained using the LTDW process. The electrochemical performance of LTDW-fabricated LFP electrodes and conventional roller-coated electrodes were conducted and compared. Results showed that the porous structure that existed in the printed electrodes can greatly improve the rate performance of LFP electrodes. Full article

(This article belongs to the Section Energy Materials)

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10 pages, 8055 KiB

Open AccessCommunication

Influence of Polymer-Clay Interfacial Interactions on the Ignition Time of Polymer/Clay Nanocomposites

by Indraneel S. Zope¹, Aravind Dasari^1,*

and Zhong-Zhen Yu²

¹ School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore

² State Key Laboratory of Organic-Inorganic Composites, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China

Materials 2017, 10(8), 935; https://doi.org/10.3390/ma10080935 - 11 Aug 2017

Cited by 11 | Viewed by 5857

Abstract

Metal ions present on smectite clay (montmorillonite) platelets have preferential reactivity towards peroxy/alkoxy groups during polyamide 6 (PA6) thermal decomposition. This changes the decomposition pathway and negatively affects the ignition response of PA6. To restrict these interfacial interactions, high-temperature-resistant polymers such as polyetherimide [...] Read more.

Metal ions present on smectite clay (montmorillonite) platelets have preferential reactivity towards peroxy/alkoxy groups during polyamide 6 (PA6) thermal decomposition. This changes the decomposition pathway and negatively affects the ignition response of PA6. To restrict these interfacial interactions, high-temperature-resistant polymers such as polyetherimide (PEI) and polyimide (PI) were used to coat clay layers. PEI was deposited on clay by solution-precipitation, whereas PI was deposited through a solution-imidization-precipitation technique before melt blending with PA6. The absence of polymer-clay interfacial interactions has resulted in a similar time-to-ignition of PA6/PEI-clay (133 s) and PA6/PI-clay (139 s) composites as neat PA6 (140 s). On the contrary, PA6 with conventional ammonium-based surfactant modified clay has showed a huge drop in time-to-ignition (81 s), as expected. The experimental evidences provided herein reveal the role of the catalytic activity of clay during the early stages of polymer decomposition. Full article

(This article belongs to the Section Advanced Composites)

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18 pages, 10025 KiB

Open AccessArticle

Porous Graphene Oxide Prepared on Nickel Foam by Electrophoretic Deposition and Thermal Reduction as High-Performance Supercapacitor Electrodes

by Yunhe Xu, Jun Li^*

and Wenxin Huang

School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China

Materials 2017, 10(8), 936; https://doi.org/10.3390/ma10080936 - 11 Aug 2017

Cited by 54 | Viewed by 9251

Abstract

A simple electrophoretic deposition method was developed to prepare graphene oxide (GO) films on the frameworks of nickel foam without any conductive agents and polymer binders. Then, GO was transformed into thermally-reduced graphene oxide (RGO) at an appropriate temperature. The effects of deposition [...] Read more.

A simple electrophoretic deposition method was developed to prepare graphene oxide (GO) films on the frameworks of nickel foam without any conductive agents and polymer binders. Then, GO was transformed into thermally-reduced graphene oxide (RGO) at an appropriate temperature. The effects of deposition voltage and thermal reduction temperature on the electrochemical properties of RGO were investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge. The appropriate combination of deposition voltage and thermal reduction temperature was established. Moreover, scanning electron microscopy, thermal gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffractometry were applied to validate the results, which showed that the highest specific capacitance of RGO was obtained when the deposition voltage was 60 V and the thermal reduction temperature was 300 °C. The specific capacitance values calculated by CV and galvanostatic charge/discharge were 139 F·g⁻¹ (0.005 V·s⁻¹) and 151 F·g⁻¹ (1 A·g⁻¹), respectively. The specific capacitance of RGO maintained 55% and 66% of the initial value when the scan rate and the current density were increased up to 0.3 V·s⁻¹ and 10 A·g⁻¹, respectively. RGO also displayed an excellent cycling stability by maintaining 98% of the initial specific capacitance after 500 cycles. Full article

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12 pages, 4269 KiB

Open AccessArticle

Fabrication and Characterization of Magnesium Ferrite-Based PCL/Aloe Vera Nanofibers

by Zanshe Thompson^1,2, Shekh Rahman^1,2, Sergey Yarmolenko^2,3, Jagannathan Sankar^2,3, Dhananjay Kumar^2,3 and Narayan Bhattarai^1,2,*

¹ Department of Chemical, Biological and Bioengineering, North Carolina A&T State University, Greensboro, NC 27411, USA

² NSF Engineering Research Center for Revolutionizing Metallic Biomaterials, Greensboro, NC 27411, USA

³ Department of Mechanical Engineering, North Carolina A&T State University, Greensboro, NC 27411, USA

Materials 2017, 10(8), 937; https://doi.org/10.3390/ma10080937 - 11 Aug 2017

Cited by 29 | Viewed by 6542

Abstract

Composite nanofibers of biopolymers and inorganic materials have been widely explored as tissue engineering scaffolds because of their superior structural, mechanical and biological properties. In this study, magnesium ferrite (Mg-ferrite) based composite nanofibers were synthesized using an electrospinning technique. Mg-ferrite nanoparticles were first [...] Read more.

Composite nanofibers of biopolymers and inorganic materials have been widely explored as tissue engineering scaffolds because of their superior structural, mechanical and biological properties. In this study, magnesium ferrite (Mg-ferrite) based composite nanofibers were synthesized using an electrospinning technique. Mg-ferrite nanoparticles were first synthesized using the reverse micelle method, and then blended in a mixture of polycaprolactone (PCL), a synthetic polymer, and Aloe vera, a natural polymer, to create magnetic nanofibers by electrospinning. The morphology, structural and magnetic properties, and cellular compatibility of the magnetic nanofibers were analyzed. Mg-ferrite/PCL/Aloe vera nanofibers showed good uniformity in fiber morphology, retained their structural integrity, and displayed magnetic strength. Experimental results, using cell viability assay and scanning electron microscopy imaging showed that magnetic nanofibers supported 3T3 cell viability. We believe that the new composite nanofibrous membranes developed in this study have the ability to mimic the physical structure and function of tissue extracellular matrix, as well as provide the magnetic and soluble metal ion attributes in the scaffolds with enhanced cell attachment, and thus improve tissue regeneration. Full article

(This article belongs to the Special Issue Polymeric Materials for Medical Applications)

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11 pages, 6670 KiB

Open AccessArticle

Comparison of Medium Manganese Steel and Q345 Steel on Corrosion Behavior in a 3.5 wt % NaCl Solution

by Guanqiao Su and Xiuhua Gao^*

The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China

Materials 2017, 10(8), 938; https://doi.org/10.3390/ma10080938 - 11 Aug 2017

Cited by 18 | Viewed by 5300

Abstract

A cyclic wet/dry accelerated corrosion test was used to compare the corrosion behavior of medium-Mn steel and Q345 steel. In terms of scanning electron microscope (SEM), using X-ray diffraction (XRD), electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), and analysis of the corrosion [...] Read more.

A cyclic wet/dry accelerated corrosion test was used to compare the corrosion behavior of medium-Mn steel and Q345 steel. In terms of scanning electron microscope (SEM), using X-ray diffraction (XRD), electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), and analysis of the corrosion process, the results showed that the medium-Mn steel did not exhibit higher corrosion resistance than Q345 steel due to the greater content of Mn-rich compounds in the rust layer. Moreover, the effect of a small amount of anti-corrosion elements in medium-manganese steel can regulate the corrosion rate. The conceptual model of the corrosion process of the medium-Mn steel in a 3.5 wt % NaCl solution is proposed. Full article

(This article belongs to the Section Advanced Materials Characterization)

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13 pages, 34053 KiB

Open AccessArticle

The Dry Sliding Wear Properties of Nano-Sized TiC_p/Al-Cu Composites at Elevated Temperatures

by Wei-Si Tian^1,2, Qing-Long Zhao^1,*

, Chuan-Jiang Zhao¹, Feng Qiu^1,2

and Qi-Chuan Jiang^1,2,*

¹ Key Laboratory of Automobile Materials, Ministry of Education, Department of Materials Science and Engineering, Jilin University, No. 5988 Renmin Street, Changchun 130025, China

² State Key Laboratory of Automotive Simulation and Control, Jilin University, No. 5988 Renmin Street, Changchun 130025, China

Materials 2017, 10(8), 939; https://doi.org/10.3390/ma10080939 - 11 Aug 2017

Cited by 24 | Viewed by 4559

Abstract

Nano-sized ceramic particle reinforced aluminum composites exhibit excellent room-temperature mechanical properties. However, there is limited research on the dry sliding wear behavior of those composites at elevated temperatures, which should be one of the major concerns on elevated temperature applications. Here the Al-Cu [...] Read more.

Nano-sized ceramic particle reinforced aluminum composites exhibit excellent room-temperature mechanical properties. However, there is limited research on the dry sliding wear behavior of those composites at elevated temperatures, which should be one of the major concerns on elevated temperature applications. Here the Al-Cu composites reinforced with nano-sized TiC_p were fabricated. The dry sliding wear behaviors of the nano-sized TiC_p/Al-Cu composites at various temperatures (140–220 °C) and loads (10–40 N) with different TiC_p contents were studied, and the results showed that the nanocomposites exhibited superior wear resistance. For instance, the relative wear resistance of the 0.5 wt.% nano-sized TiC_p/Al-Cu composite was 83.5% higher than that of the Al-Cu matrix alloy at 180 °C under 20 N, and was also 16.5% higher than that of the 5 wt.% micro-sized TiC_p/Al-Cu composite, attributed to the pronounced Orowan strengthening effect of nanoparticles. The wear rates of the nanocomposites were always lower than those of the Al-Cu matrix alloy under the same test condition, which increased with the increase in temperature and load and with the decrease in TiC_p content. Full article

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20 pages, 7364 KiB

Open AccessArticle

Thermo-Hydraulic Analysis of Heat Storage Filled with the Ceramic Bricks Dedicated to the Solar Air Heating System

by Magdalena Nemś^*

, Artur Nemś, Jacek Kasperski and Michał Pomorski

Faculty of Mechanical and Power Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland

Materials 2017, 10(8), 940; https://doi.org/10.3390/ma10080940 - 12 Aug 2017

Cited by 20 | Viewed by 7051

Abstract

This article presents the results of a study into a packed bed filled with ceramic bricks. The designed storage installation is supposed to become part of a heating system installed in a single-family house and eventually to be integrated with a concentrated solar [...] Read more.

This article presents the results of a study into a packed bed filled with ceramic bricks. The designed storage installation is supposed to become part of a heating system installed in a single-family house and eventually to be integrated with a concentrated solar collector adapted to climate conditions in Poland. The system’s working medium is air. The investigated temperature ranges and air volume flow rates in the ceramic bed were dictated by the planned integration with a solar air heater. Designing a packed bed of sufficient parameters first required a mathematical model to be constructed and heat exchange to be analyzed, since heat accumulation is a complex process influenced by a number of material properties. The cases discussed in the literature are based on differing assumptions and different formulas are used in calculations. This article offers a comparison of various mathematical models and of system operating parameters obtained from these models. The primary focus is on the Nusselt number. Furthermore, in the article, the thermo-hydraulic efficiency of the investigated packed bed is presented. This part is based on a relationship used in solar air collectors with internal storage. Full article

(This article belongs to the Section Energy Materials)

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14 pages, 3524 KiB

Open AccessArticle

Effects of Adding Polysaccharides and Citric Acid into Sodium Dihydrogen Phosphate Mixing Solution on the Material Properties of Gelatin-Hybridized Calcium-Phosphate Cement

by Keishi Kiminami^1,2, Toshiisa Konishi³, Minori Mizumoto⁴, Kohei Nagata¹, Michiyo Honda¹, Hidetoshi Arimura² and Mamoru Aizawa^1,*

¹ Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki 214-8571, Japan

² GUNZE LIMITED, 1 Zeze, Aono-cho, Ayabe 623-8511, Japan

³ Department of Medical Bioengineering, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan

⁴ Kanagawa Academy of Science and Technology, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan

Materials 2017, 10(8), 941; https://doi.org/10.3390/ma10080941 - 12 Aug 2017

Cited by 10 | Viewed by 4608

Abstract

We have succeeded in improving the material properties of a chelate-setting calcium-phosphate cement (CPC), which is composed of hydroxyapatite (HAp) the surface of which has been modified with inositol hexaphosphate (IP6) by adding α-tricalcium phosphate (α-TCP) powder. In order to create a novel [...] Read more.

We have succeeded in improving the material properties of a chelate-setting calcium-phosphate cement (CPC), which is composed of hydroxyapatite (HAp) the surface of which has been modified with inositol hexaphosphate (IP6) by adding α-tricalcium phosphate (α-TCP) powder. In order to create a novel chelate-setting CPC with sufficient bioresorbability, gelatin particles were added into the IP6-HAp/α-TCP cement system to modify the material properties. The effects of adding polysaccharides (chitosan, chondroitin sulfate, and sodium alginate) into the sodium dihydrogen phosphate mixing solution on the material properties of the gelatin-hybridized CPC were evaluated. The results of mechanical testing revealed that chondroitin sulfate would be the most suitable for fabricating the hybridized CPC with higher compressive strength. Moreover, further addition of an appropriate amount of citric acid could improve the anti-washout capability of the cement paste. In summary, a gelatin-hybridized IP6-HAp/α-TCP cement system prepared with a mixing solution containing chondroitin sulfate and citric acid is expected to be a beneficial CPC, with sufficient bioresorbability and material properties. Full article

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11 pages, 9513 KiB

Open AccessArticle

Electroless Nickel Deposition for Front Side Metallization of Silicon Solar Cells

by Shu Huei Hsieh¹, Jhong Min Hsieh², Wen Jauh Chen^2,* and Chia Chih Chuang³

¹ Department of Materials Science and Engineering, National Formosa University, 64, Wunhua Road, Huwei, Yunlin 632, Taiwan

² Graduate School of Materials Science, National Yunlin University of Science and Technology, 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan

³ Motech Industries Inc., No.2, Dashun 9th Rd., Xinshi Dist., Tainan 741, Taiwan

Materials 2017, 10(8), 942; https://doi.org/10.3390/ma10080942 - 14 Aug 2017

Cited by 11 | Viewed by 7635

Abstract

In this work, nickel thin films were deposited on texture silicon by electroless plated deposition. The electroless-deposited Ni layers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and sheet resistance measurement. [...] Read more.

In this work, nickel thin films were deposited on texture silicon by electroless plated deposition. The electroless-deposited Ni layers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and sheet resistance measurement. The results indicate that the dominant phase was Ni₂Si and NiSi in samples annealed at 300–800 °C. Sheet resistance values were found to correlate well with the surface morphology obtained by SEM and the results of XRD diffraction. The Cu/Ni contact system was used to fabricate solar cells by using two different activating baths. The open circuit voltage (Voc) of the Cu/Ni samples, before and after annealing, was measured under air mass (AM) 1.5 conditions to determine solar cell properties. The results show that open circuit voltage of a solar cell can be enhanced when the activation solution incorporated hydrofluoric acid (HF). This is mainly attributed to the native silicon oxide layer that can be decreased and/or removed by HF with the corresponding reduction of series resistance. Full article

(This article belongs to the Section Energy Materials)

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22 pages, 3991 KiB

Open AccessArticle

Nano-Charged Polypropylene Application: Realistic Perspectives for Enhancing Durability

by Carlo Naddeo^*, Luigi Vertuccio, Giuseppina Barra and Liberata Guadagno^*

Department of Industrial Engineering University of Salerno Via Giovanni Paolo II, 132-84084 Fisciano (SA), Italy

Materials 2017, 10(8), 943; https://doi.org/10.3390/ma10080943 - 14 Aug 2017

Cited by 39 | Viewed by 6114

Abstract

Isotactic polypropylene/multi-walled carbon nanotube (iPP/MWCNTs) films have been exposed to accelerated weathering in a UV device for increasing times. The effect of UV irradiation on the structural and chemical changes has been investigated. The resistance to accelerated photooxidation of (iPP/MWCNTs) films has been [...] Read more.

Isotactic polypropylene/multi-walled carbon nanotube (iPP/MWCNTs) films have been exposed to accelerated weathering in a UV device for increasing times. The effect of UV irradiation on the structural and chemical changes has been investigated. The resistance to accelerated photooxidation of (iPP/MWCNTs) films has been compared to the photooxidation behaviour of unfilled polypropylene films with the same structural organization. The chemical and structural modifications resulting from photooxidation have been followed using infrared spectroscopy, calorimetric and diffractometric analysis. MWCNTs embedded in the polymeric matrix are able to strongly contrast the degradation mechanisms and the structural and morphological rearrangements caused by the UV treatment on the unfilled polymer. MWCNTs determine an induction period (IP) before the increase of the carbonyl and hydroxyl groups. The extent of the IP is strictly correlated to the amount of MWCNTs. The low electrical percolation threshold (EPT) and the electrical conductivity of the nanocomposites, together with their excellent thermal and photooxidative stability, make them promising candidates to fulfill many industrial requirements. Full article

(This article belongs to the Special Issue Improving Performance of Nanocomposite Materials)

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8 pages, 1782 KiB

Open AccessArticle

Effect of Polymer Matrix on the Structure and Electric Properties of Piezoelectric Lead Zirconatetitanate/Polymer Composites

by Rui Li^1,2,*

, Jun Zhou¹, Hujun Liu³ and Jianzhong Pei¹

¹ Highway School, Chang’an University, Xi’an 710064, China

² School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore

³ CCCC Fourth Harbor Engineering Institute Co., LTD., Guangzhou 510000, China

Materials 2017, 10(8), 945; https://doi.org/10.3390/ma10080945 - 14 Aug 2017

Cited by 32 | Viewed by 5275

Abstract

Piezoelectric lead zirconatetitanate (PZT)/polymer composites were prepared by two typical polymer matrixes using the hot-press method. The micromorphology, microstructure, dielectric properties, and piezoelectric properties of the PZT/polymer composites were characterized and investigated. The results showed that when the condition of frequency is 10 [...] Read more.

Piezoelectric lead zirconatetitanate (PZT)/polymer composites were prepared by two typical polymer matrixes using the hot-press method. The micromorphology, microstructure, dielectric properties, and piezoelectric properties of the PZT/polymer composites were characterized and investigated. The results showed that when the condition of frequency is 10³ Hz, the dielectric and piezoelectric properties of PZT/poly(vinylidene fluoride) were both better than that of PZT/polyvinyl chloride (PVC). When the volume fraction of PZT was 50%, PZT/PVDF prepared by the hot-press method had better comprehensive electric property. Full article

(This article belongs to the Special Issue Polymers for Film Capacitors)

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14 pages, 3863 KiB

Open AccessArticle

Exploration of the Structural, Electronic and Tunable Magnetic Properties of Cu₄M (M = Sc-Ni) Clusters

by Dong Die^1,*, Ben-Xia Zheng¹, Xiao-Yu Kuang^2,*, Zheng-Quan Zhao¹, Jian-Jun Guo¹ and Quan Du¹

¹ School of Science, Xihua University, Chengdu 610039, China

² Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China

Materials 2017, 10(8), 946; https://doi.org/10.3390/ma10080946 - 15 Aug 2017

Cited by 6 | Viewed by 4583

Abstract

The structural, electronic and magnetic properties of Cu₄M (M = Sc-Ni) clusters have been studied by using density functional theory, together with an unbiased CALYPSO structure searching method. Geometry optimizations indicate that M atoms in the ground state Cu₄M [...] Read more.

The structural, electronic and magnetic properties of Cu₄M (M = Sc-Ni) clusters have been studied by using density functional theory, together with an unbiased CALYPSO structure searching method. Geometry optimizations indicate that M atoms in the ground state Cu₄M clusters favor the most highly coordinated position. The geometry of Cu₄M clusters is similar to that of the Cu₅ cluster. The infrared spectra, Raman spectra and photoelectron spectra are predicted and can be used to identify the ground state in the future. The relative stability and chemical activity are investigated by means of the averaged binding energy, dissociation energy and energy level gap. It is found that the dopant atoms except for Cr and Mn can enhance the stability of the host cluster. The chemical activity of all Cu₄M clusters is lower than that of Cu₅ cluster whose energy level gap is in agreement with available experimental finding. The magnetism calculations show that the total magnetic moment of Cu₄M cluster mainly come from M atom and vary from 1 to 5 μ_B by substituting a Cu atom in Cu₅ cluster with different transition-metal atoms. Full article

(This article belongs to the Section Advanced Materials Characterization)

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13 pages, 1896 KiB

Open AccessArticle

Modeling the Non-Equilibrium Process of the Chemical Adsorption of Ammonia on GaN(0001) Reconstructed Surfaces Based on Steepest-Entropy-Ascent Quantum Thermodynamics

by Akira Kusaba^1,*, Guanchen Li^2,3

, Michael R. Von Spakovsky³, Yoshihiro Kangawa^1,4,5 and Koichi Kakimoto^1,4

¹ Department of Aeronautics and Astronautics, Kyushu University, Fukuoka 819-0395, Japan

² Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK

³ Center for Energy Systems Research (CESR), Mechanical Engineering Department, Virginia Tech, Blacksburg, VA 24061, USA

⁴ Research Institute for Applied Mechanics (RIAM), Kyushu University, Fukuoka 816-8580, Japan

⁵ Center for Integrated Research of Future Electronics (CIRFE), Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Nagoya 464-8601, Japan

Materials 2017, 10(8), 948; https://doi.org/10.3390/ma10080948 - 15 Aug 2017

Cited by 14 | Viewed by 6076

Abstract

Clearly understanding elementary growth processes that depend on surface reconstruction is essential to controlling vapor-phase epitaxy more precisely. In this study, ammonia chemical adsorption on GaN(0001) reconstructed surfaces under metalorganic vapor phase epitaxy (MOVPE) conditions (3Ga-H and N_ad-H + Ga-H on [...] Read more.

Clearly understanding elementary growth processes that depend on surface reconstruction is essential to controlling vapor-phase epitaxy more precisely. In this study, ammonia chemical adsorption on GaN(0001) reconstructed surfaces under metalorganic vapor phase epitaxy (MOVPE) conditions (3Ga-H and N_ad-H + Ga-H on a 2 × 2 unit cell) is investigated using steepest-entropy-ascent quantum thermodynamics (SEAQT). SEAQT is a thermodynamic-ensemble based, first-principles framework that can predict the behavior of non-equilibrium processes, even those far from equilibrium where the state evolution is a combination of reversible and irreversible dynamics. SEAQT is an ideal choice to handle this problem on a first-principles basis since the chemical adsorption process starts from a highly non-equilibrium state. A result of the analysis shows that the probability of adsorption on 3Ga-H is significantly higher than that on N_ad-H + Ga-H. Additionally, the growth temperature dependence of these adsorption probabilities and the temperature increase due to the heat of reaction is determined. The non-equilibrium thermodynamic modeling applied can lead to better control of the MOVPE process through the selection of preferable reconstructed surfaces. The modeling also demonstrates the efficacy of DFT-SEAQT coupling for determining detailed non-equilibrium process characteristics with a much smaller computational burden than would be entailed with mechanics-based, microscopic-mesoscopic approaches. Full article

(This article belongs to the Special Issue Light Emitting Diodes and Laser Diodes: Materials and Devices)

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14 pages, 3670 KiB

Open AccessArticle

Study of CeO₂ Modified AlNi Mixed Pillared Clays Supported Palladium Catalysts for Benzene Adsorption/Desorption-Catalytic Combustion

by Jingrong Li, Shufeng Zuo^*

, Peng Yang and Chenze Qi

Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University, Shaoxing 312000, China

Materials 2017, 10(8), 949; https://doi.org/10.3390/ma10080949 - 15 Aug 2017

Cited by 15 | Viewed by 5565

Abstract

A new functional AlNi-pillared clays (AlNi-PILC) with a large surface area and pore volume was synthesized. The performance of adsorption/desorption-catalytic combustion over CeO_2-modified Pd/AlNi-PILC catalysts was also studied. The results showed that the d₀₀₁-value and specific surface area ( [...] Read more.

A new functional AlNi-pillared clays (AlNi-PILC) with a large surface area and pore volume was synthesized. The performance of adsorption/desorption-catalytic combustion over CeO_2-modified Pd/AlNi-PILC catalysts was also studied. The results showed that the d₀₀₁-value and specific surface area (S_BET) of AlNi-PILC reached 2.11 nm and 374.8 m²/g, respectively. The large S_BET and the d₀₀₁-value improved the high capacity for benzene adsorption. Also, the strong interaction between PdCe mixed oxides and AlNi-PILC led to the high dispersion of PdO and CeO₂ on the support, which was responsible for the high catalytic performance. Especially, 0.2% Pd/12.5% Ce/AlNi-PILC presented high performance for benzene combustion at 240 °C and high CO₂ selectivity. Also, the combustion temperatures were lower compared to the desorption temperatures, which demonstrated that it could accomplish benzene combustion during the desorption process. Furthermore, its activity did not decrease after continuous reaction for 1000 h in dry air, and it also displayed good resistance to water and the chlorinated compound, making it a promising catalytic material for the elimination of volatile organic compounds. Full article

(This article belongs to the Special Issue Advances in Pillared Clays and Similar Materials: Synthesis, Characterization and Applications)

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12 pages, 3665 KiB

Open AccessArticle

The Degree of Temporal Synchronization of the Pulse Oscillations from a Gain-Switched Multimode Semiconductor Laser

by Kenji Wada^*, Naoaki Kitagawa and Tetsuya Matsuyama

Department of Physics and Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan

Materials 2017, 10(8), 950; https://doi.org/10.3390/ma10080950 - 15 Aug 2017

Cited by 5 | Viewed by 6769

Abstract

Langevin noise leads to inhibition of the temporal synchronization of the pulse oscillations from a gain-switched multimode semiconductor laser, resulting in the power reduction in optical beat detection. In this paper, the degree of the temporal synchronization of the pulse oscillations was examined [...] Read more.

Langevin noise leads to inhibition of the temporal synchronization of the pulse oscillations from a gain-switched multimode semiconductor laser, resulting in the power reduction in optical beat detection. In this paper, the degree of the temporal synchronization of the pulse oscillations was examined by numerically estimating the output energy in THz time-domain spectroscopy (THz-TDS) using multimode semiconductor laser rate equations that include Langevin noise. The degree was estimated to be 95.5% from the ratio of the averaged THz-TDS output energy for the case where Langevin noise was included to that for when Langevin noise was excluded. Therefore, a gain-switched multimode semiconductor laser can be regarded as equivalent to optical pulses oscillating simultaneously in all modes in actual applications including optical beat detection. Full article

(This article belongs to the Special Issue Light Emitting Diodes and Laser Diodes: Materials and Devices)

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21 pages, 7055 KiB

Open AccessArticle

A Continuum Damage Mechanics Model for the Static and Cyclic Fatigue of Cellular Composites

by Sergej Diel¹

and Otto Huber^2,*

¹ Audi AG, D-85045 Ingolstadt, Germany

² Competence Center for Lightweight Design (LLK), University of Applied Sciences Landshut, D-84036 Landshut, Germany

Materials 2017, 10(8), 951; https://doi.org/10.3390/ma10080951 - 15 Aug 2017

Cited by 11 | Viewed by 7223

Abstract

The fatigue behavior of a cellular composite with an epoxy matrix and glass foam granules is analyzed and modeled by means of continuum damage mechanics. The investigated cellular composite is a particular type of composite foam, and is very similar to syntactic foams. [...] Read more.

The fatigue behavior of a cellular composite with an epoxy matrix and glass foam granules is analyzed and modeled by means of continuum damage mechanics. The investigated cellular composite is a particular type of composite foam, and is very similar to syntactic foams. In contrast to conventional syntactic foams constituted by hollow spherical particles (balloons), cellular glass, mineral, or metal place holders are combined with the matrix material (metal or polymer) in the case of cellular composites. A microstructural investigation of the damage behavior is performed using scanning electron microscopy. For the modeling of the fatigue behavior, the damage is separated into pure static and pure cyclic damage and described in terms of the stiffness loss of the material using damage models for cyclic and creep damage. Both models incorporate nonlinear accumulation and interaction of damage. A cycle jumping procedure is developed, which allows for a fast and accurate calculation of the damage evolution for constant load frequencies. The damage model is applied to examine the mean stress effect for cyclic fatigue and to investigate the frequency effect and the influence of the signal form in the case of static and cyclic damage interaction. The calculated lifetimes are in very good agreement with experimental results. Full article

(This article belongs to the Special Issue Syntactic Foams: Microstructural Characterisation and Effective Properties)

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14 pages, 1269 KiB

Open AccessArticle

Antibacterial Properties of Nonwoven Wound Dressings Coated with Manuka Honey or Methylglyoxal

by Sophie E. L. Bulman^*, Giuseppe Tronci

, Parikshit Goswami

, Chris Carr and Stephen J. Russell

Clothworkers’ Centre for Textile Materials Innovation for Healthcare (CCTMIH), School of Design, University of Leeds, Leeds LS2 9JT, West Yorkshire, UK

Materials 2017, 10(8), 954; https://doi.org/10.3390/ma10080954 - 16 Aug 2017

Cited by 45 | Viewed by 7837

Abstract

Manuka honey (MH) is used as an antibacterial agent in bioactive wound dressings via direct impregnation onto a suitable substrate. MH provides unique antibacterial activity when compared with conventional honeys, owing partly to one of its constituents, methylglyoxal (MGO). Aiming to investigate an [...] Read more.

Manuka honey (MH) is used as an antibacterial agent in bioactive wound dressings via direct impregnation onto a suitable substrate. MH provides unique antibacterial activity when compared with conventional honeys, owing partly to one of its constituents, methylglyoxal (MGO). Aiming to investigate an antibiotic-free antimicrobial strategy, we studied the antibacterial activity of both MH and MGO (at equivalent MGO concentrations) when applied as a physical coating to a nonwoven fabric wound dressing. When physically coated on to a cellulosic hydroentangled nonwoven fabric, it was found that concentrations of 0.0054 mg cm⁻² of MGO in the form of MH and MGO were sufficient to achieve a 100 colony forming unit % bacteria reduction against gram-positive Staphylococcus aureus and gram-negative Klebsiella pneumoniae, based on BS EN ISO 20743:2007. A 3- to 20-fold increase in MGO concentration (0.0170–0.1 mg cm⁻²) was required to facilitate a good antibacterial effect (based on BS EN ISO 20645:2004) in terms of zone of inhibition and lack of growth under the sample. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was also assessed for MGO in liquid form against three prevalent wound and healthcare-associated pathogens, i.e., Staphylococcus aureus, gram-negative Pseudomonas aeruginosa and gram-positive Enterococcus faecalis. Other than the case of MGO-containing fabrics, solutions with much higher MGO concentrations (128 mg L⁻¹–1024 mg L⁻¹) were required to provide either a bacteriostatic or bactericidal effect. The results presented in this study therefore demonstrate the relevance of an MGO-based coating as an environmentally friendly strategy for the design of functional dressings with antibiotic-free antimicrobial chemistries. Full article

(This article belongs to the Section Biomaterials)

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13 pages, 3012 KiB

Open AccessArticle

Pt-Co Alloys-Loaded Cubic SiC Electrode with Improved Photoelectrocatalysis Property

by Dan Liu¹, Tao Yang¹, Junhong Chen², Kuo-Chih Chou¹ and Xinmei Hou^1,*

¹ State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China

² School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

Materials 2017, 10(8), 955; https://doi.org/10.3390/ma10080955 - 16 Aug 2017

Cited by 11 | Viewed by 6273

Abstract

A novel composite photocatalyst was synthesized by loading 5 wt % of platinum cobalt alloy on 3C-SiC nanowires and powder (Pt-Co-SiC) respectively via a simple polyol reduction method. Pt-Co-SiC were comprehensively characterized by SEM, HRTEM, XRD, PL, and XPS. The results indicated that [...] Read more.

A novel composite photocatalyst was synthesized by loading 5 wt % of platinum cobalt alloy on 3C-SiC nanowires and powder (Pt-Co-SiC) respectively via a simple polyol reduction method. Pt-Co-SiC were comprehensively characterized by SEM, HRTEM, XRD, PL, and XPS. The results indicated that Pt-Co nanoparticles in the size of 2–5 nm were dispersed homogeneously in the SiC nanowires and powders. The photocurrent response of the Pt-Co-SiC increased remarkably with increasing Pt content and the best performance was observed with the sample of Pt₃Co-SiC. Especially, the Pt₃Co-SiC nanowires photoelectrode exhibited improved cathodic current density (0.14 mA·cm⁻²) under the simulated sunlight, which was about 10 times higher than the Pt₃Co-SiC powders. The H₂ production rate for the Pt₃Co-SiC nanowires is 30 times more than that of the pure SiC nanowires. The enhancement of the Pt-Co-SiC properties could be ascribed to the fact that more visible light was harvested and the photogenerated electron and the interfacial electron transfered more easily. Full article

(This article belongs to the Section Energy Materials)

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13 pages, 13491 KiB

Open AccessArticle

Enhanced Corrosion Resistance of Carbon Steel in Hydrochloric Acid Solution by Eriobotrya Japonica Thunb. Leaf Extract: Electrochemical Study

by Wenjing Yang^1,*, Qihui Wang¹, Ke Xu¹, Yanjun Yin¹, Hebin Bao¹, Xueming Li^1,*, Lidan Niu² and Shiqi Chen²

¹ College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China

² Chongqing Institute for food and Drug Control, Chongqing 401121, China

Materials 2017, 10(8), 956; https://doi.org/10.3390/ma10080956 - 16 Aug 2017

Cited by 28 | Viewed by 6612

Abstract

The biodegradable inhibitors, which could effectively reduce the rate of corrosion of carbon steel, were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The mixed-type inhibitors extracted from Eriobotrya japonica Thunb. leaf exhibited excellent inhibition performance, and the inhibition efficiency for carbon [...] Read more.

The biodegradable inhibitors, which could effectively reduce the rate of corrosion of carbon steel, were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The mixed-type inhibitors extracted from Eriobotrya japonica Thunb. leaf exhibited excellent inhibition performance, and the inhibition efficiency for carbon steel reached 90.0% at 298 K in hydrochloric acid. Moreover, the adsorption mechanism of the inhibitors on a carbon steel surface is described by the Langmuir adsorption isotherm. Simultaneously, the corrosion morphology of the carbon steel and the inhibitor structure were analyzed by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. Full article

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12 pages, 8673 KiB

Open AccessArticle

Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide

by Zhaokun Li, Shixin Song, Xuanchen Zhao, Xue Lv^* and Shulin Sun^*

Engineering Research Center of Synthetic Resin and Special Fiber, Ministry of Education, Changchun University of Technology, Changchun 130012, China

Materials 2017, 10(8), 957; https://doi.org/10.3390/ma10080957 - 16 Aug 2017

Cited by 14 | Viewed by 5631

Abstract

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such [...] Read more.

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such as grafting degree, shell thickness, internal and external grafting) of the core-shell particles. The introduction of TDDM decreased the grafting degree, shell thickness and the T_g of the core phase. When the content of TDDM was lower than 1.15%, the RCS particles dispersed in the PLA matrix uniformly—otherwise, agglomeration took place. The addition of RCS particles induced a higher cold crystallization temperature and a lower melting temperature of PLA which indicated the decreased crystallization ability of PLA. Dynamic mechanical analysis (DMA) results proved the good miscibility between PLA and the RCS particles and the increase of TDDM in RCS induced higher storage modulus of PLA/RCS blends. Suitable TDDM addition improved the toughening ability of RCS particles for PLA. In the present research, PLA/RCS-T4 (RCS-T4: the reactive core-shell particles with 0.76 wt % TDDM addition) blends displayed much better impact strength than other blends due to the easier cavitation/debonding ability and good dispersion morphology of the RCS-T4 particles. When the RCS-T4 content was 25 wt %, the impact strength of PLA/RCS-T4 blend reached 768 J/m, which was more than 25 times that of the pure PLA. Full article

(This article belongs to the Special Issue The Brittle Failure of Different Materials)

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20 pages, 10023 KiB

Open AccessArticle

Production of Synthetic Phosphoanhydrite and Its Use as a Binder in Self-Leveling Underlayments (SLU)

by Cecília Ogliari Schaefer¹, Malik Cheriaf² and Janaíde Cavalcante Rocha^2,*

¹ Post-Graduate Program in Civil Engineering, Federal University of Santa Catarina, CEP 88040-900 Florianópolis, SC, Brazil

² Department of Civil Engineering, Federal University of Santa Catarina, CEP 88040-900 Florianópolis, SC, Brazil

Materials 2017, 10(8), 958; https://doi.org/10.3390/ma10080958 - 17 Aug 2017

Cited by 28 | Viewed by 5284

Abstract

An experimental study was conducted to investigate the potential use of phosphogypsum (PG) to produce self-leveling underlayments. The study was designed in two stages. Initially a phosphoanhydrite (PA) was produced by heating phosphogypsum at temperatures of 350 °C, 450 °C, 550 °C, and [...] Read more.

An experimental study was conducted to investigate the potential use of phosphogypsum (PG) to produce self-leveling underlayments. The study was designed in two stages. Initially a phosphoanhydrite (PA) was produced by heating phosphogypsum at temperatures of 350 °C, 450 °C, 550 °C, and 650 °C. Two periods of heating were applied (2 and 4 h). The formation of anhydrite was determined by thermogravimetric analysis (DTA-TG) and confirmed by X-ray diffraction (XRD). The results show that anhydrite II was obtained at temperatures above 450 °C, and at higher calcination temperatures the PA solubility was lower. In the second stage of this research, the PA was used in self-leveling underlayments as the main binder in the ternary system comprised of calcium sulfate, calcium aluminate cement, and Portland cement. Self-leveling mortar screeds produced using PA (550 °C/4 h) and PA (650 °C/4 h) showed the best performance in terms of mechanical strength and no degradation was observed after immersion and immersion-drying tests. The formation of ettringite, identified by scanning electron microscopy (SEM), may have contributed to these results. Morphological changes were studied using the scanning electron microscopy (SEM) technique. Full article

(This article belongs to the Section Advanced Materials Characterization)

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10 pages, 2388 KiB

Open AccessArticle

Insights on the Optical Properties of Poly(3,4-Ethylenedioxythiophene):Poly(styrenesulfonate) Formulations by Optical Metrology

by Argiris Laskarakis^*, Varvara Karagkiozaki, Despoina Georgiou, Christoforos Gravalidis and Stergios Logothetidis

Nanotechnology Lab LTFN, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece

Materials 2017, 10(8), 959; https://doi.org/10.3390/ma10080959 - 17 Aug 2017

Cited by 13 | Viewed by 4934

Abstract

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is among the most widely used polymers that are used as printed transparent electrodes for flexible Organic Electronic (OE) devices, such as Organic Photovoltaics (OPVs). The understanding of their optical properties and the correlation of the optical properties with their electronic [...] Read more.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is among the most widely used polymers that are used as printed transparent electrodes for flexible Organic Electronic (OE) devices, such as Organic Photovoltaics (OPVs). The understanding of their optical properties and the correlation of the optical properties with their electronic properties and metallic-like behavior can lead to the optimization of their functionality as transparent electrodes in multilayer OE device architectures. In this work, we study the optical properties of different PEDOT:PSS formulations by non-destructive Spectroscopic Ellipsometry (SE), from the infrared to the far ultraviolet spectral regions. The optical response of PEDOT:PSS includes an intense optical absorption originated from the conductive part (PEDOT) at lower photon energies, whereas the electronic transition energies of the non-conductive PSS part have been measured at higher photon energies. Based on the different PEDOT:PSS formulations, the optical investigation revealed significant information on the relative contribution of conductive PEDOT and insulating PSS parts of the PEDOT:PSS formulation in the overall optical response, which can strongly impact the final device functionality and its optical transparency. Full article

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17 pages, 7538 KiB

Open AccessFeature PaperArticle

Ag-Coated Heterostructures of ZnO-TiO₂/Delaminated Montmorillonite as Solar Photocatalysts

by Carolina Belver^1,*

, Mariana Hinojosa², Jorge Bedia¹

, Montserrat Tobajas¹

, Maria Ariadna Alvarez¹, Vicente Rodríguez-González² and Juan Jose Rodriguez¹

¹ Seccion de Ingenieria Quimica, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, E-28049 Madrid, Spain

² Division de Materiales Avanzados, IPICYT (Instituto Potosino de Investigación Científica y Tecnológica), Camino a la Presa San José 2055, C.P. 78216 San Luis Potosí, Mexico

Materials 2017, 10(8), 960; https://doi.org/10.3390/ma10080960 - 17 Aug 2017

Cited by 40 | Viewed by 6480

Abstract

Heterostructures based on ZnO-TiO₂/delaminated montmorillonite coated with Ag have been prepared by sol–gel and photoreduction procedures, varying the Ag and ZnO contents. They have been thoroughly characterized by XRD, WDXRF, UV–Vis, and XPS spectroscopies, and N₂ adsorption, SEM, and TEM. [...] Read more.

Heterostructures based on ZnO-TiO₂/delaminated montmorillonite coated with Ag have been prepared by sol–gel and photoreduction procedures, varying the Ag and ZnO contents. They have been thoroughly characterized by XRD, WDXRF, UV–Vis, and XPS spectroscopies, and N₂ adsorption, SEM, and TEM. In all cases, the montmorillonite was effectively delaminated with the formation of TiO₂ anatase particles anchored on the clay layer’s surface, yielding porous materials with high surface areas. The structural and textural properties of the heterostructures synthesized were unaffected by the ZnO incorporated. The photoreduction led to solids with Ag nanoparticles decorating the surface. These materials were tested as photocatalysts for the degradation of several emerging contaminants with different nitrogen-bearing chemical structures under solar light. The catalysts yielded high rates of disappearance of the starting pollutants and showed quite stable performance upon successive applications. Full article

(This article belongs to the Special Issue Advances in Pillared Clays and Similar Materials: Synthesis, Characterization and Applications)

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11 pages, 3283 KiB

Open AccessArticle

A Novel Approach to Eliminate the Effect of External Stress on Interdiffusivity Measurement

by Weimin Chen¹, Qin Li² and Lijun Zhang^2,*

¹ Institute of Advanced Wear & Corrosion Resistant and Functional Materials, Jinan University, Guangzhou 510632, Guangdong, China

² State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, Hunan, China

Materials 2017, 10(8), 961; https://doi.org/10.3390/ma10080961 - 17 Aug 2017

Cited by 15 | Viewed by 4779

Abstract

In this paper, the interdiffusivities in fcc Co–Ni alloys at 1373 K due to different types of diffusion couple experiments were firstly re-calculated via the unified Wagner method based on the measured composition profiles. Their maximum difference due to different approaches for diffusion [...] Read more.

In this paper, the interdiffusivities in fcc Co–Ni alloys at 1373 K due to different types of diffusion couple experiments were firstly re-calculated via the unified Wagner method based on the measured composition profiles. Their maximum difference due to different approaches for diffusion couple preparation was found to be larger than one order of magnitude. Then, a comprehensive analysis on the effect of different preparation methods was performed. After that, a two-step diffusion couple technique in combination with the pragmatic numerical inverse method was proposed to determine the accurate interdiffusivities by eliminating the effect of external stress. Such a novel approach was successfully applied in the binary fcc Co–Ni alloys for demonstration purposes. Moreover, it is anticipated that such novel approach can be utilized as the standard method for accurate interdiffusivity measurement, and the resultant accurate interdiffusivities in different alloys may serve as a benchmark for the later experimental and theoretical studies. Full article

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18 pages, 6114 KiB

Open AccessFeature PaperArticle

Multiphysics Simulation of Low-Amplitude Acoustic Wave Detection by Piezoelectric Wafer Active Sensors Validated by In-Situ AE-Fatigue Experiment

by Md Yeasin Bhuiyan^*

and Victor Giurgiutiu

Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA

Materials 2017, 10(8), 962; https://doi.org/10.3390/ma10080962 - 17 Aug 2017

Cited by 16 | Viewed by 6372

Abstract

Piezoelectric wafer active sensors (PWAS) are commonly used for detecting Lamb waves for structural health monitoring application. However, in most applications of active sensing, the signals are of high-amplitude and easy to detect. In this article, we have shown a new avenue of [...] Read more.

Piezoelectric wafer active sensors (PWAS) are commonly used for detecting Lamb waves for structural health monitoring application. However, in most applications of active sensing, the signals are of high-amplitude and easy to detect. In this article, we have shown a new avenue of using the PWAS transducer for detecting the low-amplitude fatigue-crack related acoustic emission (AE) signals. Multiphysics finite element (FE) simulations were performed with two PWAS transducers bonded to the structure. Various configurations of the sensors were studied by using the simulations. One PWAS was placed near to the fatigue-crack and the other one was placed at a certain distance from the crack. The simulated AE event was generated at the crack tip. The simulation results showed that both PWAS transducers were capable of sensing the AE signals. To validate the multiphysics simulation results, an in-situ AE-fatigue experiment was performed. Two PWAS transducers were bonded to the thin aerospace test coupon. The fatigue crack was generated in the test coupon which had produced low-amplitude acoustic waves. The low-amplitude fatigue-crack related AE signals were successfully captured by the PWAS transducers. The distance effect on the captured AE signals was also studied. It has been shown that some high-frequency contents of the AE signal have developed as they travel away from the crack. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)

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14 pages, 6609 KiB

Open AccessArticle

Mussel-Inspired Dopamine and Carbon Nanotube Leading to a Biocompatible Self-Rolling Conductive Hydrogel Film

by Junzi Jiang^1,†, Yong Huang^3,†, Yitian Wang², Hui Xu², Malcolm Xing^1,* and Wen Zhong^2,*

¹ Department of Mechanical Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

² Department of Biosystem Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

³ Chongqing Academy of Animal Sciences, Chongqing 402460, China

^† Equally Contributing Authors.

Materials 2017, 10(8), 964; https://doi.org/10.3390/ma10080964 - 18 Aug 2017

Cited by 15 | Viewed by 6769

Abstract

We report a novel self-rolling, conductive, and biocompatible multiwall carbon nanotube (MWCNT)-dopamine-polyethylene glycol (PEG) hydrogel film. The gel can self-fold into a thin tube when it is transferred from a glass slide to an aqueous environment, regardless of the concentrations of the MWCNT. [...] Read more.

We report a novel self-rolling, conductive, and biocompatible multiwall carbon nanotube (MWCNT)-dopamine-polyethylene glycol (PEG) hydrogel film. The gel can self-fold into a thin tube when it is transferred from a glass slide to an aqueous environment, regardless of the concentrations of the MWCNT. The film presents a highly organized pattern, which results from the self-assembly of hydrophilic dopamine and hydrophobic carbon nanotubes. By exploring the biomedical potential, we found that MWCNT-included rolled film is nontoxic and can promote cell growth. For further functional verification by qPCR (quantitative polymerase chain reaction), bone marrow derived mesenchymal cells present higher levels of osteogenic differentiations in response to a higher concentration of CNTs. The results suggest that the self-rolling, conductive CNT-dopamine-PEG hydrogel could have multiple potentials, including biomedical usage and as a conductive biosensor. Full article

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17 pages, 1941 KiB

Open AccessArticle

Effect of Pullulan Coating on Postharvest Quality and Shelf-Life of Highbush Blueberry (Vaccinium corymbosum L.)

by Karolina Kraśniewska^1,*

, Iwona Ścibisz², Małgorzata Gniewosz¹

, Marta Mitek², Katarzyna Pobiega¹ and Andrzej Cendrowski²

¹ Division of Biotechnology and Microbiology, Department of Biotechnology, Microbiology and Food Evaluation, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159c, 02-776 Warsaw, Poland

² Division of Fruit and Vegetable Technology, Department of Food Technology, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159c, 02-776 Warsaw, Poland

Materials 2017, 10(8), 965; https://doi.org/10.3390/ma10080965 - 18 Aug 2017

Cited by 49 | Viewed by 7429

Abstract

Fruits form an important part of a healthy human diet as they contain many ingredients with proven pro-health effects such as vitamins, phenolic compounds, organic acids, fiber, and minerals. The purpose of this work was to evaluate the effect of pullulan coating on [...] Read more.

Fruits form an important part of a healthy human diet as they contain many ingredients with proven pro-health effects such as vitamins, phenolic compounds, organic acids, fiber, and minerals. The purpose of this work was to evaluate the effect of pullulan coating on the quality and shelf life of highbush blueberry during storage. General appearance, weight loss, dry matter, soluble solid content, reducing sugars, content of L-ascorbic acid, phenolic compounds (total phenolics, phenolics acids and anthocyanins) were determined in uncoated and coated blueberries fruits. The microbiological efficiency of pullulan coating was also evaluated. All parameters were monitored during storage at 4 °C and 16 °C by 28 and 14 days, respectively. The study showed that pullulan coating protects perishable food products especially susceptible to mechanical injury including fruits such as blueberries. Pullulan acts as a barrier that minimizes respiration rate, delaying deterioration and controlling microbial growth. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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15 pages, 3294 KiB

Open AccessArticle

Esterification Mechanism of Bagasse Modified with Glutaric Anhydride in 1-Allyl-3-methylimidazolium Chloride

by Huihui Wang¹, Wei Chen¹, Xueqin Zhang¹, Chuanfu Liu^1,*

and Runcang Sun^1,2

¹ State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China

² Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China

Materials 2017, 10(8), 966; https://doi.org/10.3390/ma10080966 - 18 Aug 2017

Cited by 13 | Viewed by 6662

Abstract

The esterification of bagasse with glutaric anhydride could increase surface adhesion compatibility and the surface of derived polymers has the potential of immobilizing peptides or proteins for biomedical application. Due to its complicated components, the esterification mechanism of bagasse esterified with glutaric anhydride [...] Read more.

The esterification of bagasse with glutaric anhydride could increase surface adhesion compatibility and the surface of derived polymers has the potential of immobilizing peptides or proteins for biomedical application. Due to its complicated components, the esterification mechanism of bagasse esterified with glutaric anhydride in ionic liquids has not been studied. In this paper, the homogenous esterification of bagasse with glutaric anhydride was comparatively investigated with the isolated cellulose, hemicelluloses, and lignin in 1-allyl-3-methylimidazolium chloride (AmimCl) to reveal the reaction mechanism. Fourier transform infrared (FT-IR) indicated that the three components (cellulose, hemicelluloses, and lignin) were all involved in the esterification. The percentage of substitution (PS) of bagasse was gradually improved with the increased dosage of glutaric anhydride (10–40 mmol/g), which was primarily attributed to the increased esterification of cellulose and hemicelluloses. However, the PS fluctuation of lignin led to a decrease in the PS of bagasse at high glutaric anhydride dosage (50 mmol/g). The esterification reactivity of bagasse components followed the order of lignin > hemicelluloses > cellulose. The esterification mechanism was proposed as a nucleophilic substitution reaction. Nuclear magnetic resonance (NMR) analysis indicated that lignin aliphatic hydroxyls were prior to be esterified, and primary hydroxyls were more reactive than secondary hydroxyls in cellulose and hemicelluloses. Full article

(This article belongs to the Section Advanced Materials Characterization)

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15 pages, 13103 KiB

Open AccessArticle

In Situ Synthesis of Silver Nanoparticles on the Polyelectrolyte-Coated Sericin/PVA Film for Enhanced Antibacterial Application

by Rui Cai¹, Gang Tao², Huawei He^2,3,*

, Pengchao Guo², Meirong Yang², Chaoxiang Ding², Hua Zuo⁴, Lingyan Wang¹, Ping Zhao² and Yejing Wang^1,*

¹ College of Biotechnology, Southwest University, Beibei, Chongqing 400715, China

² State Key Laboratory of Silkworm Genome Biology, Southwest University, Beibei, Chongqing 400715, China

³ Chongqing Engineering and Technology Research Center for Novel Silk Materials, Southwest University, Beibei, Chongqing 400715, China

⁴ College of Pharmaceutical Sciences, Southwest University, Beibei, Chongqing 400715, China

Materials 2017, 10(8), 967; https://doi.org/10.3390/ma10080967 - 18 Aug 2017

Cited by 29 | Viewed by 7034

Abstract

To develop silk sericin (SS) as a potential antibacterial biomaterial, a novel composite of polyelectrolyte multilayers (PEMs) coated sericin/poly(vinyl alcohol) (SS/PVA) film modified with silver nanoparticles (AgNPs) has been developed using a layer-by-layer assembly technique and ultraviolet-assisted AgNPs synthesis method. Ag ions were [...] Read more.

To develop silk sericin (SS) as a potential antibacterial biomaterial, a novel composite of polyelectrolyte multilayers (PEMs) coated sericin/poly(vinyl alcohol) (SS/PVA) film modified with silver nanoparticles (AgNPs) has been developed using a layer-by-layer assembly technique and ultraviolet-assisted AgNPs synthesis method. Ag ions were enriched by PEMs via the electrostatic attraction between Ag ions and PEMs, and then reduced to AgNPs in situ with the assistance of ultraviolet irradiation. PEMs facilitated the high-density growth of AgNPs and protected the synthesized AgNPs due to the formation of a 3D matrix, and thus endowed SS/PVA film with highly effective and durable antibacterial activity. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, Fourier transfer infrared spectroscopy, water contact angle, mechanical property and thermogravimetric analysis were applied to characterize SS/PVA, PEMs-SS/PVA and AgNPs-PEMs-SS/PVA films, respectively. AgNPs-PEMs-SS/PVA film has exhibited good mechanical performance, hydrophilicity, water absorption capability as well as excellent and durable antibacterial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa and good stability and degradability. This study has developed a simple method to design and prepare AgNPs-PEMs-SS/PVA film for potential antibacterial application. Full article

(This article belongs to the Section Biomaterials)

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11 pages, 2005 KiB

Open AccessFeature PaperArticle

The Effect of Hydrogen Bonding in Enhancing the Ionic Affinities of Immobilized Monoprotic Phosphate Ligands

by Spiro D. Alexandratos^1,2,* and Xiaoping Zhu¹

¹ Department of Chemistry, Hunter College of the City University of New York, New York, NY 10065, USA

² Graduate Center of the City University of New York, New York, NY 10016, USA

Materials 2017, 10(8), 968; https://doi.org/10.3390/ma10080968 - 18 Aug 2017

Cited by 16 | Viewed by 5348

Abstract

Environmental remediation requires ion-selective polymers that operate under a wide range of solution conditions. In one example, removal of trivalent and divalent metal ions from waste streams resulting from mining operations before they enter the environment requires treatment at acidic pH. The monoethyl [...] Read more.

Environmental remediation requires ion-selective polymers that operate under a wide range of solution conditions. In one example, removal of trivalent and divalent metal ions from waste streams resulting from mining operations before they enter the environment requires treatment at acidic pH. The monoethyl ester phosphate ligands developed in this report operate from acidic solutions. They have been prepared on polystyrene-bound ethylene glycol, glycerol, and pentaerythritol, and it is found that intra-ligand hydrogen bonding affects their metal ion affinities. The affinity for a set of trivalent (Fe(III), Al(III), La(III), and Lu(III)) and divalent (Pb(II), Cd(II), Cu(II), and Zn(II)) ions is greater than that of corresponding neutral diethyl esters and phosphonic acid. In an earlier study, hydrogen bonding was found important in determining the metal ion affinities of immobilized phosphorylated polyol diethyl ester coordinating ligands; their Fourier transform infrared (FTIR) band shifts indicated that the basicity of the phosphoryl oxygen increased by hydrogen bonding to auxiliary –OH groups on the neighboring polyol. The same mechanism is operative with the monoprotic resins along with hydrogen bonding to the P–OH acid site. This is reflected in the FTIR spectra: the neutral phosphate diethyl ester resins have the P=O band at 1265 cm⁻¹ while the monoethyl ester resins have the band shifted to 1230 cm⁻¹; hydrogen bonding is further indicated by the broadness of this region down to 900 cm⁻¹. The monoprotic pentaerythritol has the highest metal ion affinities of the polymers studied. Full article

(This article belongs to the Special Issue Sorption Materials for Environment Purification)

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23 pages, 12563 KiB

Open AccessArticle

ICP Materials Trends in Corrosion, Soiling and Air Pollution (1987–2014)

by Johan Tidblad^1,*, Kateřina Kreislová²

, Markus Faller³, Daniel De la Fuente⁴, Tim Yates⁵, Aurélie Verney-Carron⁶, Terje Grøntoft⁷, Andrew Gordon¹

and Ulrik Hans³

¹ Swerea KIMAB, Dept Corrosion, 164 07 Kista, Sweden

² Svuom Ltd., 17000 Prague, Czech Republic

³ Empa, Materials Science and Technology, 8600 Dübendorf, Switzerland

⁴ CENIM—National Centre for Metallurgical Research, 28040 Madrid, Spain

⁵ BRE—Building Research Establishment Ltd., Watford WD25 9XX, UK

⁶ LISA (Laboratoire Interuniversitaire des Systèmes Atmosphériques), UMR 7583 CNRS/UPEC/UPD, 94010 Creteil, France

⁷ NILU—Norwegian Institute for Air Research, 2027 Kjeller, Norway

Materials 2017, 10(8), 969; https://doi.org/10.3390/ma10080969 - 19 Aug 2017

Cited by 33 | Viewed by 7084

Abstract

Results from the international cooperative programme on effects on materials including historic and cultural monuments are presented from the period 1987–2014 and include pollution data (SO₂, NO₂, O₃, HNO₃ and PM₁₀), corrosion data (carbon [...] Read more.

Results from the international cooperative programme on effects on materials including historic and cultural monuments are presented from the period 1987–2014 and include pollution data (SO₂, NO₂, O₃, HNO₃ and PM₁₀), corrosion data (carbon steel, weathering steel, zinc, copper, aluminium and limestone) and data on the soiling of modern glass for nineteen industrial, urban and rural test sites in Europe. Both one-year and four-year corrosion data are presented. Corrosion and pollution have decreased significantly and a shift in the magnitude is generally observed around 1997: from a sharp decrease to a more modest decrease or to a constant level without any decrease. SO₂ levels, carbon steel and copper corrosion have decreased even after 1997, which is more pronounced in urban areas, while corrosion of the other materials shows no decrease after 1997, when looking at one-year values. When looking at four-year values, however, there is a significant decrease after 1997 for zinc, which is not evident when looking at the one-year values. This paper also presents results on corrosion kinetics by comparison of one- and four-year values. For carbon steel and copper, kinetics is relatively independent of sites while other materials, especially zinc, show substantial variation in kinetics for the first four years, which needs to be considered when producing new and possibly improved models for corrosion. Full article

(This article belongs to the Special Issue Fundamental and Research Frontier of Atmospheric Corrosion)

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16 pages, 2916 KiB

Open AccessArticle

Influence of Layer Thickness, Raster Angle, Deformation Temperature and Recovery Temperature on the Shape-Memory Effect of 3D-Printed Polylactic Acid Samples

by Wenzheng Wu, Wenli Ye, Zichao Wu^*, Peng Geng, Yulei Wang and Ji Zhao

School of Mechanical Science and Engineering, Jilin University, Renmin Street 5988, Changchun 130025, China

Materials 2017, 10(8), 970; https://doi.org/10.3390/ma10080970 - 19 Aug 2017

Cited by 121 | Viewed by 10249

Abstract

The success of the 3D-printing process depends upon the proper selection of process parameters. However, the majority of current related studies focus on the influence of process parameters on the mechanical properties of the parts. The influence of process parameters on the shape-memory [...] Read more.

The success of the 3D-printing process depends upon the proper selection of process parameters. However, the majority of current related studies focus on the influence of process parameters on the mechanical properties of the parts. The influence of process parameters on the shape-memory effect has been little studied. This study used the orthogonal experimental design method to evaluate the influence of the layer thickness H, raster angle θ, deformation temperature Td and recovery temperature Tr on the shape-recovery ratio Rr and maximum shape-recovery rate Vm of 3D-printed polylactic acid (PLA). The order and contribution of every experimental factor on the target index were determined by range analysis and ANOVA, respectively. The experimental results indicated that the recovery temperature exerted the greatest effect with a variance ratio of 416.10, whereas the layer thickness exerted the smallest effect on the shape-recovery ratio with a variance ratio of 4.902. The recovery temperature exerted the most significant effect on the maximum shape-recovery rate with the highest variance ratio of 1049.50, whereas the raster angle exerted the minimum effect with a variance ratio of 27.163. The results showed that the shape-memory effect of 3D-printed PLA parts depended strongly on recovery temperature, and depended more weakly on the deformation temperature and 3D-printing parameters. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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12 pages, 2934 KiB

Open AccessArticle

Synthesis and Characteristic of Xylan-grafted-polyacrylamide and Application for Improving Pulp Properties

by Gui-Bin Xu¹, Wei-Qing Kong¹, Chuan-Fu Liu¹

, Run-Cang Sun² and Jun-Li Ren^1,*

¹ State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China

² Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China

Materials 2017, 10(8), 971; https://doi.org/10.3390/ma10080971 - 20 Aug 2017

Cited by 11 | Viewed by 4931

Abstract

Recently, more attentions have been focused on the exploration of hemicelluloses in the paper industry. In this work, xylan-grafted-polyacrylamide (xylan-g-PAM) biopolymers were synthesized by the graft copolymerization of xylan with acrylamide, and their interaction with fibers was also investigated to improve waste newspaper [...] Read more.

Recently, more attentions have been focused on the exploration of hemicelluloses in the paper industry. In this work, xylan-grafted-polyacrylamide (xylan-g-PAM) biopolymers were synthesized by the graft copolymerization of xylan with acrylamide, and their interaction with fibers was also investigated to improve waste newspaper pulp properties with or without cationic fiber fines. The influences of synthesis conditions were studied on the grafting ratio and the grafting efficiency of biopolymers. Prepared biopolymers were characterized by FTIR, ¹³C NMR, TGA and rheology. It was found that the grafting of PAM on xylan was conductive to improve xylan properties, such as the solubility in water, rheological features, and thermal stability, and the maximum grafting ratio was achieved to 14.7%. Moreover, xylan-g-PAM could obviously enhance the mechanical properties of waste paper pulps. Xylan-g-PAM also played the dominant role in increasing the strength of paper in the combination with prepared cationic fine fibers. When the amounts of xylan-g-PAM and cationic fiber fines were 1.0 wt % and 0.5 wt %, the mechanical properties such as the tensile index was increased by 49.09%, tear index was increased by 36.54%, and the burst index was increased by 20.67%, when compared with the control handsheets. Therefore, xylan-g-PAM as the new biopolymer could be promising in the application of strength agents for the paper industry as well as cationic fiber fines. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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11 pages, 7363 KiB

Open AccessArticle

A Simple Method for High-Performance, Solution-Processed, Amorphous ZrO₂ Gate Insulator TFT with a High Concentration Precursor

by Wei Cai¹, Zhennan Zhu¹, Jinglin Wei¹, Zhiqiang Fang¹, Honglong Ning^1,*

, Zeke Zheng¹, Shangxiong Zhou¹, Rihui Yao^1,*

, Junbiao Peng¹ and Xubing Lu²

¹ Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

² Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China

Materials 2017, 10(8), 972; https://doi.org/10.3390/ma10080972 - 21 Aug 2017

Cited by 27 | Viewed by 6404

Abstract

Solution-processed high-k dielectric TFTs attract much attention since they cost relatively little and have a simple fabrication process. However, it is still a challenge to reduce the leakage of the current density of solution-processed dielectric TFTs. Here, a simple solution method is presented [...] Read more.

Solution-processed high-k dielectric TFTs attract much attention since they cost relatively little and have a simple fabrication process. However, it is still a challenge to reduce the leakage of the current density of solution-processed dielectric TFTs. Here, a simple solution method is presented towards enhanced performance of ZrO₂ films by intentionally increasing the concentration of precursor. The ZrO₂ films not only exhibit a low leakage current density of 10⁻⁶ A/cm² at 10 V and a breakdown field of 2.5 MV/cm, but also demonstrate a saturation mobility of 12.6 cm²·V⁻¹·s⁻¹ and a I_on/I_off ratio of 10⁶ in DC pulse sputtering IGZO-TFTs based on these films. Moreover, the underlying mechanism of influence of precursor concentration on film formation is presented. Higher concentration precursor results in a thicker film within same coating times with reduced ZrO₂/IGZO interface defects and roughness. It shows the importance of thickness, roughness, and annealing temperature in solution-processed dielectric oxide TFT and provides an approach to precisely control solution-processed oxide films thickness. Full article

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8 pages, 4593 KiB

Open AccessArticle

Genetically Engineered Phage Induced Selective H9c2 Cardiomyocytes Patterning in PDMS Microgrooves

by Youngjun Kim^1,3,*

, Chunga Kwon^1,3 and Hojeong Jeon^2,3

¹ Korea Institute of Science and Technology Europe (KIST-Europe) Forschungsgesellschaft mbH, Campus E 7 1, 66123 Saarbrücken, Germany

² Center for Biomaterials, Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Korea

³ Department of Biomedical Engineering, University of Science and Technology (UST), Daejeon 34113, Korea

Materials 2017, 10(8), 973; https://doi.org/10.3390/ma10080973 - 21 Aug 2017

Cited by 15 | Viewed by 7145

Abstract

A micro-patterned cell adhesive surface was prepared for future design of medical devices. One-dimensional polydimethylsiloxane (PDMS) micro-patterns were prepared by a photolithography process. Afterwards, recombinant filamentous phages that displayed a short binding motif with a cell adhesive peptide (-RGD-) on p8 proteins were [...] Read more.

A micro-patterned cell adhesive surface was prepared for future design of medical devices. One-dimensional polydimethylsiloxane (PDMS) micro-patterns were prepared by a photolithography process. Afterwards, recombinant filamentous phages that displayed a short binding motif with a cell adhesive peptide (-RGD-) on p8 proteins were immobilized on PDMS microgrooves through simple contact printing to study the cellular response of rat H9c2 cardiomyocyte. While the cell density decreased on PDMS micro-patterns, we observed enhanced cell proliferation and cell to surface interaction on the RGD-phage coated PDMS microgrooves. The RGD-phage coating also supported a better alignment of cell spreading rather than isotropic cell growths as we observed on non-pattered PDMS surface. Full article

(This article belongs to the Special Issue Constitutive Modelling of Biological Tissues and Biomaterials)

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10 pages, 2091 KiB

Open AccessArticle

Preparation and Characterization of Cyclotrimethylenetrinitramine (RDX) with Reduced Sensitivity

by Yuqiao Wang¹, Xin Li², Shusen Chen¹, Xiao Ma³, Ziyang Yu¹, Shaohua Jin¹, Lijie Li¹ and Yu Chen^1,*

¹ School of Materials Science and Engineeering, Beijing Institute of Technology, Beijing 100081, China

² Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, China

³ Research Institute, Gansu Yin’guang Chemical Industry Group Co., Ltd., Baiyin 730900, China

Materials 2017, 10(8), 974; https://doi.org/10.3390/ma10080974 - 21 Aug 2017

Cited by 30 | Viewed by 7615

Abstract

The internal defects and shape of cyclotrimethylenetrinitramine (RDX) crystal are critical parameters for the preparation of reduced sensitivity RDX (RS-RDX). In the current study, RDX was re-crystallized and spheroidized to form the high-quality RDX that was further characterized by purity, apparent density, size [...] Read more.

The internal defects and shape of cyclotrimethylenetrinitramine (RDX) crystal are critical parameters for the preparation of reduced sensitivity RDX (RS-RDX). In the current study, RDX was re-crystallized and spheroidized to form the high-quality RDX that was further characterized by purity, apparent density, size distribution, specific surface area, impact sensitivity, and shock sensitivity. The effects of re-crystallization solvent on the growth morphology of RDX crystal were investigated by both theoretical simulation and experiment test, and consistent results were obtained. The high-quality RDX exhibited a high purity (≥99.90%), high apparent density (≥1.811 g/cm³), spherical shape, and relatively low impact sensitivity (6%). Its specific surface area was reduced more than 30%. Compared with conventional RDXs, the high-quality RDX reduced the shock sensitivities of PBXN-109 and PBXW-115 by more than 30%, indicating that it was a RS-RDX. The reduced sensitivity and good processability of the high-quality RDX would be significant in improving the performances of RDX-based PBXs. Full article

(This article belongs to the Special Issue Energetic Materials and Processes)

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14 pages, 3714 KiB

Open AccessArticle

Carbon Nanostructure of Kraft Lignin Thermally Treated at 500 to 1000 °C

by Xuefeng Zhang¹

, Qiangu Yan^1,*, Weiqi Leng², Jinghao Li², Jilei Zhang^1,*, Zhiyong Cai^2,* and El Barbary Hassan¹

¹ Department of Sustainable Bioproducts, Mississippi State University 1, Starkville, MS 39759, USA

² USA Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI 53726, USA

Materials 2017, 10(8), 975; https://doi.org/10.3390/ma10080975 - 21 Aug 2017

Cited by 65 | Viewed by 8774

Abstract

Kraft lignin (KL) was thermally treated at 500 to 1000 °C in an inert atmosphere. Carbon nanostructure parameters of thermally treated KL in terms of amorphous carbon fraction, aromaticity, and carbon nanocrystallites lateral size (L_a), thickness (L_c), [...] Read more.

Kraft lignin (KL) was thermally treated at 500 to 1000 °C in an inert atmosphere. Carbon nanostructure parameters of thermally treated KL in terms of amorphous carbon fraction, aromaticity, and carbon nanocrystallites lateral size (L_a), thickness (L_c), and interlayer space (d₀₀₂) were analyzed quantitatively using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. Experimental results indicated that increasing temperature reduced amorphous carbon but increased aromaticity in thermally treated KL materials. The L_c value of thermally treated KL materials averaged 0.85 nm and did not change with temperature. The d₀₀₂ value decreased from 3.56 Å at 500 °C to 3.49 Å at 1000 °C. The L_a value increased from 0.7 to 1.4 nm as temperature increased from 500 to 1000 °C. A nanostructure model was proposed to describe thermally treated KL under 1000 °C. The thermal stability of heat treated KL increased with temperature rising from 500 to 800 °C. Full article

(This article belongs to the Section Advanced Materials Characterization)

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10 pages, 9151 KiB

Open AccessArticle

Preparation and Characterization of Mo Doped in BiVO₄ with Enhanced Photocatalytic Properties

by Bitao Liu¹, Xuelian Yan¹, Hengqing Yan¹, Yucen Yao¹, Yanhua Cai¹, Jumeng Wei^2,*, Shanyong Chen^1,*, Xuhui Xu³ and Lu Li^1,*

¹ Chongqing Key Laboratory of Environmental Materials and Remediation Technology, Research Institute for New Materials Technology, Chongqing University of Arts and Sciences, Yongchuan, Chongqing 402160, China

² College of Chemistry and Materials Engineering, Anhui Science and Technology of University, Fengyang 233100, China

³ School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China

Materials 2017, 10(8), 976; https://doi.org/10.3390/ma10080976 - 21 Aug 2017

Cited by 45 | Viewed by 8903

Abstract

Molybdenum (Mo) doped BiVO₄ was fabricated via a simple electrospun method. Morphology, structure, chemical states and optical properties of the obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse [...] Read more.

Molybdenum (Mo) doped BiVO₄ was fabricated via a simple electrospun method. Morphology, structure, chemical states and optical properties of the obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), N₂ adsorption–desorption isotherms (BET) and photoluminescence spectrum (PL), respectively. The photocatalytic properties indicate that doping Mo into BiVO₄ can enhance the photocatalytic activity and dark adsorption ability. The photocatalytic test suggests that the 1% Mo-BiVO₄ shows the best photocatalytic activity, which is about three times higher than pure BiVO₄. Meanwhile, 3% Mo-BiVO₄ shows stronger dark adsorption than pure BiVO₄ and 1% Mo-BiVO₄. The enhancement in photocatalytic property should be ascribed to that BiVO₄ with small amount of Mo doping could efficiently separate the photogenerated carries and improve the electronic conductivity. The high concentration doping would lead the crystal structure transformation from monoclinic to tetragonal phase, as well as the formation of MoO₃ nanoparticles on the BiVO₄ surface, which could also act as recombination centers to decrease the photocatalytic activity. Full article

(This article belongs to the Section Energy Materials)

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19 pages, 4690 KiB

Open AccessArticle

Influence of Binders and Lightweight Aggregates on the Properties of Cementitious Mortars: From Traditional Requirements to Indoor Air Quality Improvement

by Chiara Giosuè¹

, Mattia Pierpaoli¹

, Alessandra Mobili¹

, Maria Letizia Ruello¹

and Francesca Tittarelli^1,2,*

¹ Department of Materials, Environmental Sciences and Urban Planning (SIMAU), Università Politecnica delle Marche, 60131 Ancona, Italy

² Institute of Atmospheric Sciences and Climate, National Research Council (ISAC-CNR), 40129 Bologna, Italy

Materials 2017, 10(8), 978; https://doi.org/10.3390/ma10080978 - 22 Aug 2017

Cited by 42 | Viewed by 5183

Abstract

Innovative and multifunctional mortars for renders and panels were manufactured using white photocatalytic and non-photocatalytic cement as binder. Unconventional aggregates, based on lightweight materials with high specific surface and adsorbent properties, were adopted in order to investigate the possible ability to passively improve [...] Read more.

Innovative and multifunctional mortars for renders and panels were manufactured using white photocatalytic and non-photocatalytic cement as binder. Unconventional aggregates, based on lightweight materials with high specific surface and adsorbent properties, were adopted in order to investigate the possible ability to passively improve indoor air quality. The reference mortar was manufactured with traditional calcareous sand. Results show that even if the mechanical properties of mortars with unconventional aggregates generally decrease, they remain acceptable for application as render. The innovative mortars were able to passively improve indoor air quality in terms of transpirability (70% higher), moisture buffering ability (65% higher) and depolluting capacity (up to 75% higher) compared to traditional ones under the current test conditions. Full article

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14 pages, 6544 KiB

Open AccessArticle

Self-Sealing Cementitious Materials by Using Water-Swelling Rubber Particles

by Leyang Lv^1,2,*, Erik Schlangen¹

and Feng Xing²

¹ Micromechanics Laboratory (MICROLAB), Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands

² Guangdong Province Key Laboratory of Durability for Marine Civil Engineering, School of Civil Engineering, Shenzhen University, Shenzhen 518060, China

Materials 2017, 10(8), 979; https://doi.org/10.3390/ma10080979 - 22 Aug 2017

Cited by 6 | Viewed by 5600

Abstract

Water ingress into cracked concrete structures is a serious problem, as it can cause leakage and reinforcement corrosion and thus reduce functionality and safety of the structures. In this study, the application of water-swelling rubber particles for providing the cracked concrete a self-sealing [...] Read more.

Water ingress into cracked concrete structures is a serious problem, as it can cause leakage and reinforcement corrosion and thus reduce functionality and safety of the structures. In this study, the application of water-swelling rubber particles for providing the cracked concrete a self-sealing function was developed. The feasibility of applying water-swelling rubber particles and the influence of incorporating water-swelling rubber particles on the mechanical properties of concrete was investigated. The self-sealing efficiency of water-swelling rubber particles with different content and particle size was quantified through a permeability test. The sealing effect of the water swelling rubber particles was monitored by X-ray computed tomography. The experimental results show that, by using 6% of these water swelling rubber particles as a replacement of aggregates in concrete, up to 64% and 61% decrease of water permeability was realized for 0.7 mm and 1.0 mm cracks. Furthermore, when the concrete cracks, the water swelling rubber particles can act as a crack bridging filler, preventing the crack from fully separating the specimens in two pieces. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for the Built Environment)

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14 pages, 8454 KiB

Open AccessArticle

Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating

by Anping Dong^1,2, Baoping Li^3,*, Yanling Lu^4,*, Guoliang Zhu^1,2,*, Hui Xing^1,2, Da Shu^1,2, Baode Sun^1,2,5 and Jun Wang^1,2,5

¹ School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

² Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming, Shanghai 200240, China

³ Hechi Industry and Information Committee, Hechi 547000, China

⁴ Department of Nuclear Materials Science and Engineering, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China

⁵ State Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China

Materials 2017, 10(8), 980; https://doi.org/10.3390/ma10080980 - 22 Aug 2017

Cited by 28 | Viewed by 8323

Abstract

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low [...] Read more.

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0–3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn₂ changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe₂Al₅ inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products. Full article

(This article belongs to the Section Advanced Materials Characterization)

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Review

Jump to: Editorial, Research

19 pages, 1565 KiB

Open AccessReview

Production of High-Value Nanoparticles via Biogenic Processes Using Aquacultural and Horticultural Food Waste

by Purabi R. Ghosh¹, Derek Fawcett¹, Shashi B. Sharma² and Gerrard E. J. Poinern^1,*

¹ Murdoch Applied Nanotechnology Research Group, Department of Physics, Energy Studies and Nanotechnology, School of Engineering and Energy, Murdoch University, Murdoch, Western Australia 6150, Australia

² Department of Primary Industries and Regional Development, 3 Baron Hay Court, South Perth, Western Australia 6151, Australia

Materials 2017, 10(8), 852; https://doi.org/10.3390/ma10080852 - 25 Jul 2017

Cited by 78 | Viewed by 10335

Abstract

The quantities of organic waste produced globally by aquacultural and horticulture are extremely large and offer an attractive renewable source of biomolecules and bioactive compounds. The availability of such large and diverse sources of waste materials creates a unique opportunity to develop new [...] Read more.

The quantities of organic waste produced globally by aquacultural and horticulture are extremely large and offer an attractive renewable source of biomolecules and bioactive compounds. The availability of such large and diverse sources of waste materials creates a unique opportunity to develop new recycling and food waste utilisation strategies. The aim of this review is to report the current status of research in the emerging field of producing high-value nanoparticles from food waste. Eco-friendly biogenic processes are quite rapid, and are usually carried out at normal room temperature and pressure. These alternative clean technologies do not rely on the use of the toxic chemicals and solvents commonly associated with traditional nanoparticle manufacturing processes. The relatively small number of research articles in the field have been surveyed and evaluated. Among the diversity of waste types, promising candidates and their ability to produce various high-value nanoparticles are discussed. Experimental parameters, nanoparticle characteristics and potential applications for nanoparticles in pharmaceuticals and biomedical applications are discussed. In spite of the advantages, there are a number of challenges, including nanoparticle reproducibility and understanding the formation mechanisms between different food waste products. Thus, there is considerable scope and opportunity for further research in this emerging field. Full article

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33 pages, 15764 KiB

Open AccessReview

Biosorbents for Removing Hazardous Metals and Metalloids

by Katsutoshi Inoue^1,*, Durga Parajuli², Kedar Nath Ghimire³, Biplob Kumar Biswas⁴, Hidetaka Kawakita¹, Tatsuya Oshima⁵ and Keisuke Ohto¹

¹ Department of Applied Chemistry, Faculty of Science and Engineering, Saga University, Honjo-machi 1, Saga 840-8574, Japan

² Nanomaterial Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaragi 305-8565, Japan

³ Central Department of Chemistry, Tribhuvan University, Kritipur, Kathmandu, Nepal

⁴ Department of Chemical Engineering, Faculty of Engineering and Technology, Jessore University of Science and Technology, Jessore 7408, Bangladesh

⁵ Department of Applied Chemistry, Faculty of Engineering, University of Miyazaki, Gakuen Kibanadai-nishi 1-1, Miyazaki 889-2192, Japan

Materials 2017, 10(8), 857; https://doi.org/10.3390/ma10080857 - 26 Jul 2017

Cited by 35 | Viewed by 7528

Abstract

Biosorbents for remediating aquatic environmental media polluted with hazardous heavy metals and metalloids such as Pb(II), Cr(VI), Sb(III and V), and As(III and V) were prepared from lignin waste, orange and apple juice residues, seaweed and persimmon and grape wastes using simple and [...] Read more.

Biosorbents for remediating aquatic environmental media polluted with hazardous heavy metals and metalloids such as Pb(II), Cr(VI), Sb(III and V), and As(III and V) were prepared from lignin waste, orange and apple juice residues, seaweed and persimmon and grape wastes using simple and cheap methods. A lignophenol gel such as lignocatechol gel was prepared by immobilizing the catechol functional groups onto lignin from sawdust, while lignosulfonate gel was prepared directly from waste liquor generated during pulp production. These gels effectively removed Pb(II). Orange and apple juice residues, which are rich in pectic acid, were easily converted using alkali (e.g., calcium hydroxide) into biosorbents that effectively removed Pb(II). These materials also effectively removed Sb(III and V) and As(III and V) when these were preloaded with multi-valent metal ions such as Zr(IV) and Fe(III). Similar biosorbents were prepared from seaweed waste, which is rich in alginic acid. Other biosorbents, which effectively removed Cr(VI), were prepared by simply treating persimmon and grape wastes with concentrated sulfuric acid. Full article

(This article belongs to the Special Issue Sorption Materials for Environment Purification)

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18 pages, 10634 KiB

Open AccessReview

A Review on Disorder-Driven Metal–Insulator Transition in Crystalline Vacancy-Rich GeSbTe Phase-Change Materials

by Jiang-Jing Wang^1,†, Ya-Zhi Xu^1,†, Riccardo Mazzarello², Matthias Wuttig³ and Wei Zhang^1,*

¹ Center for Advancing Materials Performance from the Nanoscale, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China

² Institute for Theoretical Solid-State Physics, JARA-FIT and JARA-HPC, RWTH Aachen University, 52074 Aachen, Germany

³ Institute of Physics IA, JARA-FIT and JARA-HPC, RWTH Aachen University, 52074 Aachen, Germany

^† These authors contribute equally to this work.

Materials 2017, 10(8), 862; https://doi.org/10.3390/ma10080862 - 27 Jul 2017

Cited by 59 | Viewed by 9439

Abstract

Metal–insulator transition (MIT) is one of the most essential topics in condensed matter physics and materials science. The accompanied drastic change in electrical resistance can be exploited in electronic devices, such as data storage and memory technology. It is generally accepted that the [...] Read more.

Metal–insulator transition (MIT) is one of the most essential topics in condensed matter physics and materials science. The accompanied drastic change in electrical resistance can be exploited in electronic devices, such as data storage and memory technology. It is generally accepted that the underlying mechanism of most MITs is an interplay of electron correlation effects (Mott type) and disorder effects (Anderson type), and to disentangle the two effects is difficult. Recent progress on the crystalline Ge₁Sb₂Te₄ (GST) compound provides compelling evidence for a disorder-driven MIT. In this work, we discuss the presence of strong disorder in GST, and elucidate its effects on electron localization and transport properties. We also show how the degree of disorder in GST can be reduced via thermal annealing, triggering a disorder-driven metal–insulator transition. The resistance switching by disorder tuning in crystalline GST may enable novel multilevel data storage devices. Full article

(This article belongs to the Special Issue Metal-Insulator Transition)

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18 pages, 2305 KiB

Open AccessReview

Characterization of Gallium Indium Phosphide and Progress of Aluminum Gallium Indium Phosphide System Quantum-Well Laser Diode

by Hiroki Hamada

Department of Electric and Electronic Engineering, Kinki University, Higashi-Osaka 577-8502, Japan

Materials 2017, 10(8), 875; https://doi.org/10.3390/ma10080875 - 28 Jul 2017

Cited by 13 | Viewed by 8379

Abstract

Highly ordered gallium indium phosphide layers with the low bandgap have been successfully grown on the (100) GaAs substrates, the misorientation toward [01−1] direction, using the low-pressure metal organic chemical vapor deposition method. It is found that the optical properties of the layers [...] Read more.

Highly ordered gallium indium phosphide layers with the low bandgap have been successfully grown on the (100) GaAs substrates, the misorientation toward [01−1] direction, using the low-pressure metal organic chemical vapor deposition method. It is found that the optical properties of the layers are same as those of the disordered ones, essentially different from the ordered ones having two orientations towards [1−11] and [11−1] directions grown on (100) gallium arsenide substrates, which were previously reported. The bandgap at 300 K is 1.791 eV. The value is the smallest ever reported, to our knowledge. The high performance transverse stabilized AlGaInP laser diodes with strain compensated quantum well structure, which is developed in 1992, have been successfully obtained by controlling the misorientation angle and directions of GaAs substrates. The structure is applied to quantum dots laser diodes. This paper also describes the development history of the quantum well and the quantum dots laser diodes, and their future prospects. Full article

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33 pages, 6686 KiB

Open AccessReview

Metallic Biomaterials: Current Challenges and Opportunities

by Karthika Prasad^1,2,3,*, Olha Bazaka⁴, Ming Chua¹, Madison Rochford¹, Liam Fedrick¹, Jordan Spoor¹, Richard Symes¹, Marcus Tieppo¹, Cameron Collins¹, Alex Cao¹, David Markwell¹

, Kostya (Ken) Ostrikov^1,2,3 and Kateryna Bazaka^1,2,3,4,*

¹ School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4000, Australia

² CSIRO-QUT Joint Sustainable Processes and Devices Laboratory, Commonwealth Scientific and Industrial Research Organization, P.O. Box 218, Lindfield, NSW 2070, Australia

³ Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD 4000, Australia

⁴ College of Science and Engineering, Technology and Engineering, James Cook University, Townsville, QLD 4810, Australia

Materials 2017, 10(8), 884; https://doi.org/10.3390/ma10080884 - 31 Jul 2017

Cited by 537 | Viewed by 23123

Abstract

Metallic biomaterials are engineered systems designed to provide internal support to biological tissues and they are being used largely in joint replacements, dental implants, orthopaedic fixations and stents. Higher biomaterial usage is associated with an increased incidence of implant-related complications due to poor [...] Read more.

Metallic biomaterials are engineered systems designed to provide internal support to biological tissues and they are being used largely in joint replacements, dental implants, orthopaedic fixations and stents. Higher biomaterial usage is associated with an increased incidence of implant-related complications due to poor implant integration, inflammation, mechanical instability, necrosis and infections, and associated prolonged patient care, pain and loss of function. In this review, we will briefly explore major representatives of metallic biomaterials along with the key existing and emerging strategies for surface and bulk modification used to improve biointegration, mechanical strength and flexibility of biometals, and discuss their compatibility with the concept of 3D printing. Full article

(This article belongs to the Special Issue Biocompatibility of Materials)

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18 pages, 9951 KiB

Open AccessFeature PaperReview

Surface Sensitive Techniques for Advanced Characterization of Luminescent Materials

by Hendrik C. Swart

Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA93002, South Africa

Materials 2017, 10(8), 906; https://doi.org/10.3390/ma10080906 - 4 Aug 2017

Cited by 14 | Viewed by 5689

Abstract

The important role of surface sensitive characterization techniques such as Auger electron spectroscopy (AES), X-ray photo electron spectroscopy (XPS), time of flight scanning ion mass spectrometry (TOF-SIMS) and High resolution transmission electron microscopy (HRTEM) for the characterization of different phosphor materials is discussed [...] Read more.

The important role of surface sensitive characterization techniques such as Auger electron spectroscopy (AES), X-ray photo electron spectroscopy (XPS), time of flight scanning ion mass spectrometry (TOF-SIMS) and High resolution transmission electron microscopy (HRTEM) for the characterization of different phosphor materials is discussed in this short review by giving selective examples from previous obtained results. AES is used to monitor surface reactions during electron bombardment and also to determine the elemental composition of the surfaces of the materials, while XPS and TOF-SIMS are used for determining the surface chemical composition and valence state of the dopants. The role of XPS to determine the presence of defects in the phosphor matrix is also stated with the different examples. The role of HRTEM in combination with Energy dispersive spectroscopy (EDS) for nanoparticle characterization is also pointed out. Full article

(This article belongs to the Special Issue Techniques and Methods for Advanced Characterization of Luminescent Materials)

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49 pages, 8321 KiB

Open AccessReview

Smart Carriers and Nanohealers: A Nanomedical Insight on Natural Polymers

by Sreejith Raveendran^†, Ankit K. Rochani^†, Toru Maekawa and D. Sakthi Kumar^*

¹ Bio Nano Electronics Research Centre, Graduate School of Interdisciplinary New Science, Toyo University, Saitama 350-8585, Japan

^† These authors contributed equally to this work.

Materials 2017, 10(8), 929; https://doi.org/10.3390/ma10080929 - 10 Aug 2017

Cited by 47 | Viewed by 8754

Abstract

Biodegradable polymers are popularly being used in an increasing number of fields in the past few decades. The popularity and favorability of these materials are due to their remarkable properties, enabling a wide range of applications and market requirements to be met. Polymer [...] Read more.

Biodegradable polymers are popularly being used in an increasing number of fields in the past few decades. The popularity and favorability of these materials are due to their remarkable properties, enabling a wide range of applications and market requirements to be met. Polymer biodegradable systems are a promising arena of research for targeted and site-specific controlled drug delivery, for developing artificial limbs, 3D porous scaffolds for cellular regeneration or tissue engineering and biosensing applications. Several natural polymers have been identified, blended, functionalized and applied for designing nanoscaffolds and drug carriers as a prerequisite for enumerable bionano technological applications. Apart from these, natural polymers have been well studied and are widely used in material science and industrial fields. The present review explains the prominent features of commonly used natural polymers (polysaccharides and proteins) in various nanomedical applications and reveals the current status of the polymer research in bionanotechnology and science sectors. Full article

(This article belongs to the Special Issue Biocompatibility of Materials)

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17 pages, 4739 KiB

Open AccessReview

Artificial Structural Color Pixels: A Review

by Yuqian Zhao¹, Yong Zhao^1,*, Sheng Hu¹, Jiangtao Lv¹, Yu Ying², Gediminas Gervinskas³ and Guangyuan Si^3,*

¹ College of Information Science and Engineering, Northeastern University, Shenyang 110004, China

² College of Information & Control Engineering, Shenyang Jianzhu University, Shenyang 110168, China

³ Melbourne Centre for Nanofabrication, Clayton, Victoria 3168, Australia

Materials 2017, 10(8), 944; https://doi.org/10.3390/ma10080944 - 14 Aug 2017

Cited by 69 | Viewed by 13299

Abstract

Inspired by natural photonic structures (Morpho butterfly, for instance), researchers have demonstrated varying artificial color display devices using different designs. Photonic-crystal/plasmonic color filters have drawn increasing attention most recently. In this review article, we show the developing trend of artificial structural color pixels [...] Read more.

Inspired by natural photonic structures (Morpho butterfly, for instance), researchers have demonstrated varying artificial color display devices using different designs. Photonic-crystal/plasmonic color filters have drawn increasing attention most recently. In this review article, we show the developing trend of artificial structural color pixels from photonic crystals to plasmonic nanostructures. Such devices normally utilize the distinctive optical features of photonic/plasmon resonance, resulting in high compatibility with current display and imaging technologies. Moreover, dynamical color filtering devices are highly desirable because tunable optical components are critical for developing new optical platforms which can be integrated or combined with other existing imaging and display techniques. Thus, extensive promising potential applications have been triggered and enabled including more abundant functionalities in integrated optics and nanophotonics. Full article

(This article belongs to the Special Issue Advance in Plasmonics and Metamaterials)

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15 pages, 426 KiB

Open AccessReview

Update on Monoterpenes as Antimicrobial Agents: A Particular Focus on p-Cymene

by Anna Marchese¹

, Carla Renata Arciola^2,3

, Ramona Barbieri¹

, Ana Sanches Silva^4,5, Seyed Fazel Nabavi⁶, Arold Jorel Tsetegho Sokeng⁷, Morteza Izadi⁸, Nematollah Jonaidi Jafari⁸, Ipek Suntar⁹, Maria Daglia^7,*

and Seyed Mohammad Nabavi^6,*

¹ Sezione di Microbiologia DISC-IRCCS San Martino-IST University of Genoa, 16132 Genoa, Italy

² Research Unit on Implant Infections, Rizzoli Orthopaedic Institute, via di Barbiano 1/10, 40136 Bologna, Italy

³ Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, Via San Giacomo 14, 40126 Bologna, Italy

⁴ National Institute for Agricultural and Veterinary Research (INIAV), I.P., Vairão, 4480 Vila do Conde, Portugal

⁵ Center for Study in Animal Science (CECA), ICETA, University of Oporto, 4051-401 Oporto, Portugal

⁶ Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran 19395-5487, Iran

⁷ Department of Drug Sciences, Medicinal Chemistry and Pharmaceutical Technology Section, University of Pavia, 27100 Pavia, Italy

⁸ Health Research Center, Baqiyatallah University of Medical Sciences, Tehran 19395-5487, Iran

⁹ Department of Pharmacognosy, Faculty of Pharmacy, Gazi University, Etiler, Ankara 06330, Turkey

Materials 2017, 10(8), 947; https://doi.org/10.3390/ma10080947 - 15 Aug 2017

Cited by 286 | Viewed by 12517

Abstract

p-Cymene [1-methyl-4-(1-methylethyl)-benzene] is a monoterpene found in over 100 plant species used for medicine and food purposes. It shows a range of biological activity including antioxidant, anti-inflammatory, antinociceptive, anxiolytic, anticancer and antimicrobial effects. This last property has been widely investigated due to the [...] Read more.

p-Cymene [1-methyl-4-(1-methylethyl)-benzene] is a monoterpene found in over 100 plant species used for medicine and food purposes. It shows a range of biological activity including antioxidant, anti-inflammatory, antinociceptive, anxiolytic, anticancer and antimicrobial effects. This last property has been widely investigated due to the urgent need for new substances with antimicrobial properties, to be used to treat communicable diseases whose diffusion in developed countries has been facilitated by globalization and the evolution of antimicrobial resistance. This review summarizes available scientific data, as reported by the most recent studies describing the antimicrobial activity of p-cymene either alone, or as the main component of plant extracts, as well as addressing the mechanisms of action of cymenes as antimicrobial agents. While p-cymene is one of the major constituents of extracts and essential oils used in traditional medicines as antimicrobial agents, but considering the limited data on its in vivo efficacy and safety, further studies are required to reach a definitive recommendation on the use and beneficial effects of p-cymene in human healthcare and in biomedical applications as a promising candidate to functionalize biomaterials and nanomaterials. Full article

(This article belongs to the Special Issue State-of-the-Art Materials Science in Italy 2017)

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22 pages, 2084 KiB

Open AccessFeature PaperReview

Combination of Poly(lactic) Acid and Starch for Biodegradable Food Packaging

by Justine Muller

, Chelo González-Martínez and Amparo Chiralt^*

Universidad Politécnica de Valencia, IIAD, Camino de Vera, s/n, 46022 València, Spain

Materials 2017, 10(8), 952; https://doi.org/10.3390/ma10080952 - 15 Aug 2017

Cited by 361 | Viewed by 25460

Abstract

The massive use of synthetic plastics, in particular in the food packaging area, has a great environmental impact, and alternative more ecologic materials are being required. Poly(lactic) acid (PLA) and starch have been extensively studied as potential replacements for non-degradable petrochemical polymers on [...] Read more.

The massive use of synthetic plastics, in particular in the food packaging area, has a great environmental impact, and alternative more ecologic materials are being required. Poly(lactic) acid (PLA) and starch have been extensively studied as potential replacements for non-degradable petrochemical polymers on the basis of their availability, adequate food contact properties and competitive cost. Nevertheless, both polymers exhibit some drawbacks for packaging uses and need to be adapted to the food packaging requirements. Starch, in particular, is very water sensitive and its film properties are heavily dependent on the moisture content, exhibiting relatively low mechanical resistance. PLA films are very brittle and offer low resistance to oxygen permeation. Their combination as blend or multilayer films could provide properties that are more adequate for packaging purposes on the basis of their complementary characteristics. The main characteristics of PLA and starch in terms of not only the barrier and mechanical properties of their films but also of their combinations, by using blending or multilayer strategies, have been analyzed, identifying components or processes that favor the polymer compatibility and the good performance of the combined materials. The properties of some blends/combinations have been discussed in comparison with those of pure polymer films. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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21 pages, 3917 KiB

Open AccessReview

Samarium Monosulfide (SmS): Reviewing Properties and Applications

by Andreas Sousanis, Philippe F. Smet

and Dirk Poelman^*

Lumilab, Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Gent, Belgium

Materials 2017, 10(8), 953; https://doi.org/10.3390/ma10080953 - 16 Aug 2017

Cited by 33 | Viewed by 9384

Abstract

In this review, we give an overview of the properties and applications of samarium monosulfide, SmS, which has gained considerable interest as a switchable material. It shows a pressure-induced phase transition from the semiconducting to the metallic state by polishing, and it switches [...] Read more.

In this review, we give an overview of the properties and applications of samarium monosulfide, SmS, which has gained considerable interest as a switchable material. It shows a pressure-induced phase transition from the semiconducting to the metallic state by polishing, and it switches back to the semiconducting state by heating. The material also shows a magnetic transition, from the paramagnetic state to an antiferromagnetically ordered state. The switching behavior between the semiconducting and metallic states could be exploited in several applications, such as high density optical storage and memory materials, thermovoltaic devices, infrared sensors and more. We discuss the electronic, optical and magnetic properties of SmS, its switching behavior, as well as the thin film deposition techniques which have been used, such as e-beam evaporation and sputtering. Moreover, applications and possible ideas for future work on this material are presented. Our scope is to present the properties of SmS, which were mainly measured in bulk crystals, while at the same time we describe the possible deposition methods that will push the study of SmS to nanoscale dimensions, opening an intriguing range of applications for low-dimensional, pressure-induced semiconductor–metal transition compounds. Full article

(This article belongs to the Section Advanced Materials Characterization)

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21 pages, 2017 KiB

Open AccessFeature PaperReview

Measurement Techniques of the Magneto-Electric Coupling in Multiferroics

by M. M. Vopson^1,*

, Y. K. Fetisov², G. Caruntu³ and G. Srinivasan⁴

¹ School of Earth and Environmental Sciences, Faculty of Science, University of Portsmouth, Portsmouth PO1 3QL, UK

² Moscow Technological University, MIREA, Moscow 119454, Russia

³ Department of Chemistry and Biochemistry, Central Michigan University, 1200 S. Franklin St., Mount Pleasant, MI 48858, USA

⁴ Physics Department, Oakland University, Rochester, MI 48309-4401, USA

Materials 2017, 10(8), 963; https://doi.org/10.3390/ma10080963 - 17 Aug 2017

Cited by 96 | Viewed by 10011

Abstract

The current surge of interest in multiferroic materials demands specialized measurement techniques to support multiferroics research. In this review article we detail well-established measurement techniques of the magneto-electric coupling coefficient in multiferroic materials, together with newly proposed ones. This work is intended to [...] Read more.

The current surge of interest in multiferroic materials demands specialized measurement techniques to support multiferroics research. In this review article we detail well-established measurement techniques of the magneto-electric coupling coefficient in multiferroic materials, together with newly proposed ones. This work is intended to serve as a reference document for anyone willing to develop experimental measurement techniques of multiferroic materials. Full article

(This article belongs to the Special Issue Physics, Measurements and Applications of Multiferroic and Magnetoelectric Materials)

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31 pages, 4043 KiB

Open AccessFeature PaperReview

Potential Applications of Nanocellulose-Containing Materials in the Biomedical Field

by Nadia Halib¹

, Francesca Perrone², Maja Cemazar³

, Barbara Dapas², Rossella Farra⁴, Michela Abrami⁴, Gianluca Chiarappa⁴, Giancarlo Forte⁵, Fabrizio Zanconati⁶, Gabriele Pozzato⁶, Luigi Murena⁶, Nicola Fiotti⁶

, Romano Lapasin⁴, Laura Cansolino⁷, Gabriele Grassi^2,* and Mario Grassi⁴

¹ Department of Basic Sciences & Oral Biology, Faculty of Dentistry, Universiti Sains Islam Malaysia, Level 15, Tower B, Persiaran MPAJ, Jalan Pandan Utama, Kuala Lumpur 55100, Malaysia;

² Department of Life Sciences, Cattinara University Hospital, Trieste University, Strada di Fiume 447, I-34149 Trieste, Italy

³ Institute of Oncology Ljubljana, Zaloska 2, SI-1000 Ljubljana, Slovenia

⁴ Department of Engineering and Architecture, University of Trieste, Via Valerio 6/A, I-34127 Trieste, Italy

⁵ Center for Translational Medicine, International Clinical Research Center, St. Anne’s University Hospital, Pekarska 53, 656 91 Brno, Czech Republic

⁶ Surgery and Health Sciences, Department of Medical, Cattinara Hospital, University of Trieste, I-34127 Trieste, Italy

⁷ Department of Clinico-Surgical Sciences, Experimental Surgery Laboratory, University of Pavia and IRCCS S, Matteo Hospital Pavia, 27100 Pavia, Italy

Materials 2017, 10(8), 977; https://doi.org/10.3390/ma10080977 - 21 Aug 2017

Cited by 137 | Viewed by 11819

Abstract

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition [...] Read more.

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition of cellulose fibers, the cellulose sources/features and cellulose chemical modifications employed to improve its properties. We then move to the description of cellulose potential applications in biomedicine. In this field, cellulose is most considered in recent research in the form of nano-sized particle, i.e., nanofiber cellulose (NFC) or cellulose nanocrystal (CNC). NFC is obtained from cellulose via chemical and mechanical methods. CNC can be obtained from macroscopic or microscopic forms of cellulose following strong acid hydrolysis. NFC and CNC are used for several reasons including the mechanical properties, the extended surface area and the low toxicity. Here we present some potential applications of nano-sized cellulose in the fields of wound healing, bone-cartilage regeneration, dental application and different human diseases including cancer. To witness the close proximity of nano-sized cellulose to the practical biomedical use, examples of recent clinical trials are also reported. Altogether, the described examples strongly support the enormous application potential of nano-sized cellulose in the biomedical field. Full article

(This article belongs to the Special Issue Nanocellulose-Based Functional Materials)

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