Materials

Editorial

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3 pages, 159 KiB

Open AccessEditorial

Special Issue: Materials for Electrochemical Capacitors and Batteries

by Jian-Gan Wang^1,*

and Bingqing Wei^1,2,*

¹ State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, School of Materials Science and Engineering, Northwestern Polytechnical University and Shaanxi Joint Lab of Graphene (NPU), Xi’an 710072, China

² Department of Mechanical Engineering, University of Delaware, Newark, DE19716, USA

Materials 2017, 10(4), 438; https://doi.org/10.3390/ma10040438 - 22 Apr 2017

Cited by 4 | Viewed by 4335

Abstract

Electrochemical capacitors and rechargeable batteries have received worldwide attention due to their excellent energy storage capability for a variety of applications. The rapid development of these technologies is propelled by the advanced electrode materials and new energy storage systems. It is believed that [...] Read more.

Electrochemical capacitors and rechargeable batteries have received worldwide attention due to their excellent energy storage capability for a variety of applications. The rapid development of these technologies is propelled by the advanced electrode materials and new energy storage systems. It is believed that research efforts can improve the device performance to meet the ever-increasing requirements of high energy density, high power density and long cycle life. This Special Issue aims to provide readers with a glimpse of different kinds of electrode materials for electrochemical capacitors and batteries. Full article

(This article belongs to the Special Issue Materials for Electrochemical Capacitors and Batteries)

Research

Jump to: Editorial, Review

13 pages, 7374 KiB

Open AccessArticle

New Bio-Composites Based on Polyhydroxyalkanoates and Posidonia oceanica Fibres for Applications in a Marine Environment

by Maurizia Seggiani^1,*

, Patrizia Cinelli^1,2,*, Norma Mallegni¹, Elena Balestri³, Monica Puccini¹

, Sandra Vitolo¹

, Claudio Lardicci³ and Andrea Lazzeri¹

¹ Department of Civil and Industrial Engineering, University of Pisa, Largo Lucio Lazzarino 1, Pisa 56126, Italy

² Institute for the Chemical and Physical Processes, National Research Council, Via Moruzzi 1, Pisa 56124, Italy

³ Department of Biology, University of Pisa, Via Derna 1, Pisa 56126, Italy

Materials 2017, 10(4), 326; https://doi.org/10.3390/ma10040326 - 23 Mar 2017

Cited by 70 | Viewed by 6082

Abstract

Bio-composites based on polyhydroxyalkanoates (PHAs) and fibres of Posidonia oceanica (PO) were investigated to assess their processability by extrusion, mechanical properties, and potential biodegradability in a natural marine environment. PHAs were successfully compounded with PO fibres up to 20 wt % while, at [...] Read more.

Bio-composites based on polyhydroxyalkanoates (PHAs) and fibres of Posidonia oceanica (PO) were investigated to assess their processability by extrusion, mechanical properties, and potential biodegradability in a natural marine environment. PHAs were successfully compounded with PO fibres up to 20 wt % while, at 30 wt % of fibres, the addition of 10 wt % of polyethylene glycol (PEG 400) was necessary to improve their processability. Thermal, rheological, mechanical, and morphological characterizations of the developed composites were conducted and the degradation of composite films in a natural marine habitat was evaluated in a mesocosm by weight loss measure during an incubation period of six months. The addition of PO fibres led to an increase in stiffness of the composites with tensile modulus values about 80% higher for composites with 30 wt % fibre (2.3 GPa) compared to unfilled material (1.24 GPa). Furthermore, the impact energy markedly increased with the addition of the PO fibres, from 1.63 (unfilled material) to 3.8 kJ/m² for the composites with 30 wt % PO. The rate of degradation was markedly influenced by seawater temperature and significantly promoted by the presence of PO fibres leading to the total degradation of the film with 30 wt % PO in less than six months. The obtained results showed that the developed composites can be suitable to manufacture items usable in marine environments, for example, in natural engineering interventions, and represent an interesting valorisation of the PO fibrous wastes accumulated in large amounts on coastal beaches. Full article

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8 pages, 13217 KiB

Open AccessArticle

Cu₆Sn₅ Whiskers Precipitated in Sn3.0Ag0.5Cu/Cu Interconnection in Concentrator Silicon Solar Cells Solder Layer

by Liang Zhang^1,2,*

, Zhi-quan Liu²

, Fan Yang¹

and Su-juan Zhong³

¹ School of Mechatronic Engineering, Jiangsu Normal University, Xuzhou 221116, China

² Institute of Metal Research, Chinese Academy of Science, Shenyang 110016, China

³ State Key Laboratory of Advanced Brazing Filler Metals & Technology, Zhengzhou Research Institute of Mechanical Engineering, Zhengzhou 450001, China

Materials 2017, 10(4), 327; https://doi.org/10.3390/ma10040327 - 23 Mar 2017

Cited by 14 | Viewed by 5033

Abstract

Cu₆Sn₅ whiskers precipitated in Sn3.0Ag0.5Cu/Cu interconnection in concentrator silicon solar cells solder layer were found and investigated after reflow soldering and during aging. Ag₃Sn fibers can be observed around Cu₆Sn₅ whiskers in the matrix microstructure, [...] Read more.

Cu₆Sn₅ whiskers precipitated in Sn3.0Ag0.5Cu/Cu interconnection in concentrator silicon solar cells solder layer were found and investigated after reflow soldering and during aging. Ag₃Sn fibers can be observed around Cu₆Sn₅ whiskers in the matrix microstructure, which can play an active effect on the reliability of interconnection. Different morphologies of Cu₆Sn₅ whiskers can be observed, and hexagonal rod structure is the main morphology of Cu₆Sn₅ whiskers. A hollow structure can be observed in hexagonal Cu₆Sn₅ whiskers, and a screw dislocation mechanism was used to represent the Cu₆Sn₅ growth. Based on mechanical property testing and finite element simulation, Cu₆Sn₅ whiskers were regarded as having a negative effect on the durability of Sn3.0Ag0.5Cu/Cu interconnection in concentrator silicon solar cells solder layer. Full article

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14 pages, 4726 KiB

Open AccessArticle

Thermoelectric Properties of Highly-Crystallized Ge-Te-Se Glasses Doped with Cu/Bi

by Bhuvanesh Srinivasan¹

, Catherine Boussard-Pledel¹, Vincent Dorcet², Manisha Samanta³, Kanishka Biswas³, Robin Lefèvre⁴, Franck Gascoin⁴, François Cheviré¹

, Sylvain Tricot⁵, Michael Reece⁶ and Bruno Bureau^1,*

¹ Équipe Verres et Céramiques, ISCR CNRS UMR 6226, Université de Rennes 1, Rennes 35042, France

² PRATS, ISCR CNRS UMR 6226, Université de Rennes 1, Rennes 35042, France

³ New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India

⁴ ENSICAEN, UNICAEN, CNRS, IUT-Caen, CRISMAT, Normandie Université, Caen 14050, France

⁵ Institut de Physique de Rennes, CNRS UMR 6251-Université de Rennes 1, Rennes 35042, France

⁶ School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK

Materials 2017, 10(4), 328; https://doi.org/10.3390/ma10040328 - 23 Mar 2017

Cited by 30 | Viewed by 7353

Abstract

Chalcogenide semiconducting systems are of growing interest for mid-temperature range (~500 K) thermoelectric applications. In this work, Ge₂₀Te₇₇Se₃ glasses were intentionally crystallized by doping with Cu and Bi. These effectively-crystallized materials of composition (Ge₂₀Te₇₇Se [...] Read more.

Chalcogenide semiconducting systems are of growing interest for mid-temperature range (~500 K) thermoelectric applications. In this work, Ge₂₀Te₇₇Se₃ glasses were intentionally crystallized by doping with Cu and Bi. These effectively-crystallized materials of composition (Ge₂₀Te₇₇Se₃)_100−xM_x (M = Cu or Bi; x = 5, 10, 15), obtained by vacuum-melting and quenching techniques, were found to have multiple crystalline phases and exhibit increased electrical conductivity due to excess hole concentration. These materials also have ultra-low thermal conductivity, especially the heavily-doped (Ge₂₀Te₇₇Se₃)_100−xBi_x (x = 10, 15) samples, which possess lattice thermal conductivity of ~0.7 Wm⁻¹ K⁻¹ at 525 K due to the assumable formation of nano-precipitates rich in Bi, which are effective phonon scatterers. Owing to their high metallic behavior, Cu-doped samples did not manifest as low thermal conductivity as Bi-doped samples. The exceptionally low thermal conductivity of the Bi-doped materials did not, alone, significantly enhance the thermoelectric figure of merit, zT. The attempt to improve the thermoelectric properties by crystallizing the chalcogenide glass compositions by excess doping did not yield power factors comparable with the state of the art thermoelectric materials, as these highly electrically conductive crystallized materials could not retain the characteristic high Seebeck coefficient values of semiconducting telluride glasses. Full article

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

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17 pages, 3885 KiB

Open AccessArticle

Electric Field-Driven Assembly of Sulfonated Polystyrene Microspheres

by Alexander Mikkelsen¹

, Jarosław Wojciechowski², Michal Rajňák^3,4

, Juraj Kurimský⁴

, Khobaib Khobaib¹, Ahmet Kertmen⁵

and Zbigniew Rozynek^1,*

¹ Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland

² Department of Chemistry, University of Warsaw, Ludwika Pasteura 1, 02-093 Warsaw, Poland

³ Institute of Experimental Physics SAS, Watsonova 47, 040-01 Kosice, Slovakia

⁴ Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice, Slovakia

⁵ Faculty of Chemistry, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland

Materials 2017, 10(4), 329; https://doi.org/10.3390/ma10040329 - 23 Mar 2017

Cited by 21 | Viewed by 7069

Abstract

A designed assembly of particles at liquid interfaces offers many advantages for development of materials, and can be performed by various means. Electric fields provide a flexible method for structuring particles on drops, utilizing electrohydrodynamic circulation flows, and dielectrophoretic and electrophoretic interactions. In [...] Read more.

A designed assembly of particles at liquid interfaces offers many advantages for development of materials, and can be performed by various means. Electric fields provide a flexible method for structuring particles on drops, utilizing electrohydrodynamic circulation flows, and dielectrophoretic and electrophoretic interactions. In addition to the properties of the applied electric field, the manipulation of particles often depends on the intrinsic properties of the particles to be assembled. Here, we present an easy approach for producing polystyrene microparticles with different electrical properties. These particles are used for investigations into electric field-guided particle assembly in the bulk and on surfaces of oil droplets. By sulfonating polystyrene particles, we produce a set of particles with a range of dielectric constants and electrical conductivities, related to the sulfonation reaction time. The paper presents diverse particle behavior driven by electric fields, including particle assembly at different droplet locations, particle chaining, and the formation of ribbon-like structures with anisotropic properties. Full article

(This article belongs to the Special Issue Designed Colloidal Self-Assembly)

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14 pages, 13775 KiB

Open AccessArticle

The Wear Behavior of Textured Steel Sliding against Polymers

by Meiling Wang^*, Changtao Zhang and Xiaolei Wang^*

College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Materials 2017, 10(4), 330; https://doi.org/10.3390/ma10040330 - 23 Mar 2017

Cited by 26 | Viewed by 5524

Abstract

Artificially fabricated surface textures can significantly improve the friction and wear resistance of a tribological contact. Recently, this surface texturing technique has been applied to polymer materials to improve their tribological performance. However, the wear behavior of textured tribo-pairs made of steel and [...] Read more.

Artificially fabricated surface textures can significantly improve the friction and wear resistance of a tribological contact. Recently, this surface texturing technique has been applied to polymer materials to improve their tribological performance. However, the wear behavior of textured tribo-pairs made of steel and polymer materials has been less thoroughly investigated and is not well understood; thus, it needs further research. The aim of this study is to investigate the wear properties of tribological contacts made of textured stainless steel against polymer surfaces. Three polymer materials were selected in this study, namely, ultrahigh molecular weight polyethylene (UHMWPE), polyoxymethylene (POM) and (polyetheretherketone) PEEK. Wear tests were operated through a ring-on-plane mode. The results revealed that the texture features and material properties affected the wear rates and friction coefficients of the textured tribo-pairs. In general, PEEK/textured steel achieved the lowest wear rate among the three types of tribo-pairs investigated. Energy dispersive x-ray spectroscopy (EDX) analysis revealed that the elements of C and O on the contacting counterfaces varied with texture features and indicated different wear behavior. Experimental and simulated results showed differences in the stress distribution around the dimple edge, which may influence wear performance. Wear debris with different surface morphologies were found for tribo-pairs with varying texture features. This study has increased the understanding of the wear behavior of tribo-pairs between textured stainless steel and polymer materials. Full article

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

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13 pages, 6616 KiB

Open AccessArticle

Photocatalytic Water Splitting for O₂ Production under Visible Light Irradiation Using NdVO₄-V₂O₅ Hybrid Powders

by Tzu Hsuan Chiang^*

and Tso-Ming Chen

Department of Energy Engineering, National United University, Lienda, Nan-Shi Li, Miaoli 36006, Taiwan

Materials 2017, 10(4), 331; https://doi.org/10.3390/ma10040331 - 23 Mar 2017

Cited by 9 | Viewed by 4858

Abstract

The study investigated photocatalytic water splitting for O₂ production under visible light irradiation using neodymium vanadium oxide (NdVO₄) and vanadium oxide (V₂O₅) hybrid powders. The results in a sacrificial agent of 0.01 M AgNO₃ solution [...] Read more.

The study investigated photocatalytic water splitting for O₂ production under visible light irradiation using neodymium vanadium oxide (NdVO₄) and vanadium oxide (V₂O₅) hybrid powders. The results in a sacrificial agent of 0.01 M AgNO₃ solution were obtained, and the highest photocatalytic O₂ evolution was 2.63 μmol/h, when the hybrid powders were prepared by mixing Nd and V at a volume ratio of 1:3 at a calcination temperature of 350 °C for 1 h. The hybrid powders were synthesized by neodymium nitrate and ammonium metavanadate using the glycothermal method in ethylene glycol at 120 °C for 1 h. The hybrid powders consisted of two shapes, NdVO₄ nanoparticles and the cylindrical V₂O₅ particles, and they possessed the ability for photocatalytic oxygen (O₂) evolution during irradiation with visible light. The band gaps and structures of the hybrid powders were analyzed using UV-visible spectroscopy and transmission electron microscopy. Full article

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

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12 pages, 1001 KiB

Open AccessFeature PaperArticle

Codoping and Interstitial Deactivation in the Control of Amphoteric Li Dopant in ZnO for the Realization of p-Type TCOs

by Alessandra Catellani and Arrigo Calzolari^*

CNR-NANO Istituto Nanoscienze, Centro S3, via Campi 213A, I-41125 Modena, Italy

Materials 2017, 10(4), 332; https://doi.org/10.3390/ma10040332 - 23 Mar 2017

Cited by 14 | Viewed by 4924

Abstract

We report on first principle investigations about the electrical character of Li-X codoped ZnO transparent conductive oxides (TCOs). We studied a set of possible X codopants including either unintentional dopants typically present in the system (e.g., H, O) or monovalent acceptor groups, based [...] Read more.

We report on first principle investigations about the electrical character of Li-X codoped ZnO transparent conductive oxides (TCOs). We studied a set of possible X codopants including either unintentional dopants typically present in the system (e.g., H, O) or monovalent acceptor groups, based on nitrogen and halogens (F, Cl, I). The interplay between dopants and structural point defects in the host (such as vacancies) is also taken explicitly into account, demonstrating the crucial effect that zinc and oxygen vacancies have on the final properties of TCOs. Our results show that Li-ZnO has a p-type character, when Li is included as Zn substitutional dopant, but it turns into an n-type when Li is in interstitial sites. The inclusion of X-codopants is considered to deactivate the n-type character of interstitial Li atoms: the total Li-X compensation effect and the corresponding electrical character of the doped compounds selectively depend on the presence of vacancies in the host. We prove that LiF-doped ZnO is the only codoped system that exhibits a p-type character in the presence of Zn vacancies. Full article

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

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12 pages, 6331 KiB

Open AccessArticle

Manufacturing Feasibility and Forming Properties of Cu-4Sn in Selective Laser Melting

by Zhongfa Mao¹, David Z. Zhang^1,2,*, Peitang Wei¹ and Kaifei Zhang¹

¹ State Key Laboratory on Mechanical Transmission, Chongqing University, Chongqing 400044, China

² College of Engineering, Mathematics and Physical Sciences, University of Exeter, North Park Road, Exeter EX4 4QF, UK

Materials 2017, 10(4), 333; https://doi.org/10.3390/ma10040333 - 24 Mar 2017

Cited by 63 | Viewed by 6901

Abstract

Copper alloys, combined with selective laser melting (SLM) technology, have attracted increasing attention in aerospace engineering, automobile, and medical fields. However, there are some difficulties in SLM forming owing to low laser absorption and excellent thermal conductivity. It is, therefore, necessary to explore [...] Read more.

Copper alloys, combined with selective laser melting (SLM) technology, have attracted increasing attention in aerospace engineering, automobile, and medical fields. However, there are some difficulties in SLM forming owing to low laser absorption and excellent thermal conductivity. It is, therefore, necessary to explore a copper alloy in SLM. In this research, manufacturing feasibility and forming properties of Cu-4Sn in SLM were investigated through a systematic experimental approach. Single-track experiments were used to narrow down processing parameter windows. A Greco-Latin square design with orthogonal parameter arrays was employed to control forming qualities of specimens. Analysis of variance was applied to establish statistical relationships, which described the effects of different processing parameters (i.e., laser power, scanning speed, and hatch space) on relative density (RD) and Vickers hardness of specimens. It was found that Cu-4Sn specimens were successfully manufactured by SLM for the first time and both its RD and Vickers hardness were mainly determined by the laser power. The maximum value of RD exceeded 93% theoretical density and the maximum value of Vickers hardness reached 118 HV 0.3/5. The best tensile strength of 316–320 MPa is inferior to that of pressure-processed Cu-4Sn and can be improved further by reducing defects. Full article

(This article belongs to the Special Issue Metals for Additive Manufacturing)

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12 pages, 3643 KiB

Open AccessArticle

Effect of Immobilized Antithrombin III on the Thromboresistance of Polycarbonate Urethane

by Karin Lukas¹, Karin Stadtherr¹, Andre Gessner¹, Daniel Wehner², Thomas Schmid², Hans Peter Wendel³, Christof Schmid⁴ and Karla Lehle^4,*

¹ IMHR, Institute for Medical Microbiology and Hygiene, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany

² Dualis Medtech GmbH, Am Technologiepark 8+10, 82229 Seefeld, Germany

³ Department of Thoracic, Cardiac, and Vascular Surgery, University Hospital Tübingen, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany

⁴ Department of Cardiothoracic Surgery, University Medical Center Regensburg, Josef-Strauss-Allee 11, 93042 Regensburg, Germany

Materials 2017, 10(4), 335; https://doi.org/10.3390/ma10040335 - 24 Mar 2017

Cited by 1 | Viewed by 4612

Abstract

The surface of foils and vascular grafts made from a thermoplastic polycarbonate urethanes (PCU) (Chronoflex AR) were chemically modified using gas plasma treatment, binding of hydrogels—(1) polyethylene glycol bisdiamine and carboxymethyl dextran (PEG-DEX) and (2) polyethyleneimine (PEI)—and immobilization of human antithrombin III (AT). [...] Read more.

The surface of foils and vascular grafts made from a thermoplastic polycarbonate urethanes (PCU) (Chronoflex AR) were chemically modified using gas plasma treatment, binding of hydrogels—(1) polyethylene glycol bisdiamine and carboxymethyl dextran (PEG-DEX) and (2) polyethyleneimine (PEI)—and immobilization of human antithrombin III (AT). Their biological impact was tested in vitro under static and dynamic conditions. Static test methods showed a significantly reduced adhesion of endothelial cells, platelets, and bacteria, compared to untreated PCU. Modified PCU grafts were circulated in a Chandler-Loop model for 90 min at 37 °C with human blood. Before and after circulation, parameters of the hemostatic system (coagulation, platelets, complement, and leukocyte activation) were analyzed. PEI-AT significantly inhibited the activation of both coagulation and platelets and prevented the activation of leukocytes and complement. In conclusion, both modifications significantly reduce coagulation activation, but only PEI-AT creates anti-bacterial and anti-thrombogenic functionality. Full article

(This article belongs to the Section Biomaterials)

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13 pages, 3483 KiB

Open AccessCommunication

Tracing the Bioavailability of Three-Dimensional Graphene Foam in Biological Tissues

by Tanveer A. Tabish¹, Sakineh Chabi^1,2, Muhammad Ali³, Yongde Xia¹, Farhat Jabeen³ and Shaowei Zhang^1,*

¹ College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK

² Department of Chemistry, Florida Institute of Technology, 150 W University Blvd, Melbourne, FL 3290, USA

³ Department of Zoology, Government College University, Faisalabad 3800, Pakistan

Materials 2017, 10(4), 336; https://doi.org/10.3390/ma10040336 - 24 Mar 2017

Cited by 27 | Viewed by 5361

Abstract

Graphene-based materials with a three-dimensional (3D) framework have been investigated for a variety of biomedical applications because of their 3D morphology, excellent physiochemical properties, volume stability, and their controllable degradation rate. Current knowledge on the toxicological implications and bioavailability of graphene foam (GF) [...] Read more.

Graphene-based materials with a three-dimensional (3D) framework have been investigated for a variety of biomedical applications because of their 3D morphology, excellent physiochemical properties, volume stability, and their controllable degradation rate. Current knowledge on the toxicological implications and bioavailability of graphene foam (GF) has major uncertainties surrounding the fate and behavior of GF in exposed environments. Bioavailability, uptake, and partitioning could have potential effects on the behavior of GF in living organisms, which has not yet been investigated. Here, we report a pilot toxicology study on 3D GF in common carps. Our results showed that GF did not show any noticeable toxicity in common carps, and the antioxidant enzymatic activities, biochemical and blood parameters persisted within the standard series. Further histological imaging revealed that GF remained within liver and kidney macrophages for 7 days without showing obvious toxicity. An in vivo study also demonstrated a direct interaction between GF and biological systems, verifying its eco-friendly nature and high biocompatibility. Full article

(This article belongs to the Special Issue Bioapplications of Graphene Composites)

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9 pages, 5954 KiB

Open AccessArticle

The Mechanical Strength of Si Foams in the Mushy Zone during Solidification of Al–Si Alloys

by Jeon Taik Lim, Ji Won Youn, Seok Yong Seo, Ki Young Kim and Suk Jun Kim^*

School of Energy, Materials and Chemical Engineering, Korea University of Technology and Education (KOREATECH), Cheonan 31253, Korea

Materials 2017, 10(4), 337; https://doi.org/10.3390/ma10040337 - 24 Mar 2017

Cited by 1 | Viewed by 3081

Abstract

The mechanical strength of an Al-30% Si alloy in the mushy zone was estimated by using a novel centrifugation apparatus. In the apparatus, the alloy melt was partially solidified, forming a porous structure made of primary Si platelets (Si foam) while cooling. Subsequently, [...] Read more.

The mechanical strength of an Al-30% Si alloy in the mushy zone was estimated by using a novel centrifugation apparatus. In the apparatus, the alloy melt was partially solidified, forming a porous structure made of primary Si platelets (Si foam) while cooling. Subsequently, pressure generated by centrifugal force pushed the liquid phase out of the foam. The estimated mechanical strength of the Si foam in the temperature range 850–993 K was very low (62 kPa to 81 kPa). This is about two orders of magnitude lower than the mechanical strength at room temperature as measured by compressive tests. When the centrifugal stress was higher than the mechanical strength of the foam, the foam fractured, and the primary Si crystallites were extracted along with the Al-rich melt. Therefore, to maximize the centrifugal separation efficiency of the Al-30% Si alloy, the centrifugal stress should be in the range of 62–81 kPa. Full article

(This article belongs to the Section Advanced Materials Characterization)

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17 pages, 2870 KiB

Open AccessArticle

A Series of Robust Copper-Based Triazolyl Isophthalate MOFs: Impact of Linker Functionalization on Gas Sorption and Catalytic Activity †

by Ulrike Junghans¹, Merten Kobalz², Oliver Erhart², Hannes Preißler³, Jörg Lincke², Jens Möllmer³, Harald Krautscheid² and Roger Gläser^1,3,*

¹ Institute of Chemical Technology, Universität Leipzig, Linnéstr. 3, 04103 Leipzig, Germany

² Institute of Inorganic Chemistry, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany

³ Institut für Nichtklassische Chemie e.V., Permoserstr. 15, 04318 Leipzig, Germany

Materials 2017, 10(4), 338; https://doi.org/10.3390/ma10040338 - 24 Mar 2017

Cited by 12 | Viewed by 5345

Abstract

The synthesis and characterization of an isomorphous series of copper-containing microporous metal-organic frameworks (MOFs) based on triazolyl isophthalate linkers with the general formula [Cu₄(μ₃-OH)₂(R¹-R²-trz-ia)₃(H₂O)_x] are presented. [...] Read more.

The synthesis and characterization of an isomorphous series of copper-containing microporous metal-organic frameworks (MOFs) based on triazolyl isophthalate linkers with the general formula [Cu₄(μ₃-OH)₂(R¹-R²-trz-ia)₃(H₂O)_x] are presented. Through size adjustment of the alkyl substituents R¹ and/or R² at the linker, the impact of linker functionalization on structure-property relationships was studied. Due to the arrangement of the substituents towards the cavities, the porosity (pore fraction 28%–39%), as well as the pore size can be adjusted by the size of the substituents of the triazole ring. Thermal analysis and temperature-dependent PXRD studies reveal a thermal stability of the MOFs up to 230 °C due to increasing framework stability through fine-tuning of the linker substitution pattern. Adsorption of CO₂ (298 K) shows a decreasing maximum loading with increasing steric demand of the substituents of the triazole ring. Furthermore, the selective oxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) is studied over the MOFs at 323 K in liquid chloroform. The catalytic activity increases with the steric demand of the substituents. Additionally, these isomorphous MOFs exhibit considerable robustness under oxidizing conditions confirmed by CO₂ adsorption studies, as well as by the catalytic selective oxidation experiments. Full article

(This article belongs to the Section Porous Materials)

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6 pages, 5481 KiB

Open AccessArticle

Development and Application of Wood Flour-Filled Polylactic Acid Composite Filament for 3D Printing

by Yubo Tao¹, Honglei Wang¹, Zelong Li², Peng Li^1,*

and Sheldon Q. Shi³

¹ College of Material Science and Engineering, Northeast Forestry University, Harbin 150040, China

² Denton High School, Denton, TX 76203, USA

³ Department of Mechanical and Energy Engineering, University of North Texas, Denton, TX 76203, USA

Materials 2017, 10(4), 339; https://doi.org/10.3390/ma10040339 - 24 Mar 2017

Cited by 302 | Viewed by 15715

Abstract

This paper presents the development of wood flour (WF)-filled polylactic acid (PLA) composite filaments for a fused deposition modeling (FDM) process with the aim of application to 3D printing. The composite filament consists of wood flour (5 wt %) in a PLA matrix. [...] Read more.

This paper presents the development of wood flour (WF)-filled polylactic acid (PLA) composite filaments for a fused deposition modeling (FDM) process with the aim of application to 3D printing. The composite filament consists of wood flour (5 wt %) in a PLA matrix. The detailed formulation and characterization of the composite filament were investigated experimentally, including tensile properties, microstructure, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The feedstock filaments of this composite were produced and used successfully in an assembled FDM 3D printer. The research concludes that compared with pure PLA filament, adding WF changed the microstructure of material fracture surface, the initial deformation resistance of the composite was enhanced, the starting thermal degradation temperature of the composite decreased slightly, and there were no effects on the melting temperature. The WF/PLA composite filament is suitable to be printed by the FDM process. Full article

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12 pages, 1489 KiB

Open AccessArticle

A Photoluminescence Study of the Changes Induced in the Zinc White Pigment by Formation of Zinc Complexes

by Alessia Artesani^1,*

, Francesca Gherardi²

, Austin Nevin³

, Gianluca Valentini¹

and Daniela Comelli¹

¹ Physics Department, Politecnico di Milano, Piazza Leonardo da Vinci, 20133 Milano, Italy

² Chemistry, Materials and Chemical Engineering “Giulio Natta” Department, Politecnico di Milano, Piazza Leonardo da Vinci, 20133 Milano, Italy

³ Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci, 20133 Milano, Italy

Materials 2017, 10(4), 340; https://doi.org/10.3390/ma10040340 - 25 Mar 2017

Cited by 31 | Viewed by 6870

Abstract

It is known that oil paintings containing zinc white are subject to rapid degradation. This is caused by the interaction between the active groups of binder and the metal ions of the pigment, which gives rise to the formation of new zinc complexes [...] Read more.

It is known that oil paintings containing zinc white are subject to rapid degradation. This is caused by the interaction between the active groups of binder and the metal ions of the pigment, which gives rise to the formation of new zinc complexes (metal soaps). Ongoing studies on zinc white paints have been limited to the chemical mechanisms that lead to the formation of zinc complexes. On the contrary, little is known of the photo-physical changes induced in the zinc oxide crystal structure following this interaction. Time-resolved photoluminescence spectroscopy has been applied to follow modifications in the luminescent zinc white pigment when mixed with binder. Significant changes in trap state photoluminescence emissions have been detected: the enhancement of a blue emission combined with a change of the decay kinetic of the well-known green emission. Complementary data from molecular analysis of paints using Fourier transform infrared spectroscopy confirms the formation of zinc carboxylates and corroborates the mechanism for zinc complexes formation. We support the hypothesis that zinc ions migrate into binder creating novel vacancies, affecting the photoluminescence intensity and lifetime properties of zinc oxide. Here, we further demonstrate the advantages of a time-resolved photoluminescence approach for studying defects in semiconductor pigments. Full article

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

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18 pages, 3762 KiB

Open AccessArticle

Laser Engineered Net Shaping of Nickel-Based Superalloy Inconel 718 Powders onto AISI 4140 Alloy Steel Substrates: Interface Bond and Fracture Failure Mechanism

by Hoyeol Kim^1,*

, Weilong Cong¹, Hong-Chao Zhang^1,2 and Zhichao Liu^1,2

¹ Department of Industrial, Manufacturing and Systems Engineering, Texas Tech University, Lubbock, TX 79409, USA

² School of Mechanical Engineering, Dalian University of Technology, Dalian 116023, China

Materials 2017, 10(4), 341; https://doi.org/10.3390/ma10040341 - 25 Mar 2017

Cited by 42 | Viewed by 8549

Abstract

As a prospective candidate material for surface coating and repair applications, nickel-based superalloy Inconel 718 (IN718) was deposited on American Iron and Steel Institute (AISI) 4140 alloy steel substrate by laser engineered net shaping (LENS) to investigate the compatibility between two dissimilar materials [...] Read more.

As a prospective candidate material for surface coating and repair applications, nickel-based superalloy Inconel 718 (IN718) was deposited on American Iron and Steel Institute (AISI) 4140 alloy steel substrate by laser engineered net shaping (LENS) to investigate the compatibility between two dissimilar materials with a focus on interface bonding and fracture behavior of the hybrid specimens. The results show that the interface between the two dissimilar materials exhibits good metallurgical bonding. Through the tensile test, all the fractures occurred in the as-deposited IN718 section rather than the interface or the substrate, implying that the as-deposited interlayer bond strength is weaker than the interfacial bond strength. From the fractography using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS), three major factors affecting the tensile fracture failure of the as-deposited part are (i) metallurgical defects such as incompletely melted powder particles, lack-of-fusion porosity, and micropores; (ii) elemental segregation and Laves phase, and (iii) oxide formation. The fracture failure mechanism is a combination of all these factors which are detrimental to the mechanical properties and structural integrity by causing premature fracture failure of the as-deposited IN718. Full article

(This article belongs to the Special Issue Metals for Additive Manufacturing)

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20 pages, 3197 KiB

Open AccessArticle

Role of Tartaric Acid in Chemical, Mechanical and Self-Healing Behaviors of a Calcium-Aluminate Cement Blend with Fly Ash F under Steam and Alkali Carbonate Environments at 270 °C

by Tatiana Pyatina^* and Toshifumi Sugama

Brookhaven National Laboratory, Upton, NY 11973-5000, USA

Materials 2017, 10(4), 342; https://doi.org/10.3390/ma10040342 - 25 Mar 2017

Cited by 12 | Viewed by 5005

Abstract

Tartaric acid (TA) changes short-term mechanical behavior and phase composition of sodium-metasilicate activated calcium-aluminate cement blend with fly ash, type F, when used as a set control additive to allow sufficient pumping time for underground well placement. The present work focuses on TA [...] Read more.

Tartaric acid (TA) changes short-term mechanical behavior and phase composition of sodium-metasilicate activated calcium-aluminate cement blend with fly ash, type F, when used as a set control additive to allow sufficient pumping time for underground well placement. The present work focuses on TA effect on self-healing properties of the blend under steam or alkali carbonate environments at 270 °C applicable to geothermal wells. Compressive strength recoveries and cracks sealing were examined to evaluate self-healing of the cement after repeated crush tests followed by two consecutive healing periods of 10 and 5 days at 270 °C. Optical and scanning electron microscopes, X-ray diffraction, Fourier Transform infrared and EDX measurements along with thermal gravimetric analyses were used to identify phases participating in the healing processes. Samples with 1% mass fraction of TA by weight of blend demonstrated improved strength recoveries and crack plugging properties, especially in alkali carbonate environment. This effect was attributed to silicon-rich (C,N)-A-S-H amorphous phase predominant in TA-modified samples, high-temperature stable zeolite phases along with the formation of tobermorite-type crystals in the presence of tartaric acid. Full article

(This article belongs to the Section Advanced Composites)

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20 pages, 6621 KiB

Open AccessArticle

Chitosan and β-Cyclodextrin-epichlorohydrin Polymer Composite Film as a Plant Healthcare Material for Carbendazim-Controlled Release to Protect Rape against Sclerotinia sclerotiorum (Lib.) de Bary

by Delong Wang¹

, Mingchen Jia², Lanying Wang³, Shuang Song¹, Juntao Feng^1,* and Xing Zhang¹

¹ Research and Development Center of Biorational Pesticide, Shaanxi Research Center of Biopesticide Engineering & Technology, Key Laboratory of Plant Protection Resources and Pest Management of Ministry of Education, Northwest A & F University, Yangling 712100, Shaanxi, China

² Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China

³ College of Environment and Plant Protection, Hainan University, Haikou 570228, Hainan, China

Materials 2017, 10(4), 343; https://doi.org/10.3390/ma10040343 - 26 Mar 2017

Cited by 24 | Viewed by 7338

Abstract

The influence of β-cyclodextrin-epichlorohydrin (β-CD-EP) polymers on the improvement of the solubility and antifungal activity of carbendazim has been investigated. Meanwhile, the potential of the chitosan and β-CD-EP composite film used as a plant healthcare material for carbendazim-controlled release to protect rape against [...] Read more.

The influence of β-cyclodextrin-epichlorohydrin (β-CD-EP) polymers on the improvement of the solubility and antifungal activity of carbendazim has been investigated. Meanwhile, the potential of the chitosan and β-CD-EP composite film used as a plant healthcare material for carbendazim-controlled release to protect rape against Sclerotinia sclerotiorum (Lib.) de Bary has been evaluated. β-CD-EP-1 and 2 (β-CD content, 750 mg/g and 440 mg/g, respectively) were found to significantly improve the solubility of the guest molecule carbendazim (17.9 and 18.5 times, respectively) and the 1:1 stoichiometry of the host-guest was confirmed by the Job’s plot. A slight synergism was observed for the β-CD-EP/carbendazim complex against S. sclerotiorum (Lib.) de Bary, indicating an enhancement to the bioavailability of carbendazim. The in vitro release studies revealed that β-CD-EP polymers could efficiently modulate carbendazim release behaviors, such as the release retard and rate. The in vivo efficacy experiments demonstrated that the β-CD-EP/carbendazim and chitosan composite film could significantly prolong the effective duration of carbendazim at a concentration of 100 μg/mL compared with spraying carbendazim at 500 μg/mL. Thereby, a highly useful and strategic concept in plant disease control by a plant healthcare material—the chitosan and polymeric β-CD-EP composite film—is provided, which could also serve as a concept for related plant diseases. Full article

(This article belongs to the Section Biomaterials)

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13 pages, 3850 KiB

Open AccessArticle

LiV₃O₈/Polytriphenylamine Composites with Enhanced Electrochemical Performances as Cathode Materials for Rechargeable Lithium Batteries

by Wenjuan Li^1,2, Limin Zhu^1,2,*, Ziheng Yu³, Lingling Xie^1,2 and Xiaoyu Cao^1,2,*

¹ School of Chemistry and Chemical Engineering, Henan University of Technology, Zhengzhou 450001, China

² Key Laboratory of High Specific Energy Materials for Electrochemical Power Sources of Zhengzhou City, Henan University of Technology, Zhengzhou 450001, China

³ School of Pharmacy, China Pharmaceutical University, Nanjing 211196, China

Materials 2017, 10(4), 344; https://doi.org/10.3390/ma10040344 - 26 Mar 2017

Cited by 20 | Viewed by 5289

Abstract

LiV₃O₈/polytriphenylamine composites are synthesized by a chemical oxidative polymerization process and applied as cathode materials for rechargeable lithium batteries (RLB). The structure, morphology, and electrochemical performances of the composites are characterized by X-ray diffraction, scanning electron microscopy, transmission electron [...] Read more.

LiV₃O₈/polytriphenylamine composites are synthesized by a chemical oxidative polymerization process and applied as cathode materials for rechargeable lithium batteries (RLB). The structure, morphology, and electrochemical performances of the composites are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, galvanostatic discharge/charge tests, and electrochemical impedance spectroscopy. It was found that the polytriphenylamine particles were composited with LiV₃O₈ nanorods which acted as a protective barrier against the side reaction of LiV₃O₈, as well as a conductive network to reduce the reaction resistance among the LiV₃O₈ particles. Among the LiV₃O₈/polytriphenylamine composites, the 17 wt % LVO/PTPAn composite showed the largest d₁₀₀ spacing. The electrochemical results showed that the 17 wt % LVO/PTPAn composite maintained a discharge capacity of 271 mAh·g⁻¹ at a current density of 60 mA·g⁻¹, as well as maintaining 236 mAh·g⁻¹ at 240 mA·g⁻¹ after 50 cycles, while the bare LiV₃O₈ sample retained only 169 and 148 mAh·g⁻¹, respectively. Electrochemical impedance spectra (EIS) results implied that the 17 wt % LVO/PTPAn composite demonstrated a decreased charge transfer resistance and increased Li⁺ ion diffusion ability, therefore manifesting better rate capability and cycling performance compared to the bare LiV₃O₈ sample. Full article

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12 pages, 3367 KiB

Open AccessArticle

Fabrication of Biocompatible Potassium Sodium Niobate Piezoelectric Ceramic as an Electroactive Implant

by Wei Chen¹, Zunxiong Yu², Jinshan Pang^1,*, Peng Yu¹, Guoxin Tan³ and Chengyun Ning^1,*

¹ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, China

² Center for Human Tissues and Organs Degeneration, Shenzhen Institute of Advanced Technology, Chinese Academy of Science, Shenzhen 518055, China

³ Institute of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China

Materials 2017, 10(4), 345; https://doi.org/10.3390/ma10040345 - 26 Mar 2017

Cited by 90 | Viewed by 8289

Abstract

The discovery of piezoelectricity in natural bone has attracted extensive research in emulating biological electricity for various tissue regeneration. Here, we carried out experiments to build biocompatible potassium sodium niobate (KNN) ceramics. Then, influence substrate surface charges on bovine serum albumin (BSA) protein [...] Read more.

The discovery of piezoelectricity in natural bone has attracted extensive research in emulating biological electricity for various tissue regeneration. Here, we carried out experiments to build biocompatible potassium sodium niobate (KNN) ceramics. Then, influence substrate surface charges on bovine serum albumin (BSA) protein adsorption and cell proliferation on KNN ceramics surfaces was investigated. KNN ceramics with piezoelectric constant of ~93 pC/N and relative density of ~93% were fabricated. The adsorption of protein on the positive surfaces (Ps) and negative surfaces (Ns) of KNN ceramics with piezoelectric constant of ~93 pC/N showed greater protein adsorption capacity than that on non-polarized surfaces (NPs). Biocompatibility of KNN ceramics was verified through cell culturing and live/dead cell staining of MC3T3. The cells experiment showed enhanced cell growth on the positive surfaces (Ps) and negative surfaces (Ns) compared to non-polarized surfaces (NPs). These results revealed that KNN ceramics had great potential to be used to understand the effect of surface potential on cells processes and would benefit future research in designing piezoelectric materials for tissue regeneration. Full article

(This article belongs to the Special Issue Bioceramics 2016)

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29 pages, 11281 KiB

Open AccessFeature PaperArticle

Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching

by Nikky Pathak^1,*, Cliff Butcher¹, Michael James Worswick¹, Erika Bellhouse² and Jeff Gao²

¹ Department of Mechanical Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada

² Research and Development, ArcelorMittal Dofasco, Hamilton, ON L8H 3N8, Canada

Materials 2017, 10(4), 346; https://doi.org/10.3390/ma10040346 - 27 Mar 2017

Cited by 81 | Viewed by 6769

Abstract

The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge [...] Read more.

The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures. Full article

(This article belongs to the Special Issue Modelling and Characterization of Defects in Metals)

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15 pages, 7768 KiB

Open AccessArticle

Nurse’s A-Phase Material Enhance Adhesion, Growth and Differentiation of Human Bone Marrow-Derived Stromal Mesenchymal Stem Cells

by Ruben Rabadan-Ros^1,*, Salvador Aznar-Cervantes²

, Patricia Mazón³

, Patricia Ros-Tarraga¹, Piedad N. De Aza⁴

and Luis Meseguer-Olmo^1,5

¹ Grupo de Regeneración y Reparación de Tejidos: Ortobiología, Biomateriales e Ingeniería de Tejidos, Universidad Católica San Antonio de Murcia (UCAM), Guadalupe, 30107 Murcia, Spain

² Department of Biotechnology, Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), La Alberca, 30150 Murcia, Spain

³ Departamento de Materiales, Óptica y Tecnología Electrónica, Universidad Miguel Hernández, Avda. Universidad s/n, Elche, 03202 Alicante, Spain

⁴ Instituto de Bioingeniería, Universidad Miguel Hernández, Avda. Universidad s/n, Elche, 03202 Alicante, Spain

⁵ Servicio de Cirugía Ortopédica y Traumatología del Hospital Clínico Universitario Virgen de la Arrixaca, 30120 Murcia, Spain

Materials 2017, 10(4), 347; https://doi.org/10.3390/ma10040347 - 27 Mar 2017

Cited by 6 | Viewed by 3397

Abstract

The purpose of this study was to evaluate the bioactivity and cell response of a well-characterized Nurse’s A-phase (7CaO·P₂O₅·2SiO₂) ceramic and its effect compared to a control (tissue culture polystyrene-TCPS) on the adhesion, viability, proliferation, and osteogenic [...] Read more.

The purpose of this study was to evaluate the bioactivity and cell response of a well-characterized Nurse’s A-phase (7CaO·P₂O₅·2SiO₂) ceramic and its effect compared to a control (tissue culture polystyrene-TCPS) on the adhesion, viability, proliferation, and osteogenic differentiation of ahMSCs in vitro. Cell proliferation (Alamar Blue Assay), Alizarin Red-S (AR-s) staining, alkaline phosphatase (ALP) activity, osteocalcin (OCN), and collagen I (Col I) were evaluated. Also, field emission scanning electron microscopy (FESEM) images were acquired in order to visualise the cells and the topography of the material. The proliferation of cells growing in a direct contact with the material was slower at early stages of the study because of the new environmental conditions. However, the entire surface was colonized after 28 days of culture in growth medium (GM). Osteoblastic differentiation markers were significantly enhanced in cells growing on Nurse’s A phase ceramic and cultured with osteogenic medium (OM), probably due to the role of silica to stimulate the differentiation of ahMSCs. Moreover, calcium nodules were formed under the influence of ceramic material. Therefore, it is predicted that Nurse’s A-phase ceramic would present high biocompatibility and osteoinductive properties and would be a good candidate to be used as a biomaterial for bone tissue engineering. Full article

(This article belongs to the Section Biomaterials)

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14 pages, 5290 KiB

Open AccessFeature PaperArticle

An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V

by Tatiana Mishurova^1,*

, Sandra Cabeza¹, Katia Artzt², Jan Haubrich², Manuela Klaus³, Christoph Genzel³, Guillermo Requena² and Giovanni Bruno^1,4

¹ Bundesanstalt für Materialforschung und-prüfung (BAM; Federal Institute for Materials Research and Testing), Unter den Eichen 87, 12205 Berlin, Germany

² Institute of Materials Research, German Aerospace Center (DLR; Deutsches Zentrum für Luft-und Raumfahrt), Linder Höhe, 51147 Cologne, Germany

³ Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner Platz 1, 14109 Berlin, Germany

⁴ Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany

Materials 2017, 10(4), 348; https://doi.org/10.3390/ma10040348 - 27 Mar 2017

Cited by 104 | Viewed by 10282

Abstract

Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. [...] Read more.

Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment. Full article

(This article belongs to the Special Issue Metals for Additive Manufacturing)

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10 pages, 1532 KiB

Open AccessArticle

Switching Characteristics and High-Temperature Dielectric Relaxation Behaviours of Pb(Zn_1/3Nb_2/3)_0.91Ti_0.09O₃ Single Crystal

by Zhi Zhu, Xingui Tang^*

, Yanping Jiang, Qiuxiang Liu, Tianfu Zhang and Wenhua Li

School of Physics & Optoelectric Engineering, Guangdong University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, China

Materials 2017, 10(4), 349; https://doi.org/10.3390/ma10040349 - 28 Mar 2017

Cited by 2 | Viewed by 3928

Abstract

This work evaluated the resistance switching characteristics in the (100)-oriented Pb(Zn_1/3Nb_2/3)_0.91Ti_0.09O₃ (PZNT) single crystal. The current hysteresis can be closely related to the ferroelectric polarization and we provided a possible explanation using a model [...] Read more.

This work evaluated the resistance switching characteristics in the (100)-oriented Pb(Zn_1/3Nb_2/3)_0.91Ti_0.09O₃ (PZNT) single crystal. The current hysteresis can be closely related to the ferroelectric polarization and we provided a possible explanation using a model about oxygen vacancies to analyze the mechanism of switching. The obvious frequency dispersion of the relative permittivity signified the relaxer-type behavior of the sample. The value of the relaxation parameter γ = 1.48 was estimated from the linear fit of the modified Curie-Weiss law, indicating the relaxer nature. High-temperature dielectric relaxation behaviors were revealed in the temperature region of 400–650 °C. In addition, under the measuring frequency of 10 kHz, ε_r was tunable by changing the electric field and the largest tunability of ε_r reached 14.78%. At room temperature, the high pyroelectric coefficient and detectivity figure of merit were reported. Full article

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17 pages, 9360 KiB

Open AccessArticle

Corrosion Prediction with Parallel Finite Element Modeling for Coupled Hygro-Chemo Transport into Concrete under Chloride-Rich Environment

by Okpin Na^1,*, Xiao-Chuan Cai² and Yunping Xi³

¹ R&D Division, Hyundai E&C, Yongin-si, Gyeonggi-do 16891, Korea

² Computer Science, University of Colorado Boulder, Boulder, CO 80309, USA

³ Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA

Materials 2017, 10(4), 350; https://doi.org/10.3390/ma10040350 - 28 Mar 2017

Cited by 8 | Viewed by 4586

Abstract

The prediction of the chloride-induced corrosion is very important because of the durable life of concrete structure. To simulate more realistic durability performance of concrete structures, complex scientific methods and more accurate material models are needed. In order to predict the robust results [...] Read more.

The prediction of the chloride-induced corrosion is very important because of the durable life of concrete structure. To simulate more realistic durability performance of concrete structures, complex scientific methods and more accurate material models are needed. In order to predict the robust results of corrosion initiation time and to describe the thin layer from concrete surface to reinforcement, a large number of fine meshes are also used. The purpose of this study is to suggest more realistic physical model regarding coupled hygro-chemo transport and to implement the model with parallel finite element algorithm. Furthermore, microclimate model with environmental humidity and seasonal temperature is adopted. As a result, the prediction model of chloride diffusion under unsaturated condition was developed with parallel algorithms and was applied to the existing bridge to validate the model with multi-boundary condition. As the number of processors increased, the computational time decreased until the number of processors became optimized. Then, the computational time increased because the communication time between the processors increased. The framework of present model can be extended to simulate the multi-species de-icing salts ingress into non-saturated concrete structures in future work. Full article

(This article belongs to the Special Issue Fundamental and Research Frontier of Atmospheric Corrosion)

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8 pages, 1118 KiB

Open AccessArticle

Crystallinity and Sub-Band Gap Absorption of Femtosecond-Laser Hyperdoped Silicon Formed in Different N-Containing Gas Mixtures

by Haibin Sun¹, Jiamin Xiao², Suwan Zhu¹, Yue Hu², Guojin Feng³, Jun Zhuang^2,* and Li Zhao^1,*

¹ Collaborative Innovation Center of Advanced Microstructures, State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China

² Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China

³ Spectrophotometry Laboratory, National Institute of Metrology, Beijing 100013, China

Materials 2017, 10(4), 351; https://doi.org/10.3390/ma10040351 - 28 Mar 2017

Cited by 10 | Viewed by 4654

Abstract

Femtosecond (fs)-laser hyperdoped silicon has aroused great interest for applications in infrared photodetectors due to its special properties. Crystallinity and optical absorption influenced by co-hyperdoped nitrogen in surface microstructured silicon, prepared by fs-laser irradiation in gas mixture of SF₆/NF₃ and [...] Read more.

Femtosecond (fs)-laser hyperdoped silicon has aroused great interest for applications in infrared photodetectors due to its special properties. Crystallinity and optical absorption influenced by co-hyperdoped nitrogen in surface microstructured silicon, prepared by fs-laser irradiation in gas mixture of SF₆/NF₃ and SF₆/N₂ were investigated. In both gas mixtures, nitrogen and sulfur were incorporated at average concentrations above 10¹⁹ atoms/cm³ in the 20–400 nm surface layer. Different crystallinity and optical absorption properties were observed for samples microstructured in the two gas mixtures. For samples prepared in SF₆/N₂, crystallinity and light absorption properties were similar to samples formed in SF₆. Significant differences were observed amongst samples formed in SF₆/NF₃, which possess higher crystallinity and strong sub-band gap absorption. The differing crystallinity and light absorption rates between the two types of nitrogen co-hyperdoped silicon were attributed to different nitrogen configurations in the doped layer. This was induced by fs-laser irradiating silicon in the two N-containing gas mixtures. Full article

(This article belongs to the Special Issue Ultrafast Laser-Based Manufacturing)

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12 pages, 9338 KiB

Open AccessArticle

Haemocompatibility of Modified Nanodiamonds

by Michał Wąsowicz¹

, Mateusz Ficek²

, Maciej S. Wróbel², Ruchira Chakraborty³, Dror Fixler³

, Paweł Wierzba² and Małgorzata Jędrzejewska-Szczerska^2,*

¹ Department of Morphological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences, Nowoursynowska 159, 02-776 Warszawa, Poland

² Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland

³ Faculty of Engineering and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel

Materials 2017, 10(4), 352; https://doi.org/10.3390/ma10040352 - 28 Mar 2017

Cited by 44 | Viewed by 5729

Abstract

This study reports the interactions of modified nanodiamond particles in vitro with human blood. Modifications performed on the nanodiamond particles include oxygenation with a chemical method and hydrogenation upon chemical vapor deposition (CVD) plasma treatment. Such nanodiamonds were later incubated in whole human [...] Read more.

This study reports the interactions of modified nanodiamond particles in vitro with human blood. Modifications performed on the nanodiamond particles include oxygenation with a chemical method and hydrogenation upon chemical vapor deposition (CVD) plasma treatment. Such nanodiamonds were later incubated in whole human blood for different time intervals, ranging from 5 min to 5 h. The morphology of red blood cells was assessed along with spectral measurements and determination of haemolysis. The results showed that no more than 3% of cells were affected by the nanodiamonds. Specific modifications of the nanodiamonds give us the possibility to obtain nanoparticles which are biocompatible with human blood. They can form a basis for the development of nanoscale biomarkers and parts of sensing systems and devices useful in biomedical environments. Full article

(This article belongs to the Special Issue Nanoprobes for Imaging)

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18 pages, 4200 KiB

Open AccessArticle

The Relationship between the Mechanism of Zinc Oxide Crystallization and Its Antimicrobial Properties for the Surface Modification of Surgical Meshes

by Marta Fiedot^1,*

, Irena Maliszewska², Olga Rac-Rumijowska¹

, Patrycja Suchorska-Woźniak¹

, Agnieszka Lewińska³

and Helena Teterycz¹

¹ Faculty of Microsystem Electronics and Photonics, Wroclaw University of Science and Technology, Janiszewskiego 11/17, 50-372 Wroclaw, Poland

² Faculty of Chemistry, Wroclaw University of Science and Technology, C.K. Norwida 4/6, 50-373 Wroclaw, Poland

³ Faculty of Chemistry, University of Wrocław, Joliot-Curie 14, 50-383 Wrocław, Poland

Materials 2017, 10(4), 353; https://doi.org/10.3390/ma10040353 - 28 Mar 2017

Cited by 49 | Viewed by 5442

Abstract

Surgical meshes were modified with zinc oxide (ZnO) using a chemical bath deposition method (CBD) at 50 °C, 70 °C, or 90 °C, in order to biologically activate them. Scanning electron microscopy (SEM), mass changes, and X-ray diffraction measurements revealed that at low [...] Read more.

Surgical meshes were modified with zinc oxide (ZnO) using a chemical bath deposition method (CBD) at 50 °C, 70 °C, or 90 °C, in order to biologically activate them. Scanning electron microscopy (SEM), mass changes, and X-ray diffraction measurements revealed that at low temperatures Zn(OH)₂ was formed, and that this was converted into ZnO with a temperature increase. The antimicrobial activity without light stimulation of the ZnO modified Mersilene™ meshes was related to the species of microorganism, the incubation time, and the conditions of the experiment. Generally, cocci (S. aureus, S. epidermidis) and yeast (C. albicans) were more sensitive than Gram-negative rods (E. coli). The differences in sensitivity of the studied microorganisms to ZnO were discussed. The most active sample was that obtained at 90 °C. The mechanism of antimicrobial action of ZnO was determined by various techniques, such as zeta potential analysis, electron paramagnetic resonance (EPR) spectroscopy, SEM studies, and measurements of Zn(II) and reactive oxygen species (ROS) concentration. Our results confirmed that the generation of free radicals was crucial, which occurs on the surface of crystalline ZnO. Full article

(This article belongs to the Section Biomaterials)

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11 pages, 7247 KiB

Open AccessArticle

Graphene Oxide: A Perfect Material for Spatial Light Modulation Based on Plasma Channels

by Chao Tan¹, Xinghua Wu^2,3, Qinkai Wang³

, Pinghua Tang⁴, Xiaohui Shi⁵, Shiping Zhan¹, Zaifang Xi¹ and Xiquan Fu^5,*

¹ School of Information and Electrical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China

² Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China

³ Key Laboratory for Microstructural Functional Materials of Jiangxi Province, College of Science, Jiujiang University, Jiujiang 332005, China

⁴ School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, China

⁵ Key Laboratory for Micro-/Nano-Optoelectronic Devices of Ministry of Education, College of Computer Science and Electronic Engineering, Hunan University, Changsha 410082, China

Materials 2017, 10(4), 354; https://doi.org/10.3390/ma10040354 - 28 Mar 2017

Cited by 3 | Viewed by 4778

Abstract

The graphene oxide (GO) is successfully prepared from a purified natural graphite through a pressurized oxidation method. We experimentally demonstrate that GO as an optical media can be used for spatial light modulation based on plasma channels induced by femtosecond pulses. The modulated [...] Read more.

The graphene oxide (GO) is successfully prepared from a purified natural graphite through a pressurized oxidation method. We experimentally demonstrate that GO as an optical media can be used for spatial light modulation based on plasma channels induced by femtosecond pulses. The modulated beam exhibits good propagation properties in free space. It is easy to realize the spatial modulation on the probe beam at a high concentration of GO dispersion solutions, high power and smaller pulse width of the pump beam. We also find that the spatial modulation on the probe beam can be conveniently adjusted through the power and pulse width of pump lasers, dispersion solution concentration. Full article

(This article belongs to the Special Issue Nonlinear Optical Material)

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16 pages, 5060 KiB

Open AccessFeature PaperArticle

Ice as a Green-Structure-Directing Agent in the Synthesis of Macroporous MWCNTs and Chondroitin Sulphate Composites

by Stefania Nardecchia^1,2,*, María Concepción Serrano³, Sara García-Argüelles^1,4, Marcelo E. H. Maia Da Costa², María Luisa Ferrer¹

and María C. Gutiérrez¹

¹ Materials Science Factory, Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, C/Sor Juana Inés de la Cruz 3, 28049-Madrid, Spain

² Departamento de Física, Pontificia Universidade Católica do Rio de Janeiro (PUC-Rio), Rua Marquês de São Vicente 225, Gavea 22451-900, Rio de Janeiro, Brazil

³ Laboratory of Interfaces for Neural Repair, Hospital Nacional de Parapléjicos, Servicio de Salud de Castilla-La Mancha, Finca de la Peraleda s/n, 45071-Toledo, Spain

⁴ Departamento de Tecnología Química y Energética, Tecnologia Química y Ambiental y Tecnología Mecánica y Química Analítica, Universidad Rey Juan Carlos, 28933-Madrid, Spain

Materials 2017, 10(4), 355; https://doi.org/10.3390/ma10040355 - 28 Mar 2017

Cited by 7 | Viewed by 4222

Abstract

The incorporation of multi-walled carbon nanotubes (MWCNTs) into chondroitin sulphate-based scaffolds and the effect on the structural, mechanical, conductive, and thermal properties of the resulting scaffolds is investigated. Three-dimensional hierarchical materials are prepared upon the application of the ice segregation-induced self-assembly (ISISA) process. [...] Read more.

The incorporation of multi-walled carbon nanotubes (MWCNTs) into chondroitin sulphate-based scaffolds and the effect on the structural, mechanical, conductive, and thermal properties of the resulting scaffolds is investigated. Three-dimensional hierarchical materials are prepared upon the application of the ice segregation-induced self-assembly (ISISA) process. The use of ice as structure-directing agents avoids chemicals typically used for this purpose (e.g., surfactants, block copolymers, etc.), hence, emphasising the green features of this soft-templating approach. We determine the critical parameters that control the morphology of the scaffolds formed upon ice-templating (i.e., MWCNTs type, freezing conditions, polymer and MWCNT concentration). MWCNTs are surface functionalized by acidic treatment. MWCNT functionalization is characterized by Raman, Fourier transfer infrared (FTIR) and X-ray Photoelectron (XPS) spectroscopies. Scanning electron microscopy (SEM) analysis and porosity studies reveal that MWCNT content modifies the morphology of the macroporous structure, which decreases by increasing MWCNT concentration. Differences in scaffold morphology should be translated into their conductivity and mechanical properties. As a general trend, the Young’s modulus and the electrical conductivity of the scaffolds increase with the MWCNT content. Preliminary biocompatibility tests with human osteoblast-like cells also reveal the capability of these structures to support cell growth. Full article

(This article belongs to the Special Issue Green Chemistry - both precursors and processes - to Hierarchical Materials)

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15 pages, 2288 KiB

Open AccessArticle

Silk: Optical Properties over 12.6 Octaves THz-IR-Visible-UV Range

by Armandas Balčytis^1,2,7,*, Meguya Ryu^3,7, Xuewen Wang^1,7, Fabio Novelli^1,8, Gediminas Seniutinas^1,9, Shan Du⁴, Xungai Wang⁴, Jingliang Li⁴, Jeffrey Davis¹, Dominique Appadoo⁵, Junko Morikawa^3,* and Saulius Juodkazis^1,6

¹ School of Science, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, VIC 3122, Australia

² Department of Laser Technologies, Center for Physical Sciences and Technology, Savanoriu Ave. 231, LT-02300 Vilnius, Lithuania

³ Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan

⁴ Australian Future Fibres Research and Innovation Centre, Institute for Frontier Materials, Deakin University, Geelong, VIC 3220, Australia

⁵ Australian Synchrotron, Blackburn Road, Clayton, VIC 3168, Australia

⁶ Melbourne Centre for Nanofabrication, the Victorian Node of the Australian National Fabrication Facility, 151 Wellington Rd., Clayton, VIC 3168, Australia

⁷ These authors contributed equally to this work.

⁸ Current address: Ruhr-University Bochum, 44801 Bochum, Germany.

⁹ Current address: Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.

Materials 2017, 10(4), 356; https://doi.org/10.3390/ma10040356 - 28 Mar 2017

Cited by 31 | Viewed by 6418

Abstract

Domestic (Bombyx mori) and wild (Antheraea pernyi) silk fibers were characterised over a wide spectral range from THz 8 cm

^{- 1}

(

λ =

1.25 mm,

f =

0.24 THz) to deep-UV

50 \times 10^{3}

cm [...] Read more.

Domestic (Bombyx mori) and wild (Antheraea pernyi) silk fibers were characterised over a wide spectral range from THz 8 cm

^{- 1}

(

λ =

1.25 mm,

f =

0.24 THz) to deep-UV

50 \times 10^{3}

cm

^{- 1}

(

λ =

200 nm,

f =

1500 THz) wavelengths or over a 12.6 octave frequency range. Spectral features at

β

-sheet,

α

-coil and amorphous fibroin were analysed at different spectral ranges. Single fiber cross sections at mid-IR were used to determine spatial distribution of different silk constituents and revealed an

α

-coil rich core and more broadly spread

β

-sheets in natural silk fibers obtained from wild Antheraea pernyi moths. Low energy T-ray bands at 243 and 229 cm

^{- 1}

were observed in crystalline fibers of domestic and wild silk fibers, respectively, and showed no spectral shift down to 78 K temperature. A distinct

20 \pm 4

cm

^{- 1}

band was observed in the crystalline Antheraea pernyi silk fibers. Systematic analysis and assignment of the observed spectral bands is presented. Water solubility and biodegradability of silk, required for bio-medical and sensor applications, are directly inferred from specific spectral bands. Full article

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7 pages, 3356 KiB

Open AccessCommunication

The Fabrication of Porous Si with Interconnected Micro-Sized Dendrites and Tunable Morphology through the Dealloying of a Laser Remelted Al–Si Alloy

by Ting Huang^*, Dingyue Sun, Wuxiong Yang, Qiang Wu and Rongshi Xiao

High-Power and Ultrafast Laser Manufacturing Laboratory, Institute of Laser Engineering, Beijing University of Technology, Beijing 100124, China

Materials 2017, 10(4), 357; https://doi.org/10.3390/ma10040357 - 28 Mar 2017

Cited by 8 | Viewed by 4597

Abstract

Coral-like porous Si was fabricated through the dealloying of a laser remelted as-cast AlSi12 alloy(Al-12 wt % Si). The porous Si was composed of interconnected micro-sized Si dendrites and micro/nanopores, and compared to flaky Si, which is fabricated by direct dealloying of the [...] Read more.

Coral-like porous Si was fabricated through the dealloying of a laser remelted as-cast AlSi12 alloy(Al-12 wt % Si). The porous Si was composed of interconnected micro-sized Si dendrites and micro/nanopores, and compared to flaky Si, which is fabricated by direct dealloying of the as-cast AlSi12 alloy. The structure of the porous Si was attributed to the dendritic solidification microstructure formed during the laser remelting process. The micropore size of the porous Si decreased from 4.2 μm to 1.6 µm with the increase in laser scanning velocity, indicating that the morphology of porous Si could be easily altered by simply controlling the laser remelting parameters. The coral-like porous Si provided enough space, making it promising for high-performance Si-based composite anode materials in lithium-ion batteries. The proposed hybrid method provides a straightforward way of tuning the porous structure in the dealloyed material. Full article

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

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15 pages, 6401 KiB

Open AccessArticle

RGDC Peptide-Induced Biomimetic Calcium Phosphate Coating Formed on AZ31 Magnesium Alloy

by Lin Cao¹, Lina Wang¹, Lingying Fan¹, Wenjun Xiao¹, Bingpeng Lin¹, Yimeng Xu¹, Jun Liang² and Baocheng Cao^1,*

¹ School of Stomatology, Lanzhou University, Lanzhou 730000, China

² State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China

Materials 2017, 10(4), 358; https://doi.org/10.3390/ma10040358 - 28 Mar 2017

Cited by 23 | Viewed by 4750

Abstract

Magnesium alloys as biodegradable metal implants have received a lot of interest in biomedical applications. However, magnesium alloys have extremely high corrosion rates a in physiological environment, which have limited their application in the orthopedic field. In this study, calcium phosphate compounds (Ca–P) [...] Read more.

Magnesium alloys as biodegradable metal implants have received a lot of interest in biomedical applications. However, magnesium alloys have extremely high corrosion rates a in physiological environment, which have limited their application in the orthopedic field. In this study, calcium phosphate compounds (Ca–P) coating was prepared by arginine–glycine–aspartic acid–cysteine (RGDC) peptide-induced mineralization in 1.5 simulated body fluid (SBF) to improve the corrosion resistance and biocompatibility of the AZ31 magnesium alloys. The adhesion of Ca–P coating to the AZ31 substrates was evaluated by a scratch test. Corrosion resistance and cytocompatibility of the Ca–P coating were investigated. The results showed that the RGDC could effectively promote the nucleation and crystallization of the Ca–P coating and the Ca–P coating had poor adhesion to the AZ31 substrates. The corrosion resistance and biocompatibility of the biomimetic Ca–P coating Mg alloys were greatly improved compared with that of the uncoated sample. Full article

(This article belongs to the Section Biomaterials)

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14 pages, 2402 KiB

Open AccessArticle

Al-Doped ZnO Monolayer as a Promising Transparent Electrode Material: A First-Principles Study

by Mingyang Wu^1,*, Dan Sun², Changlong Tan^2,*, Xiaohua Tian² and Yuewu Huang³

¹ School of Mechanical Engineering, Harbin University of Science and Technology, Harbin 150080, China

² College of Applied Science, Harbin University of Science and Technology, Harbin 150080, China

³ School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

Materials 2017, 10(4), 359; https://doi.org/10.3390/ma10040359 - 29 Mar 2017

Cited by 50 | Viewed by 9117

Abstract

Al-doped ZnO has attracted much attention as a transparent electrode. The graphene-like ZnO monolayer as a two-dimensional nanostructure material shows exceptional properties compared to bulk ZnO. Here, through first-principle calculations, we found that the transparency in the visible light region of Al-doped ZnO [...] Read more.

Al-doped ZnO has attracted much attention as a transparent electrode. The graphene-like ZnO monolayer as a two-dimensional nanostructure material shows exceptional properties compared to bulk ZnO. Here, through first-principle calculations, we found that the transparency in the visible light region of Al-doped ZnO monolayer is significantly enhanced compared to the bulk counterpart. In particular, the 12.5 at% Al-doped ZnO monolayer exhibits the highest visible transmittance of above 99%. Further, the electrical conductivity of the ZnO monolayer is enhanced as a result of Al doping, which also occurred in the bulk system. Our results suggest that Al-doped ZnO monolayer is a promising transparent conducting electrode for nanoscale optoelectronic device applications. Full article

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

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17 pages, 8434 KiB

Open AccessArticle

Mineral-Based Coating of Plasma-Treated Carbon Fibre Rovings for Carbon Concrete Composites with Enhanced Mechanical Performance

by Kai Schneider¹, Matthias Lieboldt², Marco Liebscher¹

, Maik Fröhlich³, Simone Hempel¹, Marko Butler¹, Christof Schröfl¹ and Viktor Mechtcherine^1,*

¹ Technische Universität Dresden, Institute of Construction Materials, DE-01062 Dresden, Germany

² Technische Universität Dresden, Institute of Concrete Structures, DE-01062 Dresden, Germany

³ Leibniz Institute for Plasma Science and Technology e.V. (INP Greifswald), DE-17489 Greifswald, Germany

Materials 2017, 10(4), 360; https://doi.org/10.3390/ma10040360 - 29 Mar 2017

Cited by 55 | Viewed by 6549

Abstract

Surfaces of carbon fibre roving were modified by means of a low temperature plasma treatment to improve their bonding with mineral fines; the latter serving as an inorganic fibre coating for the improved mechanical performance of carbon reinforcement in concrete matrices. Variation of [...] Read more.

Surfaces of carbon fibre roving were modified by means of a low temperature plasma treatment to improve their bonding with mineral fines; the latter serving as an inorganic fibre coating for the improved mechanical performance of carbon reinforcement in concrete matrices. Variation of the plasma conditions, such as gas composition and treatment time, was accomplished to establish polar groups on the carbon fibres prior to contact with the suspension of mineral particles in water. Subsequently, the rovings were implemented in a fine concrete matrix and their pull-out performance was assessed. Every plasma treatment resulted in increased pull-out forces in comparison to the reference samples without plasma treatment, indicating a better bonding between the mineral coating material and the carbon fibres. Significant differences were found, depending on gas composition and treatment time. Microscopic investigations showed that the samples with the highest pull-out force exhibited carbon fibre surfaces with the largest areas of hydration products grown on them. Additionally, the coating material ingresses into the multifilament roving in these specimens, leading to better force transfer between individual carbon filaments and between the entire roving and surrounding matrix, thus explaining the superior mechanical performance of the specimens containing appropriately plasma-treated carbon roving. Full article

(This article belongs to the Section Advanced Composites)

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12 pages, 1551 KiB

Open AccessArticle

Assembly of One-Patch Colloids into Clusters via Emulsion Droplet Evaporation

by Hai Pham Van^1,2, Andrea Fortini³ and Matthias Schmidt^1,*

¹ Theoretische Physik II, Physikalisches Institut, Universität Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany

² Department of Physics, Hanoi National University of Education, 136 Xuanthuy, Hanoi 100000, Vietnam

³ Department of Physics, University of Surrey, Guildford GU2 7XH, UK

Materials 2017, 10(4), 361; https://doi.org/10.3390/ma10040361 - 29 Mar 2017

Cited by 7 | Viewed by 5512

Abstract

We study the cluster structures of one-patch colloidal particles generated by droplet evaporation using Monte Carlo simulations. The addition of anisotropic patch–patch interaction between the colloids produces different cluster configurations. We find a well-defined category of sphere packing structures that minimize the second [...] Read more.

We study the cluster structures of one-patch colloidal particles generated by droplet evaporation using Monte Carlo simulations. The addition of anisotropic patch–patch interaction between the colloids produces different cluster configurations. We find a well-defined category of sphere packing structures that minimize the second moment of mass distribution when the attractive surface coverage of the colloids

χ

is larger than

0.3

. For

χ < 0.3

, the uniqueness of the packing structures is lost, and several different isomers are found. A further decrease of

χ

below

0.2

leads to formation of many isomeric structures with less dense packings. Our results could provide an explanation of the occurrence of uncommon cluster configurations in the literature observed experimentally through evaporation-driven assembly. Full article

(This article belongs to the Special Issue Designed Colloidal Self-Assembly)

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16 pages, 3959 KiB

Open AccessArticle

Deformation Modes and Anisotropy of Anti-Perovskite Ti₃AN (A = Al, In and Tl) from First-Principle Calculations

by Kuankuan Chen, Cong Li, Meng Hu, Xun Hou, Chunmei Li

and Zhiqian Chen^*

Faculty of Materials and Energy, Southwest University, Chongqing 400715, China

Materials 2017, 10(4), 362; https://doi.org/10.3390/ma10040362 - 29 Mar 2017

Cited by 11 | Viewed by 5341

Abstract

Deformation modes were studied for Ti₃AN (A = Al, In and Tl) by applying strain to the materials using first-principle calculations. The states of the bonds changed during the deformation process, and the Ti-N bonds remained structurally stable under deformation. The [...] Read more.

Deformation modes were studied for Ti₃AN (A = Al, In and Tl) by applying strain to the materials using first-principle calculations. The states of the bonds changed during the deformation process, and the Ti-N bonds remained structurally stable under deformation. The elastic anisotropy, electronic structures, hardness, and minimum thermal conductivity of anti-perovskite Ti₃AN were investigated using the pseudo potential plane-wave method based on density functional theory. We found that the anisotropy of Ti₃InN was significantly larger than that of Ti₃AlN and Ti₃TlN. All three compounds were mechanically stable. The band structures of the three compounds revealed that they were conductors. The minimum thermal conductivities at high temperature in the propagation directions of [100], [110], and [111] were calculated by the acoustic wave velocity, which indicated that the thermal conductivity was also anisotropic. It is indicated that Ti₃InN is a good thermal barrier material. Full article

(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)

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8 pages, 1016 KiB

Open AccessFeature PaperArticle

Observation of Distinct Two-Photon Transition Channels in CdTe Quantum Dots in a Regime of Very Strong Confinement

by Marcelo Gonçalves Vivas^1,2, José Carlos Leandro De Sousa^3,*, Leonardo De Boni²

, Marco Antônio Schiavon³

and Cleber Renato Mendonca^2,*

¹ Instituto de Ciência e Tecnologia, Universidade Federal de Alfenas, Poços de Caldas, Minas Gerais 37715-400, Brazil

² Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, São Paulo 13560-970, Brazil

³ Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, São João del-Rei, Minas Gerais 36301-160, Brazil

Materials 2017, 10(4), 363; https://doi.org/10.3390/ma10040363 - 30 Mar 2017

Cited by 5 | Viewed by 4770

Abstract

We report here on the direct observation of distinct two-photon transition channels in glutathione-capped (GSH) CdTe quantum dots (QDs) in a very strong confinement regime. CdTe-GSH QDs with different average diameters (2.5, 3.0, and 3.3 nm) were synthesized through the one-pot method and [...] Read more.

We report here on the direct observation of distinct two-photon transition channels in glutathione-capped (GSH) CdTe quantum dots (QDs) in a very strong confinement regime. CdTe-GSH QDs with different average diameters (2.5, 3.0, and 3.3 nm) were synthesized through the one-pot method and their two-photon absorption (2PA) spectrum determined by a femtosecond wavelength-tunable Z-scan. Our results show that the two lower-energy one-photon-allowed excitonic transitions, 1S_3/2(h) → 1S(e) and 2S_3/2(h) → 1S(e), are also accessed via 2PA. These results were ascribed to the relaxation of the parity selection rules due to the noncentrosymmetric structure of the CdTe QDs (zinc-blended structure), whose magnitude are determined by surface defects and structural irregularities present in CdTe-GSH QDs, in the strong confinement regime. Full article

(This article belongs to the Special Issue Two-Photon Absorption Materials)

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11 pages, 4733 KiB

Open AccessArticle

Wear Distribution Detection of Knee Joint Prostheses by Means of 3D Optical Scanners

by Saverio Affatato^1,*

, Maria Cristina Valigi²

and Silvia Logozzo^2,3

¹ Medical Technology Laboratory, Rizzoli Orthopaedic Institute, 40136 Bologna, Italy

² Department of Engineering, University of Perugia, 06125 Perugia, Italy

³ Department of Research, V-GER S.r.l., Via Mori 6, Prunaro di Budrio,40121 Bologna, Italy

Materials 2017, 10(4), 364; https://doi.org/10.3390/ma10040364 - 30 Mar 2017

Cited by 33 | Viewed by 5054

Abstract

The objective of this study was to examine total knee polyethylene inserts from in vitro simulation to evaluate and display—using a 3D optical scanner—wear patterns and wear rates of inserts exposed to wear by means of simulators. Various sets of tibial inserts have [...] Read more.

The objective of this study was to examine total knee polyethylene inserts from in vitro simulation to evaluate and display—using a 3D optical scanner—wear patterns and wear rates of inserts exposed to wear by means of simulators. Various sets of tibial inserts have been reconstructed by using optical scanners. With this in mind, the wear behavior of fixed and mobile bearing polyethylene knee configurations was investigated using a knee wear joint simulator. After the completion of the wear test, the polyethylene menisci were analyzed by an innovative 3D optical scanners in order to evaluate the 3D wear distribution on the prosthesis surface. This study implemented a new procedure for evaluating polyethylene bearings of joint prostheses obtained after in vitro wear tests and the proposed new approach allowed quantification of the contact zone on the geometry of total knee prostheses. The results of the present study showed that mobile TKPs (total knee prosthesis) have lower wear resistance with respect to fixed TKPs. Full article

(This article belongs to the Special Issue Corrosion and Tribology of Biomaterials Used in Hip and Knee Arthroplasty)

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13 pages, 3706 KiB

Open AccessArticle

Effects of Heat-Treated Wood Particles on the Physico-Mechanical Properties and Extended Creep Behavior of Wood/Recycled-HDPE Composites Using the Time–Temperature Superposition Principle

by Teng-Chun Yang, Yi-Chi Chien, Tung-Lin Wu, Ke-Chang Hung and Jyh-Horng Wu^*

Department of Forestry, National Chung Hsing University, Taichung 402, Taiwan

Materials 2017, 10(4), 365; https://doi.org/10.3390/ma10040365 - 30 Mar 2017

Cited by 26 | Viewed by 6013

Abstract

This study investigated the effectiveness of heat-treated wood particles for improving the physico-mechanical properties and creep performance of wood/recycled-HDPE composites. The results reveal that the composites with heat-treated wood particles had significantly decreased moisture content, water absorption, and thickness swelling, while no improvements [...] Read more.

This study investigated the effectiveness of heat-treated wood particles for improving the physico-mechanical properties and creep performance of wood/recycled-HDPE composites. The results reveal that the composites with heat-treated wood particles had significantly decreased moisture content, water absorption, and thickness swelling, while no improvements of the flexural properties or the wood screw holding strength were observed, except for the internal bond strength. Additionally, creep tests were conducted at a series of elevated temperatures using the time–temperature superposition principle (TTSP), and the TTSP-predicted creep compliance curves fit well with the experimental data. The creep resistance values of composites with heat-treated wood particles were greater than those having untreated wood particles due to the hydrophobic character of the treated wood particles and improved interfacial compatibility between the wood particles and polymer matrix. At a reference temperature of 20 °C, the improvement of creep resistance (ICR) of composites with heat-treated wood particles reached approximately 30% over a 30-year period, and it increased significantly with increasing reference temperature. Full article

(This article belongs to the Special Issue Thermal Sciences and Thermodynamics of Materials)

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12 pages, 12448 KiB

Open AccessArticle

The Production of Porous Hydroxyapatite Scaffolds with Graded Porosity by Sequential Freeze-Casting

by Hyun Lee¹, Tae-Sik Jang^1,2, Juha Song², Hyoun-Ee Kim^1,3 and Hyun-Do Jung^4,*

¹ Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea

² School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Drive, Singapore 637457, Singapore

³ Biomedical Implant Convergence Research Center, Advanced Institutes of Convergence Technology, Suwon 443-270, Korea

⁴ Liquid Processing & Casting Technology R&D Group, Korea Institute of Industrial Technology, Incheon 406-840, Korea

Materials 2017, 10(4), 367; https://doi.org/10.3390/ma10040367 - 31 Mar 2017

Cited by 52 | Viewed by 9486

Abstract

Porous hydroxyapatite (HA) scaffolds with porosity-graded structures were fabricated by sequential freeze-casting. The pore structures, compressive strengths, and biocompatibilities of the fabricated porous HA scaffolds were evaluated. The porosities of the inner and outer layers of the graded HA scaffolds were controlled by [...] Read more.

Porous hydroxyapatite (HA) scaffolds with porosity-graded structures were fabricated by sequential freeze-casting. The pore structures, compressive strengths, and biocompatibilities of the fabricated porous HA scaffolds were evaluated. The porosities of the inner and outer layers of the graded HA scaffolds were controlled by adjusting the initial HA contents of the casting slurries. The interface between the dense and porous parts was compact and tightly adherent. The porosity and compressive strengths of the scaffold were controlled by the relative thicknesses of the dense/porous parts. In addition, the porous HA scaffolds showed good biocompatibility in terms of preosteoblast cell attachment and proliferation. The results suggest that porous HA scaffolds with load-bearing parts have potential as bone grafts in hard-tissue engineering. Full article

(This article belongs to the Special Issue Porous Ceramics)

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12 pages, 1697 KiB

Open AccessArticle

Electrodeposited Porous Mn_1.5Co_1.5O₄/Ni Composite Electrodes for High-Voltage Asymmetric Supercapacitors

by Guan-Ting Pan¹

, Siewhui Chong²

, Thomas C.-K. Yang¹ and Chao-Ming Huang^3,*

¹ Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 106, Taiwan

² Department of Chemical and Environmental Engineering, University of Nottingham, Selangor 43500, Malaysia

³ Department of Materials Engineering, Kun Shan University, Tainan 710, Taiwan

Materials 2017, 10(4), 370; https://doi.org/10.3390/ma10040370 - 31 Mar 2017

Cited by 24 | Viewed by 5652

Abstract

Mesoporous Mn_1.5Co_1.5O₄ (MCO) spinel films were prepared directly on a conductive nickel (Ni) foam substrate via electrodeposition and an annealing treatment as supercapacitor electrodes. The electrodeposition time markedly influenced the surface morphological, textural, and supercapacitive properties of MCO/Ni [...] Read more.

Mesoporous Mn_1.5Co_1.5O₄ (MCO) spinel films were prepared directly on a conductive nickel (Ni) foam substrate via electrodeposition and an annealing treatment as supercapacitor electrodes. The electrodeposition time markedly influenced the surface morphological, textural, and supercapacitive properties of MCO/Ni electrodes. The (MCO/Ni)-15 min electrode (electrodeposition time: 15 min) exhibited the highest capacitance among three electrodes (electrodeposition times of 7.5, 15, and 30 min, respectively). Further, an asymmetric supercapacitor that utilizes (MCO/Ni)-15 min as a positive electrode, a plasma-treated activated carbon (PAC)/Ni electrode as a negative electrode, and carboxymethyl cellulose-lithium nitrate (LiNO₃) gel electrolyte (denoted as (PAC/Ni)//(MCO/Ni)-15 min) was fabricated. In a stable operation window of 2.0 V, the device exhibited an energy density of 27.6 Wh·kg⁻¹ and a power density of 1.01 kW·kg⁻¹ at 1 A·g⁻¹. After 5000 cycles, the specific energy density retention and power density retention were 96% and 92%, respectively, demonstrating exceptional cycling stability. The good supercapacitive performance and excellent stability of the (PAC/Ni)//(MCO/Ni)-15 min device can be ascribed to the hierarchical structure and high surface area of the (MCO/Ni)-15 min electrode, which facilitate lithium ion intercalation and deintercalation at the electrode/electrolyte interface and mitigate volume change during long-term charge/discharge cycling. Full article

(This article belongs to the Special Issue Materials for Electrochemical Capacitors and Batteries)

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16 pages, 9752 KiB

Open AccessArticle

Fatigue Damage and Lifetime of SiC/SiC Ceramic-Matrix Composite under Cyclic Loading at Elevated Temperatures

by Longbiao Li

College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, No. 29 Yudao St., Nanjing 210016, China

Materials 2017, 10(4), 371; https://doi.org/10.3390/ma10040371 - 31 Mar 2017

Cited by 13 | Viewed by 5019

Abstract

In this paper, the fatigue damage and lifetime of 2D SiC/SiC ceramic-matrix composites (CMCs) under cyclic fatigue loading at 750, 1000, 1100, 1200 and 1300 °C in air and in steam atmosphere have been investigated. The damage evolution versus applied cycles of 2D [...] Read more.

In this paper, the fatigue damage and lifetime of 2D SiC/SiC ceramic-matrix composites (CMCs) under cyclic fatigue loading at 750, 1000, 1100, 1200 and 1300 °C in air and in steam atmosphere have been investigated. The damage evolution versus applied cycles of 2D SiC/SiC composites were analyzed using fatigue hysteresis dissipated energy, fatigue hysteresis modulus, fatigue peak strain and interface shear stress. The presence of steam accelerated the damage development inside of SiC/SiC composites, which increased the increasing rate of the fatigue hysteresis dissipated energy and the fatigue peak strain, and the decreasing rate of the fatigue hysteresis modulus and the interface shear stress. The fatigue life stress-cycle (S-N) curves and fatigue limit stresses of 2D SiC/SiC composites at different temperatures in air and in steam condition have been predicted. The fatigue limit stresses approach 67%, 28%, 39% 17% and 28% tensile strength at 750, 1000, 1100, 1200 and 1300 °C in air, and 49%, 10%, 9% and 19% tensile strength at 750, 1000, 1200 and 1300 °C in steam conditions, respectively. Full article

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15 pages, 3282 KiB

Open AccessArticle

Chloride Diffusion and Acid Resistance of Concrete Containing Zeolite and Tuff as Partial Replacements of Cement and Sand

by Ehsan Mohseni¹, Waiching Tang^1,*

and Hongzhi Cui²

¹ School of Architecture and Built Environment, The University of Newcastle, Callaghan NSW 2308, Australia

² Shenzhen Durability Center for Civil Engineering, Shenzhen University, Shenzhen 518060, China

Materials 2017, 10(4), 372; https://doi.org/10.3390/ma10040372 - 31 Mar 2017

Cited by 75 | Viewed by 5769

Abstract

In this paper, the properties of concrete containing zeolite and tuff as partial replacements of cement and sand were studied. The compressive strength, water absorption, chloride ion diffusion and resistance to acid environments of concretes made with zeolite at proportions of 10% and [...] Read more.

In this paper, the properties of concrete containing zeolite and tuff as partial replacements of cement and sand were studied. The compressive strength, water absorption, chloride ion diffusion and resistance to acid environments of concretes made with zeolite at proportions of 10% and 15% of binder and tuff at ratios of 5%, 10% and 15% of fine aggregate were investigated. The results showed that the compressive strength of samples with zeolite and tuff increased considerably. In general, the concrete strength increased with increasing tuff content, and the strength was further improved when cement was replaced by zeolite. According to the water absorption results, specimens with zeolite showed the lowest water absorption values. With the incorporation of tuff and zeolite, the chloride resistance of specimens was enhanced significantly. In terms of the water absorption and chloride diffusion results, the most favorable replacement of cement and sand was 10% zeolite and 15% tuff, respectively. However, the resistance to acid attack reduced due to the absorbing characteristic and calcareous nature of the tuff. Full article

(This article belongs to the Section Advanced Composites)

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13 pages, 7849 KiB

Open AccessArticle

One-Pot Route towards Active TiO₂ Doped Hierarchically Porous Cellulose: Highly Efficient Photocatalysts for Methylene Blue Degradation

by Xiaoxia Sun^1,2,3, Kunpeng Wang¹, Yu Shu⁴, Fangdong Zou¹, Boxing Zhang⁵, Guangwu Sun⁶, Hiroshi Uyama⁴ and Xinhou Wang^1,2,*

¹ College of Textiles, Donghua University, Shanghai 201620, China

² Key Laboratory of Textile Science & Technology of Eco-Textile, Ministry of Education, Donghua University, Shanghai 201620, China

³ Key Laboratory of Textile Science & Technology, Ministry of Education, Donghua University, Shanghai 201620, China

⁴ Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan

⁵ South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510641, China

⁶ School of Fashion Technology, Shanghai University of Engineering Science, Shanghai 201620, China

Materials 2017, 10(4), 373; https://doi.org/10.3390/ma10040373 - 31 Mar 2017

Cited by 17 | Viewed by 5831

Abstract

In this study, novel photocatalyst monolith materials were successfully fabricated by a non-solvent induced phase separation (NIPS) technique. By adding a certain amount of ethyl acetate (as non-solvent) into a cellulose/LiCl/N,N-dimethylacetamide (DMAc) solution, and successively adding titanium dioxide (TiO [...] Read more.

In this study, novel photocatalyst monolith materials were successfully fabricated by a non-solvent induced phase separation (NIPS) technique. By adding a certain amount of ethyl acetate (as non-solvent) into a cellulose/LiCl/N,N-dimethylacetamide (DMAc) solution, and successively adding titanium dioxide (TiO₂) nanoparticles (NPs), cellulose/TiO₂ composite monoliths with hierarchically porous structures were easily formed. The obtained composite monoliths possessed mesopores, and two kinds of macropores. Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), and Ultraviolet-visible Spectroscopy (UV-Vis) measurements were adopted to characterize the cellulose/TiO₂ composite monolith. The cellulose/TiO₂ composite monoliths showed high efficiency of photocatalytic activity in the decomposition of methylene blue dye, which was decomposed up to 99% within 60 min under UV light. Moreover, the composite monoliths could retain 90% of the photodegradation efficiency after 10 cycles. The novel NIPS technique has great potential for fabricating recyclable photocatalysts with highly efficiency. Full article

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

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10 pages, 3069 KiB

Open AccessArticle

Fabrication of Carbonate Apatite Block through a Dissolution–Precipitation Reaction Using Calcium Hydrogen Phosphate Dihydrate Block as a Precursor

by Kanji Tsuru^1,*, Ayami Yoshimoto¹, Masayuki Kanazawa², Yuki Sugiura¹, Yasuharu Nakashima² and Kunio Ishikawa¹

¹ Department of Biomaterials, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan

² Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan

Materials 2017, 10(4), 374; https://doi.org/10.3390/ma10040374 - 31 Mar 2017

Cited by 37 | Viewed by 5527

Abstract

Carbonate apatite (CO₃Ap) block, which is a bone replacement used to repair defects, was fabricated through a dissolution–precipitation reaction using a calcium hydrogen phosphate dihydrate (DCPD) block as a precursor. When the DCPD block was immersed in NaHCO₃ or Na [...] Read more.

Carbonate apatite (CO₃Ap) block, which is a bone replacement used to repair defects, was fabricated through a dissolution–precipitation reaction using a calcium hydrogen phosphate dihydrate (DCPD) block as a precursor. When the DCPD block was immersed in NaHCO₃ or Na₂CO₃ solution at 80 °C, DCPD converted to CO₃Ap within 3 days. β-Tricalcium phosphate was formed as an intermediate phase, and it was completely converted to CO₃Ap within 2 weeks when the DCPD block was immersed in Na₂CO₃ solution. Although the crystal structures of the DCPD and CO₃Ap blocks were different, the macroscopic structure was maintained during the compositional transformation through the dissolution–precipitation reaction. CO₃Ap block fabricated in NaHCO₃ or Na₂CO₃ solution contained 12.9 and 15.8 wt % carbonate, respectively. The diametral tensile strength of the CO₃Ap block was 2 MPa, and the porosity was approximately 57% regardless of the carbonate solution. DCPD is a useful precursor for the fabrication of CO₃Ap block. Full article

(This article belongs to the Special Issue Bioceramics 2016)

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11 pages, 16316 KiB

Open AccessArticle

A Novel Extrusion for Manufacturing TiBw/Ti6Al4V Composite Tubes with a Quasi-Continuous Reinforced Structure

by Jianlei Yang, Xueyan Jiao, Wenzhen Chen^*, Wencong Zhang and Guofeng Wang

School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

Materials 2017, 10(4), 375; https://doi.org/10.3390/ma10040375 - 31 Mar 2017

Cited by 4 | Viewed by 4543

Abstract

The present work introduces a novel extrusion with filler material to produce the high-performance TiBw/Ti-6Al-4V composite tube with a quasi-continuous reinforced structure. A simulation was adopted to study the effect of the filler material on the shape accuracy of the tubes. Based on [...] Read more.

The present work introduces a novel extrusion with filler material to produce the high-performance TiBw/Ti-6Al-4V composite tube with a quasi-continuous reinforced structure. A simulation was adopted to study the effect of the filler material on the shape accuracy of the tubes. Based on the simulation results, the flow stress of the filler material was not the important factor, but the friction coefficient between the filler and TiBw/Ti-6Al-4V composite and the canning shape were critical to the tube precision. The microstructure and mechanical performance for the as-extruded TiBw/Ti-6Al-4V composite tubes were systematically investigated. After extrusion, the transverse section microstructure of the TiBw/Ti6Al4V composite tube remained quasi-continuous and the TiBw were rotated to align the extrusion direction. Moreover, the tensile strength and elongation reached 1240 MPa and 13.5%, resulting from dynamic recrystallization and whisker rotation. Full article

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19 pages, 10367 KiB

Open AccessArticle

Effects of Electrospun Carbon Nanofibers’ Interlayers on High-Performance Lithium–Sulfur Batteries

by Tianji Gao³, TrungHieu Le², Ying Yang^1,2,*

, Zhihao Yu¹, Zhenghong Huang⁴ and Feiyu Kang⁴

¹ Department of Electrical Engineering, Tsinghua University, Beijing 100084, China

² State Key Laboratory of Power System, Tsinghua University, Beijing 100084, China

³ Department of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083, China

⁴ Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

Materials 2017, 10(4), 376; https://doi.org/10.3390/ma10040376 - 31 Mar 2017

Cited by 40 | Viewed by 9389

Abstract

Two different interlayers were introduced in lithium–sulfur batteries to improve the cycling stability with sulfur loading as high as 80% of total mass of cathode. Melamine was recommended as a nitrogen-rich (N-rich) amine component to synthesize a modified polyacrylic acid (MPAA). The electrospun [...] Read more.

Two different interlayers were introduced in lithium–sulfur batteries to improve the cycling stability with sulfur loading as high as 80% of total mass of cathode. Melamine was recommended as a nitrogen-rich (N-rich) amine component to synthesize a modified polyacrylic acid (MPAA). The electrospun MPAA was carbonized into N-rich carbon nanofibers, which were used as cathode interlayers, while carbon nanofibers from PAA without melamine was used as an anode interlayer. At the rate of 0.1 C, the initial discharge capacity with two interlayers was 983 mAh g⁻¹, and faded down to 651 mAh g⁻¹ after 100 cycles with the coulombic efficiency of 95.4%. At the rate of 1 C, the discharge capacity was kept to 380 mAh g⁻¹ after 600 cycles with a coulombic efficiency of 98.8%. It apparently demonstrated that the cathode interlayer is extremely effective at shutting down the migration of polysulfide ions. The anode interlayer induced the lithium ions to form uniform lithium metal deposits confined on the fiber surface and in the bulk to strengthen the cycling stability of the lithium metal anode. Full article

(This article belongs to the Special Issue Materials for Electrochemical Capacitors and Batteries)

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20 pages, 4085 KiB

Open AccessArticle

Manufacturing Technology of Composite Materials—Principles of Modification of Polymer Composite Materials Technology Based on Polytetrafluoroethylene

by Anton Panda^1,*

, Kostiantyn Dyadyura², Jan Valíček^3,4, Marta Harničárová³, Jozef Zajac¹, Vladimír Modrák¹

, Iveta Pandová¹, Peter Vrábel¹, Ema Nováková-Marcinčínová¹ and Zdeněk Pavelek⁵

¹ Faculty of Manufacturing Technologies with a seat in Prešov, Technical University of Kosice, Bayerova 1, 080 01 Prešov, Slovakia

² Department of Applied Materials Science and Technology of Constructional Materials, Faculty of Technical Systems and Energy Efficient Technologies, Sumy State University, 40007 Sumy, Ukraine

³ Institute of Physics, Faculty of Mining and Geology, VŠB—Technical University of Ostrava, 17. Listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic

⁴ RMTVC, Faculty of Metallurgy and Materials Engineering, VŠB—Technical University of Ostrava, 17. Listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic

⁵ OKD, HBZS, a.s., Ostrava—Radvanice 716 00, Czech Republic

Materials 2017, 10(4), 377; https://doi.org/10.3390/ma10040377 - 31 Mar 2017

Cited by 37 | Viewed by 8305

Abstract

The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE) filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence [...] Read more.

The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE) filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence the significant improvement of physicomechanical characteristics. The results of this research allow stating that interfacial and surface phenomena of the polymer–solid interface and composition play a decisive role in PTFE composites properties. Fillers hinder the relative movement of the PTFE molecules past one another and, in this way, reduce creep or deformation of the parts, reducing the wear rate of parts used in dynamic applications as well as the coefficient of thermal expansion. The necessary structural parameters of such polymer composites are provided by regimes of process equipment. Full article

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22 pages, 13873 KiB

Open AccessArticle

Numerical Studies on the Failure Process of Heterogeneous Brittle Rocks or Rock-Like Materials under Uniaxial Compression

by Songfeng Guo¹, Shengwen Qi^1,2,*, Yu Zou^1,2 and Bowen Zheng^1,2

¹ Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

² University of Chinese Academy of Sciences, Beijing 100049, China

Materials 2017, 10(4), 378; https://doi.org/10.3390/ma10040378 - 1 Apr 2017

Cited by 42 | Viewed by 6530

Abstract

In rocks or rock-like materials, the constituents, e.g. quartz, calcite and biotite, as well as the microdefects have considerably different mechanical properties that make such materials heterogeneous at different degrees. The failure of materials subjected to external loads is a cracking process accompanied [...] Read more.

In rocks or rock-like materials, the constituents, e.g. quartz, calcite and biotite, as well as the microdefects have considerably different mechanical properties that make such materials heterogeneous at different degrees. The failure of materials subjected to external loads is a cracking process accompanied with stress redistribution due to material heterogeneity. However, the latter cannot be observed from the experiments in laboratory directly. In this study, the cracking and stress features during uniaxial compression process are numerically studied based on a presented approach. A plastic strain dependent strength model is implemented into the continuous numerical tool—Fast Lagrangian Analysis of Continua in three Dimensions (FLAC^3D), and the Gaussian statistical function is adopted to depict the heterogeneity of mechanical parameters including elastic modulus, friction angle, cohesion and tensile strength. The mean parameter μ and the coefficient of variance (h_cv, the ratio of mean parameter to standard deviation) in the function are used to define the mean value and heterogeneity degree of the parameters, respectively. The results show that this numerical approach can perfectly capture the general features of brittle materials including fracturing process, AE events as well as stress-strain curves. Furthermore, the local stress disturbance is analyzed and the crack initiation stress threshold is identified based on the AE events process and stress-strain curves. It is shown that the stress concentration always appears in the undamaged elements near the boundary of damaged sites. The peak stress and crack initiation stress are both heterogeneity dependent, i.e., a linear relation exists between the two stress thresholds and h_cv. The range of h_cv is suggested as 0.12 to 0.21 for most rocks. The stress concentration degree is represented by a stress concentration factor and found also heterogeneity dominant. Finally, it is found that there exists a consistent tendency between the local stress difference and the AE events process. Full article

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

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22 pages, 16452 KiB

Open AccessFeature PaperArticle

Discrete Particle Method for Simulating Hypervelocity Impact Phenomena

by Erkai Watson¹ and Martin O. Steinhauser^1,2,*

¹ Department of Systems Solutions, Fraunhofer–Institute for High–Speed Dynamics, Ernst–Mach–Institut,EMI, Eckerstrasse 4, 79104 Freiburg, Germany

² Department of Chemistry, Faculty of Science, University of Basel, Klingelbergstrasse 80, CH-4056, Basel,Switzerland

Materials 2017, 10(4), 379; https://doi.org/10.3390/ma10040379 - 2 Apr 2017

Cited by 20 | Viewed by 7994

Abstract

In this paper, we introduce a computational model for the simulation of hypervelocity impact (HVI) phenomena which is based on the Discrete Element Method (DEM). Our paper constitutes the first application of DEM to the modeling and simulating of impact events for velocities [...] Read more.

In this paper, we introduce a computational model for the simulation of hypervelocity impact (HVI) phenomena which is based on the Discrete Element Method (DEM). Our paper constitutes the first application of DEM to the modeling and simulating of impact events for velocities beyond 5 kms^-1. We present here the results of a systematic numerical study on HVI of solids. For modeling the solids, we use discrete spherical particles that interact with each other via potentials. In our numerical investigations we are particularly interested in the dynamics of material fragmentation upon impact. We model a typical HVI experiment configuration where a sphere strikes a thin plate and investigate the properties of the resulting debris cloud. We provide a quantitative computational analysis of the resulting debris cloud caused by impact and a comprehensive parameter study by varying key parameters of our model. We compare our findings from the simulations with recent HVI experiments performed at our institute. Our findings are that the DEM method leads to very stable, energy–conserving simulations of HVI scenarios that map the experimental setup where a sphere strikes a thin plate at hypervelocity speed. Our chosen interaction model works particularly well in the velocity range where the local stresses caused by impact shock waves markedly exceed the ultimate material strength. Full article

(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)

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19 pages, 2704 KiB

Open AccessArticle

Investigation of the Defect Structure of Congruent and Fe-Doped LiNbO₃ Powders Synthesized by the Combustion Method

by You-Yun Li¹, Hao-Long Chen², Guo-Ju Chen³, Chia-Liang Kuo¹, Ping-Hung Hsieh¹ and Weng-Sing Hwang^1,*

¹ Department of Materials Science and Engineering, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan

² Department of Electronic Engineering, Kao Yuan University, No. 1821, Jhongshan Road, Lujhu District, Kaohsiung 82151, Taiwan

³ Department of Materials Science and Engineering, I-Shou University, No.1, Sec. 1, Syuecheng Road, Dashu District, Kaohsiung 84001, Taiwan

Materials 2017, 10(4), 380; https://doi.org/10.3390/ma10040380 - 2 Apr 2017

Cited by 12 | Viewed by 4073

Abstract

Fe-doped LiNbO₃ synthesized by the combustion method to seek new multiferroic materials exhibits room-temperature ferromagnetism, as reported in our previous work [1]. In this work, the defect structure of congruent and Fe-doped LiNbO₃ (0.57–3.3 mol %) powders was investigated in detail [...] Read more.

Fe-doped LiNbO₃ synthesized by the combustion method to seek new multiferroic materials exhibits room-temperature ferromagnetism, as reported in our previous work [1]. In this work, the defect structure of congruent and Fe-doped LiNbO₃ (0.57–3.3 mol %) powders was investigated in detail by several methods. The molar ratio of [Li]/([Li]+[Nb]) was determined by the Curie temperature (T_c) via DSC. Two peaks of T_c were observed due to phase splitting [2], and the phase at lower T_c disappears as the Fe doping concentration increases. The coexistence of two different oxidation states of Fe ions in LiNbO₃ was probed by XPS and UV-Vis spectroscopy. The Raman spectra exhibit displacements along the c axis of Li and Nb ions, and a deformation of the NbO₆ framework owing to Fe doping. Several doping models were applied in the Rietveld refinement of powder X-ray diffraction collected by synchrotron radiation. The fitting by the Nb vacancy model leads to an improbably distorted structure of congruent LiNbO₃. In Fe-doped LiNbO₃, we conjecture that Li and Nb vacancies coexist in the lattice structure; Fe⁺²/Fe⁺³ ions are substituted for Li ions at the regular Li site and may push the anti-site NbLi ion back to the regular Nb site. Full article

(This article belongs to the Special Issue Inorganic Solid State and Materials Chemistry)

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15 pages, 2842 KiB

Open AccessArticle

Effect of the Fabrication Parameters of the Nanosphere Lithography Method on the Properties of the Deposited Au-Ag Nanoparticle Arrays

by Jing Liu¹, Chaoyang Chen¹, Guangsong Yang¹, Yushan Chen¹ and Cheng-Fu Yang^2,*

¹ School of Information Engineering, Jimei University, Xiamen 361021, China

² Department of Chemical and Materials Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Nan-Tzu District, Kaohsiung 811, Taiwan

Materials 2017, 10(4), 381; https://doi.org/10.3390/ma10040381 - 3 Apr 2017

Cited by 14 | Viewed by 6852

Abstract

The nanosphere lithography (NSL) method can be developed to deposit the Au-Ag triangle hexagonal nanoparticle arrays for the generation of localized surface plasmon resonance. Previously, we have found that the parameters used to form the NSL masks and the physical methods required to [...] Read more.

The nanosphere lithography (NSL) method can be developed to deposit the Au-Ag triangle hexagonal nanoparticle arrays for the generation of localized surface plasmon resonance. Previously, we have found that the parameters used to form the NSL masks and the physical methods required to deposit the Au-Ag thin films had large effects on the geometry properties of the nanoparticle arrays. Considering this, the different parameters used to grow the Au-Ag triangle hexagonal nanoparticle arrays were investigated. A single‐layer NSL mask was formed by using self‐assembly nano-scale polystyrene (PS) nanospheres with an average radius of 265 nm. At first, the concentration of the nano-scale PS nanospheres in the solution was set at 6 wt %. Two coating methods, drop-coating and spin-coating, were used to coat the nano-scale PS nanospheres as a single‐layer NSL mask. From the observations of scanning electronic microscopy (SEM), we found that the matrixes of the PS nanosphere masks fabricated by using the drop-coating method were more uniform and exhibited a smaller gap than those fabricated by the spin-coating method. Next, the drop-coating method was used to form the single‐layer NSL mask and the concentration of nano-scale PS nanospheres in a solution that was changed from 4 to 10 wt %, for further study. The SEM images showed that when the concentrations of PS nanospheres in the solution were 6 and 8 wt %, the matrixes of the PS nanosphere masks were more uniform than those of 4 and 10 wt %. The effects of the one-side lifting angle of substrates and the vaporization temperature for the solvent of one-layer self-assembly PS nanosphere thin films, were also investigated. Finally, the concentration of the nano-scale PS nanospheres in the solution was set at 8 wt % to form the PS nanosphere masks by the drop-coating method. Three different physical deposition methods, including thermal evaporation, radio-frequency magnetron sputtering, and e-gun deposition, were used to deposit the Au-Ag triangle hexagonal periodic nanoparticle arrays. The SEM images showed that as the single-layer PS nanosphere mask was well controlled, the thermal evaporation could deposit the Au-Ag triangle hexagonal nanoparticle arrays with a higher quality than the other two methods. Full article

(This article belongs to the Special Issue Selected Material Related Papers from ICI2016)

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15 pages, 2890 KiB

Open AccessArticle

A Life Prediction Model of Multilayered PTH Based on Fatigue Mechanism

by Yaqiu Li^1,†, Weiwei Hu^1,2,*,†

, Yufeng Sun¹, Zili Wang¹ and Ali Mosleh²

¹ Reliability and System Engineering School, Beihang University, Haidian District, Beijing 100191, China

² B. John Garrick Institute for the Risk Sciences, University of California, Los Angeles, CA 90095, USA

^† These authors contributed equally to this work.

Materials 2017, 10(4), 382; https://doi.org/10.3390/ma10040382 - 4 Apr 2017

Cited by 5 | Viewed by 4570

Abstract

Plated through hole (PTH) plays a critical role in printed circuit board (PCB) reliability. Thermal fatigue deformation of the PTH material is regarded as the primary factor affecting the lifetime of electrical devices. Numerous research efforts have focused on the failure mechanism model [...] Read more.

Plated through hole (PTH) plays a critical role in printed circuit board (PCB) reliability. Thermal fatigue deformation of the PTH material is regarded as the primary factor affecting the lifetime of electrical devices. Numerous research efforts have focused on the failure mechanism model of PTH. However, most of the existing models were based on the one-dimensional structure hypothesis without taking the multilayered structure and external pad into consideration. In this paper, the constitutive relation of multilayered PTH is developed to establish the stress equation, and finite element analysis (FEA) is performed to locate the maximum stress and simulate the influence of the material properties. Finally, thermal cycle tests are conducted to verify the accuracy of the life prediction results. This model could be used in fatigue failure portable diagnosis and for life prediction of multilayered PCB. Full article

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6 pages, 1351 KiB

Open AccessArticle

Plasmonic Colour Filters Based on Coaxial Holes in Aluminium

by Ranjith Rajasekharan Unnithan^1,*, Miao Sun¹, Xin He¹, Eugeniu Balaur², Alexander Minovich³, Dragomir N. Neshev³, Efstratios Skafidas¹ and Ann Roberts⁴

¹ Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia

² Melbourne Centre for Nanofabrication, Australian National Fabrication Facility, Clayton, VIC 3168, Australia

³ Nonlinear Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601, Australia

⁴ School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia

Materials 2017, 10(4), 383; https://doi.org/10.3390/ma10040383 - 4 Apr 2017

Cited by 26 | Viewed by 4667

Abstract

Aluminum is an alternative plasmonic material in the visible regions of the spectrum due to its attractive properties such as low cost, high natural abundance, ease of processing, and complementary metal-oxide-semiconductor (CMOS) and liquid crystal display (LCD) compatibility. Here, we present plasmonic colour [...] Read more.

Aluminum is an alternative plasmonic material in the visible regions of the spectrum due to its attractive properties such as low cost, high natural abundance, ease of processing, and complementary metal-oxide-semiconductor (CMOS) and liquid crystal display (LCD) compatibility. Here, we present plasmonic colour filters based on coaxial holes in aluminium that operate in the visible range. Using both computational and experimental methods, fine-tuning of resonance peaks through precise geometric control of the coaxial holes is demonstrated. These results will lay the basis for the development of filters in high-resolution liquid crystal displays, RGB-spatial light modulators, liquid crystal over silicon devices and novel displays. Full article

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15 pages, 6936 KiB

Open AccessArticle

Effect and Stability of Poly(Amido Amine)-Induced Biomineralization on Dentinal Tubule Occlusion

by Yuan Gao^1,2, Kunneng Liang^1,2, Jianshu Li³, He Yuan^1,2, Hongling Liu^1,2, Xiaolei Duan^1,2 and Jiyao Li^1,2,*

¹ State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China

² Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China

³ Department of Biomedical Polymers and Artificial Organs, College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, China

Materials 2017, 10(4), 384; https://doi.org/10.3390/ma10040384 - 5 Apr 2017

Cited by 25 | Viewed by 5627

Abstract

In recent years, scientists have developed various biomaterials to remineralize human teeth to treat dentine hypersensitivity. Poly(amido amine) (PAMAM) dendrimers have become a research focus in this field. It has been demonstrated that PAMAM is able to create precipitates both on the surface [...] Read more.

In recent years, scientists have developed various biomaterials to remineralize human teeth to treat dentine hypersensitivity. Poly(amido amine) (PAMAM) dendrimers have become a research focus in this field. It has been demonstrated that PAMAM is able to create precipitates both on the surface of and within the dentinal tubules, however, there is little information about its effect on reducing dentine permeability in vitro. This study aimed to evaluate the in vitro effectiveness and stability of the fourth generation amine-terminated PAMAM on dentinal tubule occlusion, especially on dentine permeability. Sodium fluoride (NaF), which has been widely used as a desensitizing agent, is regarded as positive control. Demineralized sensitive dentine samples were coated with PAMAM or sodium fluoride solutions and soaked in artificial saliva (AS) at 37 °C for different periods. Four weeks later, samples in each group were then equally split into two subgroups for testing using a brushing challenge and an acid challenge. Dentine permeability of each specimen was measured before and after each challenge using a fluid filtration system. Dentine morphology and surface deposits were characterized by scanning electron microscope (SEM) and analyzed with Image-Pro Plus software. Data were evaluated through multifactorial ANOVA with repeated measures and pair-wise comparisons at a level of 5%. The results showed that PAMAM and NaF significantly reduced dentine permeability to 25.1% and 20.7%. Both of them created precipitates on dentine surfaces after AS immersion for 28 days. PAMAM-induced biomineralization not only on dentine surfaces, but also deeper in dentinal tubules, significantly reduced dentine permeability. Moreover, PAMAM-induced biomineralization elicited excellent stable occlusion effects after acid challenge. In conclusion, PAMAM demonstrated a strong ability to resist acid and showed great potential to be used in the treatment of dentine hypersensitivity in future. Full article

(This article belongs to the Section Biomaterials)

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7 pages, 3456 KiB

Open AccessArticle

The Microstructural Evolution of Vacuum Brazed 1Cr18Ni9Ti Using Various Filler Metals

by Yunxia Chen^1,2,*

, Haichao Cui², Binfeng Lu¹ and Fenggui Lu²

¹ School of Mechanical Engineering, Shanghai Dianji University, Shanghai 201306, China

² Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, China

Materials 2017, 10(4), 385; https://doi.org/10.3390/ma10040385 - 5 Apr 2017

Cited by 11 | Viewed by 5263

Abstract

The microstructures and weldability of a brazed joint of 1Cr18Ni9Ti austenitic stainless steel with BNi-2, BNi82CrSiBFe and BMn50NiCuCrCo filler metals in vacuum were investigated. It can be observed that an interdiffusion region existed between the filler metal and the base metal for the [...] Read more.

The microstructures and weldability of a brazed joint of 1Cr18Ni9Ti austenitic stainless steel with BNi-2, BNi82CrSiBFe and BMn50NiCuCrCo filler metals in vacuum were investigated. It can be observed that an interdiffusion region existed between the filler metal and the base metal for the brazed joint of Ni-based filler metals. The width of the interdiffusion region was about 10 μm, and the microstructure of the brazed joint of BNi-2 filler metal was dense and free of obvious defects. In the case of the brazed joint of BMn50NiCuCrCo filler metal, there were pits, pores and crack defects in the brazing joint due to insufficient wettability of the filler metal. Crack defects can also be observed in the brazed joint of BNi82CrSiBFe filler metal. Compared with BMn50NiCuCrCo and BNi82CrSiBFe filler metals, BNi-2 filler metal is the best material for 1Cr18Ni9Ti austenitic stainless steel vacuum brazing because of its distinct weldability. Full article

(This article belongs to the Special Issue Welding, Joining and Casting of Advanced Materials)

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17 pages, 3676 KiB

Open AccessArticle

A Practical Approach to Evaluate Lattice Thermal Conductivity in Two-Phase Thermoelectric Alloys for Energy Applications

by Yaron Amouyal

Department of Materials Science and Engineering, Technion–Israel Institute of Technology, 32000 Haifa, Israel

Materials 2017, 10(4), 386; https://doi.org/10.3390/ma10040386 - 5 Apr 2017

Cited by 9 | Viewed by 5252

Abstract

Modelling of the effects of materials’ microstructure on thermal transport is an essential tool for materials design, and is particularly relevant for thermoelectric (TE) materials converting heat into electrical energy. Precipitates dispersed in a TE matrix act as phonon-scattering centers, thereby reducing thermal [...] Read more.

Modelling of the effects of materials’ microstructure on thermal transport is an essential tool for materials design, and is particularly relevant for thermoelectric (TE) materials converting heat into electrical energy. Precipitates dispersed in a TE matrix act as phonon-scattering centers, thereby reducing thermal conductivity. We introduce a practical approach to tailor a definite precipitate size distribution for a given TE matrix, and implement it for PbTe. We evaluate vibrational properties from first principles, and develop an expression for phonon relaxation time that considers both matrix vibrational properties and precipitate size distribution. This provides us with guidelines for optimizing thermal conductivity. Full article

(This article belongs to the Special Issue Thermal Sciences and Thermodynamics of Materials)

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15 pages, 3664 KiB

Open AccessFeature PaperArticle

A Shell Model for Free Vibration Analysis of Carbon Nanoscroll

by Amin Taraghi Osguei¹, Mohamad Taghi Ahmadian^1,2,*, Mohsen Asghari¹ and Nicola Maria Pugno^3,4,5

¹ Department of Mechanical Engineering, Sharif University of Technology, 11365-11155 Tehran, Iran

² Center of Excellence in Design, Robotics and Automation (CEDRA), Sharif University of Technology, 11365-9567 Tehran, Iran

³ Laboratory of Bio-Inspired and Graphene Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38123 Trento, Italy

⁴ School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK

⁵ Ket-Lab, Italian Space Agency, Via del Politecnico s.n.c., 00133 Rome, Italy

Materials 2017, 10(4), 387; https://doi.org/10.3390/ma10040387 - 6 Apr 2017

Cited by 6 | Viewed by 5144

Abstract

Carbon nanoscroll (CNS) is a graphene sheet rolled into a spiral structure with great potential for different applications in nanotechnology. In this paper, an equivalent open shell model is presented to study the vibration behavior of a CNS with arbitrary boundary conditions. The [...] Read more.

Carbon nanoscroll (CNS) is a graphene sheet rolled into a spiral structure with great potential for different applications in nanotechnology. In this paper, an equivalent open shell model is presented to study the vibration behavior of a CNS with arbitrary boundary conditions. The equivalent parameters used for modeling the carbon nanotubes are implemented to simulate the CNS. The interactions between the layers of CNS due to van der Waals forces are included in the model. The uniformly distributed translational and torsional springs along the boundaries are considered to achieve a unified solution for different boundary conditions. To study the vibration characteristics of CNS, total energy including strain energy, kinetic energy, and van der Waals energy are minimized using the Rayleigh-Ritz technique. The first-order shear deformation theory has been utilized to model the shell. Chebyshev polynomials of first kind are used to obtain the eigenvalue matrices. The natural frequencies and corresponding mode shapes of CNS in different boundary conditions are evaluated. The effect of electric field in axial direction on the natural frequencies and mode shapes of CNS is investigated. The results indicate that, as the electric field increases, the natural frequencies decrease. Full article

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18 pages, 5444 KiB

Open AccessArticle

Analysis of the Mechanical Behavior, Creep Resistance and Uniaxial Fatigue Strength of Martensitic Steel X46Cr13

by Josip Brnic^1,*, Sanjin Krscanski¹

, Domagoj Lanc¹, Marino Brcic¹

, Goran Turkalj¹, Marko Canadija¹ and Jitai Niu^2,3

¹ Department of Engineering Mechanics, Faculty of Engineering, University of Rijeka, Vukovarska 51, 51000 Rijeka, Croatia

² School of Materials Science and Engineering, Harbin Institute of Technology, XiDaZhi Street 92#, Nangang District, Harbin 150001, China

³ School of Materials Science and Engineering, Henan Polytechnic University, No 2001, Century Avenue, Jiaozuo 454003, China

Materials 2017, 10(4), 388; https://doi.org/10.3390/ma10040388 - 6 Apr 2017

Cited by 14 | Viewed by 6811

Abstract

The article deals with the analysis of the mechanical behavior at different temperatures, uniaxial creep and uniaxial fatigue of martensitic steel X46Cr13 (1.4034, AISI 420). For the purpose of considering the aforementioned mechanical behavior, as well as determining the appropriate resistance to creep [...] Read more.

The article deals with the analysis of the mechanical behavior at different temperatures, uniaxial creep and uniaxial fatigue of martensitic steel X46Cr13 (1.4034, AISI 420). For the purpose of considering the aforementioned mechanical behavior, as well as determining the appropriate resistance to creep and fatigue strength levels, numerous uniaxial tests were carried out. Tests related to mechanical properties performed at different temperatures are presented in the form of engineering stress-strain diagrams. Short-time creep tests performed at different temperatures and different stress levels are presented in the form of creep curves. Fatigue tests carried out at stress ratios

R = 0.25

and

R = - 1

are shown in the form of S–N (fatigue) diagrams. The finite fatigue regime for each of the mentioned stress ratios is modeled by an inclined log line, while the infinite fatigue regime is modeled by a horizontal line, which represents the fatigue limit of the material and previously was calculated by the modified staircase method. Finally, the fracture toughness has been calculated based on the Charpy V-notch impact energy. Full article

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13 pages, 15670 KiB

Open AccessArticle

The Effect of Milling Time on the Microstructural Characteristics and Strengthening Mechanisms of NiMo-SiC Alloys Prepared via Powder Metallurgy

by Chao Yang^1,2, Ondrej Muránsky^3,4,*, Hanliang Zhu³

, Gordon J. Thorogood³, Maxim Avdeev³, Hefei Huang^1,* and Xingtai Zhou¹

¹ Shanghai Institute of Applied Physics, Chinese Academy of Sciences (CAS), Shanghai 201800, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia

⁴ School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia

Materials 2017, 10(4), 389; https://doi.org/10.3390/ma10040389 - 6 Apr 2017

Cited by 7 | Viewed by 4515

Abstract

A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 [...] Read more.

A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni₃Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo₂C particles during sintering. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process. Full article

(This article belongs to the Section Energy Materials)

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11 pages, 4927 KiB

Open AccessArticle

Preparation and Optical Properties of Infrared Transparent 3Y-TZP Ceramics

by Chuanfeng Wang^1,2, Xiaojian Mao^2,*, Ya-Pei Peng^2,3, Benxue Jiang², Jintai Fan², Yangyang Xu^1,2, Long Zhang^2,* and Jingtai Zhao^1,*

¹ State Key Laboratory of Advanced Special Steel, Shanghai Key Laboratory of Advanced Ferrometallurgy, School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China

² Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

³ Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China

Materials 2017, 10(4), 390; https://doi.org/10.3390/ma10040390 - 7 Apr 2017

Cited by 18 | Viewed by 5495

Abstract

In the present study, a tough tetragonal zirconia polycrystalline (Y-TZP) material was developed for use in high-speed infrared windows and domes. The influence of the preparation procedure and the microstructure on the material’s optical properties was evaluated by SEM and FT-IR spectroscopy. It [...] Read more.

In the present study, a tough tetragonal zirconia polycrystalline (Y-TZP) material was developed for use in high-speed infrared windows and domes. The influence of the preparation procedure and the microstructure on the material’s optical properties was evaluated by SEM and FT-IR spectroscopy. It was revealed that a high transmittance up to 77% in the three- to five-micrometer IR region could be obtained when the sample was pre-sintered at 1225 °C and subjected to hot isostatic pressing (HIP) at 1275 °C for two hours. The infrared transmittance and emittance at elevated temperature were also examined. The in-line transmittance remained stable as the temperature increased to 427 °C, with degradation being observed only near the infrared cutoff edge. Additionally, the emittance property of 3Y-TZP ceramic at high temperature was found to be superior to those of sapphire and spinel. Overall, the results indicate that Y-TZP ceramic is a potential candidate for high-speed infrared windows and domes. Full article

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

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15 pages, 6443 KiB

Open AccessArticle

Design and Preparation of Carbon Based Composite Phase Change Material for Energy Piles

by Haibin Yang¹, Shazim Ali Memon², Xiaohua Bao^1,*

, Hongzhi Cui¹ and Dongxu Li¹

¹ College of Civil Engineering, Shenzhen University, Shenzhen 518060, China

² Department of Civil Engineering, School of Engineering, Nazarbayev University, Astana 010000, Kazakhstan

Materials 2017, 10(4), 391; https://doi.org/10.3390/ma10040391 - 7 Apr 2017

Cited by 37 | Viewed by 6325

Abstract

Energy piles—A fairly new renewable energy concept—Use a ground heat exchanger (GHE) in the foundation piles to supply heating and cooling loads to the supported building. Applying phase change materials (PCMs) to piles can help in maintaining a stable temperature within the piles [...] Read more.

Energy piles—A fairly new renewable energy concept—Use a ground heat exchanger (GHE) in the foundation piles to supply heating and cooling loads to the supported building. Applying phase change materials (PCMs) to piles can help in maintaining a stable temperature within the piles and can then influence the axial load acting on the piles. In this study, two kinds of carbon-based composite PCMs (expanded graphite-based PCM and graphite nanoplatelet-based PCM) were prepared by vacuum impregnation for potential application in energy piles. Thereafter, a systematic study was performed and different characterization tests were carried out on two composite PCMs. The composite PCMs retained up to 93.1% of paraffin and were chemically compatible, thermally stable and reliable. The latent heat of the composite PCM was up to 152.8 J/g while the compressive strength of cement paste containing 10 wt % GNP-PCM was found to be 37 MPa. Hence, the developed composite PCM has potential for thermal energy storage applications. Full article

(This article belongs to the Section Energy Materials)

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12 pages, 5852 KiB

Open AccessArticle

Optical Design of Textured Thin-Film CIGS Solar Cells with Nearly-Invisible Nanowire Assisted Front Contacts

by Joop Van Deelen^1,*, Ahmed Omar¹ and Marco Barink²

¹ TNO/Solliance, High Tech Campus 21, 5656 AE Eindhoven, The Netherlands

² TNO/Holst, High Tech Campus 31, 5656 AE Eindhoven, The Netherlands

Materials 2017, 10(4), 392; https://doi.org/10.3390/ma10040392 - 7 Apr 2017

Cited by 12 | Viewed by 5153

Abstract

The conductivity of transparent front contacts can be improved by patterned metallic nanowires, albeit at the cost of optical loss. The associated optical penalty can be strongly reduced by texturization of the cell stack. Remarkably, the nanowires themselves are not textured and not [...] Read more.

The conductivity of transparent front contacts can be improved by patterned metallic nanowires, albeit at the cost of optical loss. The associated optical penalty can be strongly reduced by texturization of the cell stack. Remarkably, the nanowires themselves are not textured and not covered in our design. This was shown by optical modeling where the width of the nanowire, the texture height and the texture period were varied in order to obtain a good insight into the general trends. The optical performance can be improved dramatically as the reflection, which is the largest optical loss, can be reduced by 95% of the original value. The spectra reveal absorption in the Cu(In,Ga)Se₂ (CIGS) layer of 95% and reflection below 2% over a large part of the spectrum. In essence, a virtually black CIGS cell stack can be achieved for textured cells with a metal nanogrid. Moreover, it turned out that the ratio between the width of the nanowire and the height of the texture is a critical parameter for optical losses. Full article

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

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14 pages, 2347 KiB

Open AccessArticle

Characterization and Thermal Stability of Acetylated Slicewood Production by Alkali-Catalyzed Esterification

by Ke-Chang Hung, Chen-Ning Yang, Teng-Chun Yang, Tung-Lin Wu, Yong-Long Chen and Jyh-Horng Wu^*

Department of Forestry, National Chung Hsing University, Taichung 402, Taiwan

Materials 2017, 10(4), 393; https://doi.org/10.3390/ma10040393 - 7 Apr 2017

Cited by 13 | Viewed by 3436

Abstract

This study was compared and characterized two different alkali (potassium carbonate (PC) and potassium acetate (PA))-catalyzed acetylations of slicewood with vinyl acetate (VA) by a vapor phase reaction. The results revealed that the esterification reaction between VA and the hydroxyl groups of slicewood [...] Read more.

This study was compared and characterized two different alkali (potassium carbonate (PC) and potassium acetate (PA))-catalyzed acetylations of slicewood with vinyl acetate (VA) by a vapor phase reaction. The results revealed that the esterification reaction between VA and the hydroxyl groups of slicewood could be improved by using PC or PA as a catalyst. Additionally, a significant weight percent gain was obtained after VA acetylation with 5% of catalyst. Furthermore, the reactivity of the cellulose hydroxyl groups for VA acetylation was more pronounced at the C2 reactive site compared to acetylation with acetic anhydride. On the other hand, the apparent activation energy of thermal decomposition between 10% and 70% conversion is 174–183, 194–200, and 183–186 kJ/mol for unmodified slicewood and VA-acetylated slicewood with PC and PA, respectively. Accordingly, the thermal stability of the slicewood could be effectively enhanced by VA acetylation, especially for using the PC as a catalyst. Full article

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12 pages, 3170 KiB

Open AccessArticle

Creep Behavior of Poly(lactic acid) Based Biocomposites

by Marco Morreale^1,*

, Maria Chiara Mistretta²

and Vincenzo Fiore²

¹ Faculty of Engineering and Architecture, Kore University of Enna, Enna 94100, Italy

² Department of Civil, Environmental, Aerospace, Materials Engineering, University of Palermo, Palermo 90128, Italy

Materials 2017, 10(4), 395; https://doi.org/10.3390/ma10040395 - 8 Apr 2017

Cited by 26 | Viewed by 5154

Abstract

Polymer composites containing natural fibers are receiving growing attention as possible alternatives for composites containing synthetic fibers. The use of biodegradable matrices obtained from renewable sources in replacement for synthetic ones is also increasing. However, only limited information is available about the creep [...] Read more.

Polymer composites containing natural fibers are receiving growing attention as possible alternatives for composites containing synthetic fibers. The use of biodegradable matrices obtained from renewable sources in replacement for synthetic ones is also increasing. However, only limited information is available about the creep behavior of the obtained composites. In this work, the tensile creep behavior of PLA based composites, containing flax and jute twill weave woven fabrics, produced through compression molding, was investigated. Tensile creep tests were performed at different temperatures (i.e., 40 and 60 °C). The results showed that the creep behavior of the composites is strongly influenced by the temperature and the woven fabrics used. As preliminary characterization, quasi-static tensile tests and dynamic mechanical tests were carried out on the composites. Furthermore, fabrics (both flax and jute) were tested as received by means of quasi-static tests and creep tests to evaluate the influence of fabrics mechanical behavior on the mechanical response of the resulting composites. The morphological analysis of the fracture surface of the tensile samples showed the better fiber-matrix adhesion between PLA and jute fabric. Full article

(This article belongs to the Section Advanced Composites)

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20 pages, 5555 KiB

Open AccessArticle

The Brittleness and Chemical Stability of Optimized Geopolymer Composites

by Michaela Steinerova^1,*, Lenka Matulova^1,2, Pavel Vermach³ and Jindrich Kotas⁴

¹ Institute of Rock Structure and Mechanics, Academy of Sciences Czech Republic, v.v.i., Prague 18209, Czech Republic

² Department of Glass and Ceramics, Institute of Chemical Technology (ICT) in Prague, Prague 16628, Czech Republic

³ Faculty of Civil Engineering, Czech Technical University in Prague (CTU), Prague 16636, Czech Republic

⁴ Department of Water Technology and Environmental Engineering, Institute of Chemical Technology (ICT) in Prague, Prague 16628, Czech Republic

Materials 2017, 10(4), 396; https://doi.org/10.3390/ma10040396 - 9 Apr 2017

Cited by 39 | Viewed by 6605

Abstract

Geopolymers are known as high strength and durable construction materials but have a brittle fracture. In practice, this results in a sudden collapse at ultimate load, without any chance of preventing the breakdown of parts or of withstanding the stress for some time. [...] Read more.

Geopolymers are known as high strength and durable construction materials but have a brittle fracture. In practice, this results in a sudden collapse at ultimate load, without any chance of preventing the breakdown of parts or of withstanding the stress for some time. Glass fiber usage as a total anisotropic shape acting as a compact structure component should hinder the fracture mechanism. The optimized compositions in this study led to a significant reinforcement, especially in the case of flexural strength, but also in terms of the compressive strength and notch toughness. The positive and negative influence of the fibers on the complex composite properties provided chemical stability. Full article

(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)

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15 pages, 7167 KiB

Open AccessArticle

Failure Mechanisms of the Coating/Metal Interface in Waterborne Coatings: The Effect of Bonding

by Hongxia Wan¹, Dongdong Song^1,2,*, Xiaogang Li^1,3,*, Dawei Zhang¹, Jin Gao¹ and Cuiwei Du¹

¹ Institute for advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China

² Aerospace Research Institute of Materials and Processing Technology, Beijing 100076, China

³ Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China

Materials 2017, 10(4), 397; https://doi.org/10.3390/ma10040397 - 9 Apr 2017

Cited by 34 | Viewed by 5418

Abstract

Waterborne coating is the most popular type of coating, and improving its performance is a key point of research. Cathodic delamination is one of the major modes of failure for organic coatings. It refers to the weakening or loss of adhesion between the [...] Read more.

Waterborne coating is the most popular type of coating, and improving its performance is a key point of research. Cathodic delamination is one of the major modes of failure for organic coatings. It refers to the weakening or loss of adhesion between the coating and substrate. Physical and chemical characteristics of coatings have been studied via scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and secondary ion mass spectrometry (SIMS). Early heterogeneous swelling at the metal-coating interface in non-defective coated metals was elucidated using frequency-dependent alternating-current scanning electrochemical microscopy. Two types of coatings (styrene-acrylic coating and terpolymer coating) were compared. The effects of thickness, surface roughness, and chemical bonding on cathodic delamination were investigated. Full article

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16 pages, 12935 KiB

Open AccessArticle

Interacting Effects Induced by Two Neighboring Pits Considering Relative Position Parameters and Pit Depth

by Yongfang Huang^*, Tieqiang Gang^* and Lijie Chen

School of Aerospace Engineering, Xiamen University, Xiamen 361005, Fujian, China

Materials 2017, 10(4), 398; https://doi.org/10.3390/ma10040398 - 9 Apr 2017

Cited by 9 | Viewed by 4302

Abstract

For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ) and pit depth (d) with the finite [...] Read more.

For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ) and pit depth (d) with the finite element method. According to the severity of the stress concentration, the critical corrosion regions, bearing high susceptibility to fatigue damage, are determined for intersecting and adjacent pits, respectively. A straightforward approach is accordingly proposed to conservatively estimate the combined stress concentration factor induced by two neighboring pits, and a concrete application example is presented. It is found that for intersecting pits, the normalized stress concentration factor K_tnor increases with the increase of θ and λ and always reaches its maximum at θ = 90°, yet for adjacent pits, K_tnor decreases with the increase of λ and the maximum value appears at a slight asymmetric location. The simulations reveal that K_tnor follows a linear and an exponential relationship with the dimensionless depth parameter R_d for intersecting and adjacent cases, respectively. Full article

(This article belongs to the Special Issue Stress Corrosion Cracking in Materials)

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14 pages, 15746 KiB

Open AccessArticle

Effects of Tungsten Addition on the Microstructure and Corrosion Resistance of Fe-3.5B Alloy in Liquid Zinc

by Xin Liu^1,2, Mengmeng Wang³, Fucheng Yin^1,2,*, Xuemei Ouyang^1,2 and Zhi Li^1,2

¹ School of Material Science and Engineering, Xiangtan University, Xiangtan 411105, China

² Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan 411105, China

³ School of Material Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China

Materials 2017, 10(4), 399; https://doi.org/10.3390/ma10040399 - 10 Apr 2017

Cited by 10 | Viewed by 5864

Abstract

The effects of tungsten addition on the microstructure and corrosion resistance of Fe-3.5B alloys in a liquid zinc bath at 520 °C were investigated by means of scanning electron microscopy, X-ray diffraction and electron probe micro-analysis. The microstructure evolution in different alloys is [...] Read more.

The effects of tungsten addition on the microstructure and corrosion resistance of Fe-3.5B alloys in a liquid zinc bath at 520 °C were investigated by means of scanning electron microscopy, X-ray diffraction and electron probe micro-analysis. The microstructure evolution in different alloys is analyzed and discussed using an extrapolated Fe-B-W ternary phase diagram. Experimental results show that there are three kinds of borides, the reticular (Fe, W)₂B, the rod-like (Fe, W)₃B and flower-like FeWB. The addition of tungsten can refine the microstructure and improve the stability of the reticular borides. Besides, it is beneficial to the formation of the metastable (Fe, W)₃B phase. The resultant Fe-3.5B-11W (wt %) alloy possesses excellent corrosion resistance to liquid zinc. When tungsten content exceeds 11 wt %, the formed flower-like FeWB phase destroys the integrity of the reticular borides and results in the deterioration of the corrosion resistance. Also, the corrosion failure resulting from the spalling of borides due to the initiation of micro-cracks in the grain boundary of borides is discussed in this paper. Full article

(This article belongs to the Special Issue Corrosion Studies of Metal Matrix Composites/Alloys at Low and High Temperatures)

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17 pages, 5585 KiB

Open AccessArticle

Preparation and Chemical/Microstructural Characterization of Azacrown Ether-Crosslinked Chitosan Films

by Julius Toeri^1,2,*

, Anayancy Osorio-Madrazo^1,3 and Marie-Pierre Laborie^1,2

¹ Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg, Germany

² Forest Biomaterials, University of Freiburg, Werthmanstr. 6, 79085 Freiburg, Germany

³ Laboratory of Sensors, Institute of Microsystems Engineering IMTEK, University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany

Materials 2017, 10(4), 400; https://doi.org/10.3390/ma10040400 - 11 Apr 2017

Cited by 26 | Viewed by 5650

Abstract

Chemically stable porous azacrown ether-crosslinked chitosan films were prepared by reacting varying molar amounts of N,N-diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6 (molar equivalents ranging from 0, 0.125, 0.167, 0.25 and 0.5) with chitosan. Their chemical and structural properties were characterized by solid state-nuclear magnetic resonance (NMR), elemental, Fourier [...] Read more.

Chemically stable porous azacrown ether-crosslinked chitosan films were prepared by reacting varying molar amounts of N,N-diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6 (molar equivalents ranging from 0, 0.125, 0.167, 0.25 and 0.5) with chitosan. Their chemical and structural properties were characterized by solid state-nuclear magnetic resonance (NMR), elemental, Fourier transform infrared (FTIR), microscopy, and X-ray analyses, as well as gel content. NMR and FTIR analyses of the reaction products suggested that new –CH₂– crosslink bridges were produced between the amine groups of chitosan (Ch) and the allyl groups of the azacrown (DAC). The crosslinking chemistry between allyl and amine groups of the reactants was further evidenced with solution NMR studies on model compound of glucosamine with the azacrown. X-ray diffraction analysis of the Ch/azacrown films using wide angle X-ray scattering (WAXS), including synchrotron-WAXS, revealed that the crystalline arrangement of chitosan (Ch) was partially destroyed with increasing grafting of azacrown ether proportion on the Ch polymer chain. Solubility and gel content determination confirmed network formation with a gel content as high as 84–95 wt %. Microstructural analysis revealed microporous morphology with high surface area. The morphology and structure of the azacrown ether-crosslinked chitosan films could be tailored by stoichiometry of the reacting species. Full article

(This article belongs to the Section Porous Materials)

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8 pages, 1710 KiB

Open AccessArticle

Small Strain Stiffness of Unsaturated Sands Containing a Polyacrylamide Solution

by Jongwon Jung¹

, Taeseo Ku² and Jaehun Ahn^3,*

¹ School of Civil Engineering, Chungbuk National University, Cheongju, Chungbuk 28644, Korea

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

³ Department of Civil and Environmental Engineering, Pusan National University, Busan 46241, Korea

Materials 2017, 10(4), 401; https://doi.org/10.3390/ma10040401 - 11 Apr 2017

Cited by 6 | Viewed by 4206

Abstract

Sand improvements using organic agents have shown promising results. Polyacrylamide is one possible organic agent, which has been shown to influence the shear strength, stiffness, soil remediation, and erosion resistance of geomaterials. In this study, we explored the shear wave velocity (S-wave) and [...] Read more.

Sand improvements using organic agents have shown promising results. Polyacrylamide is one possible organic agent, which has been shown to influence the shear strength, stiffness, soil remediation, and erosion resistance of geomaterials. In this study, we explored the shear wave velocity (S-wave) and water retention curves of unsaturated sands containing polyacrylamide solutions. The shear wave velocity was measured during the water retention curve measurement tests according to the variation of the degree of saturation. The experimental setup was verified through comparison of the measured water retention curves with the published data. The results show that (1) the S-wave velocity of saturated sands increases with polyacrylamide concentration; (2) as the degree of saturation decreases, the S-wave velocity increases; (3) near the residual water (or polyacrylamide solution) saturation, the S-wave velocity increases dramatically; (4) as the degree of saturation decreases, the S-wave velocity at unsaturated conditions increases with any given water (or polyacrylamide solution) saturation, like the water retention curves; (5) the S-wave velocity increases with the increase in capillary pressure; and (6) the predicted S-wave velocity at a given degree of saturation is slightly overestimated, and the modification of the equation is required. Full article

(This article belongs to the Section Porous Materials)

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13 pages, 14844 KiB

Open AccessArticle

Structural and Optical Properties of Ag Nanoparticles Synthesized by Thermal Treatment Method

by Leila Gharibshahi^1,*, Elias Saion^1,*, Elham Gharibshahi^1,2, Abdul Halim Shaari¹ and Khamirul Amin Matori¹

¹ Department of Physics, Faculty of Science, University of Putra Malaysia (UPM), Serdang 43400, Selangor, Malaysia

² Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA

Materials 2017, 10(4), 402; https://doi.org/10.3390/ma10040402 - 12 Apr 2017

Cited by 158 | Viewed by 8827

Abstract

The modified thermal treatment method via alternate oxygen and nitrogen flow was successfully employed to synthesize very narrow and pure Ag nanoparticles. The structural and optical properties of the obtained metal nanoparticles at different calcination temperatures between 400 and 800 °C were studied [...] Read more.

The modified thermal treatment method via alternate oxygen and nitrogen flow was successfully employed to synthesize very narrow and pure Ag nanoparticles. The structural and optical properties of the obtained metal nanoparticles at different calcination temperatures between 400 and 800 °C were studied using various techniques. The FTIR and EDX confirmed the formation of Ag nanoparticles without a trace of impurities. The XRD spectra revealed that the amorphous sample at 30 °C had transformed into the cubic crystalline nanostructures at the calcination temperature of 400 °C and higher. The TEM images showed the formation of spherical Ag nanoparticles in which the average particle size decreased with increasing calcination temperature from 7.88 nm at 400 °C to 3.29 nm at 800 °C. The optical properties were determined by UV-vis absorption spectrophotometer, which showed an increase in the conduction band of Ag nanoparticles with increasing calcination temperature from 2.75 eV at 400 °C to 3.04 eV at 800 °C. This was due to less attraction between conduction electrons and metal ions as the particle size decreases in corresponding to fewer numbers of atoms that made up the metal nanoparticles. Full article

(This article belongs to the Special Issue Noble Metal Nanoparticles)

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12 pages, 4436 KiB

Open AccessArticle

A Comparison of Microscale Techniques for Determining Fracture Toughness of LiMn₂O₄ Particles

by Muhammad Zeeshan Mughal^1,*

, Hugues-Yanis Amanieu^2,3, Riccardo Moscatelli¹

and Marco Sebastiani¹

¹ Engineering Department, University of Rome “ROMA TRE”, Via della Vasca Navale 79, 00146 Rome, Italy

² Institute for Materials Science and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Universitätsstr. 15, 45141 Essen, Germany

³ Robert Bosch GmbH, Robert-Bosch-Platz 1, 70839 Gerlingen-Schillerhoehe, Germany

Materials 2017, 10(4), 403; https://doi.org/10.3390/ma10040403 - 12 Apr 2017

Cited by 16 | Viewed by 4652

Abstract

Accurate estimation of fracture behavior of commercial LiMn₂O₄ particles is of great importance to predict the performance and lifetime of a battery. The present study compares two different microscale techniques to quantify the fracture toughness of LiMn₂O₄ [...] Read more.

Accurate estimation of fracture behavior of commercial LiMn₂O₄ particles is of great importance to predict the performance and lifetime of a battery. The present study compares two different microscale techniques to quantify the fracture toughness of LiMn₂O₄ particles embedded in an epoxy matrix. The first technique uses focused ion beam (FIB) milled micro pillars that are subsequently tested using the nanoindentation technique. The pillar geometry, critical load at pillar failure, and cohesive FEM simulations are then used to compute the fracture toughness. The second technique relies on the use of atomic force microscopy (AFM) to measure the crack opening displacement (COD) and subsequent application of Irwin’s near field theory to measure the mode-I crack tip toughness of the material. Results show pillar splitting method provides a fracture toughness value of ~0.24 MPa.m^1/2, while COD measurements give a crack tip toughness of ~0.81 MPa.m^1/2. The comparison of fracture toughness values with the estimated value on the reference LiMn₂O₄ wafer reveals that micro pillar technique provides measurements that are more reliable than the COD method. The difference is associated with ease of experimental setup, calculation simplicity, and little or no influence of external factors as associated with the COD measurements. Full article

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

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16 pages, 3785 KiB

Open AccessArticle

Investigation on Indentation Cracking-Based Approaches for Residual Stress Evaluation

by Felix Rickhey

, Karuppasamy Pandian Marimuthu and Hyungyil Lee^*

Department of Mechanical Engineering, Sogang University, Seoul 04107, Korea

Materials 2017, 10(4), 404; https://doi.org/10.3390/ma10040404 - 12 Apr 2017

Cited by 13 | Viewed by 5367

Abstract

Vickers indentation fracture can be used to estimate equibiaxial residual stresses (RS) in brittle materials. Previous, conceptually-equal, analytical models were established on the assumptions that (i) the crack be of a semi-circular shape and (ii) that the shape not be affected by RS. [...] Read more.

Vickers indentation fracture can be used to estimate equibiaxial residual stresses (RS) in brittle materials. Previous, conceptually-equal, analytical models were established on the assumptions that (i) the crack be of a semi-circular shape and (ii) that the shape not be affected by RS. A generalized analytical model that accounts for the crack shape and its change is presented. To assess these analytical models and to gain detailed insight into the crack evolution, an extended finite element (XFE) model is established. XFE analysis results show that the crack shape is generally not semi-circular and affected by RS and that tensile and compressive RS have different effects on the crack evolution. Parameter studies are performed to calibrate the generalized analytical model. Comparison of the results calculated by the analytical models with XFE results reveals the inaccuracy inherent in the previous analytical models, namely the neglect of (the change of) the crack aspect-ratio, in particular for tensile RS. Previous models should therefore be treated with caution and, if at all, used only for compressive RS. The generalized model, on the other hand, gives a more accurate description of the RS, but requires the crack depth. Full article

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

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12 pages, 3177 KiB

Open AccessArticle

Study on Protection Mechanism of 30CrMnMo-UHMWPE Composite Armor

by Yu Zhou^1,2, Guoju Li^1,2, Qunbo Fan^1,2,*, Yangwei Wang^1,2, Haiyang Zheng³, Lin Tan³ and Xuan Xu³

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

² National Key Laboratory of Science and Technology on Materials under Shock and Impact, Beijing 100081, China

³ Beijing Winyarn High Performance Fiber Company Limited, Beijing 101407, China

Materials 2017, 10(4), 405; https://doi.org/10.3390/ma10040405 - 12 Apr 2017

Cited by 19 | Viewed by 5144

Abstract

The penetration of a 30CrMnMo ultra-high molecular weight polyethylene armor by a high-speed fragment was investigated via experiments and simulations. Analysis of the projectile revealed that the nose (of the projectile) is in the non-equilibrium state at the initial stage of penetration, and [...] Read more.

The penetration of a 30CrMnMo ultra-high molecular weight polyethylene armor by a high-speed fragment was investigated via experiments and simulations. Analysis of the projectile revealed that the nose (of the projectile) is in the non-equilibrium state at the initial stage of penetration, and the low-speed regions undergo plastic deformation. Subsequently, the nose-tail velocities of the projectile were virtually identical and fluctuated together. In addition, the effective combination of the steel plate and polyethylene (PE) laminate resulted in energy absorption by the PE just before the projectile nose impacts the laminate. This early absorption plays a positive role in the ballistic performance of the composite armor. Further analysis of the internal energy and mass loss revealed that the PE laminate absorbs energy via the continuous and stable failure of PE fibers during the initial stages of penetration, and absorbs energy via deformation until complete penetration occurs. The energy absorbed by the laminate accounts for 68% of the total energy absorption, indicating that the laminate plays a major role in energy absorption during the penetration process. Full article

(This article belongs to the Special Issue Theory, Experiment and Modelling of the Dynamic Response of Materials)

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17 pages, 5589 KiB

Open AccessArticle

Investigation of a Coupled Arrhenius-Type/Rossard Equation of AH36 Material

by Qin Qin^1,*

, Ming-Liang Tian¹

and Peng Zhang²

¹ School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China

² The Tenth System Design Department of the Tenth Research Academy, Guiyang 550009, China

Materials 2017, 10(4), 407; https://doi.org/10.3390/ma10040407 - 13 Apr 2017

Cited by 6 | Viewed by 4032

Abstract

High-temperature tensile testing of AH36 material in a wide range of temperatures (1173–1573 K) and strain rates (10⁻⁴–10⁻² s⁻¹) has been obtained by using a Gleeble system. These experimental stress-strain data have been adopted to develop the constitutive [...] Read more.

High-temperature tensile testing of AH36 material in a wide range of temperatures (1173–1573 K) and strain rates (10⁻⁴–10⁻² s⁻¹) has been obtained by using a Gleeble system. These experimental stress-strain data have been adopted to develop the constitutive equation. The constitutive equation of AH36 material was suggested based on the modified Arrhenius-type equation and the modified Rossard equation respectively. The results indicate that the constitutive equation is strongly influenced by temperature and strain, especially strain. Moreover, there is a good agreement between the predicted data of the modified Arrhenius-type equation and the experimental results when the strain is greater than 0.02. There is also good agreement between the predicted data of the Rossard equation and the experimental results when the strain is less than 0.02. Therefore, a coupled equation where the modified Arrhenius-type equation and Rossard equation are combined has been proposed to describe the constitutive equation of AH36 material according to the different strain values in order to improve the accuracy. The correlation coefficient between the computed and experimental flow stress data was 0.998. The minimum value of the average absolute relative error shows the high accuracy of the coupled equation compared with the two modified equations. Full article

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11 pages, 8807 KiB

Open AccessArticle

Fracture Analysis of MWCNT/Epoxy Nanocomposite Film Deposited on Aluminum Substrate

by Shiuh-Chuan Her^* and Pao-Chu Chien

Department of Mechanical Engineering, Yuan Ze University, Chung-Li 320, Taiwan

Materials 2017, 10(4), 408; https://doi.org/10.3390/ma10040408 - 13 Apr 2017

Cited by 10 | Viewed by 4233

Abstract

Multi-walled carbon nanotube (MWCNT) reinforced epoxy films were deposited on an aluminum substrate by a hot-pressing process. Three-point bending tests were performed to determine the Young’s modulus of MWCNT reinforced nanocomposite films. Compared to the neat epoxy film, nanocomposite film with 1 wt [...] Read more.

Multi-walled carbon nanotube (MWCNT) reinforced epoxy films were deposited on an aluminum substrate by a hot-pressing process. Three-point bending tests were performed to determine the Young’s modulus of MWCNT reinforced nanocomposite films. Compared to the neat epoxy film, nanocomposite film with 1 wt % of MWCNT exhibits an increase of 21% in the Young’s modulus. Four-point-bending tests were conducted to investigate the fracture toughness of the MWCNT/epoxy nanocomposite film deposited on an aluminum substrate with interfacial cracks. Based on the Euler-Bernoulli beam theory, the strain energy in a film/substrate composite beam is derived. The difference of strain energy before and after the propagation of the interfacial crack are calculated, leading to the determination of the strain energy release rate. Experimental test results show that the fracture toughness of the nanocomposite film deposited on the aluminum substrate increases with the increase in the MWCNT content. Full article

(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)

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11 pages, 4145 KiB

Open AccessArticle

Tortuosity of Aligned Channels in Alumina Membranes Produced by Vacuum-Induced Surface Directional Freezing

by Sandra Großberger¹

, Tobias Fey²

and Geoffrey Lee^1,*

¹ Division of Pharmaceutics, University of Erlangen, 91054 Erlangen, Germany

² Department of Material Science and Engineering, University of Erlangen, 91054 Erlangen, Germany

Materials 2017, 10(4), 409; https://doi.org/10.3390/ma10040409 - 14 Apr 2017

Cited by 4 | Viewed by 4185

Abstract

Vacuum-induced surface freezing of colloidal alumina was used to produce membranes that have elongated, aligned channels and, hence, are tortuous in the direction perpendicular to ice crystal growth. The effective tortuosity of the membranes was measured by steady-state diffusion of a solute, methylene [...] Read more.

Vacuum-induced surface freezing of colloidal alumina was used to produce membranes that have elongated, aligned channels and, hence, are tortuous in the direction perpendicular to ice crystal growth. The effective tortuosity of the membranes was measured by steady-state diffusion of a solute, methylene blue. The resulting diffusion profiles show an initial step-increase in amount of dye reaching the acceptor that is caused by capillarity drawing the donor solution through any non-wetted channels in the membrane. This is followed by a linear steady-state phase whose flux is proportional to dye concentration in the donor and inversely proportional to the colloid’s volume fraction of dispersed phase. From the steady-state flux, the effective tortuosity, τ* = (α/τ)⁻¹, was calculated. This is the reciprocal quotient of the reduced available area for diffusion within the membrane,

α

= A*/A, where A* is the available area and A is the cross-sectional area of the membrane, and the increased mean diffusional path length, i.e., tortuosity

= L^{*} / L

, where L* is the mean path length and L is the membrane thickness. The values of τ* lie in the range of 2–38 and increase as the volume fraction of dispersed phase is larger. This latter effect indicates that τ* > 1 results, to a larger extent, from the reduced available diffusion area, α, than from the lengthened pathway, τ, in these aligned porous membranes. Full article

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11 pages, 2325 KiB

Open AccessFeature PaperArticle

Fundamentals of Thermal Expansion and Thermal Contraction

by Zi-Kui Liu^*

, Shun-Li Shang and Yi Wang

Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA

Materials 2017, 10(4), 410; https://doi.org/10.3390/ma10040410 - 14 Apr 2017

Cited by 31 | Viewed by 9022

Abstract

Thermal expansion is an important property of substances. Its theoretical prediction has been challenging, particularly in cases the volume decreases with temperature, i.e., thermal contraction or negative thermal expansion at high temperatures. In this paper, a new theory recently developed by the authors [...] Read more.

Thermal expansion is an important property of substances. Its theoretical prediction has been challenging, particularly in cases the volume decreases with temperature, i.e., thermal contraction or negative thermal expansion at high temperatures. In this paper, a new theory recently developed by the authors has been reviewed and further examined in the framework of fundamental thermodynamics and statistical mechanics. Its applications to cerium with colossal thermal expansion and Fe₃Pt with thermal contraction in certain temperature ranges are discussed. It is anticipated that this theory is not limited to volume only and can be used to predict a wide range of properties at finite temperatures. Full article

(This article belongs to the Special Issue Negative Thermal Expansion Materials)

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14 pages, 4705 KiB

Open AccessArticle

Preparation and Characterization of Thermoresponsive Poly(N-isopropylacrylamide-co-acrylic acid)-Grafted Hollow Fe₃O₄/SiO₂ Microspheres with Surface Holes for BSA Release

by Jing Zhao¹, Ming Zeng¹, Kaiqiang Zheng¹, Xinhua He¹, Minqiang Xie²

and Xiaoyi Fu^1,*

¹ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, China

² Department of Otorhinolaryngology Head & Neck Surgery, Zhujiang Hospital of Southern Medical University, Guangzhou 510282, China

Materials 2017, 10(4), 411; https://doi.org/10.3390/ma10040411 - 14 Apr 2017

Cited by 4 | Viewed by 5714

Abstract

Thermoresponsive P(NIPAM-AA)/Fe₃O₄/SiO₂ microspheres with surface holes serving as carriers were prepared using p-Fe₃O₄/SiO₂ microspheres with a thermoresponsive copolymer. The p-Fe₃O₄/SiO₂ microspheres was obtained using a modified Pickering method [...] Read more.

Thermoresponsive P(NIPAM-AA)/Fe₃O₄/SiO₂ microspheres with surface holes serving as carriers were prepared using p-Fe₃O₄/SiO₂ microspheres with a thermoresponsive copolymer. The p-Fe₃O₄/SiO₂ microspheres was obtained using a modified Pickering method and chemical etching. The surface pore size of p-Fe₃O₄/SiO₂ microspheres was in the range of 18.3 nm~37.2 nm and the cavity size was approximately 60 nm, which are suitable for loading and transporting biological macromolecules. P(NIPAM-AA) was synthesized inside and outside of the p-Fe₃O₄/SiO₂ microspheres via atom transfer radical polymerization of NIPAM, MBA and AA. The volume phase transition temperature (VPTT) of the specifically designed P(NIPAM-AA)/Fe₃O₄/SiO₂ microspheres was 42.5 °C. The saturation magnetization of P(NIPAM-AA)/Fe₃O₄/SiO₂ microspheres was 72.7 emu/g. The P(NIPAM-AA)/Fe₃O₄/SiO₂ microspheres were used as carriers to study the loading and release behavior of BSA. This microsphere system shows potential for the loading of proteins as a drug delivery platform. Full article

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14 pages, 14819 KiB

Open AccessArticle

The Passive Film Growth Mechanism of New Corrosion-Resistant Steel Rebar in Simulated Concrete Pore Solution: Nanometer Structure and Electrochemical Study

by Jin-yang Jiang^1,2,*

, Danqian Wang^1,2, Hong-yan Chu^1,2, Han Ma³, Yao Liu^1,2, Yun Gao^1,2, Jinjie Shi^1,2 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(4), 412; https://doi.org/10.3390/ma10040412 - 14 Apr 2017

Cited by 49 | Viewed by 6946

Abstract

An elaborative study was carried out on the growth mechanism and properties of the passive film for a new kind of alloyed corrosion-resistant steel (CR steel). The passive film naturally formed in simulated concrete pore solutions (pH = 13.3). The corrosion resistance was [...] Read more.

An elaborative study was carried out on the growth mechanism and properties of the passive film for a new kind of alloyed corrosion-resistant steel (CR steel). The passive film naturally formed in simulated concrete pore solutions (pH = 13.3). The corrosion resistance was evaluated by various methods including open circuit potential (OCP), linear polarization resistance (LPR) measurements, and electrochemical impedance spectroscopy (EIS). Meanwhile, the 2205 duplex stainless steel (SS steel) was evaluated for comparison. Moreover, the passive film with CR steel was studied by means of X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Atomic Force Microscope (AFM), and the Mott‑Schottky approach. The results showed that the excellent passivity of CR steel could be detected in a high alkaline environment. The grain boundaries between the fine passive film particles lead to increasing Cr oxide content in the later passivation stage. The filling of cation vacancies in the later passivation stage as well as the orderly crystalized inner layer contributed to the excellent corrosion resistance of CR steel. A passive film growth model for CR steel was proposed. Full article

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11 pages, 8133 KiB

Open AccessArticle

A High Performance Lithium-Ion Capacitor with Both Electrodes Prepared from Sri Lanka Graphite Ore

by Xiaoyu Gao, Changzhen Zhan, Xiaoliang Yu, Qinghua Liang, Ruitao Lv, Guosheng Gai, Wanci Shen, Feiyu Kang and Zheng-Hong Huang^*

State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

Materials 2017, 10(4), 414; https://doi.org/10.3390/ma10040414 - 14 Apr 2017

Cited by 26 | Viewed by 6884

Abstract

The natural Sri Lanka graphite (vein graphite) is widely-used as anode material for lithium-ion batteries (LIBs), due to its high crystallinity and low cost. In this work, graphitic porous carbon (GPC) and high-purity vein graphite (PVG) were prepared from Sri Lanka graphite ore [...] Read more.

The natural Sri Lanka graphite (vein graphite) is widely-used as anode material for lithium-ion batteries (LIBs), due to its high crystallinity and low cost. In this work, graphitic porous carbon (GPC) and high-purity vein graphite (PVG) were prepared from Sri Lanka graphite ore by KOH activation, and high temperature purification, respectively. Furthermore, a lithium-ion capacitor (LIC) is fabricated with GPC as cathode, and PVG as anode. The assembled GPC//PVG LIC shows a notable electrochemical performance with a maximum energy density of 86 W·h·kg⁻¹ at 150 W·kg⁻¹, and 48 W·h·kg⁻¹ at a high-power density of 7.4 kW·kg⁻¹. This high-performance LIC based on PVG and GPC is believed to be promising for practical applications, due to its low-cost raw materials and industrially feasible production. Full article

(This article belongs to the Special Issue Materials for Electrochemical Capacitors and Batteries)

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8 pages, 3544 KiB

Open AccessArticle

Grain Boundary Character Dependence on Nucleation of Discontinuous Precipitates in Cu-Ti Alloys

by Satoshi Semboshi^1,2,*, Mitsutaka Sato¹, Yasuyuki Kaneno², Akihiro Iwase² and Takayuki Takasugi²

¹ Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan

² Department of Materials Science, Osaka Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai 599-8531, Japan

Materials 2017, 10(4), 415; https://doi.org/10.3390/ma10040415 - 15 Apr 2017

Cited by 34 | Viewed by 6200

Abstract

The dependence of the grain boundary character distribution for a Cu-4 at. % Ti polycrystal alloy (average grain size: 100 µm) on the nucleation of cellular discontinuous precipitates was systematically investigated. In an alloy over-aged at 723 K, cellular discontinuous precipitates consisted of [...] Read more.

The dependence of the grain boundary character distribution for a Cu-4 at. % Ti polycrystal alloy (average grain size: 100 µm) on the nucleation of cellular discontinuous precipitates was systematically investigated. In an alloy over-aged at 723 K, cellular discontinuous precipitates consisted of a terminal Cu solid solution and a stable β-Cu₄Ti lamellae nucleated at grain boundaries. Electron backscatter diffraction analysis revealed that the discontinuous precipitation reaction preferentially occurred at random grain boundaries with a Σ value of more than 21 according to the coincidence site lattice theory. On the other hand, few cellular discontinuous precipitates nucleated at low-angle and low-Σ boundaries, particularly twin (Σ 3) boundaries. These findings suggest that the nucleation of discontinuous precipitates is closely correlated with grain boundary character and structure, and hence energy and/or diffusibility. It should therefore be possible to suppress the discontinuous precipitation reaction through control of the alloy’s grain boundary energy, by means of texture control and third elemental addition. Full article

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16 pages, 4392 KiB

Open AccessArticle

The Utilization of Multiple-Walled Carbon Nanotubes in Polymer Modified Bitumen

by Benan Shu

, Shaopeng Wu, Ling Pang^* and Barugahare Javilla

State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China

Materials 2017, 10(4), 416; https://doi.org/10.3390/ma10040416 - 15 Apr 2017

Cited by 62 | Viewed by 5656

Abstract

SBS (styrene-butadiene-styrene block copolymer) modified bitumen is one of most widely used polymer modified bitumens in China. It is also not satisfactory when subjected to extreme conditions. Multiple-walled carbon nanotubes, as a type of advanced nanomaterial, are investigated extensively because of their strong [...] Read more.

SBS (styrene-butadiene-styrene block copolymer) modified bitumen is one of most widely used polymer modified bitumens in China. It is also not satisfactory when subjected to extreme conditions. Multiple-walled carbon nanotubes, as a type of advanced nanomaterial, are investigated extensively because of their strong adsorption capacity. Little research has been done about MWCNTs/SBS modified bitumen, and in view of this, the performance and modification mechanism of MWCNTs/SBS modified bitumen was investigated in this paper. Conventional bitumen tests, Brookfield viscosity, bending beam rheometer, and dynamic shear rheometer tests showed improved performance at high and low temperature. The optimum MWCNTs content was determined as 1.0%. FT-IR, bitumen four components, and thermal analysis tests were conducted and revealed that the addition of MWCNTs led to a decrease in the content of light components. In addition, the rate of decomposition and volatilization of saturates and aromatics was reduced and better thermal stability of bitumen was found. Fluorescence microscopy tests showed that MWCNTs improved the dispersion of SBS and storage stability of the binder. Finally a schematic was proposed to explain how MWCNTs improved the performance of SBS modified bitumen through their strong adsorption property created by π–π intermolecular forces. Full article

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13 pages, 1901 KiB

Open AccessArticle

Optimization of Anodic Porous Alumina Fabricated from Commercial Aluminum Food Foils: A Statistical Approach

by Eva Riccomagno¹

, Amirreza Shayganpour² and Marco Salerno^2,*

¹ Department of Mathematics, University of Genova, via Dodecaneso 35, I-16146 Genova, Italy

² Department of Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova, Italy

Materials 2017, 10(4), 417; https://doi.org/10.3390/ma10040417 - 15 Apr 2017

Cited by 5 | Viewed by 3660

Abstract

Anodic porous alumina is a known material based on an old industry, yet with emerging applications in nanoscience and nanotechnology. This is promising, but the nanostructured alumina should be fabricated from inexpensive raw material. We fabricated porous alumina from commercial aluminum food plate [...] Read more.

Anodic porous alumina is a known material based on an old industry, yet with emerging applications in nanoscience and nanotechnology. This is promising, but the nanostructured alumina should be fabricated from inexpensive raw material. We fabricated porous alumina from commercial aluminum food plate in 0.4 M aqueous phosphoric acid, aiming to design an effective manufacturing protocol for the material used as nanoporous filler in dental restorative composites, an application demonstrated previously by our group. We identified the critical input parameters of anodization voltage, bath temperature and anodization time, and the main output parameters of pore diameter, pore spacing and oxide thickness. Scanning electron microscopy and grain analysis allowed us to assess the nanostructured material, and the statistical design of experiments was used to optimize its fabrication. We analyzed a preliminary dataset, designed a second dataset aimed at clarifying the correlations between input and output parameters, and ran a confirmation dataset. Anodization conditions close to 125 V, 20°C, and 7 h were identified as the best for obtaining, in the shortest possible time, pore diameters and spacing of 100–150 nm and 150–275 nm respectively, and thickness of 6–8 µm, which are desirable for the selected application according to previously published results. Our analysis confirmed the linear dependence of pore size on anodization voltage and of thickness on anodization time. The importance of proper control on the experiment was highlighted, since batch effects emerge when the experimental conditions are not exactly reproduced. Full article

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18 pages, 6943 KiB

Open AccessArticle

Self-Developed Testing System for Determining the Temperature Behavior of Concrete

by He Zhu, Qingbin Li

and Yu Hu^*

Department of Hydraulic engineering, Tsinghua University, Beijing 100084, China

Materials 2017, 10(4), 419; https://doi.org/10.3390/ma10040419 - 16 Apr 2017

Cited by 16 | Viewed by 4660

Abstract

Cracking due to temperature and restraint in mass concrete is an important issue. A temperature stress testing machine (TSTM) is an effective test method to study the mechanism of temperature cracking. A synchronous closed loop federated control TSTM system has been developed by [...] Read more.

Cracking due to temperature and restraint in mass concrete is an important issue. A temperature stress testing machine (TSTM) is an effective test method to study the mechanism of temperature cracking. A synchronous closed loop federated control TSTM system has been developed by adopting the design concepts of a closed loop federated control, a detachable mold design, a direct measuring deformation method, and a temperature deformation compensation method. The results show that the self-developed system has the comprehensive ability of simulating different restraint degrees, multiple temperature and humidity modes, and closed-loop control of multi-TSTMs during one test period. Additionally, the direct measuring deformation method can obtain a more accurate deformation and restraint degree result with little local damage. The external temperature deformation affecting the concrete specimen can be eliminated by adopting the temperature deformation compensation method with different considerations of steel materials. The concrete quality of different TSTMs can be guaranteed by being vibrated on the vibrating stand synchronously. The detachable mold design and assembled method has greatly overcome the difficulty of eccentric force and deformation. Full article

(This article belongs to the Special Issue Thermal Sciences and Thermodynamics of Materials)

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9 pages, 3732 KiB

Open AccessArticle

Simulation of the Continuous Casting and Cooling Behavior of Metallic Glasses

by Zhipu Pei¹ and Dongying Ju^2,3,*

¹ Graduate School of Saitama Institute of Technology, Fusaiji 1690, Fukaya 369-0293, Japan

² High-Tech Research Center, Saitama Institute of Technology, Fusaiji 1690, Fukaya 369-0293, Japan

³ University of Science and Technology Liaoning, Anshan 114051, China

Materials 2017, 10(4), 420; https://doi.org/10.3390/ma10040420 - 17 Apr 2017

Cited by 5 | Viewed by 4903

Abstract

The development of melt spinning technique for preparation of metallic glasses was summarized. The limitations as well as restrictions of the melt spinning embodiments were also analyzed. As an improvement and variation of the melt spinning method, the vertical-type twin-roll casting (VTRC) process [...] Read more.

The development of melt spinning technique for preparation of metallic glasses was summarized. The limitations as well as restrictions of the melt spinning embodiments were also analyzed. As an improvement and variation of the melt spinning method, the vertical-type twin-roll casting (VTRC) process was discussed. As the thermal history experienced by the casting metals to a great extent determines the qualities of final products, cooling rate in the quenching process is believed to have a significant effect on glass formation. In order to estimate the ability to produce metallic glasses by VTRC method, temperature and flow phenomena of the melt in molten pool were computed, and cooling rates under different casting conditions were calculated with the simulation results. Considering the fluid character during casting process, the material derivative method based on continuum theory was adopted in the cooling rate calculation. Results show that the VTRC process has a good ability in continuous casting metallic glassy ribbons. Full article

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13 pages, 5946 KiB

Open AccessArticle

Comparative Efficacies of Collagen-Based 3D Printed PCL/PLGA/β-TCP Composite Block Bone Grafts and Biphasic Calcium Phosphate Bone Substitute for Bone Regeneration

by Kyoung-Sub Hwang^1,†, Jae-Won Choi^1,†

, Jae-Hun Kim^2,†, Ho Yun Chung³

, Songwan Jin⁴, Jin-Hyung Shim⁴, Won-Soo Yun⁴, Chang-Mo Jeong¹ and Jung-Bo Huh^1,*

¹ Department of Prosthodontics, Dental Research Institute, Institute of Translational Dental Sciences, BK21 PLUS Project, School of Dentistry, Pusan National University, Yangsan 50612, Korea

² Department of Mechanical System Engineering, Graduate School of Knowledge-Based Technology and Energy, Korea Polytechnic University, 237 Sangidaehak-Ro, Siheung-Si, Gyeonggi-Do 15073, Korea

³ Department of Plastic and Reconstructive Surgery, Kyungpook National University, School of Medicine, 130 Dongdeok-ro, Jung-gu, Daegu 41944, Korea

⁴ Department of Mechanical Engineering, Korea Polytechnic University, 237 Sangidaehak-Ro, Siheung-Si, Gyeonggi-Do 15073, Korea

^† These authors contributed equally to this work.

Materials 2017, 10(4), 421; https://doi.org/10.3390/ma10040421 - 17 Apr 2017

Cited by 60 | Viewed by 8070

Abstract

The purpose of this study was to compare bone regeneration and space maintaining ability of three-dimensional (3D) printed bone grafts with conventional biphasic calcium phosphate (BCP). After mixing polycaprolactone (PCL), poly (lactic-co-glycolic acid) (PLGA), and β-tricalcium phosphate (β-TCP) in a 4:4:2 ratio, PCL/PLGA/β-TCP [...] Read more.

The purpose of this study was to compare bone regeneration and space maintaining ability of three-dimensional (3D) printed bone grafts with conventional biphasic calcium phosphate (BCP). After mixing polycaprolactone (PCL), poly (lactic-co-glycolic acid) (PLGA), and β-tricalcium phosphate (β-TCP) in a 4:4:2 ratio, PCL/PLGA/β-TCP particulate bone grafts were fabricated using 3D printing technology. Fabricated particulate bone grafts were mixed with atelocollagen to produce collagen-based PCL/PLGA/β-TCP composite block bone grafts. After formation of calvarial defects 8 mm in diameter, PCL/PLGA/β-TCP composite block bone grafts and BCP were implanted into bone defects of 32 rats. Although PCL/PLGA/β-TCP composite block bone grafts were not superior in bone regeneration ability compared to BCP, the results showed relatively similar performance. Furthermore, PCL/PLGA/β-TCP composite block bone grafts showed better ability to maintain bone defects and to support barrier membranes than BCP. Therefore, within the limitations of this study, PCL/PLGA/β-TCP composite block bone grafts could be considered as an alternative to synthetic bone grafts available for clinical use. Full article

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27 pages, 4061 KiB

Open AccessFeature PaperArticle

Prediction of First-Year Corrosion Losses of Carbon Steel and Zinc in Continental Regions

by Yulia M. Panchenko^* and Andrey I. Marshakov

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow 119071, Russia

Materials 2017, 10(4), 422; https://doi.org/10.3390/ma10040422 - 18 Apr 2017

Cited by 32 | Viewed by 5588

Abstract

Dose-response functions (DRFs) developed for the prediction of first-year corrosion losses of carbon steel and zinc (K₁) in continental regions are presented. The dependences of mass losses on SO₂ concentration, K = f([SO₂]), obtained from experimental [...] Read more.

Dose-response functions (DRFs) developed for the prediction of first-year corrosion losses of carbon steel and zinc (K₁) in continental regions are presented. The dependences of mass losses on SO₂ concentration, K = f([SO₂]), obtained from experimental data, as well as nonlinear dependences of mass losses on meteorological parameters, were taken into account in the development of the DRFs. The development of the DRFs was based on the experimental data from one year of testing under a number of international programs: ISO CORRAG, MICAT, two UN/ECE programs, the Russian program in the Far-Eastern region, and data published in papers. The paper describes predictions of K₁ values of these metals using four different models for continental test sites under UN/ECE, RF programs and within the MICAT project. The predictions of K₁ are compared with experimental K₁ values, and the models presented here are analyzed in terms of the coefficients used in the models. Full article

(This article belongs to the Special Issue Fundamental and Research Frontier of Atmospheric Corrosion)

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14 pages, 8887 KiB

Open AccessArticle

Analysis of Deep Drawing Process for Stainless Steel Micro-Channel Array

by Tsung-Chia Chen, Jiang-Cheng Lin and Rong-Mao Lee^*

Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung City 411, Taiwan

Materials 2017, 10(4), 423; https://doi.org/10.3390/ma10040423 - 18 Apr 2017

Cited by 3 | Viewed by 7325

Abstract

The stainless steel bipolar plate has received much attention due to the cost of graphite bipolar plates. Since the micro-channel of bipolar plates plays the role of fuel flow field, electric connector and fuel sealing, an investigation of the deep drawing process for [...] Read more.

The stainless steel bipolar plate has received much attention due to the cost of graphite bipolar plates. Since the micro-channel of bipolar plates plays the role of fuel flow field, electric connector and fuel sealing, an investigation of the deep drawing process for stainless steel micro-channel arrays is reported in this work. The updated Lagrangian formulation, degenerated shell finite element analysis, and the r-minimum rule have been employed to study the relationship between punch load and stroke, distributions of stress and strain, thickness variations and depth variations of individual micro-channel sections. A micro-channel array is practically formed, with a width and depth of a single micro-channel of 0.75 mm and 0.5 mm, respectively. Fractures were usually observed in the fillet corner of the micro-channel bottom. According to the experimental results, more attention should be devoted to the fillet dimension design of punch and die. A larger die fillet can lead to better formability and a reduction of the punch load. In addition, the micro-channel thickness and the fillet radius have to be taken into consideration at the same time. Finally, the punch load estimated by the unmodified metal forming equation is higher than that of experiments. Full article

(This article belongs to the Special Issue Selected Material Related Papers from ICI2016)

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14 pages, 7622 KiB

Open AccessArticle

Room-Temperature and High-Temperature Tensile Mechanical Properties of TA15 Titanium Alloy and TiB Whisker-Reinforced TA15 Matrix Composites Fabricated by Vacuum Hot-Pressing Sintering

by Yangju Feng

, Wencong Zhang^*, Li Zeng, Guorong Cui and Wenzhen Chen^*

School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209, China

Materials 2017, 10(4), 424; https://doi.org/10.3390/ma10040424 - 18 Apr 2017

Cited by 36 | Viewed by 5906

Abstract

In this paper, the microstructure, the room-temperature and high-temperature tensile mechanical properties of monolithic TA15 alloy and TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15) fabricated by vacuum hot-pressing sintering were investigated. The microstructure results showed that there were no obvious differences in the [...] Read more.

In this paper, the microstructure, the room-temperature and high-temperature tensile mechanical properties of monolithic TA15 alloy and TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15) fabricated by vacuum hot-pressing sintering were investigated. The microstructure results showed that there were no obvious differences in the microstructure between monolithic TA15 alloy and TiBw/TA15 composites, except whether or not the grain boundaries contained TiBw. After sintering, the matrix microstructure presented a typical Widmanstätten structure and the size of primary β grain was consistent with the size of spherical TA15 titanium metallic powders. This result demonstrated that TiBw was not the only factor limiting grain coarsening of the primary β grain. Moreover, the grain coarsening of α colonies was obvious, and high-angle grain boundaries (HAGBs) were distributed within the primary β grain. In addition, TiBw played an important role in the microstructure evolution. In the composites, TiBw were randomly distributed in the matrix and surrounded by a large number of low-angle grain boundaries (LAGBs). Globularization of α phase occurred prior, near the TiBw region, because TiBw provided the nucleation site for the equiaxed α phase. The room-temperature and high-temperature tensile results showed that TiBw distributed at the primary β grain boundaries can strengthen the grain boundary, but reduce the connectivity of the matrix. Therefore, compared to the monolithic TA15 alloy fabricated by the same process, the tensile strength of the composites increased, and the tensile elongation decreased. Moreover, with the addition of TiBw, the fracture mechanism was changed to a mixture of brittle fracture and ductile failure (composites) from ductile failure (monolithic TA15 alloy). The fracture surfaces of TiBw/TA15 composites were the grain boundaries of the primary β grain where the majority of TiB whiskers distributed, i.e., the surfaces of the spherical TA15 titanium metallic powders. Full article

(This article belongs to the Section Advanced Materials Characterization)

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19 pages, 11062 KiB

Open AccessFeature PaperArticle

The In Vitro Bioactivity, Degradation, and Cytotoxicity of Polymer-Derived Wollastonite-Diopside Glass-Ceramics

by Amanda De Castro Juraski¹, Andrea Cecilia Dorion Rodas¹, Hamada Elsayed^2,3

, Enrico Bernardo^2,*

, Viviane Oliveira Soares⁴ and Juliana Daguano^1,*

¹ Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Federal University of ABC, Santo André 09210-580, Brazil

² Dipartimento di Ingegneria Industriale, University of Padova, Padova 35131, Italy

³ Ceramics Department, National Research Centre, El-Bohous Street, 12622 Cairo, Egypt

⁴ Departamento de Ciências, State University of Maringá, Maringá 87360-000, Brazil

Materials 2017, 10(4), 425; https://doi.org/10.3390/ma10040425 - 18 Apr 2017

Cited by 23 | Viewed by 7733

Abstract

Ca-Mg silicates are receiving a growing interest in the field of bioceramics. In a previous study, wollastonite-diopside (WD) glass-ceramics were successfully prepared by a new processing route, consisting of the heat treatment of a silicone resin embedding reactive oxide particles and a Ca/Mg-rich [...] Read more.

Ca-Mg silicates are receiving a growing interest in the field of bioceramics. In a previous study, wollastonite-diopside (WD) glass-ceramics were successfully prepared by a new processing route, consisting of the heat treatment of a silicone resin embedding reactive oxide particles and a Ca/Mg-rich glass. The in vitro degradation, bioactivity, and cell response of these new WD glass-ceramics, fired at 900–1100 °C for 1 h, as a function of the Ca/Mg-rich glass content, are the aim of this investigation The results showed that WD glass-ceramics from formulations comprising different glass contents (70–100% at 900 °C, 30% at 1100 °C) exhibit the formation of an apatite-like layer on their surface after immersion in SBF for seven days, thus confirming their surface bioactivity. The XRD results showed that these samples crystallized, mainly forming wollastonite (CaSiO₃) and diopside (CaMgSi₂O₆), but combeite (Na₂Ca₂Si₃O₉) crystalline phase was also detected. Besides in vitro bioactivity, cytotoxicity and osteoblast adhesion and proliferation tests were applied after all characterizations, and the formulation comprising 70% glass was demonstrated to be promising for further in vivo studies. Full article

(This article belongs to the Special Issue Bioceramics 2016)

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17 pages, 17255 KiB

Open AccessArticle

In Situ Formation of Decavanadate-Intercalated Layered Double Hydroxide Films on AA2024 and their Anti-Corrosive Properties when Combined with Hybrid Sol Gel Films

by Junsheng Wu¹, Dongdong Peng^1,2,*, Yuntao He³, Xiaoqiong Du¹, Zhan Zhang¹, Bowei Zhang², Xiaogang Li¹ and Yizhong Huang^2,*

¹ Institute of Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China

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

³ National Science &Technology Infrastructure Center, Beijing 100862, China

Materials 2017, 10(4), 426; https://doi.org/10.3390/ma10040426 - 18 Apr 2017

Cited by 26 | Viewed by 5474

Abstract

A layered double hydroxide (LDH) film was formed in situ on aluminum alloy 2024 through a urea hydrolysis method, and a decavanadate-intercalated LDH (LDH-V) film fabricated through the dip coating method. The microstructural and morphological characteristics were investigated by scanning electron microscopy (SEM). [...] Read more.

A layered double hydroxide (LDH) film was formed in situ on aluminum alloy 2024 through a urea hydrolysis method, and a decavanadate-intercalated LDH (LDH-V) film fabricated through the dip coating method. The microstructural and morphological characteristics were investigated by scanning electron microscopy (SEM). The corrosion-resistant performance was analyzed by electrochemical impedance spectroscopy (EIS), scanning electrochemical microscopy (SECM), and a salt-spray test (SST).The SEM results showed that a complete and defect-free surface was formed on the LDH-VS film. The anticorrosion results revealed that the LDH-VS film had better corrosion-resistant properties than the LDH-S film, especially long-term corrosion resistance. The mechanism of corrosion protection was proposed to consist of the self-healing effect of the decavanadate intercalation and the shielding effect of the sol-gel film. Full article

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7 pages, 3292 KiB

Open AccessArticle

Effects of Pr₆O₁₁ Addition on the Acid Resistance of Ceramic Proppant

by Guodong Xiong, Bolin Wu^* and Tingting Wu

College of Material Science and Engineering, Guilin University of Technology, Guilin 541004, Guangxi, China

Materials 2017, 10(4), 427; https://doi.org/10.3390/ma10040427 - 19 Apr 2017

Cited by 5 | Viewed by 3872

Abstract

This paper investigated the effect of Pr₆O₁₁ addition on the acid resistance of ceramic proppant. Acid resistance of proppants can be improved by introducing Pr₆O₁₁ into the Al₂O₃-CaO-MgO-SiO₂ (ACMS) system. To illustrate [...] Read more.

This paper investigated the effect of Pr₆O₁₁ addition on the acid resistance of ceramic proppant. Acid resistance of proppants can be improved by introducing Pr₆O₁₁ into the Al₂O₃-CaO-MgO-SiO₂ (ACMS) system. To illustrate and explain the mechanism of acid resistance, the samples were characterized by different techniques, using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The phase structure of the specimens was characterized by XRD and SEM-detected microstructures of the specimens. It was observed that with the increase of rare-earth oxide content, the acid solubility of the specimens decreased, and then increased when it reached the minimum value 0.45 wt %. The results of the research show that the improvement of acid resistance with rare-earth oxides was achieved by refining the grain size, strengthening the grain boundary, and turning Ca₂Al₂SiO₇, in which acid resistance is poor, into CaAl₁₂O₁₉, which possesses better acid resistance, and then enhance the acid resistance of the proppants. Furthermore, Pr₆O₁₁ can form a solid solution with Ca₂Al₂SiO₇ and CaAl₁₂O₁₉. The acid resistance of CaAl₁₂O₁₉ improves with the increase of solid solubility. In contrast, the acid resistance of Ca₂Al₂SiO₇ will decrease after Ca₂Al₂SiO₇ forms a solid solution with Pr₆O₁₁. Full article

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14 pages, 15198 KiB

Open AccessArticle

The Effect of Surfactant Content over Cu-Ni Coatings Electroplated by the sc-CO₂ Technique

by Ho-Chiao Chuang^*, Jorge Sánchez and Hsiang-Yun Cheng

Department of Mechanical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan

Materials 2017, 10(4), 428; https://doi.org/10.3390/ma10040428 - 19 Apr 2017

Cited by 8 | Viewed by 5471

Abstract

Co-plating of Cu-Ni coatings by supercritical CO₂ (sc-CO₂) and conventional electroplating processes was studied in this work. 1,4-butynediol was chosen as the surfactant and the effects of adjusting the surfactant content were described. Although the sc-CO₂ process displayed lower [...] Read more.

Co-plating of Cu-Ni coatings by supercritical CO₂ (sc-CO₂) and conventional electroplating processes was studied in this work. 1,4-butynediol was chosen as the surfactant and the effects of adjusting the surfactant content were described. Although the sc-CO₂ process displayed lower current efficiency, it effectively removed excess hydrogen that causes defects on the coating surface, refined grain size, reduced surface roughness, and increased electrochemical resistance. Surface roughness of coatings fabricated by the sc-CO₂ process was reduced by an average of 10%, and a maximum of 55%, compared to conventional process at different fabrication parameters. Cu-Ni coatings produced by the sc-CO₂ process displayed increased corrosion potential of ~0.05 V over Cu-Ni coatings produced by the conventional process, and 0.175 V over pure Cu coatings produced by the conventional process. For coatings ~10 µm thick, internal stress developed from the sc-CO₂ process were ~20 MPa lower than conventional process. Finally, the preferred crystal orientation of the fabricated coatings remained in the (111) direction regardless of the process used or surfactant content. Full article

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8 pages, 1081 KiB

Open AccessArticle

Transparent Thin-Film Transistors Based on Sputtered Electric Double Layer

by Wensi Cai, Xiaochen Ma, Jiawei Zhang and Aimin Song^*

School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, UK

Materials 2017, 10(4), 429; https://doi.org/10.3390/ma10040429 - 20 Apr 2017

Cited by 9 | Viewed by 6529

Abstract

Electric-double-layer (EDL) thin-film transistors (TFTs) have attracted much attention due to their low operation voltages. Recently, EDL TFTs gated with radio frequency (RF) magnetron sputtered SiO₂ have been developed which is compatible to large-area electronics fabrication. In this work, fully transparent Indium-Gallium-Zinc-Oxide-based [...] Read more.

Electric-double-layer (EDL) thin-film transistors (TFTs) have attracted much attention due to their low operation voltages. Recently, EDL TFTs gated with radio frequency (RF) magnetron sputtered SiO₂ have been developed which is compatible to large-area electronics fabrication. In this work, fully transparent Indium-Gallium-Zinc-Oxide-based EDL TFTs on glass substrates have been fabricated at room temperature for the first time. A maximum transmittance of about 80% has been achieved in the visible light range. The transparent TFTs show a low operation voltage of 1.5 V due to the large EDL capacitance (0.3 µF/cm² at 20 Hz). The devices exhibit a good performance with a low subthreshold swing of 130 mV/dec and a high on-off ratio > 10⁵. Several tests have also been done to investigate the influences of light irradiation and bias stress. Our results suggest that such transistors might have potential applications in battery-powered transparent electron devices. Full article

(This article belongs to the Special Issue Oxide Semiconductor Thin-Film Transistor)

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12 pages, 4829 KiB

Open AccessArticle

Effect of Elemental Sulfur and Sulfide on the Corrosion Behavior of Cr-Mo Low Alloy Steel for Tubing and Tubular Components in Oil and Gas Industry

by Ladan Khaksar^1,*

and John Shirokoff²

¹ Department of Mechanical Engineering, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada

² Department of Process Engineering, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada

Materials 2017, 10(4), 430; https://doi.org/10.3390/ma10040430 - 20 Apr 2017

Cited by 30 | Viewed by 5654

Abstract

The chemical degradation of alloy components in sulfur-containing environments is a major concern in oil and gas production. This paper discusses the effect of elemental sulfur and its simplest anion, sulfide, on the corrosion of Cr-Mo alloy steel at pH 2 and 5 [...] Read more.

The chemical degradation of alloy components in sulfur-containing environments is a major concern in oil and gas production. This paper discusses the effect of elemental sulfur and its simplest anion, sulfide, on the corrosion of Cr-Mo alloy steel at pH 2 and 5 during 10, 20 and 30 h immersion in two different solutions. 4130 Cr-Mo alloy steel is widely used as tubing and tubular components in sour services. According to the previous research in aqueous conditions, contact of solid sulfur with alloy steel can initiate catastrophic corrosion problems. The corrosion behavior was monitored by the potentiodynamic polarization technique during the experiments. Energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) have been applied to characterize the corrosion product layers after each experiment. The results show that under the same experimental conditions, the corrosion resistance of Cr-Mo alloy in the presence of elemental sulfur is significantly lower than its resistance in the presence of sulfide ions. Full article

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14 pages, 9417 KiB

Open AccessArticle

Heat-Polymerized Resin Containing Dimethylaminododecyl Methacrylate Inhibits Candida albicans Biofilm

by Hui Chen^1,2,3, Qi Han¹, Xuedong Zhou^1,2, Keke Zhang¹, Suping Wang^1,2, Hockin H. K. Xu⁴, Michael D. Weir⁴, Mingye Feng¹, Mingyun Li¹, Xian Peng¹, Biao Ren^1,* and Lei Cheng^1,2,*

¹ State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041, China

² Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China

³ Department of Preventive Dentistry, Stomatological Hospital of Chongqing Medical University, Chongqing 401147, China

⁴ Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA

Materials 2017, 10(4), 431; https://doi.org/10.3390/ma10040431 - 20 Apr 2017

Cited by 28 | Viewed by 5497

Abstract

The prevalence of stomatitis, especially caused by Candida albicans, has highlighted the need of new antifungal denture materials. This study aimed to develop an antifungal heat-curing resin containing quaternary ammonium monomer (dimethylaminododecyl methacrylate, DMADDM), and evaluate its physical performance and antifungal properties. [...] Read more.

The prevalence of stomatitis, especially caused by Candida albicans, has highlighted the need of new antifungal denture materials. This study aimed to develop an antifungal heat-curing resin containing quaternary ammonium monomer (dimethylaminododecyl methacrylate, DMADDM), and evaluate its physical performance and antifungal properties. The discs were prepared by incorporating DMADDM into the polymer liquid of a methyl methacrylate-based, heat-polymerizing resin at 0% (control), 5%, 10%, and 20% (w/w). Flexure strength, bond quality, surface charge density, and surface roughness were measured to evaluate the physical properties of resin. The specimens were incubated with C. albicans solution in medium to form biofilms. Then Colony-Forming Units, XTT assay, and scanning electron microscope were used to evaluate antifungal effect of DMADDM-modified resin. DMADDM modified acrylic resin had no effect on the flexural strength, bond quality, and surface roughness, but it increased the surface charge density significantly. Meanwhile, this new resin inhibited the C. albicans biofilm significantly according to the XTT assay and CFU counting. The hyphae in C. albicans biofilm also reduced in DMADDM-containing groups observed by SEM. DMADDM modified acrylic resin was effective in the inhibition of C. albicans biofilm with good physical properties. Full article

(This article belongs to the Section Biomaterials)

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11 pages, 2769 KiB

Open AccessArticle

Phosphor-Free InGaN White Light Emitting Diodes Using Flip-Chip Technology

by Ying-Chang Li¹, Liann-Be Chang^1,2,3,*, Hou-Jen Chen¹, Chia-Yi Yen¹, Ke-Wei Pan¹, Bohr-Ran Huang⁴

, Wen-Yu Kuo⁴, Lee Chow⁵

, Dan Zhou⁶ and Ewa Popko⁷

¹ Graduate Institute of Electro-Optical Engineering, Chang Gung University, Taoyuan 333, Taiwan

² Department of Otolaryngology-Head and Neck Surgery, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan

³ Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 243, Taiwan

⁴ Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

⁵ Department of Physics, University of Central Florida, Orlando, FL 32816, USA

⁶ Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816, USA

⁷ Institute of Physics, Wroclaw University of Technology, 50-370 Wroclaw, Poland

Materials 2017, 10(4), 432; https://doi.org/10.3390/ma10040432 - 20 Apr 2017

Cited by 12 | Viewed by 7583

Abstract

Monolithic phosphor-free two-color gallium nitride (GaN)-based white light emitting diodes (LED) have the potential to replace current phosphor-based GaN white LEDs due to their low cost and long life cycle. Unfortunately, the growth of high indium content indium gallium nitride (InGaN)/GaN quantum dot [...] Read more.

Monolithic phosphor-free two-color gallium nitride (GaN)-based white light emitting diodes (LED) have the potential to replace current phosphor-based GaN white LEDs due to their low cost and long life cycle. Unfortunately, the growth of high indium content indium gallium nitride (InGaN)/GaN quantum dot and reported LED’s color rendering index (CRI) are still problematic. Here, we use flip-chip technology to fabricate an upside down monolithic two-color phosphor-free LED with four grown layers of high indium quantum dots on top of the three grown layers of lower indium quantum wells separated by a GaN tunneling barrier layer. The photoluminescence (PL) and electroluminescence (EL) spectra of this white LED reveal a broad spectrum ranging from 475 to 675 nm which is close to an ideal white-light source. The corresponding color temperature and color rendering index (CRI) of the fabricated white LED, operated at 350, 500, and 750 mA, are comparable to that of the conventional phosphor-based LEDs. Insights of the epitaxial structure and the transport mechanism were revealed through the TEM and temperature dependent PL and EL measurements. Our results show true potential in the Epi-ready GaN white LEDs for future solid state lighting applications. Full article

(This article belongs to the Section Advanced Materials Characterization)

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30 pages, 5987 KiB

Open AccessArticle

An Energy-Equivalent d⁺/d⁻ Damage Model with Enhanced Microcrack Closure-Reopening Capabilities for Cohesive-Frictional Materials

by Miguel Cervera¹

and Claudia Tesei^2,*

¹ International Center for Numerical Methods in Engineering (CIMNE), Universidad Politécnica de Cataluña, Campus Norte UPC, 08034 Barcelona, Spain

² Department of Structural, Building and Geotechnical Engineering (DISEG), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

Materials 2017, 10(4), 433; https://doi.org/10.3390/ma10040433 - 20 Apr 2017

Cited by 19 | Viewed by 4737

Abstract

In this paper, an energy-equivalent orthotropic d⁺/d⁻ damage model for cohesive-frictional materials is formulated. Two essential mechanical features are addressed, the damage-induced anisotropy and the microcrack closure-reopening (MCR) effects, in order to provide an enhancement of the original d [...] Read more.

In this paper, an energy-equivalent orthotropic d⁺/d⁻ damage model for cohesive-frictional materials is formulated. Two essential mechanical features are addressed, the damage-induced anisotropy and the microcrack closure-reopening (MCR) effects, in order to provide an enhancement of the original d⁺/d⁻ model proposed by Faria et al. 1998, while keeping its high algorithmic efficiency unaltered. First, in order to ensure the symmetry and positive definiteness of the secant operator, the new formulation is developed in an energy-equivalence framework. This proves thermodynamic consistency and allows one to describe a fundamental feature of the orthotropic damage models, i.e., the reduction of the Poisson’s ratio throughout the damage process. Secondly, a “multidirectional” damage procedure is presented to extend the MCR capabilities of the original model. The fundamental aspects of this approach, devised for generic cyclic conditions, lie in maintaining only two scalar damage variables in the constitutive law, while preserving memory of the degradation directionality. The enhanced unilateral capabilities are explored with reference to the problem of a panel subjected to in-plane cyclic shear, with or without vertical pre-compression; depending on the ratio between shear and pre-compression, an absent, a partial or a complete stiffness recovery is simulated with the new multidirectional procedure. Full article

(This article belongs to the Special Issue Computational Mechanics of Cohesive-Frictional Materials)

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27 pages, 3718 KiB

Open AccessArticle

Strain Localization of Elastic-Damaging Frictional-Cohesive Materials: Analytical Results and Numerical Verification

by Jian-Ying Wu^1,* and Miguel Cervera²

¹ State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou 510641, China

² CIMNE, Technical University of Catalonia, Edificio C1, Campus Norte, Jordi Girona 1-3, 08034 Barcelona, Spain

Materials 2017, 10(4), 434; https://doi.org/10.3390/ma10040434 - 20 Apr 2017

Cited by 14 | Viewed by 5452

Abstract

Damage-induced strain softening is of vital importance for the modeling of localized failure in frictional-cohesive materials. This paper addresses strain localization of damaging solids and the resulting consistent frictional-cohesive crack models. As a supplement to the framework recently established for stress-based continuum material [...] Read more.

Damage-induced strain softening is of vital importance for the modeling of localized failure in frictional-cohesive materials. This paper addresses strain localization of damaging solids and the resulting consistent frictional-cohesive crack models. As a supplement to the framework recently established for stress-based continuum material models in rate form (Wu and Cervera 2015, 2016), several classical strain-based damage models, expressed usually in total and secant format, are considered. Upon strain localization of such damaging solids, Maxwell’s kinematics of a strong (or regularized) discontinuity has to be reproduced by the inelastic damage strains, which are defined by a bounded characteristic tensor and an unbounded scalar related to the damage variable. This kinematic constraint yields a set of nonlinear equations from which the discontinuity orientation and damage-type localized cohesive relations can be derived. It is found that for the “Simó and Ju 1987” isotropic damage model, the localization angles and the resulting cohesive model heavily depend on lateral deformations usually ignored in classical crack models for quasi-brittle solids. To remedy this inconsistency, a modified damage model is proposed. Its strain localization analysis naturally results in a consistent frictional-cohesive crack model of damage type, which can be regularized as a classical smeared crack model. The analytical results are numerically verified by the recently-proposed mixed stabilized finite element method, regarding a singly-perforated plate under uniaxial tension. Remarkably, for all of the damage models discussed in this work, the numerically-obtained localization angles agree almost exactly with the closed-form results. This agreement, on the one hand, consolidates the strain localization analysis based on Maxwell’s kinematics and, on the other hand, illustrates versatility of the mixed stabilized finite element method. Full article

(This article belongs to the Special Issue Computational Mechanics of Cohesive-Frictional Materials)

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12 pages, 11834 KiB

Open AccessArticle

Preparation and Characterization of Silica Aerogel Microspheres

by Qifeng Chen¹, Hui Wang^1,2,* and Luyi Sun^2,*

¹ College of Materials Science & Engineering, South China University of Technology, Guangzhou 510640, China

² Department of Chemical & Biomolecular Engineering and Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, CT 06269, USA

Materials 2017, 10(4), 435; https://doi.org/10.3390/ma10040435 - 20 Apr 2017

Cited by 33 | Viewed by 10131

Abstract

Silica aerogel microspheres based on alkali silica sol were synthesized using the emulsion method. The experimental results revealed that the silica aerogel microspheres (4–20 µm in diameter) were mesoporous solids with an average pore diameter ranging from 6 to 35 nm. The tapping [...] Read more.

Silica aerogel microspheres based on alkali silica sol were synthesized using the emulsion method. The experimental results revealed that the silica aerogel microspheres (4–20 µm in diameter) were mesoporous solids with an average pore diameter ranging from 6 to 35 nm. The tapping densities and specific surface areas of the aerogel microspheres are in the range of 0.112–0.287 g/cm³ and 207.5–660.6 m²/g, respectively. The diameter of the silica aerogel microspheres could be tailored by varying the processing conditions including agitation rate, water/oil ratio, mass ratio of Span 80: Tween 80, and emulsifier concentration. The effects of these parameters on the morphology and textural properties of the synthesized silica aerogel microspheres were systematically investigated. Such silica aerogel microspheres can be used to prepare large-scale silica aerogels at an ambient pressure for applications in separation and high efficiency catalysis, which requires features of high porosity and easy fill and recovery. Full article

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12 pages, 8228 KiB

Open AccessArticle

Mechanics of Pickering Drops Probed by Electric Field–Induced Stress

by Alexander Mikkelsen^1,2

, Paul Dommersnes^1,*, Zbigniew Rozynek^1,2

, Azarmidokht Gholamipour-Shirazi³, Marcio da Silveira Carvalho³ and Jon Otto Fossum^1,3,4

¹ Department of Physics, Norwegian University of Science and Technology, Høgskoleringen 5, NO-7491 Trondheim, Norway

² Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland

³ Department of Mechanical Engineering, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marquês de São Vicente, 225, Rio de Janeiro, Brazil

⁴ Institut Pierre-Gilles de Gennes, 6-12 rue Jean Calvin, Paris 75005, France

Materials 2017, 10(4), 436; https://doi.org/10.3390/ma10040436 - 21 Apr 2017

Cited by 13 | Viewed by 6020

Abstract

Fluid drops coated with particles, so-called Pickering drops, play an important role in emulsion and capsule applications. In this context, knowledge of mechanical properties and stability of Pickering drops are essential. Here we prepare Pickering drops via electric field-driven self-assembly. We use direct [...] Read more.

Fluid drops coated with particles, so-called Pickering drops, play an important role in emulsion and capsule applications. In this context, knowledge of mechanical properties and stability of Pickering drops are essential. Here we prepare Pickering drops via electric field-driven self-assembly. We use direct current (DC) electric fields to induce mechanical stress on these drops, as a possible alternative to the use of, for example, fluid flow fields. Drop deformation is monitored as a function of the applied electric field strength. The deformation of pure silicone oil drops is enhanced when covered by insulating polyethylene (PE) particles, whereas drops covered by conductive clay particles can also change shape from oblate to prolate. We attribute these results to changes in the electric conductivity of the drop interface after adding particles, and have developed a fluid shell description to estimate the conductivity of Pickering particle layers that are assumed to be non-jammed and fluid-like. Retraction experiments in the absence of electric fields are also performed. Particle-covered drops retract slower than particle-free drops, caused by increased viscous dissipation due to the presence of the Pickering particle layer. Full article

(This article belongs to the Special Issue Designed Colloidal Self-Assembly)

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11 pages, 2851 KiB

Open AccessArticle

In Situ TEM Study of Microstructure Evolution of Zr-Nb-Fe Alloy Irradiated by 800 keV Kr²⁺ Ions

by Penghui Lei, Guang Ran^*, Chenwei Liu, Chao Ye, Dong Lv, Jianxin Lin, Yizhen Wu and Jiangkun Xu

College of Energy, Xiamen University, Xiamen 361102, Fujian, China

Materials 2017, 10(4), 437; https://doi.org/10.3390/ma10040437 - 22 Apr 2017

Cited by 7 | Viewed by 5406

Abstract

The microstructure evolution of Zr-1.1Nb-1.51Fe-0.26Cu-0.72Ni zirconium alloy, irradiated by 800 keV Kr²⁺ ions at 585 K using the IVEM-Tandem Facility at Argonne National Laboratory, was observed by in situ transmission electron microscopy. A number of β-Nb precipitates with a body-centered cubic (BCC) [...] Read more.

The microstructure evolution of Zr-1.1Nb-1.51Fe-0.26Cu-0.72Ni zirconium alloy, irradiated by 800 keV Kr²⁺ ions at 585 K using the IVEM-Tandem Facility at Argonne National Laboratory, was observed by in situ transmission electron microscopy. A number of β-Nb precipitates with a body-centered cubic (BCC) structure were distributed in the as-received zirconium alloy with micrometer-size grains. Kr²⁺ ion irradiation induced the growth of β-Nb precipitates, which could be attributed to the segregation of the dissolved niobium atoms in the zirconium lattice and the migration to the existing precipitates. The size of precipitates was increased with increasing Kr²⁺ ion fluence. During Kr²⁺ iron irradiation, the zirconium crystals without Nb precipitates tended to transform to the nanocrystals, which was not observed in the zirconium crystals with Nb nanoparticles. The existing Nb nanoparticles were the key factor that constrained the nanocrystallization of zirconium crystals. The thickness of the formed Zr-nanocrystal layer was about 300 nm, which was consistent with the depth of Kr²⁺ iron irradiation. The mechanism of the precipitate growth and the formation of zirconium nanocrystal was analyzed and discussed. Full article

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9 pages, 4014 KiB

Open AccessArticle

Corrosion-Fatigue Crack Growth in Plates: A Model Based on the Paris Law

by Jesús Toribio^*, Juan-Carlos Matos

and Beatriz González

Fracture & Structural Integrity Research Group (FSIRG), University of Salamanca (USAL), E.P.S., Campus Viriato, Avda. Requejo 33, 49022 Zamora, Spain

Materials 2017, 10(4), 439; https://doi.org/10.3390/ma10040439 - 22 Apr 2017

Cited by 14 | Viewed by 6307

Abstract

In this paper, a Paris law-based model is presented whereby crack propagation occurs under cyclic loading in air (fatigue) and in an aggressive environment (corrosion-fatigue) for the case of corner cracks (with a wide range of aspect ratios in [...] Read more.

In this paper, a Paris law-based model is presented whereby crack propagation occurs under cyclic loading in air (fatigue) and in an aggressive environment (corrosion-fatigue) for the case of corner cracks (with a wide range of aspect ratios in the matter of the initial cracks) in finite-thickness plates of 316L austenitic stainless steel subjected to tension, bending, or combined (tension + bending) loading. Results show that the cracks tend during their growth towards a preferential propagation path, exhibiting aspect ratios slightly lower than unity only for the case of very shallow cracks, and diminishing as the crack grows (increasing the relative crack depth)—more intensely in the case of bending than in the case of tension (the mixed loading tension/bending representing an intermediate case). In addition, the crack aspect ratios during fatigue propagation evolution are lower in fatigue (in air) than in corrosion-fatigue (in aggressive environment). Full article

(This article belongs to the Special Issue Stress Corrosion Cracking in Materials)

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13 pages, 4808 KiB

Open AccessArticle

Preparation of Porous Poly(Styrene-Divinylbenzene) Microspheres and Their Modification with Diazoresin for Mix-Mode HPLC Separations

by Bing Yu^1,2, Tao Xu¹, Hailin Cong^1,2,*

, Qiaohong Peng¹ and Muhammad Usman¹

¹ Institute of Biomedical Materials and Engineering, College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, China

² Laboratory for New Fiber Materials and Modern Textile, Growing Base for State Key Laboratory, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, China

Materials 2017, 10(4), 440; https://doi.org/10.3390/ma10040440 - 22 Apr 2017

Cited by 28 | Viewed by 11012

Abstract

By using the two-step activated swelling method, monodisperse porous poly(styrene-divinylbenzene) (P(S-DVB)) microparticles were successfully synthesized. The influence of porogens, swelling temperatures and crosslinking agents on the porosity of porous microparticles was carefully investigated. Porous P(S-DVB) microparticles were used as a packing material for [...] Read more.

By using the two-step activated swelling method, monodisperse porous poly(styrene-divinylbenzene) (P(S-DVB)) microparticles were successfully synthesized. The influence of porogens, swelling temperatures and crosslinking agents on the porosity of porous microparticles was carefully investigated. Porous P(S-DVB) microparticles were used as a packing material for high performance liquid chromatography (HPLC). Several benzene analogues were effectively separated in a stainless-steel column as short as 75 mm due to the high specific surface area of the porous microparticles. Porous P(S-DVB) microparticles were further sulfonated and subsequently modified with diazoresin (DR) via electrostatic self-assembly and UV (ultraviolet) radiation. After treatment with UV light, the ionic bonding between sulfonated P(S-DVB) and DR was converted into covalent bonding through a unique photochemistry reaction of DR. Depending on the chemical structure of DR and mobile phase composition, the DR-modified P(S-DVB) stationary phase performed different separation mechanisms, including reversed phase (RP) and hydrophilic interactions. Therefore, baseline separations of benzene analogues and organic acids were achieved by using the DR-modified P(S-DVB) particles as packing materials in HPLC. According to the π–π interactional difference between carbon rings of fullerenes and benzene rings of DR, C₆₀ and C₇₀ were also well separated in the HPLC column packed with DR-modified P(S-DVB) particles. Full article

(This article belongs to the Section Porous Materials)

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13 pages, 3223 KiB

Open AccessArticle

A Novel Silicon Allotrope in the Monoclinic Phase

by Chaogang Bai, Changchun Chai, Qingyang Fan^*, Yuqian Liu and Yintang Yang

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

Materials 2017, 10(4), 441; https://doi.org/10.3390/ma10040441 - 22 Apr 2017

Cited by 18 | Viewed by 5790 | Correction

Abstract

This paper describes a new silicon allotrope in the P2/m space group found by first-principles calculations using the Cambridge Serial Total Energy Package (CASTEP) plane-wave code. The examined P2/m-Si belongs to the monoclinic crystal system. P2/m [...] Read more.

This paper describes a new silicon allotrope in the P2/m space group found by first-principles calculations using the Cambridge Serial Total Energy Package (CASTEP) plane-wave code. The examined P2/m-Si belongs to the monoclinic crystal system. P2/m-Si is an indirect band-gap semiconductor with a band gap of 1.51 eV, as determined using the HSE06 hybrid functional. The elastic constants, phonon spectra and enthalpy indicate that P2/m-Si is mechanically, dynamically, and thermodynamically stable. P2/m-Si is a low-density (2.19 g/cm³) silicon allotrope. The value of B/G is less than 1.75, which indicates that the new allotrope is brittle. It is shown that the difference in the elastic anisotropy along different orientations is greater than that in other phases. Finally, to understand the thermodynamic properties of P2/m-Si, the thermal expansion coefficient α, the Debye temperature Θ_D, and the heat capacities C_P and C_V are also investigated in detail. Full article

(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)

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12 pages, 2563 KiB

Open AccessArticle

Linear Graphene Nanocomposite Synthesis and an Analytical Application for the Amino Acid Detection of Camellia nitidissima Chi Seeds

by Jinsheng Cheng^1,2,*

, Ruimin Zhong^1,*, Jiajian Lin¹, Jianhua Zhu¹, Weihong Wan¹ and Xinyan Chen³

¹ School of Ying-Dong Food Sciences and Engineering, Shaoguan University, Shaoguan 512005, China

² Soochow Tanfeng Graphene Technology Co. Ltd., Suzhou 215100, China

³ School of Medicine, Jiaying University, Meizhou 513031, China

Materials 2017, 10(4), 443; https://doi.org/10.3390/ma10040443 - 24 Apr 2017

Cited by 9 | Viewed by 5063

Abstract

Husk derived amino modified linear graphene nanocomposites (aLGN) with a diameter range of 80–300 nm and a length range of 100–300 μm were prepared by a modified Hummers method, ammonia treatment, NaBH₄ reduction and phenylalanine induced assembly processes, etc. The resulting composites [...] Read more.

Husk derived amino modified linear graphene nanocomposites (aLGN) with a diameter range of 80–300 nm and a length range of 100–300 μm were prepared by a modified Hummers method, ammonia treatment, NaBH₄ reduction and phenylalanine induced assembly processes, etc. The resulting composites were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), biological microscope (BM), and X-ray diffraction spectroscopy (XRD), etc. Investigations found that the aLGN can serve as the novel coating of stir bar sorptive extraction (SBSE) technology. By combing this technology with gas chromatography–mass spectrometry (GC-MS), the combined SBSE/GC-MS technology with an aLGN coating can detect seventeen kinds of amino acids of Camellia nitidissima Chi seeds, including Ala, Gly, Thr, Ser, Val, Leu, Ile, Cys, Pro, Met, Asp, Phe, Glu, Lys, Tyr, His, and Arg. Compared to a conventional polydimethylsiloxane (PDMS) coating, an aLGN coating for SBSE exhibited a better thermal desorption performance, better analytes fragmentation depressing efficiencies, higher peak intensities, and superior amino acid discrimination, leading to a practicable and highly distinguishable method for the variable amino acid detection of Camellia nitidissima Chi seeds. Full article

(This article belongs to the Special Issue Bioapplications of Graphene Composites)

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15 pages, 995 KiB

Open AccessArticle

Thermophysical Characterization of MgCl₂·6H₂O, Xylitol and Erythritol as Phase Change Materials (PCM) for Latent Heat Thermal Energy Storage (LHTES)

by Stephan Höhlein^*

, Andreas König-Haagen and Dieter Brüggemann

Chair of Engineering Thermodynamics and Transport Processes (LTTT), Center of Energy Technology (ZET), University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany

Materials 2017, 10(4), 444; https://doi.org/10.3390/ma10040444 - 24 Apr 2017

Cited by 107 | Viewed by 10133

Abstract

The application range of existing real scale mobile thermal storage units with phase change materials (PCM) is restricted by the low phase change temperature of 58

^{\circ} C

for sodium acetate trihydrate, which is a commonly used storage material. Therefore, only low temperature [...] Read more.

The application range of existing real scale mobile thermal storage units with phase change materials (PCM) is restricted by the low phase change temperature of 58

^{\circ} C

for sodium acetate trihydrate, which is a commonly used storage material. Therefore, only low temperature heat sinks like swimming pools or greenhouses can be supplied. With increasing phase change temperatures, more applications like domestic heating or industrial process heat could be operated. The aim of this study is to find alternative PCM with phase change temperatures between 90 and 150

^{\circ} C

. Temperature dependent thermophysical properties like phase change temperatures and enthalpies, densities and thermal diffusivities are measured for the technical grade purity materials xylitol (C

_{5}

H

_{12}

O

_{5}

), erythritol (C

_{4}

H

_{10}

O

_{4}

) and magnesiumchloride hexahydrate (MCHH, MgCl

_{2}

\cdot

6H

_{2}

O). The sugar alcohols xylitol and erythritol indicate a large supercooling and different melting regimes. The salt hydrate MgCl

_{2}

\cdot

6H

_{2}

O seems to be a suitable candidate for practical applications. It has a melting temperature of 115.1 ± 0.1

^{\circ} C

and a phase change enthalpy of 166.9 ± 1.2

J / g

with only 2.8

K

supercooling at sample sizes of 100

g

. The PCM is stable over 500 repeated melting and solidification cycles at differential scanning calorimeter (DSC) scale with only small changes of the melting enthalpy and temperature. Full article

(This article belongs to the Section Energy Materials)

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16 pages, 4851 KiB

Open AccessArticle

Osteoblast Cell Response on the Ti6Al4V Alloy Heat-Treated

by Mercedes Paulina Chávez-Díaz^1,2, María Lorenza Escudero-Rincón², Elsa Miriam Arce-Estrada¹ and Román Cabrera-Sierra^3,*

¹ Departamento de Ingeniería en Metalurgia y Materiales, Instituto Politécnico Nacional (ESIQIE-IPN), UPALM Zacatenco, Ciudad de México 07738, Mexico

² Departamento de Ingeniería de Superficies, Corrosión y Durabilidad, Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Madrid 28040, Spain

³ Departamento de Ingeniería Química Industrial, Instituto Politécnico Nacional (ESIQIE-IPN), UPALM Zacatenco, Ciudad de México 07738, Mexico

Materials 2017, 10(4), 445; https://doi.org/10.3390/ma10040445 - 23 Apr 2017

Cited by 15 | Viewed by 4998

Abstract

In an effort to examine the effect of the microstructural changes of the Ti6Al4V alloy, two heat treatments were carried out below (Ti6Al4V₈₀₀) and above (Ti6Al4V₁₀₅₀) its β-phase transformation temperature. After each treatment, globular and lamellar microstructures were obtained. [...] Read more.

In an effort to examine the effect of the microstructural changes of the Ti6Al4V alloy, two heat treatments were carried out below (Ti6Al4V₈₀₀) and above (Ti6Al4V₁₀₅₀) its β-phase transformation temperature. After each treatment, globular and lamellar microstructures were obtained. Saos-2 pre-osteoblast human osteosarcoma cells were seeded onto Ti6Al4V alloy disks and immersed in cell culture for 7 days. Electrochemical assays in situ were performed using OCP and EIS measurements. Impedance data show a passive behavior for the three Ti6Al4V alloys; additionally, enhanced impedance values were recorded for Ti6Al4V₈₀₀ and Ti6Al4V₁₀₅₀ alloys. This passive behavior in culture medium is mostly due to the formation of TiO₂ during their sterilization. Biocompatibility and cell adhesion were characterized using the SEM technique; Ti6Al4V as received and Ti6Al4V₈₀₀ alloys exhibited polygonal and elongated morphology, whereas Ti6Al4V₁₀₅₀ alloy displayed a spherical morphology. Ti and O elements were identified by EDX analysis due to the TiO₂ and signals of C, N and O, related to the formation of organic compounds from extracellular matrix. These results suggest that cell adhesion is more likely to occur on TiO₂ formed in discrete α-phase regions (hcp) depending on its microstructure (grains). Full article

(This article belongs to the Section Biomaterials)

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10 pages, 2280 KiB

Open AccessArticle

Strong Photoluminescence Enhancement of Silicon Oxycarbide through Defect Engineering

by Brian Ford, Natasha Tabassum, Vasileios Nikas and Spyros Gallis^*

Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY 12203, USA

Materials 2017, 10(4), 446; https://doi.org/10.3390/ma10040446 - 23 Apr 2017

Cited by 10 | Viewed by 7042

Abstract

The following study focuses on the photoluminescence (PL) enhancement of chemically synthesized silicon oxycarbide (SiC_xO_y) thin films and nanowires through defect engineering via post-deposition passivation treatments. SiC_xO_y materials were deposited via thermal chemical vapor deposition (TCVD), [...] Read more.

The following study focuses on the photoluminescence (PL) enhancement of chemically synthesized silicon oxycarbide (SiC_xO_y) thin films and nanowires through defect engineering via post-deposition passivation treatments. SiC_xO_y materials were deposited via thermal chemical vapor deposition (TCVD), and exhibit strong white light emission at room-temperature. Post-deposition passivation treatments were carried out using oxygen, nitrogen, and forming gas (FG, 5% H₂, 95% N₂) ambients, modifying the observed white light emission. The observed white luminescence was found to be inversely related to the carbonyl (C=O) bond density present in the films. The peak-to-peak PL was enhanced ~18 and ~17 times for, respectively, the two SiC_xO_y matrices, oxygen-rich and carbon-rich SiC_xO_y, via post-deposition passivations. Through a combinational and systematic Fourier transform infrared spectroscopy (FTIR) and PL study, it was revealed that proper tailoring of the passivations reduces the carbonyl bond density by a factor of ~2.2, corresponding to a PL enhancement of ~50 times. Furthermore, the temperature-dependent and temperature-dependent time resolved PL (TDPL and TD-TRPL) behaviors of the nitrogen and forming gas passivated SiC_xO_y thin films were investigated to acquire further insight into the ramifications of the passivation on the carbonyl/dangling bond density and PL yield. Full article

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13 pages, 2560 KiB

Open AccessArticle

Cesium and Strontium Retentions Governed by Aluminosilicate Gel in Alkali-Activated Cements

by Jeong Gook Jang¹

, Sol Moi Park²

and Haeng Ki Lee^2,*

¹ Korea Institute of Geoscience and Mineral Resources, 124 Gwahak-ro, Yuseong-gu, Daejeon 34132, Korea

² Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea

Materials 2017, 10(4), 447; https://doi.org/10.3390/ma10040447 - 23 Apr 2017

Cited by 25 | Viewed by 5246

Abstract

The present study investigates the retention mechanisms of cesium and strontium for alkali-activated cements. Retention mechanisms such as adsorption and precipitation were examined in light of chemical interactions. Batch adsorption experiments and multi-technical characterizations by using X-ray diffraction, zeta potential measurements, and the [...] Read more.

The present study investigates the retention mechanisms of cesium and strontium for alkali-activated cements. Retention mechanisms such as adsorption and precipitation were examined in light of chemical interactions. Batch adsorption experiments and multi-technical characterizations by using X-ray diffraction, zeta potential measurements, and the N₂ gas adsorption/desorption methods were conducted for this purpose. Strontium was found to crystalize in alkali-activated cements, while no cesium-bearing crystalline phases were detected. The adsorption kinetics of alkali-activated cements having relatively high adsorption capacities were compatible with pseudo-second-order kinetic model, thereby suggesting that it is governed by complex multistep adsorption. The results provide new insight, demonstrating that characteristics of aluminosilicate gel with a highly negatively charged surface and high micropore surface area facilitated more effective immobilization of cesium and strontium in comparison with calcium silicate hydrates. Full article

(This article belongs to the Section Advanced Composites)

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10 pages, 8280 KiB

Open AccessArticle

Production of High-Purity Anhydrous Nickel(II) Perrhenate for Tungsten-Based Sintered Heavy Alloys

by Katarzyna Leszczyńska-Sejda^1,*

, Grzegorz Benke¹, Dorota Kopyto¹, Tomasz Majewski² and Michał Drzazga¹

¹ Institute of Non Ferrous Metals (IMN), Hydrometallurgy Department, Sowińskiego 5, 44-100 Gliwice, Poland

² Military University of Technology in Warsaw (WAT), Kaliskiego 2, 00-908 Warszawa 49, Poland

Materials 2017, 10(4), 448; https://doi.org/10.3390/ma10040448 - 24 Apr 2017

Cited by 10 | Viewed by 3965

Abstract

This paper presents a method for the production of high-purity anhydrous nickel(II) perrhenate. The method comprises sorption of nickel(II) ions from aqueous nickel(II) nitrate solutions, using strongly acidic C160 cation exchange resin, and subsequent elution of sorbed nickel(II) ions using concentrated perrhenic acid [...] Read more.

This paper presents a method for the production of high-purity anhydrous nickel(II) perrhenate. The method comprises sorption of nickel(II) ions from aqueous nickel(II) nitrate solutions, using strongly acidic C160 cation exchange resin, and subsequent elution of sorbed nickel(II) ions using concentrated perrhenic acid solutions. After the neutralization of the resulting rhenium-nickel solutions, hydrated nickel(II) perrhenate is then separated and then dried at 160 °C to obtain the anhydrous form. The resulting compound is reduced in an atmosphere of dissociated ammonia in order to produce a Re-Ni alloy powder. This study provides information on the selected properties of the resulting Re-Ni powder. This powder was used as a starting material for the production of 77W-20Re-3Ni heavy alloys. Microstructure examination results and selected properties of the produced sintered heavy alloys were compared to sintered alloys produced using elemental W, Re, and Ni powders. This study showed that the application of anhydrous nickel(II) perrhenate in the production of 77W-20Re-3Ni results in better properties of the sintered alloys compared to those made from elemental powders. Full article

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

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Review

Jump to: Editorial, Research

104 pages, 19684 KiB

Open AccessFeature PaperReview

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

by Noam Eliaz^*

and Noah Metoki

Biomaterials and Corrosion Lab, Department of Materials Science and Engineering, Tel-Aviv University, Ramat Aviv 6997801, Israel

Materials 2017, 10(4), 334; https://doi.org/10.3390/ma10040334 - 24 Mar 2017

Cited by 874 | Viewed by 37498

Abstract

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of [...] Read more.

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs. Full article

(This article belongs to the Special Issue Calcium Phosphate in Biomedical Applications)

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12 pages, 17316 KiB

Open AccessReview

Toughening Mechanisms in Nanolayered MAX Phase Ceramics—A Review

by Xinhua Chen¹ and Guoping Bei^2,*

¹ School of Mechanical Electronic and Automobile Engineering, Beijing University of Civil Engineering and Architecture, Beijing 100044, China

² Department of Materials Science and Engineering, 3ME, Delft University of Technology, Mekelweg 2, 2628CD Delft, The Netherlands

Materials 2017, 10(4), 366; https://doi.org/10.3390/ma10040366 - 30 Mar 2017

Cited by 55 | Viewed by 11151

Abstract

Advanced engineering and functional ceramics are sensitive to damage cracks, which delay the wide applications of these materials in various fields. Ceramic composites with enhanced fracture toughness may trigger a paradigm for design and application of the brittle components. This paper reviews the [...] Read more.

Advanced engineering and functional ceramics are sensitive to damage cracks, which delay the wide applications of these materials in various fields. Ceramic composites with enhanced fracture toughness may trigger a paradigm for design and application of the brittle components. This paper reviews the toughening mechanisms for the nanolayered MAX phase ceramics. The main toughening mechanisms for these ternary compounds were controlled by particle toughening, phase-transformation toughening and fiber-reinforced toughening, as well as texture toughening. Based on the various toughening mechanisms in MAX phase, models of SiC particles and fibers toughening Ti₃SiC₂ are established to predict and explain the toughening mechanisms. The modeling work provides insights and guidance to fabricate MAX phase-related composites with optimized microstructures in order to achieve the desired mechanical properties required for harsh application environments. Full article

(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)

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22 pages, 3333 KiB

Open AccessFeature PaperReview

Controlling Oxygen Mobility in Ruddlesden–Popper Oxides

by Dongkyu Lee

and Ho Nyung Lee^*

Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

Materials 2017, 10(4), 368; https://doi.org/10.3390/ma10040368 - 31 Mar 2017

Cited by 130 | Viewed by 11855

Abstract

Discovering new energy materials is a key step toward satisfying the needs for next-generation energy conversion and storage devices. Among the various types of oxides, Ruddlesden–Popper (RP) oxides (A₂BO₄) are promising candidates for electrochemical energy devices, such as solid [...] Read more.

Discovering new energy materials is a key step toward satisfying the needs for next-generation energy conversion and storage devices. Among the various types of oxides, Ruddlesden–Popper (RP) oxides (A₂BO₄) are promising candidates for electrochemical energy devices, such as solid oxide fuel cells, owing to their attractive physicochemical properties, including the anisotropic nature of oxygen migration and controllable stoichiometry from oxygen excess to oxygen deficiency. Thus, understanding and controlling the kinetics of oxygen transport are essential for designing optimized materials to use in electrochemical energy devices. In this review, we first discuss the basic mechanisms of oxygen migration in RP oxides depending on oxygen nonstoichiometry. We then focus on the effect of changes in the defect concentration, crystallographic orientation, and strain on the oxygen migration in RP oxides. We also briefly review their thermal and chemical stability. Finally, we conclude with a perspective on potential research directions for future investigation to facilitate controlling oxygen ion migration in RP oxides. Full article

(This article belongs to the Special Issue (Photo)Electrochemistry of Perovskites)

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19 pages, 2706 KiB

Open AccessReview

Research Advances of Microencapsulation and Its Prospects in the Petroleum Industry

by Miaomiao Hu¹, Jintang Guo^1,*, Yongjin Yu^1,2, Lei Cao¹ and Yang Xu¹

¹ School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China

² Drilling Research Institute, China National Petroleum Corporation, Beijing 102206, China

Materials 2017, 10(4), 369; https://doi.org/10.3390/ma10040369 - 31 Mar 2017

Cited by 28 | Viewed by 8461

Abstract

Additives in the petroleum industry have helped form an efficient system in the past few decades. Nowadays, the development of oil and gas has been facing more adverse conditions, and smart response microcapsules with the abilities of self-healing, and delayed and targeted release [...] Read more.

Additives in the petroleum industry have helped form an efficient system in the past few decades. Nowadays, the development of oil and gas has been facing more adverse conditions, and smart response microcapsules with the abilities of self-healing, and delayed and targeted release are introduced to eliminate obstacles for further exploration in the petroleum industry. However, limited information is available, only that of field measurement data, and not mechanism theory and structural innovation data. Thus we propose that the basic type, preparation, as well as mechanism of microcapsules partly depend on other mature fields. In this review, we explore the latest advancements in evaluating microcapsules, such as X-ray computed tomography (XCT), simulation, and modeling. Finally, some novel microencapsulated additives with unparalleled advantages, such as flexibility, efficiency, and energy-conservation are described. Full article

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10 pages, 2083 KiB

Open AccessReview

The Results of 45 Years of Atmospheric Corrosion Study in the Czech Republic

by Katerina Kreislova^*

and Dagmar Knotkova

SVUOM Ltd., U Mestanskeho pivovaru 934, 170 00 Prague 7, Czech Republic

Materials 2017, 10(4), 394; https://doi.org/10.3390/ma10040394 - 7 Apr 2017

Cited by 34 | Viewed by 5874

Abstract

Atmospheric corrosion poses a significant problem with regard to destruction of various materials, especially metals. Observations made over the past decades suggest that the world’s climate is changing. Besides global warming, there are also changes in other parameters. For example, average annual precipitation [...] Read more.

Atmospheric corrosion poses a significant problem with regard to destruction of various materials, especially metals. Observations made over the past decades suggest that the world’s climate is changing. Besides global warming, there are also changes in other parameters. For example, average annual precipitation increased by nearly 10% over the course of the 20th century. In Europe, the most significant change, from the atmospheric corrosion point of view, was an increase in SO₂ pollution in the 1970s through the 1980s and a subsequent decrease in this same industrial air pollution and an increase in other types of air pollution, which created a so-called multi-pollutant atmospheric environment. Exposed metals react to such changes immediately, even if corrosion attack started in high corrosive atmospheres. This paper presents a complex evaluation of the effect of air pollution and other environmental parameters and verification of dose/response equations for conditions in the Czech Republic. Full article

(This article belongs to the Special Issue Fundamental and Research Frontier of Atmospheric Corrosion)

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67 pages, 19219 KiB

Open AccessReview

Marine Atmospheric Corrosion of Carbon Steel: A Review

by Jenifer Alcántara, Daniel de la Fuente, Belén Chico, Joaquín Simancas, Iván Díaz and Manuel Morcillo^*

National Centre for Metallurgical Research (CENIM/CSIC), Avda. Gregorio del Amo n° 8, 28040 Madrid, Spain

Materials 2017, 10(4), 406; https://doi.org/10.3390/ma10040406 - 13 Apr 2017

Cited by 297 | Viewed by 23523

Abstract

The atmospheric corrosion of carbon steel is an extensive topic that has been studied over the years by many researchers. However, until relatively recently, surprisingly little attention has been paid to the action of marine chlorides. Corrosion in coastal regions is a particularly [...] Read more.

The atmospheric corrosion of carbon steel is an extensive topic that has been studied over the years by many researchers. However, until relatively recently, surprisingly little attention has been paid to the action of marine chlorides. Corrosion in coastal regions is a particularly relevant issue due the latter’s great importance to human society. About half of the world’s population lives in coastal regions and the industrialisation of developing countries tends to concentrate production plants close to the sea. Until the start of the 21st century, research on the basic mechanisms of rust formation in Cl⁻-rich atmospheres was limited to just a small number of studies. However, in recent years, scientific understanding of marine atmospheric corrosion has advanced greatly, and in the authors’ opinion a sufficient body of knowledge has been built up in published scientific papers to warrant an up-to-date review of the current state-of-the-art and to assess what issues still need to be addressed. That is the purpose of the present review. After a preliminary section devoted to basic concepts on atmospheric corrosion, the marine atmosphere, and experimentation on marine atmospheric corrosion, the paper addresses key aspects such as the most significant corrosion products, the characteristics of the rust layers formed, and the mechanisms of steel corrosion in marine atmospheres. Special attention is then paid to important matters such as coastal-industrial atmospheres and long-term behaviour of carbon steel exposed to marine atmospheres. The work ends with a section dedicated to issues pending, noting a series of questions in relation with which greater research efforts would seem to be necessary. Full article

(This article belongs to the Special Issue Fundamental and Research Frontier of Atmospheric Corrosion)

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37 pages, 7600 KiB

Open AccessReview

Vibrational Spectroscopy in Studies of Atmospheric Corrosion

by Saman Hosseinpour^1,†

and Magnus Johnson^2,*

¹ Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

² Department of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden

^† Current Address: Institute of Particle Technology (LFG), FAU Erlangen-Nürnberg, Erlangen, Germany

Materials 2017, 10(4), 413; https://doi.org/10.3390/ma10040413 - 18 Apr 2017

Cited by 23 | Viewed by 7451

Abstract

Vibrational spectroscopy has been successfully used for decades in studies of the atmospheric corrosion processes, mainly to identify the nature of corrosion products but also to quantify their amounts. In this review article, a summary of the main achievements is presented with focus [...] Read more.

Vibrational spectroscopy has been successfully used for decades in studies of the atmospheric corrosion processes, mainly to identify the nature of corrosion products but also to quantify their amounts. In this review article, a summary of the main achievements is presented with focus on how the techniques infrared spectroscopy, Raman spectroscopy, and vibrational sum frequency spectroscopy can be used in the field. Several different studies have been discussed where these instruments have been used to assess both the nature of corrosion products as well as the properties of corrosion inhibitors. Some of these techniques offer the valuable possibility to perform in-situ measurements in real time on ongoing corrosion processes, which allows the kinetics of formation of corrosion products to be studied, and also minimizes the risk of changing the surface properties which may occur during ex-situ experiments. Since corrosion processes often occur heterogeneously over a surface, it is of great importance to obtain a deeper knowledge about atmospheric corrosion phenomena on the nano scale, and this review also discusses novel vibrational microscopy techniques allowing spectra to be acquired with a spatial resolution of 20 nm. Full article

(This article belongs to the Special Issue Fundamental and Research Frontier of Atmospheric Corrosion)

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31 pages, 18610 KiB

Open AccessReview

Thermoelectric Transport in Nanocomposites

by Bin Liu¹, Jizhu Hu¹, Jun Zhou^1,* and Ronggui Yang²

¹ Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China

² Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309, USA

Materials 2017, 10(4), 418; https://doi.org/10.3390/ma10040418 - 15 Apr 2017

Cited by 37 | Viewed by 6800

Abstract

Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit (ZT [...] Read more.

Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit (ZT). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT. Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed. Full article

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

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22 pages, 8795 KiB

Open AccessReview

Crystallization of Polymers Investigated by Temperature-Modulated DSC

by Maria Cristina Righetti

National Research Council of Italy—Institute for Chemical and Physical Processes (CNR-IPCF), Via Moruzzi 1, 56124 Pisa, Italy

Materials 2017, 10(4), 442; https://doi.org/10.3390/ma10040442 - 24 Apr 2017

Cited by 45 | Viewed by 12436

Abstract

The aim of this review is to summarize studies conducted by temperature-modulated differential scanning calorimetry (TMDSC) on polymer crystallization. This technique can provide several advantages for the analysis of polymers with respect to conventional differential scanning calorimetry. Crystallizations conducted by TMDSC in different [...] Read more.

The aim of this review is to summarize studies conducted by temperature-modulated differential scanning calorimetry (TMDSC) on polymer crystallization. This technique can provide several advantages for the analysis of polymers with respect to conventional differential scanning calorimetry. Crystallizations conducted by TMDSC in different experimental conditions are analysed and discussed, in order to illustrate the type of information that can be deduced. Isothermal and non-isothermal crystallizations upon heating and cooling are examined separately, together with the relevant mathematical treatments that allow the evolution of the crystalline, mobile amorphous and rigid amorphous fractions to be determined. The phenomena of ‘reversing’ and ‘reversible‘ melting are explicated through the analysis of the thermal response of various semi-crystalline polymers to temperature modulation. Full article

(This article belongs to the Special Issue Thermal Sciences and Thermodynamics of Materials)

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