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Materials, Volume 9, Issue 2 (February 2016) – 53 articles

Cover Story (view full-size image): The risk of infectious diseases can be diminished while using materials with antibacterial properties. PHMB is a good example of a strong, diverse, antimicrobial agent with low toxicity, which has attracted much attention for its effective antimicrobial finishing. This article presents the results concerning laminates with antimicrobial properties imparted by PHMB embedded in the MF resin. This work is the result of collaboration between the SONAE-Industria group and several Portuguese Universities. View the paper
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13 pages, 3259 KiB  
Article
Deposition of Visible Light Active Photocatalytic Bismuth Molybdate Thin Films by Reactive Magnetron Sputtering
by Marina Ratova, Peter J. Kelly, Glen T. West, Xiaohong Xia and Yun Gao
Materials 2016, 9(2), 67; https://doi.org/10.3390/ma9020067 - 22 Jan 2016
Cited by 22 | Viewed by 7124
Abstract
Bismuth molybdate thin films were deposited by reactive magnetron co-sputtering from two metallic targets in an argon/oxygen atmosphere, reportedly for the first time. Energy dispersive X-ray spectroscopy (EDX) analysis showed that the ratio of bismuth to molybdenum in the coatings can be effectively [...] Read more.
Bismuth molybdate thin films were deposited by reactive magnetron co-sputtering from two metallic targets in an argon/oxygen atmosphere, reportedly for the first time. Energy dispersive X-ray spectroscopy (EDX) analysis showed that the ratio of bismuth to molybdenum in the coatings can be effectively controlled by varying the power applied to each target. Deposited coatings were annealed in air at 673 K for 30 min. The crystalline structure was assessed by means of Raman spectroscopy and X-ray diffraction (XRD). Oxidation state information was obtained by X-ray photoelectron spectroscopy (XPS). Photodegradation of organic dyes methylene blue and rhodamine B was used for evaluation of the photocatalytic properties of the coatings under a visible light source. The photocatalytic properties of the deposited coatings were then compared to a sample of commercial titanium dioxide-based photocatalytic product. The repeatability of the dye degradation reactions and photocatalytic coating reusability are discussed. It was found that coatings with a Bi:Mo ratio of approximately 2:1 exhibited the highest photocatalytic activity of the coatings studied; its efficacy in dye photodegradation significantly outperformed a sample of commercial photocatalytic coating. Full article
(This article belongs to the Special Issue Advancement of Photocatalytic Materials 2016)
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12 pages, 2190 KiB  
Article
Mechanical Strength Improvements of Carbon Nanotube Threads through Epoxy Cross-Linking
by Qingyue Yu, Noe T. Alvarez, Peter Miller, Rachit Malik, Mark R. Haase, Mark Schulz, Vesselin Shanov and Xinbao Zhu
Materials 2016, 9(2), 68; https://doi.org/10.3390/ma9020068 - 25 Jan 2016
Cited by 30 | Viewed by 7782
Abstract
Individual Carbon Nanotubes (CNTs) have a great mechanical strength that needs to be transferred into macroscopic fiber assemblies. One approach to improve the mechanical strength of the CNT assemblies is by creating covalent bonding among their individual CNT building blocks. Chemical cross-linking of [...] Read more.
Individual Carbon Nanotubes (CNTs) have a great mechanical strength that needs to be transferred into macroscopic fiber assemblies. One approach to improve the mechanical strength of the CNT assemblies is by creating covalent bonding among their individual CNT building blocks. Chemical cross-linking of multiwall CNTs (MWCNTs) within the fiber has significantly improved the strength of MWCNT thread. Results reported in this work show that the cross-linked thread had a tensile strength six times greater than the strength of its control counterpart, a pristine MWCNT thread (1192 MPa and 194 MPa, respectively). Additionally, electrical conductivity changes were observed, revealing 2123.40 S·cm−1 for cross-linked thread, and 3984.26 S·cm−1 for pristine CNT thread. Characterization suggests that the obtained high tensile strength is due to the cross-linking reaction of amine groups from ethylenediamine plasma-functionalized CNT with the epoxy groups of the cross-linking agent, 4,4-methylenebis(N,N-diglycidylaniline). Full article
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13 pages, 5008 KiB  
Article
Controllable Electrochemical Synthesis of Reduced Graphene Oxide Thin-Film Constructed as Efficient Photoanode in Dye-Sensitized Solar Cells
by Soon Weng Chong, Chin Wei Lai and Sharifah Bee Abd Hamid
Materials 2016, 9(2), 69; https://doi.org/10.3390/ma9020069 - 25 Jan 2016
Cited by 19 | Viewed by 7627
Abstract
A controllable electrochemical synthesis to convert reduced graphene oxide (rGO) from graphite flakes was introduced and investigated in detail. Electrochemical reduction was used to prepare rGO because of its cost effectiveness, environmental friendliness, and ability to produce rGO thin films in industrial scale. [...] Read more.
A controllable electrochemical synthesis to convert reduced graphene oxide (rGO) from graphite flakes was introduced and investigated in detail. Electrochemical reduction was used to prepare rGO because of its cost effectiveness, environmental friendliness, and ability to produce rGO thin films in industrial scale. This study aimed to determine the optimum applied potential for the electrochemical reduction. An applied voltage of 15 V successfully formed a uniformly coated rGO thin film, which significantly promoted effective electron transfer within dye-sensitized solar cells (DSSCs). Thus, DSSC performance improved. However, rGO thin films formed in voltages below or exceeding 15 V resulted in poor DSSC performance. This behavior was due to poor electron transfer within the rGO thin films caused by poor uniformity. These results revealed that DSSC constructed using 15 V rGO thin film exhibited high efficiency (η = 1.5211%) attributed to its higher surface uniformity than other samples. The addition of natural lemon juice (pH ~ 2.3) to the electrolyte accelerated the deposition and strengthened the adhesion of rGO thin film onto fluorine-doped tin oxide (FTO) glasses. Full article
(This article belongs to the Special Issue Electrode Materials)
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16 pages, 6402 KiB  
Article
Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study
by Xiangfei Kong, Yuliang Zhong, Xian Rong, Chunhua Min and Chengying Qi
Materials 2016, 9(2), 70; https://doi.org/10.3390/ma9020070 - 25 Jan 2016
Cited by 57 | Viewed by 8101
Abstract
This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film [...] Read more.
This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency. Full article
(This article belongs to the Special Issue Development and Characterisation of Encapsulated PCM: Nano-, Micro-, and Macro-Encapsulation)
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30 pages, 15542 KiB  
Review
Numerical Characterization of Piezoceramics Using Resonance Curves
by Nicolás Pérez, Flávio Buiochi, Marco Aurélio Brizzotti Andrade and Julio Cezar Adamowski
Materials 2016, 9(2), 71; https://doi.org/10.3390/ma9020071 - 27 Jan 2016
Cited by 47 | Viewed by 8620
Abstract
Piezoelectric materials characterization is a challenging problem involving physical concepts, electrical and mechanical measurements and numerical optimization techniques. Piezoelectric ceramics such as Lead Zirconate Titanate (PZT) belong to the 6 mm symmetry class, which requires five elastic, three piezoelectric and two dielectric constants [...] Read more.
Piezoelectric materials characterization is a challenging problem involving physical concepts, electrical and mechanical measurements and numerical optimization techniques. Piezoelectric ceramics such as Lead Zirconate Titanate (PZT) belong to the 6 mm symmetry class, which requires five elastic, three piezoelectric and two dielectric constants to fully represent the material properties. If losses are considered, the material properties can be represented by complex numbers. In this case, 20 independent material constants are required to obtain the full model. Several numerical methods have been used to adjust the theoretical models to the experimental results. The continuous improvement of the computer processing ability has allowed the use of a specific numerical method, the Finite Element Method (FEM), to iteratively solve the problem of finding the piezoelectric constants. This review presents the recent advances in the numerical characterization of 6 mm piezoelectric materials from experimental electrical impedance curves. The basic strategy consists in measuring the electrical impedance curve of a piezoelectric disk, and then combining the Finite Element Method with an iterative algorithm to find a set of material properties that minimizes the difference between the numerical impedance curve and the experimental one. Different methods to validate the results are also discussed. Examples of characterization of some common piezoelectric ceramics are presented to show the practical application of the described methods. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
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18 pages, 5957 KiB  
Article
Revisiting the Characterization of the Losses in Piezoelectric Materials from Impedance Spectroscopy at Resonance
by Amador M. González, Álvaro García, César Benavente-Peces and Lorena Pardo
Materials 2016, 9(2), 72; https://doi.org/10.3390/ma9020072 - 26 Jan 2016
Cited by 42 | Viewed by 7474
Abstract
Electronic devices using the piezoelectric effect contain piezoelectric materials: often crystals, but in many cases poled ferroelectric ceramics (piezoceramics), polymers or composites. On the one hand, these materials exhibit non-negligible losses, not only dielectric, but also mechanical and piezoelectric. In this work, we [...] Read more.
Electronic devices using the piezoelectric effect contain piezoelectric materials: often crystals, but in many cases poled ferroelectric ceramics (piezoceramics), polymers or composites. On the one hand, these materials exhibit non-negligible losses, not only dielectric, but also mechanical and piezoelectric. In this work, we made simulations of the effect of the three types of losses in piezoelectric materials on the impedance spectrum at the resonance. We analyze independently each type of loss and show the differences among them. On the other hand, electrical and electronic engineers include piezoelectric sensors in electrical circuits to build devices and need electrical models of the sensor element. Frequently, material scientists and engineers use different languages, and the characteristic material coefficients do not have a straightforward translation to those specific electrical circuit components. To connect both fields of study, we propose the use of accurate methods of characterization from impedance measurements at electromechanical resonance that lead to determination of all types of losses, as an alternative to current standards. We introduce a simplified equivalent circuit model with electrical parameters that account for piezoceramic losses needed for the modeling and design of industrial applications. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
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21 pages, 1309 KiB  
Review
Potential of Electrospun Nanofibers for Biomedical and Dental Applications
by Muhammad Zafar, Shariq Najeeb, Zohaib Khurshid, Masoud Vazirzadeh, Sana Zohaib, Bilal Najeeb and Farshid Sefat
Materials 2016, 9(2), 73; https://doi.org/10.3390/ma9020073 - 26 Jan 2016
Cited by 203 | Viewed by 17829
Abstract
Electrospinning is a versatile technique that has gained popularity for various biomedical applications in recent years. Electrospinning is being used for fabricating nanofibers for various biomedical and dental applications such as tooth regeneration, wound healing and prevention of dental caries. Electrospun materials have [...] Read more.
Electrospinning is a versatile technique that has gained popularity for various biomedical applications in recent years. Electrospinning is being used for fabricating nanofibers for various biomedical and dental applications such as tooth regeneration, wound healing and prevention of dental caries. Electrospun materials have the benefits of unique properties for instance, high surface area to volume ratio, enhanced cellular interactions, protein absorption to facilitate binding sites for cell receptors. Extensive research has been conducted to explore the potential of electrospun nanofibers for repair and regeneration of various dental and oral tissues including dental pulp, dentin, periodontal tissues, oral mucosa and skeletal tissues. However, there are a few limitations of electrospinning hindering the progress of these materials to practical or clinical applications. In terms of biomaterials aspects, the better understanding of controlled fabrication, properties and functioning of electrospun materials is required to overcome the limitations. More in vivo studies are definitely required to evaluate the biocompatibility of electrospun scaffolds. Furthermore, mechanical properties of such scaffolds should be enhanced so that they resist mechanical stresses during tissue regeneration applications. The objective of this article is to review the current progress of electrospun nanofibers for biomedical and dental applications. In addition, various aspects of electrospun materials in relation to potential dental applications have been discussed. Full article
(This article belongs to the Special Issue Electrospun Materials)
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19 pages, 3810 KiB  
Article
Properties of Non-Structural Concrete Made with Mixed Recycled Aggregates and Low Cement Content
by Antonio López-Uceda, Jesús Ayuso, Martin López, José Ramón Jimenez, Francisco Agrela and María José Sierra
Materials 2016, 9(2), 74; https://doi.org/10.3390/ma9020074 - 26 Jan 2016
Cited by 37 | Viewed by 6023
Abstract
In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could be a suitable raw material for concrete manufacturing. The aims of this research were as follows: (i) to analyze the effect of the replacement ratio of natural coarse [...] Read more.
In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could be a suitable raw material for concrete manufacturing. The aims of this research were as follows: (i) to analyze the effect of the replacement ratio of natural coarse aggregates with MRA, the amount of ceramic particles in MRA, and the amount of cement, on the mechanical and physical properties of a non-structural concrete made with a low cement content; and (ii) to verify if it is possible to achieve a low-strength concrete that replaces a greater amount of natural aggregate with MRA and that has a low cement content. Two series of concrete mixes were manufactured using 180 and 200 kg/m3 of CEM II/A-V 42.5 R type Portland cement. Each series included seven concrete mixes: one with natural aggregates; two MRA with different ceramic particle contents; and one for each coarse aggregate replacement ratio (20%, 40%, and 100%). To study their properties, compressive and splitting tensile strength, modulus of elasticity, density, porosity, water penetration, and sorptivity, tests were performed. The results confirmed that the main factors affecting the properties analyzed in this research are the amount of cement and the replacement ratio; the two MRAs used in this work presented a similar influence on the properties. A non-structural, low-strength concrete (15 MPa) with an MRA replacement ratio of up to 100% for 200 kg/m3 of cement was obtained. This type of concrete could be applied in the construction of ditches, sidewalks, and other similar civil works. Full article
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11 pages, 2799 KiB  
Article
Electrochemical Properties of LLTO/Fluoropolymer-Shell Cellulose-Core Fibrous Membrane for Separator of High Performance Lithium-Ion Battery
by Fenglin Huang, Wenting Liu, Peiying Li, Jinxia Ning and Qufu Wei
Materials 2016, 9(2), 75; https://doi.org/10.3390/ma9020075 - 26 Jan 2016
Cited by 28 | Viewed by 7729
Abstract
A superfine Li0.33La0.557TiO3 (LLTO, 69.4 nm) was successfully synthesized by a facile solvent-thermal method to enhance the electrochemical properties of the lithium-ion battery separator. Co-axial nanofiber of cellulose and Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was prepared by a [...] Read more.
A superfine Li0.33La0.557TiO3 (LLTO, 69.4 nm) was successfully synthesized by a facile solvent-thermal method to enhance the electrochemical properties of the lithium-ion battery separator. Co-axial nanofiber of cellulose and Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was prepared by a co-axial electrospinning technique, in which the shell material was PVDF-HFP and the core was cellulose. LLTO superfine nanoparticles were incorporated into the shell of the PVDF-HFP. The core–shell composite nanofibrous membrane showed good wettability (16.5°, contact angle), high porosity (69.77%), and super electrolyte compatibility (497%, electrolyte uptake). It had a higher ionic conductivity (13.897 mS·cm−1) than those of pure polymer fibrous membrane and commercial separator. In addition, the rate capability (155.56 mAh·g−1) was also superior to the compared separator. These excellent performances endowed LLTO composite nanofibrous membrane as a promising separator for high-performance lithium-ion batteries. Full article
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18 pages, 2062 KiB  
Article
Evaluation of Castor Oil Cake Starch and Recovered Glycerol and Development of “Green” Composites Based on Those with Plant Fibers
by José Luis Guimarães, Ana Cristina Trindade Cursino, Cyro Ketzer Saul, Maria Rita Sierrakowski, Luiz Pereira Ramos and Kestur Gundappa Satyanarayana
Materials 2016, 9(2), 76; https://doi.org/10.3390/ma9020076 - 27 Jan 2016
Cited by 23 | Viewed by 6309
Abstract
Continuous efforts are being made in some countries for the recovery of crude glycerin (RG/CG) and castor oil cake (COC), the two byproducts of biodiesel production. These are expected to help, not only in addressing environmental safety, but also in adding value to [...] Read more.
Continuous efforts are being made in some countries for the recovery of crude glycerin (RG/CG) and castor oil cake (COC), the two byproducts of biodiesel production. These are expected to help, not only in addressing environmental safety, but also in adding value to those byproducts, which otherwise may go to waste. Finding ways to utilize those byproducts underlines the main objective of this study. This paper presents the evaluation of (i) COC, glycerin and banana and sugarcane fibers for moisture content; (ii) COC for structural and thermal properties; and (iii) CG for its chemical characteristics. The possibility of using COC and CG with the selected fibers as reinforcement in the development of bio-composites is attempted through thermo-molding. Results revealed enhanced mechanical properties for these composites. The obtained results are discussed in terms of the observed morphology. Full article
(This article belongs to the Special Issue Green Composites)
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14 pages, 9595 KiB  
Article
Deep Drawing of High-Strength Tailored Blanks by Using Tailored Tools
by Thomas Mennecart, Hamad Ul Hassan, Alper Güner, Noomane Ben Khalifa and Mohamad Hosseini
Materials 2016, 9(2), 77; https://doi.org/10.3390/ma9020077 - 27 Jan 2016
Cited by 6 | Viewed by 7715
Abstract
In most forming processes based on tailored blanks, the tool material remains the same as that of sheet metal blanks without tailored properties. A novel concept of lightweight construction for deep drawing tools is presented in this work to improve the forming behavior [...] Read more.
In most forming processes based on tailored blanks, the tool material remains the same as that of sheet metal blanks without tailored properties. A novel concept of lightweight construction for deep drawing tools is presented in this work to improve the forming behavior of tailored blanks. The investigations presented here deal with the forming of tailored blanks of dissimilar strengths using tailored dies made of two different materials. In the area of the steel blank with higher strength, typical tool steel is used. In the area of the low-strength steel, a hybrid tool made out of a polymer and a fiber-reinforced surface replaces the steel half. Cylindrical cups of DP600/HX300LAD are formed and analyzed regarding their formability. The use of two different halves of tool materials shows improved blank thickness distribution, weld-line movement and pressure distribution compared to the use of two steel halves. An improvement in strain distribution is also observed by the inclusion of springs in the polymer side of tools, which is implemented to control the material flow in the die. Furthermore, a reduction in tool weight of approximately 75% can be achieved by using this technique. An accurate finite element modeling strategy is developed to analyze the problem numerically and is verified experimentally for the cylindrical cup. This strategy is then applied to investigate the thickness distribution and weld-line movement for a complex geometry, and its transferability is validated. The inclusion of springs in the hybrid tool leads to better material flow, which results in reduction of weld-line movement by around 60%, leading to more uniform thickness distribution. Full article
(This article belongs to the Special Issue Forming of Light Weight Materials)
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17 pages, 5040 KiB  
Article
Metallurgical Parameters Controlling the Eutectic Silicon Charateristics in Be-Treated Al-Si-Mg Alloys
by Mohamed F. Ibrahim, Emad M. Elgallad, Salvador Valtierra, Herbert W. Doty and Fawzy H. Samuel
Materials 2016, 9(2), 78; https://doi.org/10.3390/ma9020078 - 27 Jan 2016
Cited by 23 | Viewed by 7289
Abstract
The present work was carried out on Al-7%Si-0.4%Mg-X alloy (where X = Mg, Fe, Sr or Be), where the effect of solidification rate on the eutectic silicon characteristics was investigated. Two solidification rates corresponding to dendrite arm spacings (DAS) of 24 and 65 [...] Read more.
The present work was carried out on Al-7%Si-0.4%Mg-X alloy (where X = Mg, Fe, Sr or Be), where the effect of solidification rate on the eutectic silicon characteristics was investigated. Two solidification rates corresponding to dendrite arm spacings (DAS) of 24 and 65 μm were employed. Samples with 24 μm DAS were solution heat-treated at 540 °C for 5 and 12 h prior to quenching in warm water at 65 °C. Eutectic Si particle charateristics were measured using an image analyzer. The results show that the addition of 0.05% Be leads to partial modification of the Si particles. Full modification was only obtained when Sr was added in an amount of 150–200 ppm, depending on the applied solidification rate. Increasing the amount of Mg to 0.8% in Sr-modified alloys leads to a reduction in the effectiveness of Sr as the main modifier. Similar observations were made when the Fe content was increased in Be-treated alloys due to the Be-Fe interaction. Over-modification results in the precipitation of hard Sr-rich particles, mainly Al4SrSi2, whereas overheating causes incipient melting of the Al-Cu eutectic and hence the surrounding matrix. Both factors lead to a deterioration in the alloy mechanical properties. Furthermore, the presence of long, acicular Si particles accelerates the occurrence of fracture and, as a result, yields poor ductility. In low iron (less than 0.1 wt%) Al-Si-Mg alloys, the mechanical properties in the as cast, as well as heat treated conditions, are mainly controlled by the eutectic Si charatersitics. Increasing the iron content and, hence, the volume fraction of Fe-based intermetallics leads to a complex fracture mode. Full article
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34 pages, 4792 KiB  
Review
Composite and Nanocomposite Metal Foams
by Isabel Duarte and José M. F. Ferreira
Materials 2016, 9(2), 79; https://doi.org/10.3390/ma9020079 - 28 Jan 2016
Cited by 126 | Viewed by 13742
Abstract
Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell [...] Read more.
Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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16 pages, 3905 KiB  
Article
Effect of Gum Arabic karroo as a Water-Reducing Admixture in Concrete
by Rose Mbugua, Ramadhan Salim and Julius Ndambuki
Materials 2016, 9(2), 80; https://doi.org/10.3390/ma9020080 - 28 Jan 2016
Cited by 29 | Viewed by 6640
Abstract
Concrete is one of the most popular construction materials in the world. Chemical admixtures are ingredients added to concrete to enhance its properties. However, most chemical admixtures on the market today are expensive, thereby making them out of reach for small consumers of [...] Read more.
Concrete is one of the most popular construction materials in the world. Chemical admixtures are ingredients added to concrete to enhance its properties. However, most chemical admixtures on the market today are expensive, thereby making them out of reach for small consumers of concrete. In Africa, use of chemical admixtures is rare despite the harsh weather conditions. In the current study, Gum from Acacia karroo (GAK) was used as a water-reducing admixture in concrete. A slump test, density and compressive strength were studied using different dosages of GAK while neat concrete was the control. Results showed that slump increased by 200% at a 2% dosage of GAK. This enabled reduction of water-to-binder (w/b) ratio from 0.61 to 0.48 for samples with a 3% dosage. Reduction in w/b resulted in increased compressive strength of 37.03% above the control after 180 days of curing for a 3% dosage. XRD studies also showed a decreased rate of hydration in the presence of GAK in concrete. It was concluded that GAK can be used in concrete as a water-reducing admixture, which is environmentally-friendly, thus producing sustainable and greener concrete. Full article
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8 pages, 2847 KiB  
Article
Validation of Parmigiano Reggiano Cheese Aroma Authenticity, Categorized through the Use of an Array of Semiconductors Nanowire Device (S3)
by Veronica Sberveglieri
Materials 2016, 9(2), 81; https://doi.org/10.3390/ma9020081 - 28 Jan 2016
Cited by 16 | Viewed by 4984
Abstract
Parmigiano Reggiano (PR) cheese is one of the most important Italian Protected Designation of Origin (PDO) cheeses and it is exported worldwide. As a PDO, the product is supposed to have distinctive sensory characteristics. In this work we present the use of the [...] Read more.
Parmigiano Reggiano (PR) cheese is one of the most important Italian Protected Designation of Origin (PDO) cheeses and it is exported worldwide. As a PDO, the product is supposed to have distinctive sensory characteristics. In this work we present the use of the Small Gas Sensor System (S3) device for the identification of specific PR markers, as compared to classical chemical techniques, such as Gas chromatography–mass spectrometry solid-phase microextraction (SPME-GC-MS). Markers are used to determine the percent of grated pulp and rind commercially utilized. The S3 device is equipped with an array of six metal oxide semiconductor (MOX) gas sensors, three of them with a nanowire (NW) morphology and the other three in the form of thin films. PDO can cover grated PR cheese as well, but only if made with whole cheese. Grated PR cheese must be characterized by the absence of additives and no more than 18% crust. The achieved results strongly encourage the use of S3 for a rapid identification of the percentage of grated PR. Full article
(This article belongs to the Special Issue Nanostructured Materials for Chemical Sensing Applications)
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17 pages, 3534 KiB  
Article
Hybrid ABC Optimized MARS-Based Modeling of the Milling Tool Wear from Milling Run Experimental Data
by Paulino José García Nieto, Esperanza García-Gonzalo, Celestino Ordóñez Galán and Antonio Bernardo Sánchez
Materials 2016, 9(2), 82; https://doi.org/10.3390/ma9020082 - 28 Jan 2016
Cited by 12 | Viewed by 5569
Abstract
Milling cutters are important cutting tools used in milling machines to perform milling operations, which are prone to wear and subsequent failure. In this paper, a practical new hybrid model to predict the milling tool wear in a regular cut, as well as [...] Read more.
Milling cutters are important cutting tools used in milling machines to perform milling operations, which are prone to wear and subsequent failure. In this paper, a practical new hybrid model to predict the milling tool wear in a regular cut, as well as entry cut and exit cut, of a milling tool is proposed. The model was based on the optimization tool termed artificial bee colony (ABC) in combination with multivariate adaptive regression splines (MARS) technique. This optimization mechanism involved the parameter setting in the MARS training procedure, which significantly influences the regression accuracy. Therefore, an ABC–MARS-based model was successfully used here to predict the milling tool flank wear (output variable) as a function of the following input variables: the time duration of experiment, depth of cut, feed, type of material, etc. Regression with optimal hyperparameters was performed and a determination coefficient of 0.94 was obtained. The ABC–MARS-based model's goodness of fit to experimental data confirmed the good performance of this model. This new model also allowed us to ascertain the most influential parameters on the milling tool flank wear with a view to proposing milling machine's improvements. Finally, conclusions of this study are exposed. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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14 pages, 1263 KiB  
Article
Flexural Strength of Preheated Resin Composites and Bonding Properties to Glass-Ceramic and Dentin
by Matthias Richard Kramer, Daniel Edelhoff and Bogna Stawarczyk
Materials 2016, 9(2), 83; https://doi.org/10.3390/ma9020083 - 29 Jan 2016
Cited by 18 | Viewed by 6060
Abstract
To test the impact of preheating (25, 37, 54, or 68 °C) of TetricEvoCeram (TEC), FiltekSupremeXT (FSXT), and Venus (V) on flexural strength (FS), shear bond strength (SBS) and interfacial tension (IFT). FS was tested with TEC and FSXT. For SBS, glass-ceramic and [...] Read more.
To test the impact of preheating (25, 37, 54, or 68 °C) of TetricEvoCeram (TEC), FiltekSupremeXT (FSXT), and Venus (V) on flexural strength (FS), shear bond strength (SBS) and interfacial tension (IFT). FS was tested with TEC and FSXT. For SBS, glass-ceramic and human dentin substrate were fabricated and luted with the preheated resin composite (RC). SBSs of 1500 thermal cycled specimens were measured. For IFT, glass slides covered with the non-polymerized RC were prepared and contact angles were measured. Data were analyzed using 2/1-way ANOVA with Scheffé-test, and t-test (p < 0.05). Preheated TEC (37–68 °C) showed higher FS compared to the control-group (25 °C) (p < 0.001). FSXT presented higher FS than TEC (p < 0.001). For SBS to dentin higher values for FSXT than TEC were found. The preheating temperature showed no impact on SBS to dentin. SBS to glass-ceramic revealed a positive influence of temperature for TEC 25–68 °C (p = 0.015). TEC showed higher values than V and FSXT (p < 0.001). IFT values increased with the preheating temperature. A significant difference could be observed in every RC group between 25 and 68 °C (p < 0.001). Full article
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11 pages, 1664 KiB  
Article
Effects on the Physical and Mechanical Properties of Porous Concrete for Plant Growth of Blast Furnace Slag, Natural Jute Fiber, and Styrene Butadiene Latex Using a Dry Mixing Manufacturing Process
by Hwang-Hee Kim, Chun-Soo Kim, Ji-Hong Jeon and Chan-Gi Park
Materials 2016, 9(2), 84; https://doi.org/10.3390/ma9020084 - 29 Jan 2016
Cited by 41 | Viewed by 6418
Abstract
To evaluate the effects of industrial by-products materials on the performance of porous concrete for plant growth, this study investigated the physical, strength, and freeze/thaw resistances of porous concrete for plant growth, prepared by replacing cement with blast furnace slag powder at 60% [...] Read more.
To evaluate the effects of industrial by-products materials on the performance of porous concrete for plant growth, this study investigated the physical, strength, and freeze/thaw resistances of porous concrete for plant growth, prepared by replacing cement with blast furnace slag powder at 60% by weight, and replacing natural stone aggregates with coarse blast furnace slag aggregates at rates of 0%, 20%, 40%, 60% and 100% by weight. In addition, the effects of adding natural jute fiber and styrene butadiene (SB) latex to these concrete mixtures were evaluated. The void ratio, compressive strength, and freeze/thaw resistance of the samples were measured. With increasing replacement rate of blast furnace aggregates, addition of latex, and mixing of natural jute fiber the void ratio of the concrete was increased. Compressive strength decreased as the replacement rate of blast-furnace slag aggregates increased. The compressive strength decreased after 100 freeze/thaw cycles, regardless of the replacement rate of blast furnace slag aggregates or of the addition of natural jute fiber and latex. The addition of natural jute fiber and latex decreased the compressive strength after 100 freeze/thaw cycles. The test results indicate that the control mixture satisfied the target compressive strength of 10 MPa and the target void ratio of 25% at replacement rates of 0% and 20% for blast furnace aggregates, and that the mixtures containing latex satisfied the criteria up to an aggregate replacement rate of 60%. However, the mixtures containing natural jute fiber did not satisfy these criteria. The relationship between void ratio and residual compressive strength after 100 freeze/thaw cycles indicates that the control mixture and the mixtures containing jute fiber at aggregate replacement rates of 20% and 40% satisfied the target void ratio of 25% and the target residual compressive strength of over 80% after 100 freeze/thaw cycles. The mixtures containing latex and aggregate replacement rates up to 60% satisfied the target void ratio and compressive strength. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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27 pages, 15618 KiB  
Review
Commercial Applications of Metal Foams: Their Properties and Production
by Francisco García-Moreno
Materials 2016, 9(2), 85; https://doi.org/10.3390/ma9020085 - 29 Jan 2016
Cited by 455 | Viewed by 33509
Abstract
This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also [...] Read more.
This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also taking into account costs and feasibility considerations. These properties are the motivation and basis of related applications. Finally, a summary of the most relevant applications showing a large number of actual examples is presented. Concluding, we can forecast a slow, but continuous growth of this industrial sector. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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19 pages, 7635 KiB  
Article
Uniaxial Compressive Constitutive Relationship of Concrete Confined by Special-Shaped Steel Tube Coupled with Multiple Cavities
by Haipeng Wu, Wanlin Cao, Qiyun Qiao and Hongying Dong
Materials 2016, 9(2), 86; https://doi.org/10.3390/ma9020086 - 29 Jan 2016
Cited by 16 | Viewed by 5298
Abstract
A method is presented to predict the complete stress-strain curves of concrete subjected to triaxial stresses, which were caused by axial load and lateral force. The stress can be induced due to the confinement action inside a special-shaped steel tube having multiple cavities. [...] Read more.
A method is presented to predict the complete stress-strain curves of concrete subjected to triaxial stresses, which were caused by axial load and lateral force. The stress can be induced due to the confinement action inside a special-shaped steel tube having multiple cavities. The existing reinforced confined concrete formulas have been improved to determine the confinement action. The influence of cross-sectional shape, of cavity construction, of stiffening ribs and of reinforcement in cavities has been considered in the model. The parameters of the model are determined on the basis of experimental results of an axial compression test for two different kinds of special-shaped concrete filled steel tube (CFT) columns with multiple cavities. The complete load-strain curves of the special-shaped CFT columns are estimated. The predicted concrete strength and the post-peak behavior are found to show good agreement within the accepted limits, compared with the experimental results. In addition, the parameters of proposed model are taken from two kinds of totally different CFT columns, so that it can be concluded that this model is also applicable to concrete confined by other special-shaped steel tubes. Full article
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16 pages, 3394 KiB  
Article
Cu-Doped ZnO Thin Films Deposited by a Sol-Gel Process Using Two Copper Precursors: Gas-Sensing Performance in a Propane Atmosphere
by Heberto Gómez-Pozos, Emma Julia Luna Arredondo, Arturo Maldonado Álvarez, Rajesh Biswal, Yuriy Kudriavtsev, Jaime Vega Pérez, Yenny Lucero Casallas-Moreno and María De la Luz Olvera Amador
Materials 2016, 9(2), 87; https://doi.org/10.3390/ma9020087 - 29 Jan 2016
Cited by 33 | Viewed by 7874
Abstract
A study on the propane gas-sensing properties of Cu-doped ZnO thin films is presented in this work. The films were deposited on glass substrates by sol-gel and dip coating methods, using zinc acetate as a zinc precursor, copper acetate and copper chloride as [...] Read more.
A study on the propane gas-sensing properties of Cu-doped ZnO thin films is presented in this work. The films were deposited on glass substrates by sol-gel and dip coating methods, using zinc acetate as a zinc precursor, copper acetate and copper chloride as precursors for doping. For higher sensitivity values, two film thickness values are controlled by the six and eight dippings, whereas for doping, three dippings were used, irrespective of the Cu precursor. The film structure was analyzed by X-ray diffractometry, and the analysis of the surface morphology and film composition was made through scanning electron microscopy (SEM) and secondary ion mass spectroscopy (SIMS), respectively. The sensing properties of Cu-doped ZnO thin films were then characterized in a propane atmosphere, C3H8, at different concentration levels and different operation temperatures of 100, 200 and 300 °C. Cu-doped ZnO films doped with copper chloride presented the highest sensitivity of approximately 6 × 104, confirming a strong dependence on the dopant precursor type. The results obtained in this work show that the use of Cu as a dopant in ZnO films processed by sol-gel produces excellent catalysts for sensing C3H8 gas. Full article
(This article belongs to the Special Issue Nanostructured Materials for Chemical Sensing Applications)
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14 pages, 4293 KiB  
Article
Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al–5Mg–Mn Alloys Solidified Under Near-Rapid Cooling
by Yulin Liu, Gaoren Huang, Yimeng Sun, Li Zhang, Zhenwei Huang, Jijie Wang and Chunzhong Liu
Materials 2016, 9(2), 88; https://doi.org/10.3390/ma9020088 - 29 Jan 2016
Cited by 56 | Viewed by 7796
Abstract
Mn was an important alloying element used in Al–Mg–Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was [...] Read more.
Mn was an important alloying element used in Al–Mg–Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al–5Mg–Mn alloy with low Fe content (<0.1 wt %), intermetallic Al6(Fe,Mn) was small in size and amount. With increasing Mn content, intermetallic Al6(Fe,Mn) increased, but in limited amount. In high-Fe-containing Al–5Mg–Mn alloys (0.5 wt % Fe), intermetallic Al6(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al6(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al6(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al6(Fe,Mn) to become the primary phase at a lower Mn content. Full article
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13 pages, 1581 KiB  
Article
Experimental and Statistical Evaluation of the Size Effect on the Bending Strength of Dimension Lumber of Northeast China Larch
by Yong Zhong, Hai-Qing Ren and Ze-Hui Jiang
Materials 2016, 9(2), 89; https://doi.org/10.3390/ma9020089 - 30 Jan 2016
Cited by 11 | Viewed by 4648
Abstract
This study investigated the size effect on the bending strength (modulus of rupture—MOR) of dimension lumber of Northeast China larch (Larix gmelinii); providing a basis for the further application in light wood frame construction. Experimental and statistical evaluations were conducted on [...] Read more.
This study investigated the size effect on the bending strength (modulus of rupture—MOR) of dimension lumber of Northeast China larch (Larix gmelinii); providing a basis for the further application in light wood frame construction. Experimental and statistical evaluations were conducted on the bending strength. A total of 2409 full-size dimension lumber samples were tested by static bending tests; which included three different sizes: 2 × 3; 2 × 4; and 2 × 6. Results indicate that the size has a significant effect on the MOR. Both the chi-square (χ2) and Kolmogorov-Smirnov (K-S) test results show that the lognormal distribution generally fits to the MOR better than to the normal distribution. Additionally; the effects of partial safety factor (γR) and live-to-dead load ratio (ρ) were studied by reliability analysis. Reliability analysis results indicate that the reliability index increases nonlinearly with the decrease of γR and the rise of ρ. Finally; the design value of bending strength and its adjusting factor of size effect of 2 × 3; 2 × 4; and 2 × 6 larch dimension lumber were obtained according to the Chinese National Standards’ requirements of the reliability index. Full article
(This article belongs to the Special Issue Bio- and Natural-Fiber Composites)
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12 pages, 7355 KiB  
Article
Heterojunctions of p-BiOI Nanosheets/n-TiO2 Nanofibers: Preparation and Enhanced Visible-Light Photocatalytic Activity
by Kexin Wang, Changlu Shao, Xinghua Li, Fujun Miao, Na Lu and Yichun Liu
Materials 2016, 9(2), 90; https://doi.org/10.3390/ma9020090 - 30 Jan 2016
Cited by 40 | Viewed by 8501
Abstract
p-BiOI nanosheets/n-TiO2 nanofibers (p-BiOI/n-TiO2 NFs) have been facilely prepared via the electrospinning technique combining successive ionic layer adsorption and reaction (SILAR). Dense BiOI nanosheets with good crystalline and width about 500 nm were uniformly assembled on TiO2 nanofibers at room [...] Read more.
p-BiOI nanosheets/n-TiO2 nanofibers (p-BiOI/n-TiO2 NFs) have been facilely prepared via the electrospinning technique combining successive ionic layer adsorption and reaction (SILAR). Dense BiOI nanosheets with good crystalline and width about 500 nm were uniformly assembled on TiO2 nanofibers at room temperature. The amount of the heterojunctions and the specific surface area were well controlled by adjusting the SILAR cycles. Due to the synergistic effect of p-n heterojunctions and high specific surface area, the obtained p-BiOI/n-TiO2 NFs exhibited enhanced visible-light photocatalytic activity. Moreover, the p-BiOI/n-TiO2 NFs heterojunctions could be easily recycled without decreasing the photocatalytic activity owing to their one-dimensional nanofibrous structure. Based on the above, the heterojunctions of p-BiOI/n-TiO2 NFs may be promising visible-light-driven photocatalysts for converting solar energy to chemical energy in environment remediation. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)
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16 pages, 3289 KiB  
Article
Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete
by Antonio López-Uceda, Jesús Ayuso, José Ramón Jiménez, Francisco Agrela, Auxiliadora Barbudo and Jorge De Brito
Materials 2016, 9(2), 91; https://doi.org/10.3390/ma9020091 - 2 Feb 2016
Cited by 21 | Viewed by 5780
Abstract
This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures [...] Read more.
This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors’ knowledge, there have not been any upscaled applications of concrete with MRA and low cement content. Full article
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13 pages, 3329 KiB  
Article
Effect of Functionalization of Graphene Nanoplatelets on the Mechanical and Thermal Properties of Silicone Rubber Composites
by Guangwu Zhang, Fuzhong Wang, Jing Dai and Zhixiong Huang
Materials 2016, 9(2), 92; https://doi.org/10.3390/ma9020092 - 2 Feb 2016
Cited by 125 | Viewed by 10986
Abstract
This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized [...] Read more.
This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized GnPs were individually incorporated into the SR. Compared with the pristine GnP/SR composite, the composites reinforced with modified GnP showed better tensile strength, elongation at break, and thermal conductivity properties due to better dispersion of modified GnPs and stronger interfacial interactions between the modified GnPs and matrix. The mechanical properties and thermal conductivity of the VTMS-GnP/SR composite were comparable to the properties of the Triton-GnP counterpart, but better than that of the APTES-GnP/SR composite. In addition, the VTMS-GnP/SR composite demonstrated the highest thermal stability and crystallization temperature among the four types of composites. The remarkable improvement of mechanical and thermal properties of the VTMS-GnP/SR composite was mainly due to the covalent linkage of VTMS-GnP with SR. The VTMS treatment was a more appropriate modification of GnP particles to improve the multifunctional properties of SR. Full article
(This article belongs to the Section Advanced Composites)
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18 pages, 4347 KiB  
Article
Effects of Wet/Dry-Cycling and Plasma Treatments on the Properties of Flax Nonwovens Intended for Composite Reinforcing
by Heura Ventura, Josep Claramunt, Antonio Navarro, Miguel A. Rodriguez-Perez and Mònica Ardanuy
Materials 2016, 9(2), 93; https://doi.org/10.3390/ma9020093 - 3 Feb 2016
Cited by 19 | Viewed by 5837
Abstract
This research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments [...] Read more.
This research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments with air, argon and ethylene gases considering different conditions and combinations, which produce variation on the chemical surface composition of the NWs. The resulting changes in the chemical surface composition, wetting properties, thermal stability and mechanical properties were determined. Variations in surface morphology could be observed by scanning electron microscopy (SEM). The results of the X-ray photoelectron spectroscopy (XPS) showed significant changes to the surface chemistry for the samples treated with argon or air (with more content on polar groups on the surface) and ethylene plasma (with less content of polar groups). Although only slight differences were found in moisture regain and water retention values (WRV), significant changes were found on the contact angle values, thus revealing hydrophilicity for the air-treated and argon-treated samples and hydrophobicity for the ethylene-treated ones. Moreover, for some of the treatments the mechanical testing revealed an increase of the NW breaking force. Full article
(This article belongs to the Special Issue Green Composites)
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27 pages, 31328 KiB  
Review
How to Study Thermal Applications of Open-Cell Metal Foam: Experiments and Computational Fluid Dynamics
by Sven De Schampheleire, Peter De Jaeger, Kathleen De Kerpel, Bernd Ameel, Henk Huisseune and Michel De Paepe
Materials 2016, 9(2), 94; https://doi.org/10.3390/ma9020094 - 3 Feb 2016
Cited by 45 | Viewed by 12428
Abstract
This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most [...] Read more.
This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most studies only report the dependence of thermal properties on porosity and a number of pores per linear inch (PPI-value). A different approach, which is studied in this paper, is to characterize the foam using micro tomography scans with small voxel sizes. The results of these scans are compared to correlations from the open literature. Large differences are observed. For the numerical work, the focus is on studies using computational fluid dynamics. A novel way of determining the closure terms is proposed in this work. This is done through a numerical foam model based on micro tomography scan data. With this foam model, the closure terms are determined numerically. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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14 pages, 9155 KiB  
Article
Effect of H2S Plasma Treatment on the Surface Modification of a Polyethylene Terephthalate Surface
by Alenka Vesel, Janez Kovac, Gregor Primc, Ita Junkar and Miran Mozetic
Materials 2016, 9(2), 95; https://doi.org/10.3390/ma9020095 - 5 Feb 2016
Cited by 16 | Viewed by 6558
Abstract
H2S plasma created by an electrode-less radio-frequency discharge was used to modify the surface properties of the polymer polyethylene terephthalate. X-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy were used to determine the evolution of the surface functionalities [...] Read more.
H2S plasma created by an electrode-less radio-frequency discharge was used to modify the surface properties of the polymer polyethylene terephthalate. X-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy were used to determine the evolution of the surface functionalities and morphology. A very thin film of chemically bonded sulfur formed on the surface within the first 10 s of treatment, whereas treatment for more than 20 s caused deposition of higher quantities of unbonded sulfur. The sulfur concentration reached a maximum of between 40 and 80 s of plasma treatment; at longer treatment times, the unbonded sulfur vanished, indicating instability of the deposited sulfur layer. Large differences in the surface morphology were observed. Full article
(This article belongs to the Section Biomaterials)
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13 pages, 4294 KiB  
Article
Multi-Material Front Contact for 19% Thin Film Solar Cells
by Joop Van Deelen, Yasemin Tezsevin and Marco Barink
Materials 2016, 9(2), 96; https://doi.org/10.3390/ma9020096 - 6 Feb 2016
Cited by 7 | Viewed by 8076
Abstract
The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, [...] Read more.
The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing Cu(In,Ga)Se2 (CIGS), CdTe and high band gap perovskites. Supplementing the metal oxide with a metallic copper grid improves the performance of the front contact and aims to increase the efficiency. Various front contact designs with and without a metallic finger grid were calculated with a variation of the transparent conductive oxide (TCO) sheet resistance, scribing area, cell length, and finger dimensions. In addition, the contact resistance and illumination power were also assessed and the optimal thin film solar panel design was determined. Adding a metallic finger grid on a TCO gives a higher solar cell efficiency and this also enables longer cell lengths. However, contact resistance between the metal and the TCO material can reduce the efficiency benefit somewhat. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)
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8 pages, 2366 KiB  
Article
Bone Regeneration Using a Mixture of Silicon-Substituted Coral HA and β-TCP in a Rat Calvarial Bone Defect Model
by Jiyeon Roh, Ji-Youn Kim, Young-Muk Choi, Seong-Min Ha, Kyoung-Nam Kim and Kwang-Mahn Kim
Materials 2016, 9(2), 97; https://doi.org/10.3390/ma9020097 - 6 Feb 2016
Cited by 14 | Viewed by 6151
Abstract
The demand of bone graft materials has been increasing. Among various origins of bone graft materials, natural coral composed of up to 99% calcium carbonate was chosen and converted into hydroxyapatite (HA); silicon was then substituted into the HA. Then, the Si-HA was [...] Read more.
The demand of bone graft materials has been increasing. Among various origins of bone graft materials, natural coral composed of up to 99% calcium carbonate was chosen and converted into hydroxyapatite (HA); silicon was then substituted into the HA. Then, the Si-HA was mixed with β-tricalcium phosphate (TCP) in the ratios 100:0 (S100T0), 70:30 (S70T30), 60:40 (S60T40), and 50:50 (S50T50). The materials were implanted for four and eight weeks in a rat calvarial bone defect model (8 mm). The MBCPTM (HA:β-TCP = 60:40, Biomatalante, Vigneux de Bretagne, France) was used as a control. After euthanasia, the bone tissue was analyzed by making histological slides. From the results, S60T40 showed the fastest bone regeneration in four weeks (p < 0.05). In addition, S60T40, S50T50, and MBCPTM showed significant new bone formation in eight weeks (p < 0.05). In conclusion, Si-HA/TCP showed potential as a bone graft material. Full article
(This article belongs to the Section Biomaterials)
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26 pages, 11620 KiB  
Article
Increased Durability of Concrete Made with Fine Recycled Concrete Aggregates Using Superplasticizers
by Francisco Cartuxo, Jorge De Brito, Luis Evangelista, José Ramón Jiménez and Enrique F. Ledesma
Materials 2016, 9(2), 98; https://doi.org/10.3390/ma9020098 - 8 Feb 2016
Cited by 94 | Viewed by 8535
Abstract
This paper evaluates the influence of two superplasticizers (SP) on the durability properties of concrete made with fine recycled concrete aggregate (FRCA). For this purpose, three families of concrete were tested: concrete without SP, concrete made with a regular superplasticizer and concrete made [...] Read more.
This paper evaluates the influence of two superplasticizers (SP) on the durability properties of concrete made with fine recycled concrete aggregate (FRCA). For this purpose, three families of concrete were tested: concrete without SP, concrete made with a regular superplasticizer and concrete made with a high-performance superplasticizer. Five volumetric replacement ratios of natural sand by FRCA were tested: 0%, 10%, 30%, 50% and 100%. Two natural gravels were used as coarse aggregates. All mixes had the same particle size distribution, cement content and amount of superplasticizer. The w/c ratio was calibrated to obtain similar slump. The results showed that the incorporation of FRCA increased the water absorption by immersion, the water absorption by capillary action, the carbonation depth and the chloride migration coefficient, while the use of superplasticizers highly improved these properties. The incorporation of FRCA jeopardized the SP’s effectiveness. This research demonstrated that, from a durability point of view, the simultaneous incorporation of FRCA and high-performance SP is a viable sustainable solution for structural concrete production. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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12 pages, 1833 KiB  
Article
Investigation of Pozzolanic Reaction in Nanosilica-Cement Blended Pastes Based on Solid-State Kinetic Models and 29Si MAS NMR
by Jiho Moon, Mahmoud M. Reda Taha, Kwang-Soo Youm and Jung J. Kim
Materials 2016, 9(2), 99; https://doi.org/10.3390/ma9020099 - 6 Feb 2016
Cited by 37 | Viewed by 7668
Abstract
The incorporation of pozzolanic materials in concrete has many beneficial effects to enhance the mechanical properties of concrete. The calcium silicate hydrates in cement matrix of concrete increase by pozzolanic reaction of silicates and calcium hydroxide. The fine pozzolanic particles fill spaces between [...] Read more.
The incorporation of pozzolanic materials in concrete has many beneficial effects to enhance the mechanical properties of concrete. The calcium silicate hydrates in cement matrix of concrete increase by pozzolanic reaction of silicates and calcium hydroxide. The fine pozzolanic particles fill spaces between clinker grains, thereby resulting in a denser cement matrix and interfacial transition zone between cement matrix and aggregates; this lowers the permeability and increases the compressive strength of concrete. In this study, Ordinary Portland Cement (OPC) was mixed with 1% and 3% nanosilica by weight to produce cement pastes with water to binder ratio (w/b) of 0.45. The specimens were cured for 7 days. 29Si nuclear magnetic resonance (NMR) experiments are conducted and conversion fraction of nanosilica is extracted. The results are compared with a solid-state kinetic model. It seems that pozzolanic reaction of nanosilica depends on the concentration of calcium hydroxide. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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12 pages, 3876 KiB  
Communication
High Pressure Laminates with Antimicrobial Properties
by Sandra Magina, Mauro D. Santos, João Ferra, Paulo Cruz, Inês Portugal and Dmitry Evtuguin
Materials 2016, 9(2), 100; https://doi.org/10.3390/ma9020100 - 6 Feb 2016
Cited by 13 | Viewed by 9414
Abstract
High-pressure laminates (HPLs) are durable, resistant to environmental effects and good cost-benefit decorative surface composite materials with special properties tailored to meet market demand. In the present work, polyhexamethylene biguanide (PHMB) was incorporated for the first time into melamine-formaldehyde resin (MF) matrix on [...] Read more.
High-pressure laminates (HPLs) are durable, resistant to environmental effects and good cost-benefit decorative surface composite materials with special properties tailored to meet market demand. In the present work, polyhexamethylene biguanide (PHMB) was incorporated for the first time into melamine-formaldehyde resin (MF) matrix on the outer layer of HPLs to provide them antimicrobial properties. Chemical binding of PHMB to resin matrix was detected on the surface of produced HPLs by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Antimicrobial evaluation tests were carried out on the ensuing HPLs doped with PHMB against gram-positive Listeria innocua and gram-negative Escherichia coli bacteria. The results revealed that laminates prepared with 1.0 wt % PHMB in MF resin were bacteriostatic (i.e., inhibited the growth of microorganisms), whereas those prepared with 2.4 wt % PHMB in MF resin exhibited bactericidal activity (i.e., inactivated the inoculated microorganisms). The results herein reported disclose a promising strategy for the production of HPLs with antimicrobial activity without affecting basic intrinsic quality parameters of composite material. Full article
(This article belongs to the Special Issue Self-Cleaning and Antimicrobial Surfaces)
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9 pages, 4003 KiB  
Communication
Tungsten as a Chemically-Stable Electrode Material on Ga-Containing Piezoelectric Substrates Langasite and Catangasite for High-Temperature SAW Devices
by Gayatri K. Rane, Marietta Seifert, Siegfried Menzel, Thomas Gemming and Jürgen Eckert
Materials 2016, 9(2), 101; https://doi.org/10.3390/ma9020101 - 6 Feb 2016
Cited by 21 | Viewed by 5715
Abstract
Thin films of tungsten on piezoelectric substrates La3Ga5SiO14 (LGS) and Ca3TaGa3Si2O14 (CTGS) have been investigated as a potential new electrode material for interdigital transducers for surface acoustic wave-based sensor devices operating [...] Read more.
Thin films of tungsten on piezoelectric substrates La3Ga5SiO14 (LGS) and Ca3TaGa3Si2O14 (CTGS) have been investigated as a potential new electrode material for interdigital transducers for surface acoustic wave-based sensor devices operating at high temperatures up to 800 °C under vacuum conditions. Although LGS is considered to be suitable for high-temperature applications, it undergoes chemical and structural transformation upon vacuum annealing due to diffusion of gallium and oxygen. This can alter the device properties depending on the electrode nature, the annealing temperature, and the duration of the application. Our studies present evidence for the chemical stability of W on these substrates against the diffusion of Ga/O from the substrate into the film, even upon annealing up to 800 °C under vacuum conditions using Auger electron spectroscopy and energy-dispersive X-ray spectroscopy, along with local studies using transmission electron microscopy. Additionally, the use of CTGS as a more stable substrate for such applications is indicated. Full article
(This article belongs to the Section Advanced Composites)
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10 pages, 3541 KiB  
Article
Long-Term Progressive Degradation of the Biological Capability of Titanium
by Hajime Minamikawa, Wael Att, Takayuki Ikeda, Makoto Hirota and Takahiro Ogawa
Materials 2016, 9(2), 102; https://doi.org/10.3390/ma9020102 - 6 Feb 2016
Cited by 40 | Viewed by 5076
Abstract
Titanium undergoes time-dependent degradation in biological capability, or “biological aging”. It is unknown whether the biological aging of titanium occurs beyond four weeks and whether age-related changes are definitely associated with surface hydrophilicity. We therefore measured multiple biological parameters of bone marrow-derived osteoblasts [...] Read more.
Titanium undergoes time-dependent degradation in biological capability, or “biological aging”. It is unknown whether the biological aging of titanium occurs beyond four weeks and whether age-related changes are definitely associated with surface hydrophilicity. We therefore measured multiple biological parameters of bone marrow-derived osteoblasts cultured on newly prepared, one-month-old, three-month-old, and six-month-old acid-etched titanium surfaces, as well as the hydrophilicity of these surfaces. New surfaces were superhydrophilic with a contact angle of ddH2O of 0°, whereas old surfaces were all hydrophobic with the contact angle of around 90°. Cell attachment, cell spread, cell density, and alkaline phosphatase activity were highest on new surfaces and decreased in a time-dependent manner. These decreases persisted and remained significant for most of the biological parameters up to six-months. While the number of attached cells was negatively correlated with hydrophilicity, the other measured parameters were not. The biological capability of titanium continues to degrade up to six months of aging, but these effects are not directly associated with time-dependent reductions in hydrophilicity. A full understanding of the biological aging will help guide regulatory improvements in implant device manufacturing and develop countermeasures against this phenomenon in order to improve clinical outcomes. Full article
(This article belongs to the Section Biomaterials)
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12 pages, 2767 KiB  
Article
Dual Function Behavior of Carbon Fiber-Reinforced Polymer in Simulated Pore Solution
by Ji-Hua Zhu, Guanping Guo, Liangliang Wei, Miaochang Zhu and Xianchuan Chen
Materials 2016, 9(2), 103; https://doi.org/10.3390/ma9020103 - 6 Feb 2016
Cited by 22 | Viewed by 6251
Abstract
The mechanical and electrochemical performance of carbon fiber-reinforced polymer (CFRP) were investigated regarding a novel improvement in the load-carrying capacity and durability of reinforced concrete structures by adopting CFRP as both a structural strengthener and an anode of the impressed current cathodic protection [...] Read more.
The mechanical and electrochemical performance of carbon fiber-reinforced polymer (CFRP) were investigated regarding a novel improvement in the load-carrying capacity and durability of reinforced concrete structures by adopting CFRP as both a structural strengthener and an anode of the impressed current cathodic protection (ICCP) system. The mechanical and anode performance of CFRP were investigated in an aqueous pore solution in which the electrolytes were available to the anode in a cured concrete structure. Accelerated polarization tests were designed with different test durations and various levels of applied currents in accordance with the international standard. The CFRP specimens were mechanically characterized after polarization. The measured feeding voltage and potential during the test period indicates CFRP have stable anode performance in a simulated pore solution. Two failure modes were observed through tensile testing. The tensile properties of the post-polarization CFRP specimens declined with an increased charge density. The CFRP demonstrated success as a structural strengthener and ICCP anode. We propose a mathematic model predicting the tensile strengths of CFRP with varied impressed charge densities. Full article
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10 pages, 1284 KiB  
Article
Effect of Addition of Colloidal Silica to Films of Polyimide, Polyvinylpyridine, Polystyrene, and Polymethylmethacrylate Nano-Composites
by Soliman Abdalla, Fahad Al-Marzouki, Abdullah Obaid and Salah Gamal
Materials 2016, 9(2), 104; https://doi.org/10.3390/ma9020104 - 6 Feb 2016
Cited by 9 | Viewed by 5149
Abstract
Nano-composite films have been the subject of extensive work for developing the energy-storage efficiency of electrostatic capacitors. Factors such as polymer purity, nanoparticle size, and film morphology drastically affect the electrostatic efficiency of the dielectric material that forms the insulating film between the [...] Read more.
Nano-composite films have been the subject of extensive work for developing the energy-storage efficiency of electrostatic capacitors. Factors such as polymer purity, nanoparticle size, and film morphology drastically affect the electrostatic efficiency of the dielectric material that forms the insulating film between the conductive electrodes of a capacitor. This in turn affects the energy storage performance of the capacitor. In the present work, we have studied the dielectric properties of four highly pure amorphous polymer films: polymethyl methacrylate (PMMA), polystyrene, polyimide and poly-4-vinylpyridine. Comparison between the dielectric properties of these polymers has revealed that the higher breakdown performance is a character of polyimide (PI) and PMMA. Also, our experimental data shows that adding colloidal silica to PMMA and PI leads to a net decrease in the dielectric properties compared to the pure polymer. Full article
(This article belongs to the Section Advanced Composites)
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15 pages, 2715 KiB  
Review
Irradiation Induced Microstructure Evolution in Nanostructured Materials: A Review
by Wenbo Liu, Yanzhou Ji, Pengkang Tan, Hang Zang, Chaohui He, Di Yun, Chi Zhang and Zhigang Yang
Materials 2016, 9(2), 105; https://doi.org/10.3390/ma9020105 - 6 Feb 2016
Cited by 50 | Viewed by 8869
Abstract
Nanostructured (NS) materials may have different irradiation resistance from their coarse-grained (CG) counterparts. In this review, we focus on the effect of grain boundaries (GBs)/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void [...] Read more.
Nanostructured (NS) materials may have different irradiation resistance from their coarse-grained (CG) counterparts. In this review, we focus on the effect of grain boundaries (GBs)/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void denuded zones (VDZs) and the unusual behavior of void formation near GBs/interfaces in metals due to the interactions between GBs/interfaces and irradiation-produced point defects are systematically reviewed. Some experimental results and calculation results show that NS materials have enhanced irradiation resistance, due to their extremely small grain sizes and large volume fractions of GBs/interfaces, which could absorb and annihilate the mobile defects produced during irradiation. However, there is also literature reporting reduced irradiation resistance or even amorphization of NS materials at a lower irradiation dose compared with their bulk counterparts, since the GBs are also characterized by excess energy (compared to that of single crystal materials) which could provide a shift in the total free energy that will lead to the amorphization process. The competition of these two effects leads to the different irradiation tolerance of NS materials. The irradiation-induced grain growth is dominated by irradiation temperature, dose, ion flux, character of GBs/interface and nanoprecipitates, although the decrease of grain sizes under irradiation is also observed in some experiments. Full article
(This article belongs to the Special Issue Nuclear Materials 2015)
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15 pages, 6408 KiB  
Article
Fatigue of Ti6Al4V Structural Health Monitoring Systems Produced by Selective Laser Melting
by Maria Strantza, Reza Vafadari, Dieter De Baere, Bey Vrancken, Wim Van Paepegem, Isabelle Vandendael, Herman Terryn, Patrick Guillaume and Danny Van Hemelrijck
Materials 2016, 9(2), 106; https://doi.org/10.3390/ma9020106 - 11 Feb 2016
Cited by 35 | Viewed by 8896
Abstract
Selective laser melting (SLM) is an additive manufacturing (AM) process which is used for producing metallic components. Currently, the integrity of components produced by SLM is in need of improvement due to residual stresses and unknown fracture behavior. Titanium alloys produced by AM [...] Read more.
Selective laser melting (SLM) is an additive manufacturing (AM) process which is used for producing metallic components. Currently, the integrity of components produced by SLM is in need of improvement due to residual stresses and unknown fracture behavior. Titanium alloys produced by AM are capable candidates for applications in aerospace and industrial fields due to their fracture resistance, fatigue behavior and corrosion resistance. On the other hand, structural health monitoring (SHM) system technologies are promising and requested from the industry. SHM systems can monitor the integrity of a structure and during the last decades the research has primarily been influenced by bionic engineering. In that aspect a new philosophy for SHM has been developed: the so-called effective structural health monitoring (eSHM) system. The current system uses the design freedom provided by AM. The working principle of the system is based on crack detection by means of a network of capillaries that are integrated in a structure. The main objective of this research is to evaluate the functionality of Ti6Al4V produced by the SLM process in the novel SHM system and to confirm that the eSHM system can successfully detect cracks in SLM components. In this study four-point bending fatigue tests on Ti6Al4V SLM specimens with an integrated SHM system were conducted. Fractographic analysis was performed after the final failure, while finite element simulations were used in order to determine the stress distribution in the capillary region and on the component. It was proven that the SHM system does not influence the crack initiation behavior during fatigue. The results highlight the effectiveness of the eSHM on SLM components, which can potentially be used by industrial and aerospace applications. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
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19 pages, 3348 KiB  
Article
Synthesis, Characterization, Antimicrobial Studies and Corrosion Inhibition Potential of 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane: Experimental and Quantum Chemical Studies
by Henry U. Nwankwo, Collins N. Ateba, Lukman O. Olasunkanmi, Abolanle S. Adekunle, David A. Isabirye, Damian C. Onwudiwe and Eno E. Ebenso
Materials 2016, 9(2), 107; https://doi.org/10.3390/ma9020107 - 11 Feb 2016
Cited by 26 | Viewed by 7365
Abstract
The macrocylic ligand, 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane (MHACD) was synthesized by the demetallation of its freshly synthesized Ni(II) complex (NiMHACD). Successful synthesis of NiMHACD and the free ligand (MHACD) was confirmed by various characterization techniques, including Fourier transform infra-red (FT-IR), proton nuclear magnetic resonance (1 [...] Read more.
The macrocylic ligand, 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane (MHACD) was synthesized by the demetallation of its freshly synthesized Ni(II) complex (NiMHACD). Successful synthesis of NiMHACD and the free ligand (MHACD) was confirmed by various characterization techniques, including Fourier transform infra-red (FT-IR), proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), ultraviolet-visible (UV-vis), and energy dispersive x-ray (EDX) spectroscopic techniques. The anti-bacteria activities of MHACD were investigated against Staphylococcus aureus and Enterococcus species and the results showed that MHACD possesses a spectrum of activity against the two bacteria. The electrochemical cyclic voltammetry study on MHACD revealed that it is a redox active compound with promising catalytic properties in electrochemical applications. The inhibition potential of MHACD for mild steel corrosion in 1 M HCl was investigated using potentiodynamic polarization method. The results showed that MHACD inhibits steel corrosion as a mixed-type inhibitor, and the inhibition efficiency increases with increasing concentration of MHACD. The adsorption of MHACD obeys the Langmuir adsorption isotherm; it is spontaneous and involves competitive physisorption and chemisorption mechanisms. Quantum chemical calculations revealed that the energy of the highest occupied molecular orbital (HOMO) of MHACD is high enough to favor forward donation of charges to the metal during adsorption and corrosion inhibition. Natural bond orbital (NBO) analysis revealed the presence of various orbitals in the MHACD that are capable of donating or accepting electrons under favorable conditions. Full article
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17 pages, 3606 KiB  
Article
In-Plane Behaviour of a Reinforcement Concrete Frame with a Dry Stack Masonry Panel
by Kun Lin, Yuri Zarevich Totoev, Hongjun Liu and Tianyou Guo
Materials 2016, 9(2), 108; https://doi.org/10.3390/ma9020108 - 11 Feb 2016
Cited by 26 | Viewed by 6292
Abstract
In order to improve the energy dissipation of the masonry infilled frame structure while decreasing the stiffening and strengthening effects of the infill panels, a new dry stacked panel (DSP) semi-interlocking masonry (SIM) infill panel has been developed. In this paper, the material [...] Read more.
In order to improve the energy dissipation of the masonry infilled frame structure while decreasing the stiffening and strengthening effects of the infill panels, a new dry stacked panel (DSP) semi-interlocking masonry (SIM) infill panel has been developed. In this paper, the material properties of DSP and a traditional unreinforced masonry (URM) panel have been evaluated experimentally. A series of cyclic tests were performed to investigate the cyclic behaviour of the reinforcement concrete (RC) frame with different infill panels. The failure modes, damage evolution, hysteretic behaviour, stiffness degradation and energy dissipation were compared and analysed. We concluded that DSP is capable of significantly improving the seismic energy dissipation due to its hysteretic behaviour when the frame is in elastic stage without increasing the stiffness of the frame. Therefore, DSP or SIM panels can be considered as frictional dampers. Based on the experimental results, the influence of DSP was examined. Using the parallel model, the hysteretic loops of DSP subjected to different load cases were achieved. The typical full hysteretic loop for DSP could be divided into three distinct stages of behaviour: packing stage, constant friction stage and equivalent strut stage. The connection between the panel and the frame had a great effect on the transferring of different mechanical stages. The constant friction stage was verified to provide substantial energy dissipation and benefits to the ductility of the structure, which, therefore, is suggested to be prolonged in reality. Full article
(This article belongs to the Section Advanced Materials Characterization)
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14 pages, 2792 KiB  
Article
Imaging Techniques and Scanning Electron Microscopy as Tools for Characterizing a Si-Based Material Used in Air Monitoring Applications
by Suárez-Peña Beatriz, Negral Luis, Castrillón Leonor, Megido Laura, Marañón Elena and Fernández-Nava Yolanda
Materials 2016, 9(2), 109; https://doi.org/10.3390/ma9020109 - 11 Feb 2016
Cited by 20 | Viewed by 7059
Abstract
This paper presents a study of the quartz fibrous filters used as a substrate for capturing the particulate matter (PM) present in the air. Although these substrates are widely used in environmental applications, their microstructure has been barely studied. The behavior of these [...] Read more.
This paper presents a study of the quartz fibrous filters used as a substrate for capturing the particulate matter (PM) present in the air. Although these substrates are widely used in environmental applications, their microstructure has been barely studied. The behavior of these devices during the filtration process was investigated in terms of their microstructure and the quartz fibers. Surface and cross sections were monitored. Scanning electronic microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), imaging and stereology techniques were used as tools for this purpose. The results show that most of the quartz filter fibers have sizes that allow them to be classified as nanofibers. It was also observed that, while the mechanisms of the mechanical capture of particles via impaction, interception and diffusion operate simultaneously in the outer zones of the filter cross section, the mechanism of capture by impaction is virtually non-existent in the innermost zones. Particles between 0.1 and 0.5 μm are known to be the most difficult to have captured by means of fibrous substrates. The fibers in inner zones were highly efficient in capturing this type of particle. Full article
(This article belongs to the Special Issue Materials and Nanomaterials for Environmental and Bio-Medical Applications)
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10 pages, 2341 KiB  
Article
Research on the Thermal Decomposition Reaction Kinetics and Mechanism of Pyridinol-Blocked Isophorone Diisocyanate
by Sen Guo, Jingwei He, Weixun Luo and Fang Liu
Materials 2016, 9(2), 110; https://doi.org/10.3390/ma9020110 - 11 Feb 2016
Cited by 18 | Viewed by 7535
Abstract
A series of pyridinol-blocked isophorone isocyanates, based on pyridinol including 2-hydroxypyridine, 3-hydroxypyridine, and 4-hydroxypyridine, was synthesized and characterized by 1H-NMR, 13C-NMR, and FTIR spectra. The deblocking temperature of blocked isocyanates was established by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and [...] Read more.
A series of pyridinol-blocked isophorone isocyanates, based on pyridinol including 2-hydroxypyridine, 3-hydroxypyridine, and 4-hydroxypyridine, was synthesized and characterized by 1H-NMR, 13C-NMR, and FTIR spectra. The deblocking temperature of blocked isocyanates was established by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and the CO2 evaluation method. The deblocking studies revealed that the deblocking temperature was increased with pyridinol nucleophilicity in this order: 3-hydroxypyridine > 4-hydroxypyridine > 2-hydroxypyridine. The thermal decomposition reaction of 4-hydroxypyridine blocked isophorone diisocyanate was studied by thermo-gravimetric analysis. The Friedman–Reich–Levi (FRL) equation, Flynn–Wall–Ozawa (FWO) equation, and Crane equation were utilized to analyze the thermal decomposition reaction kinetics. The activation energy calculated by FRL method and FWO method was 134.6 kJ·mol−1 and 126.2 kJ·mol−1, respectively. The most probable mechanism function calculated by the FWO method was the Jander equation. The reaction order was not an integer because of the complicated reactions of isocyanate. Full article
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13 pages, 10449 KiB  
Article
An Investigation on the Wear Resistance and Fatigue Behaviour of Ti-6Al-4V Notched Members Coated with Hydroxyapatite Coatings
by Reza H Oskouei, Khosro Fallahnezhad and Sushmitha Kuppusami
Materials 2016, 9(2), 111; https://doi.org/10.3390/ma9020111 - 16 Feb 2016
Cited by 19 | Viewed by 6369
Abstract
In this study, surface properties of Ti-6Al-4V alloy coated with hydroxyapatite coatings were investigated. Wear resistance and fatigue behaviour of samples with coating thicknesses of 10 and 50 µm as well as uncoated samples were examined. Wear experiments demonstrated that the friction factor [...] Read more.
In this study, surface properties of Ti-6Al-4V alloy coated with hydroxyapatite coatings were investigated. Wear resistance and fatigue behaviour of samples with coating thicknesses of 10 and 50 µm as well as uncoated samples were examined. Wear experiments demonstrated that the friction factor of the uncoated titanium decreased from 0.31 to 0.06, through a fluctuating trend, after 50 cycles of wear tests. However, the friction factor of both the coated samples (10 and 50 µm) gradually decreased from 0.20 to 0.12 after 50 cycles. At the end of the 50th cycle, the penetration depth of the 10 and 50 µm coated samples were 7.69 and 6.06 µm, respectively. Fatigue tests showed that hydroxyapatite coatings could improve fatigue life of a notched Ti-6Al-4V member in both low and high cycle fatigue zones. It was understood, from fractography of the fracture surfaces, that the fatigue zone of the uncoated specimens was generally smaller in comparison with that of the coated specimens. No significant difference was observed between the fatigue life of coated specimens with 10 and 50 µm thicknesses. Full article
(This article belongs to the Special Issue Surface Modification Methods to Improve Fatigue, Fretting Fatigue, and Fretting Wear Behavior of Materials)
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24 pages, 1188 KiB  
Article
Residual Stress Analysis Based on Acoustic and Optical Methods
by Sanichiro Yoshida, Tomohiro Sasaki, Masaru Usui, Shuichi Sakamoto, David Gurney and Ik-Keun Park
Materials 2016, 9(2), 112; https://doi.org/10.3390/ma9020112 - 16 Feb 2016
Cited by 12 | Viewed by 7013
Abstract
Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able [...] Read more.
Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able to measure deformation yielding two-dimensional, full-field data, but it is not suitable for absolute evaluation of residual stresses. By theoretically relating the deformation data to residual stresses, and calibrating it with absolute residual stress evaluated at a reference point, it is possible to measure residual stresses quantitatively, nondestructively and two-dimensionally. The feasibility of the idea has been tested with a butt-jointed dissimilar plate specimen. A steel plate 18.5 mm wide, 50 mm long and 3.37 mm thick is braze-jointed to a cemented carbide plate of the same dimension along the 18.5 mm-side. Acoustoelasticity evaluates the elastic modulus at reference points via acoustic velocity measurement. A tensile load is applied to the specimen at a constant pulling rate in a stress range substantially lower than the yield stress. Optical interferometry measures the resulting acceleration field. Based on the theory of harmonic oscillation, the acceleration field is correlated to compressive and tensile residual stresses qualitatively. The acoustic and optical results show reasonable agreement in the compressive and tensile residual stresses, indicating the feasibility of the idea. Full article
(This article belongs to the Special Issue Materials in Motorsport)
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19 pages, 13165 KiB  
Article
An in Vitro Twist Fatigue Test of Fabric Stent-Grafts Supported by Z-Stents vs. Ringed Stents
by Jing Lin, Robert Guidoin, Jia Du, Lu Wang, Graeham Douglas, Danjie Zhu, Mark Nutley, Lygia Perron, Ze Zhang and Yvan Douville
Materials 2016, 9(2), 113; https://doi.org/10.3390/ma9020113 - 16 Feb 2016
Cited by 20 | Viewed by 9260
Abstract
Whereas buckling can cause type III endoleaks, long-term twisting of a stent-graft was investigated here as a mechanism leading to type V endoleak or endotension. Two experimental device designs supported with Z-stents having strut angles of 35° or 45° were compared to a [...] Read more.
Whereas buckling can cause type III endoleaks, long-term twisting of a stent-graft was investigated here as a mechanism leading to type V endoleak or endotension. Two experimental device designs supported with Z-stents having strut angles of 35° or 45° were compared to a ringed control under accelerated twisting. Damage to each device was assessed and compared after different durations of twisting, with focus on damage that may allow leakage. Stent-grafts with 35° Z-stents had the most severe distortion and damage to the graft fabric. The 45° Z-stents caused less fabric damage. However, consistent stretching was still seen around the holes for sutures, which attach the stents to the graft fabric. Larger holes may become channels for fluid percolation through the wall. The ringed stent-graft had the least damage observed. Stent apexes with sharp angles appear to be responsible for major damage to the fabrics. Device manufacturers should consider stent apex angle when designing stent-grafts, and ensure their devices are resistant to twisting. Full article
(This article belongs to the Section Advanced Materials Characterization)
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9 pages, 2147 KiB  
Article
Tailored N-Containing Carbons as Catalyst Supports in Alcohol Oxidation
by Sebastiano Campisi, Stefania Marzorati, Paolo Spontoni, Carine E. Chan-Thaw, Mariangela Longhi, Alberto Villa and Laura Prati
Materials 2016, 9(2), 114; https://doi.org/10.3390/ma9020114 - 17 Feb 2016
Cited by 5 | Viewed by 5197
Abstract
The introduction of N-containing functionalities in carbon-based materials is brought to stable and highly active metal-supported catalysts. However, up to now, the role of the amount and the nature of N-groups have not been completely clear. This study aims to clarify these aspects [...] Read more.
The introduction of N-containing functionalities in carbon-based materials is brought to stable and highly active metal-supported catalysts. However, up to now, the role of the amount and the nature of N-groups have not been completely clear. This study aims to clarify these aspects by preparing tailored N-containing carbons where different N-groups are introduced during the synthesis of the carbon material. These materials were used as the support for Pd nanoparticles. Testing these catalysts in alcohol oxidations and comparing the results with those obtained using Pd nanoparticles supported on different N-containing supports allowed us to obtain insight into the role of the different N-containing groups. In the cinnamyl alcohol oxidation, pyridine-like groups seem to favor both activity and selectivity toward cinnamaldehyde. Full article
(This article belongs to the Special Issue Porous Carbonaceous Materials from Biomass)
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16 pages, 8212 KiB  
Article
Structure and Compressive Properties of Invar-Cenosphere Syntactic Foams
by Dung Luong, Dirk Lehmhus, Nikhil Gupta, Joerg Weise and Mohamed Bayoumi
Materials 2016, 9(2), 115; https://doi.org/10.3390/ma9020115 - 18 Feb 2016
Cited by 34 | Viewed by 9217
Abstract
The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately [...] Read more.
The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately 41.6 and 60.0 vol.% in relation to the metal content and at 0.6 g/cm3 hollow particle density. The synthesis process results in survival of cenospheres and provides low density syntactic foams. The microstructure of the materials is investigated as well as the mechanical performance under quasi-static and high strain rate compressive loads. The compressive stress-strain curves of syntactic foams reveal a continuous strain hardening behavior in the plastic region, followed by a densification region. The results reveal a strain rate sensitivity in cenosphere-based Invar matrix syntactic foams. Differences in properties between cenosphere- and glass microsphere-based materials are discussed in relation to the findings of microstructural investigations. Cenospheres present a viable choice as filler material in iron-based syntactic foams due to their higher thermal stability compared to glass microspheres. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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26 pages, 10818 KiB  
Review
Bio-Inspired Extreme Wetting Surfaces for Biomedical Applications
by Sera Shin, Jungmok Seo, Heetak Han, Subin Kang, Hyunchul Kim and Taeyoon Lee
Materials 2016, 9(2), 116; https://doi.org/10.3390/ma9020116 - 19 Feb 2016
Cited by 116 | Viewed by 18594
Abstract
Biological creatures with unique surface wettability have long served as a source of inspiration for scientists and engineers. More specifically, materials exhibiting extreme wetting properties, such as superhydrophilic and superhydrophobic surfaces, have attracted considerable attention because of their potential use in various applications, [...] Read more.
Biological creatures with unique surface wettability have long served as a source of inspiration for scientists and engineers. More specifically, materials exhibiting extreme wetting properties, such as superhydrophilic and superhydrophobic surfaces, have attracted considerable attention because of their potential use in various applications, such as self-cleaning fabrics, anti-fog windows, anti-corrosive coatings, drag-reduction systems, and efficient water transportation. In particular, the engineering of surface wettability by manipulating chemical properties and structure opens emerging biomedical applications ranging from high-throughput cell culture platforms to biomedical devices. This review describes design and fabrication methods for artificial extreme wetting surfaces. Next, we introduce some of the newer and emerging biomedical applications using extreme wetting surfaces. Current challenges and future prospects of the surfaces for potential biomedical applications are also addressed. Full article
(This article belongs to the Special Issue Superhydrophobicity of Materials)
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16 pages, 9918 KiB  
Article
Tribo-Mechanical Properties of HVOF Deposited Fe3Al Coatings Reinforced with TiB2 Particles for Wear-Resistant Applications
by Mahdi Amiriyan, Carl Blais, Sylvio Savoie, Robert Schulz, Mario Gariépy and Houshang Alamdari
Materials 2016, 9(2), 117; https://doi.org/10.3390/ma9020117 - 19 Feb 2016
Cited by 18 | Viewed by 5873
Abstract
This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy [...] Read more.
This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. Full article
(This article belongs to the Section Advanced Composites)
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17 pages, 3605 KiB  
Article
Investigation of Fumed Silica/Aqueous NaCl Superdielectric Material
by Natalie Jenkins, Clayton Petty and Jonathan Phillips
Materials 2016, 9(2), 118; https://doi.org/10.3390/ma9020118 - 20 Feb 2016
Cited by 9 | Viewed by 5338
Abstract
A constant current charge/discharge protocol which showed fumed silica filled to the point of incipient wetness with aqueous NaCl solution to have dielectric constants >108 over the full range of dielectric thicknesses of 0.38–3.9 mm and discharge times of 0.25–>100 s was [...] Read more.
A constant current charge/discharge protocol which showed fumed silica filled to the point of incipient wetness with aqueous NaCl solution to have dielectric constants >108 over the full range of dielectric thicknesses of 0.38–3.9 mm and discharge times of 0.25–>100 s was studied, making this material another example of a superdielectric. The dielectric constant was impacted by both frequency and thickness. For time to discharge greater than 10 s the dielectric constant for all thicknesses needed to be fairly constant, always >109, although trending higher with increasing thickness. At shorter discharge times the dielectric constant consistently decreased, with decreasing time to discharge. Hence, it is reasonable to suggest that for time to discharge >10 s the dielectric constant at all thicknesses will be greater than 109. This in turn implies an energy density for a 5 micron thick dielectric layer in the order of 350 J/cm3 for discharge times greater than 10 s. Full article
(This article belongs to the Section Energy Materials)
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