Materials

1422 KiB

Open AccessReview

Synthetic Strategies in the Preparation of Polymer/Inorganic Hybrid Nanoparticles

by Matthew A. Hood, Margherita Mari and Rafael Muñoz-Espí

Materials 2014, 7(5), 4057-4087; https://doi.org/10.3390/ma7054057 - 22 May 2014

Cited by 162 | Viewed by 18048 | Correction

This article reviews the recent advances and challenges in the preparation of polymer/inorganic hybrid nanoparticles. We mainly focus on synthetic strategies, basing our classification on whether the inorganic and the polymer components have been formed in situ or ex situ, of the [...] Read more.

This article reviews the recent advances and challenges in the preparation of polymer/inorganic hybrid nanoparticles. We mainly focus on synthetic strategies, basing our classification on whether the inorganic and the polymer components have been formed in situ or ex situ, of the hybrid material. Accordingly, four types of strategies are identified and described, referring to recent examples: (i) ex situ formation of the components and subsequent attachment or integration, either by covalent or noncovalent bonding; (ii) in situ polymerization in the presence of ex situ formed inorganic nanoparticles; (iii) in situ precipitation of the inorganic components on or in polymer structures; and (iv) strategies in which both polymer and inorganic component are simultaneously formed in situ. Full article

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

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816 KiB

Open AccessArticle

Novel Discotic Boroxines: Synthesis and Mesomorphic Properties

by Tobias Wöhrle, Angelika Baro and Sabine Laschat

Materials 2014, 7(5), 4045-4056; https://doi.org/10.3390/ma7054045 - 22 May 2014

Cited by 20 | Viewed by 8919

Abstract

A new synthetic approach to highly substituted triphenylboroxines 11 is described. Their mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (SAXS, WAXS). The tris(3,4,5-trialkyloxy)phenyl functionalized derivatives 11b–e showed broad mesophases for a minimum [...] Read more.

A new synthetic approach to highly substituted triphenylboroxines 11 is described. Their mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (SAXS, WAXS). The tris(3,4,5-trialkyloxy)phenyl functionalized derivatives 11b–e showed broad mesophases for a minimum alkyl chain length of C9. The phase widths ranged from 110 K to 77 K near room temperature, thus decreasing with enhanced alkyl chain lengths. Textures observed under POM indicated a columnar hexagonal (Col_h) mesophase symmetry that was confirmed by X-ray diffraction experiments. Full article

(This article belongs to the Special Issue Liquid Crystals)

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733 KiB

Open AccessArticle

Visible-Light Active and Magnetically Recyclable Nanocomposites for the Degradation of Organic Dye

by Helin Niu, Qinmin Wang, Hongxia Liang, Min Chen, Changjie Mao, Jiming Song, Shengyi Zhang, Yuanhao Gao and Changle Chen

Materials 2014, 7(5), 4034-4044; https://doi.org/10.3390/ma7054034 - 21 May 2014

Cited by 37 | Viewed by 7517

Abstract

Recyclable visible-light photocatalyst Fe₃O₄@TiO₂ with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe₃O₄ nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to [...] Read more.

Recyclable visible-light photocatalyst Fe₃O₄@TiO₂ with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe₃O₄ nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to evaluate the visible-light photocatalytic activity of the as prepared Fe₃O₄@TiO₂ nanoparticles, which show excellent photocatalytic activity compared with commercial P25 catalyst. Moreover, the Fe₃O₄@TiO₂ nanocomposites can be easily separated from the reaction mixture, and maintain favorable photocatalytic activity after five cycles. The high visible light absorption of the Fe₃O₄@TiO₂ nanocomposites may originate from the absence of electronic heterojunction, excellently dispersity and the high specific surface area of the as-synthesized Fe₃O₄@TiO₂ samples. Full article

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697 KiB

Open AccessArticle

Comparing Triflate and Hexafluorophosphate Anions of Ionic Liquids in Polymer Electrolytes for Supercapacitor Applications

by Chiam-Wen Liew and S. Ramesh

Materials 2014, 7(5), 4019-4033; https://doi.org/10.3390/ma7054019 - 21 May 2014

Cited by 69 | Viewed by 8359

Abstract

Two different ionic liquid-based biopolymer electrolyte systems were prepared using a solution casting technique. Corn starch and lithium hexafluorophosphate (LiPF₆) were employed as polymer and salt, respectively. Additionally, two different counteranions of ionic liquids, viz. 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF₆) and [...] Read more.

Two different ionic liquid-based biopolymer electrolyte systems were prepared using a solution casting technique. Corn starch and lithium hexafluorophosphate (LiPF₆) were employed as polymer and salt, respectively. Additionally, two different counteranions of ionic liquids, viz. 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF₆) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (also known as 1-butyl-3-methylimidazolium triflate) (BmImTf) were used and studied in this present work. The maximum ionic conductivities of (1.47 ± 0.02) × 10⁻⁴ and (3.21 ± 0.01) × 10⁻⁴ S∙cm⁻¹ were achieved with adulteration of 50 wt% of BmImPF₆ and 80 wt% of BmImTf, respectively at ambient temperature. Activated carbon-based electrodes were prepared and used in supercapacitor fabrication. Supercapacitors were then assembled using the most conducting polymer electrolyte from each system. The electrochemical properties of the supercapacitors were then analyzed. The supercapacitor containing the triflate-based biopolymer electrolyte depicted a higher specific capacitance with a wider electrochemical stability window compared to that of the hexafluorophosphate system. Full article

(This article belongs to the Section Energy Materials)

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1783 KiB

Open AccessArticle

Effect of Polymer Infiltration on the Flexural Behavior of β-Tricalcium Phosphate Robocast Scaffolds

by Francisco J. Martínez-Vázquez, Antonia Pajares, Fernando Guiberteau and Pedro Miranda

Materials 2014, 7(5), 4001-4018; https://doi.org/10.3390/ma7054001 - 21 May 2014

Cited by 53 | Viewed by 8790

Abstract

The influence of polymer infiltration on the flexural strength and toughness of β-tricalcium phosphate (β-TCP) scaffolds fabricated by robocasting (direct-write assembly) is analyzed. Porous structures consisting of a tetragonal three-dimensional lattice of interpenetrating rods were impregnated with biodegradable polymers (poly(lactic acid) (PLA) and [...] Read more.

The influence of polymer infiltration on the flexural strength and toughness of β-tricalcium phosphate (β-TCP) scaffolds fabricated by robocasting (direct-write assembly) is analyzed. Porous structures consisting of a tetragonal three-dimensional lattice of interpenetrating rods were impregnated with biodegradable polymers (poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL)) by immersion of the structure in a polymer melt. Infiltration increased the flexural strength of these model scaffolds by a factor of 5 (PCL) or 22 (PLA), an enhancement considerably greater than that reported for compression strength of analogue materials. The greater strength improvement in bending was attributed to a more effective transfer of stress to the polymer under this solicitation since the degree of strengthening associated to the sealing of precursor flaws in the ceramic rod surfaces should remain unaltered. Impregnation with either polymer also improved further than in compression the fracture energy of the scaffolds (by more than two orders of magnitude). This increase is associated to the extraordinary strengthening provided by impregnation and to a crack bridging toughening mechanism produced by polymer fibrils. Full article

(This article belongs to the Special Issue Ceramics for Healthcare 2013)

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1945 KiB

Open AccessArticle

Microstructure Analysis of Ti-xPt Alloys and the Effect of Pt Content on the Mechanical Properties and Corrosion Behavior of Ti Alloys

by Ho-Jun Song, Mi-Kyung Han, Hyeon-Gyeong Jeong, Yong-Tai Lee and Yeong-Joon Park

Materials 2014, 7(5), 3990-4000; https://doi.org/10.3390/ma7053990 - 21 May 2014

Cited by 5 | Viewed by 6767

Abstract

The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt [...] Read more.

The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt (x = 5, 10, 15, 20) alloys showed hexagonal α-Ti structure with cubic Ti₃Pt intermetallic phase. The mechanical properties and corrosion behavior of Ti-xPt alloys were sensitive to the Pt content. The addition of Pt contributed to hardening of cp-Ti and to improving its oxidation resistance. Electrochemical results showed that the Ti-xPt alloys exhibited superior corrosion resistance than that of cp-Ti. Full article

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885 KiB

Open AccessReview

Hybrid Materials Based on the Embedding of Organically Modified Transition Metal Oxoclusters or Polyoxometalates into Polymers for Functional Applications: A Review

by Mauro Carraro and Silvia Gross

Materials 2014, 7(5), 3956-3989; https://doi.org/10.3390/ma7053956 - 20 May 2014

Cited by 106 | Viewed by 14786

Abstract

The covalent incorporation of inorganic building blocks into a polymer matrix to obtain stable and robust materials is a widely used concept in the field of organic-inorganic hybrid materials, and encompasses the use of different inorganic systems including (but not limited to) nanoparticles, [...] Read more.

The covalent incorporation of inorganic building blocks into a polymer matrix to obtain stable and robust materials is a widely used concept in the field of organic-inorganic hybrid materials, and encompasses the use of different inorganic systems including (but not limited to) nanoparticles, mono- and polynuclear metal complexes and clusters, polyhedral oligomeric silsesquioxanes (POSS), polyoxometalates (POM), layered inorganic systems, inorganic fibers, and whiskers. In this paper, we will review the use of two particular kinds of structurally well-defined inorganic building blocks, namely transition metals oxoclusters (TMO) and polyoxometalates (POM), to obtain hybrid materials with enhanced functional (e.g., optical, dielectric, magnetic, catalytic) properties. Full article

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

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649 KiB

Open AccessArticle

Antimicrobial Activity of Chitosan-Carbon Nanotube Hydrogels

by Jayachandran Venkatesan, Rangasamy Jayakumar, Annapoorna Mohandas, Ira Bhatnagar and Se-Kwon Kim

Materials 2014, 7(5), 3946-3955; https://doi.org/10.3390/ma7053946 - 19 May 2014

Cited by 106 | Viewed by 10560

Abstract

In the present study, we have prepared chitosan-carbon nanotube (Chitosan-CNT) hydrogels by the freeze-lyophilization method and examined their antimicrobial activity. Different concentrations of CNT were used in the preparation of Chitosan-CNT hydrogels. These differently concentrated CNT hydrogels were chemically characterized using Fourier Transform-Infrared [...] Read more.

In the present study, we have prepared chitosan-carbon nanotube (Chitosan-CNT) hydrogels by the freeze-lyophilization method and examined their antimicrobial activity. Different concentrations of CNT were used in the preparation of Chitosan-CNT hydrogels. These differently concentrated CNT hydrogels were chemically characterized using Fourier Transform-Infrared Spectroscopy, Scanning Electron Microscopy and Optical microscopy. The porosity of the hydrogels were found to be >94%. Dispersion of chitosan was observed in the CNT matrix by normal photography and optical microscopy. The addition of CNT in the composite scaffold significantly reduced the water uptake ability. In order to evaluate antimicrobial activity, the serial dilution method was used towards Staphylococcus aureus, Escherichia coli and Candida tropicalis. The composite Chitosan-CNT hydrogel showed greater antimicrobial activity with increasing CNT concentration, suggesting that Chitosan-CNT hydrogel scaffold will be a promising biomaterial in biomedical applications. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1247 KiB

Open AccessReview

Carbon Nanofibers and Their Composites: A Review of Synthesizing, Properties and Applications

by Lichao Feng, Ning Xie and Jing Zhong

Materials 2014, 7(5), 3919-3945; https://doi.org/10.3390/ma7053919 - 15 May 2014

Cited by 340 | Viewed by 17470

Abstract

Carbon nanofiber (CNF), as one of the most important members of carbon fibers, has been investigated in both fundamental scientific research and practical applications. CNF composites are able to be applied as promising materials in many fields, such as electrical devices, electrode materials [...] Read more.

Carbon nanofiber (CNF), as one of the most important members of carbon fibers, has been investigated in both fundamental scientific research and practical applications. CNF composites are able to be applied as promising materials in many fields, such as electrical devices, electrode materials for batteries and supercapacitors and as sensors. In these applications, the electrical conductivity is always the first priority need to be considered. In fact, the electrical property of CNF composites largely counts on the dispersion and percolation status of CNFs in matrix materials. In this review, the electrical transport phenomenon of CNF composites is systematically summarized based on percolation theory. The effects of the aspect ratio, percolation backbone structure and fractal characteristics of CNFs and the non-universality of the percolation critical exponents on the electrical properties are systematically reviewed. Apart from the electrical property, the thermal conductivity and mechanical properties of CNF composites are briefly reviewed, as well. In addition, the preparation methods of CNFs, including catalytic chemical vapor deposition growth and electrospinning, and the preparation methods of CNF composites, including the melt mixing and solution process, are briefly introduced. Finally, their applications as sensors and electrode materials are described in this review article. Full article

(This article belongs to the Section Advanced Composites)

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819 KiB

Open AccessArticle

Synthesis of MgB₂ at Low Temperature and Autogenous Pressure

by Ian D. R. Mackinnon, Abigail Winnett, Jose A. Alarco and Peter C. Talbot

Materials 2014, 7(5), 3901-3918; https://doi.org/10.3390/ma7053901 - 15 May 2014

Cited by 12 | Viewed by 7495

Abstract

High quality, micron-sized interpenetrating grains of MgB₂, with high density, are produced at low temperatures (~420 °C < T < ~500 °C) under autogenous pressure by pre-mixing Mg powder and NaBH₄ and heating in an Inconel 601 alloy reactor for [...] Read more.

High quality, micron-sized interpenetrating grains of MgB₂, with high density, are produced at low temperatures (~420 °C < T < ~500 °C) under autogenous pressure by pre-mixing Mg powder and NaBH₄ and heating in an Inconel 601 alloy reactor for 5–15 h. Optimum production of MgB₂, with yields greater than 75%, occurs for autogenous pressure in the range 1.0 MPa to 2.0 MPa, with the reactor at ~500 °C. Autogenous pressure is induced by the decomposition of NaBH₄ in the presence of Mg and/or other Mg-based compounds. The morphology, transition temperature and magnetic properties of MgB₂ are dependent on the heating regime. Significant improvement in physical properties accrues when the reactor temperature is held at 250 °C for >20 min prior to a hold at 500 °C. Full article

(This article belongs to the Section Energy Materials)

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1342 KiB

Open AccessReview

Functional Films from Silica/Polymer Nanoparticles

by Tânia Ribeiro, Carlos Baleizão and José Paulo S. Farinha

Materials 2014, 7(5), 3881-3900; https://doi.org/10.3390/ma7053881 - 15 May 2014

Cited by 89 | Viewed by 18583

Abstract

High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to [...] Read more.

High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to obtain hybrid polymer films with increased tensile strength and impact resistance, without decreasing the flexural properties of the polymer matrix. The SiNPs can further be used as carriers to impart other functionalities (optical, etc.) to the hybrid films. By using polymer-coated SiNPs, it is possible to reduce particle aggregation in the films and, thus, achieve more homogeneous distributions of the inorganic components and, therefore, better properties. On the other hand, by coating polymer particles with silica, one can create hierarchically structured materials, for example to obtain superhydrophobic coatings. In this review, we will cover the latest developments in films prepared from hybrid polymer/silica functional systems. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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1370 KiB

Open AccessArticle

CO₂ Capture and Separation Properties in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Nonafluorobutylsulfonate

by Lingyun Zhou, Jing Fan and Xiaomin Shang

Materials 2014, 7(5), 3867-3880; https://doi.org/10.3390/ma7053867 - 14 May 2014

Cited by 33 | Viewed by 6108

Abstract

Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO₂ in ILs. In the present work, solubility measurements of CO₂ in the novel IL [...] Read more.

Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO₂ in ILs. In the present work, solubility measurements of CO₂ in the novel IL 1-n-butyl-3-methylimidazolium nonafluorobutylsulfonate [C₄mim][CF₃CF₂CF₂CF₂SO₃] were performed with a high-pressure view-cell technique in the temperature range from 293.15 to 343.15 K and pressures up to about 4.2 MPa. For comparison, solubilities of H₂, N₂, and O₂ in the IL were also measured at 323.15 K via the same procedure. The Krichevsky-Kasarnovsky equation was employed to correlate the measured solubility data. Henry’s law constants, enthalpies, and entropies of absorption for CO₂ in the IL were also determined and presented. The CO₂ solubility in this IL was compared with other ILs sharing the same cation. It was shown that the solubility of CO₂ in these ILs follows the sequence: [C₄mim][CF₃CF₂CF₂CF₂SO₃] ≈ [C₄mim][Tf₂N] > [C₄mim][CF₃CF₂CF₂COO] > [C₄mim][BF₄], and the solubility selectivity of CO₂ relative to O₂, N₂, and H₂ in [C₄mim][CF₃CF₂CF₂CF₂SO₃] was 8, 16, and 22, respectively. Furthermore, this IL is regenerable and exhibits good stability. Therefore, the IL reported here would be a promising sorbent for CO₂. Full article

(This article belongs to the Section Energy Materials)

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1360 KiB

Open AccessArticle

Effect of Receptor Structure and Length on the Wrapping of a Nanoparticle by a Lipid Membrane

by Haizhen Zhang, Ling Wang, Bing Yuan, Kai Yang and Yuqiang Ma

Materials 2014, 7(5), 3855-3866; https://doi.org/10.3390/ma7053855 - 14 May 2014

Cited by 5 | Viewed by 5547

Abstract

Nanoparticles have been considered as a type of powerful tool to deliver drugs and genes into cells for disease diagnosis and therapies. It has been generally accepted that the internalization of nanoparticles into cells is mostly realized by receptor-mediated endocytosis. However, for the [...] Read more.

Nanoparticles have been considered as a type of powerful tool to deliver drugs and genes into cells for disease diagnosis and therapies. It has been generally accepted that the internalization of nanoparticles into cells is mostly realized by receptor-mediated endocytosis. However, for the influence of structural factors of receptors on endocytosis, this is still largely unknown. In this paper, computer simulations are applied to investigate the effects of structure (i.e., the number of constituent chains of the receptor) and the length of the receptor on the wrapping behavior of nanoparticles by the lipid membrane, which is a key step of receptor-medicated endocytosis. It is found that these structural factors of receptors have strong effects on the nanoparticle’s final interaction configuration with the membrane in the simulations, such as adhering on the membrane surface or being partly or fully wrapped by the membrane. Furthermore, in some cases, the rupture of the lipid membrane occurs. These results are helpful for the understanding of endocytosis and the preparation of advanced nanoscale drug-delivery vectors. Full article

(This article belongs to the Section Biomaterials)

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856 KiB

Open AccessReview

Porous Gold Films—A Short Review on Recent Progress

by Renyun Zhang and Håkan Olin

Materials 2014, 7(5), 3834-3854; https://doi.org/10.3390/ma7053834 - 14 May 2014

Cited by 66 | Viewed by 10589

Abstract

Porous gold films have attracted increasing interest over the last ten years due to the unique properties of high specific surface area and electrical conductivity combined with chemical stability and ability to alter the surface chemistry. Several methods have been developed to synthesize [...] Read more.

Porous gold films have attracted increasing interest over the last ten years due to the unique properties of high specific surface area and electrical conductivity combined with chemical stability and ability to alter the surface chemistry. Several methods have been developed to synthesize porous gold films such as de-alloying, templating, electrochemical, and self-assembling. These porous gold films are used in diverse fields, for example, as electrochemical and Raman sensors or for chemical catalysis. Here, we provide a short review on the progress of porous gold films over the past ten years, including the synthesis and applications of such films. Full article

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

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604 KiB

Open AccessArticle

Carbonized Micro- and Nanostructures: Can Downsizing Really Help?

by Mohammad Naraghi and Sneha Chawla

Materials 2014, 7(5), 3820-3833; https://doi.org/10.3390/ma7053820 - 14 May 2014

Cited by 23 | Viewed by 5969

Abstract

In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs) with diameters of 5–10 µm to submicron thick carbon nanofibers (CNFs). Our research points to [...] Read more.

In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs) with diameters of 5–10 µm to submicron thick carbon nanofibers (CNFs). Our research points to radial inhomogeneity, skin–core structure, as a size-dependent feature of polyacrylonitrile-based CFs. This inhomogeneity is a surface effect, caused by suppressed diffusion of oxygen and stabilization byproducts during stabilization through skin. Hence, reducing the precursor diameters from tens of microns to submicron appears as an effective strategy to develop homogeneous carbonized structures. Our research establishes the significance of this downsizing in developing lightweight structural materials by comparing intrinsic strength of radially inhomogeneous CFs with that of radially homogeneous CNF. While experimental studies on the strength of CNFs have targeted randomly oriented turbostratic domains, via continuum modeling, we have estimated that strength of CNFs can reach 14 GPa, when the basal planes of graphitic domains are parallel to nanofiber axis. The CNFs in our model are treated as composites of amorphous carbon (matrix), reinforced with turbostratic domains, and their strength is predicted using Tsai–Hill criterion. The model was calibrated with existing experimental data. Full article

(This article belongs to the Section Advanced Composites)

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603 KiB

Open AccessArticle

Drilling Damage in Composite Material

by Luís Miguel P. Durão, João Manuel R.S. Tavares, Victor Hugo C. De Albuquerque, Jorge Filipe S. Marques and Oscar N.G. Andrade

Materials 2014, 7(5), 3802-3819; https://doi.org/10.3390/ma7053802 - 14 May 2014

Cited by 88 | Viewed by 10024

Abstract

The characteristics of carbon fibre reinforced laminates have widened their use from aerospace to domestic appliances, and new possibilities for their usage emerge almost daily. In many of the possible applications, the laminates need to be drilled for assembly purposes. It is known [...] Read more.

The characteristics of carbon fibre reinforced laminates have widened their use from aerospace to domestic appliances, and new possibilities for their usage emerge almost daily. In many of the possible applications, the laminates need to be drilled for assembly purposes. It is known that a drilling process that reduces the drill thrust force can decrease the risk of delamination. In this work, damage assessment methods based on data extracted from radiographic images are compared and correlated with mechanical test results—bearing test and delamination onset test—and analytical models. The results demonstrate the importance of an adequate selection of drilling tools and machining parameters to extend the life cycle of these laminates as a consequence of enhanced reliability. Full article

(This article belongs to the Special Issue Carbon Fibers)

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2006 KiB

Open AccessArticle

Solid-State Synthesis and Photocatalytic Activity of Polyterthiophene Derivatives/TiO₂ Nanocomposites

by Ruxangul Jamal, Yakupjan Osman, Adalet Rahman, Ahmat Ali, Yu Zhang and Tursun Abdiryim

Materials 2014, 7(5), 3786-3801; https://doi.org/10.3390/ma7053786 - 14 May 2014

Cited by 45 | Viewed by 8951

Abstract

Poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO₂ and poly(3,4-(2,2-dimethylenepropylenedioxy)-2,2':5',2"-terthiophene)/TiO₂ nanocomposites were synthesized by a simple solid-state method. Additionally, the poly(3,4-propylenedioxy thiophene)/TiO₂ and poly(3,4-2,2-dimethylenepropylenedioxythiophene)/TiO₂ nanocomposites were synthesized in a similar manner for comparison. The structure and morphology were characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis) [...] Read more.

Poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO₂ and poly(3,4-(2,2-dimethylenepropylenedioxy)-2,2':5',2"-terthiophene)/TiO₂ nanocomposites were synthesized by a simple solid-state method. Additionally, the poly(3,4-propylenedioxy thiophene)/TiO₂ and poly(3,4-2,2-dimethylenepropylenedioxythiophene)/TiO₂ nanocomposites were synthesized in a similar manner for comparison. The structure and morphology were characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic activities of the nanocomposites were examined through the degradation processes of a methylene blue (MB) solution under UV light and sunlight irradiation. The results of FTIR and UV-Vis spectra showed that the composites were successfully synthesized by solid-state method and the poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO₂ and poly(3,4-(2,2-dimethylenepropylenedioxy)-2,2':5',2"-terthiophene)/TiO₂ nanocomposite had a higher oxidation degree and conjugation length than others. The results also indicated that the TiO₂ had no effect on the crystallinity of composites, but was well embedded in the polymer matrix. Additionally, the highest degradation efficiency of 90.5% occurred in the case of the poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO₂ nanocomposite. Full article

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471 KiB

Open AccessArticle

Chemical, Mechanical, and Durability Properties of Concrete with Local Mineral Admixtures under Sulfate Environment in Northwest China

by Qingke Nie, Changjun Zhou, Xiang Shu, Qiang He and Baoshan Huang

Materials 2014, 7(5), 3772-3785; https://doi.org/10.3390/ma7053772 - 13 May 2014

Cited by 57 | Viewed by 8540

Abstract

Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts [...] Read more.

Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts of mineral admixtures, such as fly ash and slags from energy and metallurgical industries. These industrial by-products would turn into waste materials if not utilized in time. The present study evaluated the suitability of utilizing local mineral admixtures in significant quantities for producing quality concrete mixtures that can withstand the harsh chemical environment without compromising the essential mechanical properties. Comprehensive chemical, mechanical, and durability tests were conducted in the laboratory to characterize the properties of the local cementitious mineral admixtures, cement mortar and portland cement concrete mixtures containing these admixtures. The results from this study indicated that the sulfate resistance of concrete was effectively improved by adding local class F fly ash and slag, or by applying sulfate resistance cement to the mixtures. It is noteworthy that concrete containing local mineral admixtures exhibited much lower permeability (in terms of chloride ion penetration) than ordinary portland cement concrete while retaining the same mechanical properties; whereas concrete mixtures made with sulfate resistance cement had significantly reduced strength and much increased chloride penetration comparing to the other mixtures. Hence, the use of local mineral admixtures in Northwest China in concrete mixtures would be beneficial to the performance of concrete, as well as to the protection of environment. Full article

(This article belongs to the Section Advanced Composites)

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467 KiB

Open AccessArticle

Effects of Asymmetric Quantum Wells on the Structural and Optical Properties of InGaN-Based Light-Emitting Diodes

by Chia-Lung Tsai and Wei-Che Wu

Materials 2014, 7(5), 3758-3771; https://doi.org/10.3390/ma7053758 - 12 May 2014

Cited by 13 | Viewed by 6462

Abstract

A metalorganic vapor phase epitaxy-grown InGaN/GaN multiple-quantum-well (MQW) with three graded-thickness wells (the first-grown well had the greatest width) near the n-GaN was used as the active layer of an LED. For LEDs with an asymmetric quantum well (AQW), high-resolution X-ray diffraction and [...] Read more.

A metalorganic vapor phase epitaxy-grown InGaN/GaN multiple-quantum-well (MQW) with three graded-thickness wells (the first-grown well had the greatest width) near the n-GaN was used as the active layer of an LED. For LEDs with an asymmetric quantum well (AQW), high-resolution X-ray diffraction and transmission electron microscopic reveal that the modified MQWs with a reasonable crystalline quality were coherently strained on the underlying GaN epilayers without any relaxation. In addition, the slight increase of indium segregation in the LED with an AQW may be attributed to variations in indium contents experienced during epitaxial growth of the wide well-containing MQWs. By preventing the energetic electrons from accumulating at the topmost quantum well nearest the p-GaN, the presence of light intensity roll-off in the LED with an AQW is shifted to higher currents and the corresponding maximum light output power is increased with a ratio 7.9% higher than that of normal LEDs. Finally, similar emission wavelengths were observed in the electroluminescence spectra of both LEDs, suggesting that light emitted mostly from the top quantum wells (near the p-GaN) while the emissions from the AQW region were insignificant. Full article

(This article belongs to the Section Advanced Materials Characterization)

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1981 KiB

Open AccessReview

A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys

by Liming Liu, Daxin Ren and Fei Liu

Materials 2014, 7(5), 3735-3757; https://doi.org/10.3390/ma7053735 - 8 May 2014

Cited by 221 | Viewed by 18073

Abstract

Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from [...] Read more.

Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from different perspectives. Welding of dissimilar Mg and Al is challenging due to the formation of brittle intermetallic compound (IMC) such as Mg₁₇Al₁₂ and Mg₂Al₃. In order to increase the joint strength, three main research approaches were used to eliminate or reduce the Mg-Al intermetallic reaction layer. First, solid state welding techniques which have a low welding temperature were used to reduce the IMCs. Second, IMC variety and distribution were controlled to avoid the degradation of the joining strength in fusion welding. Third, techniques which have relatively controllable reaction time and energy were used to eliminate the IMCs. Some important processing parameters and their effects on weld quality are discussed, and the microstructure and metallurgical reaction are described. Mechanical properties of welds such as hardness, tensile, shear and fatigue strength are discussed. The aim of the report is to review the recent progress in the welding of dissimilar Mg and Al to provide a basis for follow-up research. Full article

(This article belongs to the Special Issue Light Alloys and Their Applications)

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743 KiB

Open AccessArticle

Magnetic Properties of the Ferromagnetic Shape Memory Alloys Ni_50+xMn_27−xGa₂₃ in Magnetic Fields

by Takuo Sakon, Kohei Otsuka, Junpei Matsubayashi, Yuushi Watanabe, Hironori Nishihara, Kenta Sasaki, Satoshi Yamashita, Rie Y. Umetsu, Hiroyuki Nojiri and Takeshi Kanomata

Materials 2014, 7(5), 3715-3734; https://doi.org/10.3390/ma7053715 - 8 May 2014

Cited by 5 | Viewed by 6463

Abstract

Thermal strain, permeability, and magnetization measurements of the ferromagnetic shape memory alloys Ni_50+xMn_27−xGa₂₃ (x = 2.0, 2.5, 2.7) were performed. For x = 2.7, in which the martensite transition and the ferromagnetic transition occur at [...] Read more.

Thermal strain, permeability, and magnetization measurements of the ferromagnetic shape memory alloys Ni_50+xMn_27−xGa₂₃ (x = 2.0, 2.5, 2.7) were performed. For x = 2.7, in which the martensite transition and the ferromagnetic transition occur at the same temperature, the martensite transition starting temperature T_Ms shift in magnetic fields around a zero magnetic field was estimated to be dT_Ms/dB = 1.1 ± 0.2 K/T, thus indicating that magnetic fields influences martensite transition. We discussed the itinerant electron magnetism of x = 2.0 and 2.5. As for x = 2.5, the M⁴ vs. B/M plot crosses the origin of the coordinate axis at the Curie temperature, and the plot indicates a good linear relation behavior around the Curie temperature. The result is in agreement with the theory by Takahashi, concerning itinerant electron ferromagnets. Full article

(This article belongs to the Special Issue Shape Memory Materials)

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Graphical abstract

953 KiB

Open AccessArticle

Fabrication of a Low Density Carbon Fiber Foam and Its Characterization as a Strain Gauge

by Claudia C. Luhrs, Chris D. Daskam, Edwin Gonzalez and Jonathan Phillips

Materials 2014, 7(5), 3699-3714; https://doi.org/10.3390/ma7053699 - 8 May 2014

Cited by 9 | Viewed by 7390

Abstract

Samples of carbon nano-fiber foam (CFF), essentially a 3D solid mat of intertwined nanofibers of pure carbon, were grown using the Constrained Formation of Fibrous Nanostructures (CoFFiN) process in a steel mold at 550 °C from a palladium particle catalysts exposed to fuel [...] Read more.

Samples of carbon nano-fiber foam (CFF), essentially a 3D solid mat of intertwined nanofibers of pure carbon, were grown using the Constrained Formation of Fibrous Nanostructures (CoFFiN) process in a steel mold at 550 °C from a palladium particle catalysts exposed to fuel rich mixtures of ethylene and oxygen. The resulting material was studied using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Surface area analysis (BET), and Thermogravimetric Analysis (TGA). Transient and dynamic mechanical tests clearly demonstrated that the material is viscoelastic. Concomitant mechanical and electrical testing of samples revealed the material to have electrical properties appropriate for application as the sensing element of a strain gauge. The sample resistance versus strain values stabilize after a few compression cycles to show a perfectly linear relationship. Study of microstructure, mechanical and electrical properties of the low density samples confirm the uniqueness of the material: It is formed entirely of independent fibers of diverse diameters that interlock forming a tridimensional body that can be grown into different shapes and sizes at moderate temperatures. It regains its shape after loads are removed, is light weight, presents viscoelastic behavior, thermal stability up to 550 °C, hydrophobicity, and is electrically conductive. Full article

(This article belongs to the Special Issue Carbon Fibers)

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16266 KiB

Open AccessArticle

Optical Properties of Electrically Tunable Two-Dimensional Photonic Lattice Structures Formed in a Holographic Polymer-Dispersed Liquid Crystal Film: Analysis and Experiment

by Mayu Miki, Ryuichiro Ohira and Yasuo Tomita

Materials 2014, 7(5), 3677-3698; https://doi.org/10.3390/ma7053677 - 7 May 2014

Cited by 12 | Viewed by 7056

Abstract

We report on theoretical and experimental investigations of optical wave propagations in two-dimensional photonic lattice structures formed in a holographic polymer-dispersed liquid crystal (HPDLC) film. In the theoretical analysis we employed the 2×2 matrix formulation and the statistical thermodynamics model to analyze the [...] Read more.

We report on theoretical and experimental investigations of optical wave propagations in two-dimensional photonic lattice structures formed in a holographic polymer-dispersed liquid crystal (HPDLC) film. In the theoretical analysis we employed the 2×2 matrix formulation and the statistical thermodynamics model to analyze the formation of anisotropic photonic lattice structures by holographic polymerization. The influence of multiple reflections inside an HPDLC film on the formed refractive index distribution was taken into account in the analysis. In the experiment we fabricated two-dimensional photonic lattice structures in an HPDLC film under three-beam interference holographic polymerization and performed optical measurements of spectral transmittances and wavelength dispersion. We also demonstrated the electrical control capability of the fabricated photonic lattice structure and its dependence on incident wave polarization. These measured results were compared with the calculated ones by means of photonic band and beam propagation calculations. Full article

(This article belongs to the Special Issue Liquid Crystals)

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Graphical abstract

3006 KiB

Open AccessArticle

Performance Comparison of Al–Ti Master Alloys with Different Microstructures in Grain Refinement of Commercial Purity Aluminum

by Wanwu Ding, Tiandong Xia and Wenjun Zhao

Materials 2014, 7(5), 3663-3676; https://doi.org/10.3390/ma7053663 - 7 May 2014

Cited by 33 | Viewed by 8356

Abstract

Three types of Al–5Ti master alloys were synthesized by a method of thermal explosion reaction in pure molten aluminum. Performance comparison of Al–5Ti master alloy in grain refinement of commercial purity Al with different additions (0.6%, 1.0%, 1.6%, 2.0%, and 3.0%) and holding [...] Read more.

Three types of Al–5Ti master alloys were synthesized by a method of thermal explosion reaction in pure molten aluminum. Performance comparison of Al–5Ti master alloy in grain refinement of commercial purity Al with different additions (0.6%, 1.0%, 1.6%, 2.0%, and 3.0%) and holding time (10, 30, 60 and 120 min) were investigated. The results show that Al–5Ti master alloy with blocky TiAl₃ particles clearly has better refining efficiency than the master alloy with mixed TiAl₃ particles and the master alloy with needle-like TiAl₃ particles. The structures of master alloys, differing by sizes, morphologies and quantities of TiAl₃ crystals, were found to affect the pattern of the grain refining properties with the holding time. The grain refinement effect was revealed to reduce markedly for master alloys with needle–like TiAl₃ crystals and to show the further significant improvement at a longer holding time for the master alloy containing both larger needle–like and blocky TiAl₃ particles. For the master alloy with finer blocky particles, the grain refining effect did not obviously decrease during the whole studied range of the holding time. Full article

(This article belongs to the Section Advanced Materials Characterization)

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311 KiB

Open AccessReview

The Relationship between Biofilm and Physical-Chemical Properties of Implant Abutment Materials for Successful Dental Implants

by Erica Dorigatti De Avila, Rafael Scaf De Molon, Carlos Eduardo Vergani, Francisco De Assis Mollo, Jr. and Vehid Salih

Materials 2014, 7(5), 3651-3662; https://doi.org/10.3390/ma7053651 - 7 May 2014

Cited by 28 | Viewed by 8788

Abstract

The aim of this review was to investigate the relationship between biofilm and peri-implant disease, with an emphasis on the types of implant abutment surfaces. Individuals with periodontal disease typically have a large amount of pathogenic microorganisms in the periodontal pocket. If the [...] Read more.

The aim of this review was to investigate the relationship between biofilm and peri-implant disease, with an emphasis on the types of implant abutment surfaces. Individuals with periodontal disease typically have a large amount of pathogenic microorganisms in the periodontal pocket. If the individuals lose their teeth, these microorganisms remain viable inside the mouth and can directly influence peri-implant microbiota. Metal implants offer a suitable solution, but similarly, these remaining bacteria can adhere on abutment implant surfaces, induce peri-implantitis causing potential destruction of the alveolar bone near to the implant threads and cause the subsequent loss of the implant. Studies have demonstrated differences in biofilm formation on dental materials and these variations can be associated with both physical and chemical characteristics of the surfaces. In the case of partially edentulous patients affected by periodontal disease, the ideal type of implant abutments utilized should be one that adheres the least or negligible amounts of periodontopathogenic bacteria. Therefore, it is of clinically relevance to know how the bacteria behave on different types of surfaces in order to develop new materials and/or new types of treatment surfaces, which will reduce or inhibit adhesion of pathogenic microorganisms, and, thus, restrict the use of the abutments with indication propensity for bacterial adhesion. Full article

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406 KiB

Open AccessArticle

Removal of Heavy Metal Ions with Acid Activated Carbons Derived from Oil Palm and Coconut Shells

by Mokhlesur M. Rahman, Mohd Adil, Alias M. Yusof, Yunus B. Kamaruzzaman and Rezaul H. Ansary

Materials 2014, 7(5), 3634-3650; https://doi.org/10.3390/ma7053634 - 7 May 2014

Cited by 77 | Viewed by 9402

Abstract

In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid [...] Read more.

In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid under similar activation process while the differences lie either in impregnation condition or in both pretreatment and impregnation conditions. Prepared activated carbons were modified by dispersing hydrated iron oxide. The adsorption equilibrium data for nickel(II) and lead(II) were obtained from adsorption by the prepared and commercial activated carbons. Langmuir and Freundlich models fit the data well. Prepared activated carbons showed higher adsorption capacity for nickel(II) and lead(II). The removal of chromium(VI) was studied by the prepared acid activated, modified and commercial activated carbons at different pH. The isotherms studies reveal that the prepared activated carbon performs better in low concentration region while the commercial ones in the high concentration region. Thus, a complete adsorption is expected in low concentration by the prepared activated carbon. The kinetics data for Ni(II), Pb(II) and Cr(VI) by the best selected activated carbon fitted very well to the pseudo-second-order kinetic model. Full article

(This article belongs to the Section Porous Materials)

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2032 KiB

Open AccessArticle

Phosphor Deposits of β-Sialon:Eu²⁺ Mixed with SnO₂ Nanoparticles Fabricated by the Electrophoretic Deposition (EPD) Process

by Chenning Zhang, Tetsuo Uchikoshi, Lihong Liu, Yoshio Sakka and Naoto Hirosaki

Materials 2014, 7(5), 3623-3633; https://doi.org/10.3390/ma7053623 - 6 May 2014

Cited by 12 | Viewed by 6089

Abstract

The phosphor deposits of the β-sialon:Eu²⁺ mixed with various amounts (0–1 g) of the SnO₂ nanoparticles were fabricated by the electrophoretic deposition (EPD) process. The mixed SnO₂ nanoparticles was observed to cover onto the particle surfaces of the β-sialon:Eu²⁺ [...] Read more.

The phosphor deposits of the β-sialon:Eu²⁺ mixed with various amounts (0–1 g) of the SnO₂ nanoparticles were fabricated by the electrophoretic deposition (EPD) process. The mixed SnO₂ nanoparticles was observed to cover onto the particle surfaces of the β-sialon:Eu²⁺ as well as fill in the voids among the phosphor particles. The external and internal quantum efficiencies (QEs) of the prepared deposits were found to be dependent on the mixing amount of the SnO₂: by comparing with the deposit without any mixing (48% internal and 38% external QEs), after mixing the SnO₂ nanoparticles, the both QEs were improved to 55% internal and 43% external QEs at small mixing amount (0.05 g); whereas, with increasing the mixing amount to 0.1 and 1 g, they were reduced to 36% and 29% for the 0.1 g addition and 15% and 12% l QEs for the 1 g addition. More interestingly, tunable color appearances of the deposits prepared by the EPD process were achieved, from yellow green to blue, by varying the addition amount of the SnO₂, enabling it as an alternative technique instead of altering the voltage and depositing time for the color appearance controllability. Full article

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

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1230 KiB

Open AccessReview

Fabrication of Metallic Biomedical Scaffolds with the Space Holder Method: A Review

by Budi Arifvianto and Jie Zhou

Materials 2014, 7(5), 3588-3622; https://doi.org/10.3390/ma7053588 - 6 May 2014

Cited by 138 | Viewed by 16163

Abstract

Bone tissue engineering has been increasingly studied as an alternative approach to bone defect reconstruction. In this approach, new bone cells are stimulated to grow and heal the defect with the aid of a scaffold that serves as a medium for bone cell [...] Read more.

Bone tissue engineering has been increasingly studied as an alternative approach to bone defect reconstruction. In this approach, new bone cells are stimulated to grow and heal the defect with the aid of a scaffold that serves as a medium for bone cell formation and growth. Scaffolds made of metallic materials have preferably been chosen for bone tissue engineering applications where load-bearing capacities are required, considering the superior mechanical properties possessed by this type of materials to those of polymeric and ceramic materials. The space holder method has been recognized as one of the viable methods for the fabrication of metallic biomedical scaffolds. In this method, temporary powder particles, namely space holder, are devised as a pore former for scaffolds. In general, the whole scaffold fabrication process with the space holder method can be divided into four main steps: (i) mixing of metal matrix powder and space-holding particles; (ii) compaction of granular materials; (iii) removal of space-holding particles; (iv) sintering of porous scaffold preform. In this review, detailed procedures in each of these steps are presented. Technical challenges encountered during scaffold fabrication with this specific method are addressed. In conclusion, strategies are yet to be developed to address problematic issues raised, such as powder segregation, pore inhomogeneity, distortion of pore sizes and shape, uncontrolled shrinkage and contamination. Full article

(This article belongs to the Special Issue Light Alloys and Their Applications)

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2459 KiB

Open AccessReview

A Review of Polymer-Stabilized Ferroelectric Liquid Crystals

by Ingo Dierking

Materials 2014, 7(5), 3568-3587; https://doi.org/10.3390/ma7053568 - 6 May 2014

Cited by 37 | Viewed by 9334

Abstract

The polymer stabilized state of ferroelectric liquid crystals (FLC) is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as [...] Read more.

The polymer stabilized state of ferroelectric liquid crystals (FLC) is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as well as the dielectric modes. It was found that the data can largely be explained by assuming an elastic interaction between the polymer network strands and the liquid crystal molecules. The elastic interaction parameter was determined; and increases linearly with increasing polymer concentration. Full article

(This article belongs to the Special Issue Liquid Crystals)

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386 KiB

Open AccessArticle

Influence of Column Axial Load and Heat Affected Zone on the Strength of Aluminium Column Web in Tension

by Gianfranco De Matteis, Gianluca Sarracco, Giuseppe Brando and Federico M. Mazzolani

Materials 2014, 7(5), 3557-3567; https://doi.org/10.3390/ma7053557 - 6 May 2014

Cited by 7 | Viewed by 7079

Abstract

The component method for aluminium joints has been recently introduced in some codes and guidelines. Nevertheless, it is still in need of some development and improvement, as in some cases it was obtained by adapting the existing formulations that are valid for steel. [...] Read more.

The component method for aluminium joints has been recently introduced in some codes and guidelines. Nevertheless, it is still in need of some development and improvement, as in some cases it was obtained by adapting the existing formulations that are valid for steel. The current paper presents the main outcomes of a parametric analysis carried out by means of finite element (FE) numerical models for determining the influence of both column axial load and heat affected zone—in the case of welded details—on the structural response of the column web in a tension component. The proposed study integrates previous research carried out by the authors, where the influence of the assumed alloy was investigated and interpreted by corrective parameters expressed as a function of both the material strain hardening and ductility. Full article

(This article belongs to the Special Issue Selected Papers from the International Aluminium Conference (INALCO) 2013)

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Materials, Volume 7, Issue 5 (May 2014) – 45 articles , Pages 3337-4087

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