Next Issue
Previous Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

Materials, Volume 9, Issue 10 (October 2016)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Cover Story Human mesenchymal stem cells (MSCs), cultured on ultra-short pulsed laser deposited TiO2-based [...] Read more.
View options order results:
result details:
Displaying articles 1-66
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessArticle Comparative Study on Crack Initiation and Propagation of Glass under Thermal Loading
Materials 2016, 9(10), 794; doi:10.3390/ma9100794
Received: 6 July 2016 / Revised: 7 September 2016 / Accepted: 14 September 2016 / Published: 22 September 2016
Cited by 1 | PDF Full-text (6238 KB) | HTML Full-text | XML Full-text
Abstract
This paper explores the fracture process based on finite element simulation. Both probabilistic and deterministic methods are employed to model crack initiation, and several commonly used criteria are utilized to predict crack growth. It is concluded that the criteria of maximum tensile stress,
[...] Read more.
This paper explores the fracture process based on finite element simulation. Both probabilistic and deterministic methods are employed to model crack initiation, and several commonly used criteria are utilized to predict crack growth. It is concluded that the criteria of maximum tensile stress, maximum normal stress, and maximum Mises stress, as well as the Coulomb-Mohr criterion are able to predict the initiation of the first crack. The mixed-mode criteria based on the stress intensity factor (SIF), energy release rate, and the maximum principal stress, as well as the SIF-based maximum circumferential stress criterion are suitable to predict the crack propagation. Full article
Figures

Figure 1

Open AccessArticle Improved Tribological Performance of Amorphous Carbon (a-C) Coating by ZrO2 Nanoparticles
Materials 2016, 9(10), 795; doi:10.3390/ma9100795
Received: 23 July 2016 / Revised: 1 September 2016 / Accepted: 14 September 2016 / Published: 22 September 2016
Cited by 1 | PDF Full-text (8280 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Nanomaterials, such as Graphene, h-BN nanoparticles and MoS2 nanotubes, have shown their ability in improving the tribological performance of amorphous carbon (a-C) coatings. In the current study, the effectiveness of ZrO2 nanoparticles (ZrO2-NPs) in lubricating the self-mated nonhydrogenated a-C
[...] Read more.
Nanomaterials, such as Graphene, h-BN nanoparticles and MoS2 nanotubes, have shown their ability in improving the tribological performance of amorphous carbon (a-C) coatings. In the current study, the effectiveness of ZrO2 nanoparticles (ZrO2-NPs) in lubricating the self-mated nonhydrogenated a-C contacts was investigated in boundary lubrication regime. The results showed that 13% less friction and 50% less wear compared to the base oil were achieved by employing ZrO2-NPs in the base oil in self-mated a-C contacts. Via analyzing the ZrO2-NPs and the worn a-C surface after tests, it was found that the improved lubrication by ZrO2-NPs was based on “polishing effects”, which is a new phenomenon observed between a-C and nanoparticles. Under the “polishing effect”, micro-plateaus with extremely smooth surface and uniform height were produced on the analyzed a-C surface. The resulting topography of the a-C coating is suitable for ZrO2-NPs to act as nano-bearings between rubbing surfaces. Especially, the ZrO2-NPs exhibited excellent mechanical and chemical stability, even under the severe service condition, suggesting that the combination of nonhydrogenated a-C coating with ZrO2-NPs is an effective, long lasting and environment-friendly lubrication solution. Full article
(This article belongs to the Special Issue Tribological Behavior of Materials by Surface Engineering)
Figures

Figure 1

Open AccessArticle Correlation Factor Study of Small Punch Creep Test and Its Life Prediction
Materials 2016, 9(10), 796; doi:10.3390/ma9100796
Received: 8 August 2016 / Revised: 16 September 2016 / Accepted: 19 September 2016 / Published: 24 September 2016
Cited by 2 | PDF Full-text (2770 KB) | HTML Full-text | XML Full-text
Abstract
A small punch test is one of the innovative methods that can be used to evaluate the properties of a material without destructive harm to the in-service component. Conventionally identifying material properties by a uniaxial test is widely applied to engineering. How the
[...] Read more.
A small punch test is one of the innovative methods that can be used to evaluate the properties of a material without destructive harm to the in-service component. Conventionally identifying material properties by a uniaxial test is widely applied to engineering. How the properties obtained from a small punch test can be applied with the same utility has been a goal. In 2006, European Code of Practice (CoP) of small punch tests was first released, in which the correlation factor, ksp, was introduced to bridge the gap between the above methods. The author investigates the relationship between a uniaxial creep text and a small punch creep test by exploring the correlation factor ksp. Various sets of experiments and a comparative study of the conventional uniaxial creep test and small punch creep test were carried out. Methods including Norton, Larson-Miller and Time versus Stress relation were employed to identify the value of ksp. Different ksp values were found in different materials, which indicate that ksp values of materials need to be identified separately. In addition, the life prediction of a small punch creep test was carried out and the results of the life prediction predict a reasonable accuracy, which indicates that the small punch creep test is a reliable method for life prediction. Full article
(This article belongs to the Special Issue Selected Papers from SSTT2016)
Figures

Figure 1

Open AccessArticle Synthesis and Characterization of Types A and B Gelatin Methacryloyl for Bioink Applications
Materials 2016, 9(10), 797; doi:10.3390/ma9100797
Received: 7 August 2016 / Revised: 14 September 2016 / Accepted: 20 September 2016 / Published: 24 September 2016
Cited by 3 | PDF Full-text (5701 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Gelatin methacryloyl (GelMA) has been increasingly considered as an important bioink material due to its tailorable mechanical properties, good biocompatibility, and ability to be photopolymerized in situ as well as printability. GelMA can be classified into two types: type A GelMA (a product
[...] Read more.
Gelatin methacryloyl (GelMA) has been increasingly considered as an important bioink material due to its tailorable mechanical properties, good biocompatibility, and ability to be photopolymerized in situ as well as printability. GelMA can be classified into two types: type A GelMA (a product from acid treatment) and type B GelMA (a product from alkali treatment). In current literature, there is little research on the comparison of type A GelMA and type B GelMA in terms of synthesis, rheological properties, and printability for bioink applications. Here, we report the synthesis, rheological properties, and printability of types A and B GelMA. Types A and B GelMA samples with different degrees of substitution (DS) were prepared in a controllable manner by a time-lapse loading method of methacrylic anhydride (MAA) and different feed ratios of MAA to gelatin. Type B GelMA tended to have a slightly higher DS compared to type A GelMA, especially in a lower feed ratio of MAA to gelatin. All the type A and type B GelMA solutions with different DS exhibited shear thinning behaviours at 37 °C. However, only GelMA with a high DS had an easy-to-extrude feature at room temperature. The cell-laden printed constructs of types A and B GelMA at 20% w/v showed around 75% cell viability. Full article
(This article belongs to the Special Issue 3D Printing for Biomedical Engineering)
Figures

Figure 1

Open AccessArticle High-Speed Edge Trimming of CFRP and Online Monitoring of Performance of Router Tools Using Acoustic Emission
Materials 2016, 9(10), 798; doi:10.3390/ma9100798
Received: 16 June 2016 / Revised: 6 September 2016 / Accepted: 19 September 2016 / Published: 26 September 2016
Cited by 1 | PDF Full-text (9294 KB) | HTML Full-text | XML Full-text
Abstract
Carbon fiber reinforced polymers (CFRPs) have found wide-ranging applications in numerous industrial fields such as aerospace, automotive, and shipping industries due to their excellent mechanical properties that lead to enhanced functional performance. In this paper, an experimental study on edge trimming of CFRP
[...] Read more.
Carbon fiber reinforced polymers (CFRPs) have found wide-ranging applications in numerous industrial fields such as aerospace, automotive, and shipping industries due to their excellent mechanical properties that lead to enhanced functional performance. In this paper, an experimental study on edge trimming of CFRP was done with various cutting conditions and different geometry of tools such as helical-, fluted-, and burr-type tools. The investigation involves the measurement of cutting forces for the different machining conditions and its effect on the surface quality of the trimmed edges. The modern cutting tools (router tools or burr tools) selected for machining CFRPs, have complex geometries in cutting edges and surfaces, and therefore a traditional method of direct tool wear evaluation is not applicable. An acoustic emission (AE) sensing was employed for on-line monitoring of the performance of router tools to determine the relationship between AE signal and length of machining for different kinds of geometry of tools. The investigation showed that the router tool with a flat cutting edge has better performance by generating lower cutting force and better surface finish with no delamination on trimmed edges. The mathematical modeling for the prediction of cutting forces was also done using Artificial Neural Network and Regression Analysis. Full article
(This article belongs to the Special Issue Machining of Composites and Multi-Stacks of Aerospace Materials)
Figures

Figure 1

Open AccessArticle Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime
Materials 2016, 9(10), 799; doi:10.3390/ma9100799
Received: 20 August 2016 / Revised: 11 September 2016 / Accepted: 22 September 2016 / Published: 26 September 2016
Cited by 1 | PDF Full-text (6061 KB) | HTML Full-text | XML Full-text
Abstract
As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution
[...] Read more.
As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin2ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement. Full article
(This article belongs to the Special Issue Selected Papers from IS3C2016)
Figures

Figure 1

Open AccessArticle Inclined Fiber Pullout from a Cementitious Matrix: A Numerical Study
Materials 2016, 9(10), 800; doi:10.3390/ma9100800
Received: 30 August 2016 / Revised: 19 September 2016 / Accepted: 20 September 2016 / Published: 26 September 2016
Cited by 1 | PDF Full-text (3999 KB) | HTML Full-text | XML Full-text
Abstract
It is well known that fibers improve the performance of cementitious composites by acting as bridging ligaments in cracks. Such bridging behavior is often studied through fiber pullout tests. The relation between the pullout force vs. slip end displacement is characteristic of the
[...] Read more.
It is well known that fibers improve the performance of cementitious composites by acting as bridging ligaments in cracks. Such bridging behavior is often studied through fiber pullout tests. The relation between the pullout force vs. slip end displacement is characteristic of the fiber-matrix interface. However, such a relation varies significantly with the fiber inclination angle. In the current work, we establish a numerical model to simulate the entire pullout process by explicitly representing the fiber, matrix and the interface for arbitrary fiber orientations. Cohesive elements endorsed with mixed-mode fracture capacities are implemented to represent the bond-slip behavior at the interface. Contact elements with Coulomb’s friction are placed at the interface to simulate frictional contact. The bond-slip behavior is first calibrated through pull-out curves for fibers aligned with the loading direction, then validated against experimental results for steel fibers oriented at 30 and 60 . Parametric studies are then performed to explore the influences of both material properties (fiber yield strength, matrix tensile strength, interfacial bond) and geometric factors (fiber diameter, embedment length and inclination angle) on the overall pullout behavior, in particular on the maximum pullout load. The proposed methodology provides the necessary pull-out curves for a fiber oriented at a given angle for multi-scale models to study fracture in fiber-reinforced cementitious materials. The novelty lies in its capacity to capture the entire pullout process for a fiber with an arbitrary inclination angle. Full article
(This article belongs to the Special Issue Multiscale Methods and Application to Computational Materials Design)
Figures

Figure 1

Open AccessArticle The Structural, Photocatalytic Property Characterization and Enhanced Photocatalytic Activities of Novel Photocatalysts Bi2GaSbO7 and Bi2InSbO7 during Visible Light Irradiation
Materials 2016, 9(10), 801; doi:10.3390/ma9100801
Received: 29 July 2016 / Revised: 18 September 2016 / Accepted: 21 September 2016 / Published: 27 September 2016
PDF Full-text (3917 KB) | HTML Full-text | XML Full-text
Abstract
In order to develop original and efficient visible light response photocatalysts for degrading organic pollutants in wastewater, new photocatalysts Bi2GaSbO7 and Bi2InSbO7 were firstly synthesized by a solid-state reaction method and their chemical, physical and structural properties
[...] Read more.
In order to develop original and efficient visible light response photocatalysts for degrading organic pollutants in wastewater, new photocatalysts Bi2GaSbO7 and Bi2InSbO7 were firstly synthesized by a solid-state reaction method and their chemical, physical and structural properties were characterized. Bi2GaSbO7 and Bi2InSbO7 were crystallized with a pyrochlore-type structure and the lattice parameter of Bi2GaSbO7 or Bi2InSbO7 was 10.356497 Å or 10.666031 Å. The band gap of Bi2GaSbO7 or Bi2InSbO7 was estimated to be 2.59 eV or 2.54 eV. Compared with nitrogen doped TiO2, Bi2GaSbO7 and Bi2InSbO7, both showed excellent photocatalytic activities for degrading methylene blue during visible light irradiation due to their narrower band gaps and higher crystallization perfection. Bi2GaSbO7 showed higher catalytic activity compared with Bi2InSbO7. The photocatalytic degradation of methylene blue followed by the first-order reaction kinetics and the first-order rate constant was 0.01470 min−1, 0.00967 min−1 or 0.00259 min−1 with Bi2GaSbO7, Bi2InSbO7 or nitrogen doped TiO2 as a catalyst. The evolution of CO2 and the removal of total organic carbon were successfully measured and these results indicated continuous mineralization of methylene blue during the photocatalytic process. The possible degradation scheme and pathway of methylene blue was also analyzed. Bi2GaSbO7 and Bi2InSbO7 photocatalysts both had great potential to purify textile industry wastewater. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Figures

Open AccessArticle Room Temperature Electroluminescence from Tensile-Strained Si0.13Ge0.87/Ge Multiple Quantum Wells on a Ge Virtual Substrate
Materials 2016, 9(10), 803; doi:10.3390/ma9100803
Received: 26 July 2016 / Revised: 13 September 2016 / Accepted: 14 September 2016 / Published: 27 September 2016
Cited by 2 | PDF Full-text (4729 KB) | HTML Full-text | XML Full-text
Abstract
Direct band electroluminescence (EL) from tensile-strained Si0.13Ge0.87/Ge multiple quantum wells (MQWs) on a Ge virtual substrate (VS) at room temperature is reported herein. Due to the competitive result of quantum confinement Stark effect and bandgap narrowing induced by tensile
[...] Read more.
Direct band electroluminescence (EL) from tensile-strained Si0.13Ge0.87/Ge multiple quantum wells (MQWs) on a Ge virtual substrate (VS) at room temperature is reported herein. Due to the competitive result of quantum confinement Stark effect and bandgap narrowing induced by tensile strain in Ge wells, electroluminescence from Γ1-HH1 transition in 12-nm Ge wells was observed at around 1550 nm. As injection current density increases, additional emission shoulders from Γ2-HH2 transition in Ge wells and Ge VS appeared at around 1300–1400 nm and 1600–1700 nm, respectively. The peak energy of EL shifted to the lower energy side superquadratically with an increase of injection current density as a result of the Joule heating effect. During the elevation of environmental temperature, EL intensity increased due to a reduction of energy between L and Γ valleys of Ge. Empirical fitting of the relationship between the integrated intensity of EL (L) and injection current density (J) with L~Jm shows that the m factor increased with injection current density, suggesting higher light emitting efficiency of the diode at larger injection current densities, which can be attributed to larger carrier occupations in the Γ valley and the heavy hole (HH) valance band at higher temperatures. Full article
(This article belongs to the Special Issue Silicon Nanophotonics)
Figures

Figure 1

Open AccessArticle Analysis of Minimum Quantity Lubrication (MQL) for Different Coating Tools during Turning of TC11 Titanium Alloy
Materials 2016, 9(10), 804; doi:10.3390/ma9100804
Received: 6 July 2016 / Revised: 12 September 2016 / Accepted: 12 September 2016 / Published: 28 September 2016
Cited by 2 | PDF Full-text (12469 KB) | HTML Full-text | XML Full-text
Abstract
The tool coating and cooling strategy are two key factors when machining difficult-to-cut materials such as titanium alloy. In this paper, diamond coating was deposited on a commercial carbide insert as an attempt to increase the machinability of TC11 alloy during the turning
[...] Read more.
The tool coating and cooling strategy are two key factors when machining difficult-to-cut materials such as titanium alloy. In this paper, diamond coating was deposited on a commercial carbide insert as an attempt to increase the machinability of TC11 alloy during the turning process. An uncoated carbide insert and a commercial Al2O3/TiAlN-coated tool were also tested as a comparison. Furthermore, MQL was applied to improve the cutting condition. Cutting performances were analyzed by cutting force, cutting temperate and surface roughness measurements. Tool wears and tool lives were evaluated to find a good matchup between the tool coating and cooling strategy. According to the results, using MQL can slightly reduce the cutting force. By applying MQL, cutting temperatures and tool wears were reduced by a great amount. Besides, MQL can affect the tool wear mechanism and tool failure modes. The tool life of an Al2O3/TiAlN-coated tool can be prolonged by 88.4% under the MQL condition. Diamond-coated tools can obtain a good surface finish when cutting parameters and lubrication strategies are properly chosen. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Figures

Figure 1

Open AccessArticle Optical and Piezoelectric Study of KNN Solid Solutions Co-Doped with La-Mn and Eu-Fe
Materials 2016, 9(10), 805; doi:10.3390/ma9100805
Received: 15 July 2016 / Revised: 10 August 2016 / Accepted: 22 September 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (10401 KB) | HTML Full-text | XML Full-text
Abstract
The solid-state method was used to synthesize single phase potassium-sodium niobate (KNN) co-doped with the La3+–Mn4+ and Eu3+–Fe3+ ion pairs. Structural determination of all studied solid solutions was accomplished by XRD and Rietveld refinement method. Electron paramagnetic
[...] Read more.
The solid-state method was used to synthesize single phase potassium-sodium niobate (KNN) co-doped with the La3+–Mn4+ and Eu3+–Fe3+ ion pairs. Structural determination of all studied solid solutions was accomplished by XRD and Rietveld refinement method. Electron paramagnetic resonance (EPR) studies were performed to determine the oxidation state of paramagnetic centers. Optical spectroscopy measurements, excitation, emission and decay lifetime were carried out for each solid solution. The present study reveals that doping KNN with La3+–Mn4+ and Eu3+–Fe3+ at concentrations of 0.5 mol % and 1 mol %, respectively, improves the ferroelectric and piezoelectric behavior and induce the generation of optical properties in the material for potential applications. Full article
(This article belongs to the Section Materials for Energy Applications)
Figures

Figure 1

Open AccessArticle Solvothermal Synthesis of Hierarchical Colloidal Nanocrystal Assemblies of ZnFe2O4 and Their Application in Water Treatment
Materials 2016, 9(10), 806; doi:10.3390/ma9100806
Received: 15 July 2016 / Revised: 5 September 2016 / Accepted: 20 September 2016 / Published: 29 September 2016
Cited by 2 | PDF Full-text (2218 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hierarchical colloidal nanocrystal assemblies (CNAs) of ZnFe2O4 have been synthesized controllably by a solvothermal method. Hollow ZnFe2O4 spheres can be formed with the volume ratios of ethylene glycol to ethanol of 1:4 in the starting systems, while
[...] Read more.
Hierarchical colloidal nanocrystal assemblies (CNAs) of ZnFe2O4 have been synthesized controllably by a solvothermal method. Hollow ZnFe2O4 spheres can be formed with the volume ratios of ethylene glycol to ethanol of 1:4 in the starting systems, while solid ZnFe2O4 CNAs are obtained by adjusting the volume proportion of ethylene glycol to ethanol from 1:2 to 2:1. Magnetometric measurement data showed that the ZnFe2O4 CNAs obtained with the volume ratios of 1:2 and 1:1 exhibited weak ferromagnetic behavior with high saturation magnetization values of 60.4 and 60.3 emu·g−1, respectively. However, hollow spheres showed a saturation magnetization value of 52.0 emu·g−1, but the highest coercivity among all the samples. It was found that hollow spheres displayed the best ability to adsorb Congo red dye among all the CNAs. The formation mechanisms of ZnFe2O4 CNAs, as well as the relationship between their structure, crystallite size, and properties were discussed based on the experimental results. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
Figures

Figure 1

Open AccessArticle Multi-Layered TiO2 Films towards Enhancement of Escherichia coli Inactivation
Materials 2016, 9(10), 808; doi:10.3390/ma9100808
Received: 10 August 2016 / Revised: 13 September 2016 / Accepted: 26 September 2016 / Published: 30 September 2016
Cited by 1 | PDF Full-text (4352 KB) | HTML Full-text | XML Full-text
Abstract
Crystalline TiO2 has shown its great photocatalytic properties in bacterial inactivation. This work presents a design fabrication of low-cost, layered TiO2 films assembled reactors and a study of their performance for a better understanding to elucidate the photocatalytic effect on inactivation
[...] Read more.
Crystalline TiO2 has shown its great photocatalytic properties in bacterial inactivation. This work presents a design fabrication of low-cost, layered TiO2 films assembled reactors and a study of their performance for a better understanding to elucidate the photocatalytic effect on inactivation of E. coli in water. The ability to reduce the number of bacteria in water samples for the layered TiO2 composing reactors has been investigated as a function of time, while varying the parameters of light sources, initial concentration of bacteria, and ratios of TiO2 film area and volume of water. Herein, the layered TiO2 films have been fabricated on the glass plates by thermal spray coating prior to screen printing, allowing a good adhesion of the films. Surface topology and crystallographic phase of TiO2 for the screen-printed active layer have been characterized, resulting in the ratio of anatase:rutile being 80:20. Under exposure to sunlight and a given condition employed in this study, the optimized film area:water volume of 1:2.62 has shown a significant ability to reduce the E. coli cells in water samples. The ratio of surface area of photocatalytic active base to volume of water medium is believed to play a predominant role facilitating the cells inactivation. The kinetic rate of inactivation and its behavior are also described in terms of adsorption of reaction species at different contact times. Full article
Figures

Figure 1

Open AccessArticle Synthesis of Copper Nanoparticles in Ethylene Glycol by Chemical Reduction with Vanadium (+2) Salts
Materials 2016, 9(10), 809; doi:10.3390/ma9100809
Received: 31 July 2016 / Revised: 18 September 2016 / Accepted: 26 September 2016 / Published: 29 September 2016
Cited by 1 | PDF Full-text (2572 KB) | HTML Full-text | XML Full-text
Abstract
Copper nanoparticles have been synthesized in ethylene glycol (EG) using copper sulphate as a precursor and vanadium sulfate as an atypical reductant being active at room temperature. We have described a technique for a relatively simple preparation of such a reagent, which has
[...] Read more.
Copper nanoparticles have been synthesized in ethylene glycol (EG) using copper sulphate as a precursor and vanadium sulfate as an atypical reductant being active at room temperature. We have described a technique for a relatively simple preparation of such a reagent, which has been electrolytically produced without using standard procedures requiring an inert atmosphere and a mercury cathode. Several stabilizing agents have been tested and cationic capping agents have been discarded owing to the formation of complex compounds with copper ions leading to insoluble phases contaminating the metallic nanoparticles. The elemental copper nanoparticles, stabilized with polyvinylpyrrolidone (PVP) and sodium dodecyl sulphate (SDS), have been characterized for composition by energy dispersive X-ray spectroscopy (EDS), and for size by dynamic light scattering (DLS), and transmission electron microscopy (TEM), giving a size distribution in the range of 40–50 nm for both stabilizing agents. From a methodological point of view, the process described here may represent an alternative to other wet-chemical techniques for metal nanoparticle synthesis in non-aqueous media based on conventional organic or inorganic reductants. Full article
Figures

Figure 1

Open AccessArticle Charged Triazole Cross-Linkers for Hyaluronan-Based Hybrid Hydrogels
Materials 2016, 9(10), 810; doi:10.3390/ma9100810
Received: 28 July 2016 / Revised: 13 September 2016 / Accepted: 23 September 2016 / Published: 30 September 2016
Cited by 2 | PDF Full-text (1164 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polyelectrolyte hydrogels play an important role in tissue engineering and can be produced from natural polymers, such as the glycosaminoglycan hyaluronan. In order to control charge density and mechanical properties of hyaluronan-based hydrogels, we developed cross-linkers with a neutral or positively charged triazole
[...] Read more.
Polyelectrolyte hydrogels play an important role in tissue engineering and can be produced from natural polymers, such as the glycosaminoglycan hyaluronan. In order to control charge density and mechanical properties of hyaluronan-based hydrogels, we developed cross-linkers with a neutral or positively charged triazole core with different lengths of spacer arms and two terminal maleimide groups. These cross-linkers react with thiolated hyaluronan in a fast, stoichiometric thio-Michael addition. Introducing a positive charge on the core of the cross-linker enabled us to compare hydrogels with the same interconnectivity, but a different charge density. Positively charged cross-linkers form stiffer hydrogels relatively independent of the size of the cross-linker, whereas neutral cross-linkers only form stable hydrogels at small spacer lengths. These novel cross-linkers provide a platform to tune the hydrogel network charge and thus the mechanical properties of the network. In addition, they might offer a wide range of applications especially in bioprinting for precise design of hydrogels. Full article
(This article belongs to the Special Issue Smart Hydrogels for (Bio)printing Applications)
Figures

Figure 1

Open AccessArticle µXRF Elemental Mapping of Bioresorbable Magnesium-Based Implants in Bone
Materials 2016, 9(10), 811; doi:10.3390/ma9100811
Received: 20 August 2016 / Revised: 24 September 2016 / Accepted: 26 September 2016 / Published: 30 September 2016
PDF Full-text (5991 KB) | HTML Full-text | XML Full-text
Abstract
This study investigated the distribution of the elemental constituents of Mg-based implants at various stages of the degradation process in surrounding bone tissue, with a focus on magnesium (Mg), as the main component of the alloy, and yttrium (Y), due to its potential
[...] Read more.
This study investigated the distribution of the elemental constituents of Mg-based implants at various stages of the degradation process in surrounding bone tissue, with a focus on magnesium (Mg), as the main component of the alloy, and yttrium (Y), due to its potential adverse health effects. The measurements were performed on the implant-bearing thin sections of rat bone in a time series of implant degradation between one and 18 months. Micro X-ray fluorescence analysis (μXRF) with a special spectrometer meeting the requirements for the measurements of low-Z elements was used. It was found that the migration and accumulation behaviour of implant degradation products is element-specific. A sharp decrease in Mg was observed in the immediate vicinity of the interface and no specific accumulation or aggregation of Mg in the adjacent bone tissue was detected. By contrast, Y was found to migrate further into the bone over time and to remain in the tissue even after the complete degradation of the implant. Although the nature of Y accumulations must still be clarified, its potential health impact should be considered. Full article
(This article belongs to the Special Issue Degradable Biomaterials Based on Magnesium Alloys)
Figures

Figure 1

Open AccessArticle Conductive Polymer Synthesis with Single-Crystallinity via a Novel Plasma Polymerization Technique for Gas Sensor Applications
Materials 2016, 9(10), 812; doi:10.3390/ma9100812
Received: 7 July 2016 / Revised: 13 September 2016 / Accepted: 26 September 2016 / Published: 30 September 2016
Cited by 5 | PDF Full-text (6175 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes a new nanostructured conductive polymer synthesis method that can grow the single-crystalline high-density plasma-polymerized nanoparticle structures by enhancing the sufficient nucleation and fragmentation of the pyrrole monomer using a novel atmospheric pressure plasma jet (APPJ) technique. Transmission electron microscopy (TEM),
[...] Read more.
This study proposes a new nanostructured conductive polymer synthesis method that can grow the single-crystalline high-density plasma-polymerized nanoparticle structures by enhancing the sufficient nucleation and fragmentation of the pyrrole monomer using a novel atmospheric pressure plasma jet (APPJ) technique. Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM) results show that the plasma-polymerized pyrrole (pPPy) nanoparticles have a fast deposition rate of 0.93 µm·min−1 under a room-temperature process and have single-crystalline characteristics with porous properties. In addition, the single-crystalline high-density pPPy nanoparticle structures were successfully synthesized on the glass, plastic, and interdigitated gas sensor electrode substrates using a novel plasma polymerization technique at room temperature. To check the suitability of the active layer for the fabrication of electrochemical toxic gas sensors, the resistance variations of the pPPy nanoparticles grown on the interdigitated gas sensor electrodes were examined by doping with iodine. As a result, the proposed APPJ device could obtain the high-density and ultra-fast single-crystalline pPPy thin films for various gas sensor applications. This work will contribute to the design of highly sensitive gas sensors adopting the novel plasma-polymerized conductive polymer as new active layer. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Figures

Figure 1

Open AccessArticle An Experimental and Theoretical Investigation of the Electronic Structures and Photoelectrical Properties of Ethyl Red and Carminic Acid for DSSC Application
Materials 2016, 9(10), 813; doi:10.3390/ma9100813
Received: 14 August 2016 / Revised: 21 September 2016 / Accepted: 27 September 2016 / Published: 1 October 2016
Cited by 1 | PDF Full-text (4416 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The photoelectrical properties of two dyes—ethyl red and carminic acid—as sensitizers of dye-sensitized solar cells were investigated in experiments herein described. In order to reveal the reason for the difference between the photoelectrical properties of the two dyes, the ground state and excited
[...] Read more.
The photoelectrical properties of two dyes—ethyl red and carminic acid—as sensitizers of dye-sensitized solar cells were investigated in experiments herein described. In order to reveal the reason for the difference between the photoelectrical properties of the two dyes, the ground state and excited state properties of the dyes before and after adsorbed on TiO2 were calculated via density functional theory (DFT) and time-dependent DFT (TDDFT). The key parameters including the light harvesting efficiency (LHE), the driving force of electron injection ( Δ G inject ) and dye regeneration ( Δ G regen ), the total dipole moment ( μ normal ), the conduction band of edge of the semiconductor ( Δ E CB ), and the excited state lifetime (τ) were investigated, which are closely related to the short-circuit current density ( J sc ) and open circuit voltage ( V oc ). It was found that the experimental carminic acid has a larger J sc and V oc , which are interpreted by a larger amount of dye adsorbed on a TiO2 photoanode and a larger Δ G regen , excited state lifetime (τ), μ normal , and Δ E CB . At the same time, chemical reactivity parameters illustrate that the lower chemical hardness (h) and higher electron accepting power (ω+) of carminic acid have an influence on the short-circuit current density. Therefore, carminic acid shows excellent photoelectric conversion efficiency in comparison with ethyl red. Full article
(This article belongs to the Section Materials for Energy Applications)
Figures

Open AccessArticle A Numerical Investigation of the Thermal Stresses of a Planar Solid Oxide Fuel Cell
Materials 2016, 9(10), 814; doi:10.3390/ma9100814
Received: 27 July 2016 / Revised: 31 August 2016 / Accepted: 19 September 2016 / Published: 30 September 2016
Cited by 1 | PDF Full-text (9205 KB) | HTML Full-text | XML Full-text
Abstract
A typical operating temperature of a solid oxide fuel cell (SOFC) is quite high above 750 °C and affects the thermomechanical behavior of the cell. Thermal stresses may cause microstructural instability and sub-critical cracking. Therefore, a joint analysis by the computational fluid dynamics
[...] Read more.
A typical operating temperature of a solid oxide fuel cell (SOFC) is quite high above 750 °C and affects the thermomechanical behavior of the cell. Thermal stresses may cause microstructural instability and sub-critical cracking. Therefore, a joint analysis by the computational fluid dynamics (CFD) and computational structural mechanics based on the finite element method (FEM) was carried out to analyze thermal stresses in a planar SOFC and to predict potential failure locations in the cell. A full numerical model was based on the coupling of thermo-fluid model with the thermo-mechanical model. Based on a temperature distribution from the thermo-fluid model, stress distribution including the von Mises stress, shear stress as well as the operating principal stress were derived in the thermo-mechanical model. The FEM calculations were performed under different working conditions of the planar SOFC. The highest total stress was noticed at the lower operating voltage of 0.3 V, while the lowest total stress was determined at the voltage of 0.7 V. The obtained stress distributions allowed a better understanding of details of internal processes occurring within the SOFC and provided helpful guidance in the optimization of a new SOFC design. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Figures

Figure 1

Open AccessArticle TiC Reinforcement Composite Coating Produced Using Graphite of the Cast Iron by Laser Cladding
Materials 2016, 9(10), 815; doi:10.3390/ma9100815
Received: 25 August 2016 / Revised: 26 September 2016 / Accepted: 26 September 2016 / Published: 30 September 2016
Cited by 1 | PDF Full-text (13359 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a TiC-reinforced composite coating was produced to improve the wear resistance of a pearlite matrix grey iron using a pre-placed Ti powder by laser cladding. Results of scanning electron microscopy (SEM), X-ray diffractometer (XRD), and energy dispersive X-ray spectroscopy (EDS)
[...] Read more.
In this study, a TiC-reinforced composite coating was produced to improve the wear resistance of a pearlite matrix grey iron using a pre-placed Ti powder by laser cladding. Results of scanning electron microscopy (SEM), X-ray diffractometer (XRD), and energy dispersive X-ray spectroscopy (EDS) confirmed that the coating was composed of TiC particles and two kinds of α-Fe phase. The fine TiC particles were only a few microns in size and uniformly distributed on the matrix phase in the composite coating. The microstructure characteristic of the composite coating resulted in the microhardness rising to about 1000 HV0.3 (China GB/T 4342-1991) and the wear resistance significantly increased relative to the substrate. In addition, the fine and homogeneous solidification microstructure without graphite phase in the transition zone led to a good metallurgical bonding and transition between the coating and the substrate. It was of great significance for the cast iron to modify the surface and repair surface defects or surface damage. Full article
Figures

Open AccessArticle Preparation and Characterization of Chitosan—Agarose Composite Films
Materials 2016, 9(10), 816; doi:10.3390/ma9100816
Received: 16 August 2016 / Revised: 15 September 2016 / Accepted: 19 September 2016 / Published: 30 September 2016
Cited by 5 | PDF Full-text (949 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, there is a growing interest to develop biodegradable functional composite materials for food packaging and biomedicine applications from renewable sources. Some composite films were prepared by the casting method using chitosan (CS) and agarose (AG) in different mass ratios. The composite films
[...] Read more.
Nowadays, there is a growing interest to develop biodegradable functional composite materials for food packaging and biomedicine applications from renewable sources. Some composite films were prepared by the casting method using chitosan (CS) and agarose (AG) in different mass ratios. The composite films were analyzed for physical-chemical-mechanical properties including tensile strength (TS), elongation-at-break (EB), water vapor transmission rate (WVTR), swelling ratio, Fourier-transform infrared spectroscopy, and morphology observations. The antibacterial properties of the composite films were also evaluated. The obtained results reveal that an addition of AG in varied proportions to a CS solution leads to an enhancement of the composite film’s tensile strength, elongation-at-break, and water vapor transmission rate. The composite film with an agarose mass concentration of 60% was of the highest water uptake capacity. These improvements can be explained by the chemical structures of the new composite films, which contain hydrogen bonding interactions between the chitosan and agarose as shown by Fourier-transform infrared spectroscopy (FTIR) analysis and the micro-pore structures as observed with optical microscopes and scanning electron microscopy (SEM). The antibacterial results demonstrated that the films with agarose mass concentrations ranging from 0% to 60% possessed antibacterial properties. These results indicate that these composite films, especially the composite film with an agarose mass concentration of 60%, exhibit excellent potential to be used in food packaging and biomedical materials. Full article
Figures

Figure 1

Open AccessArticle Mesquite Gum as a Novel Reducing and Stabilizing Agent for Modified Tollens Synthesis of Highly Concentrated Ag Nanoparticles
Materials 2016, 9(10), 817; doi:10.3390/ma9100817
Received: 31 July 2016 / Accepted: 26 September 2016 / Published: 4 October 2016
Cited by 1 | PDF Full-text (4483 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The synthesis that is described in this study is for the preparation of silver nanoparticles of sizes ranging from 10 nm to 30 nm with a defined shape (globular), confirmed by UV-vis, SEM, STEM and DLS analysis. This simple and favorable one-step modified
[...] Read more.
The synthesis that is described in this study is for the preparation of silver nanoparticles of sizes ranging from 10 nm to 30 nm with a defined shape (globular), confirmed by UV-vis, SEM, STEM and DLS analysis. This simple and favorable one-step modified Tollens reaction does not require any special equipment or other stabilizing or reducing agent except for a solution of purified mesquite gum, and it produces aqueous colloidal dispersions of silver nanoparticles with a stability thatexceeds three months, a relatively narrow size distribution, a low tendency to aggregate and a yield of at least 95% for all cases. Reaction times are between 15 min and 60 min to obtain silver nanoparticles in concentrations ranging from 0.1 g to 3 g of Ag per 100 g of reaction mixture. The proposed synthetic method presents a high potential for scale-up, since its production capacity is rather high and the methodology is simple.The synthesis that is described in this study is for the preparation of silver nanoparticles of sizes ranging from 10 nm to 30 nm with a defined shape (globular), confirmed by UV-vis, SEM, STEM and DLS analysis. This simple and favorable one-step modified Tollens reaction does not require any special equipment or other stabilizing or reducing agent except for a solution of purified mesquite gum, and it produces aqueous colloidal dispersions of silver nanoparticles with a stability thatexceeds three months, a relatively narrow size distribution, a low tendency to aggregate and a yield of at least 95% for all cases. Reaction times are between 15 min and 60 min to obtain silver nanoparticles in concentrations ranging from 0.1 g to 3 g of Ag per 100 g of reaction mixture. The proposed synthetic method presents a high potential for scale-up, since its production capacity is rather high and the methodology is simple. Full article
Figures

Figure 1

Open AccessArticle Surface Characterization, Corrosion Resistance and in Vitro Biocompatibility of a New Ti‐Hf‐Mo‐Sn Alloy
Materials 2016, 9(10), 818; doi:10.3390/ma9100818
Received: 6 August 2016 / Accepted: 28 September 2016 / Published: 4 October 2016
Cited by 2 | PDF Full-text (9027 KB) | HTML Full-text | XML Full-text
Abstract
A new superelastic Ti‐23Hf‐3Mo‐4Sn biomedical alloy displaying a particularly large recovery strain was synthesized and characterized in this study. Its native passive film is very thick (18 nm) and contains very protective TiO2, Ti2O3, HfO2, MoO2, and SnO2 oxides (XPS analysis). This alloy
[...] Read more.
A new superelastic Ti‐23Hf‐3Mo‐4Sn biomedical alloy displaying a particularly large recovery strain was synthesized and characterized in this study. Its native passive film is very thick (18 nm) and contains very protective TiO2, Ti2O3, HfO2, MoO2, and SnO2 oxides (XPS analysis). This alloy revealed nobler electrochemical behavior, more favorable values of the corrosion parameters and open circuit potentials in simulated body fluid in comparison with commercially pure titanium (CP‐Ti) and Ti‐6Al‐4V alloy taken as reference biomaterials in this study. This is due to the favorable influence of the alloying elements Hf, Sn, Mo, which enhance the protective properties of the native passive film on alloy surface. Impedance spectra showed a passive film with two layers, an inner, capacitive, barrier, dense layer and an outer, less insulating, porous layer that confer both high corrosion resistance and bioactivity to the alloy. In vitro tests were carried out in order to evaluate the response of Human Umbilical Vein Endothelial Cells (HUVECs) to Ti‐23Hf‐3Mo‐4Sn alloy in terms of cell viability, cell proliferation, phenotypic marker expression and nitric oxide release. The results indicate a similar level of cytocompatibility with HUVEC cells cultured on Ti‐23Hf‐3Mo‐4Sn substrate and those cultured on the conventional CP‐Ti and Ti‐6Al‐4V metallic materials. Full article
(This article belongs to the Section Biomaterials)
Figures

Open AccessArticle Using Noise and Fluctuations for In Situ Measurements of Nitrogen Diffusion Depth
Materials 2016, 9(10), 819; doi:10.3390/ma9100819
Received: 30 May 2016 / Accepted: 15 September 2016 / Published: 5 October 2016
Cited by 1 | PDF Full-text (6860 KB) | HTML Full-text | XML Full-text
Abstract
In manufacturing processes involving diffusion (of C, N, S, etc.), the evolution of the layer depth is of the utmost importance: the success of the entire process depends on this parameter. Currently, nitriding is typically either calibrated using a “post process” method or
[...] Read more.
In manufacturing processes involving diffusion (of C, N, S, etc.), the evolution of the layer depth is of the utmost importance: the success of the entire process depends on this parameter. Currently, nitriding is typically either calibrated using a “post process” method or controlled via indirect measurements (H2, O2, H2O + CO2). In the absence of “in situ” monitoring, any variation in the process parameters (gas concentration, temperature, steel composition, distance between sensors and furnace chamber) can cause expensive process inefficiency or failure. Indirect measurements can prevent process failure, but uncertainties and complications may arise in the relationship between the measured parameters and the actual diffusion process. In this paper, a method based on noise and fluctuation measurements is proposed that offers direct control of the layer depth evolution because the parameters of interest are measured in direct contact with the nitrided steel (represented by the active electrode). The paper addresses two related sets of experiments. The first set of experiments consisted of laboratory tests on nitrided samples using Barkhausen noise and yieded a linear relationship between the frequency exponent in the Hooge equation and the nitriding time. For the second set, a specific sensor based on conductivity noise (at the nitriding temperature) was built for shop‐floor experiments. Although two different types of noise were measured in these two sets of experiments, the use of the frequency exponent to monitor the process evolution remained valid. Full article
Figures

Figure 1

Open AccessArticle Effects of Combined Surface and In‐Depth Absorption on Ignition of PMMA
Materials 2016, 9(10), 820; doi:10.3390/ma9100820
Received: 29 August 2016 / Accepted: 26 September 2016 / Published: 5 October 2016
Cited by 1 | PDF Full-text (5053 KB) | HTML Full-text | XML Full-text
Abstract
A one‐dimensional numerical model and theoretical analysis involving both surface and in‐depth radiative heat flux absorption are utilized to investigate the influence of their combination on ignition of PMMA (Polymethyl Methacrylate). Ignition time, transient temperature in a solid and optimized combination of these
[...] Read more.
A one‐dimensional numerical model and theoretical analysis involving both surface and in‐depth radiative heat flux absorption are utilized to investigate the influence of their combination on ignition of PMMA (Polymethyl Methacrylate). Ignition time, transient temperature in a solid and optimized combination of these two absorption modes of black and clear PMMA are examined to understand the ignition mechanism. Based on the comparison, it is found that the selection of constant or variable thermal parameters of PMMA barely affects the ignition time of simulation results. The linearity between tig-0.5 and heat flux does not exist anymore for high heat flux. Both analytical and numerical models underestimate the surface temperature and overestimate the temperature in a solid beneath the heat penetration layer for pure in‐depth absorption. Unlike surface absorption circumstances, the peak value of temperature is in the vicinity of the surface but not on the surface for in‐depth absorption. The numerical model predicts the ignition time better than the analytical model due to the more reasonable ignition criterion selected. The surface temperature increases with increasing incident heat flux. Furthermore, it also increases with the fraction of surface absorption and the radiative extinction coefficient for fixed heat flux. Finally, the combination is optimized by ignition time, temperature distribution in a solid and mass loss rate. Full article
Figures

Figure 1

Open AccessArticle Preparation and Characterization of Modified Soda Lignin with Polyethylene Glycol
Materials 2016, 9(10), 822; doi:10.3390/ma9100822
Received: 4 August 2016 / Revised: 5 September 2016 / Accepted: 28 September 2016 / Published: 7 October 2016
PDF Full-text (2158 KB) | HTML Full-text | XML Full-text
Abstract
Soda lignin does not have thermal flowing characteristics and it is impossible for it to be further thermally molded. To achieve the fusibility of soda lignin for fiber preparation by melt-spinning, an effective method for soda lignin modification was conducted by cooking it
[...] Read more.
Soda lignin does not have thermal flowing characteristics and it is impossible for it to be further thermally molded. To achieve the fusibility of soda lignin for fiber preparation by melt-spinning, an effective method for soda lignin modification was conducted by cooking it with polyethylene glycol (PEG) 400 at various ratios. The higher the ratio of PEG that was used, the more PEG molecular chains were grafted at the alpha carbon of the soda lignin through ether bonds, resulting in lower thermal transition temperatures and more excellent fusibility. The modified soda lignin with a weight ratio of lignin to PEG of 1:4 exhibited a relative thermal stability of molten viscosity at selected temperatures. Thereafter, the resultant fusible soda lignin was successfully melt-spun into filaments with an average diameter of 33 ± 5 μm, which is smaller than that of some industrial lignins. Accordingly, it is possible to utilize soda lignin to produce fibrous carbonaceous materials. Full article
Figures

Figure 1

Open AccessArticle Wire Arc Additive Manufacturing of AZ31 Magnesium Alloy: Grain Refinement by Adjusting Pulse Frequency
Materials 2016, 9(10), 823; doi:10.3390/ma9100823
Received: 26 August 2016 / Revised: 22 September 2016 / Accepted: 5 October 2016 / Published: 9 October 2016
Cited by 9 | PDF Full-text (9763 KB) | HTML Full-text | XML Full-text
Abstract
Wire arc additive manufacturing (WAAM) offers a potential approach to fabricate large-scale magnesium alloy components with low cost and high efficiency, although this topic is yet to be reported in literature. In this study, WAAM is preliminarily applied to fabricate AZ31 magnesium. Fully
[...] Read more.
Wire arc additive manufacturing (WAAM) offers a potential approach to fabricate large-scale magnesium alloy components with low cost and high efficiency, although this topic is yet to be reported in literature. In this study, WAAM is preliminarily applied to fabricate AZ31 magnesium. Fully dense AZ31 magnesium alloy components are successfully obtained. Meanwhile, to refine grains and obtain good mechanical properties, the effects of pulse frequency (1, 2, 5, 10, 100, and 500 Hz) on the macrostructure, microstructure and tensile properties are investigated. The results indicate that pulse frequency can result in the change of weld pool oscillations and cooling rate. This further leads to the change of the grain size, grain shape, as well as the tensile properties. Meanwhile, due to the resonance of the weld pool at 5 Hz and 10 Hz, the samples have poor geometry accuracy but contain finer equiaxed grains (21 μm) and exhibit higher ultimate tensile strength (260 MPa) and yield strength (102 MPa), which are similar to those of the forged AZ31 alloy. Moreover, the elongation of all samples is above 23%. Full article
(This article belongs to the Special Issue Metals for Additive Manufacturing)
Figures

Figure 1

Open AccessArticle Application of a Loop-Type Laboratory Biofilm Reactor to the Evaluation of Biofilm for Some Metallic Materials and Polymers such as Urinary Stents and Catheters
Materials 2016, 9(10), 824; doi:10.3390/ma9100824
Received: 8 May 2016 / Revised: 13 September 2016 / Accepted: 1 October 2016 / Published: 11 October 2016
PDF Full-text (3245 KB) | HTML Full-text | XML Full-text
Abstract
A laboratory biofilm reactor (LBR) was modified to a new loop-type closed system in order to evaluate novel stents and catheter materials using 3D optical microscopy and Raman spectroscopy. Two metallic specimens, pure nickel and cupronickel (80% Cu-20% Ni), along with two polymers,
[...] Read more.
A laboratory biofilm reactor (LBR) was modified to a new loop-type closed system in order to evaluate novel stents and catheter materials using 3D optical microscopy and Raman spectroscopy. Two metallic specimens, pure nickel and cupronickel (80% Cu-20% Ni), along with two polymers, silicone and polyurethane, were chosen as examples to ratify the system. Each set of specimens was assigned to the LBR using either tap water or an NB (Nutrient broth based on peptone from animal foods and beef extract mainly)—cultured solution with E-coli formed over 48–72 h. The specimens were then analyzed using Raman Spectroscopy. 3D optical microscopy was employed to corroborate the Raman Spectroscopy results for only the metallic specimens since the inherent roughness of the polymer specimens made such measurements difficult. The findings suggest that the closed loop-type LBR together with Raman spectroscopy analysis is a useful method for evaluating biomaterials as a potential urinary system. Full article
(This article belongs to the Special Issue Biofilm and Materials Science)
Figures

Figure 1

Open AccessArticle Dielectric Characteristics and Microwave Absorption of Graphene Composite Materials
Materials 2016, 9(10), 825; doi:10.3390/ma9100825
Received: 12 September 2016 / Revised: 27 September 2016 / Accepted: 2 October 2016 / Published: 13 October 2016
Cited by 4 | PDF Full-text (4328 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, many types of materials are elaborated for microwave absorption applications. Carbon-based nanoparticles belong to these types of materials. Among these, graphene presents some distinctive features for electromagnetic radiation absorption and thus microwave isolation applications. In this paper, the dielectric characteristics and microwave
[...] Read more.
Nowadays, many types of materials are elaborated for microwave absorption applications. Carbon-based nanoparticles belong to these types of materials. Among these, graphene presents some distinctive features for electromagnetic radiation absorption and thus microwave isolation applications. In this paper, the dielectric characteristics and microwave absorption properties of epoxy resin loaded with graphene particles are presented from 2 GHz to 18 GHz. The influence of various parameters such as particle size (3 µm, 6–8 µm, and 15 µm) and weight ratio (from 5% to 25%) are presented, studied, and discussed. The sample loaded with the smallest graphene size (3 µm) and the highest weight ratio (25%) exhibits high loss tangent (tanδ = 0.36) and a middle dielectric constant ε′ = 12–14 in the 8–10 GHz frequency range. As expected, this sample also provides the highest absorption level: from 5 dB/cm at 4 GHz to 16 dB/cm at 18 GHz. Full article
(This article belongs to the Special Issue Microwave Absorbing and Energy Storage Materials)
Figures

Figure 1

Open AccessArticle Functionalization of Fe3O4 NPs by Silanization: Use of Amine (APTES) and Thiol (MPTMS) Silanes and Their Physical Characterization
Materials 2016, 9(10), 826; doi:10.3390/ma9100826
Received: 29 July 2016 / Revised: 29 September 2016 / Accepted: 2 October 2016 / Published: 12 October 2016
Cited by 6 | PDF Full-text (5837 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this paper the results concerning the synthesis of magnetite (Fe3O4) nanoparticles (NPs), their functionalization using silane derivatives, such as (3-Aminopropyl)triethoxysilane (APTES) and (3-mercaptopropyl)trimethoxysilane (MPTMS), and their exhaustive morphological and physical characterization by field emission scanning electron microscopy (FE-SEM)
[...] Read more.
In this paper the results concerning the synthesis of magnetite (Fe3O4) nanoparticles (NPs), their functionalization using silane derivatives, such as (3-Aminopropyl)triethoxysilane (APTES) and (3-mercaptopropyl)trimethoxysilane (MPTMS), and their exhaustive morphological and physical characterization by field emission scanning electron microscopy (FE-SEM) with energy dispersion X-ray spectrometer (EDX) analysis, AC magnetic susceptibility, UV-VIS and IR spectroscopy, and thermogravimetric (TGA) analyses are reported. Two different paths were adopted to achieve the desired functionalization: (1) the direct reaction between the functionalized organo-silane molecule and the surface of the magnetite nanoparticle; and (2) the use of an intermediate silica coating. Finally, the occurrence of both the functionalization with amino and thiol groups has been demonstrated by the reaction with ninhydrin and the capture of Au NPs, respectively. Full article
Figures

Open AccessFeature PaperArticle Behavior of Human Bone Marrow-Derived Mesenchymal Stem Cells on Various Titanium-Based Coatings
Materials 2016, 9(10), 827; doi:10.3390/ma9100827
Received: 8 August 2016 / Revised: 26 September 2016 / Accepted: 6 October 2016 / Published: 12 October 2016
PDF Full-text (12291 KB) | HTML Full-text | XML Full-text
Abstract
The chemical composition and texture of titanium coatings can influence the growth characteristics of the adhered cells. An enhanced proliferation of the human mesenchymal stem cells (hMSCs) would be beneficial. The present study was aimed to investigate whether titanium deposited at different atmospheres
[...] Read more.
The chemical composition and texture of titanium coatings can influence the growth characteristics of the adhered cells. An enhanced proliferation of the human mesenchymal stem cells (hMSCs) would be beneficial. The present study was aimed to investigate whether titanium deposited at different atmospheres would affect the cell growth properties, cellular morphology, and expression of surface markers of hMSCs. Titanium-based coatings were deposited on silicon wafers under oxygen, nitrogen, or argon atmospheres by ultra-short pulsed laser deposition using two different gas pressures followed by heating at 400 °C for 2 h. The characteristics of the coated surfaces were determined via contact angle, zeta potential, and scanning electron microscopy (SEM) techniques. Human MSCs were cultivated on differently coated silicon wafers for 48 h. Subsequently, the cell proliferation rates were analyzed with an MTT assay. The phenotype of hMSCs was checked via immunocytochemical stainings of MSC-associated markers CD73, CD90, and CD105, and the adhesion, spreading, and morphology of hMSCs on coated materials via SEM. The cell proliferation rates of the hMSCs were similar on all coated silicon wafers. The hMSCs retained the MSC phenotype by expressing MSC-associated markers and fibroblast-like morphology with cellular projections. Furthermore, no significant differences could be found in the size of the cells when cultured on all various coated surfaces. In conclusion, despite certain differences in the contact angles and the zeta potentials of various titanium-based coatings, no single coating markedly improved the growth characteristics of hMSCs. Full article
Figures

Open AccessFeature PaperArticle Characterization and Effects of Fiber Pull-Outs in Hole Quality of Carbon Fiber Reinforced Plastics Composite
Materials 2016, 9(10), 828; doi:10.3390/ma9100828
Received: 13 July 2016 / Revised: 13 September 2016 / Accepted: 29 September 2016 / Published: 13 October 2016
Cited by 1 | PDF Full-text (5030 KB) | HTML Full-text | XML Full-text
Abstract
Hole quality plays a crucial role in the production of close-tolerance holes utilized in aircraft assembly. Through drilling experiments of carbon fiber-reinforced plastic composites (CFRP), this study investigates the impact of varying drilling feed and speed conditions on fiber pull-out geometries and resulting
[...] Read more.
Hole quality plays a crucial role in the production of close-tolerance holes utilized in aircraft assembly. Through drilling experiments of carbon fiber-reinforced plastic composites (CFRP), this study investigates the impact of varying drilling feed and speed conditions on fiber pull-out geometries and resulting hole quality parameters. For this study, hole quality parameters include hole size variance, hole roundness, and surface roughness. Fiber pull-out geometries are quantified by using scanning electron microscope (SEM) images of the mechanically-sectioned CFRP-machined holes, to measure pull-out length and depth. Fiber pull-out geometries and the hole quality parameter results are dependent on the drilling feed and spindle speed condition, which determines the forces and undeformed chip thickness during the process. Fiber pull-out geometries influence surface roughness parameters from a surface profilometer, while their effect on other hole quality parameters obtained from a coordinate measuring machine is minimal. Full article
(This article belongs to the Special Issue Machining of Composites and Multi-Stacks of Aerospace Materials)
Figures

Figure 1

Open AccessArticle Improvement in Predicting the Post-Cracking Tensile Behavior of Ultra-High Performance Cementitious Composites Based on Fiber Orientation Distribution
Materials 2016, 9(10), 829; doi:10.3390/ma9100829
Received: 1 August 2016 / Revised: 4 October 2016 / Accepted: 9 October 2016 / Published: 13 October 2016
Cited by 3 | PDF Full-text (2881 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the post-cracking tensile behavior of Ultra-High Performance Cementitious Composites (UHPCC) was studied and an improved analytical model to predict the behavior depending on the fiber orientation distribution was proposed. Two different casting methods were adopted to estimate the influence of
[...] Read more.
In this paper, the post-cracking tensile behavior of Ultra-High Performance Cementitious Composites (UHPCC) was studied and an improved analytical model to predict the behavior depending on the fiber orientation distribution was proposed. Two different casting methods were adopted to estimate the influence of the casting method on the tensile behavior. The direct tensile test results showed that the post-cracking tensile behavior was considerably dependent on the casting method. The influence of the casting method was quantified by image analysis of the fiber distribution. The fiber orientation distribution obtained by image analysis may sometimes include considerable error according to the image resolution, which may cause inaccuracy when predicting the post-cracking tensile behavior based on the fiber orientation distribution. To overcome this dependency, the tensile bridging behavior by the fibers in UHPCC was simulated considering the obtained fiber orientation distribution as well as the number of fibers detected. The post-cracking behavior was then simulated by combining the bridging behavior and tension softening behavior of the matrix. The approach adopted in this study to simulate the post-cracking behavior of UHPCC showed good agreement with the experimental results. Full article
(This article belongs to the Section Advanced Composites)
Figures

Figure 1

Open AccessArticle A New Compact Double-Negative Miniaturized Metamaterial for Wideband Operation
Materials 2016, 9(10), 830; doi:10.3390/ma9100830
Received: 1 September 2016 / Revised: 24 September 2016 / Accepted: 28 September 2016 / Published: 13 October 2016
Cited by 11 | PDF Full-text (3995 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The aim of this paper is to introduce a compact double-negative (DNG) metamaterial that exhibits a negative refractive index (NRI) bandwidth of more than 3.6 GHz considering the frequency from 2 to 14 GHz. In this framework, two arms of the designed unit
[...] Read more.
The aim of this paper is to introduce a compact double-negative (DNG) metamaterial that exhibits a negative refractive index (NRI) bandwidth of more than 3.6 GHz considering the frequency from 2 to 14 GHz. In this framework, two arms of the designed unit cell are split in a way that forms a Modified-Z-shape structure of the FR-4 substrate material. The finite integration technique (FIT)-based Computer Simulation Technology (CST) Microwave Studio is applied for computation, and the experimental setup for measuring the performance is performed inside two waveguide ports. Therefore, the measured data complies well with the simulated data of the unit cell at 0-degree and 90-degree rotation angles. The designed unit cell shows a negative refractive index from 3.482 to 7.096 GHz (bandwidth of 3.61 GHz), 7.876 to 10.047 GHz (bandwidth of 2.171 GHz), and 11.594 to 14 GHz (bandwidth of 2.406 GHz) in the microwave spectra. The design also exhibits almost the same wide negative refractive index bandwidth in the major region of the C-band and X-band if it is rotated 90 degrees. However, the novelty of the proposed structure lies in its effective medium ratio of more than 4, wide bandwidth, and compact size. Full article
Figures

Figure 1

Open AccessArticle A Constitutive Relationship between Fatigue Limit and Microstructure in Nanostructured Bainitic Steels
Materials 2016, 9(10), 831; doi:10.3390/ma9100831
Received: 31 August 2016 / Revised: 21 September 2016 / Accepted: 27 September 2016 / Published: 14 October 2016
Cited by 4 | PDF Full-text (12929 KB) | HTML Full-text | XML Full-text
Abstract
The recently developed nanobainitic steels show high strength as well as high ductility. Although this combination seems to be promising for fatigue design, fatigue properties of nanostructured bainitic steels are often surprisingly low. To improve the fatigue behavior, an understanding of the correlation
[...] Read more.
The recently developed nanobainitic steels show high strength as well as high ductility. Although this combination seems to be promising for fatigue design, fatigue properties of nanostructured bainitic steels are often surprisingly low. To improve the fatigue behavior, an understanding of the correlation between the nanobainitic microstructure and the fatigue limit is fundamental. Therefore, our hypothesis to predict the fatigue limit was that the main function of the microstructure is not necessarily totally avoiding the initiation of a fatigue crack, but the microstructure has to increase the ability to decelerate or to stop a growing fatigue crack. Thus, the key to understanding the fatigue behavior of nanostructured bainite is to understand the role of the microstructural features that could act as barriers for growing fatigue cracks. To prove this hypothesis, we carried out fatigue tests, crack growth experiments, and correlated these results to the size of microstructural features gained from microstructural analysis by light optical microscope and EBSD-measurements. Finally, we were able to identify microstructural features that influence the fatigue crack growth and the fatigue limit of nanostructured bainitic steels. Full article
(This article belongs to the Special Issue Fracture and Fatigue Mechanics of Materials)
Figures

Figure 1

Open AccessArticle Peanut Shell-Derived Carbon Solid Acid with Large Surface Area and Its Application for the Catalytic Hydrolysis of Cyclohexyl Acetate
Materials 2016, 9(10), 833; doi:10.3390/ma9100833
Received: 5 September 2016 / Revised: 29 September 2016 / Accepted: 11 October 2016 / Published: 15 October 2016
PDF Full-text (2613 KB) | HTML Full-text | XML Full-text
Abstract
A carbon solid acid with large surface area (CSALA) was prepared by partial carbonization of H3PO4 pre-treated peanut shells followed by sulfonation with concentrated H2SO4. The structure and acidity of CSALA were characterized by N2
[...] Read more.
A carbon solid acid with large surface area (CSALA) was prepared by partial carbonization of H3PO4 pre-treated peanut shells followed by sulfonation with concentrated H2SO4. The structure and acidity of CSALA were characterized by N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), 13C cross polarization (CP)/magic angle spinning (MAS) nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy (FT-IR), titration, and elemental analysis. The results demonstrated that the CSALA was an amorphous carbon material with a surface area of 387.4 m2/g. SO3H groups formed on the surface with a density of 0.46 mmol/g, with 1.11 mmol/g of COOH and 0.39 mmol/g of phenolic OH. Densities of the latter two groups were notably greater than those observed on a carbon solid acid (CSA) with a surface area of 10.1 m2/g. The CSALA catalyst showed better performance than the CSA for the hydrolysis of cyclohexyl acetate to cyclohexanol. Under optimal reaction conditions, cyclohexyl acetate conversion was 86.6% with 97.3% selectivity for cyclohexanol, while the results were 25.0% and 99.4%, respectively, catalyzed by CSA. The high activity of the CSALA could be attributed to its high density of COOH and large surface area. Moreover, the CSALA showed good reusability. Its catalytic activity decreased slightly during the first two cycles due to the leaching of polycyclic aromatic hydrocarbon-containing SO3H groups, and then remained constant during following uses. Full article
Figures

Figure 1

Open AccessArticle Microstructural Evolution, Thermodynamics, and Kinetics of Mo-Tm2O3 Powder Mixtures during Ball Milling
Materials 2016, 9(10), 834; doi:10.3390/ma9100834
Received: 23 August 2016 / Revised: 4 October 2016 / Accepted: 11 October 2016 / Published: 15 October 2016
Cited by 2 | PDF Full-text (5732 KB) | HTML Full-text | XML Full-text
Abstract
The microstructural evolution, thermodynamics, and kinetics of Mo (21 wt %) Tm2O3 powder mixtures during ball milling were investigated using X-ray diffraction and transmission electron microscopy. Ball milling induced Tm2O3 to be decomposed and then dissolved into
[...] Read more.
The microstructural evolution, thermodynamics, and kinetics of Mo (21 wt %) Tm2O3 powder mixtures during ball milling were investigated using X-ray diffraction and transmission electron microscopy. Ball milling induced Tm2O3 to be decomposed and then dissolved into Mo crystal. After 96 h of ball milling, Tm2O3 was dissolved completely and the supersaturated nanocrystalline solid solution of Mo (Tm, O) was obtained. The Mo lattice parameter increased with increasing ball-milling time, opposite for the Mo grain size. The size and lattice parameter of Mo grains was about 8 nm and 0.31564 nm after 96 h of ball milling, respectively. Ball milling induced the elements of Mo, Tm, and O to be distributed uniformly in the ball-milled particles. Based on the semi-experimental theory of Miedema, a thermodynamic model was developed to calculate the driving force of phase evolution. There was no chemical driving force to form a crystal solid solution of Tm atoms in Mo crystal or an amorphous phase because the Gibbs free energy for both processes was higher than zero. For Mo (21 wt %) Tm2O3, it was mechanical work, not the negative heat of mixing, which provided the driving force to form a supersaturated nanocrystalline Mo (Tm, O) solid solution. Full article
Figures

Figure 1

Open AccessArticle Pentaethylenehexamine-Loaded Hierarchically Porous Silica for CO2 Adsorption
Materials 2016, 9(10), 835; doi:10.3390/ma9100835
Received: 15 August 2016 / Revised: 25 September 2016 / Accepted: 8 October 2016 / Published: 15 October 2016
Cited by 1 | PDF Full-text (7923 KB) | HTML Full-text | XML Full-text
Abstract
Recently, amine-functionalized materials as a prospective chemical sorbent for post combustion CO2 capture have gained great interest. However, the amine grafting for the traditional MCM-41, SBA-15, pore-expanded MCM-41 or SBA-15 supports can cause the pore volume and specific surface area of sorbents
[...] Read more.
Recently, amine-functionalized materials as a prospective chemical sorbent for post combustion CO2 capture have gained great interest. However, the amine grafting for the traditional MCM-41, SBA-15, pore-expanded MCM-41 or SBA-15 supports can cause the pore volume and specific surface area of sorbents to decrease, significantly affecting the CO2 adsorption-desorption dynamics. To overcome this issue, hierarchical porous silica with interparticle macropores and long-range ordering mesopores was prepared and impregnated with pentaethylenehexamine. The pore structure and amino functional group content of the modified silicas were analyzed by scanning electron microscope, transmission electron microscope, N2 adsorption, X-ray powder diffraction, and Fourier transform infrared spectra. Moreover, the effects of the pore structure as well as the amount of PEHA loading of the samples on the CO2 adsorption capacity were investigated in a fixed-bed adsorption system. The CO2 adsorption capacity reached 4.5 mmol CO2/(g of adsorbent) for HPS−PEHA-70 at 75 °C. Further, the adsorption capacity for HPS-PEHA-70 was steady after a total of 15 adsorption-desorption cycles. Full article
Figures

Figure 1a

Open AccessArticle Physical Properties of PDMS (Polydimethylsiloxane) Microfluidic Devices on Fluid Behaviors: Various Diameters and Shapes of Periodically-Embedded Microstructures
Materials 2016, 9(10), 836; doi:10.3390/ma9100836
Received: 17 August 2016 / Revised: 29 September 2016 / Accepted: 11 October 2016 / Published: 15 October 2016
Cited by 1 | PDF Full-text (4834 KB) | HTML Full-text | XML Full-text
Abstract
Deformable polydimethylsiloxane (PDMS) microfluidic devices embedded with three differently-shaped obstacles (hexagon, square, and triangle) were used to examine the significant challenge to classical fluid dynamics. The significant factors in determining a quasi-steady state value of flow velocity (v)QS and pressure
[...] Read more.
Deformable polydimethylsiloxane (PDMS) microfluidic devices embedded with three differently-shaped obstacles (hexagon, square, and triangle) were used to examine the significant challenge to classical fluid dynamics. The significant factors in determining a quasi-steady state value of flow velocity (v)QS and pressure drop per unit length (∆P/∆x)QS were dependent on the characteristic of embedded microstructures as well as the applied flow rates. The deviation from the theoretical considerations due to PDMS bulging investigated by the friction constant and the normalized friction factor revealed that the largest PDMS bulging observed in hexagonal obstacles had the smallest (∆P/∆x)QS ratios, whereas triangle obstacles exhibited the smallest PDMS bulging, but recorded the largest (∆P/∆x)QS ratios. However, the influence of (v)QS ratio on microstructures was not very significant in this study. The results were close to the predicted values even though some discrepancy may be due to the relatively mean bulging and experimental uncertainty. The influence of deformable PDMS microfluidic channels with various shapes of embedded microstructures was compared with the rigid microchannels. The significant deviation from the classical relation (i.e., f~1/Re) was also observed in hexagonal obstacles and strongly dependent on the channel geometry, the degree of PDMS deformation, and the shapes of the embedded microstructures. Full article
(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)
Figures

Figure 1

Open AccessArticle Surface Structures Formed by a Copper(II) Complex of Alkyl-Derivatized Indigo
Materials 2016, 9(10), 837; doi:10.3390/ma9100837
Received: 15 July 2016 / Revised: 29 September 2016 / Accepted: 10 October 2016 / Published: 15 October 2016
Cited by 1 | PDF Full-text (3318 KB) | HTML Full-text | XML Full-text
Abstract
Assembled structures of dyes have great influence on their coloring function. For example, metal ions added in the dyeing process are known to prevent fading of color. Thus, we have investigated the influence of an addition of copper(II) ion on the surface structure
[...] Read more.
Assembled structures of dyes have great influence on their coloring function. For example, metal ions added in the dyeing process are known to prevent fading of color. Thus, we have investigated the influence of an addition of copper(II) ion on the surface structure of alkyl-derivatized indigo. Scanning tunneling microscope (STM) analysis revealed that the copper(II) complexes of indigo formed orderly lamellar structures on a HOPG substrate. These lamellar structures of the complexes are found to be more stable than those of alkyl-derivatized indigos alone. Furthermore, 2D chirality was observed. Full article
(This article belongs to the Special Issue Functional Organic Dyes and Pigments)
Figures

Open AccessArticle Metal-Promoted Assembly of Two Collagen Mimetic Peptides into a Biofunctional “Spiraled Horn” Scaffold
Materials 2016, 9(10), 838; doi:10.3390/ma9100838
Received: 12 August 2016 / Revised: 30 September 2016 / Accepted: 11 October 2016 / Published: 17 October 2016
Cited by 1 | PDF Full-text (10530 KB) | HTML Full-text | XML Full-text
Abstract
Biofunctional scaffolds for the delivery of living cells are of the utmost importance for regenerative medicine. Herein, a novel, robust “spiraled horn” scaffold was elucidated through the Co2+-promoted hierarchical assembly of two collagen mimetic peptides, NCoH and HisCol. Each “horn”
[...] Read more.
Biofunctional scaffolds for the delivery of living cells are of the utmost importance for regenerative medicine. Herein, a novel, robust “spiraled horn” scaffold was elucidated through the Co2+-promoted hierarchical assembly of two collagen mimetic peptides, NCoH and HisCol. Each “horn” displayed a periodic banding pattern with band lengths corresponding to the length of the collagen peptide triple helix. Strand exchange between the two peptide trimers resulted in failure to form this intricate morphology, lending support to a precise metal-ligand-based mechanism of assembly. Little change occurred to the observed morphology when the Co2+ concentration was varied from 0.5 to 4.0 mM, and the scaffold was found to be fully formed within two minutes of exposure to the metal ion. The horned network also displayed biological functionality by binding to a His-tagged fluorophore and associating with cells. Full article
(This article belongs to the Special Issue Biological and Synthetic Organic–Inorganic Composite Materials)
Figures

Open AccessArticle Polymer-Cement Composites Containing Waste Perlite Powder
Materials 2016, 9(10), 839; doi:10.3390/ma9100839
Received: 29 August 2016 / Revised: 7 October 2016 / Accepted: 12 October 2016 / Published: 17 October 2016
Cited by 2 | PDF Full-text (5833 KB) | HTML Full-text | XML Full-text
Abstract
Polymer-cement composites (PCCs) are materials in which the polymer and mineral binder create an interpenetrating network and co-operate, significantly improving the performance of the material. On the other hand, the need for the utilization of waste materials is a demand of sustainable construction.
[...] Read more.
Polymer-cement composites (PCCs) are materials in which the polymer and mineral binder create an interpenetrating network and co-operate, significantly improving the performance of the material. On the other hand, the need for the utilization of waste materials is a demand of sustainable construction. Various mineral powders, such as fly ash or blast-furnace slag, are successfully used for the production of cement and concrete. This paper deals with the use of perlite powder, which is a burdensome waste from the process of thermal expansion of the raw perlite, as a component of PCCs. The results of the testing of the mechanical properties of the composite and some microscopic observations are presented, indicating that there is a possibility to rationally and efficiently utilize waste perlite powder as a component of the PCC. This would lead to creating a new type of building material that successfully meets the requirements of sustainable construction. Full article
Figures

Figure 1

Open AccessArticle Cubic C3N: A New Superhard Phase of Carbon-Rich Nitride
Materials 2016, 9(10), 840; doi:10.3390/ma9100840
Received: 5 September 2016 / Revised: 4 October 2016 / Accepted: 12 October 2016 / Published: 17 October 2016
Cited by 6 | PDF Full-text (1752 KB) | HTML Full-text | XML Full-text
Abstract
Using the particle swarm optimization technique, we proposed a cubic superhard phase of C3N (c-C3N) with an estimated Vicker’s hardness of 65 GPa, which is more energetically favorable than the recently proposed o-C3N. The
[...] Read more.
Using the particle swarm optimization technique, we proposed a cubic superhard phase of C3N (c-C3N) with an estimated Vicker’s hardness of 65 GPa, which is more energetically favorable than the recently proposed o-C3N. The c-C3N is the most stable phase in a pressure range of 6.5–15.4 GPa. Above 15.4 GPa, the most energetic favorable high pressure phase R3m-C3N is uncovered. Phonon dispersion and elastic constant calculations confirm the dynamical and mechanical stability of c-C3N and R3m-C3N at ambient pressure. The electronic structure calculations indicate that both c-C3N and R3m-C3N are indirect semiconductor. Full article
(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)
Figures

Open AccessArticle Incorporation of Rubber Powder as Filler in a New Dry-Hybrid Technology: Rheological and 3D DEM Mastic Performances Evaluation
Materials 2016, 9(10), 842; doi:10.3390/ma9100842
Received: 25 July 2016 / Revised: 10 October 2016 / Accepted: 12 October 2016 / Published: 18 October 2016
Cited by 3 | PDF Full-text (2892 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, the use of crumb rubber as modifier or additive within asphalt concretes has allowed obtaining mixtures able to bind high performances to recovery and reuse of discarded tires. To date, the common technologies that permit the reuse of rubber powder
[...] Read more.
In recent years, the use of crumb rubber as modifier or additive within asphalt concretes has allowed obtaining mixtures able to bind high performances to recovery and reuse of discarded tires. To date, the common technologies that permit the reuse of rubber powder are the wet and dry ones. In this paper, a dry-hybrid technology for the production of Stone Mastic Asphalt mixtures is proposed. It allows the use of the rubber powder as filler, replacing part of the limestone one. Fillers are added and mixed with a high workability bitumen, modified with SBS (styrene-butadiene-styrene) polymer and paraffinic wax. The role of rubber powder and limestone filler within the bituminous mastic has been investigated through two different approaches. The first one is a rheological approach, which comprises a macro-scale laboratory analysis and a micro-scale DEM simulation. The second, instead, is a performance approach at high temperatures, which includes Multiple Stress Creep Recovery tests. The obtained results show that the rubber works as filler and it improves rheological characteristics of the polymer modified bitumen. In particular, it increases stiffness and elasticity at high temperatures and it reduces complex modulus at low temperatures. Full article
Figures

Open AccessArticle Interior Fracture Mechanism Analysis and Fatigue Life Prediction of Surface-Hardened Gear Steel under Axial Loading
Materials 2016, 9(10), 843; doi:10.3390/ma9100843
Received: 31 August 2016 / Revised: 29 September 2016 / Accepted: 13 October 2016 / Published: 18 October 2016
PDF Full-text (3587 KB) | HTML Full-text | XML Full-text
Abstract
The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized
[...] Read more.
The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized low alloy gear steel in the long life region. Results show that this steel represents the duplex S-N (stress-number of cycles) characteristics without conventional fatigue limit related to 107 cycles. Fatigue cracks are all originated from the interior inclusions in the matrix region due to the inhabitation effect of carburized layer. The inclusion induced fracture with fisheye occurs in the short life region below 5 × 105 cycles, whereas the inclusion induced fracture with fine granular area (FGA) and fisheye occurs in the long life region beyond 106 cycles. The stress intensity factor range at the front of FGA can be regarded as the threshold value controlling stable growth of interior long crack. The evaluated maximum inclusion size in the effective damage volume of specimen is about 27.29 μm. Considering the size relationships between fisheye and FGA, and inclusion, the developed life prediction method involving crack growth can be acceptable on the basis of the good agreement between the predicted and experimental results. Full article
(This article belongs to the Special Issue Fracture and Fatigue Mechanics of Materials)
Figures

Figure 1

Open AccessArticle Comparisons of Damage Evolution between 2D C/SiC and SiC/SiC Ceramic-Matrix Composites under Tension-Tension Cyclic Fatigue Loading at Room and Elevated Temperatures
Materials 2016, 9(10), 844; doi:10.3390/ma9100844
Received: 3 August 2016 / Revised: 28 September 2016 / Accepted: 11 October 2016 / Published: 19 October 2016
Cited by 2 | PDF Full-text (10879 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, comparisons of damage evolution between 2D C/SiC and SiC/SiC ceramic-matrix composites (CMCs) under tension–tension cyclic fatigue loading at room and elevated temperatures have been investigated. Fatigue hysteresis loops models considering multiple matrix cracking modes in 2D CMCs have been developed
[...] Read more.
In this paper, comparisons of damage evolution between 2D C/SiC and SiC/SiC ceramic-matrix composites (CMCs) under tension–tension cyclic fatigue loading at room and elevated temperatures have been investigated. Fatigue hysteresis loops models considering multiple matrix cracking modes in 2D CMCs have been developed based on the damage mechanism of fiber sliding relative to the matrix in the interface debonded region. The relationships between the fatigue hysteresis loops, fatigue hysteresis dissipated energy, fatigue peak stress, matrix multiple cracking modes, and interface shear stress have been established. The effects of fiber volume fraction, fatigue peak stress and matrix cracking mode proportion on fatigue hysteresis dissipated energy and interface debonding and sliding have been analyzed. The experimental fatigue hysteresis dissipated energy of 2D C/SiC and SiC/SiC composites at room temperature, 550 °C, 800 °C, and 1100 °C in air, and 1200 °C in vacuum corresponding to different fatigue peak stresses and cycle numbers have been analyzed. The interface shear stress degradation rate has been obtained through comparing the experimental fatigue hysteresis dissipated energy with theoretical values. Fatigue damage evolution in C/SiC and SiC/SiC composites has been compared using damage parameters of fatigue hysteresis dissipated energy and interface shear stress degradation rate. It was found that the interface shear stress degradation rate increases at elevated temperature in air compared with that at room temperature, decreases with increasing loading frequency at room temperature, and increases with increasing fatigue peak stress at room and elevated temperatures. Full article
(This article belongs to the Section Advanced Composites)
Figures

Figure 1a

Open AccessArticle Modification of Lightweight Aggregates’ Microstructure by Used Motor Oil Addition
Materials 2016, 9(10), 845; doi:10.3390/ma9100845
Received: 4 August 2016 / Revised: 21 September 2016 / Accepted: 6 October 2016 / Published: 18 October 2016
Cited by 2 | PDF Full-text (6713 KB) | HTML Full-text | XML Full-text
Abstract
An admixture of lightweight aggregate substrates (beidellitic clay containing 10 wt % of natural clinoptilolite or Na-P1 zeolite) with used motor oil (1 wt %–8 wt %) caused marked changes in the aggregates’ microstructure, measured by a combination of mercury porosimetry (MIP), microtomography
[...] Read more.
An admixture of lightweight aggregate substrates (beidellitic clay containing 10 wt % of natural clinoptilolite or Na-P1 zeolite) with used motor oil (1 wt %–8 wt %) caused marked changes in the aggregates’ microstructure, measured by a combination of mercury porosimetry (MIP), microtomography (MT), and scanning electron microscopy. Maximum porosity was produced at low (1%–2%) oil concentrations and it dropped at higher concentrations, opposite to the aggregates’ bulk density. Average pore radii, measured by MIP, decreased with an increasing oil concentration, whereas larger (MT) pore sizes tended to increase. Fractal dimension, derived from MIP data, changed similarly to the MIP pore radius, while that derived from MT remained unaltered. Solid phase density, measured by helium pycnometry, initially dropped slightly and then increased with the amount of oil added, which was most probably connected to changes in the formation of extremely small closed pores that were not available for He atoms. Full article
(This article belongs to the Special Issue Porous Ceramics)
Figures

Open AccessArticle Effect of Surface Densification on the Microstructure and Mechanical Properties of Powder Metallurgical Gears by Using a Surface Rolling Process
Materials 2016, 9(10), 846; doi:10.3390/ma9100846
Received: 22 August 2016 / Revised: 25 September 2016 / Accepted: 14 October 2016 / Published: 19 October 2016
Cited by 1 | PDF Full-text (4031 KB) | HTML Full-text | XML Full-text
Abstract
Powder metallurgy (PM) components are widely used in the auto industry due to the advantage of net-shape forming, low cost, and high efficiency. Still, usage of PM components is limited in the auto industry when encountering rigorous situations, like heavy load, due to
[...] Read more.
Powder metallurgy (PM) components are widely used in the auto industry due to the advantage of net-shape forming, low cost, and high efficiency. Still, usage of PM components is limited in the auto industry when encountering rigorous situations, like heavy load, due to lower strength, hardness, wear resistance, and other properties compared to wrought components due to the existence of massive pores in the PM components. In this study, through combining the powder metallurgy process and rolling process, the pores in the PM components were decreased and a homogenous densified layer was formed on the surface, which resulted in the enhancement of the strength, hardness, wear resistance, and other properties, which can expand its range of application. In this paper, we study the impact of different rolling feeds on the performance of the components’ surfaces. We found that with the increase of the rolling feed, the depth of the densified layer increased. Full article
(This article belongs to the Special Issue Tribological Behavior of Materials by Surface Engineering)
Figures

Figure 1

Open AccessArticle Optimization of High Temperature and Pressurized Steam Modified Wood Fibers for High-Density Polyethylene Matrix Composites Using the Orthogonal Design Method
Materials 2016, 9(10), 847; doi:10.3390/ma9100847
Received: 7 August 2016 / Revised: 25 September 2016 / Accepted: 10 October 2016 / Published: 18 October 2016
Cited by 3 | PDF Full-text (2828 KB) | HTML Full-text | XML Full-text
Abstract
The orthogonal design method was used to determine the optimum conditions for modifying poplar fibers through a high temperature and pressurized steam treatment for the subsequent preparation of wood fiber/high-density polyethylene (HDPE) composites. The extreme difference, variance, and significance analyses were performed to
[...] Read more.
The orthogonal design method was used to determine the optimum conditions for modifying poplar fibers through a high temperature and pressurized steam treatment for the subsequent preparation of wood fiber/high-density polyethylene (HDPE) composites. The extreme difference, variance, and significance analyses were performed to reveal the effect of the modification parameters on the mechanical properties of the prepared composites, and they yielded consistent results. The main findings indicated that the modification temperature most strongly affected the mechanical properties of the prepared composites, followed by the steam pressure. A temperature of 170 °C, a steam pressure of 0.8 MPa, and a processing time of 20 min were determined as the optimum parameters for fiber modification. Compared to the composites prepared from untreated fibers, the tensile, flexural, and impact strength of the composites prepared from modified fibers increased by 20.17%, 18.5%, and 19.3%, respectively. The effect on the properties of the composites was also investigated by scanning electron microscopy and dynamic mechanical analysis. When the temperature, steam pressure, and processing time reached the highest values, the composites exhibited the best mechanical properties, which were also well in agreement with the results of the extreme difference, variance, and significance analyses. Moreover, the crystallinity and thermal stability of the fibers and the storage modulus of the prepared composites improved; however, the hollocellulose content and the pH of the wood fibers decreased. Full article
Figures

Open AccessArticle A Novel Nanohybrid Nanofibrous Adsorbent for Water Purification from Dye Pollutants
Materials 2016, 9(10), 848; doi:10.3390/ma9100848
Received: 9 September 2016 / Revised: 6 October 2016 / Accepted: 10 October 2016 / Published: 19 October 2016
Cited by 6 | PDF Full-text (3001 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we devised a novel nanofibrous adsorbent made of polyethersulfone (PES) for removal of methylene blue (MB) dye pollutant from water. The polymer shows a low isoelectric point thus at elevated pHs and, being nanofibrous, can offer a huge highly hydroxylated
[...] Read more.
In this study, we devised a novel nanofibrous adsorbent made of polyethersulfone (PES) for removal of methylene blue (MB) dye pollutant from water. The polymer shows a low isoelectric point thus at elevated pHs and, being nanofibrous, can offer a huge highly hydroxylated surface area for adsorption of cationic MB molecules. As an extra challenge, to augment the adsorbent’s properties in terms of adsorption capacity in neutral and acidic conditions and thermal stability, vanadium pentoxide (V2O5) nanoparticles were added to the nanofibers. Adsorption data were analyzed according to the Freundlich adsorption model. The thermodynamic parameters verified that only at basic pH is the adsorption spontaneous and in general the process is entropy-driven and endothermic. The kinetics of the adsorption process was evaluated by the pseudo-first- and pseudo-second-order models. The latter model exhibited the highest correlation with data. In sum, the adsorbent showed a promising potential for dye removal from industrial dyeing wastewater systems, especially when envisaging their alkaline and hot conditions. Full article
(This article belongs to the Special Issue Green Nanotechnology)
Figures

Open AccessArticle Synthesis and Characterization of N-Doped Porous TiO2 Hollow Spheres and Their Photocatalytic and Optical Properties
Materials 2016, 9(10), 849; doi:10.3390/ma9100849
Received: 28 August 2016 / Revised: 4 October 2016 / Accepted: 11 October 2016 / Published: 19 October 2016
Cited by 3 | PDF Full-text (7297 KB) | HTML Full-text | XML Full-text
Abstract
Three kinds of N-doped mesoporous TiO2 hollow spheres with different N-doping contents, surface area, and pore size distributions were prepared based on a sol–gel synthesis and combined with a calcination process. Melamine formaldehyde (MF) microspheres have been used as sacrificial template and
[...] Read more.
Three kinds of N-doped mesoporous TiO2 hollow spheres with different N-doping contents, surface area, and pore size distributions were prepared based on a sol–gel synthesis and combined with a calcination process. Melamine formaldehyde (MF) microspheres have been used as sacrificial template and cetyltrimethyl ammonium bromide (CTAB) or polyvinylpyrrolidone (PVP) was selected as pore-directing agent. Core–shell intermediate spheres of titania-coated MF with diameters of 1.2–1.6 μm were fabricated by varying the volume concentration of TiO2 precursor from 1 to 3 vol %. By calcining the core–shell composite spheres at 500 °C for 3 h in air, an in situ N-doping process occurred upon the decomposition of the MF template and CTAB or PVP pore-directing surfactant. N-doped mesoporous TiO2 hollow spheres with sizes in the range of 0.4–1.2 μm and shell thickness from 40 to 110 nm were obtained. The composition and N-doping content, thermal stability, morphology, surface area and pore size distribution, wall thickness, photocatalytic activities, and optical properties of the mesoporous TiO2 hollow spheres derived from different conditions were investigated and compared based on Fourier-transformation infrared (FTIR), SEM, TEM, thermogravimetric analysis (TGA), nitrogen adsorption–desorption, and UV–vis spectrophotoscopy techniques. The influences of particle size, N-doping, porous, and hollow characteristics of the TiO2 hollow spheres on their photocatalytic activities and optical properties have been studied and discussed based on the composition analysis, structure characterization, and optical property investigation of these hollow spherical TiO2 matrices. Full article
(This article belongs to the Special Issue Porous Materials for Water Technology)
Figures

Figure 1

Open AccessArticle Flexural Capability of Patterned Transparent Conductive Substrate by Performing Electrical Measurements and Stress Simulations
Materials 2016, 9(10), 850; doi:10.3390/ma9100850
Received: 31 August 2016 / Revised: 4 October 2016 / Accepted: 14 October 2016 / Published: 19 October 2016
PDF Full-text (3034 KB) | HTML Full-text | XML Full-text
Abstract
The suitability of stacked thin films for next-generation display technology was analyzed based on their properties and geometrical designs to evaluate the mechanical reliability of transparent conducting thin films utilized in flexural displays. In general, the high bending stress induced by various operation
[...] Read more.
The suitability of stacked thin films for next-generation display technology was analyzed based on their properties and geometrical designs to evaluate the mechanical reliability of transparent conducting thin films utilized in flexural displays. In general, the high bending stress induced by various operation conditions is a major concern regarding the mechanical reliability of indium–tin–oxide (ITO) films deposited on polyethylene terephthalate (PET) substrates; mechanical reliability is commonly used to estimate the flexibility of displays. However, the pattern effect is rarely investigated to estimate the mechanical reliability of ITO/PET films. Thus, this study examined the flexible content of patterned ITO/PET films with two different line widths by conducting bending tests and sheet resistance measurements. Moreover, a stress–strain simulation enabled by finite element analysis was performed on the patterned ITO/PET to explore the stress impact of stacked film structures under various levels of flexural load. Results show that the design of the ITO/PET film can be applied in developing mechanically reliable flexible electronics. Full article
(This article belongs to the Special Issue Advances in Bendable and Soft Material Film)
Figures

Figure 1

Open AccessArticle Morphological Influence of Solution-Processed Zinc Oxide Films on Electrical Characteristics of Thin-Film Transistors
Materials 2016, 9(10), 851; doi:10.3390/ma9100851
Received: 8 September 2016 / Revised: 12 October 2016 / Accepted: 13 October 2016 / Published: 19 October 2016
Cited by 1 | PDF Full-text (4334 KB) | HTML Full-text | XML Full-text
Abstract
We report on the morphological influence of solution-processed zinc oxide (ZnO) semiconductor films on the electrical characteristics of ZnO thin-film transistors (TFTs). Different film morphologies were produced by controlling the spin-coating condition of a precursor solution, and the ZnO films were analyzed using
[...] Read more.
We report on the morphological influence of solution-processed zinc oxide (ZnO) semiconductor films on the electrical characteristics of ZnO thin-film transistors (TFTs). Different film morphologies were produced by controlling the spin-coating condition of a precursor solution, and the ZnO films were analyzed using atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and Hall measurement. It is shown that ZnO TFTs have a superior performance in terms of the threshold voltage and field-effect mobility, when ZnO crystallites are more densely packed in the film. This is attributed to lower electrical resistivity and higher Hall mobility in a densely packed ZnO film. In the results of consecutive TFT operations, a positive shift in the threshold voltage occurred irrespective of the film morphology, but the morphological influence on the variation in the field-effect mobility was evident. The field-effect mobility in TFTs having a densely packed ZnO film increased continuously during consecutive TFT operations, which is in contrast to the mobility decrease observed in the less packed case. An analysis of the field-effect conductivities ascribes these results to the difference in energetic traps, which originate from structural defects in the ZnO films. Consequently, the morphological influence of solution-processed ZnO films on the TFT performance can be understood through the packing property of ZnO crystallites. Full article
(This article belongs to the Special Issue Oxide Semiconductor Thin-Film Transistor)
Figures

Figure 1

Open AccessArticle A Fracture Analysis of Ti-10Mo-8V-1Fe-3.5Al Alloy Screws during Assembly
Materials 2016, 9(10), 852; doi:10.3390/ma9100852
Received: 29 August 2016 / Revised: 16 October 2016 / Accepted: 17 October 2016 / Published: 19 October 2016
PDF Full-text (4726 KB) | HTML Full-text | XML Full-text
Abstract
Titanium screws have properties that make them ideal for applications that require both a high strength-to-weight ratio and corrosion resistance, such as fastener applications for aviation and aerospace. The fracture behavior of Ti-10Mo-8V-1Fe-3.5Al (TB3) alloy screws during assembly was explored. Besides visual examination,
[...] Read more.
Titanium screws have properties that make them ideal for applications that require both a high strength-to-weight ratio and corrosion resistance, such as fastener applications for aviation and aerospace. The fracture behavior of Ti-10Mo-8V-1Fe-3.5Al (TB3) alloy screws during assembly was explored. Besides visual examination, other experimental techniques used for the investigation are as follows: (1) fracture characteristics and damage morphology via scanning electron microscopy (SEM); (2) chemical constituents via energy dispersive spectroscopy (EDS) and hydrogen concentration testing; (3) metallographic observation; (4) stress durability embrittlement testing; and (5) torsion simulation testing. Results show that the fracture mode of the screws is brittle. There is no obvious relation to hydrogen-induced brittle. The main reason for the fracture of titanium alloy screws is internal defects, around which oxygen content is high, increasing brittleness. The internal defects of screws result from grain boundary cracking caused by hot forging. Full article
Figures

Figure 1

Open AccessArticle Porous Alpha-Tricalcium Phosphate with Immobilized Basic Fibroblast Growth Factor Enhances Bone Regeneration in a Canine Mandibular Bone Defect Model
Materials 2016, 9(10), 853; doi:10.3390/ma9100853
Received: 14 July 2016 / Revised: 5 October 2016 / Accepted: 13 October 2016 / Published: 19 October 2016
Cited by 1 | PDF Full-text (5497 KB) | HTML Full-text | XML Full-text
Abstract
The effect of porous alpha-tricalcium phosphate (α-TCP) with immobilized basic fibroblast growth factor (bFGF) on bone regeneration was evaluated in a canine mandibular bone defect model. Identical bone defects were made in the canine mandible; six defects in each animal were filled with
[...] Read more.
The effect of porous alpha-tricalcium phosphate (α-TCP) with immobilized basic fibroblast growth factor (bFGF) on bone regeneration was evaluated in a canine mandibular bone defect model. Identical bone defects were made in the canine mandible; six defects in each animal were filled with porous α-TCP with bFGF bound via heparin (bFGF group), whereas the other was filled with unmodified porous α-TCP (control group). Micro-computed tomography and histological evaluation were performed two, four and eight weeks after implantation. The bone mineral density of the bFGF group was higher than that of the control group at each time point (p < 0.05), and the bone mineral content of the bFGF group was higher than that of the control group at four and eight weeks (p < 0.05). Histological evaluation two weeks after implantation revealed that the porous α-TCP had degraded and bone had formed on the surface of α-TCP particles in the bFGF group. At eight weeks, continuous cortical bone with a Haversian structure covered the top of bone defects in the bFGF group. These findings demonstrate that porous α-TCP with immobilized bFGF can promote bone regeneration. Full article
(This article belongs to the Section Biomaterials)
Figures

Figure 1

Open AccessArticle Synthesis and Characterization of Poly(Ethylene Glycol) Based Thermo-Responsive Hydrogels for Cell Sheet Engineering
Materials 2016, 9(10), 854; doi:10.3390/ma9100854
Received: 7 September 2016 / Revised: 14 October 2016 / Accepted: 14 October 2016 / Published: 20 October 2016
Cited by 3 | PDF Full-text (4493 KB) | HTML Full-text | XML Full-text
Abstract
The swelling properties and thermal transition of hydrogels can be tailored by changing the hydrophilic-hydrophobic balance of polymer networks. Especially, poly(N-isopropylacrylamide) (PNIPAm) has received attention as thermo-responsive hydrogels for tissue engineering because its hydrophobicity and swelling property are transited around body
[...] Read more.
The swelling properties and thermal transition of hydrogels can be tailored by changing the hydrophilic-hydrophobic balance of polymer networks. Especially, poly(N-isopropylacrylamide) (PNIPAm) has received attention as thermo-responsive hydrogels for tissue engineering because its hydrophobicity and swelling property are transited around body temperature (32 °C). In this study, we investigated the potential of poly(ethylene glycol) diacrylate (PEGDA) as a hydrophilic co-monomer and crosslinker of PNIPAm to enhance biological properties of PNIPAm hydrogels. The swelling ratios, lower critical solution temperature (LCST), and internal pore structure of the synthesized p(NIPAm-co-PEGDA) hydrogels could be varied with changes in the molecular weight of PEGDA and the co-monomer ratios (NIPAm to PEGDA). We found that increasing the molecular weight of PEGDA showed an increase of pore sizes and swelling ratios of the hydrogels. In contrast, increasing the weight ratio of PEGDA under the same molecular weight condition increased the crosslinking density and decreased the swelling ratios of the hydrogels. Further, to evaluate the potential of these hydrogels as cell sheets, we seeded bovine chondrocytes on the p(NIPAm-co-PEGDA) hydrogels and observed the proliferation of the seed cells and their detachment as a cell sheet upon a decrease in temperature. Based on our results, we confirmed that p(NIPAm-co-PEGDA) hydrogels could be utilized as cell sheets with enhanced cell proliferation performance. Full article
(This article belongs to the Special Issue Smart Biomaterials and Biointerfaces)
Figures

Figure 1

Open AccessFeature PaperArticle Synthesis of CdSe Quantum Dots Using Fusarium oxysporum
Materials 2016, 9(10), 855; doi:10.3390/ma9100855
Received: 10 August 2016 / Revised: 13 September 2016 / Accepted: 11 October 2016 / Published: 20 October 2016
Cited by 2 | PDF Full-text (2820 KB) | HTML Full-text | XML Full-text
Abstract
CdSe quantum dots are often used in industry as fluorescent materials. In this study, CdSe quantum dots were synthesized using Fusarium oxysporum. The cadmium and selenium concentration, pH, and temperature for the culture of F. oxysporum (Fusarium oxysporum) were optimized
[...] Read more.
CdSe quantum dots are often used in industry as fluorescent materials. In this study, CdSe quantum dots were synthesized using Fusarium oxysporum. The cadmium and selenium concentration, pH, and temperature for the culture of F. oxysporum (Fusarium oxysporum) were optimized for the synthesis, and the CdSe quantum dots obtained from the mycelial cells of F. oxysporum were observed by transmission electron microscopy. Ultra-thin sections of F. oxysporum showed that the CdSe quantum dots were precipitated in the intracellular space, indicating that cadmium and selenium ions were incorporated into the cell and that the quantum dots were synthesized with intracellular metabolites. To reveal differences in F. oxysporum metabolism, cell extracts of F. oxysporum, before and after CdSe synthesis, were compared using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results suggested that the amount of superoxide dismutase (SOD) decreased after CdSe synthesis. Fluorescence microscopy revealed that cytoplasmic superoxide increased significantly after CdSe synthesis. The accumulation of superoxide may increase the expression of various metabolites that play a role in reducing Se4+ to Se2− and inhibit the aggregation of CdSe to make nanoparticles. Full article
(This article belongs to the Special Issue Biological and Synthetic Organic–Inorganic Composite Materials)
Figures

Open AccessArticle Tribological Performance of Green Lubricant Enhanced by Sulfidation IF-MoS2
Materials 2016, 9(10), 856; doi:10.3390/ma9100856
Received: 12 August 2016 / Revised: 5 October 2016 / Accepted: 17 October 2016 / Published: 21 October 2016
Cited by 4 | PDF Full-text (4402 KB) | HTML Full-text | XML Full-text
Abstract
Biopolymers reinforced with nanoparticle (NP) additives are widely used in tribological applications. In this study, the effect of NP additives on the tribological properties of a green lubricant hydroxypropyl methylcellulose (HPMC) composite was investigated. The IF-MoS2 NPs were prepared using the newly
[...] Read more.
Biopolymers reinforced with nanoparticle (NP) additives are widely used in tribological applications. In this study, the effect of NP additives on the tribological properties of a green lubricant hydroxypropyl methylcellulose (HPMC) composite was investigated. The IF-MoS2 NPs were prepared using the newly developed gas phase sulfidation method to form a multilayered, polyhedral structure. The number of layers and crystallinity of IF-MoS2 increased with sulfidation time and temperature. The dispersity of NPs in the HPMC was investigated using Raman and EDS mapping and showed great uniformity. The use of NPs with HPMC enhanced the tribological performance of the composites as expected. The analysis of the worn surface shows that the friction behavior of the HPMC composite with added NPs is very sensitive to the NP structure. The wear mechanisms vary with NP structure and depend on their lubricating behaviors. Full article
(This article belongs to the Special Issue Selected Papers from IMETI2016)
Figures

Figure 1

Open AccessArticle Gold Nanoparticle-Based Colorimetric and Electrochemical Methods for Dipeptidyl Peptidase-IV Activity Assay and Inhibitor Screening
Materials 2016, 9(10), 857; doi:10.3390/ma9100857
Received: 3 September 2016 / Revised: 30 September 2016 / Accepted: 13 October 2016 / Published: 21 October 2016
Cited by 5 | PDF Full-text (4239 KB) | HTML Full-text | XML Full-text
Abstract
We presented the colorimetric and electrochemical methods for determination of the dipeptidyl peptidase-IV (DPP-IV) activity and screening of its inhibitor using gold nanoparticle (AuNP) as the probe. In the colorimetric assay, the substrate peptide with a sequence of Arg-Pro-Arg induced the aggregation and
[...] Read more.
We presented the colorimetric and electrochemical methods for determination of the dipeptidyl peptidase-IV (DPP-IV) activity and screening of its inhibitor using gold nanoparticle (AuNP) as the probe. In the colorimetric assay, the substrate peptide with a sequence of Arg-Pro-Arg induced the aggregation and color change of AuNPs, whereas cleavage of the peptide by DPP-IV prevented the aggregation of AuNPs. Furthermore, the aggregation of AuNPs in the solution was easily initiated on a solid/liquid (electrode/electrolyte) surface, which induced a decrease in the electron-transfer resistance. However, once the peptide was clipped by DPP-IV, the assembly of AuNPs on electrode surface was prevented. Consequently, a higher electron-transfer resistance was observed. The colorimetric and electrochemical assays allowed for the determination of DPP-IV with the detection limits of 70 μU/mL and 0.55 μU/mL, respectively. Meanwhile, the proposed methods were used to determine DPP-IV inhibitor with satisfactory results. Both the colorimetric and electrochemical methods are simple, rapid and sufficiently sensitive for DPP-IV activity assay and inhibitor screening. The results also demonstrated that the AuNP-based colorimetric assay could be converted into an enhanced surface tethered electrochemical assay with improving sensitivity. The simple detection principle may be extended to the design of other peptidases biosensors with easy manipulation procedures. Full article
(This article belongs to the Special Issue Noble Metal Nanoparticles)
Figures

Figure 1

Open AccessArticle An In-Depth Investigation into the Physicochemical, Thermal, Microstructural, and Rheological Properties of Petroleum and Natural Asphalts
Materials 2016, 9(10), 859; doi:10.3390/ma9100859
Received: 14 August 2016 / Revised: 29 September 2016 / Accepted: 17 October 2016 / Published: 21 October 2016
PDF Full-text (3895 KB) | HTML Full-text | XML Full-text
Abstract
Over the last decade, unexpected and sudden pavement failures have occurred in several provinces in South Korea. Some of these failures remain unexplained, further illustrating the gaps in our knowledge about binder chemistry. To prevent premature pavement distress and enhance road performance, it
[...] Read more.
Over the last decade, unexpected and sudden pavement failures have occurred in several provinces in South Korea. Some of these failures remain unexplained, further illustrating the gaps in our knowledge about binder chemistry. To prevent premature pavement distress and enhance road performance, it is imperative to provide an adequate characterization of asphalt. For this purpose, the current research aims at inspecting the chemistry, microstructure, thermal, and physico-rheological properties of two types of asphalt, namely petroleum asphalt (PA) and natural asphalt (NA). The binders were extensively investigated by using elemental analysis, thin-layer chromatography with flame ionization detection (TLC-FID), matrix-assisted laser desorption ionization time-of-fight mass spectroscopy (MALDI-TOF-MS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), Nuclear magnetic resonance spectroscopy (1H-NMR), ultraviolet and visible spectroscopy (UV-VIS), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), penetration, softening point, ductility, and viscosity tests. The findings of this research have revealed the distinct variations between the chemical compositions, microstructures, and thermo-rheological properties of the two asphalts and provided valuable knowledge into the characteristics of the binders. Such insight has been effective in predicting the performance or distress of road pavement. This paper will, therefore, be of immediate interest to materials engineers in state highway agencies and asphalt industries. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Figures

Figure 1

Open AccessArticle A Model of BGA Thermal Fatigue Life Prediction Considering Load Sequence Effects
Materials 2016, 9(10), 860; doi:10.3390/ma9100860
Received: 20 August 2016 / Revised: 2 October 2016 / Accepted: 13 October 2016 / Published: 24 October 2016
PDF Full-text (11960 KB) | HTML Full-text | XML Full-text
Abstract
Accurate testing history data is necessary for all fatigue life prediction approaches, but such data is always deficient especially for the microelectronic devices. Additionally, the sequence of the individual load cycle plays an important role in physical fatigue damage. However, most of the
[...] Read more.
Accurate testing history data is necessary for all fatigue life prediction approaches, but such data is always deficient especially for the microelectronic devices. Additionally, the sequence of the individual load cycle plays an important role in physical fatigue damage. However, most of the existing models based on the linear damage accumulation rule ignore the sequence effects. This paper proposes a thermal fatigue life prediction model for ball grid array (BGA) packages to take into consideration the load sequence effects. For the purpose of improving the availability and accessibility of testing data, a new failure criterion is discussed and verified by simulation and experimentation. The consequences for the fatigue underlying sequence load conditions are shown. Full article
(This article belongs to the Special Issue Fracture and Fatigue Mechanics of Materials)
Figures

Figure 1

Review

Jump to: Research, Other

Open AccessReview 3D Bioprinting Technologies for Hard Tissue and Organ Engineering
Materials 2016, 9(10), 802; doi:10.3390/ma9100802
Received: 31 July 2016 / Revised: 19 September 2016 / Accepted: 22 September 2016 / Published: 27 September 2016
Cited by 7 | PDF Full-text (5557 KB) | HTML Full-text | XML Full-text | Correction
Abstract
Hard tissues and organs, including the bones, teeth and cartilage, are the most extensively exploited and rapidly developed areas in regenerative medicine field. One prominent character of hard tissues and organs is that their extracellular matrices mineralize to withstand weight and pressure. Over
[...] Read more.
Hard tissues and organs, including the bones, teeth and cartilage, are the most extensively exploited and rapidly developed areas in regenerative medicine field. One prominent character of hard tissues and organs is that their extracellular matrices mineralize to withstand weight and pressure. Over the last two decades, a wide variety of 3D printing technologies have been adapted to hard tissue and organ engineering. These 3D printing technologies have been defined as 3D bioprinting. Especially for hard organ regeneration, a series of new theories, strategies and protocols have been proposed. Some of the technologies have been applied in medical therapies with some successes. Each of the technologies has pros and cons in hard tissue and organ engineering. In this review, we summarize the advantages and disadvantages of the historical available innovative 3D bioprinting technologies for used as special tools for hard tissue and organ engineering. Full article
(This article belongs to the Special Issue 3D Printing for Biomedical Engineering)
Figures

Figure 1

Open AccessReview Applications of Graphene-Modified Electrodes in Microbial Fuel Cells
Materials 2016, 9(10), 807; doi:10.3390/ma9100807
Received: 18 August 2016 / Revised: 31 August 2016 / Accepted: 5 September 2016 / Published: 29 September 2016
Cited by 1 | PDF Full-text (5937 KB) | HTML Full-text | XML Full-text
Abstract
Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite
[...] Read more.
Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite oxide reduction methods, self-assembly methods, and chemical vapor deposition, are summarized. According to the different functions of the graphene-modified materials in the MFC anode and cathode chambers, a series of design concepts for MFC electrodes are assembled, e.g., enhancing the biocompatibility and improving the extracellular electron transfer efficiency for anode electrodes and increasing the active sites and strengthening the reduction pathway for cathode electrodes. In spite of the challenges of MFC electrodes, graphene-modified electrodes are promising for MFC development to address the reduction in efficiency brought about by organic waste by converting it into electrical energy. Full article
(This article belongs to the Special Issue Microbial Fuel Cells)
Figures

Figure 1

Open AccessReview A Review of PMMA Bone Cement and Intra‐Cardiac Embolism
Materials 2016, 9(10), 821; doi:10.3390/ma9100821
Received: 3 September 2016 / Accepted: 22 September 2016 / Published: 6 October 2016
Cited by 2 | PDF Full-text (2928 KB) | HTML Full-text | XML Full-text
Abstract
Percutaneous vertebroplasty procedure is of major importance, given the significantly increasing aging population and the higher number of orthopedic procedures related to vertebral compression fractures. Vertebroplasty is a complex technique involving the injection of polymethylmethacrylate (PMMA) into the compressed vertebral body for mechanical
[...] Read more.
Percutaneous vertebroplasty procedure is of major importance, given the significantly increasing aging population and the higher number of orthopedic procedures related to vertebral compression fractures. Vertebroplasty is a complex technique involving the injection of polymethylmethacrylate (PMMA) into the compressed vertebral body for mechanical stabilization of the fracture. Our understanding and ability to modify these mechanisms through alterations in cement material is rapidly evolving. However, the rate of cardiac complications secondary to PMMA injection and subsequent cement leakage has increased with time. The following review considers the main effects of PMMA bone cement on the heart, and the extent of influence of the materials on cardiac embolism. Clinically, cement leakage results in life‐threatening cardiac injury. The convolution of this outcome through an appropriate balance of complex material properties is highlighted via clinical case reports. Full article
(This article belongs to the Section Biomaterials)
Figures

Figure 1

Open AccessReview Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes
Materials 2016, 9(10), 858; doi:10.3390/ma9100858
Received: 30 July 2016 / Revised: 4 October 2016 / Accepted: 10 October 2016 / Published: 21 October 2016
Cited by 3 | PDF Full-text (7768 KB) | HTML Full-text | XML Full-text
Abstract
Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface
[...] Read more.
Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic), and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS) with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance. Full article
(This article belongs to the Special Issue Recent Advances in Materials for Solid Oxide Cells)
Figures

Figure 1

Other

Jump to: Research, Review

Open AccessLetter Evolution Law of Helium Bubbles in Hastelloy N Alloy on Post-Irradiation Annealing Conditions
Materials 2016, 9(10), 832; doi:10.3390/ma9100832
Received: 26 September 2016 / Revised: 9 October 2016 / Accepted: 12 October 2016 / Published: 14 October 2016
Cited by 1 | PDF Full-text (3728 KB) | HTML Full-text | XML Full-text
Abstract
This work reports on the evolution law of helium bubbles in Hastelloy N alloy on post-irradiation annealing conditions. After helium ion irradiation at room temperature and subsequent annealing at 600 °C (1 h), the transmission electron microscopy (TEM) micrograph indicates the presence of
[...] Read more.
This work reports on the evolution law of helium bubbles in Hastelloy N alloy on post-irradiation annealing conditions. After helium ion irradiation at room temperature and subsequent annealing at 600 °C (1 h), the transmission electron microscopy (TEM) micrograph indicates the presence of helium bubbles with size of 2 nm in the depth range of 0–300 nm. As for the sample further annealed at 850 °C (5 h), on one hand, a “Denuded Zone” (0–38 nm) with rare helium bubbles forms due to the decreased helium concentration. On the other hand, the “Ripening Zone” (38–108 nm) and “Coalescence Zone” (108–350 nm) with huge differences in size and separation of helium bubbles, caused by different coarsening rates, are observed. The mechanisms of “Ostwald ripening” and “migration and coalescence”, experimentally proved in this work, may explain these observations. Full article
(This article belongs to the Special Issue Modelling and Characterization of Defects in Metals)
Figures

Figure 1

Journal Contact

MDPI AG
Materials Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
E-Mail: 
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Materials Edit a special issue Review for Materials
logo
loading...
Back to Top