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Materials, Volume 9, Issue 12 (December 2016)

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Cover Story Synthetic and natural ligands that bind IgG are detailed in this paper. Bacterial proteins such as [...] Read more.
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Open AccessCommunication Well-Dispersed Co/CoO/C Nanospheres with Tunable Morphology as High-Performance Anodes for Lithium Ion Batteries
Materials 2016, 9(12), 955; doi:10.3390/ma9120955
Received: 17 October 2016 / Revised: 14 November 2016 / Accepted: 18 November 2016 / Published: 24 November 2016
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Abstract
Well-dispersed Co/CoO/C nanospheres have been designed and constructed through a facile electrospinning method with a strategy controlling the morphology of nanocomposites via adjusting the pre-oxidized and heat treatments. Scanning electron microscopy results reveal that the as-synthesized sample pre-oxidized at 275 °C shows better
[...] Read more.
Well-dispersed Co/CoO/C nanospheres have been designed and constructed through a facile electrospinning method with a strategy controlling the morphology of nanocomposites via adjusting the pre-oxidized and heat treatments. Scanning electron microscopy results reveal that the as-synthesized sample pre-oxidized at 275 °C shows better spherical morphology with a diameter of around 300 nm without conspicuous agglomeration. X-ray diffraction analysis confirms the coexistence of cobalt and cobalt monoxide in the sample. Furthermore, the electrochemical tests reveal that the sample pre-oxidized at 275 °C displays excellent cycling stability with only 0.016% loss per cycle even after 400 cycles at 1000 mA·g−1 and enhanced high-rate capability with a specific discharge capacity of 354 mA·g−1 at 2000 mA·g−1. Besides, the sample pre-oxidized at 275 °C shows a specific capacity of 755 mA·g−1 at 100 mA·g−1 after 95 cycles. The improved electrochemical performance has been ascribed to the well dispersion of nanospheres, the improved electronic conductivity, and the structural integrity contribution from the carbon and cobalt coexisting nanocomposite. The strategy for preparing well-dispersed nanospheres by adjusting pre-oxidized and annealing processes could have insight for other oxide nanosphere synthesis. Full article
(This article belongs to the Special Issue Microwave Absorbing and Energy Storage Materials)
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Open AccessArticle Microstructure and Characteristics of Calcium Phosphate Layers on Bioactive Oxide Surfaces of Air-Sintered Titanium Foams after Immersion in Simulated Body Fluid
Materials 2016, 9(12), 956; doi:10.3390/ma9120956
Received: 12 October 2016 / Revised: 10 November 2016 / Accepted: 17 November 2016 / Published: 24 November 2016
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Abstract
We propose a simple and low-cost process for the preparation of porous Ti foams through a sponge replication method using single-step air sintering at various temperatures. In this study, the apatite-forming ability of air-sintered Ti samples after 21 days of immersion in simulated
[...] Read more.
We propose a simple and low-cost process for the preparation of porous Ti foams through a sponge replication method using single-step air sintering at various temperatures. In this study, the apatite-forming ability of air-sintered Ti samples after 21 days of immersion in simulated body fluid (SBF) was investigated. The microstructures of the prepared Ca–P deposits were examined by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, and cross-sectional transmission electron microscopy (TEM). In contrast to the control sample sintered in vacuum, which was found to have the simple hexagonal α-Ti phase, the air-sintered samples contained only the rutile phase. High intensities of XRD peaks for rutile TiO2 were obtained with samples sintered at 1000 °C. Moreover, the air-sintered Ti samples had a greater apatite-forming ability than that of the Ti sample sintered in vacuum. Ti samples sintered at 900 and 1000 °C had large aggregated spheroidal particles on their surfaces after immersion in SBF for 21 days. Combined XRD, energy-dispersive X-ray spectroscopy, FTIR spectroscopy, and TEM results suggest that the calcium phosphate deposited on the rutile TiO2 surfaces consist of carbonated calcium-deficient hydroxyapatite instead of octacalcium phosphate. Full article
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Open AccessArticle Effect of Electrical Discharge Machining on Stress Concentration in Titanium Alloy Holes
Materials 2016, 9(12), 957; doi:10.3390/ma9120957
Received: 16 September 2016 / Revised: 14 November 2016 / Accepted: 18 November 2016 / Published: 24 November 2016
Cited by 1 | PDF Full-text (6274 KB) | HTML Full-text | XML Full-text
Abstract
Titanium alloys have several advantages, such as a high strength-to-weight ratio. However, the machinability of titanium alloys is not as good as its mechanical properties. Many machining processes have been used to fabricate titanium alloys. Among these machining processes, electrical discharge machining (EDM)
[...] Read more.
Titanium alloys have several advantages, such as a high strength-to-weight ratio. However, the machinability of titanium alloys is not as good as its mechanical properties. Many machining processes have been used to fabricate titanium alloys. Among these machining processes, electrical discharge machining (EDM) has the advantage of processing efficiency. EDM is based on thermoelectric energy between a workpiece and an electrode. A pulse discharge occurs in a small gap between the workpiece and electrode. Then, the material from the workpiece is removed through melting and vaporization. However, defects such as cracks and notches are often detected at the boundary of holes fabricated using EDM and the irregular profile of EDM holes reduces product quality. In this study, an innovative method was proposed to estimate the effect of EDM parameters on the surface quality of the holes. The method combining the finite element method and image processing can rapidly evaluate the stress concentration factor of a workpiece. The stress concentration factor was assumed as an index of EDM process performance for estimating the surface quality of EDM holes. In EDM manufacturing processes, Ti-6Al-4V was used as an experimental material and, as process parameters, pulse current and pulse on-time were taken into account. The results showed that finite element simulations can effectively analyze stress concentration in EDM holes. Using high energy during EDM leads to poor hole quality, and the stress concentration factor of a workpiece is correlated to hole quality. The maximum stress concentration factor for an EDM hole was more than four times that for the same diameter of the undamaged hole. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle The Effect of UV Treatment on the Osteoconductive Capacity of Zirconia-Based Materials
Materials 2016, 9(12), 958; doi:10.3390/ma9120958
Received: 16 August 2016 / Revised: 14 November 2016 / Accepted: 17 November 2016 / Published: 24 November 2016
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Abstract
Objective: Improvements in the bioactivity of zirconia implants for accelerated healing and reduced morbidity have been of continuing interest in the fields of dentistry and orthopedic surgery. The aim of the present study was to examine whether UV treatment increases the osteoconductivity of
[...] Read more.
Objective: Improvements in the bioactivity of zirconia implants for accelerated healing and reduced morbidity have been of continuing interest in the fields of dentistry and orthopedic surgery. The aim of the present study was to examine whether UV treatment increases the osteoconductivity of zirconia-based materials. Materials and Methods: Smooth and rough zirconia-based disks and cylindrical implants were treated with UV light for 15 min and subsequently placed in rat femurs. Surface characterization was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Results: In vivo histomorphometry revealed that the percentage of bone-implant contact and the amount of bone volume, formed around UV-treated implants, increased by 3–7-fold for smooth surfaces and by 1.4–1.7-fold for rough surfaces compared to non-treated specimens at Weeks 2 and 4 of healing, respectively. A biomechanical test showed that UV treatment accelerated the establishment of bone-zirconia integration and enhanced the strength of the bone-implant interface by two-fold. Additionally, surface characterization of the zirconia disks revealed that UV treatment decreased the amount of surface carbon and converted the hydrophilic status from hydrophobic to superhydrophilic. Conclusions: This study indicates that UV light pretreatment enhances the osteoconductive capacity of zirconia-based materials. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Synthesis and In Vitro Activity Assessment of Novel Silicon Oxycarbide-Based Bioactive Glasses
Materials 2016, 9(12), 959; doi:10.3390/ma9120959
Received: 18 October 2016 / Revised: 12 November 2016 / Accepted: 15 November 2016 / Published: 24 November 2016
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Abstract
Novel bioactive glasses based on a Ca- and Mg-modified silicon oxycarbide (SiCaMgOC) were prepared from a polymeric single-source precursor, and their in vitro activity towards hydroxyapatite mineralization was investigated upon incubating the samples in simulated body fluid (SBF) at 37 °C. The as-prepared
[...] Read more.
Novel bioactive glasses based on a Ca- and Mg-modified silicon oxycarbide (SiCaMgOC) were prepared from a polymeric single-source precursor, and their in vitro activity towards hydroxyapatite mineralization was investigated upon incubating the samples in simulated body fluid (SBF) at 37 °C. The as-prepared materials exhibit an outstanding resistance against devitrification processes and maintain their amorphous nature even after exposure to 1300 °C. The X-ray diffraction (XRD) analysis of the SiCaMgOC samples after the SBF test showed characteristic reflections of apatite after only three days, indicating a promising bioactivity. The release kinetics of the Ca2+ and Mg2+ and the adsorption of H+ after immersion of SiCaMgOC in simulated body fluid for different soaking times were analyzed via optical emission spectroscopy. The results show that the mechanism of formation of apatite on the surface of the SiCaMgOC powders is similar to that observed for standard (silicate) bioactive glasses. A preliminary cytotoxicity investigation of the SiOC-based bioactive glasses was performed in the presence of mouse embryonic fibroblasts (MEF) as well as human embryonic kidney cells (HEK-293). Due to their excellent high-temperature crystallization resistance in addition to bioactivity, the Ca- and Mg-modified SiOC glasses presented here might have high potential in applications related to bone repair and regeneration. Full article
(This article belongs to the Special Issue Bioceramics 2016)
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Open AccessArticle Rolling Contact Fatigue Performances of Carburized and High-C Nanostructured Bainitic Steels
Materials 2016, 9(12), 960; doi:10.3390/ma9120960
Received: 26 October 2016 / Revised: 22 November 2016 / Accepted: 22 November 2016 / Published: 25 November 2016
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Abstract
In the present work, the nanostructured bainitic microstructures were obtained at the surfaces of a carburized steel and a high-C steel. The rolling contact fatigue (RCF) performances of the two alloy steels with the same volume fraction of undissolved carbide were studied under
[...] Read more.
In the present work, the nanostructured bainitic microstructures were obtained at the surfaces of a carburized steel and a high-C steel. The rolling contact fatigue (RCF) performances of the two alloy steels with the same volume fraction of undissolved carbide were studied under lubrication. Results show that the RCF life of the carburized nanostructured bainitic steel is superior to that of the high-C nanostructured bainitic steel in spite of the chemical composition, phase constituent, plate thickness of bainitic ferrite, hardness, and residual compressive stress value of the contact surfaces of the two steels under roughly similar conditions. The excellent RCF performance of the carburized nanostructured bainitic steel is mainly attributed to the following reasons: finer carbide dispersion distribution in the top surface, the higher residual compressive stress values in the carburized layer, the deeper residual compressive stress layer, the higher work hardening ability, the larger amount of retained austenite transforming into martensite at the surface and the more stable untransformed retained austenite left in the top surface of the steel. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Open AccessArticle Thermal Shock and Oxidation Behavior of HiPIMS TiAlN Coatings Grown on Ti-48Al-2Cr-2Nb Intermetallic Alloy
Materials 2016, 9(12), 961; doi:10.3390/ma9120961
Received: 23 September 2016 / Revised: 7 November 2016 / Accepted: 21 November 2016 / Published: 25 November 2016
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Abstract
A High Power Impulse Magnetron Sputtering (HiPIMS) method for depositing TiAlN environmental barrier coatings on the surface of Ti-48Al-2Cr-2Nb alloy was developed in view of their exploitation in turbine engines. Three differently engineered TiAlN films were processed and their performance compared. Bare intermetallic
[...] Read more.
A High Power Impulse Magnetron Sputtering (HiPIMS) method for depositing TiAlN environmental barrier coatings on the surface of Ti-48Al-2Cr-2Nb alloy was developed in view of their exploitation in turbine engines. Three differently engineered TiAlN films were processed and their performance compared. Bare intermetallic alloy coupons and coated specimens were submitted to thermal cycling under oxidizing atmosphere up to 850 °C or 950 °C, at high heating and cooling rates. For this purpose, a burner rig able to simulate the operating conditions of the different stages of turbine engines was used. Microstructures of the samples were compared before and after each test using several techniques (microscopy, XRD, and XPS). Coating-intermetallic substrate adhesion and tribological properties were investigated too. All the TiAlN films provided a remarkable increase in oxidation resistance. Good adhesion properties were observed even after repeated thermal shocks. HiPIMS pretreatments of the substrate surfaces performed before the coating deposition significantly affected the oxidation rate, the oxide layer composition and the coating/substrate adhesion. Full article
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Open AccessArticle Acoustic Behavior of Hollow Blocks and Bricks Made of Concrete Doped with Waste-Tire Rubber
Materials 2016, 9(12), 962; doi:10.3390/ma9120962
Received: 6 October 2016 / Revised: 21 November 2016 / Accepted: 22 November 2016 / Published: 26 November 2016
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Abstract
In this paper, we investigate the acoustic behaviour of building elements made of concrete doped with waste-tire rubber. Three different mixtures were created, with 0%, 10%, and 20% rubber in their composition. Bricks, lattice joists, and hollow blocks were manufactured with each mixture,
[...] Read more.
In this paper, we investigate the acoustic behaviour of building elements made of concrete doped with waste-tire rubber. Three different mixtures were created, with 0%, 10%, and 20% rubber in their composition. Bricks, lattice joists, and hollow blocks were manufactured with each mixture, and three different cells were built and tested against aerial and impact noise. The values of the global acoustic isolation and the reduction of the sound pressure level of impacts were measured. Results proved that highly doped elements are an excellent option to isolate low frequency sounds, whereas intermediate and standard elements constitute a most interesting option to block middle and high frequency sounds. In both cases, the considerable amount of waste-tire rubber recycled could justify the employment of the doped materials for the sake of the environment. Full article
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Open AccessArticle Tribocorrosion Failure Mechanism of TiN/SiOx Duplex Coating Deposited on AISI304 Stainless Steel
Materials 2016, 9(12), 963; doi:10.3390/ma9120963
Received: 11 October 2016 / Revised: 13 November 2016 / Accepted: 21 November 2016 / Published: 26 November 2016
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Abstract
TiN/SiOx duplex coatings were synthesized on AISI304 stainless steel by plasma immersion ion implantation and deposition (PIIID) followed by radio frequency magnetron sputtering (RFMS). The microstructure and tribocorrosion failure behaviors of the duplex coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy,
[...] Read more.
TiN/SiOx duplex coatings were synthesized on AISI304 stainless steel by plasma immersion ion implantation and deposition (PIIID) followed by radio frequency magnetron sputtering (RFMS). The microstructure and tribocorrosion failure behaviors of the duplex coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, reciprocating-sliding tribometer, and electrochemical tests. The as-deposited duplex coating had a two-layered columnar growth structure consisting of face-centered cubic TiN and amorphous SiOx. Sliding tests showed that the TiN interlayer had good adhesion with the substrate, but the SiOx layer suffered from severe delamination failure. Friction force induced a number of micro-cracks in the coating, which provided channels for the diffusion of NaCl solution. The tribocorrosion test showed that the duplex coating exhibited a lower wear-performance in NaCl solution than in ambient atmosphere. Multi-scale chloride ion corrosion occurred simultaneously and substantially degraded the bonding strength of the columnar crystals or neighboring layers. Force-corrosion synergy damage eventually led to multi-degradation failure of the duplex coating. The presented results provide a comprehensive understanding of the tribocorrosion failure mechanism in coatings with duplex architecture. Full article
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Open AccessArticle Effect of Pre-Oxidation Treatment of Nano-SiC Particulates on Microstructure and Mechanical Properties of SiC/Mg-8Al-1Sn Composites Fabricated by Powder Metallurgy Combined with Hot Extrusion
Materials 2016, 9(12), 964; doi:10.3390/ma9120964
Received: 23 September 2016 / Revised: 17 November 2016 / Accepted: 23 November 2016 / Published: 26 November 2016
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Abstract
Nano-SiC particulates (n-SiCp) reinforced Mg-8Al-1Sn (AT81) composites with different pre-oxidation parameters were fabricated by powder metallurgy (P/M) process combined with hot extrusion. The effects of pre-oxidization treatment of n-SiCp on the microstructure and tensile properties of 0.5 vol % n-SiC
[...] Read more.
Nano-SiC particulates (n-SiCp) reinforced Mg-8Al-1Sn (AT81) composites with different pre-oxidation parameters were fabricated by powder metallurgy (P/M) process combined with hot extrusion. The effects of pre-oxidization treatment of n-SiCp on the microstructure and tensile properties of 0.5 vol % n-SiCp/AT81 composites were investigated accordingly. The distribution of n-SiCp with different pre-oxidation parameters was homogeneous in the composites. Moreover, it was found that a thin MgAl2O4 layer formed at the interface when the n-SiCp were pre-oxidized at 1073 K for 2 h, while the MgAl2O4 layer became much thicker with pre-oxidization temperature increasing to 1273 K for 2 h. After an appropriate pre-oxidization treatment of n-SiCp at 1073 K for 2 h, the as-extruded 0.5 vol % n-SiCp/AT81 composites exhibited an enhanced strength. It was found that the yield strength (YS) and ultimate tensile strength (UTS) increased from 168 MPa and 311 MPa to 255 MPa and 393 MPa compared with the as-extruded AT81 alloy, reflecting 51.8% and 26.4% increments, respectively. The improvement of mechanical properties should be mainly attributed to the grain refinement and homogeneous distribution of n-SiCp in the composites. Moreover, a well-bonded interface and the formation of an appropriate amount of interfacial product (MgAl2O4) benefited the material’s mechanical properties. Full article
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Open AccessArticle Simple One-Pot Syntheses and Characterizations of Free Fluoride- and Bifluoride-Containing Polymers Soluble in Non-Aqueous Solvents
Materials 2016, 9(12), 965; doi:10.3390/ma9120965
Received: 27 October 2016 / Revised: 18 November 2016 / Accepted: 22 November 2016 / Published: 30 November 2016
Cited by 1 | PDF Full-text (6793 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
One of the problems that arise with bifluoride- or fluoride-containing compounds is their poor solubility in non-aqueous solvents. We report herein a facile one-pot synthesis and the chemical analysis of fluoride/bifluoride-containing polymers, which are soluble in MeCN. Different polymers, such as Polyvinylacetate or
[...] Read more.
One of the problems that arise with bifluoride- or fluoride-containing compounds is their poor solubility in non-aqueous solvents. We report herein a facile one-pot synthesis and the chemical analysis of fluoride/bifluoride-containing polymers, which are soluble in MeCN. Different polymers, such as Polyvinylacetate or Polyethylene imine and saccharides, such as maltodextrin, were complexed with ammonium (bi)fluoride using hydrogen bonds to form the desired (bi)fluoride-containing compounds. The newly formed hydrogen bonding (bi)fluoride-doped polymer matrices were analyzed using infrared and nuclear magnetic resonance spectroscopies, and X-ray diffraction. The promising materials also underwent impedance spectroscopy, conductivity measurements and preliminary tests as electrolytes for room temperature fluoride ion batteries along with an analysis of their performance. Full article
(This article belongs to the Section Materials for Energy Applications)
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Open AccessArticle Neo-Geometric Copper Nanocrystals by Competitive, Dual Surfactant-Mediated Facet Adsorption Controlling Skin Permeation
Materials 2016, 9(12), 966; doi:10.3390/ma9120966
Received: 14 October 2016 / Revised: 18 November 2016 / Accepted: 21 November 2016 / Published: 28 November 2016
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Abstract
Neogeometric copper nanoparticles (CuNPs) have various applications yet its synthesis still proves to be challenging with regards to self-assembly and uniformity control. This study aimed to synthesize shape-specific CuNPs in the biomedical application of ascertaining skin permeation and retention of the CuNPs as
[...] Read more.
Neogeometric copper nanoparticles (CuNPs) have various applications yet its synthesis still proves to be challenging with regards to self-assembly and uniformity control. This study aimed to synthesize shape-specific CuNPs in the biomedical application of ascertaining skin permeation and retention of the CuNPs as a drug delivery system. The approach to the shape design involved the dual control of two surfactants to direct the shape organisation of the nanoparticles (NPs) while an interesting aspect of the study showed the competitive adsorption of the surfactants onto the nanocrystal facets to direct facet growth. The resulting copper nanoparticles were characterised using X-ray diffraction (XRD) and electron diffraction spectra analysis (EDS) for elemental and crystalline analysis. Thermogravimetric Analysis (TGA) identified the degradation of the surfactant coat and the synthesis of a novel copper-polymer complex and extensive transmission electron microscopy (TEM) was conducted to determine the nanoparticle morphology. Epidermal skin tissue served as the model for permeation studies of five idealistic nano-geometries and investigated its application in drug delivery with regards to cellular internalisation and transbarrier transport of the geometric CuNPs. A mechanistic consideration for shape control is discussed. Full article
(This article belongs to the Special Issue Noble Metal Nanoparticles)
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Open AccessArticle ZrB2-CNTs Nanocomposites Fabricated by Spark Plasma Sintering
Materials 2016, 9(12), 967; doi:10.3390/ma9120967
Received: 16 October 2016 / Revised: 18 November 2016 / Accepted: 22 November 2016 / Published: 29 November 2016
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Abstract
ZrB2-based nanocomposites with and without carbon nanotubes (CNTs) as reinforcement were prepared at 1600 °C by spark plasma sintering. The effects of CNTs on the microstructure and mechanical properties of nano-ZrB2 matrix composites were studied. The results indicated that adding
[...] Read more.
ZrB2-based nanocomposites with and without carbon nanotubes (CNTs) as reinforcement were prepared at 1600 °C by spark plasma sintering. The effects of CNTs on the microstructure and mechanical properties of nano-ZrB2 matrix composites were studied. The results indicated that adding CNTs can inhibit the abnormal grain growth of ZrB2 grains and improve the fracture toughness of the composites. The toughness mechanisms were crack deflection, crack bridging, debonding, and pull-out of CNTs. The experimental results of the nanograined ZrB2-CNTs composites were compared with those of the micro-grained ZrB2-CNTs composites. Due to the small size and surface effects, the nanograined ZrB2-CNTs composites exhibited stronger mechanical properties: the hardness, flexural strength and fracture toughness were 18.7 ± 0.2 GPa, 1016 ± 75 MPa, and 8.5 ± 0.4 MPa·m1/2, respectively. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Open AccessArticle Origin of Activity and Stability Enhancement for Ag3PO4 Photocatalyst after Calcination
Materials 2016, 9(12), 968; doi:10.3390/ma9120968
Received: 30 September 2016 / Revised: 21 November 2016 / Accepted: 23 November 2016 / Published: 29 November 2016
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Abstract
Pristine Ag3PO4 microspheres were synthesized by a co-precipitation method, followed by being calcined at different temperatures to obtain a series of calcined Ag3PO4 photocatalysts. This work aims to investigate the origin of activity and stability enhancement for
[...] Read more.
Pristine Ag3PO4 microspheres were synthesized by a co-precipitation method, followed by being calcined at different temperatures to obtain a series of calcined Ag3PO4 photocatalysts. This work aims to investigate the origin of activity and stability enhancement for Ag3PO4 photocatalyst after calcination based on the systematical analyses of the structures, morphologies, chemical states of elements, oxygen defects, optical absorption properties, separation and transfer of photogenerated electron-hole pairs, and active species. The results indicate that oxygen vacancies (VO˙˙) are created and metallic silver nanoparticles (Ag NPs) are formed by the reaction of partial Ag+ in Ag3PO4 semiconductor with the thermally excited electrons from Ag3PO4 and then deposited on the surface of Ag3PO4 microspheres during the calcination process. Among the calcined Ag3PO4 samples, the Ag3PO4-200 sample exhibits the best photocatalytic activity and greatly enhanced photocatalytic stability for photodegradation of methylene blue (MB) solution under visible light irradiation. Oxygen vacancies play a significantly positive role in the enhancement of photocatalytic activity, while metallic Ag has a very important effect on improving the photocatalytic stability. Overall, the present work provides some powerful evidences and a deep understanding on the origin of activity and stability enhancement for the Ag3PO4 photocatalyst after calcination. Full article
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Open AccessArticle Assessment of Effects of Si-Ca-P Biphasic Ceramic on the Osteogenic Differentiation of a Population of Multipotent Adult Human Stem Cells
Materials 2016, 9(12), 969; doi:10.3390/ma9120969
Received: 12 October 2016 / Revised: 11 November 2016 / Accepted: 15 November 2016 / Published: 29 November 2016
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Abstract
A new type of bioceramic with osteogenic properties, suitable for hard tissue regeneration, was synthesised. The ceramic was designed and obtained in the Nurse’s A-phase-silicocarnotite subsystem. The selected composition was that corresponding to the eutectoid 28.39 wt % Nurse’s A-phase-71.61 wt % silicocarnotite
[...] Read more.
A new type of bioceramic with osteogenic properties, suitable for hard tissue regeneration, was synthesised. The ceramic was designed and obtained in the Nurse’s A-phase-silicocarnotite subsystem. The selected composition was that corresponding to the eutectoid 28.39 wt % Nurse’s A-phase-71.61 wt % silicocarnotite invariant point. We report the effect of Nurse’s A-phase-silicocarnotite ceramic on the capacity of multipotent adult human mesenchymal stem cells (ahMSCs) cultured under experimental conditions, known to adhere, proliferate and differentiate into osteoblast lineage cells. The results at long-term culture (28 days) on the material confirmed that the undifferentiated ahMSCs cultured and in contact with the material surface adhered, spread, proliferated, and produced a mineralised extracellular matrix on the studied ceramic, and finally acquired an osteoblastic phenotype. These findings indicate that it underwent an osteoblast differentiation process. All these findings were more significant than when cells were grown on plastic, in the presence and absence of this osteogenic supplement, and were more evident when this supplement was present in the growth medium (GM). The ceramic evaluated herein was bioactive, cytocompatible and capable of promoting the proliferation and differentiation of undifferentiated ahMSCs into osteoblasts, which may be important for bone integration into the clinical setting. Full article
(This article belongs to the Special Issue Bioceramics 2016)
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Open AccessArticle On the Sr1−xBaxFeO2F Oxyfluoride Perovskites: Structure and Magnetism from Neutron Diffraction and Mössbauer Spectroscopy
Materials 2016, 9(12), 970; doi:10.3390/ma9120970
Received: 3 October 2016 / Revised: 18 November 2016 / Accepted: 22 November 2016 / Published: 29 November 2016
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Abstract
Four oxyfluorides of the title series (x = 0.00, 0.25, 0.50, 0.75) have been stabilized by topotactic treatment of perovskite precursors Sr1−xBaxFeO3−δ prepared by soft-chemistry procedures, yielding reactive materials that can easily incorporate a substantial amount
[...] Read more.
Four oxyfluorides of the title series (x = 0.00, 0.25, 0.50, 0.75) have been stabilized by topotactic treatment of perovskite precursors Sr1−xBaxFeO3−δ prepared by soft-chemistry procedures, yielding reactive materials that can easily incorporate a substantial amount of F atoms at moderate temperatures, thus avoiding the stabilization of competitive SrF2 and BaF2 parasitic phases. XRD and Neutron Powder Diffraction (NPD) measurements assess the phase purity and yield distinct features concerning the unit cell parameters’ variation, the Sr and Ba distribution, the stoichiometry of the anionic sublattice and the anisotropic displacement factors for O and F atoms. The four oxyfluorides are confirmed to be cubic in all of the compositional range, the unit cell parameters displaying Vergard’s law. All of the samples are magnetically ordered above room temperature; the magnetic structure is always G-type antiferromagnetic, as shown from NPD data. The ordered magnetic moments are substantially high, around 3.5 μB, even at room temperature (RT). Temperature-dependent Mössbauer data allow identifying Fe3+ in all of the samples, thus confirming the Sr1−xBaxFeO2F stoichiometry. The fit of the magnetic hyperfine field vs. temperature curve yields magnetic ordering TN temperatures between 740 K (x = 0.00) and 683 K (x = 0.75). These temperatures are substantially higher than those reported before for some of the samples, assessing for stronger Fe-Fe superexchange interactions for these specimens prepared by fluorination of citrate precursors in mild conditions. Full article
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Open AccessArticle Influence of Hot Plastic Deformation in γ and (γ + α) Area on the Structure and Mechanical Properties of High-Strength Low-Alloy (HSLA) Steel
Materials 2016, 9(12), 971; doi:10.3390/ma9120971
Received: 29 July 2016 / Revised: 18 November 2016 / Accepted: 28 November 2016 / Published: 30 November 2016
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Abstract
The main goal of this study was to develop a new processing technology for a high-strength low-alloy (HSLA) steel in order to maximize the mechanical properties attainable at its low alloy levels. Samples of the steel were processed using thermal deformation schedules carried
[...] Read more.
The main goal of this study was to develop a new processing technology for a high-strength low-alloy (HSLA) steel in order to maximize the mechanical properties attainable at its low alloy levels. Samples of the steel were processed using thermal deformation schedules carried out in single-phase (γ) and dual-phase (γ + α) regions. The samples were rolled at unconventional finishing temperatures, their final mechanical properties were measured, and their strength and plasticity behavior was analyzed. The resulting microstructures were observed using optical and transmission electron microscopy (TEM). They consisted of martensite, ferrite and (NbV)CN precipitates. The study also explored the process of ferrite formation and its influence on the mechanical properties of the material. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle High-Strength Ultra-Fine-Grained Hypereutectic Al-Si-Fe-X (X = Cr, Mn) Alloys Prepared by Short-Term Mechanical Alloying and Spark Plasma Sintering
Materials 2016, 9(12), 973; doi:10.3390/ma9120973
Received: 25 October 2016 / Revised: 17 November 2016 / Accepted: 24 November 2016 / Published: 30 November 2016
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Abstract
In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined
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In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined that the α-Al along with α-Al15(Fe,Cr)3Si2 or α-Al15(Fe,Mn)3Si2 phases were present, with dimensions below 130 nm. The highest hardness of 380 ± 7 HV5 was observed for the Al-20Si-10Fe-6Mn alloy, exceeding the hardness of the reference as-cast Al-12Si-1Cu-1 Mg-1Ni alloy (121 ± 2 HV5) by nearly a factor of three. Both of the prepared alloys showed exceptional thermal stability with the hardness remaining almost the same even after 100 h of annealing at 400 °C. Additionally, the compressive strengths of the Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn alloys reached 869 MPa and 887 MPa, respectively, and had virtually the same values of 870 MPa and 865 MPa, respectively, even after 100 h of annealing. More importantly, the alloys showed an increase in ductility at 400 °C, reaching several tens of percent. Thus, both of the investigated alloys showed better mechanical properties, including superior hardness, compressive strength and thermal stability, as compared to the reference Al-10Si-1Cu-1Mg-1Ni alloy, which softened remarkably, reducing its hardness by almost 50% to 63 ± 8 HV5. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle An Investigation of Sintering Parameters on Titanium Powder for Electron Beam Melting Processing Optimization
Materials 2016, 9(12), 974; doi:10.3390/ma9120974
Received: 13 September 2016 / Revised: 20 October 2016 / Accepted: 4 November 2016 / Published: 1 December 2016
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Abstract
Selective electron beam melting (SEBM) is a relatively new additive manufacturing technology for metallic materials. Specific to this technology is the sintering of the metal powder prior to the melting process. The sintering process has disadvantages for post-processing. The post-processing of parts produced
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Selective electron beam melting (SEBM) is a relatively new additive manufacturing technology for metallic materials. Specific to this technology is the sintering of the metal powder prior to the melting process. The sintering process has disadvantages for post-processing. The post-processing of parts produced by SEBM typically involves the removal of semi-sintered powder through the use of a powder blasting system. Furthermore, the sintering of large areas before melting decreases productivity. Current investigations are aimed at improving the sintering process in order to achieve better productivity, geometric accuracy, and resolution. In this study, the focus lies on the modification of the sintering process. In order to investigate and improve the sintering process, highly porous titanium test specimens with various scan speeds were built. The aim of this study was to decrease build time with comparable mechanical properties of the components and to remove the residual powder more easily after a build. By only sintering the area in which the melt pool for the components is created, an average productivity improvement of approx. 20% was achieved. Tensile tests were carried out, and the measured mechanical properties show comparatively or slightly improved values compared with the reference. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Performance of High Layer Thickness in Selective Laser Melting of Ti6Al4V
Materials 2016, 9(12), 975; doi:10.3390/ma9120975
Received: 22 October 2016 / Revised: 13 November 2016 / Accepted: 22 November 2016 / Published: 1 December 2016
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Abstract
To increase building rate and save cost, the selective laser melting (SLM) of Ti6Al4V with a high layer thickness (200 μm) and low cost coarse powders (53 μm–106 μm) at a laser power of 400 W is investigated in this preliminary study. A
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To increase building rate and save cost, the selective laser melting (SLM) of Ti6Al4V with a high layer thickness (200 μm) and low cost coarse powders (53 μm–106 μm) at a laser power of 400 W is investigated in this preliminary study. A relatively large laser beam with a diameter of 200 μm is utilized to produce a stable melt pool at high layer thickness, and the appropriate scanning track, which has a smooth surface with a shallow contact angle, can be obtained at the scanning speeds from 40 mm/s to 80 mm/s. By adjusting the hatch spacings, the density of multi-layer samples can be up to 99.99%, which is much higher than that achieved in previous studies about high layer thickness selective laser melting. Meanwhile, the building rate can be up to 7.2 mm3/s, which is about 2 times–9 times that of the commercial equipment. Besides, two kinds of defects are observed: the large un-melted defects and the small spherical micropores. The formation of the un-melted defects is mainly attributed to the inappropriate overlap rates and the unstable scanning tracks, which can be eliminated by adjusting the processing parameters. Nevertheless, the micropores cannot be completely eliminated. It is worth noting that the high layer thickness plays a key role on surface roughness rather than tensile properties during the SLM process. Although a sample with a relatively coarse surface is generated, the average values of yield strength, ultimate tensile strength, and elongation are 1050 MPa, 1140 MPa, and 7.03%, respectively, which are not obviously different than those with the thin layer thickness used in previous research; this is due to the similar metallurgical bonding and microstructure. Full article
(This article belongs to the Special Issue Metals for Additive Manufacturing)
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Open AccessArticle In Situ Soft X-ray Spectromicroscopy of Early Tricalcium Silicate Hydration
Materials 2016, 9(12), 976; doi:10.3390/ma9120976
Received: 3 November 2016 / Revised: 29 November 2016 / Accepted: 29 November 2016 / Published: 1 December 2016
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Abstract
The understanding and control of early hydration of tricalcium silicate (C3S) is of great importance to cement science and concrete technology. However, traditional characterization methods are incapable of providing morphological and spectroscopic information about in situ hydration at the nanoscale. Using
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The understanding and control of early hydration of tricalcium silicate (C3S) is of great importance to cement science and concrete technology. However, traditional characterization methods are incapable of providing morphological and spectroscopic information about in situ hydration at the nanoscale. Using soft X-ray spectromicroscopy, we report the changes in morphology and molecular structure of C3S at an early stage of hydration. In situ C3S hydration in a wet cell, beginning with induction (~1 h) and acceleration (~4 h) periods of up to ~8 h, was studied and compared with ex situ measurements in the deceleration period after 15 h of curing. Analysis of the near-edge X-ray absorption fine structure showed that the Ca binding energy and energy splitting of C3S changed rapidly in the early age of hydration and exhibited values similar to calcium silicate hydrate (C–S–H). The formation of C–S–H nanoseeds in the C3S solution and the development of a fibrillar C–S–H morphology on the C3S surface were visualized. Following this, silicate polymerization accompanied by C–S–H precipitation produced chemical shifts in the peaks of the main Si K edge and in multiple scattering. However, the silicate polymerization process did not significantly affect the Ca binding energy of C–S–H. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Modelling of Granular Fracture in Polycrystalline Materials Using Ordinary State-Based Peridynamics
Materials 2016, 9(12), 977; doi:10.3390/ma9120977
Received: 1 September 2016 / Revised: 7 November 2016 / Accepted: 22 November 2016 / Published: 2 December 2016
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Abstract
An ordinary state-based peridynamic formulation is developed to analyse cubic polycrystalline materials for the first time in the literature. This new approach has the advantage that no constraint condition is imposed on material constants as opposed to bond-based peridynamic theory. The formulation is
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An ordinary state-based peridynamic formulation is developed to analyse cubic polycrystalline materials for the first time in the literature. This new approach has the advantage that no constraint condition is imposed on material constants as opposed to bond-based peridynamic theory. The formulation is validated by first considering static analyses and comparing the displacement fields obtained from the finite element method and ordinary state-based peridynamics. Then, dynamic analysis is performed to investigate the effect of grain boundary strength, crystal size, and discretization size on fracture behaviour and fracture morphology. Full article
(This article belongs to the Special Issue Multiscale Methods and Application to Computational Materials Design)
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Open AccessArticle Engineering Characteristics of Chemically Treated Water-Repellent Kaolin
Materials 2016, 9(12), 978; doi:10.3390/ma9120978
Received: 28 October 2016 / Revised: 20 November 2016 / Accepted: 29 November 2016 / Published: 2 December 2016
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Abstract
Water-repellent soils have a potential as alternative construction materials that will improve conventional geotechnical structures. In this study, the potential of chemically treated water-repellent kaolin clay as a landfill cover material is explored by examining its characteristics including hydraulic and mechanical properties. In
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Water-repellent soils have a potential as alternative construction materials that will improve conventional geotechnical structures. In this study, the potential of chemically treated water-repellent kaolin clay as a landfill cover material is explored by examining its characteristics including hydraulic and mechanical properties. In order to provide water repellency to the kaolin clay, the surface of clay particle is modified with organosilanes in concentrations (CO) ranging from 0.5% to 10% by weight. As the CO increases, the specific gravity of treated clay tends to decrease, whereas the total organic carbon content of the treated clay tends to increase. The soil-water contact angle increases with an increase in CO until CO = 2.5%, and then maintains an almost constant value (≈134.0°). Resistance to water infiltration is improved by organosilane treatment under low hydrostatic pressure. However, water infiltration resistance under high hydrostatic pressure is reduced or exacerbated to the level of untreated clay. The maximum compacted dry weight density decreases with increasing CO. As the CO increases, the small strain shear modulus increases, whereas the effect of organosilane treatment on the constrained modulus is minimal. The results indicate that water-repellent kaolin clay possesses excellent engineering characteristics for a landfill cover material. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Conversion of Biowaste Asian Hard Clam (Meretrix lusoria) Shells into White-Emitting Phosphors for Use in Neutral White LEDs
Materials 2016, 9(12), 979; doi:10.3390/ma9120979
Received: 29 September 2016 / Revised: 23 November 2016 / Accepted: 29 November 2016 / Published: 2 December 2016
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Abstract
The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell
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The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell waste was first transformed into pure and well-crystallized single-phase white light-emitting phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials. The phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials were synthesized by the solid-state reaction method and the carbothermic reduction process, and then characterized and analyzed by means of X-ray diffraction (XRD) and photoluminescence (PL) measurements. The structural and luminescent properties of the phosphors were investigated as well. The PL and quantum efficiency measurements showed that the luminescence properties of clam shell-based phosphors were comparable to that of the chemically derived phosphors. Moreover, white light-emitting diodes were fabricated through the integration of 380 nm chips and single-phase white light-emitting phosphors (Ca0.979Eu0.006Mn0.015)9Gd(PO4)7 into a single package of a white light emitting diode (WLED) emitting a neutral white light of 5298 K with color coordinates of (0.337, 0.344). Full article
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Open AccessArticle Photoresponsive Polymeric Reversible Nanoparticles via Self-Assembly of Reactive ABA Triblock Copolymers and Their Transformation to Permanent Nanostructures
Materials 2016, 9(12), 980; doi:10.3390/ma9120980
Received: 8 October 2016 / Revised: 29 November 2016 / Accepted: 29 November 2016 / Published: 2 December 2016
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Abstract
Azobenzene-functionalized ABA triblock copolymers with controlled molecular weights are prepared first via a sequential ring-opening metathesis polymerization and acyclic diene metathesis polymerization in one-pot, which are readily converted, by a facile esterification, to the modified ABA triblock copolymers. Then, these reactive triblock copolymers
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Azobenzene-functionalized ABA triblock copolymers with controlled molecular weights are prepared first via a sequential ring-opening metathesis polymerization and acyclic diene metathesis polymerization in one-pot, which are readily converted, by a facile esterification, to the modified ABA triblock copolymers. Then, these reactive triblock copolymers can spontaneously self-assemble in a selective solvent to form reproducible and reversible polymeric core-shell nanoparticles. Finally, the stable and permanent shell-crosslinked nanoparticles are obtained by an intramolecular crosslinking reaction in dilute solution under UV light irradiation. These as-prepared polymeric nanoparticles and their precursor incorporating azobenzene chromophores exhibit distinct photoresponsive performance and morphological variation. Full article
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Open AccessArticle A General Accelerated Degradation Model Based on the Wiener Process
Materials 2016, 9(12), 981; doi:10.3390/ma9120981
Received: 26 September 2016 / Revised: 27 November 2016 / Accepted: 30 November 2016 / Published: 6 December 2016
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Abstract
Accelerated degradation testing (ADT) is an efficient tool to conduct material service reliability and safety evaluations by analyzing performance degradation data. Traditional stochastic process models are mainly for linear or linearization degradation paths. However, those methods are not applicable for the situations where
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Accelerated degradation testing (ADT) is an efficient tool to conduct material service reliability and safety evaluations by analyzing performance degradation data. Traditional stochastic process models are mainly for linear or linearization degradation paths. However, those methods are not applicable for the situations where the degradation processes cannot be linearized. Hence, in this paper, a general ADT model based on the Wiener process is proposed to solve the problem for accelerated degradation data analysis. The general model can consider the unit-to-unit variation and temporal variation of the degradation process, and is suitable for both linear and nonlinear ADT analyses with single or multiple acceleration variables. The statistical inference is given to estimate the unknown parameters in both constant stress and step stress ADT. The simulation example and two real applications demonstrate that the proposed method can yield reliable lifetime evaluation results compared with the existing linear and time-scale transformation Wiener processes in both linear and nonlinear ADT analyses. Full article
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Open AccessArticle An Analytical Calculation of Frictional and Bending Moments at the Head-Neck Interface of Hip Joint Implants during Different Physiological Activities
Materials 2016, 9(12), 982; doi:10.3390/ma9120982
Received: 10 November 2016 / Revised: 30 November 2016 / Accepted: 1 December 2016 / Published: 5 December 2016
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Abstract
This study predicts the frictional moments at the head-cup interface and frictional torques and bending moments acting on the head-neck interface of a modular total hip replacement across a range of activities of daily living. The predicted moment and torque profiles are based
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This study predicts the frictional moments at the head-cup interface and frictional torques and bending moments acting on the head-neck interface of a modular total hip replacement across a range of activities of daily living. The predicted moment and torque profiles are based on the kinematics of four patients and the implant characteristics of a metal-on-metal implant. Depending on the body weight and type of activity, the moments and torques had significant variations in both magnitude and direction over the activity cycles. For the nine investigated activities, the maximum magnitude of the frictional moment ranged from 2.6 to 7.1 Nm. The maximum magnitude of the torque acting on the head-neck interface ranged from 2.3 to 5.7 Nm. The bending moment acting on the head-neck interface varied from 7 to 21.6 Nm. One-leg-standing had the widest range of frictional torque on the head-neck interface (11 Nm) while normal walking had the smallest range (6.1 Nm). The widest range, together with the maximum magnitude of torque, bending moment, and frictional moment, occurred during one-leg-standing of the lightest patient. Most of the simulated activities resulted in frictional torques that were near the previously reported oxide layer depassivation threshold torque. The predicted bending moments were also found at a level believed to contribute to the oxide layer depassivation. The calculated magnitudes and directions of the moments, applied directly to the head-neck taper junction, provide realistic mechanical loading data for in vitro and computational studies on the mechanical behaviour and multi-axial fretting at the head-neck interface. Full article
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Open AccessArticle Vacuum-Induced Surface Freezing to Produce Monoliths of Aligned Porous Alumina
Materials 2016, 9(12), 983; doi:10.3390/ma9120983
Received: 15 October 2016 / Revised: 28 November 2016 / Accepted: 30 November 2016 / Published: 5 December 2016
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Abstract
Vacuum-induced surface freezing has been used to produce uni-directional freezing of colloidal aluminum oxide dispersions. It leads to zones of different structure within the resulting sintered monoliths that are highly similar to those known for freeze casting using a cryogen cold source. A
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Vacuum-induced surface freezing has been used to produce uni-directional freezing of colloidal aluminum oxide dispersions. It leads to zones of different structure within the resulting sintered monoliths that are highly similar to those known for freeze casting using a cryogen cold source. A more-or-less dense surface layer and a cellular sub-surface region are formed, beneath which is a middle region of aligned lamellae and pores that stretches through most of the depth of the monolith. This is the case even at a volume fraction of dispersed phase as low as 0.032. A more-dense but still porous base layer is formed by accumulation of rejected nanoparticles preceding the freezing front and differs from previous reports in that no ice lenses are observed. X-ray micro-computed tomography reveals a uniform aligned pore structure vertically through the monolith. The pores close to the periphery are oriented radially or as chords, while the center region contains domains of parallel pores/lamellae. The domains are randomly oriented to one another, as already reported for regular freeze casting. This technique for directional freezing is convenient and easy to perform, but requires further refinement in that the temperature gradient and freezing rates remain yet to be measured. Also, control of the temperature gradient by varying chamber vacuum and shelf temperature needs to be evaluated. Full article
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Open AccessArticle Fretting Fatigue Experiment and Analysis of AlSi9Cu2Mg Alloy
Materials 2016, 9(12), 984; doi:10.3390/ma9120984
Received: 29 September 2016 / Revised: 15 November 2016 / Accepted: 23 November 2016 / Published: 5 December 2016
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Abstract
An investigation was carried out in order to study the fretting fatigue behavior of an AlSi9Cu2Mg aluminum alloy. The fretting fatigue tests of AlSi9Cu2Mg were performed using a specially designed testing machine. The failure mechanism of fretting fatigue was explored by studying the
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An investigation was carried out in order to study the fretting fatigue behavior of an AlSi9Cu2Mg aluminum alloy. The fretting fatigue tests of AlSi9Cu2Mg were performed using a specially designed testing machine. The failure mechanism of fretting fatigue was explored by studying the fracture surfaces, fretting scars, fretting debris, and micro-hardness of fretting fatigue specimens using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and micro Vickers hardness test techniques. The experimental results show that the fretting fatigue limit (42 MPa) is significantly reduced to approximately 47% of the plain fatigue limit (89 MPa) under 62.5 MPa contact pressure. Furthermore, the fretting fatigue life decreases with increasing alternating stress and increasing contact pressure. The examination results suggest that the stress concentrates induced by oxidation-assisted wear on the contact interface led to the earlier initiation and propagation of crack under the fretting condition. Full article
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Open AccessArticle Strontium-Substituted Bioceramics Particles: A New Way to Modulate MCP-1 and Gro-α Production by Human Primary Osteoblastic Cells
Materials 2016, 9(12), 985; doi:10.3390/ma9120985
Received: 29 September 2016 / Revised: 8 November 2016 / Accepted: 25 November 2016 / Published: 5 December 2016
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Abstract
Background: To avoid morbidity and limited availability associated with autografts, synthetic calcium phosphate (CaP) ceramics were extensively developed and used as bone filling materials. Controlling their induced-inflammatory response nevertheless remained a major concern. Strontium-containing CaP ceramics were recently demonstrated for impacting cytokines’ secretion
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Background: To avoid morbidity and limited availability associated with autografts, synthetic calcium phosphate (CaP) ceramics were extensively developed and used as bone filling materials. Controlling their induced-inflammatory response nevertheless remained a major concern. Strontium-containing CaP ceramics were recently demonstrated for impacting cytokines’ secretion pattern of human primary monocytes. The present study focuses on the ability of strontium-containing CaP to control the human primary bone cell production of two major inflammatory and pro-osteoclastogenic mediators, namely MCP-1 and Gro-α, in response to ceramics particles. Methods: This in vitro study was performed using human primary osteoblasts in which their response to ceramics was evaluated by PCR arrays, antibody arrays were used for screening and real-time PCR and ELISA for more focused analyses. Results: Study of mRNA and protein expression highlights that human primary bone cells are able to produce these inflammatory mediators and reveal that the adjunction of CaP in the culture medium leads to their enhanced production. Importantly, the current work determines the down-regulating effect of strontium-substituted CaP on MCP-1 and Gro-α production. Conclusion: Our findings point out a new capability of strontium to modulate human primary bone cells’ communication with the immune system. Full article
(This article belongs to the Special Issue Calcium Phosphate in Biomedical Applications)
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Open AccessArticle Microstructure and Tribological Properties of Mo–40Ni–13Si Multiphase Intermetallic Alloy
Materials 2016, 9(12), 986; doi:10.3390/ma9120986
Received: 19 October 2016 / Revised: 16 November 2016 / Accepted: 29 November 2016 / Published: 6 December 2016
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Abstract
Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo–40Ni–13Si (at %).
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Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo–40Ni–13Si (at %). Microstructure characterization reveals that a certain amount of ductile Mo phases formed during the solidification process of a ternary Mo–Ni–Si molten alloy, which is beneficial to the improvement of ductility of intermetallic alloys. Tribological properties of the designed alloy—including wear resistance, friction coefficient, and metallic tribological compatibility—were evaluated under dry sliding wear test conditions at room temperature. Results suggest that the multiphase alloy possesses an excellent tribological property, which is attributed to unique microstructural features and thereby a good combination in hardness and ductility. The corresponding wear mechanism is explained by observing the worn surface, subsurface, and wear debris of the alloy, which was found to be soft abrasive wear. Full article
(This article belongs to the Special Issue Tribological Behavior of Materials by Surface Engineering)
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Open AccessArticle Optoelectronic Properties and the Electrical Stability of Ga-Doped ZnO Thin Films Prepared via Radio Frequency Sputtering
Materials 2016, 9(12), 987; doi:10.3390/ma9120987
Received: 26 October 2016 / Revised: 22 November 2016 / Accepted: 29 November 2016 / Published: 6 December 2016
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Abstract
In this work, Ga-doped ZnO (GZO) thin films were deposited via radio frequency sputtering at room temperature. The influence of the Ga content on the film’s optoelectronic properties as well as the film’s electrical stability were investigated. The results showed that the film’s
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In this work, Ga-doped ZnO (GZO) thin films were deposited via radio frequency sputtering at room temperature. The influence of the Ga content on the film’s optoelectronic properties as well as the film’s electrical stability were investigated. The results showed that the film’s crystallinity degraded with increasing Ga content. The film’s conductivity was first enhanced due to the replacement of Zn2+ by Ga3+ before decreasing due to the separation of neutralized gallium atoms from the ZnO lattice. When the Ga content increased to 15.52 at %, the film’s conductivity improved again. Furthermore, all films presented an average transmittance exceeding 80% in the visible region. Regarding the film’s electrical stability, GZO thermally treated below 200 °C exhibited no significant deterioration in electrical properties, but such treatment over 200 °C greatly reduced the film’s conductivity. In normal atmospheric conditions, the conductivity of GZO films remained very stable at ambient temperature for more than 240 days. Full article
(This article belongs to the Special Issue Advances in Transparent Conducting Materials)
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Open AccessArticle The Preparation of Modified Industrial Waste Polyacrylonitrile for the Adsorptive Recovery of Pt(IV) from Acidic Solutions
Materials 2016, 9(12), 988; doi:10.3390/ma9120988
Received: 4 November 2016 / Revised: 23 November 2016 / Accepted: 1 December 2016 / Published: 6 December 2016
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Abstract
Sorption technique is one of the most effective methods for recovering precious metals from wastewater solutions; however, its main drawbacks of the traditional sorbents are the slow kinetics and relatively low sorption capacities. As a solution, thin sorbent fibers have been highlighted because
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Sorption technique is one of the most effective methods for recovering precious metals from wastewater solutions; however, its main drawbacks of the traditional sorbents are the slow kinetics and relatively low sorption capacities. As a solution, thin sorbent fibers have been highlighted because they can lead to fast adsorption kinetics due to their high surface areas and numerous binding sites. In this sense, the applicability of an industrial waste polyacrylonitrile (PAN) textile was examined to recover Pt(IV) from acid solutions. In order to enrich cationic functional groups on the surface of a PAN textile, the textile was chemically modified via polyethylenmine (PEI) coating. Afterwards, using PEI-coated PAN fiber, batch sorption experiments (isotherms and kinetics) and column experiments were conducted to evaluate its sorption performance toward Pt(IV). It was clearly revealed in column experiments that the PEI-coated waste PAN textile (WPAN) has fast kinetics and good performance for Pt(IV) recovery. Full article
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Open AccessArticle Electroconductive Composites from Polystyrene Block Copolymers and Cu–Alumina Filler
Materials 2016, 9(12), 989; doi:10.3390/ma9120989
Received: 20 October 2016 / Revised: 23 November 2016 / Accepted: 1 December 2016 / Published: 7 December 2016
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Abstract
Technological advancements and development of new materials may lead to the manufacture of sustainable energy-conducting devices used in the energy sector. This research attempts to fabricate novel electroconductive and mechanically stable nanocomposites via an electroless deposition (ELD) technique using electrically insulating materials. Metallic
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Technological advancements and development of new materials may lead to the manufacture of sustainable energy-conducting devices used in the energy sector. This research attempts to fabricate novel electroconductive and mechanically stable nanocomposites via an electroless deposition (ELD) technique using electrically insulating materials. Metallic Cu is coated onto Al2O3 by ELD, and the prepared filler is then integrated (2–14 wt %) into a matrix of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleic anhydride (PS-b-(PE-r-B)-b-PS-g-MA). Considerable variations in composite phases with filler inclusion exist. The Cu crystallite growth onto Al2O3 was evaluated by X-ray diffraction (XRD) analysis and energy dispersive spectrometry (EDS). Scanning electron microscopy (SEM) depicts a uniform Cu coating on Al2O3, while homogeneous filler dispersion is exhibited in the case of composites. The electrical behavior of composites is enhanced drastically (7.7 × 10−5 S/cm) upon incorporation of Cu–Al2O3 into an insulating polymer matrix (4.4 × 10−16 S/cm). Moreover, mechanical (Young’s modulus, tensile strength and % elongation at break) and thermal (thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC)) properties of the nanocomposites also improve substantially. These composites are likely to meet the demands of modern high-strength electroconductive devices. Full article
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Open AccessArticle Luminescence Properties and Mechanisms of CuI Thin Films Fabricated by Vapor Iodization of Copper Films
Materials 2016, 9(12), 990; doi:10.3390/ma9120990
Received: 15 September 2016 / Revised: 2 November 2016 / Accepted: 22 November 2016 / Published: 7 December 2016
Cited by 2 | PDF Full-text (3173 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Copper iodide (CuI) thin films were grown on Si(100) substrates using a copper film iodination reaction method. It was found that γ-CuI films have a uniform and dense microstructure with (111)-orientation. Transmission spectra indicated that CuI thin films have an average transmittance of
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Copper iodide (CuI) thin films were grown on Si(100) substrates using a copper film iodination reaction method. It was found that γ-CuI films have a uniform and dense microstructure with (111)-orientation. Transmission spectra indicated that CuI thin films have an average transmittance of about 60% in the visible range and the optical band gap is 3.01 eV. By checking the effect of the thickness of the Cu films and annealing condition on the photoluminescence (PL) character of CuI films, the luminescence mechanisms of CuI have been comprehensively analyzed, and the origin of different PL emissions are proposed with Cu vacancy and iodine vacancy as defect levels. Full article
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Open AccessArticle Enhancing the Hydrophilicity and Cell Attachment of 3D Printed PCL/Graphene Scaffolds for Bone Tissue Engineering
Materials 2016, 9(12), 992; doi:10.3390/ma9120992
Received: 30 September 2016 / Revised: 24 November 2016 / Accepted: 25 November 2016 / Published: 7 December 2016
Cited by 2 | PDF Full-text (8714 KB) | HTML Full-text | XML Full-text
Abstract
Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements, i.e., certain standards in terms of mechanical properties, surface characteristics, porosity, degradability, and biocompatibility. The optimal design
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Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements, i.e., certain standards in terms of mechanical properties, surface characteristics, porosity, degradability, and biocompatibility. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes, as well as surface treatment. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion-based additive manufacturing system to produce poly(ε-caprolactone) (PCL)/pristine graphene scaffolds for bone tissue applications and the influence of chemical surface modification on their biological behaviour. Scaffolds with the same architecture but different concentrations of pristine graphene were evaluated from surface property and biological points of view. Results show that the addition of pristine graphene had a positive impact on cell viability and proliferation, and that surface modification leads to improved cell response. Full article
(This article belongs to the Special Issue 3D Printing for Biomedical Engineering)
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Open AccessArticle An Evaluation of a Borided Layer Formed on Ti-6Al-4V Alloy by Means of SMAT and Low-Temperature Boriding
Materials 2016, 9(12), 993; doi:10.3390/ma9120993
Received: 6 October 2016 / Revised: 23 November 2016 / Accepted: 25 November 2016 / Published: 8 December 2016
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Abstract
In this paper, a nanocrystalline surface layer without impurities was fabricated on Ti-6Al-4V alloy by means of surface mechanical attrition treatment (SMAT). The grain size in the nanocrystalline layer is about 10 nm and grain morphology displays a random crystallographic orientation distribution. Subsequently,
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In this paper, a nanocrystalline surface layer without impurities was fabricated on Ti-6Al-4V alloy by means of surface mechanical attrition treatment (SMAT). The grain size in the nanocrystalline layer is about 10 nm and grain morphology displays a random crystallographic orientation distribution. Subsequently, the low-temperature boriding behaviors (at 600 °C) of the SMAT sample, including the phase composition, microstructure, micro-hardness, and brittleness, were investigated in comparison with those of coarse-grained sample borided at 1100 °C. The results showed that the boriding kinetics could be significantly enhanced by SMAT, resulting in the formation of a nano-structured boride layers on Ti-6Al-4V alloy at lower temperature. Compared to the coarse-grained boriding sample, the SMAT boriding sample exhibits a similar hardness value, but improved surface toughness. The satisfactory surface toughness may be attributed to the boriding treatment that was carried out at lower temperature. Full article
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Open AccessArticle Pore-Structure-Optimized CNT-Carbon Nanofibers from Starch for Rechargeable Lithium Batteries
Materials 2016, 9(12), 995; doi:10.3390/ma9120995
Received: 29 July 2016 / Revised: 21 November 2016 / Accepted: 23 November 2016 / Published: 8 December 2016
Cited by 2 | PDF Full-text (6072 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Porous carbon materials are used for many electrochemical applications due to their outstanding properties. However, research on controlling the pore structure and analyzing the carbon structures is still necessary to achieve enhanced electrochemical properties. In this study, mesoporous carbon nanotube (CNT)-carbon nanofiber electrodes
[...] Read more.
Porous carbon materials are used for many electrochemical applications due to their outstanding properties. However, research on controlling the pore structure and analyzing the carbon structures is still necessary to achieve enhanced electrochemical properties. In this study, mesoporous carbon nanotube (CNT)-carbon nanofiber electrodes were developed by heat-treatment of electrospun starch with carbon nanotubes, and then applied as a binder-free electrochemical electrode for a lithium-ion battery. Using the unique lamellar structure of starch, mesoporous CNT-carbon nanofibers were prepared and their pore structures were controlled by manipulating the heat-treatment conditions. The activation process greatly increased the volume of micropores and mesopores of carbon nanofibers by etching carbons with CO2 gas, and the Brunauer-Emmett-Teller (BET) specific area increased to about 982.4 m2·g−1. The activated CNT-carbon nanofibers exhibited a high specific capacity (743 mAh·g−1) and good cycle performance (510 mAh·g−1 after 30 cycles) due to their larger specific surface area. This condition presents many adsorption sites of lithium ions, and higher electrical conductivity, compared with carbon nanofibers without CNT. The research suggests that by controlling the heat-treatment conditions and activation process, the pore structure of the carbon nanofibers made from starch could be tuned to provide the conditions needed for various applications. Full article
(This article belongs to the Special Issue Materials for Electrochemical Capacitors and Batteries)
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Open AccessArticle Enhanced Photovoltaic Properties of Bulk Heterojunction Organic Photovoltaic Devices by an Addition of a Low Band Gap Conjugated Polymer
Materials 2016, 9(12), 996; doi:10.3390/ma9120996
Received: 7 November 2016 / Revised: 2 December 2016 / Accepted: 2 December 2016 / Published: 8 December 2016
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Abstract
In this study, we fabricated organic photovoltaics (OPVs) by introducing the polymer additive HTh6BT into the photoactive layer of a poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) system. The HTh6BT had a relatively low band gap energy of 1.65 eV and a molecular
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In this study, we fabricated organic photovoltaics (OPVs) by introducing the polymer additive HTh6BT into the photoactive layer of a poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) system. The HTh6BT had a relatively low band gap energy of 1.65 eV and a molecular and crystalline structure similar to that of P3HT. In the photoactive layer, the HTh6BT and P3HT can both act as donors. In such parallel-type bulk heterojunctions, each donor can form excitons and generate charges while being separated from the donor/acceptor interface. Changes in the photovoltaic property of the OPV device by the addition of HTh6BT were evaluated, and the optical characteristics of the photoactive layer, as well as the surface morphology, polymer ordering, and crystallinity of the P3HT:PCBM film were analyzed. Compared to a device without HTh6BT, all short-circuit current densities, open-circuit voltages, and fill factors were enhanced, leading to the enhancement of the power conversion efficiency by 36%. Full article
(This article belongs to the Section Materials for Energy Applications)
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Open AccessArticle Synthesis of Fluorescent Core-Shell Metal Nanohybrids: A Versatile Approach
Materials 2016, 9(12), 997; doi:10.3390/ma9120997
Received: 15 July 2016 / Revised: 15 November 2016 / Accepted: 5 December 2016 / Published: 9 December 2016
Cited by 2 | PDF Full-text (2268 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A flexible way of fabricating core-shell noble metal-organic nanohybrids with tailored chemical and spectroscopic properties is proposed here. The synthetic protocol consists of a multi-step procedure able to guarantee acceptable reproducibility of core size and shape as well as control of the organic
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A flexible way of fabricating core-shell noble metal-organic nanohybrids with tailored chemical and spectroscopic properties is proposed here. The synthetic protocol consists of a multi-step procedure able to guarantee acceptable reproducibility of core size and shape as well as control of the organic outer layer. The proposed method highlights limitations in obtaining highly controllable products, although the heterogeneity degree of the nanostructures is in line with that expected from bottom-up approaches in solution. Selective functionalization of the nanohybrids with properly-substituted fluorescent dyes under variable experimental conditions allowed the preparation of composite systems of tunable spectroscopic properties to be employed as nanoprobes in sensing or photonic applications. To this end, preliminary investigation on embedding the nanohybrids in compatible polymeric matrices is also reported. Full article
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Open AccessArticle The Non-Steady State Growth of Pearlite outside the Hultgren Extrapolation
Materials 2016, 9(12), 998; doi:10.3390/ma9120998
Received: 30 September 2016 / Revised: 24 November 2016 / Accepted: 29 November 2016 / Published: 14 December 2016
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Abstract
The goal of this paper is to analyse the effect of adding Al on the non-steady pearlite growth occurring in a Fe–C–Mn system. The results are discussed in terms of the partitioning of elements across the austenite/ferrite and austenite/cementite interfaces, and the modification
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The goal of this paper is to analyse the effect of adding Al on the non-steady pearlite growth occurring in a Fe–C–Mn system. The results are discussed in terms of the partitioning of elements across the austenite/ferrite and austenite/cementite interfaces, and the modification of the pearlite driving force related to the change in carbon activity in austenite. Full article
(This article belongs to the Special Issue Thermal Sciences and Thermodynamics of Materials)
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Open AccessArticle New Elastomeric Materials Based on Natural Rubber Obtained by Electron Beam Irradiation for Food and Pharmaceutical Use
Materials 2016, 9(12), 999; doi:10.3390/ma9120999
Received: 22 September 2016 / Revised: 16 November 2016 / Accepted: 25 November 2016 / Published: 21 December 2016
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Abstract
The efficiency of polyfunctional monomers as cross-linking co-agents on the chemical properties of natural rubber vulcanized by electron beam irradiation was studied. The following polyfunctional monomers were used: trimethylolpropane-trimethacrylate, zinc-diacrylate, ethylene glycol dimethacrylate, triallylcyanurate and triallylisocyanurate. The electron beam treatment was done using
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The efficiency of polyfunctional monomers as cross-linking co-agents on the chemical properties of natural rubber vulcanized by electron beam irradiation was studied. The following polyfunctional monomers were used: trimethylolpropane-trimethacrylate, zinc-diacrylate, ethylene glycol dimethacrylate, triallylcyanurate and triallylisocyanurate. The electron beam treatment was done using irradiation doses in the range of 75 kGy–300 kGy. The gel fraction, crosslink density and effects of different aqueous solutions, by absorption tests, have been investigated as a function of polyfunctional monomers type and absorbed dose. The samples gel fraction and crosslink density were determined on the basis of equilibrium solvent-swelling measurements by applying the modified Flory–Rehner equation for tetra functional networks. The absorption tests were done in accordance with the SR ISI 1817:2015 using distilled water, acetic acid (10%), sodium hydroxide (1%), ethylic alcohol (96%), physiological serum (sodium chloride 0.9%) and glucose (glucose monohydrate 10%). The samples structure and morphology were investigated by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy techniques. Full article
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Open AccessArticle Effects of Perforation on Rigid PU Foam Plates: Acoustic and Mechanical Properties
Materials 2016, 9(12), 1000; doi:10.3390/ma9121000
Received: 10 September 2016 / Revised: 28 November 2016 / Accepted: 2 December 2016 / Published: 9 December 2016
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Abstract
Factories today are equipped with diverse mechanical equipment in response to rapid technological and industrial developments. Industrial areas located near residential neighborhoods cause massive environmental problems. In particular, noise pollution results in physical and psychological discomfort, and is a seen as invisible and
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Factories today are equipped with diverse mechanical equipment in response to rapid technological and industrial developments. Industrial areas located near residential neighborhoods cause massive environmental problems. In particular, noise pollution results in physical and psychological discomfort, and is a seen as invisible and inevitable problem. Thus, noise reduction is a critical and urgent matter. In this study, rigid polyurethane (PU) foam plates undergo perforation using a tapping machine. The mechanical and acoustic properties of these perforated plates as related to perforation rate and perforation depth are evaluated in terms of compression strength, drop-weight impact strength, and sound absorption coefficient. Experimental results indicate that applying the perforation process endows the rigid PU foaming plates with greater load absorption and better sound absorption at medium and high frequencies. Full article
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Open AccessArticle The Refining Mechanism of Super Gravity on the Solidification Structure of Al-Cu Alloys
Materials 2016, 9(12), 1001; doi:10.3390/ma9121001
Received: 15 October 2016 / Revised: 26 November 2016 / Accepted: 30 November 2016 / Published: 10 December 2016
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Abstract
There is far less study of the refining effect of super gravity fields on solidification structures of metals than of the effects of electrical currents, magnetic and ultrasonic fields. Moreover, the refining mechanisms of super gravity are far from clear. This study applied
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There is far less study of the refining effect of super gravity fields on solidification structures of metals than of the effects of electrical currents, magnetic and ultrasonic fields. Moreover, the refining mechanisms of super gravity are far from clear. This study applied a super gravity field to Al-Cu alloys to investigate its effect on refining their structures and the mechanism of interaction. The experimental results showed that the solidification structure of Al-Cu alloys can be greatly refined by a super gravity field. The major refining effect was mainly achieved when super gravity was applied at the initial solidification stage; only slight refinement could be obtained towards the end of solidification. No refinement was obtained by the super gravity treatment on pure liquid or solid stages. The effectiveness of super gravity results from its promoting the multiplication of crystal nuclei, which we call “Heavy Crystal Rain”, thereby greatly strengthening the migration of crystal nuclei within the alloy. Increasing the solute Cu content can increase nucleation density and restrict the growth of crystals, which further increases the refining effect of super gravity. Within this paper, we also discuss the motile behavior of crystals in a field of super gravity. Full article
(This article belongs to the Special Issue Welding, Joining and Casting of Advanced Materials)
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Open AccessFeature PaperArticle Cellulose Nanocrystal Membranes as Excipients for Drug Delivery Systems
Materials 2016, 9(12), 1002; doi:10.3390/ma9121002
Received: 30 October 2016 / Revised: 18 November 2016 / Accepted: 2 December 2016 / Published: 12 December 2016
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Abstract
In this work, cellulose nanocrystals (CNCs) were obtained from flax fibers by an acid hydrolysis assisted by sonochemistry in order to reduce reaction times. The cavitation inducted during hydrolysis resulted in CNC with uniform shapes, and thus further pretreatments into the cellulose are
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In this work, cellulose nanocrystals (CNCs) were obtained from flax fibers by an acid hydrolysis assisted by sonochemistry in order to reduce reaction times. The cavitation inducted during hydrolysis resulted in CNC with uniform shapes, and thus further pretreatments into the cellulose are not required. The obtained CNC exhibited a homogeneous morphology and high crystallinity, as well as typical values for surface charge. Additionally, CNC membranes were developed from CNC solution to evaluation as a drug delivery system by the incorporation of a model drug. The drug delivery studies were carried out using chlorhexidine (CHX) as a drug and the antimicrobial efficiency of the CNC membrane loaded with CHX was examined against Gram-positive bacteria Staphylococcus aureus (S. Aureus). The release of CHX from the CNC membranes is determined by UV-Vis. The obtaining methodology of the membranes proved to be simple, and these early studies showed a potential use in antibiotic drug delivery systems due to the release kinetics and the satisfactory antimicrobial activity. Full article
(This article belongs to the Special Issue Nanocellulose-Based Functional Materials)
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Open AccessArticle Synthesis and Drug Delivery Application of Thermo- and pH-Sensitive Hydrogels: Poly(β-CD-co-N-Isopropylacrylamide-co-IAM)
Materials 2016, 9(12), 1003; doi:10.3390/ma9121003
Received: 8 October 2016 / Revised: 7 December 2016 / Accepted: 8 December 2016 / Published: 11 December 2016
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Abstract
Copolymerization of N-isopropylacrylamide (NIPAM), itaconamic acid (IAM; 4-amino-2-methylene-4-oxobutanoic acid) and β-cyclodextrin was investigated in this study. β-cyclodextrin was at first modified by reacting with allyl glycidyl ether to substitute its OH end groups with moieties containing double bonds to facilitate the subsequent
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Copolymerization of N-isopropylacrylamide (NIPAM), itaconamic acid (IAM; 4-amino-2-methylene-4-oxobutanoic acid) and β-cyclodextrin was investigated in this study. β-cyclodextrin was at first modified by reacting with allyl glycidyl ether to substitute its OH end groups with moieties containing double bonds to facilitate the subsequent radical copolymerization with NIPAM and IAM. It was reported that poly(NIPAM-IAM) can respond to the change of temperature as well as pH value. In this study, the structure of β-cyclodextrin was introduced to poly(NIPAM-IAM) copolymers because of its cavity structure capable of encapsulating a variety of drug molecules. The tri-component copolymers, poly(CD-NIPAM-IAM), were synthesized with different monomeric ratios of NIPAM/IAM/β-CD and the hydrogels of the tri-component copolymers were also synthesized by additionally adding N,N′-methylenebisacrylamide as a cross-linking agent. The results show that the lower critical solution temperature (LCST) of the copolymer (or hydrogel) increases as the molar fraction of IAM increases. The transmission electron microscopic (TEM) images of linear copolymers (no cross-linking) show that molecules undergo self-assembly to have a distinct core–shell structure, compared to poly(CD-NIPAM) which contains no IAM. On the other hand, the scanning electron microscopic (SEM) images of hydrogels show that the pores gradually become sheet-like structures as the molar fraction of IAM increases to enhance the water absorption capacity. In order to exhibit the thermal and pH sensitivities of poly(CD-NIPAM-IAM) as the drug carrier, the drug release of the newly synthesized hydrogels at 37 °C and different pH values, pH = 2 and pH = 7.4, was investigated using atorvastatin which was used primarily as a lipid-lowering drug. The drug release experimental result shows that poly(CD-NIPAM-IAM) as a drug carrier was pH-sensitive and has the largest release rate at pH = 7.4 at 37 °C, indicating it is useful to release drugs in a neutral or alkaline (intestinal) environment. Full article
(This article belongs to the Special Issue Smart Biomaterials and Biointerfaces)
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Open AccessArticle Spark Plasma Sintering of a Gas Atomized Al7075 Alloy: Microstructure and Properties
Materials 2016, 9(12), 1004; doi:10.3390/ma9121004
Received: 18 October 2016 / Revised: 23 November 2016 / Accepted: 30 November 2016 / Published: 12 December 2016
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Abstract
The powder of an Al7075 alloy was prepared by gas atomization. A combination of cellular, columnar, and equiaxed dendritic-like morphology was observed in individual powder particles with continuous layers of intermetallic phases along boundaries. The cells are separated predominantly by high-angle boundaries, the
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The powder of an Al7075 alloy was prepared by gas atomization. A combination of cellular, columnar, and equiaxed dendritic-like morphology was observed in individual powder particles with continuous layers of intermetallic phases along boundaries. The cells are separated predominantly by high-angle boundaries, the areas with dendritic-like morphology usually have a similar crystallographic orientation. Spark plasma sintering resulted in a fully dense material with a microstructure similar to that of the powder material. The continuous layers of intermetallic phases are replaced by individual particles located along internal boundaries, coarse particles are formed at the surface of original powder particles. Microhardness measurements revealed both artificial and natural ageing behavior similar to that observed in ingot metallurgy material. The minimum microhardness of 81 HV, observed in the sample annealed at 300 °C, reflects the presence of coarse particles. The peak microhardness of 160 HV was observed in the sample annealed at 500 °C and then aged at room temperature. Compression tests confirmed high strength combined with sufficient plasticity. Annealing even at 500 °C does not significantly influence the distribution of grain sizes—about 45% of the area is occupied by grains with the size below 10 µm. Full article
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Open AccessArticle Floating Hydrogel with Self-Generating Micro-Bubbles for Intravesical Instillation
Materials 2016, 9(12), 1005; doi:10.3390/ma9121005
Received: 7 November 2016 / Revised: 26 November 2016 / Accepted: 5 December 2016 / Published: 12 December 2016
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Abstract
Intravesical instillation is the main therapy for bladder cancer and interstitial cystitis. However, most drug solutions are eliminated from bladder after the first voiding of urine. To solve this problem, we proposed a floating hydrogel with self-generating micro-bubbles as a new delivery system.
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Intravesical instillation is the main therapy for bladder cancer and interstitial cystitis. However, most drug solutions are eliminated from bladder after the first voiding of urine. To solve this problem, we proposed a floating hydrogel with self-generating micro-bubbles as a new delivery system. It floated in urine, avoiding the urinary obstruction and bladder irritation that ordinary hydrogels caused. In this study, we abandoned traditional gas-producing method like chemical decomposition of NaHCO3, and used the foamability of Poloxamer 407 (P407) instead. Through simple shaking (just like shaking SonoVue for contrast-enhanced ultrasound in clinical), the P407 solution will “lock” many micro-bubbles and float in urine as quickly and steadily as other gas producing materials. In vivo release experiments showed that drug was released continually from hydrogel for 10 h during the erosion process. Thus, the residence time of drug in bladder was prolonged and drug efficacy was improved. In vivo efficacy study using rabbit acute bladder injury model showed that prolonged drug residence time in bladder increased the efficiency of heparin in the protection of bladder mucosal permeability. Therefore, our floating hydrogel system with self-generating micro-bubbles was single-component, simply prepared and efficacy enhancing, successfully exempting users from worries on safety and clinical efficiency from bench to bedside. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Fabrication of Fe-Based Diamond Composites by Pressureless Infiltration
Materials 2016, 9(12), 1006; doi:10.3390/ma9121006
Received: 18 September 2016 / Revised: 6 November 2016 / Accepted: 29 November 2016 / Published: 12 December 2016
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Abstract
A metal-based matrix is usually used for the fabrication of diamond bits in order to achieve favorable properties and easy processing. In the effort to reduce the cost and to attain the desired bit properties, researchers have brought more attention to diamond composites.
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A metal-based matrix is usually used for the fabrication of diamond bits in order to achieve favorable properties and easy processing. In the effort to reduce the cost and to attain the desired bit properties, researchers have brought more attention to diamond composites. In this paper, Fe-based impregnated diamond composites for drill bits were fabricated by using a pressureless infiltration sintering method at 970 °C for 5 min. In addition, boron was introduced into Fe-based diamond composites. The influence of boron on the density, hardness, bending strength, grinding ratio, and microstructure was investigated. An Fe-based diamond composite with 1 wt % B has an optimal overall performance, the grinding ratio especially improving by 80%. After comparing with tungsten carbide (WC)-based diamond composites with and without 1 wt % B, results showed that the Fe-based diamond composite with 1 wt % B exhibits higher bending strength and wear resistance, being satisfactory to bit needs. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Intrinsic Flame-Retardant and Thermally Stable Epoxy Endowed by a Highly Efficient, Multifunctional Curing Agent
Materials 2016, 9(12), 1008; doi:10.3390/ma9121008
Received: 2 November 2016 / Revised: 30 November 2016 / Accepted: 5 December 2016 / Published: 12 December 2016
Cited by 1 | PDF Full-text (7095 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
It is difficult to realize flame retardancy of epoxy without suffering much detriment in thermal stability. To solve the problem, a super-efficient phosphorus-nitrogen-containing reactive-type flame retardant, 10-(hydroxy(4-hydroxyphenyl)methyl)-5,10-dihydrophenophosphazinine-10-oxide (HB-DPPA) is synthesized and characterized. When it is used as a co-curing agent of 4,4′-methylenedianiline (DDM)
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It is difficult to realize flame retardancy of epoxy without suffering much detriment in thermal stability. To solve the problem, a super-efficient phosphorus-nitrogen-containing reactive-type flame retardant, 10-(hydroxy(4-hydroxyphenyl)methyl)-5,10-dihydrophenophosphazinine-10-oxide (HB-DPPA) is synthesized and characterized. When it is used as a co-curing agent of 4,4′-methylenedianiline (DDM) for curing diglycidyl ether of bisphenol A (DGEBA), the cured epoxy achieves UL-94 V-0 rating with the limiting oxygen index of 29.3%. In this case, the phosphorus content in the system is exceptionally low (0.18 wt %). To the best of our knowledge, it currently has the highest efficiency among similar epoxy systems. Such excellent flame retardancy originates from the exclusive chemical structure of the phenophosphazine moiety, in which the phosphorus element is stabilized by the two adjacent aromatic rings. The action in the condensed phase is enhanced and followed by pressurization of the pyrolytic gases that induces the blowing-out effect during combustion. The cone calorimeter result reveals the formation of a unique intumescent char structure with five discernible layers. Owing to the super-efficient flame retardancy and the rigid molecular structure of HB-DPPA, the flame-retardant epoxy acquires high thermal stability and its initial decomposition temperature only decreases by 4.6 °C as compared with the unmodified one. Full article
(This article belongs to the Special Issue Flame Retardant Polymeric Materials)
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Open AccessArticle Ferrite Film Loaded Frequency Selective Metamaterials for Sub-GHz Applications
Materials 2016, 9(12), 1009; doi:10.3390/ma9121009
Received: 11 September 2016 / Revised: 28 November 2016 / Accepted: 29 November 2016 / Published: 13 December 2016
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Abstract
Electromagnetic metamaterials are constructed with sub-wavelength structures that exhibit particular electromagnetic properties under a certain frequency range. Because the form-factor of the substructures has to be comparable to the wavelength of the operating frequency, few papers have discussed the metamaterials under GHz frequency.
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Electromagnetic metamaterials are constructed with sub-wavelength structures that exhibit particular electromagnetic properties under a certain frequency range. Because the form-factor of the substructures has to be comparable to the wavelength of the operating frequency, few papers have discussed the metamaterials under GHz frequency. In this paper, we developed an innovative method to reduce the resonant frequency of metamaterals. By integrating the meta-structures with ferrite materials of higher permeability, the cell size of the meta-structure can be scaled down. This paper describes the methodology, design, and development of low-profile GHz ferrite loaded metamaterials. A ferrite film with a permeability of 20 could reduce the resonant frequency of metamaterials by up to 50%. A prototype has been fabricated and the measurement data align well with the simulation results. Because of the lowered operational frequency, the proposed ferrite loaded metamaterials offer more flexibility for various sub-GHz microwave applications, such as cloaks, absorbers, and frequency selective surfaces. Full article
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Open AccessArticle Two-Level Micro-to-Nanoscale Hierarchical TiO2 Nanolayers on Titanium Surface
Materials 2016, 9(12), 1010; doi:10.3390/ma9121010
Received: 5 October 2016 / Revised: 29 November 2016 / Accepted: 6 December 2016 / Published: 13 December 2016
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Abstract
Joint replacement is being actively developed within modern orthopedics. One novel material providing fast implantation is bioactive coatings. The synthesis of targeted nanocoatings on metallic nanotitanium surface is reported in this paper. TiO2-based micro- and nanocoatings were produced by sol-gel synthesis
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Joint replacement is being actively developed within modern orthopedics. One novel material providing fast implantation is bioactive coatings. The synthesis of targeted nanocoatings on metallic nanotitanium surface is reported in this paper. TiO2-based micro- and nanocoatings were produced by sol-gel synthesis using dip-coating technology with subsequent fast (shock) drying in hot plate mode at 400 °C. As a result of shock drying, the two-level hierarchical TiO2 nanolayer on the nanotitanium was obtained. This two-level hierarchy includes nanorelief of porous xerogel and microrelief of the micron-sized “defect” network (a crack network). The thickness of TiO2 nanolayers was controlled by repeating dip-coating process the necessary number of times after the first layer deposition. The state of the MS3T3-E1 osteoblast cell line (young cells that form bone tissue) on the two-level hierarchical surface has been studied. Particularly, adhesion character, adhesion time and morphology have been studied. The reported results may serve the starting point for the development of novel bioactive coatings for bone and teeth implants. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Modeling of Thermal Conductivity of CVI-Densified Composites at Fiber and Bundle Level
Materials 2016, 9(12), 1011; doi:10.3390/ma9121011
Received: 13 October 2016 / Revised: 25 November 2016 / Accepted: 29 November 2016 / Published: 13 December 2016
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Abstract
The evolution of the thermal conductivities of the unidirectional, 2D woven and 3D braided composites during the CVI (chemical vapor infiltration) process have been numerically studied by the finite element method. The results show that the dual-scale pores play an important role in
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The evolution of the thermal conductivities of the unidirectional, 2D woven and 3D braided composites during the CVI (chemical vapor infiltration) process have been numerically studied by the finite element method. The results show that the dual-scale pores play an important role in the thermal conduction of the CVI-densified composites. According to our results, two thermal conductivity models applicable for CVI process have been developed. The sensitivity analysis demonstrates the parameter with the most influence on the CVI-densified composites’ thermal conductivity is matrix cracking’s density, followed by volume fraction of the bundle and thermal conductance of the matrix cracks, finally by micro-porosity inside the bundles and macro-porosity between the bundles. The obtained results are well consistent with the reported data, thus our models could be useful for designing the processing and performance of the CVI-densified composites. Full article
(This article belongs to the Special Issue Textile Composites)
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Open AccessArticle Preparation of TiO2-Decorated Boron Particles by Wet Ball Milling and their Photoelectrochemical Hydrogen and Oxygen Evolution Reactions
Materials 2016, 9(12), 1012; doi:10.3390/ma9121012
Received: 1 October 2016 / Revised: 19 November 2016 / Accepted: 7 December 2016 / Published: 14 December 2016
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Abstract
TiO2-coated boron particles were prepared by a wet ball milling method, with the particle size distribution and average particle size being easily controlled by varying the milling operation time. Based on the results from X-ray photoelectron spectroscopy, transmission electron microscopy, energy
[...] Read more.
TiO2-coated boron particles were prepared by a wet ball milling method, with the particle size distribution and average particle size being easily controlled by varying the milling operation time. Based on the results from X-ray photoelectron spectroscopy, transmission electron microscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy, it was confirmed that the initial oxide layer on the boron particles surface was removed by the wet milling process, and that a new B–O–Ti bond was formed on the boron surface. The uniform TiO2 layer on the 150 nm boron particles was estimated to be 10 nm thick. Based on linear sweep voltammetry, cyclic voltammetry, current-time amperometry, and electrochemical impedance analyses, the potential for the application of TiO2-coated boron particles as a photoelectrochemical catalyst was demonstrated. A current of 250 μA was obtained at a potential of 0.5 V for hydrogen evolution, with an onset potential near to 0.0 V. Finally, a current of 220 μA was obtained at a potential of 1.0 V for oxygen evolution. Full article
(This article belongs to the Section Materials for Energy Applications)
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Open AccessArticle Strain Rate Behavior in Tension of Reinforcing Steels HPB235, HRB335, HRB400, and HRB500
Materials 2016, 9(12), 1013; doi:10.3390/ma9121013
Received: 16 November 2016 / Revised: 5 December 2016 / Accepted: 9 December 2016 / Published: 15 December 2016
Cited by 2 | PDF Full-text (2689 KB) | HTML Full-text | XML Full-text
Abstract
The strain rate effect of reinforcing steel bars is generally indispensable for modeling the dynamic responses of reinforced concrete structures in blast and impact events. A systematic experimental investigation was conducted on the strain rate behavior of reinforcing steel bar grades HPB235, HRB335,
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The strain rate effect of reinforcing steel bars is generally indispensable for modeling the dynamic responses of reinforced concrete structures in blast and impact events. A systematic experimental investigation was conducted on the strain rate behavior of reinforcing steel bar grades HPB235, HRB335, HRB400, and HRB500 which are widely used in the field of civil engineering in China. The dynamic testing was performed using a servo-hydraulic Instron VHS160/100-20 in a strain rate range from 2 to 75 s−1. Stress-strain curves at preset strain rates were obtained. The test data were then used to derive the parameters in a model based on the dynamic increase factors (DIFs) of strengths and the Johnson–Cook constitutive model. Results indicated that a significant strain rate effect was observed for the four rebar grades. The dynamic yield strengths increased from 13% to 41% and their ultimate strengths improved from 9% to 19% in the strain rate range during testing. The strain rate behavior of the four rebar grades could be appropriately predicted using the parameters in the model based on the DIFs of strengths and the Johnson–Cook model. Full article
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Open AccessArticle Microstructure-Dependent Visible-Light Driven Photoactivity of Sputtering-Assisted Synthesis of Sulfide-Based Visible-Light Sensitizer onto ZnO Nanorods
Materials 2016, 9(12), 1014; doi:10.3390/ma9121014
Received: 31 October 2016 / Revised: 3 December 2016 / Accepted: 7 December 2016 / Published: 15 December 2016
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Abstract
The ZnO-CdS core-shell composite nanorods with CdS shell layer thicknesses of 5 and 20 nm were synthesized by combining the hydrothermal growth of ZnO nanorods with the sputtering thin-film deposition of CdS crystallites. The microstructures and optical properties of the ZnO-CdS nanorods were
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The ZnO-CdS core-shell composite nanorods with CdS shell layer thicknesses of 5 and 20 nm were synthesized by combining the hydrothermal growth of ZnO nanorods with the sputtering thin-film deposition of CdS crystallites. The microstructures and optical properties of the ZnO-CdS nanorods were associated with the CdS shell layer thickness. A thicker CdS shell layer resulted in a rougher surface morphology, more crystal defects, and a broader optical absorbance edge in the ZnO-CdS rods. The ZnO-CdS (20 nm) nanorods thus engaged in more photoactivity in this study. When they were further subjected to a postannealing procedure in ambient Ar/H2, this resulted in the layer-like CdS shell layers being converted into the serrated CdS shell layers. By contrast, the ZnO-CdS nanorods conducted with the postannealing procedure exhibited superior photoactivity and photoelectrochemical performance; the substantial changes in the microstructures and optical properties of the composite nanorods following postannealing in this study might account for the observed results. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Role of Hydrogen Bonding in the Formation of Adenine Chains on Cu(110) Surfaces
Materials 2016, 9(12), 1016; doi:10.3390/ma9121016
Received: 30 October 2016 / Revised: 12 December 2016 / Accepted: 12 December 2016 / Published: 16 December 2016
Cited by 1 | PDF Full-text (2146 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Understanding the adsorption properties of DNA bases on metal surfaces is fundamental for the rational control of surface functionalization leading to the realisation of biocompatible devices for biosensing applications, such as monitoring of particular parameters within bio-organic environments and drug delivery. In this
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Understanding the adsorption properties of DNA bases on metal surfaces is fundamental for the rational control of surface functionalization leading to the realisation of biocompatible devices for biosensing applications, such as monitoring of particular parameters within bio-organic environments and drug delivery. In this study, the effects of deposition rate and substrate temperature on the adsorption behavior of adenine on Cu(110) surfaces have been investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) modeling, with a focus on the characterization of the morphology of the adsorbed layers. STM results revealed the formation of one-dimensional linear chains and ladder-like chains parallel to the [110] direction, when dosing at a low deposition rate at room temperature, followed by annealing to 490 K. Two mirror related, well-ordered chiral domains oriented at ±55° with respect to the [110] direction are formed upon deposition on a substrate kept at 490 K. The molecular structures observed via STM are rationalized and qualitatively described on the basis of the DFT modeling. The observation of a variety of ad-layer structures influenced by deposition rate and substrate temperature indicates that dynamic processes and hydrogen bonding play an important role in the self-assembly of adenine on the Cu(110) surface. Full article
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Open AccessArticle First Principles Study on the Interaction Mechanisms of Water Molecules on TiO2 Nanotubes
Materials 2016, 9(12), 1018; doi:10.3390/ma9121018
Received: 30 October 2016 / Revised: 1 December 2016 / Accepted: 8 December 2016 / Published: 16 December 2016
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Abstract
The adsorption properties of water molecules on TiO2 nanotubes (TiO2NT) and the interaction mechanisms between water molecules are studied by first principles calculations. The adsorption preferences of water molecules in molecular or dissociated states on clean and H-terminated TiO2
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The adsorption properties of water molecules on TiO2 nanotubes (TiO2NT) and the interaction mechanisms between water molecules are studied by first principles calculations. The adsorption preferences of water molecules in molecular or dissociated states on clean and H-terminated TiO2NT are evaluated. Adsorption of OH clusters on (0, 6) and (9, 0) TiO2 nanotubes are first studied. The smallest adsorption energies are −1.163 eV and −1.383 eV, respectively, by examining five different adsorption sites on each type of tube. Eight and six adsorption sites were considered for OH adsorbtion on the H terminated (0, 6) and (9, 0) nanotubes. Water molecules are reformed with the smallest adsorption energy of −4.796 eV on the former and of −5.013 eV on the latter nanotube, respectively. For the adsorption of a single water molecule on TiO2NT, the molecular state shows the strongest adsorption preference with an adsorption energy of −0.660 eV. The adsorption of multiple (two and three) water molecules on TiO2NT is also studied. The calculated results show that the interactions between water molecules greatly affect their adsorption properties. Competition occurs between the molecular and dissociated states. The electronic structures are calculated to clarify the interaction mechanisms between water molecules and TiO2NT. The bonding interactions between H from water and oxygen from TiO2NT may be the reason for the dissociation of water on TiO2NT. Full article
(This article belongs to the Special Issue Enhancing the Photocatalytic Activity of TiO2 Photocatalysts)
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Open AccessArticle Estimation of Soil-Water Characteristic Curves in Multiple-Cycles Using Membrane and TDR System
Materials 2016, 9(12), 1019; doi:10.3390/ma9121019
Received: 30 September 2016 / Revised: 28 November 2016 / Accepted: 13 December 2016 / Published: 17 December 2016
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Abstract
The objective of this study is to estimate multiple-cycles of the soil-water characteristic curve (SWCC) using an innovative volumetric pressure plate extractor (VPPE), which is incorporated with a membrane and time domain reflectometry (TDR). The pressure cell includes the membrane to reduce the
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The objective of this study is to estimate multiple-cycles of the soil-water characteristic curve (SWCC) using an innovative volumetric pressure plate extractor (VPPE), which is incorporated with a membrane and time domain reflectometry (TDR). The pressure cell includes the membrane to reduce the experimental time and the TDR probe to automatically estimate the volumetric water content. For the estimation of SWCC using the VPPE system, four specimens with different grain size and void ratio are prepared. The volumetric water contents of the specimens according to the matric suction are measured by the burette system and are estimated in the TDR system during five cycles of SWCC tests. The volumetric water contents estimated by the TDR system are almost identical to those determined by the burette system. The experimental time significantly decreases with the new VPPE. The hysteresis in the SWCC is largest in the first cycle and is nearly identical after 1.5 cycles. As the initial void ratio decreases, the air entry value increases. This study suggests that the new VPPE may effectively estimate multiple-cycles of the SWCC of unsaturated soils. Full article
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Open AccessArticle Viscoelastic Properties of the Chinese Fir (Cunninghamia lanceolata) during Moisture Sorption Processes Determined by Harmonic Tests
Materials 2016, 9(12), 1020; doi:10.3390/ma9121020
Received: 25 September 2016 / Revised: 23 November 2016 / Accepted: 5 December 2016 / Published: 17 December 2016
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Abstract
Measured by harmonic tests, the viscoelastic properties of Chinese fir during moisture sorption processes were examined under three relative humidity (RH) modes: RHramp, RHisohume, and RHstep. The stiffness decreased and damping increased as a function of the
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Measured by harmonic tests, the viscoelastic properties of Chinese fir during moisture sorption processes were examined under three relative humidity (RH) modes: RHramp, RHisohume, and RHstep. The stiffness decreased and damping increased as a function of the moisture content (MC), which is presumed to be the effect of plasticization and an unstable state. The increasing damping was associated with the breaking of hydrogen bonds and the formation of free volume within polymer networks. The changes of loss modulus ratio at 1 and 20 Hz, E1Hz/E20Hz, proved the changing trend of the unstable state. Higher ramping rates aggravated the unstable state at the RHramp period, and higher constant RH levels provided more recovery of the unstable state at the RHisohume period. Changes of viscoelastic properties were associated with RH (varied or remained constant), and the application of Boltzmann’s superposition principle is a good approach to simulate viscoelasticity development. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Organic-Inorganic Hydrophobic Nanocomposite Film with a Core-Shell Structure
Materials 2016, 9(12), 1021; doi:10.3390/ma9121021
Received: 23 September 2016 / Revised: 1 December 2016 / Accepted: 5 December 2016 / Published: 17 December 2016
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Abstract
A method to prepare novel organic-inorganic hydrophobic nanocomposite films was proposed by a site-specific polymerization process. The inorganic part, the core of the nanocomposite, is a ternary SiO2–Al2O3–TiO2 nanoparticles, which is grafted with methacryloxy propyl trimethoxyl
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A method to prepare novel organic-inorganic hydrophobic nanocomposite films was proposed by a site-specific polymerization process. The inorganic part, the core of the nanocomposite, is a ternary SiO2–Al2O3–TiO2 nanoparticles, which is grafted with methacryloxy propyl trimethoxyl silane (KH570), and wrapped by fluoride and siloxane polymers. The synthesized samples are characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrscopy, X-ray diffractometry (XRD), contact angle meter (CA), and scanning electron microscope (SEM). The results indicate that the novel organic-inorganic hydrophobic nanocomposite with a core-shell structure was synthesized successfully. XRD analysis reveals the nanocomposite film has an amorphous structure, and FTIR analysis indicates the nanoparticles react with a silane coupling agent (methacryloxy propyl trimethoxyl silane KH570). Interestingly, the morphology of the nanoparticle film is influenced by the composition of the core. Further, comparing with the film synthesized by silica nanoparticles, the film formed from SiO2–Al2O3–TiO2 nanoparticles has higher hydrophobic performance, i.e., the contact angle is greater than 101.7°. In addition, the TEM analysis reveals that the crystal structure of the particles can be changed at high temperatures. Full article
(This article belongs to the Special Issue Green Nanotechnology)
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Open AccessArticle Synthesis, Characterization, Tautomeric Structure and Solvatochromic Behavior of Novel 4-(5-Arylazo-2-Hydroxystyryl)-1-Methylpyridinium Iodide as Potential Molecular Photoprobe
Materials 2016, 9(12), 1022; doi:10.3390/ma9121022
Received: 21 October 2016 / Revised: 7 December 2016 / Accepted: 12 December 2016 / Published: 19 December 2016
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Abstract
A novel series of the title compound 4-(5-arylazo-2-hydroxystyryl)-1-methylpyridinium iodide 6 has been synthesized via condensation reactions of the arylazosalicylaldehyde derivatives 4ai with 1-methyl-picolinium iodide 5. The structures of the new arylazo compounds were characterized by 1H NMR, IR, mass
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A novel series of the title compound 4-(5-arylazo-2-hydroxystyryl)-1-methylpyridinium iodide 6 has been synthesized via condensation reactions of the arylazosalicylaldehyde derivatives 4ai with 1-methyl-picolinium iodide 5. The structures of the new arylazo compounds were characterized by 1H NMR, IR, mass spectroscopy, as well as spectral and elemental analyses. The electronic absorption spectra of arylazomerocyanine compounds 6 were measured in different buffer solutions and solvents. The pK′s and pK*′s in both the ground and excited states, respectively, were determined for the series and their correlations with the Hammett equation were examined. The results indicated that the title arylazomerocyanine dyes 6 exist in the azo form 6A in both ground and excited states. The substituent and solvent effects (solvatochromism) of the title compound arylazomerocyanine dyes were determined using the Kamlet-Taft equation and subsequently discussed. Full article
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Open AccessArticle Effect of Repetition Rate on Femtosecond Laser-Induced Homogenous Microstructures
Materials 2016, 9(12), 1023; doi:10.3390/ma9121023
Received: 1 November 2016 / Revised: 7 December 2016 / Accepted: 13 December 2016 / Published: 19 December 2016
Cited by 2 | PDF Full-text (3396 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We report on the effect of repetition rate on the formation and surface texture of the laser induced homogenous microstructures. Different microstructures were micromachined on copper (Cu) and titanium (Ti) using femtosecond pulses at 1 and 10 kHz. We studied the effect of
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We report on the effect of repetition rate on the formation and surface texture of the laser induced homogenous microstructures. Different microstructures were micromachined on copper (Cu) and titanium (Ti) using femtosecond pulses at 1 and 10 kHz. We studied the effect of the repetition rate on structure formation by comparing the threshold accumulated pulse ( F Σ p u l s e ) values and the effect on the surface texture through lacunarity analysis. Machining both metals at low F Σ p u l s e resulted in microstructures with higher lacunarity at 10 kHz compared to 1 kHz. On increasing F Σ p u l s e , the microstructures showed higher lacunarity at 1 kHz. The effect of the repetition rate on the threshold F Σ p u l s e values were, however, considerably different on the two metals. With an increase in repetition rate, we observed a decrease in the threshold F Σ p u l s e on Cu, while on Ti we observed an increase. These differences were successfully allied to the respective material characteristics and the resulting melt dynamics. While machining Ti at 10 kHz, the melt layer induced by one laser pulse persists until the next pulse arrives, acting as a dielectric for the subsequent pulse, thereby increasing F Σ p u l s e . However, on Cu, the melt layer quickly resolidifies and no such dielectric like phase is observed. Our study contributes to the current knowledge on the effect of the repetition rate as an irradiation parameter. Full article
(This article belongs to the Special Issue Ultrafast Laser-Based Manufacturing)
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Open AccessArticle Application of Ni-Oxide@TiO2 Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors
Materials 2016, 9(12), 1024; doi:10.3390/ma9121024
Received: 14 October 2016 / Revised: 20 November 2016 / Accepted: 16 December 2016 / Published: 20 December 2016
Cited by 1 | PDF Full-text (4533 KB) | HTML Full-text | XML Full-text
Abstract
Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO2 core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue)
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Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO2 core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue) degradation under ultraviolet (UV) and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO2 overlayer coating. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Micromechanical Properties of a New Polymeric Microcapsule for Self-Healing Cementitious Materials
Materials 2016, 9(12), 1025; doi:10.3390/ma9121025
Received: 8 November 2016 / Revised: 5 December 2016 / Accepted: 15 December 2016 / Published: 20 December 2016
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Abstract
Self-healing cementitious materials containing a microencapsulated healing agent are appealing due to their great application potential in improving the serviceability and durability of concrete structures. In this study, poly(phenol–formaldehyde) (PF) microcapsules that aim to provide a self-healing function for cementitious materials were prepared
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Self-healing cementitious materials containing a microencapsulated healing agent are appealing due to their great application potential in improving the serviceability and durability of concrete structures. In this study, poly(phenol–formaldehyde) (PF) microcapsules that aim to provide a self-healing function for cementitious materials were prepared by an in situ polymerization reaction. Size gradation of the synthesized microcapsules was achieved through a series of sieving processes. The shell thickness and the diameter of single microcapsules was accurately measured under environmental scanning electron microscopy (ESEM). The relationship between the physical properties of the synthesized microcapsules and their micromechanical properties were investigated using nanoindentation. The results of the mechanical tests show that, with the increase of the mean size of microcapsules and the decrease of shell thickness, the mechanical force required to trigger the self-healing function of microcapsules increased correspondingly from 68.5 ± 41.6 mN to 198.5 ± 31.6 mN, featuring a multi-sensitive trigger function. Finally, the rupture behavior and crack surface of cement paste with embedded microcapsules were observed and analyzed using X-ray computed tomography (XCT). The synthesized PF microcapsules may find potential application in self-healing cementitious materials. Full article
(This article belongs to the Special Issue Self-Healing Concrete)
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Open AccessArticle The Effect of the Substituent Position on the Two-Photon Absorption Performances of Dibenzylideneacetone-Based Isomers
Materials 2016, 9(12), 1026; doi:10.3390/ma9121026
Received: 31 October 2016 / Revised: 6 December 2016 / Accepted: 14 December 2016 / Published: 20 December 2016
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Abstract
The two-photon absorption and optical limiting properties of two dibenzylideneacetone derivatives with different substituent positions have been theoretically investigated by solving the coupled rate equations-field intensity equation in the nanosecond time domain using an iterative predictor-corrector finite-difference time-domain method. The calculations show that
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The two-photon absorption and optical limiting properties of two dibenzylideneacetone derivatives with different substituent positions have been theoretically investigated by solving the coupled rate equations-field intensity equation in the nanosecond time domain using an iterative predictor-corrector finite-difference time-domain method. The calculations show that the electronic structure, the transition dipole moment, the energy gap between the highest occupied orbital (HOMO) and the lowest unoccupied orbital (LUMO), and the pumping rate for the two molecules are quite different due to the different position of chlorine atoms. Importantly, two-photon absorption and optical limiting properties of the molecules depend crucially on the substituent positions of the terminal group, indicating that subtle manipulation on the molecule can affect the nonlinear optical properties of the medium. Full article
(This article belongs to the Special Issue Two-Photon Absorption Materials)
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Open AccessArticle Ceramic Ti—B Composites Synthesized by Combustion Followed by High-Temperature Deformation
Materials 2016, 9(12), 1027; doi:10.3390/ma9121027
Received: 7 November 2016 / Revised: 10 December 2016 / Accepted: 16 December 2016 / Published: 20 December 2016
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Abstract
Long compact cylindrical rods, which consist of a titanium monoboride-based TiB—30 wt % Ti ceramic composite material, are synthesized during combustion of the initial components (titanium, boron) followed by high-temperature deformation. High-temperature deformation is found to affect the orientation of the hardening titanium
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Long compact cylindrical rods, which consist of a titanium monoboride-based TiB—30 wt % Ti ceramic composite material, are synthesized during combustion of the initial components (titanium, boron) followed by high-temperature deformation. High-temperature deformation is found to affect the orientation of the hardening titanium monoboride phase in the sample volume and the phase composition of the sample. The combustion temperature is studied as a function of the relative density of the initial workpiece under the experimental conditions. Full article
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Open AccessArticle Synthesis and Structural Characterization of Silver Nanoparticles Stabilized with 3-Mercapto-1-Propansulfonate and 1-Thioglucose Mixed Thiols for Antibacterial Applications
Materials 2016, 9(12), 1028; doi:10.3390/ma9121028
Received: 22 November 2016 / Revised: 14 December 2016 / Accepted: 15 December 2016 / Published: 20 December 2016
Cited by 3 | PDF Full-text (3272 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The synthesis, characterization and assessment of the antibacterial properties of hydrophilic silver nanoparticles (AgNPs) were investigated with the aim to probe their suitability for innovative applications in the field of nanobiotechnology. First, silver nanoparticles were synthetized and functionalized with two capping agents, namely
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The synthesis, characterization and assessment of the antibacterial properties of hydrophilic silver nanoparticles (AgNPs) were investigated with the aim to probe their suitability for innovative applications in the field of nanobiotechnology. First, silver nanoparticles were synthetized and functionalized with two capping agents, namely 3-mercapto-1-propansulfonate (3MPS) and 1-β-thio-d-glucose (TG). The investigation of the structural and electronic properties of the nano-systems was carried out by means of X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). XPS data provided information about the system stability and the interactions between the metallic surface and the organic ligands. In addition, XPS data allowed us to achieve a deep understanding of the influence of the thiols stoichiometric ratio on the electronic properties and stability of AgNPs. In order to shed light on the structural and electronic local properties at Ag atoms sites, XAS at Ag K-Edge was successfully applied; furthermore, the combination of Dynamic Light Scattering (DLS) and XAS results allowed determining AgNPs sizes, ranging between 3 and 13 nm. Finally, preliminary studies on the antibacterial properties of AgNPs showed promising results on four of six multidrug-resistant bacteria belonging to the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter sp.). Full article
(This article belongs to the Special Issue Noble Metal Nanoparticles)
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Open AccessArticle An Experimental Study of Mortars with Recycled Ceramic Aggregates: Deduction and Prediction of the Stress-Strain
Materials 2016, 9(12), 1029; doi:10.3390/ma9121029
Received: 18 October 2016 / Revised: 28 November 2016 / Accepted: 13 December 2016 / Published: 21 December 2016
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Abstract
The difficult current environmental situation, caused by construction industry residues containing ceramic materials, could be improved by using these materials as recycled aggregates in mortars, with their processing causing a reduction in their use in landfill, contributing to recycling and also minimizing the
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The difficult current environmental situation, caused by construction industry residues containing ceramic materials, could be improved by using these materials as recycled aggregates in mortars, with their processing causing a reduction in their use in landfill, contributing to recycling and also minimizing the consumption of virgin materials. Although some research is currently being carried out into recycled mortars, little is known about their stress-strain (σ-ε); therefore, this work will provide the experimental results obtained from recycled mortars with recycled ceramic aggregates (with contents of 0%, 10%, 20%, 30%, 50% and 100%), such as the density and compression strength, as well as the σ-ε curves representative of their behavior. The values obtained from the analytical process of the results in order to finally obtain, through numerical analysis, the equations to predict their behavior (related to their recycled content) are those of: σ (elastic ranges and failure maximum), ε (elastic ranges and failure maximum), and Resilience and Toughness. At the end of the investigation, it is established that mortars with recycled ceramic aggregate contents of up to 20% could be assimilated just like mortars with the usual aggregates, and the obtained prediction equations could be used in cases of similar applications. Full article
(This article belongs to the Special Issue Granular Materials)
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Open AccessArticle A Size and Boundary Effects Model for Quasi-Brittle Fracture
Materials 2016, 9(12), 1030; doi:10.3390/ma9121030
Received: 27 November 2016 / Revised: 18 December 2016 / Accepted: 19 December 2016 / Published: 21 December 2016
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Abstract
The fracture behaviors of quasi-brittle materials are commonly specimen size (size effect) and crack size (boundary effect) dependent. In this study, a new failure model is developed for characterizing the size and boundary effects. The derivative of the energy release rate is firstly
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The fracture behaviors of quasi-brittle materials are commonly specimen size (size effect) and crack size (boundary effect) dependent. In this study, a new failure model is developed for characterizing the size and boundary effects. The derivative of the energy release rate is firstly introduced to predict the nominal strength dominated by the strength mechanism. Combined with the energy criterion for the energy mechanism, an asymptotic model is developed to capture the effect of any crack size on the nominal strength, and its expression for geometrically similar specimens is also established, which is able to characterize the size effect. Detailed comparisons of the proposed model with the size effect law and the boundary effect model are performed, respectively. The nominal strength predictions based on the proposed model are validated with the experimental results of cracked three-point bending beam specimens made of concrete, of limestone and of hardened cement paste and compared with the model predictions given by the size effect law and the boundary effect model. Full article
(This article belongs to the Special Issue The Brittle Failure of Different Materials)
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Review

Jump to: Research

Open AccessReview Admixtures in Cement-Matrix Composites for Mechanical Reinforcement, Sustainability, and Smart Features
Materials 2016, 9(12), 972; doi:10.3390/ma9120972
Received: 31 October 2016 / Revised: 18 November 2016 / Accepted: 25 November 2016 / Published: 30 November 2016
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Abstract
For more than a century, several inclusions have been mixed with Portland cement—nowadays the most-consumed construction material worldwide—to improve both the strength and durability required for construction. The present paper describes the different families of inclusions that can be combined with cement matrix
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For more than a century, several inclusions have been mixed with Portland cement—nowadays the most-consumed construction material worldwide—to improve both the strength and durability required for construction. The present paper describes the different families of inclusions that can be combined with cement matrix and reviews the achievements reported to date regarding mechanical performance, as well as two other innovative functionalities of growing importance: reducing the high carbon footprint of Portland cement, and obtaining new smart features. Nanomaterials stand out in the production of such advanced features, allowing the construction of smart or multi-functional structures by means of thermal- and strain-sensing, and photocatalytic properties. The first self-cleaning concretes (photocatalytic) have reached the markets. In this sense, it is expected that smart concretes will be commercialized to address specialized needs in construction and architecture. Conversely, other inclusions that enhance strength or reduce the environmental impact remain in the research stage, in spite of the promising results reported in these issues. Despite the fact that such functionalities are especially profitable in the case of massive cement consumption, the shift from the deeply established Portland cement to green cements still has to overcome economic, institutional, and technical barriers. Full article
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Open AccessReview Fabrication of Porous Materials from Natural/Synthetic Biopolymers and Their Composites
Materials 2016, 9(12), 991; doi:10.3390/ma9120991
Received: 23 October 2016 / Revised: 18 November 2016 / Accepted: 22 November 2016 / Published: 7 December 2016
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Abstract
Biopolymers and their applications have been widely studied in recent years. Replacing the oil based polymer materials with biopolymers in a sustainable manner might give not only a competitive advantage but, in addition, they possess unique properties which cannot be emulated by conventional
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Biopolymers and their applications have been widely studied in recent years. Replacing the oil based polymer materials with biopolymers in a sustainable manner might give not only a competitive advantage but, in addition, they possess unique properties which cannot be emulated by conventional polymers. This review covers the fabrication of porous materials from natural biopolymers (cellulose, chitosan, collagen), synthetic biopolymers (poly(lactic acid), poly(lactic-co-glycolic acid)) and their composite materials. Properties of biopolymers strongly depend on the polymer structure and are of great importance when fabricating the polymer into intended applications. Biopolymers find a large spectrum of application in the medical field. Other fields such as packaging, technical, environmental, agricultural and food are also gaining importance. The introduction of porosity into a biomaterial broadens the scope of applications. There are many techniques used to fabricate porous polymers. Fabrication methods, including the basic and conventional techniques to the more recent ones, are reviewed. Advantages and limitations of each method are discussed in detail. Special emphasis is placed on the pore characteristics of biomaterials used for various applications. This review can aid in furthering our understanding of the fabrication methods and about controlling the porosity and microarchitecture of porous biopolymer materials. Full article
(This article belongs to the Section Porous Materials)
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Open AccessReview Fc-Binding Ligands of Immunoglobulin G: An Overview of High Affinity Proteins and Peptides
Materials 2016, 9(12), 994; doi:10.3390/ma9120994
Received: 15 October 2016 / Revised: 26 November 2016 / Accepted: 29 November 2016 / Published: 8 December 2016
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Abstract
The rapidly increasing application of antibodies has inspired the development of several novel methods to isolate and target antibodies using smart biomaterials that mimic the binding of Fc-receptors to antibodies. The Fc-binding domain of antibodies is the primary binding site for e.g., effector
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The rapidly increasing application of antibodies has inspired the development of several novel methods to isolate and target antibodies using smart biomaterials that mimic the binding of Fc-receptors to antibodies. The Fc-binding domain of antibodies is the primary binding site for e.g., effector proteins and secondary antibodies, whereas antigens bind to the Fab region. Protein A, G, and L, surface proteins expressed by pathogenic bacteria, are well known to bind immunoglobulin and have been widely exploited in antibody purification strategies. Several difficulties are encountered when bacterial proteins are used in antibody research and application. One of the major obstacles hampering the use of bacterial proteins is sample contamination with trace amounts of these proteins, which can invoke an immune response in the host. Many research groups actively develop synthetic ligands that are able to selectively and strongly bind to antibodies. Among the reported ligands, peptides that bind to the Fc-domain of antibodies are attractive tools in antibody research. Besides their use as high affinity ligands in antibody purification chromatography, Fc-binding peptides are applied e.g., to localize antibodies on nanomaterials and to increase the half-life of proteins in serum. In this review, recent developments of Fc-binding peptides are presented and their binding characteristics and diverse applications are discussed. Full article
(This article belongs to the Special Issue Smart Biomaterials and Biointerfaces)
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Open AccessReview Atomic Layer Deposition of Silicon Nitride Thin Films: A Review of Recent Progress, Challenges, and Outlooks
Materials 2016, 9(12), 1007; doi:10.3390/ma9121007
Received: 8 November 2016 / Revised: 1 December 2016 / Accepted: 6 December 2016 / Published: 12 December 2016
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Abstract
With the continued miniaturization of devices in the semiconductor industry, atomic layer deposition (ALD) of silicon nitride thin films (SiNx) has attracted great interest due to the inherent benefits of this process compared to other silicon nitride thin film deposition techniques.
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With the continued miniaturization of devices in the semiconductor industry, atomic layer deposition (ALD) of silicon nitride thin films (SiNx) has attracted great interest due to the inherent benefits of this process compared to other silicon nitride thin film deposition techniques. These benefits include not only high conformality and atomic-scale thickness control, but also low deposition temperatures. Over the past 20 years, recognition of the remarkable features of SiNx ALD, reinforced by experimental and theoretical investigations of the underlying surface reaction mechanism, has contributed to the development and widespread use of ALD SiNx thin films in both laboratory studies and industrial applications. Such recognition has spurred ever-increasing opportunities for the applications of the SiNx ALD technique in various arenas. Nevertheless, this technique still faces a number of challenges, which should be addressed through a collaborative effort between academia and industry. It is expected that the SiNx ALD will be further perceived as an indispensable technique for scaling next-generation ultra-large-scale integration (ULSI) technology. In this review, the authors examine the current research progress, challenges and future prospects of the SiNx ALD technique. Full article
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Open AccessReview Nano-Inclusions Applied in Cement-Matrix Composites: A Review
Materials 2016, 9(12), 1015; doi:10.3390/ma9121015
Received: 21 October 2016 / Revised: 5 December 2016 / Accepted: 9 December 2016 / Published: 16 December 2016
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Abstract
Research on cement-based materials is trying to exploit the synergies that nanomaterials can provide. This paper describes the findings reported in the last decade on the improvement of these materials regarding, on the one hand, their mechanical performance and, on the other hand,
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Research on cement-based materials is trying to exploit the synergies that nanomaterials can provide. This paper describes the findings reported in the last decade on the improvement of these materials regarding, on the one hand, their mechanical performance and, on the other hand, the new properties they provide. These features are mainly based on the electrical and chemical characteristics of nanomaterials, thus allowing cement-based elements to acquire “smart” functions. In this paper, we provide a quantitative approach to the reinforcements achieved to date. The fundamental concepts of nanoscience are introduced and the need of both sophisticated devices to identify nanostructures and techniques to disperse nanomaterials in the cement paste are also highlighted. Promising results have been obtained, but, in order to turn these advances into commercial products, technical, social and standardisation barriers should be overcome. From the results collected, it can be deduced that nanomaterials are able to reduce the consumption of cement because of their reinforcing effect, as well as to convert cement-based products into electric/thermal sensors or crack repairing materials. The main obstacle to foster the implementation of such applications worldwide is the high cost of their synthesis and dispersion techniques, especially for carbon nanotubes and graphene oxide. Full article
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Open AccessReview Secondary Electron Emission Materials for Transmission Dynodes in Novel Photomultipliers: A Review
Materials 2016, 9(12), 1017; doi:10.3390/ma9121017
Received: 8 August 2016 / Revised: 1 December 2016 / Accepted: 6 December 2016 / Published: 16 December 2016
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Abstract
Secondary electron emission materials are reviewed with the aim of providing guidelines for the future development of novel transmission dynodes. Materials with reflection secondary electron yield higher than three and transmission secondary electron yield higher than one are tabulated for easy reference. Generations
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Secondary electron emission materials are reviewed with the aim of providing guidelines for the future development of novel transmission dynodes. Materials with reflection secondary electron yield higher than three and transmission secondary electron yield higher than one are tabulated for easy reference. Generations of transmission dynodes are listed in the order of the invention time with a special focus on the most recent atomic-layer-deposition synthesized transmission dynodes. Based on the knowledge gained from the survey of secondary election emission materials with high secondary electron yield, an outlook of possible improvements upon the state-of-the-art transmission dynodes is provided. Full article
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