http://www.mdpi.com/journal/materials Latest open access articles published in Materials at http://www.mdpi.com/journal/materials http://www.mdpi.com/1996-1944/6/6/2508 Low-pH cements are designed to be used in underground repositories for high level waste. When they are based on Ordinary Portland Cements (OPC), high mineral admixture contents must be used which significantly modify their microstructure properties and performance. This paper evaluates the microstructure evolution of low-pH cement pastes based on OPC plus silica fume and/or fly ashes, using Mid-Infrared and Near-Infrared spectroscopy to detect cement pastes mainly composed of high polymerized C-A-S-H gels with low C/S ratios. In addition, the lower pore solution pH of these special cementitious materials have been monitored with embedded metallic sensors. Besides, as the use of reinforced concrete can be required in underground repositories, the influence of low-pH cementitious materials on steel reinforcement corrosion was analysed. Due to their lower pore solution pH and their different pore solution chemical composition a clear influence on steel reinforcement corrosion was detected. Materials 2013-06-18 6 6 Article 10.3390/ma6062508 2508 2521 1996-1944 2013-06-18 doi: 10.3390/ma6062508 José Calvo Mercedes Moreno María Alonso Ana López Juan Olmo http://www.mdpi.com/1996-1944/6/6/2497 In this report, a technique for rapid synthesis of ZnO microstructures by microwave-assisted heating of precursors at hydrothermal conditions is demonstrated. Further, the reaction mechanism for the growth of ZnO microstructures is analyzed. An accelerated rate of reaction obtained using microwaves enables a dissolution-recrystallization mechanism for generation of one dimensional (1D) rod-like structures, thereby showing that time of reaction can be used to dictate ZnO microstructure morphology. Materials 2013-06-18 6 6 Article 10.3390/ma6062497 2497 2507 1996-1944 2013-06-18 doi: 10.3390/ma6062497 Ravish Majithia Jeffrey Speich Kenith Meissner http://www.mdpi.com/1996-1944/6/6/2483 This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE) enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs). The maximum values of the specific tensile and flexural strengths are achieved at a MAPE content of 5%–8%. The elongation increases rapidly at first and then continues slowly. The nearly complete integration of the wood fiber with the high-density polyethylene upon MAPE addition to WPC is examined, and two models of interfacial behavior are proposed. We examined the physical significance of both interfacial models and their ability to accurately describe the effects of MAPE addition. The mechanism of formation of the Model I interface and the integrated matrix is outlined based on the chemical reactions that may occur between the various components as a result of hydrogen bond formation or based on the principle of compatibility, resulting from similar polarity. The Model I fracture occurred on the outer surface of the interfacial layer, visually demonstrating the compatibilization effect of MAPE addition. Materials 2013-06-18 6 6 Article 10.3390/ma6062483 2483 2496 1996-1944 2013-06-18 doi: 10.3390/ma6062483 Jinxiang Chen Yong Wang Chenglong Gu Jianxun Liu Yufu Liu Min Li Yun Lu http://www.mdpi.com/1996-1944/6/6/2464 Measurements of nuclear spin relaxation times over a wide temperature range have been used to determine the interaction energies and molecular dynamics of light molecular gases trapped in the cages of microporous structures. The experiments are designed so that, in the cases explored, the local excitations and the corresponding heat capacities determine the observed nuclear spin-lattice relaxation times. The results indicate well-defined excitation energies for low densities of methane and hydrogen deuteride in zeolite structures. The values obtained for methane are consistent with Monte Carlo calculations of A.V. Kumar et al. The results also confirm the high mobility and diffusivity of hydrogen deuteride in zeolite structures at low temperatures as observed by neutron scattering. Materials 2013-06-17 6 6 Article 10.3390/ma6062464 2464 2482 1996-1944 2013-06-17 doi: 10.3390/ma6062464 Yu Ji Neil Sullivan Yibing Tang Jaha Hamida http://www.mdpi.com/1996-1944/6/6/2452 We propose a specific procedure to compute the inductance of a toroidal ferrite core as a function of the excitation current. The study includes the linear, intermediate and saturation regions. The procedure combines the use of Finite Element Analysis in 2D and experimental measurements. Through the two dimensional (2D) procedure we are able to achieve convergence, a reduction of computational cost and equivalent results to those computed by three dimensional (3D) simulations. The validation is carried out by comparing 2D, 3D and experimental results. Materials 2013-06-17 6 6 Article 10.3390/ma6062452 2452 2463 1996-1944 2013-06-17 doi: 10.3390/ma6062452 Rosa Salas Jorge Pleite http://www.mdpi.com/1996-1944/6/6/2436 Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyeletrolyte pectates (PEC) as a water-soluble natural polymer polysaccharide has been studied using both gasometric and weight loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing inhibitor concentration and decrease with increasing temperature. The inhibition action of PEC on Al metal surface was found to obey the Freundlich isotherm. Factors such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and temperature affecting the corrosion rates were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the kinetic results is discussed in the paper. Materials 2013-06-17 6 6 Article 10.3390/ma6062436 2436 2451 1996-1944 2013-06-17 doi: 10.3390/ma6062436 Refat Hassan Ishaq Zaafarany http://www.mdpi.com/1996-1944/6/6/2410 This paper describes the results obtained on the preparation of films composed of linter cellulose and the corresponding acetates. The acetylation was carried out in the LiCl/DMAc solvent system. Films were prepared from a LiCl/DMAc solution of cellulose acetates (degree of substitution, DS 0.8–2.9) mixed with linter cellulose (5, 10 and 15 wt %). Detailed characterization of the films revealed the following: (i) they exhibited fibrous structures on their surfaces. The strong tendency of the linter cellulose chains to aggregate in LiCl/DMAc suggests that these fibrous elements consist of cellulose chains, as can be deduced from SEM images of the film of cellulose proper; (ii) the cellulose acetate films obtained from samples with DS 2.1 and 2.9 exhibited microspheres on the surface, whose formation seems to be favored for acetates with higher DS; (iii) AFM analysis showed that, in general, the presence of cellulose increased both the asperity thickness and the surface roughness of the analyzed films, indicating that cellulose chains are at least partially organized in domains and not molecularly dispersed between acetate chains; and (iv) the films prepared from cellulose and acetates exhibited lower hygroscopicity than the acetate films, also suggesting that the cellulose chains are organized into domains, probably due to strong intermolecular interactions. The linter and sisal acetates (the latter from a prior study), and their respective films, were prepared using the same processes; however, the two sets of films presented more differences (as in humidity absorption, optical, and tensile properties) than similarities (as in some morphological aspects), most likely due to the different properties of the starting materials. Potential applications of the films prepared in tissue engineering scaffold coatings and/or drug delivery are mentioned. Materials 2013-06-14 6 6 Article 10.3390/ma6062410 2410 2435 1996-1944 2013-06-14 doi: 10.3390/ma6062410 Daniella Morgado Bruno Rodrigues Erika Almeida Omar Seoud Elisabete Frollini http://www.mdpi.com/1996-1944/6/6/2400 An effect of promoters such as calcium, aluminium, and potassium oxides and also addition of chromium and manganese on the structure of cobalt catalysts was examined. Studies of the catalytic ammonia decomposition over the cobalt catalysts are presented. The studies of the ammonia decomposition were carried out for various ammonia-hydrogen mixtures in which ammonia concentration varied in the range from 10% to 100%. Co(0) catalyst, promoted by oxides of aluminium, calcium, and potassium, showed the highest activity in the ammonia decomposition reaction. Contrary to expectations, it was found that chromium and manganese addition into the catalysts decreased their activity. Materials 2013-06-10 6 6 Article 10.3390/ma6062400 2400 2409 1996-1944 2013-06-10 doi: 10.3390/ma6062400 Zofia Lendzion-Bielun Urszula Narkiewicz Walerian Arabczyk http://www.mdpi.com/1996-1944/6/6/2393 In nanoscale structure sizes, the surface-to-bulk energy ratio is high and the surface effects must be taken into account. Surface effect plays a key role in accurately predicting the vibration behavior of nanostructures. In this paper, the wave behaviors of a single-walled carbon nanotube (CNT) conveying fluid are studied. The nonlocal Timoshenko beam theory is used and the surface effect is taken into account. It is found that the fluid can flow at a very high flow velocity and the wave propagates in the terahertz frequency range. The surface effects can significantly enhance the propagating frequency. This finding is different from the classical model where the surface effect is neglected. Materials 2013-06-10 6 6 Article 10.3390/ma6062393 2393 2399 1996-1944 2013-06-10 doi: 10.3390/ma6062393 Ye-Wei Zhang Tian-Zhi Yang Jian Zang Bo Fang http://www.mdpi.com/1996-1944/6/6/2372 Coumarin-based dyes have been successfully used in dye-sensitized solar cells, leading to photovoltaic conversion efficiencies of up to about 8%. Given the need to better understand the behavior of the dye adsorbed on the TiO2 nanoparticle, we report results of density functional theory (DFT) and time-dependent DFT (TD-DFT) studies of several coumarin-based dyes, as well as complex systems consisting of the dye bound to a TiO2 cluster. We provide the electronic structure and simulated UV-Vis spectra of the dyes alone and adsorbed to the cluster and discuss the matching with the solar spectrum. We display the energy level diagrams and the electron density of the key molecular orbitals and analyze the electron transfer from the dye to the oxide. Finally, we compare our theoretical results with the experimental data available and discuss the key issues that influence the device performance. Materials 2013-06-10 6 6 Article 10.3390/ma6062372 2372 2392 1996-1944 2013-06-10 doi: 10.3390/ma6062372 Corneliu Oprea Petre Panait Fanica Cimpoesu Marilena Ferbinteanu Mihai Gîrţu http://www.mdpi.com/1996-1944/6/6/2360 Buckypapers are thin sheets of randomly entangled carbon nanotubes, which are highly porous networks. They are strong candidates for a number of applications, such as reinforcing materials for composites. In this work, buckypapers were produced from multiwall carbon nanotubes, pre-treated by two different chemical processes, either an oxidation or an epoxidation reaction. Properties, such as porosity, the mechanical and electrical response are investigated. It was found that the chemical pretreatment of carbon nanotubes strongly affects the structural properties of the buckypapers and, consecutively, their mechanical and electrical performance. Materials 2013-06-10 6 6 Article 10.3390/ma6062360 2360 2371 1996-1944 2013-06-10 doi: 10.3390/ma6062360 George Trakakis Dimitrios Tasis John Parthenios Costas Galiotis Konstantinos Papagelis http://www.mdpi.com/1996-1944/6/6/2351 The present paper reports the use of an amphoteric copolymer, poly(diallylamine-co-maleic acid) (PDAMA), as a component of precursor layers (or sacrificial layers) for constructing free-standing layer-by-layer (LbL) films. A PDAMA-poly(styrenesulfonate) (PSS) film or PDAMA-poly(dimethyldiallylammonium chloride) (PDDA) film was coated on the surface of a quartz slide at pH 4.0 or 8.0, respectively, as a sacrificial layer that can be removed by changing the pH. The surface of the sacrificial layer was further covered with LbL films composed of poly(allylamine hydrochloride) (PAH) and PSS. The PAH-PSS films were released from the substrate upon immersing the film-coated quartz slide in acidic or neutral/basic solution, respectively, as a result of the pH-induced dissolution of the PDAMA-PDDA or PDAMA-PSS sacrificial layer. Thus, PDAMA-based sacrificial layers have been demonstrated to dissolve in both acidic and neutral solutions, depending on the type of counter polymer. The thicknesses of the sacrificial layers and released LbL films are crucial factors for constructing free-standing LbL films. The releasing kinetics also depended on the thickness of the crucial layers. The free-standing PAH-PSS films obtained were stable in water or in air in the dry state. PDAMA-based sacrificial layers may be useful in constructing free-standing LbL films containing biomolecules with limited pH stability. Materials 2013-06-06 6 6 Communication 10.3390/ma6062351 2351 2359 1996-1944 2013-06-06 doi: 10.3390/ma6062351 Baozhen Wang Yu Tokuda Koji Tomida Shigehiro Takahashi Katsuhiko Sato Jun-ichi Anzai http://www.mdpi.com/1996-1944/6/6/2295 Nanosilver, due to its small particle size and enormous specific surface area, facilitates more rapid dissolution of ions than the equivalent bulk material; potentially leading to increased toxicity of nanosilver. This, coupled with their capacity to adsorb biomolecules and interact with biological receptors can mean that nanoparticles can reach sub-cellular locations leading to potentially higher localized concentrations of ions once those particles start to dissolve or degrade in situ. Further complicating the story is the capacity for nanoparticles to generate reactive oxygen species, and to interact with, and potentially disturb the functioning of biomolecules such as proteins, enzymes and DNA. The fact that the nanoparticle size, shape, surface coating and a host of other factors contribute to these interactions, and that the particles themselves are evolving or ageing leads to further complications in terms of elucidating mechanisms of interaction and modes of action for silver nanoparticles, in contrast to dissolved silver species. This review aims to provide a critical assessment of the current understanding of silver nanoparticle toxicity, as well as to provide a set of pointers and guidelines for experimental design of future studies to assess the environmental and biological impacts of silver nanoparticles. In particular; in future we require a detailed description of the nanoparticles; their synthesis route and stabilisation mechanisms; their coating; and evolution and ageing under the exposure conditions of the assay. This would allow for comparison of data from different particles; different environmental or biological systems; and structure-activity or structure-property relationships to emerge as the basis for predictive toxicology. On the basis of currently available data; such comparisons or predictions are difficult; as the characterisation and time-resolved data is not available; and a full understanding of silver nanoparticle dissolution and ageing under different conditions is observed. Clear concerns are emerging regarding the overuse of nanosilver and the potential for bacterial resistance to develop. A significant conclusion includes the need for a risk—benefit analysis for all applications and eventually restrictions of the uses where a clear benefit cannot be demonstrated. Materials 2013-06-05 6 6 Review 10.3390/ma6062295 2295 2350 1996-1944 2013-06-05 doi: 10.3390/ma6062295 Bogumiła Reidy Andrea Haase Andreas Luch Kenneth Dawson Iseult Lynch http://www.mdpi.com/1996-1944/6/6/2285 Ramsdellite-type lithium titanate (Li2Ti3O7) powders were synthesized by performing ultrasonic spray pyrolysis, and their chemical and physical properties were characterized by performing Scanning Electron Microscope (SEM), powder X-ray Diffraction (XRD), and Inductively Coupled Plasma (ICP) analyses. The as-prepared Li2Ti3O7 precursor powders had spherical morphologies with hollow microstructures, but an irregularly shaped morphology was obtained after calcination above 900 °C. The ramsdellite Li2Ti3O7 crystal phase was obtained after the calcination at 1100 °C under an argon/hydrogen atmosphere. The first rechargeable capacity of the Li2Ti3O7 anode material was 168 mAh/g at 0.1 C and 82 mAh/g at 20 C, and the discharge capacity retention ratio was 99% at 1 C after the 500th cycle. The cycle performance of the Li2Ti3O7 anode was also highly stable at 50 °C, demonstrating the superiority of Li2Ti3O7 anode materials reported previously. Materials 2013-06-03 6 6 Article 10.3390/ma6062285 2285 2294 1996-1944 2013-06-03 doi: 10.3390/ma6062285 Takashi Ogihara Takayuki Kodera http://www.mdpi.com/1996-1944/6/6/2274 The influence of multi-walled carbon nanotubes (MWCNT) on the structural dynamic behavior of MWCNT/epoxy nanocomposites was investigated. Two different types of MWCNTs, pristine MWCNT and functionalized MWCNT, were used in this study. Carboxylic acid-functionalized MWCNTs (MWCNT-COOH) were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid and characterized by Fourier transform infrared spectroscopy (FTIR). Dynamic behaviors of the MWCNT reinforced nanocomposite including the natural frequency and damping ratio were determined using free vibration test. Experimental results showed that the damping ratio of the nanocomposite decreases with the increase of the MWCNT addition, while the natural frequency is increasing with the increase of the MWCNT addition. Functionalized MWCNTs improved the interfacial bonding between the nanotubes and epoxy resin resulting in the reduction of the interfacial energy dissipation ability and enhancement of the stiffness. Materials 2013-06-03 6 6 Article 10.3390/ma6062274 2274 2284 1996-1944 2013-06-03 doi: 10.3390/ma6062274 Shiuh-Chuan Her Chun-Yu Lai http://www.mdpi.com/1996-1944/6/6/2262 A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements, thereby confirming the proposed reactors ability to extend the existing sheath fields by up to 7 mm. A 7 mbar growth atmosphere combined with a 25 W plasma permitted the concurrent growth and alignment of carbon nanotubes with electric fields of the order of 0.04 V μm−1 with linear packing densities of up to ~5 × 104 cm−1. These results open up the potential for multi-directional in situ alignment of carbon nanotubes providing one viable route to the fabrication of many novel optoelectronic devices. Materials 2013-05-31 6 6 Communication 10.3390/ma6062262 2262 2273 1996-1944 2013-05-31 doi: 10.3390/ma6062262 Matthew Cole William Milne http://www.mdpi.com/1996-1944/6/6/2240 Commercial α-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They also exhibited high moduli, which is characteristic of brittle materials. A higher temperature and higher pressure rate produced specimens with higher mechanical properties while low moisture content produced weaker specimens. Generally, the strong specimen had higher specific gravity and lower moisture content. However, some parameters did not follow the general trend e.g., thinner specimen showed much higher Young’s Modulus, although their specific gravity and moisture content remained similar to control, revealing a marked skin-effect which was confirmed by SEM observations. Materials 2013-05-30 6 6 Article 10.3390/ma6062240 2240 2261 1996-1944 2013-05-30 doi: 10.3390/ma6062240 Thibaud Pintiaux David Viet Virginie Vandenbossche Luc Rigal Antoine Rouilly http://www.mdpi.com/1996-1944/6/6/2229 Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/AlS.G.) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/AlS.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/AlS.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size. Materials 2013-05-30 6 6 Article 10.3390/ma6062229 2229 2239 1996-1944 2013-05-30 doi: 10.3390/ma6062229 Zahira Yaakob Ahmed Bshish Ali Ebshish Siti Tasirin Fatah Alhasan http://www.mdpi.com/1996-1944/6/6/2218 Copolymers, consisting of isothianaphthene and phenylene derivatives with liquid crystal groups, were synthesized via Migita-Kosugi-Stille polycondensation reaction. IR absorption, UV-vis optical absorption, and PL spectroscopy measurements were carried out. Thermotropic liquid crystallinity of the polymers with bandgap of ~2.5 eV was confirmed. Materials 2013-05-30 6 6 Communication 10.3390/ma6062218 2218 2228 1996-1944 2013-05-30 doi: 10.3390/ma6062218 Aohan Wang Kohsuke Kawabata Hiromasa Goto http://www.mdpi.com/1996-1944/6/6/2182 Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair may be required. However, these repair works raise the life-cycle cost of concrete as they are labor intensive and because the structure becomes in disuse during repair. In 1994, C. Dry was the first who proposed the intentional introduction of self-healing properties in concrete. In the following years, several researchers started to investigate this topic. The goal of this review is to provide an in-depth comparison of the different self-healing approaches which are available today. Among these approaches, some are aimed at improving the natural mechanism of autogenous crack healing, while others are aimed at modifying concrete by embedding capsules with suitable healing agents so that cracks heal in a completely autonomous way after they appear. In this review, special attention is paid to the types of healing agents and capsules used. In addition, the various methodologies have been evaluated based on the trigger mechanism used and attention has been paid to the properties regained due to self-healing. Materials 2013-05-27 6 6 Review 10.3390/ma6062182 2182 2217 1996-1944 2013-05-27 doi: 10.3390/ma6062182 Kim Van Tittelboom Nele De Belie http://www.mdpi.com/1996-1944/6/6/2155 The demand for transparent conductors is expected to grow rapidly as electronic devices, such as touch screens, displays, solid state lighting and photovoltaics become ubiquitous in our lives. Doped metal oxides, especially indium tin oxide, are the commonly used materials for transparent conductors. As there are some drawbacks to this class of materials, exploration of alternative materials has been conducted. There is an interest in films of carbon nanomaterials such as, carbon nanotubes and graphene as they exhibit outstanding properties. This article reviews the synthesis and assembly of these films and their post-treatment. These processes determine the film performance and understanding of this platform will be useful for future work to improve the film performance. Materials 2013-05-27 6 6 Review 10.3390/ma6062155 2155 2181 1996-1944 2013-05-27 doi: 10.3390/ma6062155 Xinning Ho Jun Wei http://www.mdpi.com/1996-1944/6/6/2143 The manufacture of medical and aerospace components made of titanium alloys and other difficult-to-cut materials requires the parallel development of high performance cutting tools coated with materials capable of enhanced tribological and resistance properties. In this matter, a thin nanocomposite film made out of AlCrN (aluminum–chromium–nitride) was studied in this research, showing experimental work in the deposition process and its characterization. A heat-treated monolayer coating, competitive with other coatings in the machining of titanium alloys, was analyzed. Different analysis and characterizations were performed on the manufactured coating by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDXS), and X-ray diffraction (XRD). Furthermore, the mechanical behavior of the coating was evaluated through hardness test and tribology with pin-on-disk to quantify friction coefficient and wear rate. Finally, machinability tests using coated tungsten carbide cutting tools were executed in order to determine its performance through wear resistance, which is a key issue of cutting tools in high-end cutting at elevated temperatures. It was demonstrated that the specimen (with lower friction coefficient than previous research) is more efficient in machinability tests in Ti6Al4V alloys. Furthermore, the heat-treated monolayer coating presented better performance in comparison with a conventional monolayer of AlCrN coating. Materials 2013-05-24 6 6 Article 10.3390/ma6062143 2143 2154 1996-1944 2013-05-24 doi: 10.3390/ma6062143 Natalia Cadena Rodrigo Cue-Sampedro Héctor Siller Ana Arizmendi-Morquecho Carlos Rivera-Solorio Santiago Di-Nardo http://www.mdpi.com/1996-1944/6/6/2130 The misfit dislocations and strain fields at a Ge/Si heterostructure interface were investigated experimentally using a combination of high-resolution transmission electron microscopy and quantitative electron micrograph analysis methods. The type of misfit dislocation at the interface was determined to be 60° dislocation and 90° full-edge dislocation. The full-field strains at the Ge/Si heterostructure interface were mapped by using the geometric phase analysis (GPA) and peak pairs analysis (PPA), respectively. The effect of the mask size on the GPA and PPA results was analyzed in detail. For comparison, the theoretical strain fields of the misfit dislocations were also calculated by the Peierls-Nabarro and Foreman dislocation models. The results showed that the optimal mask sizes in GPA and PPA were approximately three tenths and one-tenth of the reciprocal lattice vector, respectively. The Foreman dislocation model with an alterable factor a = 4 can best describe the strain field of the misfit dislocation at the Ge/Si heterostructure interface. Materials 2013-05-24 6 6 Article 10.3390/ma6062130 2130 2142 1996-1944 2013-05-24 doi: 10.3390/ma6062130 Jijun Li Chunwang Zhao Yongming Xing Shaojian Su Buwen Cheng http://www.mdpi.com/1996-1944/6/6/2119 We fabricated hybrid films of pentaerythritol triacrylate (PETA) with core–shell ceria/poly(vinylpyrrolidone) (PVP) nanoparticles, which consist of cerium oxide as the core and PVP as the shell, and investigated the film optical properties. In this study, we used ceria/PVP nanoparticles with average diameters of 37, 49 and 91 nm. We obtained translucent films consisting of PETA with core–shell ceria/PVP nanoparticles. The core–shell ceria/PVP nanoparticles can reduce the transmittance of near-ultraviolet light. The transmittance of visible light and haze values depends not only on the thickness of the films, but also on the average diameter of the nanoparticles. A SEM observation and the optical analyses prove that the core–shell ceria/PVP nanoparticles do not aggregate into the PETA matrix. Materials 2013-05-24 6 6 Article 10.3390/ma6062119 2119 2129 1996-1944 2013-05-24 doi: 10.3390/ma6062119 Toshio Itoh Toshio Uchida Noriya Izu Ichiro Matsubara Woosuck Shin http://www.mdpi.com/1996-1944/6/5/2103 Ce-modified mesoporous silica materials MCM-41 and SBA-15, namely 32 wt % Ce–Si–MCM-41, 16 wt % Ce–H–MCM-41 and 20 wt % Ce–Si–SBA-15, were prepared, characterized and studied in the selective preparation of trans-carveol by α-pinene oxide isomerization. The characterizations of these catalysts were performed using scanning electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and FTIR pyridine adsorption. Selective preparation of trans-carveol was carried out in the liquid phase in a batch reactor. The activity and the selectivity of catalyst were observed to be influenced by their acidity, basicity and morphology of the mesoporous materials. The formation of trans-carveol is moreover strongly influenced by the basicity of the used solvent and in order to achieve high yields of this desired alcohol it is necessary to use polar basic solvent. Materials 2013-05-17 6 5 Article 10.3390/ma6052103 2103 2118 1996-1944 2013-05-17 doi: 10.3390/ma6052103 Martina Stekrova Narendra Kumar Päivi Mäki-Arvela Oleg Ardashov Konstantin Volcho Nariman Salakhutdinov Dmitry Murzin http://www.mdpi.com/1996-1944/6/5/2090 Alumina-zirconia (AZ) composites are attractive structural materials, which combine the high hardness and Young’s modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In this study, AZ composites containing different amounts of zirconia (in the range 5–20 vol %) were prepared by a wet chemical method, consisting on the surface coating of alumina powders by mixing them with zirconium salt aqueous solutions. After spray-drying, powders were calcined at 600 °C for 1 h. Green bodies were then prepared by two methods: uniaxial pressing of spray-dried granules and slip casting of slurries, obtained by re-dispersing the spray dried granulates. After pressureless sintering at 1500 °C for 1 h, the slip cast samples gave rise to fully dense materials, characterized by a quite homogeneous distribution of ZrO2 grains in the alumina matrix. The microstructure, phase composition, tetragonal to monoclinic transformation behavior and mechanical properties were investigated and are here discussed as a function of the ZrO2 content. The material containing 10 vol % ZrO2 presented a relevant hardness and exhibited the maximum value of KI0, mainly imputable to the t → m transformation at the crack tip. Materials 2013-05-16 6 5 Article 10.3390/ma6052090 2090 2102 1996-1944 2013-05-16 doi: 10.3390/ma6052090 Valentina Naglieri Paola Palmero Laura Montanaro Jérôme Chevalier http://www.mdpi.com/1996-1944/6/5/2074 South African fly ash has been shown to be a useful feedstock for the synthesis of some zeolites. The present study focuses on the effect of impeller design and agitation rates on the synthesis of zeolite Na-P1 which are critical to the commercialization of this product. The effects of three impeller designs (4-flat blade, Anchor and Archimedes screw impellers) and three agitation speeds (150, 200 and 300 rpm) were investigated using a modified previously reported synthesis conditions; 48 hours of ageing at 47 °C and static hydrothermal treatment at 140 °C for 48 hours. The experimental results demonstrated that the phase purity of zeolite Na-P1 was strongly affected by the agitation rate and the type of impeller used during the ageing step of the synthesis process. Although zeolite Na-P1 was synthesized with a space time yield (STY) of 15 ± 0.4 kg d−1m−3and a product yield of 0.98±0.05 g zeolites/g fly ash for each impeller at different agitation speeds, zeolite formation was assessed to be fairly unsuccessful in some cases due the occurrence of undissolved mullite and/or the formation of impurities such as hydroxysodalite with the zeolitic product. This study also showed that a high crystalline zeolite Na-P1 can be synthesized from South African coal fly ash using a 4-flat blade impeller at an agitation rate of 200 rpm during the ageing step at 47 °C for 48 hours followed by static hydrothermal treatment at 140 °C for 48 hours. Materials 2013-05-16 6 5 Article 10.3390/ma6052074 2074 2089 1996-1944 2013-05-16 doi: 10.3390/ma6052074 Dakalo Mainganye Tunde Ojumu Leslie Petrik http://www.mdpi.com/1996-1944/6/5/2059 e effects of biological pretreatment on the rubberwood (Hevea brasiliensis), was evaluated after cultivation of white rot fungi Ceriporiopsis subvermispora, Trametes versicolor, and a mixed culture of C. subvermispora and T. versicolor. The analysis of chemical compositions indicated that C. subvermispora had greater selectivity for lignin degradation with the highest lignin and hemicellulose loss at 45.06% and 42.08%, respectively, and lowest cellulose loss (9.50%) after 90 days among the tested samples. X-ray analysis showed that pretreated samples had a higher crystallinity than untreated samples. The sample pretreated by C. subvermispora presented the highest crystallinity of all the samples which might be caused by the selective degradation of amorphous components. Fourier transform infrared (FT-IR) spectroscopy demonstrated that the content of lignin and hemicellulose decreased during the biological pretreatment process. A study on hydrolysis of rubberwood treated with C. subvermispora, T. versicolor, and mixed culture for 90 days resulted in an increased sugar yield of about 27.67%, 16.23%, and 14.20%, respectively, as compared with untreated rubberwood (2.88%). The results obtained demonstrate that rubberwood is a potential raw material for industrial applications and white rot fungus C. subevermispora provides an effective method for improving the enzymatic hydrolysis of rubberwood. Materials 2013-05-15 6 5 Article 10.3390/ma6052059 2059 2073 1996-1944 2013-05-15 doi: 10.3390/ma6052059 Forough Nazarpour Dzulkefly Abdullah Norhafizah Abdullah Reza Zamiri http://www.mdpi.com/1996-1944/6/5/2043 High-grade cellulose (97% α-cellulose content) of 48% crystallinity index was extracted from the renewable marine biomass waste Posidonia oceanica using H2O2 and organic peracids following an environmentally friendly and chlorine-free process. This cellulose appeared as a new high-grade cellulose of waste origin quite similar to the high-grade cellulose extracted from more noble starting materials like wood and cotton linters. The benefits of α-cellulose recovery from P. oceanica were enhanced by its transformation into cellulose acetate CA and cellulose derivative GMA-C. Fully acetylated CA was prepared by conventional acetylation method and easily transformed into a transparent film. GMA-C with a molar substitution (MS) of 0.72 was produced by quenching Fenton’s reagent (H2O2/FeSO4) generated cellulose radicals with GMA. GMA grafting endowed high-grade cellulose from Posidonia with adsorption capability. GMA-C removes β-naphthol from water with an efficiency of 47%, as measured by UV-Vis spectroscopy. After hydrolysis of the glycidyl group to glycerol group, the modified GMA-C was able to remove p-nitrophenol from water with an efficiency of 92%, as measured by UV-Vis spectroscopy. α-cellulose and GMA-Cs from Posidonia waste can be considered as new materials of potential industrial and environmental interest. Materials 2013-05-15 6 5 Article 10.3390/ma6052043 2043 2058 1996-1944 2013-05-15 doi: 10.3390/ma6052043 Alessia Coletti Antonio Valerio Elena Vismara http://www.mdpi.com/1996-1944/6/5/2026 Doxorubicin hydrochloride (DOX) is an effective anticancer agent for leukemia chemotherapy, although its clinical use has been limited because of its side effects such as cardiotoxicity, alopecia, vomiting, and leucopenia. Attention has been focussed on developing new drug carriers with high adsorption capacity and rapid adsorption rate in order to minimize the side effects of DOX. Graphene oxide (GO), a new type of nanomaterial in the carbon family, was prepared by Hummers method and used as adsorbent for DOX from aqueous solution. The physico-chemical properties of GO were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), zeta potential, and element analysis. The adsorption properties of DOX on GO were studied as a function of contact time, adsorbent dosage, temperature and pH value. The results showed that GO had a maximum adsorption capacity of 1428.57 mg/g and the adsorption isotherm data fitted the Langmuir model. The kinetics of adsorption fits a pseudo-second-order model. The thermodynamic studies indicate that the adsorption of DOX on GO is spontaneous and endothermic in nature. Materials 2013-05-15 6 5 Article 10.3390/ma6052026 2026 2042 1996-1944 2013-05-15 doi: 10.3390/ma6052026 Shaoling Wu Xindong Zhao Yanhui Li Qiuju Du Jiankun Sun Yonghao Wang Xin Wang Yanzhi Xia Zonghua Wang Linhua Xia http://www.mdpi.com/1996-1944/6/5/2007 Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) are well established surface techniques that provide both elemental and organic information from several monolayers of a sample surface, while also allowing depth profiling or image mapping to be carried out. The static TOF-SIMS with improved performances has expanded the application of TOF-SIMS to the study of a variety of organic, polymeric and biological materials. In this work, TOF-SIMS, XPS and Fourier Transform Infrared (FTIR) measurements were used to characterize commercial natural dyes and traditional silk fabric dyed with plant extracts dyes avoiding the time-consuming and destructive extraction procedures necessary for the spectrophotometric and chromatographic methods previously used. Silk textiles dyed with plant extracts were then analyzed for chemical and functional group identification of their dye components and mordants. TOF-SIMS spectra for the dyed silk fabric showed element ions from metallic mordants, specific fragment ions and molecular ions from plant-extracted dyes. The results of TOF-SIMS, XPS and FTIR are very useful as a reference database for comparison with data about traditional Korean silk fabric and to provide an understanding of traditional dyeing materials. Therefore, this study shows that surface techniques are useful for micro-destructive analysis of plant-extracted dyes and Korean dyed silk fabric. Materials 2013-05-15 6 5 Article 10.3390/ma6052007 2007 2025 1996-1944 2013-05-15 doi: 10.3390/ma6052007 Jihye Lee Min Kang Kang-Bong Lee Yeonhee Lee http://www.mdpi.com/1996-1944/6/5/1994 In this study, we first investigated changes seen in electrical and optical properties of a polymer light-emitting diode due to using different kinds of solvents and their mixture. Two-layer light emitting diodes with organic small molecules doped in a PVK polymer host were fabricated using (i) non-aromatic solvent chloroform with a high evaporation rate; (ii) aromatic solvent chlorobenzene with a low evaporation rate, and (iii) their mixture with different relative ratios. The effect of nano-scale layer thickness, surface roughness and internal nano-morphology on threshold voltage and the amount of electric current, the luminance and efficiency of a device were assessed. Results indicated the importance of majority charge carriers’ type in the selection of solvent and tuning its properties. Then, the effect of thermal annealing on electrical and optical properties of polymer light emitting diodes was investigated. During the device fabrication, pre-annealing in 80 and/or 120 °C and post-annealing in 120 °C were performed. The nano-scale effect of annealing on polymer-metal interface and electric current injection was described thoroughly. A comparison between threshold voltage, luminance and electric current efficiency of luminescence for different annealing processes was undertaken, so that the best electric current efficiency of luminescence achieved at 120 °C pre-annealing accompanied with 120 °C post-annealing. Materials 2013-05-15 6 5 Article 10.3390/ma6051994 1994 2006 1996-1944 2013-05-15 doi: 10.3390/ma6051994 Mohammad Rezvani Farid Farajollahi Alireza Nikfarjam Parisa Bakhtiarpour Erfan Saydanzad http://www.mdpi.com/1996-1944/6/5/1980 This work aims at studying the effect of the milling conditions on the microstructure and mechanical properties of a ZrB2-5 vol% Si3N4 matrix reinforced with chopped Hi-Nicalon SiC fibers. Several composites were obtained using different milling conditions in terms of time, speed and type of milling media. The composites were prepared from commercial powders, ball milled, dried and shaped, and hot pressed at 1720 °C. Their relative bulk densities achieved values as high as 99%. For each material the fiber length distribution, the extent of reacted fiber area and matrix mean grain size were evaluated in order to ascertain the effects of milling time, milling speed and type of milling media. While the fracture toughness and hardness were statistically the same independently of the milling conditions, the flexural strength changed. From the results obtained, the best milling conditions for optimized mechanical properties were determined. Materials 2013-05-15 6 5 Article 10.3390/ma6051980 1980 1993 1996-1944 2013-05-15 doi: 10.3390/ma6051980 L. Pienti D. Sciti L. Silvestroni S. Guicciardi http://www.mdpi.com/1996-1944/6/5/1967 The unique properties of ceramic foams enable their use in a variety of applications. This work investigated the effects of different parameters on the production of zirconia ceramic foam using the sol-gel process associated with liquid foam templates. Evaluation was made of the influence of the thermal treatment temperature on the porous and crystalline characteristics of foams manufactured using different amounts of sodium dodecylsulfate (SDS) surfactant. A maximum pore volume, with high porosity (94%) and a bimodal pore size distribution, was observed for the ceramic foam produced with 10% SDS. Macropores, with an average size of around 30 μm, were obtained irrespective of the SDS amount, while the average size of the supermesopores increased systematically as the SDS amount was increased up to 10%, after which it decreased. X-ray diffraction analyses showed that the sample treated at 500 °C was amorphous, while crystallization into a tetragonal metastable phase occurred at 600 °C due to the presence of sulfate groups in the zirconia structure. At 800 and 1000 °C the monoclinic phase was observed, which is thermodynamically stable at these temperatures. Materials 2013-05-10 6 5 Article 10.3390/ma6051967 1967 1979 1996-1944 2013-05-10 doi: 10.3390/ma6051967 Cristiane Beozzo Marinalva Alves-Rosa Sandra Pulcinelli Celso Santilli http://www.mdpi.com/1996-1944/6/5/1956 Bacterial cellulose (BC) is characterized for its high water holding capacity, high crystallinity, an ultrafine fiber network and high tensile strength. This work demonstrates the production of a new interpenetrated polymer network nanocomposite obtained through the incorporation of poly(vinyl alcohol) (PVA) on the BC matrix and evaluates the effect of oven drying on the morphological, mechanical and mass transfer properties of the composite membranes. Both the addition of PVA and oven drying induce the appearance of larger pores (circa 1–3 µm in average diameter) in dried BC/PVA membranes. Both types of treatments also affect the permeability of the composite, as assessed by the diffusion coefficients of polyethylene glycol (PEG) molecules (900, 8,000, 35,000 and 100,000 Da) across the membranes. Finally, the Young’s modulus of dry pristine BC decreases following PVA incorporation, resulting in a change from 3.5 GPa to 1 GPa and a five-fold loss in tensile strength. Materials 2013-05-10 6 5 Article 10.3390/ma6051956 1956 1966 1996-1944 2013-05-10 doi: 10.3390/ma6051956 Alexandre Leitão João Silva Fernando Dourado Miguel Gama http://www.mdpi.com/1996-1944/6/5/1940 In this study, magnesium composites with nano-size boron nitride (BN) particulates of varying contents were synthesized using the powder metallurgy (PM) technique incorporating microwave-assisted two-directional sintering followed by hot extrusion. The effect of nano-BN addition on the microstructural and the mechanical behavior of the developed Mg/BN composites were studied in comparison with pure Mg using the structure-property correlation. Microstructural characterization revealed uniform distribution of nano-BN particulates and marginal grain refinement. The coefficient of thermal expansion (CTE) value of the magnesium matrix was improved with the addition of nano-sized BN particulates. The results of XRD studies indicate basal texture weakening with an increase in nano-BN addition. The composites showed improved mechanical properties measured under micro-indentation, tension and compression loading. While the tensile yield strength improvement was marginal, a significant increase in compressive yield strength was observed. This resulted in the reduction of tension-compression yield asymmetry and can be attributed to the weakening of the strong basal texture. Materials 2013-05-10 6 5 Article 10.3390/ma6051940 1940 1955 1996-1944 2013-05-10 doi: 10.3390/ma6051940 Sankaranarayanan Seetharaman Jayalakshmi Subramanian Khin Tun Abdelmagid Hamouda Manoj Gupta http://www.mdpi.com/1996-1944/6/5/1920 In this study the development of a metakaolin based geopolymeric mortar to be used as bonding matrix for external strengthening of reinforced concrete beams is reported. Four geopolymer formulations have been obtained by varying the composition of the activating solution in terms of SiO2/Na2O ratio. The obtained samples have been characterized from a structural, microstructural and mechanical point of view. The differences in structure and microstructure have been correlated to the mechanical properties. A major issue of drying shrinkage has been encountered in the high Si/Al ratio samples. In the light of the characterization results, the optimal geopolymer composition was then applied to fasten steel fibers to reinforced concrete beams. The mechanical behavior of the strengthened reinforced beams was evaluated by four-points bending tests, which were performed also on reinforced concrete beams as they are for comparison. The preliminary results of the bending tests point out an excellent behavior of the geopolymeric mixture tested, with the failure load of the reinforced beams roughly twice that of the control beam. Materials 2013-05-10 6 5 Article 10.3390/ma6051920 1920 1939 1996-1944 2013-05-10 doi: 10.3390/ma6051920 Claudio Ferone Francesco Colangelo Giuseppina Roviello Domenico Asprone Costantino Menna Alberto Balsamo Andrea Prota Raffaele Cioffi Gaetano Manfredi http://www.mdpi.com/1996-1944/6/5/1903 TiB2-based ceramic matrix composites (CMCs) were fabricated using elemental powders of Ti, B and C. The self-propagating high temperature synthesis (SHS) was carried out for the highly exothermic “in situ” reaction of TiB2 formation and the “tailing” synthesis of boron carbide characterized by weak exothermicity. Two series of samples were fabricated, one of them being prepared with additional milling of raw materials. The effects of TiB2 vol fraction as well as grain size of reactant were investigated. The results revealed that combustion was not successful for a TiB2:B4C molar ratio of 0.96, which corresponds to 40 vol% of TiB2 in the composite, however the SHS reaction was initiated and self-propagated for the intended TiB2:B4C molar ratio of 2.16 or above. Finally B13C2 was formed as the matrix phase in each composite. Significant importance of the grain size of the C precursor with regard to the reaction completeness, which affected the microstructure homogeneity and hardness of investigated composites, was proved in this study. The grain size of Ti powder did not influence the microstructure of TiB2 grains. The best properties (HV = 25.5 GPa, average grain size of 9 μm and homogenous microstructure), were obtained for material containing 80 vol% of TiB2, fabricated using a graphite precursor of 2 μm. Materials 2013-05-10 6 5 Article 10.3390/ma6051903 1903 1919 1996-1944 2013-05-10 doi: 10.3390/ma6051903 Marta Ziemnicka-Sylwester http://www.mdpi.com/1996-1944/6/5/1891 Metal-containing mesoporous starches have been synthesized using a simple and efficient microwave-assisted methodology followed by metal impregnation in the porous gel network. Final materials exhibited surface areas >60 m2 g−1, being essentially mesoporous with pore sizes in the 10–15 nm range with some developed inter-particular mesoporosity. These materials characterized by several techniques including XRD, SEM, TG/DTA and DRIFTs may find promising catalytic applications due to the presence of (hydr)oxides in their composition. Materials 2013-05-10 6 5 Article 10.3390/ma6051891 1891 1902 1996-1944 2013-05-10 doi: 10.3390/ma6051891 Manuel Ojeda Vitaliy Budarin Peter Shuttleworth James Clark Antonio Pineda Alina Balu Antonio Romero Rafael Luque http://www.mdpi.com/1996-1944/6/5/1873 Plastic worm wheel is widely used in the vehicle manufacturing field because it is favorable for weight lightening, vibration and noise reduction, as well as corrosion resistance. However, it is very difficult for general plastics to secure the mechanical properties that are required for vehicle gears. If the plastic resin is reinforced by glass fiber in the fabrication process of plastic worm wheel, it is possible to achieve the mechanical properties of metallic material levels. In this study, the mechanical characteristic analysis of the glass-reinforced plastic worm wheel, according to the contents of glass fiber, is performed by analytic and experimental methods. In the case of the glass fiber-reinforced resin, the orientation and contents of glass fibers can influence the mechanical properties. For the characteristic prediction of plastic worm wheel, computer-aided engineering (CAE) analysis processes such as structural and injection molding analysis were executed with the polyamide resin reinforcement glass fiber (25 wt %, 50 wt %). The injection mold for fabricating the prototype plastic worm wheel was designed and made to reflect the CAE analysis results. Finally, the durability of prototype plastic worm wheel fabricated by the injection molding process was evaluated by the experimental method and the characteristics according to the glass fiber contents. Materials 2013-05-10 6 5 Article 10.3390/ma6051873 1873 1890 1996-1944 2013-05-10 doi: 10.3390/ma6051873 Gun-Hee Kim Jeong-Won Lee Tae-Il Seo http://www.mdpi.com/1996-1944/6/5/1851 Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing reinforcing steel corrosion. This study investigates the effects of leaching behavior of calcium ions on the compression and durability of cement-based materials. Since the parameters influencing the leaching behavior of cement-based materials are unclear and diverse, this paper focuses on the influence of added mineral admixtures (fly ash, slag and silica fume) on the leaching behavior of calcium ions regarding compression and durability of cemented-based materials. Ammonium nitrate solution was used to accelerate the leaching process in this study. Scanning electron microscopy, X-ray diffraction analysis, and thermogravimetric analysis were employed to analyze and compare the cement-based material compositions prior to and after calcium ion leaching. The experimental results show that the mineral admixtures reduce calcium hydroxide quantity and refine pore structure through pozzolanic reaction, thus enhancing the compressive strength and durability of cement-based materials. Materials 2013-05-07 6 5 Article 10.3390/ma6051851 1851 1872 1996-1944 2013-05-07 doi: 10.3390/ma6051851 An Cheng Sao-Jeng Chao Wei-Ting Lin http://www.mdpi.com/1996-1944/6/5/1840 The surface of a glassy carbon (GC) electrode was modified with reduced graphene oxide (rGO) to evaluate the electrochemical response of the modified GC electrodes to hydrogen peroxide (H2O2) and hydrazine. The electrode potential of the GC electrode was repeatedly scanned from −1.5 to 0.6 V in an aqueous dispersion of graphene oxide (GO) to deposit rGO on the surface of the GC electrode. The surface morphology of the modified GC electrode was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM and AFM observations revealed that aggregated rGO was deposited on the GC electrode, forming a rather rough surface. The rGO-modified electrodes exhibited significantly higher responses in redox reactions of H2O2 as compared with the response of an unmodified GC electrode. In addition, the electrocatalytic activity of the rGO-modified electrode to hydrazine oxidation was also higher than that of the unmodified GC electrode. The response of the rGO-modified electrode was rationalized based on the higher catalytic activity of rGO to the redox reactions of H2O2 and hydrazine. The results suggest that rGO-modified electrodes are useful for constructing electrochemical sensors. Materials 2013-05-07 6 5 Communication 10.3390/ma6051840 1840 1850 1996-1944 2013-05-07 doi: 10.3390/ma6051840 Shigehiro Takahashi Naoyuki Abiko Jun-ichi Anzai http://www.mdpi.com/1996-1944/6/5/1826 In the present study, room temperature mechanical properties of pure magnesium, Mg/ZrO2 and Mg/(ZrO2 + Cu) composites with various compositions are investigated. Results revealed that the use of hybrid (ZrO2 + Cu) reinforcements in Mg led to enhanced mechanical properties when compared to that of single reinforcement (ZrO2). Marginal reduction in mechanical properties of Mg/ZrO2 composites were observed mainly due to clustering of ZrO2 particles in Mg matrix and lack of matrix grain refinement. Addition of hybrid reinforcements led to grain size reduction and uniform distribution of hybrid reinforcements, globally and locally, in the hybrid composites. Macro- and micro- hardness, tensile strengths and compressive strengths were all significantly increased in the hybrid composites. With respect to unreinforced magnesium, failure strain was almost unchanged under tensile loading while it was reduced under compressive loading for both Mg/ZrO2 and Mg/(ZrO2 + Cu) composites. Materials 2013-05-07 6 5 Article 10.3390/ma6051826 1826 1839 1996-1944 2013-05-07 doi: 10.3390/ma6051826 Khin Tun Wai Wong Quy Nguyen Manoj Gupta http://www.mdpi.com/1996-1944/6/5/1803 Fabricating industrial-scale photoreactive composite materials containing living cells, requires a deposition strategy that unifies colloid science and cell biology. Convective assembly can rapidly deposit suspended particles, including whole cells and waterborne latex polymer particles into thin (<10 µm thick), organized films with engineered adhesion, composition, thickness, and particle packing. These highly ordered composites can stabilize the diverse functions of photosynthetic cells for use as biophotoabsorbers, as artificial leaves for hydrogen or oxygen evolution, carbon dioxide assimilation, and add self-cleaning capabilities for releasing or digesting surface contaminants. This paper reviews the non-biological convective assembly literature, with an emphasis on how the method can be modified to deposit living cells starting from a batch process to its current state as a continuous process capable of fabricating larger multi-layer biocomposite coatings from diverse particle suspensions. Further development of this method will help solve the challenges of engineering multi-layered cellular photocomposite materials with high reactivity, stability, and robustness by clarifying how process, substrate, and particle parameters affect coating microstructure. We also describe how these methods can be used to selectively immobilize photosynthetic cells to create biomimetic leaves and compare these biocomposite coatings to other cellular encapsulation systems. Materials 2013-05-07 6 5 Review 10.3390/ma6051803 1803 1825 1996-1944 2013-05-07 doi: 10.3390/ma6051803 Jessica Jenkins Michael Flickinger Orlin Velev http://www.mdpi.com/1996-1944/6/5/1789 The dimensionless Niyama criterion was used to predict the formation of microporosity in nickel-based superalloy casting, which extended the model application from a simple plate casting to complex thin-wall superalloy casting. The physical characteristics of the superalloy were calculated by JMatPro software. The relation between the volume percentage of microporosity and the dimensionless Niyama values were constructed. Quantitative metallographic measurements of the microporosity of the practical thin-wall casting were carried out. The prediction agreed well with the experiment in general, except for some thick-wall sites in the casting. Materials 2013-05-07 6 5 Article 10.3390/ma6051789 1789 1802 1996-1944 2013-05-07 doi: 10.3390/ma6051789 Maodong Kang Haiyan Gao Jun Wang Lishibao Ling Baode Sun http://www.mdpi.com/1996-1944/6/5/1779 Novel structures of an near-infrared (NIR) tetraarylazadipyrromethene (aza-BODIPY) series have been prepared. We designed the core structure containing two amido groups at the para-position of the aromatic rings. The amido group was incorporated to secure insensitivity to pH and to ensure a bathochromic shift to the NIR region. Forty members of aza-BODIPY compounds were synthesized by substitution of the acetyl group with commercial amines on the alpha bromide. The physicochemical properties and photostability were investigated and the fluorescence emission maxima (745~755 nm) were found to be in the near infrared (NIR) range of fluorescence. Materials 2013-05-06 6 5 Communication 10.3390/ma6051779 1779 1788 1996-1944 2013-05-06 doi: 10.3390/ma6051779 Sung-Chan Lee Duanting Zhai Parag Mukherjee Young-Tae Chang http://www.mdpi.com/1996-1944/6/5/1767 Zeolite-geopolymer hybrid materials have been formed when kaolin was used as a starting material. Their characteristics are of interest because they can have a wide pore size distribution with micro- and meso-pores due to the zeolite and geopolymer, respectively. In this study, Zeolite-geopolymer hybrid bulk materials were fabricated using four kinds of kaolinitic clays (a halloysite and three kinds of kaolinite). The kaolinitic clays were first calcined at 700 °C for 3 h to transform into the amorphous aluminosilicate phases. Alkali-activation treatment of the metakaolin yielded bulk materials with different amounts and types of zeolite and different compressive strength. This study investigated the effects of the initial kaolinitic clays on the amount and types of zeolite in the resultant geopolymers as well as the strength of the bulk materials. The kaolinitic clays and their metakaolin were characterized by XRD analysis, chemical composition, crystallite size, 29Si and 27Al MAS NMR analysis, and specific surface area measurements. The correlation between the amount of zeolite formed and the compressive strength of the resultant hybrid bulk materials, previously reported by other researchers was not positively observed. In the studied systems, the effects of Si/Al and crystalline size were observed. When the atomic ratio of Si/Al in the starting kaolinitic clays increased, the compressive strength of the hybrid bulk materials increased. The crystallite size of the zeolite in the hybrid bulk materials increased with decreasing compressive strength of the hybrid bulk materials. Materials 2013-05-06 6 5 Article 10.3390/ma6051767 1767 1778 1996-1944 2013-05-06 doi: 10.3390/ma6051767 Hayami Takeda Shinobu Hashimoto Hiroaki Yokoyama Sawao Honda Yuji Iwamoto http://www.mdpi.com/1996-1944/6/5/1745 Interest in nanofibrillated cellulose (NFC) has increased notably over recent decades. This bio-based nanomaterial has been used essentially in bionanocomposites or in paper thanks to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. It is worth noting that chemical surface modification of this material can be a key factor to achieve a better compatibility with matrices. In order to increase the compatibility in different matrices or to add new functions, surface chemical modification of NFC appears to be the prior choice to conserve its intrinsic nanofibre properties. In this review, the authors have proposed for the first time an overview of all chemical grafting strategies used to date on nanofibrillated cellulose with focus on surface modification such as physical adsorption, molecular grafting or polymer grafting. Materials 2013-05-03 6 5 Review 10.3390/ma6051745 1745 1766 1996-1944 2013-05-03 doi: 10.3390/ma6051745 Karim Missoum Mohamed Belgacem Julien Bras http://www.mdpi.com/1996-1944/6/5/1730 The ablation and oxidation of ZrB2-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which was strongly dependent on the composition. Composites containing 10% SiC showed the highest surface temperature (>2300 °C) and underwent a marked degradation under both conditions. In contrast, composites with 30% SiC exhibited the lowest surface temperature (<2000 °C) and demonstrated excellent ablation resistance. The surface temperature of UHTCs in aerothermal testing was closely associated with the dynamic evolution of the surface and bulk oxide properties, especially for the change in chemical composition on the exposed surface, which was strongly dependent on the material composition and testing parameters (i.e., heat flux, enthalpy, pressure and test time), and in turn affected its oxidation performance. Materials 2013-04-29 6 5 Article 10.3390/ma6051730 1730 1744 1996-1944 2013-04-29 doi: 10.3390/ma6051730 Ping Hu Kaixuan Gui Yang Yang Shun Dong Xinghong Zhang http://www.mdpi.com/1996-1944/6/5/1718 MCM-41 was used as a support and, by using atomic layer deposition (ALD) in the liquid phase, a catalyst was prepared by consecutively loading titanium oxide and vanadium oxide to the support. This research analyzes the effect of the loading amount of vanadium oxide on the acidic characteristics and catalytic performance in the dehydration of butanol. The physical and chemical characteristics of the TiO2-V2O5/MCM-41 catalysts were analyzed using XRF, BET, NH3-TPD, XRD, Py-IR, and XPS. The dehydration reaction of butanol was performed in a fixed bed reactor. For the samples with vanadium oxide loaded to TiO2/MCM-41 sample using the liquid phase ALD method, it was possible to increase the loading amount until the amount of vanadium oxide reached 12.1 wt %. It was confirmed that the structural properties of the mesoporous silica were retained well after titanium oxide and vanadium loading. The NH3-TPD and Py-IR results indicated that weak acid sites were produced over the TiO2/MCM-41 samples, which is attributed to the generation of Lewis acid sites. The highest activity of the V2O5(12.1)-TiO2/MCM-41 catalyst in 2-butanol dehydration is ascribed to it having the highest number of Lewis acid sites, as well as the highest vanadium dispersion. Materials 2013-04-29 6 5 Article 10.3390/ma6051718 1718 1729 1996-1944 2013-04-29 doi: 10.3390/ma6051718 Hyeonhee Choi Jung-Hyun Bae Do Kim Young-Kwon Park Jong-Ki Jeon http://www.mdpi.com/1996-1944/6/5/1704 In this study, we report the light-emitting assistance effect of perylene on a polymer electrochemiluminescence (ECL) device using poly(3-octylthiophene-2,5-diyl) (P3OT). An ECL device is a liquid type self-luminous device with a simple structure, and can be fabricated by a relatively easy procedure. Significant improvement in luminescence properties was confirmed when 1.0 wt % perylene was added to the ECL device using 3.0 wt % P3OT. Improvements of about 12 times of the maximum luminescence intensity and about 23 times of the light-emitting time ratio compared with that of a P3OT ECL device were obtained. We conclude that the light-emitting assistance of perylene is achieved by perylene radical ions shuttling electrons to P3OT while they are moving around in the emitting solution. The light-emitting assistance effect of perylene was also confirmed when poly(3-dodecylthiophene-2,5-diyl), which has almost identical electrochemical and photophysical characteristics to those of P3OT, was used instead of P3OT. Materials 2013-04-29 6 5 Article 10.3390/ma6051704 1704 1717 1996-1944 2013-04-29 doi: 10.3390/ma6051704 Tatsuya Daimon Eisuke Nihei http://www.mdpi.com/1996-1944/6/5/1688 Production of a high value zeolite from fly ash has been shown to be an avenue for the utilization of South African fly ash which presently constitutes a huge disposal problem. The synthesis of zeolites Na-P1 and analcime on a micro-scale has been successful and preliminary investigation shows that scale-up synthesis is promising. However, the post-synthesis supernatant waste generated contains high levels of NaOH that may constitute a secondary disposal problem. A waste minimization protocol was developed to reduce the volume of waste generated with a view to enhancing the feasibility of the scale synthesis. Series of experiments were conducted in 100 mL jacketed batch reactors. Fly ash was reacted with 5 Mol NaOH on a 1:1 mass basis during the aging step, followed by hydrothermal treatment in which ultrapure water was added to the slurry. This study shows that by re-introducing the supernatant waste into the experiments in such a way that it supplies the required reagent (NaOH) for the zeolite synthesis, zeolite Na-P1 and analcime can be synthesized. It also shows that the synthesis process can be altered to allow up to 100% re-use of the supernatant waste to yield high value zeolitic products. This study effectively constructed two protocols for the minimization of waste generated during the synthesis of zeolites from South African coal fly ash. This result could be used to establish a basis for legal and environmental aspects involved in the commission of a full-scale plant synthesizing zeolites NaP1 and analcime. Materials 2013-04-29 6 5 Article 10.3390/ma6051688 1688 1703 1996-1944 2013-04-29 doi: 10.3390/ma6051688 Pieter Plessis Tunde Ojumu Leslie Petrik http://www.mdpi.com/1996-1944/6/5/1656 LiFePO4 is considered to be one of the most promising cathode materials for lithium ion batteries for electric vehicle (EV) application. However, there are still a number of unsolved issues regarding the influence of Li and Fe-site substitution on the physicochemical properties of LiFePO4. This is a review-type article, presenting results of our group, related to the possibility of the chemical modification of phosphoolivine by introduction of cation dopants in Li and Fe sublattices. Along with a synthetic review of previous papers, a large number of new results are included. The possibility of substitution of Li+ by Al3+, Zr4+, W6+ and its influence on the physicochemical properties of LiFePO4 was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The range of solid solution formation in Li1−3xAlxFePO4, Li1−4xZrxFePO4 and Li1−6xWxFePO4 materials was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the chemical composition. The battery performance of selected olivines was tested by cyclic voltammetry (CV). In the case of LiFe1−yMyPO4 (M = Mn, Co and Ni), solid solution formation was observed over a large range of y (0 < y ≤ 1). An increase of electrical conductivity for the substitution level y = 0.25 was observed. Electrons of 3d metals other than iron do not contribute to the electrical properties of LiFe1−yMyPO4, and substitution level y > 0.25 leads to considerably lower values of σ. The activated character of electrical conductivity with a rather weak temperature dependence of the Seebeck coefficient suggests a small polaron-type conduction mechanism. The electrochemical properties of LiFe1−yMyPO4 strongly depend on the Fe substitution level. Materials 2013-04-29 6 5 Article 10.3390/ma6051656 1656 1687 1996-1944 2013-04-29 doi: 10.3390/ma6051656 Janina Molenda Andrzej Kulka Anna Milewska Wojciech Zając Konrad Świerczek http://www.mdpi.com/1996-1944/6/5/1632 Cell colonization of synthetic polymers can be regulated by physical and chemical modifications of the polymer surface. High-density and low-density polyethylene (HDPE and LDPE) were therefore activated with Ar+ plasma and grafted with fibronectin (Fn) or bovine serum albumin (BSA). The water drop contact angle usually decreased on the plasma-treated samples, due to the formation of oxidized groups, and this decrease was inversely related to the plasma exposure time (50–300 s). The presence of nitrogen and sulfur on the polymer surface, revealed by X-ray photoelectron spectroscopy (XPS), and also by immunofluorescence staining, showed that Fn and BSA were bound to this surface, particularly to HDPE. Plasma modification and grafting with Fn and BSA increased the nanoscale surface roughness of the polymer. This was mainly manifested on HDPE. Plasma treatment and grafting with Fn or BSA improved the adhesion and growth of vascular smooth muscle cells in a serum-supplemented medium. The final cell population densities on day 6 after seeding were on an average higher on LDPE than on HDPE. In a serum-free medium, BSA grafted to the polymer surface hampered cell adhesion. Thus, the cell behavior on polyethylene can be modulated by its type, intensity of plasma modification, grafting with biomolecules, and composition of the culture medium. Materials 2013-04-29 6 5 Article 10.3390/ma6051632 1632 1655 1996-1944 2013-04-29 doi: 10.3390/ma6051632 Katarina Novotna Marketa Bacakova Nikola Kasalkova Petr Slepicka Vera Lisa Vaclav Svorcik Lucie Bacakova http://www.mdpi.com/1996-1944/6/5/1621 Two structural forms of a ternary alloy PtRuIr/C catalyst, one amorphous and one highly crystalline, were synthesized and compared to determine the effect of their respective structures on their activity and stability as anodic catalysts in methanol oxidation. Characterization techniques included TEM, XRD, and EDX. Electrochemical analysis using a glassy carbon disk electrode for cyclic voltammogram and chronoamperometry were tested in a solution of 0.5 mol L−1 CH3OH and 0.5 mol L−1 H2SO4. Amorphous PtRuIr/C catalyst was found to have a larger electrochemical surface area, while the crystalline PtRuIr/C catalyst had both a higher activity in methanol oxidation and increased CO poisoning rate. Crystallinity of the active alloy nanoparticles has a big impact on both methanol oxidation activity and in the CO poisoning rate. Materials 2013-04-29 6 5 Article 10.3390/ma6051621 1621 1631 1996-1944 2013-04-29 doi: 10.3390/ma6051621 Yanjiao Ma Rongfang Wang Hui Wang Shijun Liao Julian Key Vladimir Linkov Shan Ji http://www.mdpi.com/1996-1944/6/5/1608 Microencapsulated paraffin wax/polyaniline was prepared using a simple in situ polymerization technique, and its performance characteristics were investigated. Weight losses of samples were determined by Thermal Gravimetry Analysis (TGA). The microencapsulated samples with 23% and 49% paraffin showed less decomposition after 330 °C than with higher percentage of paraffin. These samples were then subjected to a thermal cycling test. Thermal properties of microencapsulated paraffin wax were evaluated by Differential Scanning Calorimeter (DSC). Structure stability and compatibility of core and coating materials were also tested by Fourier transform infrared spectrophotometer (FTIR), and the surface morphology of the samples are shown by Field Emission Scanning Electron Microscopy (FESEM). It has been found that the microencapsulated paraffin waxes show little change in the latent heat of fusion and melting temperature after one thousand thermal recycles. Besides, the chemical characteristics and structural profile remained constant after one thousand thermal cycling tests. Therefore, microencapsulated paraffin wax/polyaniline is a stable material that can be used for thermal energy storage systems. Materials 2013-04-29 6 5 Article 10.3390/ma6051608 1608 1620 1996-1944 2013-04-29 doi: 10.3390/ma6051608 Mahyar Silakhori Mohammad Naghavi Hendrik Metselaar Teuku Mahlia Hadi Fauzi Mohammad Mehrali http://www.mdpi.com/1996-1944/6/5/1599 The biomedical properties of a porous bio-collagenic polymer extracted from leather industrial waste residues have been investigated in wound healing and tissue regeneration in induced wounds in rats. Application of the pure undiluted bio-collagen to induced wounds in rats dramatically improved its healing after 7 days in terms of collagen production and wound filling as well as in the migration and differentiation of keratinocytes. The formulation tested was found to be three times more effective than the commercial reference product Catrix® (Heal Progress (HP): 8 ± 1.55 vs. 2.33 ± 0.52, p < 0.001; Formation of Collagen (FC): 7.5 ± 1.05 vs. 2.17 ± 0.75, p < 0.001; Regeneration of Epidermis (RE): 13.33 ± 5.11 vs. 5 ± 5.48, p < 0.05). Materials 2013-04-29 6 5 Article 10.3390/ma6051599 1599 1607 1996-1944 2013-04-29 doi: 10.3390/ma6051599 Mercedes Catalina Jaume Cot Miquel Borras Joaquín Lapuente Javier González Alina Balu Rafael Luque http://www.mdpi.com/1996-1944/6/5/1584 The irradiation of pulp is of interest from different perspectives. Mainly it is required when a modification of cellulose is needed. Irradiation could bring many advantages, such as chemical savings and, therefore, cost savings and a reduction in environmental pollutants. In this account, pulp and dissociated celluloses were analyzed before and after irradiation by electron beaming. The focus of the analysis was the oxidation of hydroxyl groups to carbonyl and carboxyl groups in pulp and the degradation of cellulose causing a decrease in molar mass. For that purpose, the samples were labeled with a selective fluorescence marker and analyzed by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), refractive index (RI), and fluorescence detectors. Degradation of the analyzed substrates was the predominant result of the irradiation; however, in the microcrystalline samples, oxidized cellulose functionalities were introduced along the cellulose chain, making this substrate suitable for further chemical modification. Materials 2013-04-29 6 5 Article 10.3390/ma6051584 1584 1598 1996-1944 2013-04-29 doi: 10.3390/ma6051584 Ute Henniges Merima Hasani Antje Potthast Gunnar Westman Thomas Rosenau http://www.mdpi.com/1996-1944/6/5/1566 A wider utilization of ultra high temperature ceramics (UHTC) materials strongly depends on the availability of efficient techniques for their fabrication as dense bodies. Based on recent results reported in the literature, it is possible to state that Spark Plasma Sintering (SPS) technology offers a useful contribution in this direction. Along these lines, the use of two different SPS-based processing routes for the preparation of massive UHTCs is examined in this work. One method, the so-called reactive SPS (R-SPS), consists of the synthesis and densification of the material in a single step. Alternatively, the ceramic powders are first synthesized by Self-propagating High-temperature Synthesis (SHS) and then sintered by SPS. The obtained results evidenced that R-SPS method is preferable for the preparation of dense monolithic products, while the sintering of SHS powders requires relatively milder conditions when considering binary composites. The different kinetic mechanisms involved during R-SPS of the monolithic and composite systems, i.e., combustion-like or gradual solid-diffusion, respectively, provides a possible explanation. An important role is also played by the SHS process, particularly for the preparation of composite powders, since stronger interfaces are established between the ceramic constituents formed in situ, thus favoring diffusion processes during the subsequent SPS step. Materials 2013-04-29 6 5 Review 10.3390/ma6051566 1566 1583 1996-1944 2013-04-29 doi: 10.3390/ma6051566 Roberto Orrù Giacomo Cao http://www.mdpi.com/1996-1944/6/4/1554 Three periodic mesoporous materials, i.e., two organosilicas with either ethylene or phenylene bridges and one silica, have been used as supports for Pd nanoparticles. All Pd-supported samples (1.0 wt%) were prepared by the incipient wetness method and subsequently reduced in an H2 stream at 200 °C. Both hydrogen chemisorption and temperature programmed reduction experiments revealed significant differences depending on the support. Pd2+ species were more reducible on the mesoporous organosilicas than on their silica counterpart. Also, remarkable differences on the particle morphology were observed by transmission electron microscopy. All Pd-supported samples were active in the Suzuki cross-coupling reaction between bromobenzene and phenylboronic acid. Materials 2013-04-17 6 4 Article 10.3390/ma6041554 1554 1565 1996-1944 2013-04-17 doi: 10.3390/ma6041554 Jorge Corral María López Dolores Esquivel Manuel Mora César Jiménez-Sanchidrián Francisco Romero-Salguero http://www.mdpi.com/1996-1944/6/4/1543 We report a new method for growing hexagonal columnar nanograin structured silicon carbide (SiC) thin films on silicon substrates by using graphene–graphitic carbon nanoflakes (GGNs) templates from solid carbon sources. The growth was carried out in a conventional low pressure chemical vapor deposition system (LPCVD). The GGNs are small plates with lateral sizes of around 100 nm and overlap each other, and are made up of nanosized multilayer graphene and graphitic carbon matrix (GCM). Long and straight SiC nanograins with hexagonal shapes, and with lateral sizes of around 200–400 nm are synthesized on the GGNs, which form compact SiC thin films. Materials 2013-04-16 6 4 Article 10.3390/ma6041543 1543 1553 1996-1944 2013-04-16 doi: 10.3390/ma6041543 Xingfang Liu Guosheng Sun Bin Liu Guoguo Yan Min Guan Yang Zhang Feng Zhang Yu Chen Lin Dong Liu Zheng Shengbei Liu Lixin Tian Lei Wang Wanshun Zhao Yiping Zeng http://www.mdpi.com/1996-1944/6/4/1530 The novel complex photocatalytic material was prepared by coating TiO2 nanoparticles on tourmaline using the sol-gel method, and used in the degradation of the herbicide 2,4-D. The results indicated that coating TiO2 with tourmaline enhanced the photocatalytic activity significantly. Based on the research of a simplified model for the average light intensity in the photoreactor, the influence of the concentration of photocatalyst, and the initial concentration of 2,4-D, a model for the degradation of 2,4-D by the tourmaline-coated TiO2 nanoparticles was established. Further tests showed that results calculated from this model were close to those obtained in the actual experiments. Materials 2013-04-15 6 4 Article 10.3390/ma6041530 1530 1542 1996-1944 2013-04-15 doi: 10.3390/ma6041530 Xuesen Bian Jianqiu Chen Rong Ji http://www.mdpi.com/1996-1944/6/4/1520 A novel kind of α-Fe2O3-filled ordered mesoporous carbon nanorods has been synthesized by a facial hydrothermal method. Compared with dendritic α-Fe2O3 micropines, both a broader effective absorption range—from 10.5 GHz to 16.5 GHz with reflection loss (RL) less than −10 dB—and a thinner matching thickness of 2.0 mm have been achieved in the frequency range 2–18 GHz. The enhanced microwave absorption properties evaluated by the RL are attributed to the enhanced dielectric loss resulting from the intrinsic physical properties and special structures. Materials 2013-04-15 6 4 Article 10.3390/ma6041520 1520 1529 1996-1944 2013-04-15 doi: 10.3390/ma6041520 Yiming Wang Liuding Wang Hongjing Wu http://www.mdpi.com/1996-1944/6/4/1506 A series of new gemini surfactants without a spacer group, disodium 2,3-dialkyl-1,2,3,4-butanetetracarboxylates, were synthesized in a green chemistry context minimizing the use of organic solvents and applying microwaves (MW) when activation energy was required. Once the desired architecture was confirmed by means of the nuclear magnetic resonance technique (1H-NMR, 1H-1H COSY) for all the studied surfactants, the critical micellization concentration was determined by conductance measurements. The diffusion coefficient of micelles formed by the four compounds was characterized using pulsed field gradient (PFG)-NMR. Diffusion coefficients were found to be dependent on the concentration and on the number of carbon atoms in the alkyl chain. The absence of the spacer group, peculiar to this new series of gemini surfactants, may confer relatively low flexibility to the molecules, with potential implications on the interfacial properties, namely on micellization. These gemini surfactants might have interesting applications in the preparation of composite materials, in nanotechnology, in gene transfection and mainly, due to the low CMCs, as new interesting ingredients of cosmetics and toiletries. Materials 2013-04-12 6 4 Article 10.3390/ma6041506 1506 1519 1996-1944 2013-04-12 doi: 10.3390/ma6041506 Carla Villa Sara Baldassari Delia Martino Alberto Spinella Eugenio Caponetti http://www.mdpi.com/1996-1944/6/4/1496 Randomness and discreteness for appearance of pop-out of the single crystal silicon with a (100) orientation were studied by a self-made indentation device. For a given maximum penetration load, the load Ppo for appearance of pop-out fluctuates in a relatively large range, which makes it hard to study the effect of the loading/unloading rate on the load Ppo. Experimental results with different maximum penetration loads indicate that the critical penetration load for appearance of pop-out is in the range of 15 mN~20 mN for the current used single crystal silicon. For a given maximum penetration load, the load Ppo for appearance of pop-out seems random and discrete, but in the point of statistics, it has an obviously increasing trend with increase of the maximum penetration load and also the fraction Ppo/Pmax approximately keeps in the range of 0.2~0.5 for different maximum penetration loads changing from 15 mN to 150 mN. Materials 2013-04-12 6 4 Article 10.3390/ma6041496 1496 1505 1996-1944 2013-04-12 doi: 10.3390/ma6041496 Hu Huang Hongwei Zhao Chengli Shi Lin Zhang Shunguang Wan Chunyang Geng http://www.mdpi.com/1996-1944/6/4/1485 This paper presents workability, compressive strength and microstructure for geopolymer pastes and mortars made of class C fly ash at mass ratios of water-to-fly ash from 0.30 to 0.35. Fluidity was in the range of 145–173 mm for pastes and 131–136 mm for mortars. The highest strengths of paste and mortar were 58 MPa and 85 MPa when they were cured at 70 °C for 24 h. In XRD patterns, unreacted quartz and some reacted product were observed. SEM examination indicated that reacted product has formed and covered the unreacted particles in the paste and mortar that were consistent with their high strength. Materials 2013-04-09 6 4 Article 10.3390/ma6041485 1485 1495 1996-1944 2013-04-09 doi: 10.3390/ma6041485 Xueying Li Xinwei Ma Shoujie Zhang Enzu Zheng http://www.mdpi.com/1996-1944/6/4/1467 In this work, we prepared oriented mesoporous thin films of silica on various solid substrates using the pluronic block copolymer P123 as a template. We attempted to insert guest iron oxide (FexOy) nanoparticles into these films by two different methods: (a) by co-precipitation—where iron precursors are introduced in the synthesis sol before deposition of the silica film—and subsequent oxide production during the film calcination step; (b) by preparing and calcining the silica films first then impregnating them with the iron precursor, obtaining the iron oxide nanoparticles by a second calcination step. We have examined the structural effects of the guest nanoparticles on the silica film structures using grazing incidence X-ray scattering (GISAXS), high-resolution transmission electron spectroscopy (HRTEM), spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and Raman microscopy. Formation of nanoparticles by co-precipitation may induce substantial changes in the film structure leading, in our adopted process, to the appearance of lamellar ordering in the calcination stage. On the contrary, impregnation-based approaches perturb the film structures much more weakly, but are also less efficient in filling the pores with nanoparticles. Materials 2013-04-09 6 4 Article 10.3390/ma6041467 1467 1484 1996-1944 2013-04-09 doi: 10.3390/ma6041467 Ioanna Andreou Heinz Amenitsch Vlassis Likodimos Polycarpos Falaras Petros Koutsoukos Epameinondas Leontidis http://www.mdpi.com/1996-1944/6/4/1452 In the present work the dehydration process of layered solids with formula unit M(H2O)2[Ni(CN)4]·nH2O, M = Ni, Co, Mn; n = 1, 2, 4 is studied using modulated thermogravimetry. The results show that water molecules need to overcome an energetic barrier (activation energy between 63 and 500 kJ/mol) in order to diffuse through the interlayer region. The related kinetic parameters show a dependence on the water partial pressure. On the other hand, X-ray diffraction results provide evidence that the dehydration process is accompanied by framework collapse, limiting the structural reversibility, except for heating below 80 °C where the ordered structure remains. Removal of water molecules from the interlayer region disrupts the long-range structural order of the solid. Materials 2013-04-09 6 4 Article 10.3390/ma6041452 1452 1466 1996-1944 2013-04-09 doi: 10.3390/ma6041452 Omar Reyes-Martinez Enelio Torres-García Geonel Rodríguez-Gattorno Edilso Reguera http://www.mdpi.com/1996-1944/6/4/1434 Miniaturization encourages the development of new manufacturing processes capable of fabricating features, like micro-channels, in order to use them for different applications, such as in fuel cells, heat exchangers, microfluidic devices and micro-electromechanical systems (MEMS). Many studies have been conducted on heat and fluid transfer in micro-channels, and they appeared significantly deviated from conventional theory, due to measurement errors and fabrication methods. The present research, in order to deal with this opportunity, is focused on a set of experiments in the micro-milling of channels made of aluminum, titanium alloys and stainless steel, varying parameters, such as spindle speed, depth of cut per pass (ap), channel depth (d), feed per tooth (fz) and coolant application. The experimental results were analyzed in terms of dimensional error, channel profile shape deviation from rectangular and surface quality (burr and roughness). The micro-milling process was capable of offering quality features required on the micro-channeled devices. Critical phenomena, like run-out, ploughing, minimum chip thickness and tool wear, were encountered as an explanation for the deviations in shape and for the surface quality of the micro-channels. The application of coolant and a low depth of cut per pass were significant to obtain better superficial quality features and a smaller dimensional error. In conclusion, the integration of superficial and geometrical features on the study of the quality of micro-channeled devices made of different metallic materials contributes to the understanding of the impact of calibrated cutting conditions in MEMS applications. Materials 2013-04-03 6 4 Article 10.3390/ma6041434 1434 1451 1996-1944 2013-04-03 doi: 10.3390/ma6041434 Karla Monroy-Vázquez Aldo Attanasio Elisabetta Ceretti Héctor Siller Nicolás Hendrichs-Troeglen Claudio Giardini http://www.mdpi.com/1996-1944/6/4/1432 Due to an oversight by the authors, Table 4 in the aforementioned review article [1] should have been referred to as obtained from reference [2]: Khajavi, S. Separation of Process Water Using Hydroxy Sodalite Membranes. PhD Thesis, Delft University of Technology, Delft, The Netherlands, 2010. Furthermore, an additional affiliation for the first author of this review is added as follows: Catalysis Engineering Section, Delft University of Technology, Julianalaan 136, 2628 BL, Delft, The Netherlands The authors apologize for any inconvenience this may have caused. Materials 2013-04-02 6 4 Correction 10.3390/ma6041432 1432 1433 1996-1944 2013-04-02 doi: 10.3390/ma6041432 Michael Daramola Elizabeth Aransiola Tunde Ojumu http://www.mdpi.com/1996-1944/6/4/1420 2-(1-methyl-4-((E)-(2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-ylidene)-hydrazineecarbothioamide (HCB) was synthesized as a corrosion inhibitor from the reaction of 4-aminoantipyrine, thiosemicarbazide and 2-methylbenzaldehyde. The corrosion inhibitory effects of HCB on mild steel in 1.0 M HCl were investigated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The results showed that HCB inhibited mild steel corrosion in acidic solution and inhibition efficiency increased with an increase in the concentration of the inhibitor. The inhibition efficiency was up to 96.5% at 5.0 mM. Changes in the impedance parameters suggested that HCB adsorbed on the surface of mild steel, leading to the formation of a protective film. The novel corrosion inhibitor synthesized in the present study was characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectral data. Materials 2013-04-02 6 4 Article 10.3390/ma6041420 1420 1431 1996-1944 2013-04-02 doi: 10.3390/ma6041420 Ahmed Al-Amiery Abdul Kadhum Abu Mohamad Sutiana Junaedi http://www.mdpi.com/1996-1944/6/4/1403 Sorbent materials were developed utilizing two morphological structures, comprising either hexagonally packed pores (HX) or a disordered pore arrangement (CF). The sorbents were functionalized with combinations of two types of alkylammonium groups. When capture of perchlorate by the sorbents was compared, widely varying performance was noted as a result of differing morphology and/or functional group loading. A material providing improved selectivity for perchlorate over perrhenate was synthesized with a CF material using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride. Materials were applied in batch and column formats. Binding isotherms followed the behavior expected for a system in which univalent ligands of varying affinity compete for immobilized sites. Performance of the sorbents was also compared to that of commercial Purolite materials. Materials 2013-04-02 6 4 Article 10.3390/ma6041403 1403 1419 1996-1944 2013-04-02 doi: 10.3390/ma6041403 Brandy Johnson Iwona Leska Brian Melde Ronald Siefert Anthony Malanoski Martin Moore Jenna Taft Jeffrey Deschamps http://www.mdpi.com/1996-1944/6/4/1391 Chitosonic® Acid, carboxymethyl hexanoyl chitosan, is a novel chitosan material that has recently been accepted by the Personal Care Products Council as a new cosmetic ingredient with the INCI (International Nomenclature of Cosmetic Ingredients) name Carboxymethyl Caprooyl Chitosan. In this study, we analyze several important cosmetic characteristics of Chitosonic® Acid. Our results demonstrate that Chitosonic® Acid is a water-soluble chitosan derivative with a high HLB value. Chitosonic® Acid can form a nano-network structure when its concentration is higher than 0.5% and can self-assemble into a nanosphere structure when its concentration is lower than 0.2%. Chitosonic® Acid has potent antimicrobial activities against gram-positive bacteria, gram-negative bacteria and fungus. Chitosonic® Acid also has moderate DPPH radical scavenging activity. Additionally, Chitosonic® Acid exhibits good hydration activity for absorbing and retaining water molecules with its hydrophilic groups. From a safety point of view, Chitosonic® Acid has no cytotoxicity to L-929 cells if its concentration is less than 0.5%. Moreover, Chitosonic® Acid has good compatibilities with various normal cosmetic ingredients. Therefore, we propose that Chitosonic® Acid has the potential to be a widely used ingredient in various types of cosmetic products. Materials 2013-03-28 6 4 Article 10.3390/ma6041391 1391 1402 1996-1944 2013-03-28 doi: 10.3390/ma6041391 Shu-Mei Lee Kun-Ho Liu Yen-Yu Liu Yen-Po Chang Chih-Chien Lin Yi-Shyan Chen http://www.mdpi.com/1996-1944/6/4/1377 Cellulose micro/nano-fibers can be produced by electrospinning from liquid crystalline solutions. Scanning electron microscopy (SEM), as well as atomic force microscopy (AFM) and polarizing optical microscopy (POM) measurements showed that cellulose-based electrospun fibers can curl and twist, due to the presence of an off-core line defect disclination, which was present when the fibers were prepared. This permits the mimicking of the shapes found in many systems in the living world, e.g., the tendrils of climbing plants, three to four orders of magnitude larger. In this work, we address the mechanism that is behind the spirals’ and helices’ appearance by recording the trajectories of the fibers toward diverse electrospinning targets. The intrinsic curvature of the system occurs via asymmetric contraction of an internal disclination line, which generates different shrinkages of the material along the fiber. The completely different instabilities observed for isotropic and anisotropic electrospun solutions at the exit of the needle seem to corroborate the hypothesis that the intrinsic curvature of the material is acquired during liquid crystalline sample processing inside the needle. The existence of perversions, which joins left and right helices, is also investigated by using suspended, as well as flat, targets. Possible routes of application inspired from the living world are addressed. Materials 2013-03-28 6 4 Article 10.3390/ma6041377 1377 1390 1996-1944 2013-03-28 doi: 10.3390/ma6041377 João Canejo Maria Godinho http://www.mdpi.com/1996-1944/6/4/1360 In this study, the effect of preparation route of magnetic graphene oxide (mGO) on Reactive Black 5 (RB5) adsorption was investigated. The synthesis of mGO was achieved both with (i) impregnation method (mGOi nanoparticles), and (ii) co-precipitation (mGOp nanoparticles). After synthesis, the full characterization with various techniques (SEM, FTIR, XRD, DTA, DTG, VSM) was achieved revealing many possible interactions/forces of dye-composite system. Effects of initial solution pH, effect of temperature, adsorption isotherms and kinetics were investigated in order to conclude about the aforementioned effect of the preparation method on dye adsorption performance of the magnetic nanocomposites. The adsorption evaluation of the magnetic nanoparticles presented higher adsorption capacity of mGOp derivative (188 mg/g) and lower of mGOi (164 mg/g). Equilibrium experiments are also performed studying the effect of contact time (pseudo-first and -second order equations) and temperature (isotherms at 25, 45 and 65 °C fitted to Langmuir and Freundlich model). A full thermodynamic evaluation was carried out, calculating the parameters of enthalpy, free energy and entropy (ΔH0, ΔG0 and ΔS0). Materials 2013-03-28 6 4 Article 10.3390/ma6041360 1360 1376 1996-1944 2013-03-28 doi: 10.3390/ma6041360 George Kyzas Nikolina Travlou Orestis Kalogirou Eleni Deliyanni http://www.mdpi.com/1996-1944/6/4/1333 Nanotechnologists have become involved in regenerative medicine via creation of biomaterials and nanostructures with potential clinical implications. Their aim is to develop systems that can mimic, reinforce or even create in vivo tissue repair strategies. In fact, in the last decade, important advances in the field of tissue engineering, cell therapy and cell delivery have already been achieved. In this review, we will delve into the latest research advances and discuss whether cell and/or tissue repair devices are a possibility. Focusing on the application of nanotechnology in tissue engineering research, this review highlights recent advances in the application of nano-engineered scaffolds designed to replace or restore the followed tissues: (i) skin; (ii) cartilage; (iii) bone; (iv) nerve; and (v) cardiac. Materials 2013-03-28 6 4 Review 10.3390/ma6041333 1333 1359 1996-1944 2013-03-28 doi: 10.3390/ma6041333 Macarena Perán María García Elena Lopez-Ruiz Gema Jiménez Juan Marchal http://www.mdpi.com/1996-1944/6/4/1326 (TiZrHf)NiSn half-Heusler compounds were prepared by arc melting and their thermoelectric properties characterized in the temperature range between 325 K and 857 K, resulting in a Figure of Merit ZT ≈ 0.45. Furthermore, the prepared samples were used to construct a unileg module. This module was characterized in a homemade thermoelectric module measurement stand and yielded 275 mW/cm2 and a maximum volumetric power density of 700 mW/cm3. This was reached using normal silver paint as a contacting material; from an improved contacting, much higher power yields are to be expected. Materials 2013-03-27 6 4 Article 10.3390/ma6041326 1326 1332 1996-1944 2013-03-27 doi: 10.3390/ma6041326 Sascha Populoh Oliver Brunko Krzysztof Gałązka Wenjie Xie Anke Weidenkaff http://www.mdpi.com/1996-1944/6/4/1310 Degradation mechanisms such as lithium plating, growth of the passivated surface film layer on the electrodes and loss of both recyclable lithium ions and electrode material adversely affect the longevity of the lithium ion battery. The anode electrode is very vulnerable to these degradation mechanisms. In this paper, the most common aging mechanisms occurring at the anode during the operation of the lithium battery, as well as some approaches for minimizing the degradation are reviewed. Materials 2013-03-27 6 4 Review 10.3390/ma6041310 1310 1325 1996-1944 2013-03-27 doi: 10.3390/ma6041310 Victor Agubra Jeffrey Fergus http://www.mdpi.com/1996-1944/6/4/1285 Alginate is a natural polysaccharide exhibiting excellent biocompatibility and biodegradability, having many different applications in the field of biomedicine. Alginate is readily processable for applicable three-dimensional scaffolding materials such as hydrogels, microspheres, microcapsules, sponges, foams and fibers. Alginate-based biomaterials can be utilized as drug delivery systems and cell carriers for tissue engineering. Alginate can be easily modified via chemical and physical reactions to obtain derivatives having various structures, properties, functions and applications. Tuning the structure and properties such as biodegradability, mechanical strength, gelation property and cell affinity can be achieved through combination with other biomaterials, immobilization of specific ligands such as peptide and sugar molecules, and physical or chemical crosslinking. This review focuses on recent advances in the use of alginate and its derivatives in the field of biomedical applications, including wound healing, cartilage repair, bone regeneration and drug delivery, which have potential in tissue regeneration applications. Materials 2013-03-26 6 4 Review 10.3390/ma6041285 1285 1309 1996-1944 2013-03-26 doi: 10.3390/ma6041285 Jinchen Sun Huaping Tan http://www.mdpi.com/1996-1944/6/4/1270 More and more attention has been paid to environmentally friendly bio-based renewable materials as the substitution of fossil-based materials, due to the increasing environmental concerns. In this study, regenerated cellulose films with enhanced mechanical property were prepared via incorporating different plasticizers using ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as the solvent. The characteristics of the cellulose films were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis (TG), X-ray diffraction (XRD), 13C Solid-state cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and tensile testing. The results showed that the cellulose films exhibited a homogeneous and smooth surface structure. It was noted that the thermal stability of the regenerated cellulose film plasticized with glycerol was increased compared with other regenerated cellulose films. Furthermore, the incorporation of plasticizers dramatically strengthened the tensile strength and improved the hydrophobicity of cellulose films, as compared to the control sample. Therefore, these notable results exhibited the potential utilization in producing environmentally friendly cellulose films with high performance properties. Materials 2013-03-26 6 4 Article 10.3390/ma6041270 1270 1284 1996-1944 2013-03-26 doi: 10.3390/ma6041270 Jinhui Pang Xin Liu Xueming Zhang Yuying Wu Runcang Sun http://www.mdpi.com/1996-1944/6/4/1255 An ultrasensitive portable electrochemical immunosensor for human immunodeficiency virus p24 (HIV p24) antigen detection has been developed, whereby the detection sensitivity was 1000 times higher than that of the ELISA method. Firstly, a novel HRP enzyme–antibody copolymer (EV-p24 Ab2) was synthesized through an EnVision regent (EV, a dextrin amine skeleton anchoring more than 100 molecules of HRP and 15 molecules of anti IgG), then incubated in the secondary antibody of p24. Secondly, the copolymer was immobilized on the gold nanocolloids (AuNPs) to fabricate a novel signal tag (AuNPs/EV-p24 Ab2). Subsequently, a sandwich-type immunoreaction would take place between the capture probe (silicon dioxide-coated magnetic Fe3O4 nanoparticles (MNPs) labeled with the primary p24 antibody (MNPs-p24 Ab1)), p24 (different concentrations) and the signal tag [AuNPs/EV-p24 Ab2)] to form the immunocomplex. Finally, the immunocomplex was absorbed on the surface of screen printed carbon electrode (SPCE) by a magnet and immersed in the o-hydroxyl phenol (HQ) and H2O2. The large amounts of HRP on the signal tag can catalyze the oxidation of HQ by H2O2, which can induce an amplified reductive current. Moreover, the capture probe could improve the accumulation ability of p24 and facilitate its separation from the substrate through the magnet. Under optimal conditions, the proposed immunoassay exhibited good sensitivity to p24 within a certain concentration range from 0.001 to 10.00 ng/mL, with a detection limit of 0.5 pg/mL (S/N = 3). The proposed method can be used for real-time and early detection of HIV-infected people. Materials 2013-03-25 6 4 Article 10.3390/ma6041255 1255 1269 1996-1944 2013-03-25 doi: 10.3390/ma6041255 Ning Gan Xiaowen Du Yuting Cao Futao Hu Tianhua Li Qianli Jiang http://www.mdpi.com/1996-1944/6/4/1237 We evaluated the bioflocculant production potential of an Actinobacteria, which was isolated from a freshwater environment in the Eastern Cape province of South Africa. 16S rDNA nucleotide sequencing analyses revealed that the actinobacteria belongs to the Brachybacterium genus, and the sequences were deposited in the GenBank as Brachybacterium sp. UFH, with accession number HQ537131. Optimum fermentation conditions for bioflocculant production by the bacteria include an initial medium pH of 7.2, incubation temperature of 30 °C, agitation speed of 160 rpm and an inoculum size of 2% (vol/vol) of cell density 3.0 × 108 CFU/mL. The carbon, nitrogen and cation sources for optimum bioflocculant production were maltose (83% flocculating activity), urea (91.17% flocculating activity) and MgCl2 (91.16% flocculating activity). Optimum bioflocculant production coincided with the logarithmic growth phase of the bacteria, and chemical analyses of the bioflocculant showed 39.4% carbohydrate and 43.7% protein (wt/wt). The mass ratio of neutral sugar, amino sugar and uronic acids was 1.3:0.7:2.2. Fourier transform infrared spectroscopy (FTIR) indicated the presence of carboxyl, hydroxyl and amino groups, amongst others, typical for heteropolysaccharide and glycosaminoglycan polysaccharides. Bioflocculant pyrolysis showed thermal stability at over 600 °C, while scanning electron microscope (SEM) imaging revealed a maze-like structure of interlaced flakes. Its high flocculation activity suggests its suitability for industrial applicability. Materials 2013-03-25 6 4 Article 10.3390/ma6041237 1237 1254 1996-1944 2013-03-25 doi: 10.3390/ma6041237 Uchechukwu Nwodo Mayowa Agunbiade Ezekiel Green Mutshinyalo Nwamadi Karl Rumbold Anthony Okoh http://www.mdpi.com/1996-1944/6/4/1205 In this review, the main synthetic aspects and properties of fluorinated arylenevinylene compounds, both oligomers and polymers, are summarized and analyzed. Starting from vinyl organotin derivatives and aryl halides, the Stille cross-coupling reaction has been successfully applied as a versatile synthetic protocol to prepare a wide series of π-conjugated compounds, selectively fluorinated on the aromatic and/or vinylene units. The impact of fluoro-functionalization on properties, the solid state organization and intermolecular interactions of the synthesized compounds are discussed, also in comparison with the non-fluorinated counterparts. Luminescent and photovoltaic applications are also discussed, highlighting the role of fluorine on the performance of devices. Materials 2013-03-25 6 4 Review 10.3390/ma6041205 1205 1236 1996-1944 2013-03-25 doi: 10.3390/ma6041205 Carmela Martinelli Gianluca Farinola Vita Pinto Antonio Cardone http://www.mdpi.com/1996-1944/6/3/1191 This study investigates the effectiveness of concrete protection with two inorganic silicate sealer materials (ISSMs). The Taguchi method and grey relational analysis (GRA) have been used to identify the key factors influencing concrete protection provided by the surface treatment. Seven control factors with two levels were selected. By using the orthogonal array L12 (27), 12 experiments are chosen and four tests—the compressive strength test, resistivity test, absorption test and permeability test—were performed. Results have shown that the major factors affecting the protection effectiveness of ISSM are the water-binder ratio of mortar substrate, age of substrate for sealer application, addition of pozzolanic material and sealer type. Materials 2013-03-22 6 3 Article 10.3390/ma6031191 1191 1204 1996-1944 2013-03-22 doi: 10.3390/ma6031191 Si-Yu Zou Ran Huang Mao-Chieh Chi Hui-Mi Hsu http://www.mdpi.com/1996-1944/6/3/1159 This review deals with the correlation between morphology, structure and performance of organic electronic devices including thin film transistors and solar cells. In particular, we report on solution processed devices going into the role of the 3D supramolecular organization in determining their electronic properties. A selection of case studies from recent literature are reviewed, relying on solution methods for organic thin-film deposition which allow fine control of the supramolecular aggregation of polymers confined at surfaces in nanoscopic layers. A special focus is given to issues exploiting morphological structures stemming from the intrinsic polymeric dynamic adaptation under non-equilibrium conditions. Materials 2013-03-22 6 3 Review 10.3390/ma6031159 1159 1190 1996-1944 2013-03-22 doi: 10.3390/ma6031159 Sebastiano Cataldo Bruno Pignataro http://www.mdpi.com/1996-1944/6/3/1138 Carbon nanotubes (CNTs) have displayed great potential as anode materials for lithium ion batteries (LIBs) due to their unique structural, mechanical, and electrical properties. The measured reversible lithium ion capacities of CNT-based anodes are considerably improved compared to the conventional graphite-based anodes. Additionally, the opened structure and enriched chirality of CNTs can help to improve the capacity and electrical transport in CNT-based LIBs. Therefore, the modification of CNTs and design of CNT structure provide strategies for improving the performance of CNT-based anodes. CNTs could also be assembled into free-standing electrodes without any binder or current collector, which will lead to increased specific energy density for the overall battery design. In this review, we discuss the mechanism of lithium ion intercalation and diffusion in CNTs, and the influence of different structures and morphologies on their performance as anode materials for LIBs. Materials 2013-03-21 6 3 Review 10.3390/ma6031138 1138 1158 1996-1944 2013-03-21 doi: 10.3390/ma6031138 Zhili Xiong Young Yun Hyoung-Joon Jin http://www.mdpi.com/1996-1944/6/3/1118 Recent work in the creep field has indicated that the traditional methodologies involving power law equations are not sufficient to describe wide ranging creep behaviour. More recent approaches such as the Wilshire equations however, have shown promise in a wide range of materials, particularly in extrapolation of short term results to long term predictions. In the aerospace industry however, long term creep behaviour is not critical and more focus is required on the prediction of times to specific creep strains. The current paper illustrates the capability of the Wilshire equations to recreate full creep curves in a modern nickel superalloy. Furthermore, a finite-element model based on this method has been shown to accurately predict stress relaxation behaviour allowing more accurate component lifing. Materials 2013-03-20 6 3 Article 10.3390/ma6031118 1118 1137 1996-1944 2013-03-20 doi: 10.3390/ma6031118 William Harrison Mark Whittaker Steve Williams http://www.mdpi.com/1996-1944/6/3/1090 The aim of this article is to present an overview of salient issues of exposure, characterisation and hazard assessment of nanomaterials as they emerged from the consensus-building of experts undertaken within the four year European Commission coordination project NanoImpactNet. The approach adopted is to consolidate and condense the findings and problem-identification in such a way as to identify knowledge-gaps and generate a set of interim recommendations of use to industry, regulators, research bodies and funders. The categories of recommendation arising from the consensual view address: significant gaps in vital factual knowledge of exposure, characterisation and hazards; the development, dissemination and standardisation of appropriate laboratory protocols; address a wide range of technical issues in establishing an adequate risk assessment platform; the more efficient and coordinated gathering of basic data; greater inter-organisational cooperation; regulatory harmonization; the wider use of the life-cycle approaches; and the wider involvement of all stakeholders in the discussion and solution-finding efforts for nanosafety. Materials 2013-03-20 6 3 Article 10.3390/ma6031090 1090 1117 1996-1944 2013-03-20 doi: 10.3390/ma6031090 Geoffrey Hunt Iseult Lynch Flemming Cassee Richard Handy Teresa Fernandes Markus Berges Thomas Kuhlbusch Maria Dusinska Michael Riediker http://www.mdpi.com/1996-1944/6/3/1072 This paper presents a study conducted on the thermo-mechanical properties of knitted structures, the methods of manufacture, effect of contact pressure at the structural binding points, on the degree of heating. The test results also present the level of heating produced as a function of the separation between the supply terminals. The study further investigates the rate of heating and cooling of the knitted structures. The work also presents the decay of heating properties of the yarn due to overheating. Thermal images were taken to study the heat distribution over the surface of the knitted fabric. A tensile tester having constant rate of extension was used to stretch the fabric. The behavior of temperature profile of stretched fabric was observed. A comparison of heat generation by plain, rib and interlock structures was studied. It was observed from the series of experiments that there is a minimum threshold force of contact at binding points of a knitted structure is required to pass the electricity. Once this force is achieved, stretching the fabric does not affect the amount of heat produced. Materials 2013-03-20 6 3 Article 10.3390/ma6031072 1072 1089 1996-1944 2013-03-20 doi: 10.3390/ma6031072 Syed Hamdani Prasad Potluri Anura Fernando http://www.mdpi.com/1996-1944/6/3/1061 Incorporation of pigment or dye molecules as building units is of great interest in the development of semiconducting polymers, due to their strong intermolecular interactions arising from the strong local dipoles in the unit structure, which would facilitate the charge transport property. In this paper, semiconducting polymers based on well-known pigments, namely, quinacridone and diketopyrrolopyrrole, are synthesized and characterized. The π-stacking distances are found to be 3.5–3.8 Å, which is fairly narrow for semiconducting polymers, indicating that they possess strong intermolecular interactions. Interestingly, polymer orientation is influenced by the composition of alkyl side chains. While the edge-on orientation is observed when the linear alkyl groups are introduced for all the side chains, the face-on orientation is observed when the branched alkyl groups are introduced either in the quinacridone or diketopyrrolopyrrole unit. It is found that the electronic structure of the present polymers is mostly affected by that of the diketopyrrolopyrrole unit, as evidenced by the absorption spectra and computation. Although the field-effect mobility of the polymers is modest, i.e., in the order of 10−4–10−3 cm2/Vs, these findings could be important information for the development of semiconducting polymers. Materials 2013-03-18 6 3 Article 10.3390/ma6031061 1061 1071 1996-1944 2013-03-18 doi: 10.3390/ma6031061 Masahiro Akita Itaru Osaka Kazuo Takimiya http://www.mdpi.com/1996-1944/6/3/1050 Photoluminescence (PL) studies in GaN thin films grown by infrared close space vapor transport (CSVT-IR) in vacuum are presented in this work. The growth of GaN thin films was done on a variety of substrates like silicon, sapphire and fused silica. Room temperature PL spectra of all the GaN films show near band-edge emission (NBE) and a broad blue and green luminescence (BL, GL), which can be seen with the naked eye in a bright room. The sample grown by infrared CSVT on the silicon substrate shows several emission peaks from 2.4 to 3.22 eV with a pronounced red shift with respect to the band gap energy. The sample grown on sapphire shows strong and broad ultraviolet emission peaks (UVL) centered at 3.19 eV and it exhibits a red shift of NBE. The PL spectrum of GaN films deposited on fused silica exhibited a unique and strong blue-green emission peak centered at 2.38 eV. The presence of yellow and green luminescence in all samples is related to native defects in the structure such as dislocations in GaN and/or the presence of amorphous phases. We analyze the material quality that can be obtained by CSVT-IR in vacuum, which is a high yield technique with simple equipment set-up, in terms of the PL results obtained in each case. Materials 2013-03-15 6 3 Article 10.3390/ma6031050 1050 1060 1996-1944 2013-03-15 doi: 10.3390/ma6031050 Guillermo Santana Osvaldo de Melo Jorge Aguilar-Hernández Rogelio Mendoza-Pérez B. Monroy Adolfo Escamilla-Esquivel Máximo López-López Francisco de Moure Luis Hernández Gerardo Contreras-Puente http://www.mdpi.com/1996-1944/6/3/1028 While little success has been obtained over the past few years in attempts to increase the capacity of Li-ion batteries, significant improvement in the power density has been achieved, opening the route to new applications, from hybrid electric vehicles to high-power electronics and regulation of the intermittency problem of electric energy supply on smart grids. This success has been achieved not only by decreasing the size of the active particles of the electrodes to few tens of nanometers, but also by surface modification and the synthesis of new multi-composite particles. It is the aim of this work to review the different approaches that have been successful to obtain Li-ion batteries with improved high-rate performance and to discuss how these results prefigure further improvement in the near future. Materials 2013-03-15 6 3 Review 10.3390/ma6031028 1028 1049 1996-1944 2013-03-15 doi: 10.3390/ma6031028 Karim Zaghib Alain Mauger Henri Groult John Goodenough Christian Julien http://www.mdpi.com/1996-1944/6/3/1011 : A simple procedure was developed for the fabrication of electrochemical glucose biosensors using glucose oxidase (GOx), with graphene or multi-walled carbon nanotubes (MWCNTs). Graphene and MWCNTs were dispersed in 0.25% 3-aminopropyltriethoxysilane (APTES) and drop cast on 1% KOH-pre-treated glassy carbon electrodes (GCEs). The EDC (1-ethyl-(3-dimethylaminopropyl) carbodiimide)-activated GOx was then bound covalently on the graphene- or MWCNT-modified GCE. Both the graphene- and MWCNT-based biosensors detected the entire pathophysiological range of blood glucose in humans, 1.4–27.9 mM. However, the direct electron transfer (DET) between GOx and the modified GCE’s surface was only observed for the MWCNT-based biosensor. The MWCNT-based glucose biosensor also provided over a four-fold higher current signal than its graphene counterpart. Several interfering substances, including drug metabolites, provoked negligible interference at pathological levels for both the MWCNT- and graphene-based biosensors. However, the former was more prone to interfering substances and drug metabolites at extremely pathological concentrations than its graphene counterpart. Materials 2013-03-14 6 3 Article 10.3390/ma6031011 1011 1027 1996-1944 2013-03-14 doi: 10.3390/ma6031011 Dan Zheng Sandeep Vashist Michal Dykas Surajit Saha Khalid Al-Rubeaan Edmond Lam John Luong Fwu-Shan Sheu http://www.mdpi.com/1996-1944/6/3/1000 A new “omic” platform—Cosmetomics—that proves to be extremely simple and effective in terms of sample preparation and readiness for data acquisition/interpretation is presented. This novel approach employing Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) for cosmetic analysis has proven to readily identify and quantify compounds of interest. It also allows full control of all the production phases, as well as of the final product, by integration of both analytical and statistical data. This work has focused on products of daily use, namely nail polish, lipsticks and eyeliners of multiple brands sold in the worldwide market. Materials 2013-03-13 6 3 Article 10.3390/ma6031000 1000 1010 1996-1944 2013-03-13 doi: 10.3390/ma6031000 Diogo de Oliveira Sabrina de Bona Sartor Mônica Ferreira Rodrigo Catharino http://www.mdpi.com/1996-1944/6/3/981 SBA-15 prepared via ethanol extraction for template removing was grafted with three kinds of amine precursors (mono-, di-, tri-aminosilanes) to synthesis new CO2 adsorbents. The SBA-15 support and the obtained adsorbents were characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), N2 adsorption/desorption, thermogravimetry (TG), elemental analysis, Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that, except higher silanol density, the ethanol-extracted SBA-15 support possessed a more regular mesophase and thicker walls than traditionally calcined samples, leading to a good stability of the adsorbent under steam treatment. The adsorption capacity of different amine-grafted samples was found to be influenced by not only the surface amine density, but also their physiochemical properties. These observations provide important support for further studies of applying amine-grafted adsorbents in practical CO2 capture process. Materials 2013-03-12 6 3 Article 10.3390/ma6030981 981 999 1996-1944 2013-03-12 doi: 10.3390/ma6030981 Yong Li Nannan Sun Lei Li Ning Zhao Fukui Xiao Wei Wei Yuhan Sun Wei Huang http://www.mdpi.com/1996-1944/6/3/969 Polyacrylonitrile (PAN) nanofibers were prepared by electrospinning and they were modified with hydroxylamine to synthesize amidoxime polyacrylonitrile (AOPAN) chelating nanofibers, which were applied to adsorb copper and iron ions. The conversion of the nitrile group in PAN was calculated by the gravimetric method. The structure and surface morphology of the AOPAN nanofiber were characterized by a Fourier transform infrared spectrometer (FT-IR) and a scanning electron microscope (SEM), respectively. The adsorption abilities of Cu2+ and Fe3+ ions onto the AOPAN nanofiber mats were evaluated. FT-IR spectra showed nitrile groups in the PAN were partly converted into amidoxime groups. SEM examination demonstrated that there were no serious cracks or sign of degradation on the surface of the PAN nanofibers after chemical modification. The adsorption capacities of both copper and iron ions onto the AOPAN nanofiber mats were higher than those into the raw PAN nanofiber mats. The adsorption data of Cu2+ and Fe3+ ions fitted particularly well with the Langmuir isotherm. The maximal adsorption capacities of Cu2+ and Fe3+ ions were 215.18 and 221.37 mg/g, respectively. Materials 2013-03-11 6 3 Article 10.3390/ma6030969 969 980 1996-1944 2013-03-11 doi: 10.3390/ma6030969 Fenglin Huang Yunfei Xu Shiqin Liao Dawei Yang You-Lo Hsieh Qufu Wei http://www.mdpi.com/1996-1944/6/3/941 The ultrahighly nanoporous aerogel is recognized as a state of matter rather than as a functional material, because of its qualitative differences in bulk properties, transitional density and enthalpy between liquid and gas, and diverse chemical compositions. In this review, the characteristics, classification, history and preparation of the aerogel were introduced. More attention was paid to the sol-gel method for preparing different kinds of aerogels, given its important role on bridging the synthetic parameters with the properties. At last, preparation of a novel single-component aerogel, design of a composite aerogel and industrial application of the aerogel were regarded as the research tendency of the aerogel state in the near future. Materials 2013-03-08 6 3 Review 10.3390/ma6030941 941 968 1996-1944 2013-03-08 doi: 10.3390/ma6030941 Ai Du Bin Zhou Zhihua Zhang Jun Shen http://www.mdpi.com/1996-1944/6/3/927 Pure whey protein isolate (WPI)-based cast films are very brittle due to its strong formation of protein cross-linking of disulphide bonding, hydrogen bonding as well as hydrophobic and electrostatic interactions. However, this strong cross-linking is the reason for its final barrier performance. To overcome film brittleness of whey protein layers, plasticisers like glycerol are used. It reduces intermolecular interactions, increases the mobility of polymer chains and thus film flexibility can be achieved. The objective of this study was to investigate the influence of hydrolysed whey protein isolate (WPI) in whey protein isolate-based cast films on their techno-functional properties. Due to the fact, that the addition of glycerol is necessary but at the same time increases the free volume in the film leading to higher oxygen and water vapour permeability, the glycerol concentration was kept constant. Cast films with different ratios of hydrolysed and not hydrolysed WPI were produced. They were characterised in order to determine the influence of the lower molecular weight caused by the addition of hydrolysed WPI on the techno-functional properties. This study showed that increasing hydrolysed WPI concentrations significantly change the mechanical properties while maintaining the oxygen and water vapour permeability. The tensile and elastic film properties decreased significantly by reducing the average molecular weight whereas the yellowish coloration and the surface tension considerably increased. This study provided new data which put researchers and material developers in a position to tailor the characteristics of whey protein based films according to their intended application and further processing. Materials 2013-03-07 6 3 Article 10.3390/ma6030927 927 940 1996-1944 2013-03-07 doi: 10.3390/ma6030927 Markus Schmid Lesley-Virgina Hinz Florian Wild Klaus Noller http://www.mdpi.com/1996-1944/6/3/911 Carbon nanostructures have played an important role in creating a new field of materials based on carbon. Chemical modification of carbon nanostructures through grafting has been a successful step to improve dispersion and compatibility in solvents, with biomolecules and polymers to form nanocomposites. In this sense carbohydrates such as chitosan are extremely valuable because their functional groups play an important role in diversifying the applications of carbon nanomaterials. This paper reports the covalent attachment of chitosan onto graphene oxide, taking advantage of this carbohydrate at the nanometric level. Grafting is an innovative route to modify properties of graphene, a two-dimensional nanometric arrangement, which is one of the most novel and promising nanostructures. Chitosan grafting was achieved by redox reaction using different temperature conditions that impact on the morphology and features of graphene oxide sheets. Transmission Electron Microscopy, Fourier Transform Infrared, Raman and Energy Dispersive spectroscopies were used to study the surface of chitosan-grafted-graphene oxide. Results show a successful modification indicated by the functional groups found in the grafted material. Dispersions of chitosan-grafted-graphene oxide samples in water and hexane revealed different behavior due to the chemical groups attached to the graphene oxide sheet. Materials 2013-03-07 6 3 Article 10.3390/ma6030911 911 926 1996-1944 2013-03-07 doi: 10.3390/ma6030911 Karina Bustos-Ramírez Ana Martínez-Hernández Gonzalo Martínez-Barrera Miguel Icaza Víctor Castaño Carlos Velasco-Santos http://www.mdpi.com/1996-1944/6/3/897 We measured the picoseconds (ps) transient dynamics of photoexcitations in blends of regio-regular poly(3-hexyl-thiophene) (RR-P3HT) (donors-D) and fullerene (PCBM) (acceptor-A) in an unprecedented broad spectral range of 0.25 to 2.5 eV. In D-A blends with maximum domain separation, such as RR-P3HT/PCBM, with (1.2:1) weight ratio having solar cell power conversion efficiency of ~4%, we found that although the intrachain excitons in the polymer domains decay within ~10 ps, no charge polarons are generated at their expense up to ~1 ns. Instead, there is a build-up of charge-transfer (CT) excitons at the D-A interfaces having the same kinetics as the exciton decay. The CT excitons dissociate into separate polarons in the D and A domains at a later time (>1 ns). This “two-step” charge photogeneration process may be typical in organic bulk heterojunction cells. We also report the effect of adding spin 1/2 radicals, Galvinoxyl on the ultrafast photoexcitation dynamics in annealed films of RR-P3HT/PCBM blend. The addition of Galvinoxyl radicals to the blend reduces the geminate recombination rate of photogenerated CT excitons. In addition, the photoexcitation dynamics in a new D-A blend of RR-P3HT/Indene C60 trisadduct (ICTA) has been studied and compared with the dynamics in RR-P3HT/PCBM. Materials 2013-03-06 6 3 Article 10.3390/ma6030897 897 910 1996-1944 2013-03-06 doi: 10.3390/ma6030897 Sanjeev Singh Zeev Vardeny