Materials Science Forum Vol. 750

Abstract: ZnTe solar cells with homojunction and heterojunction structures have been developed. Homojunction was fabricated by thermal diffusion of Al into p-ZnTe, and the effect of the diffusion temperature on the photovoltaic (PV) properties was investigated. The highest efficiency was obtained by lowering the diffusion temperature and using p-ZnTe substrate with a low hole concentration. For the heterojunction solar cell, n-ZnO/i-ZnTe/p-ZnTe structure was fabricated, and PV properties were characterized.

Abstract: Horseradish peroxidase (HRP) and toluidine blue (TB) were incorporated in polyion complex membrane composed of double stranded DNA(dsDNA) and chitosan prepared on the surface of an glassy carbon (GC) disk electrode to fabricate highly sensitive and selective reagentless H2O2 biosensor. The embedded-TB in the DNA/chitosan membrane exhibited excellent electrochemical redox property with an electron transfer rate constant of 3.12 ± 0.5 sec−1, and shuttled electron effectively from the base GC electrode to catalytic center of the HRP. Under the applied potential of -0.22V (versus Ag/AgCl) and pH 7.0, the resulting electrode (HRP/DNA–TB/chitosan/GCE) exhibited rapid (<10 s) and sensitive response to H2O2. The calibration curve of H2O2, plotting steady-state cathodic current versus H2O2 concentration, was linear up to 0.1mM with a detection limit of 1 μM H2O2 (S/N = 3). The H2O2 response was scarcely interfered by ascorbic acid and uric acid, which potentially reduce oxidized intermediate of the HRP and interfere with the response of peroxidase-based electrodes.

Abstract: This work was to clarify the characteristics of serrated flow in an austenitic FeMnC twin-induced plasticity (TWIP) steel at room temperature (RT) using both strain- and crosshead displacement-controlled tensile tests. Three types of serrations were observed in strain-controlled but not in displacement-controlled tests, indicating that strain-controlled tensile tests provide more deformation details. The occurrence of the different types of serrations depends on both strain rate and strain level. Type C serrations were observed in TWIP steels at RT for the first time. The critical strain for the onset of serrations exhibits a positive strain rate dependence at higher strain rates, whereas an “inverse” critical strain behavior was observed in the lower strain rate region.

Abstract: Al2O3 matrix composites reinforced with Ba-b-Al2O3 phase were synthesized through reactive sintering using Al2O3 and BaCO3 as starting powders. Dense Al2O3/Ba-b-Al2O3 composites can be obtained by spark plasma sintering from Al2O3/BaO•Al2O3 powder, which was prepared by calcining Al2O3/BaCO3 powder mixture. The Ba-b-Al2O3 reinforcing phase exhibited an elongated morphology due to preferred diffusion of Ba cations. The existence of Ba-b-Al2O3 phase as well as low sintering temperature and short holding time during reactive sintering inhibit grain growth and thus result in small grain sizes of the Al2O3 matrix.

Abstract: A cost effective directional solidification (DS) technique is one of the main methods to produce multi-crystalline silicon (mc-Si) ingots for solar cells. A detailed understanding of the DS process is very important to control the formation and distribution of impurities, precipitates, thermal stress and dislocation defects in an ingot. All these factors have direct effects on the solar cells efficiency. The quality of crystal grown by DS is largely determined by the temperature field. In order to optimize the technique parameters and obtain high quality silicon ingots, the temperature fields with different heat transfer coefficients at different positions have been calculated during the silicon DS process. The influence of the heat transfer coefficients at the ingot top(h_t), the ingot bottom (h_b), and between ingot and crucible (h_s) on the DS process of mc-Si have been analyzed. The calculation results may provide important theoretical basis for optimizing technological recipe in the productive practice.

Abstract: This work proposes a rheological model for a nanoporous-elasto-hydrodynamic composite material (NPEHDCM), which can be obtained by mixing a colloid, consisted of water and water-repellent nanoporous silica micro-particles, with an adequate jellification agent. Hydrogel is modeled as a biphasic mixture consisted of a nanoporous hydrophilic isotropic and linear elastic solid matrix, and a liquid phase (water). At dynamic pressurization, water molecules exude from the hydrogel matrix and forcedly penetrate the nanopores of hydrophobic silica particles. Based on the proposed rheological model, the NPEHDCM can be suitably designed.

Abstract: The influence of glass coating thickness on the interfacial heat transfer coefficient has been examined using numerical modeling. Temperature and heat flux during working of a Inconel 718 work-piece and colder H13 dies have been simulated. The thickness of the glass coating is found to have a significant influence on the forming characteristic.

Abstract: In this paper, the interlaminar shear strength properties of laminated binderless bamboo composites is described. The binderless bamboo composites were prepared by hot-pressing of steam-exploded Moso bamboo stripes. In order to explore the effect of node section on the mechanical properties of the laminated binderless bamboo composites, the node section was flattened by shaving the nodes off. The result of our experiment clearly shows that the shear strength of the laminated binderless bamboo composites increased by flattening of the node section.

Abstract: The fatigue limit of a plain specimen of a tool steel JIS SK85 was investigated. The initial crack length in the fatigue process is related to the size of a single crystal in the case of low carbon steel. However, that is independent of the crystal size in the case of pure aluminum, a lamellar pearlitic steel, etc. In this study, the relationship between the initial crack length and the fatigue limit was investigated. The original microstructure of this material includes a spherical microstructure. However, after heat treatment under some conditions, that microstructure changed to a lamellar microstructure. The fatigue limit of heat-treated SK85 could be evaluated by an equation in which the parameters are the hardness and initial crack length. Finally, this result was discussed based on the observations of crack growth behavior and fracture surface.

Abstract: This study presents an application of Hall Effect sensor to assess the viscosity of industrial lubricant by using reference metal particles with the dimension ranging from 1 µm to 100 µm and the mass ranging from 0.1 g to 1 g as the essential modules of the developed system. Hall Effect sensor is a small electronic component which is easy for installing, analyzing, and processing due to electrical output generated. Moreover, the cost of this developed method is lower than other means of viscosity tests. At present, there are several studies on viscosity and quality tests of industrial lubricants such as Ultrasonic measurement of viscosity of liquids [1], Photoacoustic measurement of liquid viscosity [2], Measurement of magnetic viscosity in NdFeB [3], A viscosity and density meter with a magnetically suspended rotor [4], Capacitive sensor [5], IR-Absorption [6], and Optical fiber sensing [7]. In this study, the measurement methodology was considered only the lubricant viscosity at the temperature of 26 °C and then compared the results to the viscosity classification which is the reference of lubricant characteristic. Moreover, the lubricant types namely SAE 15W-40, SAE 20W-50 and ISO VG 100 were selected as the case studies.