Advanced Materials Research Vols. 139-141

Abstract: Wood plastic composite (WPC) is very useful new material in the modern society. Improving the interfacial bond strength between wood and plastic is the foundation of improving the properties of WPC. Ethylene vinyl acetate (EVA) was used as the coupling agent of WPC in this study. Thermo-gravimetric analysis (TGA) was employed to study the thermal stability of wood flour modified by EVA. The modulus of rupture (MOR), the modulus of elasticity (MOE), and the tensile strength of WPC were investigated to understand the effects of the vinyl acetate (VA) content and the melt index of EVA on WPC. The results show that EVA could improve the thermal stability of wood flour and the mechanical properties of WPC. The mechanical properties of WPC are increasing with VA content raise and melt index reducing.

Abstract: The stab resistance of thermoset(TS) impregnated, woven UHMWPE fabric with additional steel fabrics was investigated under dynamic stab testing conditions. Vinyl-ester resin was coated on the UHMWPE fabrics with hand lay-up process to fabricate the composite and the mental fabrics were laminated on the composites. Dynamic stab testing of targets was based on GA68-2008 for stab resistance of body armor. Six uniform specified knives impactor were used for testing. And the samples are found to present significant improvements in stab resistance (knife threat) over neat fabric targets of equal areal density. Photographs show that resin primarily reduces the mobility of yarns and enables them to stop the knife penetration more effectively in the damage zone. These results indicate that the penetration of knives through such multilayer fabrics is effectively prevented and the process could be used to fabricate flexible body armors that provide improved protection against stab threat.

Abstract: Optical fiber sensor with small size, light weight and immunity to electromagnetic interference can be embedded and integrated into the host material to form an ideally smart structure system. One must recognize that optical fibers are foreign entities to the host structure, therefore will induce high stress state in the vicinity of the embedded sensor irrespective of the small size of the fiber. To address this concern, present paper focuses the attention on constituent interaction between the optical fiber, coating, matrix and host material. An analytical model to predict the stress fields in the vicinity of the embedded optical fiber is presented. The theoretical development is based on the four concentric cylinders model which represents the optical fiber, protective coating, matrix and host material, respectively. The host material is considered to be a composite with reinforced fiber parallel to the optical fiber. In this investigation, the host structure is subjected to in-plane shear loading. The effects of the coating and host material on the stress distribution in the vicinity of the embedded optical fiber are presented through a parametric study.

Abstract: Solid oxide fuel cells (SOFCs) have been the centre of much research attention as these shows much potential in the generation of electrical power especially in terms of the high conversion efficiency of chemical energy to electric power. Recent research has been focused on a new material which is an electro catalyst for the oxygen reduction reaction in the intermediate temperature range (600-800oC). In this work, perovskite oxide which is a mixed ionic conducting material, La1-xSrxCo0.2Fe0.8O3-δ (LSCF) with x = 0.3-0.5 has been developed using the sol-gel method. The obtained powders were pelletized and sintered at different temperatures from 800 to1300oC. The sintered properties of the LSCF pellets such as density, porosity, grain size and shrinkage were investigated. A sintering temperature of 900oC was found to be the optimum temperature for the preparation of the LSCF cathodes in this study.

Abstract: Zinc sulfide thin films were deposited on optical glass substrates by using chemical bath deposition (CBD) technique that contain solutions of thiourea, zinc acetate, ammonia and sodium citrate. The deposition time were varied from 18 hours to 39 hours. SEM, XRD, and UV-Vis-NIR were used to characterize the sample which shows that the films are thicker and the grains sizes are bigger as the deposition time increases. X-ray diffraction (XRD) pattern prove that ZnS thin films are in disordered since it does not revealing any peaks and the surface of ZnS thin films are amorphous. UV-Vis spectra showed that the deposited ZnS thin films have more than 100% transmittance in the visible region and direct band gap of deposited films are in range of 2.45 eV to 3.53 eV. Time increasing of deposition will slightly decrease the transmittance of the film.

Abstract: A dye-sensitized solar cell based on TiO2 electrode was prepared by mixing the TiO2 nanopowder and TiCl4 aqueous solution, in which the mixture was used as the paste to deposit onto the fluorine doped tin oxide (FTO) coated glass substrates by screen-printing method. DSSC were created after a rinse of TiO2 electrode with acetonitrile to remove excess dye molecules. The synthesis and characterization of the TiO2 paste was figured out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The TiO2 layer is homogeneous and composed of anatase and rutile particles. The photocurrent-voltage of the cell was fabricated and the comparison dye was made by using the eosin Y and N719. The sample that use N719 dye showed the better result which is generating a short-circuit photocurrent density of 0.0299 mA/cm2, an open-circuit voltage of 0.713 V, and the energy conversion efficiency was 0.08926 %.

Abstract: This paper describes a heat treatment process using dual aging for the A7050 aluminum alloy with the Taguchi method to optimize process parameters. The current study considers micro hardness and electrical conductivity as optimization criteria. Pre-aging temperature, pre-aging time, re-aging temperature, and re-aging time are important factors influencing these optimization criteria. Experiment results show that re-aging temperature is the most significant parameter for electrical conductivity, and both aging times are important influence factors for micro hardness performance. The optimal hardness for A7050 heat treatment conditions are pre-ageing temperature 120 °C, pre-ageing time 12hrs., re-aging temperature140 °C, and re-aging time 8 hrs., respectively. The best electrical conductivity parameters are pre-ageing temperature 120 °C, pre-ageing time 4 hrs., re-aging temperature180 °C, and re-aging time 24 hrs., respectively. The current study obtained contributing individual parameters for hardness, and electrical conductivity in dual aging of heat treatment.

Abstract: A practical electropulsing treatment device has been developed based on capacitor energy storage and discharge technology. The device was controlled by a pair of charge and discharge switches which close in turn to produce high density electropulsing. The electropulsing treatment experiment was carried out by capacitor discharging while an exponential damping oscillatory waveform was produced. A group of 45 steel quenched specimens were connected into the discharge circuit with copper electrodes through a vacuum contactor switch. At last, a typical waveform of electropulsing was detected by a DS5062MA digital storage oscilloscope. This waveform demonstrates that the first peak of electropulsing has reached 23 kA, and the discharging process has concluded within 0.6 ms. Results indicate that the energy density of electropulsing treatment is very concentrated because of the waveform of high peak value and short duration. The device is now being used for the stress relief processing of metals.

Abstract: Groundbreaking work and past standard of surface integrity regarding description, measurement and evaluation of machined components are retrospected. Typical surface integrity characteristics such as surface topography, macro and microstructure, microhardness and residual stress distribution are preferentially adopted for quantitatively describing and systematically evaluating of surface integrity. Corresponding processing conditions and fatigue performance along with surface integrity characteristics are also detailedly classified and digitally defined through meaningful data sets. A framework of surface integrity model for machined components is subsequently proposed and preliminarily established by understanding the nature of surface integrity and its relation with processing parameters and fatigue properties. This pilot study offers a conceptual model as well as some feasible operational approaches for control of surface integrity in cutting technology and consequent improvement of the fatigue life for machined components.