Advanced Materials Research Vols. 538-541

Abstract: In this paper the dielectric properties including volume resistivity, relative permittivity and break down voltage for plasma sprayed Al₂O₃ coating with and without sealing treatment and as sprayed Al₂O₃-3wt%TiO₂ coating with sealing treatment were evaluated. The effect of silicon resin sealing reagent on dielectric properties of plasma sprayed Al₂O₃ coating was explored. The results indicated that volume resistivity, relative permittivity and break down voltage for Al2O3 and Al₂O₃-3wt%TiO₂ coating with silicon resin sealing treatment was 6.33±2.25×10⁹Ω.m, 8.11±2.99, 16.42±1.68 kV/mm and 1.06±0.5×10¹⁰Ω.m, 7.40±0.15, 14.27±1.20 kV/mm respectively. Sealing treatment was helpful for the dielectric properties of Al₂O₃ coating owing to the decreased residual water in the coating.

Abstract: YSZ/Al2O3 composite coatings have been fabricated by using EPD. The microstructures, mechanical properties and micro-stresses of the coatings produced from different sized powders and sintered at different temperatures have been studied. Different attrition milling time leads to different particle distribution modes, thereby different microstructures. Due to the deposition process and the constraint effect from the substrate, a gradient structure has been formed across the coating thickness.

Abstract: The deposition of alumina (nano-powder, <80nm) and zirconia doped with yttria laminar composite coatings on Ni3Al coatings were investigated via a complex method of Sol-Gel, electrolytic deposition (ELD) and electrophoretic deposition (EPD). The average particle sizes of alumina and zirconia are 80nm and 20nm respectively. The relation of deposition parameters (deposition voltage, dwell time) and deposition rate was discussed based on the experiment results of alumina, zirconia single and laminated coatings deposition. The post thermal treatments were performed in attempt to acquire a dense multilayer composite ceramic coating. The uniform duplex or laminar coatings could be achieved via this complex method. The surface and cross-sectional morphologies of two layers and ten layers alumina/ zirconia composite ceramic coating after sintering showed that the laminar structure thickness could be tailored by controlling the deposition voltage and dwell time. The sintering mechanism of nano-sized alumina and zirconia was also discussed.

Abstract: In the detection of steel ball surface defects, the non-destructive eddy current testing has the advantage of reliability, high efficiency, non-contact and easy to automate, etc. Base on the establishment of the mathematical model of the ball surface unfolding, Correct processing of eddy current sensor output signal is the first conditions of accuracy. In the paper, base on the propose of unfolding mechanism of the ball's surface, with smooth, phase-sensitive detection, filtering and other methods to process the detected signal, so interference signals can be suppressed and to improve the signal to noise ratio; Then the signal can be further analyzed in time domain or frequency domain, the signal amplitude, frequency, phase and other characteristic quantities can be extracted, and the characteristic quantity of defect signal can be Calculated, So the surface quality of steel balls can be determined.

Abstract: Nowadays, many economists and scientist worry about sharply increased to fuel consumption. New energy sources have to be investigation now. This was a base on the low-emission gas, high-energy efficiency, permanence and possible with co-generation. Especially, transportation system has been restricted to system’s total weight. Light weight of a transportation system offers to increase performance. By using light weight in a transportation system, it gives another benefit that reduced oil consumption, improved fuel efficiency and increased Market-value. Fuel cell is one of the new energy systems for next generation. Normally, fuel cell consists of bipolar plate, MEA (Membrane Electrode Assembly) and GDL (Gas Diffusion Layer). Conventional bipolar plate material was used to graphite. Graphite has been very weak at external shock. Machining process is not easy, and the main problem is that the graphite material supplied by oxidizing and reducing agent composition of the gas leak comes. Thus, the manufacturing cost is increased by this reason. This study will be tried to bipolar plate material replacement from graphite materials to metallic material. In this experiment, STS316 base on austenite stainless steel was used. This experiment was observing an effect of surface conditions with corrosion behavior with Non-coated and CrN coated STS316 on a similar PEMFC operating condition. By the results of experimental, CrN coated condition has better corrosion resistance than that of Non-coated condition due to passivation layer on CrN coated surface.

Abstract: The CrN-based solid self-lubricant composite coating was obtained by magnetron sputtering and low-temperature ion sulfuring. The XPS, AES and SEM equipped with EDS were utilized to observe and analyze the microstructure of the composite coating. The results show that there are Cr, Mo, N, S in the composite coating, and the phase structure is CrN, MoS2 and a few oxide. The element S was implanted 500nm in depth. For the sulfurized layer is extremely apt to be oxidized, in this paper, the source of element O is analyzed in detail through comparative studies on different methods for preservation of specimens, and the film-forming mechanism of CrN-based solid self-lubricant composite coating is discussed.

Abstract: The enamel powder was preseted on the Ti alloy by electrophoresis, and the enamel coatings were obtained through sintering. Friction and abrasion performance of the enamel coatings and RE enamel coatings were compared. The results show that the RE element improved the inner organizational structure of the enamel coating, decreased the friction coefficient of the coating and consequently improved the friction-resistant character of the enamel coatings. By adding RE, the viscidity, suspension and fluidity of the enamel coatings are improved, and that the microstructure of the enamel coating are more dense and the horniness grain phase was more small in uniform during sintering.

Abstract: Optical losses or the effect of reflection from surface of light-matter devices have a significantly influence on their accuracy, reliability and efficiency. Solar cells, including silicon substrate solar cells or dye sensitized solar cells, are one of them. The simplest way to improve the efficiency of solar cells is introducing an anti-reflection coating. This paper investigates the performance of anti-reflection coating by introducing a composite material, using different deposition methods. It is found that the annealing temperature of single anti-reflection layer can reduce to 600 °C by using our recipe. Moreover, the efficiency of three layer anti-reflection coating is modeled by MATLAB to demonstrate the gradient refractive index theory.

Abstract: The present study shows the thermal modeling on AMTEC (Alkali-metal thermoelectric power generation) system by analytical 1-D simulation method. In the present study, the unique AMTEC design model which consists of an evaporator, single BASE (Beta-Alumina Solid Electrolyte) tube, condenser and artery cable wick were presented. The operating design target of the present AMTEC system were 700°C in the evaporator section, and 400°C in the condenser section for solar energy conversion. The present AMTEC system operates near 10-15 % efficiency and this can be improved with the optimum design of the system. In case of improved BASE design, the system can reach over 30% efficiency.

Abstract: Using polycarbosilane(PCS) as precursor materials, 2.5D、3D3d、3D4d、3D5d braided structure Cf/SiC composites were prepared by Precursor Infiltration and Pyrolysis (PIP). The result showed that different braided structure Cf/SiC composites had dissimilar change tendency of density and porosity. The braided structure and pore position influenced mechanical properties of Cf/SiC composites obviously. 2.5D Cf/SiC composites had the lowest mechanical properties compared others braided structure via PIP process, 3D5d Cf/SiC composites had the highest mechanical properties for the bending strength reached 334MPa, modulus 99.5GPa. Furthermore, the microstructure and properties of different braided structure Cf/SiC composites has been investigated by means of SEM.