多孔铝合金的铸造工艺研究

采用加压铸造工艺，制备出了多孔铝合金。系统地研究了预制块的制备工艺过程及影响因素。利用所制备的预制块，研究了多孔铝合金的加压铸造工艺。研究表明，预制块孔隙大小及其初始温度、金属液浇注温度、外加压力等影响了金属液在预制块中的充型长度。采用合理的工艺，就可以获得大尺寸的多孔制品。     

环境湿度对聚酰亚胺驻极体性能的影响

本文讨论了恒流电晕过程中环境湿度对聚酰亚胺驻极体表面电位建立的影响,分析了恒压充电后环境湿度对聚酰亚胺驻极体电荷储存稳定性的影响。利用热脉冲技术研究了不同湿度下电晕充电的聚酰亚胺薄膜沉积电荷平均深度向背电极的迁移规律。     

Isolation of silicon film grown on porous silicon layer

We have investigated a new technology for dielectric isolation of a Si film grown epitaxially on a porous silicon layer. After oxidation of the porous silicon layer, a Si on Ohcidized Porous Silicon(SOPS) structure can be obtained. It is proposed that micropores pinch off quickly in the interfacial region between the porous silicon layer and the epitaxial film. A minimum yield calculated from Rutherford backscattering spectra of the epitaxial silicon film is 5.3%, and an electron Hall mobility of 600cm²/V.s is obtained in the film with a carrier concentration of 1 x 10¹⁷ /cm³. MOSFETs were fabricated on the SOPS structure.     

Origin and prevention of high contact resistance in multilevel metal-polyimide structures

When polyimide is used as the insulating dielectric in multilevel-metal structures, a high contact resistance can result within the interconnecting vias. This paper examines the particular case of oxygen plasma patterning of the polyimide using a photoresist mask. Auger analysis in combination with compositional depth profiling was employed on a series of samples to measure surface composition of etched vias in polyimide. Results show two effects which, together, can account for high contact resistance: first, there is a thicker than normal aluminum oxide layer on the first level metal surface (due to exposure to the oxygen plasma); second, there is a thin, etch-resistant carbonaceous film (due to redeposition of organic material during plasma etching) that prevents oxide thinning through chemical means. It was found that by lowering the plasma pressure to 50 mTorr near the end of the etch, the organic film can be removed. In the absence of the carbonaceous layer, the oxide can then be chemically thinned to produce clean aluminum surfaces within the vias.     

ZnO/PS异质结的光学和电学性质

用脉冲激光沉积的方法在多孔硅(PS)衬底上沉积ZnO薄膜,在室温下测量了ZnO/PS异质结的结构及光学和电学性质.X射线衍射仪和扫描电子显微镜测量表明,制备的ZnO薄膜具有一定的c轴取向,但薄膜存在较多缺陷.光致发光谱显示,PS的发光与ZnO的发光相叠加,呈现白光发射.对异质结I-V特性曲线的测量表明,异质结呈现出与普通二极管不同的整流特性,其反向电流不饱和,据此提出了能带模型.     

THEORETICAL STUDY OF HEAT TRANSFER ENHANCEMENT IN PIPE WITH POROUS BODY

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＨｅａｔｔｒａｎｓｆｅｒｅｎｈａｎｃｅｍｅｎｔｂｙｐｏｒｏｕｓｂｏｄｙｈａｓｂｅｅｎｗｉｄｅｌｙｓｔｕｄｉｅｄｉｎｒｅｃｅｎｔｄｅｃａｄｅｓ .Ｔｈｅｐｏｒｏｕｓｂｏｄｙｓｔｕｄｉｅｄ ｐｒｅｖｉｏｕｓｌｙ ,ｗｉｔｈｔｈｅｐｏｒｏｓｉｔｙｌｅｓｓｔｈａｎ80 % [1] ｃａｎｅｎｈａｎｃｅｔｈｅｈｅａｔｔｒａｎｓｆｅｒ ,ｂｕｔｔｈｅｆｌｏｗｒｅｓｉｓｔａｎｃｅｉｎｃｒｅａｓｅｓｑｕｉｌｅｆａｓｔｅｒ .Ｉｔａｆｆｅｃｔｓｉｔｓｕｓｅｉｎｐｒａｃｔｉｃｅ.Ｔｈｅ ｐｒｅｓｅｎｔｓｔ…     

Combustion of a substitution fuel made of cardboard and polyethylene: influence of the mix characteristics—modeling

The model proposed in this paper describes the combustion of a porous medium subjected to a radiative heat flux at its surface. There is no forced convection of air through the medium; hence this situation corresponds to the one encountered at the surface of fuel elements such as pellets, bricks or ballots, inside a furnace or kiln. Ash is not removed from the surface. No assumption is made a priori in terms of the limiting phenomena. The medium is composed of cardboard and polyethylene (PE). Based on previous experimental work (Fuel 2004; 83 :451–462), the material is assumed to be a macroscopically homogeneous porous medium. Local thermal equilibrium is also assumed. Most of the parameters required for the modeling were determined from specific experiments. Good predictions of the sample mass evolution and of the temperature levels inside the sample body were obtained for a large range of densities and PE content. A devolatilization front of about 20 mm first propagates inside the medium. The volatile matter flux is advected to the surface, which leads to the formation of the flame above the surface. Then a second char oxidation front propagates, starting from the surface. The front thickness is approximately 25 mm under the experimental conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

多孔介质构造应力驱油的固流耦合分析

构造应力场是控制油气运移、聚集最重要的因素之一。依据连续介质力学理论，从理论上分析构造应力驱油的机理，应用孔隙压力和有效应力的概念，阐述了将多孔介质中的平均应力作为固体骨架和孔隙流体之间耦合桥梁的合理性。在柴达木盆地西部南翼山地区的构造应力场和油气运移聚集规律的数值模拟中，采用有限元数值模拟方法，用平均应力推导出孔隙介质中等效的流体压力和流体势，并用达西定律解出由构造应力作用引起的流体运移速度矢量场，为预测有利油气聚集区提供了依据。     

Polyaniline/polyimide blends as gas sensors and electrical conductivity response to CO–N2 mixtures

The effects of dopant type, doping level, polyimide (PI) content and temperature on electrical conductivity response of polyaniline (PANI) and polyaniline/polyimide (PANI/PI) blends to CO–N₂ gas mixtures were systematically investigated. At the same doping level, HNO₃‐doped PANI has a greater electrical conductivity response and sensitivity towards CO than that of camphor sulfonic acid (CSA)‐doped PANI because the former has a more ordered structure. The interaction mechanism between CO and PANI is proposed to occur at the attack site, ? N?H? or the amine nitrogen where CO withdraws an electron. Addition of PI causes a small change in electrical conductivity under atmospheric conditions when PI content is below the percolation threshold value of 55 wt%. Addition of PI reduces brittleness and improves electrical conductivity sensitivity towards CO; the effect is more pronounced at higher temperatures. Copyright © 2005 Society of Chemical Industry     

Frequency Shifts of Luminescence for ZnO Nanoparticles in Porous Alumina Template

ZnO nanoparticles in porous anodized alumina were fabricated by sol-gel method. The PL spectra of pure ZnO nanoparticles, porous alumina template and the ZnO/PAA composite system were investigated after annealed at different temperatures. The annealing of ZnO/PAA composite system displays very complicated behavior, where changing of luminescence intensity and a "red shift" of emission frequency were observed at less or higher than 500 ℃ of the annealing temperature, respectively. To explain the phenomenon, it is considered that the emission origin of the green luminescence of ZnO nanoparticles came from OZn. It is suggested that the ZnO/PAA composite system should be annealed at the temperature above 500 ℃ in order to get intense luminescence of ZnO nanoparticle.