Effects of Processing Parameters on Microstructure and Properties of Nanoscale ZrC/ZrB2 Multilayered Coatings

ZrC/ZrB2 multilayered coatings with bilayer periods of 3.5-40nm are synthesized by rf magnetron sputtering. Analyses of x-ray diffraction, scanning electron microscopy and nanoindentation indicate that multilayered coatings possess much higher hardness and greater fracture resistance than monolithic ZrC and ZrB2 coatings. A maximum hardness （41.TCPa） and a critical fracture load （73.7mN） are observed in the multilayer with A = 32 nm deposited at the substrate bias -40 V. Higher residual stress built in the ZrC layer can be released by periodic insertion of ZrB2 into the ZrC layer. A clear multilayered structure with mixed ZrB2（001）, ZrB2 （002） and ZrC （111） orientations should be responsible for the enhanced mechanical properties.     

Pregelation Behaviour of Coagulation Processes with the Constant-Reaction-Number Kernel

We propose an irreversible binary coagulation model with a constant-reaction-number kernel, in which, among all the possible binary coagulation reactions, only p reactions are permitted to take place at every time. By means of the generalized rate equation we investigate the kinetic behaviour of the system with the reaction rate kernel K（i;j） = （ij）^w （0 ≤w〈1/2）, at which an i-mer and a j-mer coagulate together to form a large one. It is found that for such a system there always exists a gelation transition at a finte time to, which is in contrast to the ordinary binary coagulation with the same rate kernel. Moreover, the pre-gelation behaviour of the cluster size distribution near the gelation point falls in a scaling regime and the typical cluster size grows as （to - t）-1/（1-2w）. On the other hand, our model can also provide some predictions for the evolution of the cluster distribution in multicomponent complex networks.     

^1H自旋扩散方法研究离子化聚氨酯的相态结构

本文用改进的Goldman-Shen脉冲序列研究了聚丁二烯加MDI离子化聚氨酯体系中磁化矢量的自旋扩散过程,通过一些合理的简化,求解了扩散方程,得到了一种可定量的求出多相高聚物微区尺寸的简便方法.     

2003 International Powder／Bulk Conference ＆ Exhibition

Hosted by the Chinese Society of Particuology, China Powder Industry Association and Shanghai Science Technology Exhibition Company, with the sponsorship of Trans Tech Publications, Germany, and the organization of Worldwide Exhi-bitions Service Company, the above Conference/Exhibition, the largest of its kind in China, was held from Nov. 29 to Dec. 1 in Shanghai Mart, Shanghai. More than 100 professional equipment producers and market promotion agencies in powder/bulk handling and p…     

纳米尺寸的ZnO晶体高压相变的拉曼散射研究(英文)

Weperformedthehigh-pressureRaman measurementofthethreenanosizedZnOcrystals. Wefoundthesmallerthesize,thehigherthe pressuretoinducethephasetransitionfrom w櫣rzitetorock-saltstructure. High-pressureRamanmeasurementsof nona-shapedZnOcrystalswerepreformed.The…     

用超声化学法制备有机包覆纳米银

纳米级银粉，以其纳米尺寸所赋予的独特性能，可广泛应用于催化剂材料、电池电极材料、低温材料和导电浆料，探索纳米银粉的制备方法具有重要的意义。2004年，通过超声化学法，在乙二醇介质中、以硝酸银为原料制备出了有机包覆的纳米银。产物用X射线光电子能谱仪（XPS）、透射电子显微镜（TEM）和红外光谱等进行了检测。     

提高YBCO块材在外磁场中悬浮力

本给出了三种提高YBCO块材在外磁场中悬浮力的方法．第一种方法是增强外磁场，对于此方法，本研究了一块直径为30mm的圆柱状YBCO块材分别在圆柱状NdFeB永磁体和NdFeB永磁导轨上的悬浮力．测量结果表明在77K温度下YBCO块在圆柱状NdFeB永磁体上的最大悬浮力为50N，在NdFeB永磁导轨上的最大悬浮力为103．ON．第二种方法是提高YBCO块材自身的性能，包括临界电流密度、俘获磁通和块材尺寸，对于此方法，本仅研究了块材尺寸对悬浮力的影响．三块直径分别为30mm、35mm、40mm的圆柱状YBC0块材在NdFeB永磁导轨上的悬浮力被测量，77K温度下5mm悬浮间距时的悬浮力分别为103．ON、134．5N、175．ON．第三方法是将YBCO块材变成准永久磁体，此种情况下，直径为40mm的圆柱状YBCO块材在77K温度下5mm悬浮间距时的悬浮力高达218．3N．     

二维渗流中的最短开穿透

在二维边渗流模型中，设／ｒｎ／＝ｍｉｎ（／ｒ／：ｒ是正方形「０，ｎ」＾２的开穿透），这里／ｒ／表示ｒ的长度，本文证明了在上临界状态有ｌｉｍＥ／ｒｎ／／ｎ＝λ，在临界状态时，我们对Ｅ／ｎ／给出了上界，并对一个ｒｎｒｎ给出了Ｅ／ｒｎ／的下界。     

高负荷情形开网络的强逼近

本文用强逼近理论,对一般排队网络在高负荷情形下,得到了队长,虚等待时间和顾客在网中逗留时间的强逼近定理.同时还得到了队长嵌入过程的强逼近定理.