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101.
102.
Jae Ryong Kim Do-Hyeong Kim Chong Hee Kim 《Journal of the American Ceramic Society》1990,73(8):2567-2569
The effects of ZrO2 and Y2 O3 on the densification of hotpressed Si3 N4 -Zr(Y)O2 composites have been studied. High density could not be obtained by the addition of pure or 3-mol%-Y2 O3 -doped ZrO2 in this composite; however, nearly full density (>97%) could be obtained in Si3 N4 using 6- and 8-mol%-Y2 O3 -doped ZrO2 . It is concluded that Y2 O3 diffusing out from the added Zr(Y)O2 promoted the densification and that ZrO2 also had some role in the formation of an oxynitride glass. 相似文献
103.
104.
直接凝固注模成型Si_3N_4及SiC陶瓷──基本原理及工艺过程 总被引:10,自引:3,他引:10
直接凝固注模成型(directcoagulationcasting,DCC)是一种崭新的(准)净尺寸陶瓷成型方法。本文报道了采用此法成型Si_3N_4及SiC陶瓷的基本原理和工艺过程。DCC成型工艺过程为把高固相含量低粘度的陶瓷浆料浇注到无孔模具中,事先加入到浆料中的生物酶及化学物质通过改变浆料的pH或电解质浓度来改变浆料的胶体化学行为,从而使浆料原位凝固,得到有足够脱模强度的陶瓷坯体。DCC成型的特点为坯体密度高(理论密度的55%~70%),坯体均匀,不用或只需少量的有机添加剂(少于1%),可成型大尺寸、复杂形状、高可靠性的陶瓷部件。 相似文献
105.
A model is developed to address the uniformity of displacement deposition of nickel inside porous silicon with an ultrahigh aspect ratio as high as 200. The nickel distribution is treated as a current distribution issue as in electrodeposition. It is shown that the deposition distribution along the pore depth exhibits a strong dependence on a polarization parameter ξ. High values of ξ correspond to mass transport limitations and lead to non-uniform distributions, whereas small ξ values, representing interfacial reaction control, produce uniform distributions. Non-uniform deposition primarily occurs at an initial stage in which the reaction is dominated by mass transfer. As the deposition process continues, the deposition rate drops to a low value, and the deposition uniformity shifts from Ni2+ mass transport limitations to its interfacial reaction control, leading to uniform Ni2+ concentration and deposition rate distributions. It is predicted that the non-uniformity at the initial stage could be remedied by increasing the bulk concentration of the nickel ions and decreasing the plating bath pH. In addition, the uniformity of the deposition distribution can be significantly improved by introducing inhibiting additive coumarin to the plating solution. 相似文献
106.
Tateoki Iizuka Hideki Kita Hideki Hyuga Takene Hirai Kazuo Osumi 《Journal of the American Ceramic Society》2004,87(3):337-341
A W2 C-nanoparticle-reinforced Si3 N4 -matrix composite was fabricated by sintering porous Si3 N4 that had been infiltrated with a tungsten solution. During the sintering procedure, nanometer-sized W2 C particles grew in situ from the reaction between the tungsten and carbon sources considered to originate mainly from residual binder. The W2 C particles resided in the grain-boundary junctions of the Si3 N4 , had an average diameter of ∼60 nm, and were polyhedral in shape. Because the residual carbon, which normally would obstruct sintering, reacted with the tungsten to form W2 C particles in the composite, the sinterability of the Si3 N4 was improved, and a W2 C–Si3 N4 composite with almost full density was obtained. The flexural strength of the W2 C–Si3 N4 composite was 1212 MPa, ∼34% higher than that of standard sintered Si3 N4 . 相似文献
107.
合成二氧化硅对硅橡胶性能的影响 总被引:5,自引:0,他引:5
介绍了合成二氧化硅及硅橡胶的结构性质,探究了二氧化硅的结构性质对硅橡胶补强性能的影响,指出了二氧化硅颗粒的大小、形态、聚结状态、表面性质和与高分子硅氧烷之间的相互作用是影响二氧化硅对硅橡胶补强性能的最主要的因素,并用实验对硅橡胶的硬度、拉伸强度、300%定伸应力、扯断伸长率、撕裂强度、压缩永久变形等物理性能进行测定,结果表明:BET比表面积180~200m^2/g,孔隙度(吸油量)为3.0~3.2mL/g,平均粒径为8~10岬的沉淀法白炭黑对硅橡胶具有很好的补强效果。 相似文献
108.
Electrochemical ferrate generation for waste water treatment using cast irons with high silicon contents 总被引:5,自引:0,他引:5
This paper deals with the electrochemical preparation of ferrate in 15 M NaOH media, with a view to treatment of waste waters. Grey cast irons with high silicon contents were shown to allow current yields in the range 20–40% depending on the applied current density, up to 34 mA cm–2. Ferrate solutions with contents up to 0.08 M could be produced in a divided cell of simple design, and provided with flat or packed-bed electrodes. Deactivation of the anode surface was shown to be of moderate significance for hour-long runs. The ferrate produced was tested for treatment of industrial liquid wastes: coagulation efficiency of the suspended matter was comparable with that of an electrocoagulation process with sacrificial Al anodes. The potential of waste water treatment by addition of ferrate is discussed. 相似文献
109.
In previous work, we developed a highly active bimetallic platinum–ruthenium catalyst supported on a very high surface area activated carbon substrate. In fixed bed reactors, this catalyst proved capable of the continuous long-term deep oxidation of a variety of aqueous organic contaminants associated with spacecraft wastewater streams at 121 °C. This work was extended to the mineralization of more typical environmental contaminants, including halocarbons and aromatics. The primary weakness of this catalyst was the tendency toward relatively high rates of chemical decomposition. To overcome this limitation, methods were developed for the production of a silicon carbide coating over the surface of the activated carbon, yielding a reasonable trade-off between increasing resilience and decreasing surface area. Here we report the catalytic decomposition of dissolved organic contaminants at 130 °C using this silicon carbide/activated carbon supported bimetallic catalyst. 相似文献
110.