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Fabrication of Porous Silicon Carbide for Environmental Use based on Free Energy Theory

基于自由能理论的环保用多孔碳化硅的制备

基本信息

批准号：
15560592
负责人：
TANAKA Hidehiko
金额：
$ 1.79万
依托单位：
National Institute for Materials Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

We developed silicon carbide porous materials in order to apply to environmental use. We noticed that grain growth of fine powder made possible to fabricate porous materials.First, we reorganized that sintering and grain growth theory in the fabrication of ceramics was important as basic science. Therefore, we proposed free energy theory for material transport. In the theory, a rate of diffusion was proportional to excess free energy, a diffusion constant and a geometry factor. The theory was totally different from traditional sintering and grain growth established so far. We could analyze from this theory the role of surface energy and other free energies on the material transport.Second, we investigate new compounds that accelerated diffusion constant and found Al-B-C compounds. The compounds decreased sintering and grain growth temperatures, and also enabled us to use a sophisticated hot isostatic pressing (HIP) resulting in fabricating completely dense silicon carbide.Third, we studied silicon carbide and metal boride composites, and characterized grain growth and densification behavior. Some of metal borides elongated SiC particles.Finally, from these results, we tried to make porous material utilizing transformation induced material transport and diffusion accelerated grain growth. We used two types of silicon carbides different in crystal structure and used the Al-B-C additives that we already found. The raw powders behaved initial grain growth accelerated by surface energy and then final large grain growth due to crystal transformation. We succeeded in fabrication of strong porous silicon carbide materials having about 50% porosity and 100 MP strength that are suitable environmental use.

我们开发了碳化硅多孔材料，以应用于环境用途。我们注意到细粉的颗粒长大为制备多孔材料提供了可能。首先，我们重新梳理了陶瓷制备中的烧结和颗粒长大理论作为基础科学的重要意义。因此，我们提出了物质输运的自由能理论。在该理论中，扩散速率与过剩自由能、扩散常数和几何因子成正比。这一理论与目前所建立的传统烧结和晶粒长大理论完全不同。从这个理论出发，我们可以分析表面能和其他自由能在物质输运中的作用。其次，我们研究了加速扩散常数的新化合物，发现了Al-B-C化合物。这些化合物降低了烧结和晶粒生长温度，还使我们能够使用复杂的热等静压(HIP)工艺来制备完全致密的碳化硅。第三，我们研究了碳化硅和金属硼化物复合材料，并对其晶粒生长和致密化行为进行了表征。最后，根据这些结果，我们尝试利用相变诱导的物质输运和扩散来制备多孔材料，从而加速了颗粒的生长。我们使用了两种不同晶体结构的碳化硅，并使用了我们已经发现的Al-B-C添加剂。原始粉末表现为由表面能加速的初期晶粒长大，再到晶化转变后的大颗粒长大。我们成功地制备了孔隙率约为50%、强度约为100MP的适合环境使用的硬质多孔碳化硅材料。