2.1材料概论-陶瓷双语分析.ppt

* * * * * * * * Medical: Bioceramic materials: are used for repair and replacement of human hips, knees, and other body parts. Ceramic materials: can stimulate bone growth, promote tissue formation and provide protection from the immune system. Environmental and Space Applications To decrease pollution, capture toxic materials and encapsulate nuclear waste; Catalytic converters in trucks and cars are made of cellular ceramics and help convert noxious hydrocarbons and carbon monoxide gases into harmless carbon dioxide and water. Advanced ceramics: used in diesel and automotive engines: Its light-weight, high-temperature and wear resistant properties results in more efficient combustion and significant fuel savings. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Open porosity开口孔 refers to the network of pores in a material that is open to the surface and into which a liquid such as water can penetrate渗透 if the part were submerged浸入init. Closed porosity闭口孔 refers to those pores that have become sealed within the grain structure. * Pores affect the strength of ceramics in two ways： First，they produce stress concentrations应力集中. Once the stress reaches a critical level, a crack will form and propagate扩展. Second，pores reduce the cross-sectional areas over which a load can be applied and, consequently, lower the stress that these materials can support. * The amount, size, distribution分布, and the continuity 连续性 of voids空隙 in a ceramic are the principal factors that determine its properties In general，porosity is detrimental 有害的 to ceramics properties. Grain boundary晶粒界线 sliding, creep rate, and chemical reactions that attack the ceramic or reduce its melting point are more adverse不利的 conditions produced by impurities and porosity. * * 收缩 a 收缩 b 收缩 无气孔的 多晶体 c 说明： a: 颗粒聚集 b: 开口堆积体中颗 粒中心逼近 c: 封闭堆积体中颗 粒中心逼近 3.3 Ceramic Processing Traditional Processing structural clay products and the whitewares. Formation → Drying → Firing 成型 Forming：