分类： 物理学 >> 凝聚态:结构、力学和热性能 提交时间： 2016-07-12
摘要： A robust solid state diffusion joining technique for SiC ceramics was designed with thickness-controlled Ti interlayer formed by Physical Vapor Deposition method and joined by Electric Field-Assisted Sintering Technology. The interface reaction and phase revolution process were investigated in details, and was analyzed in term of equilibrium phase diagram and also concentration-dependent potential diagram of Ti-Si-C ternary system. Interestingly, on the same joining conditions (fixed temperature and annealing duration), the thickness of Ti interlayer determined the concentration and distribution of reactants of Si and C elements in the resultant joint layer, and the respective diffusion distance of Si and C into Ti interlayer dramatically differentiated during the short joining process (only 5 min). In the case of 100nm thickness Ti interlayer, the C concentration saturated quickly in the joint layer and benefited the formation of TiC phase and following Ti3SiC2 phase. When the Ti thickness increase to 1μm, Si atoms easily diffuse through the diluted Ti-C alloy (dense TiC phase not formed), and amount of Ti5Si3 brittle phase was preferential formed. When the thickness of Ti interlayer is 100nm, SiC ceramics were successfully joined at low temperature of 1000°C for 20min with a flexural strength of 168.2MPa which satisfies the application in corrosion environment. All above findings revealed the importance of diffusion kinetics of reactants on the final composition in the solid state reaction, especially in the joining technique for the covalent SiC ceramics. The well-controlled composition in the joint layer of SiC couples will find its application merits in the harsh service environments, such as nuclear cladding for accident-tolerant fuel (ATF) in the environment of steam corrosion, high neutron irradiation, high temperature, etc.).
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