采用Ta2O5为晶核剂制备Li2O·Al2O3·4SiO2-Ta2O5微晶玻璃, 并研究其分相、析晶机理, 构建晶化模型. 结果表明Ta2O5能有效促进玻璃的体积析晶, 获得了晶粒尺寸为50nm的精细组织. 非等温动力学计算显示随Ta2O5含量增加, 析晶活化能降低, 析晶指数增加, 析晶动力学参数K(Tp)作为析晶判据更为合理. 研究发现, LAST玻璃冷却时因亚稳分解导致互锁分相, 形核前期又借助成核生长机制发生微滴分相, 晶体生长则在继承亚稳分相形貌基础上发生“他形”析晶. 最终构建了LAST微晶玻璃的晶化模型.
Li2O·Al2O3·4SiO2-Ta2O5 glass-ceramics were prepared with Ta2O5 as nucleating agent, and the phase separation and crystallization mechanism were investigated. The results show that addition of Ta2O5 promotes internal crystallization effectively, which result in fine-grained microstructure with dimension of 50nm. The non-isothermal crystallization kinetics indicates that the crystallization activation energy decrease and crystallization index increase apparently with increasing amount of Ta2O5, the parameter of K(Tp) is recommended as a better crystallization criterion. It is considered that spinodal decomposition occur primarily and result in an interlocking phase separation on cooling of glass, metastable droplet phase separate by nucleation and growth mechanism upon reheating process, then, “anhedral” crystallization takes place and inherits the morphology of the original phase separation. Consequently, the crystallization model of LAST glass-ceramics is put forward successfully.
参考文献
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