【摘要】 采用高温融熔法制备SiO2-Al2O3-MgO-F系可加工玻璃陶瓷基础玻璃,应用XRD、SEM和EP MA等方法对不同预处理条件下样品晶体种类、显微组织进行分析,研究不同预处理条件下云母晶体的析出机制.结果表明:在相同组成的玻璃体系中,由于预处理条件的不同,导致了云母晶体以不同的析出机制析出,并且在不同的析出机制下,云母晶体的形态有着显著的差异.在快速升温的情况下,针状云母晶体在试样表面直接形核,相互平行的云母晶体几乎垂直于试样表面向中心长大;当试样预先在分相区处理后再加热到析晶温度时,针束状云母晶体以分相时形成的晶体为异质核心,呈相互交错方式长大;而当试样在过渡相析出区处理后再加热到析晶温度时,片状云母晶体呈相互交错状以异质外延长大机制析出.更多还原

【Abstract】 The base glass on the SiO2-Al2O3-MgO-F machinable glass-ceramic was prepared by melting the mixture of reagent-grade chemicals of SiO2, Al2O3, MgO and AlF3. The effect of different pre-treatments on crystallization mechanism, microstructures and morphology of mica crystalline were investigated by using XRD, SEM and EPMA. It was found that in the glass system studied pre-treatments had important influences on the mica phase crystallizing mechanism, three kinds of which were observed, and had influences on the microstructures and morphology of mica crystalline. In the isothermal processes, during the which glass samples were heated to quickly pass the ranges of phase-seperation and transient phases precipitation, it was suggested that the growth of mica crystalline appeared dominately to be a needle-like manner following a surface-induced mechanism; While the base glass was annealed at temperature range of phases-seperation prior to crystallization process, needle-like mica was also crystallized but it was tended to precipitate in the whole body by the heterogeneous nucleus formed in the annealing processes; However, when the crystallization processs was preceded with the precipitation of transient phases, flake-like mica was crystallized through epitaxial growth and blocky mica was then found.更多还原