Cao-mgo-al <sub> 2 </ Sub> O <sub> 3 </ Sub>-sio <sub> 2 </ Sub> Glass-ceramics

In this paper, the development, classification, fabrication technology and application of glass-ceramics were systematically reviewed. A white glass-ceramics of CaO-MgO-A1203-Si02 system was prepared by melting with quartz, dolomite and calcite as the starting materials and fluoride as nucleation agent. The major crystalline phases are wollastonite(~3-CaSiO3) and diopside(CaMg(Si03)2). The phase compositions of the glass-ceramics were analyzed by XRD, and its microstructures were observed by SEM. Cooled glass is milky white and opaque. SEM observation showed that phase separation takes place in the glass. After heat treatment, homogeneous particles with the size of about i000A serve as nucleation agent. Around them, wollastonite and diopside gradually deposit and grow. Experiments showed that CaF2 can effectively prompt crystallization of the glass. With the increase of CaF2 content, crystallization temperature of the glass decreases and its crystallizing ability increases. Wollastonite decreases and diopside increases in the glass-ceramics after heat treatment. With the decrease of CaOfMgO, crystallization temperature and the content of diopside increase, resulting in the improvement of its mechanical properties. A glass-ceramics with bending strength of 245MPa, hardness of ll.1SGPa and wear resistance of O.1401g/kg.h was prepared with CaOIMgO ratio of 5. Good mechanical properties of the glass-ceramics are related with its homogeneous and dense microstructure. In this material, flake and granular crystals are interlaced. Heating conditions have obvious influence on the glass-ceramics. In this work, the optimal crystallization parameters are 9400C and holding 2h. The heating rate is: 6C/min before 650扖, 40C/min between 6500C and 8400C, 20C/min between 840C and 9400(2.