Study On The Crystallization Kinetics, Microstructure And Properties Of B₂O₃-Al₂O₃-SiO₂ Glass-ceramics

B₂O₃-Al₂O₃-SiO₂ (BAS) glass-ceramics have the advantages such as lower thermal expansion cofficient, high chemical stability, good dielectric properties, which make it potential applications in the fields of electronics, information, mechanical and chemical engineering. The crystallization kinetics of BAS glass has been analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The kinetic parameters such as crystallization activation energy were calculated by Ozawa and K method. The influences of B2O3/SiO2 ratio and different alkali earth metal oxides MO (M= Ba, Mg, Ca) on the crystallization behavior of BAS glass were investigated by means of DSC, XRD, SEM(Scanning Electron Microscope). The crystal phases, microstructure, thermal expansion and strength of BAS glass-ceramic were characterized.The values of crystallization activation energy of BAS glass calculated by Ozawa and K method are similar to each other, and have the same varying tendency. With the reduction of B2O3/SiO2 ratio, the crystallization activation energy increases at first and then decreases, but the crystallization temperature increases straightly. The crystallization activation energy reaches the minimum value of 375.4E/kJ·mol-1 when the B2O3/SiO2 ratio is 2.2. The crystalline index(n) are all more than 4, which indicates that the glass-ceramic system is in bulk crystallization.There is evident effect of different alkali earth metal oxides on the crystallization behavior of BAS glass. The crystallization activation energy of the glass containing CaO is the smallest, while that of the glass containing MgO is the biggest. The addition of nucleation agent TiO2 can improve the ability of crystallization. When the glass was heated at 800℃, the primary crystalline phase was Al4B2O9, and with the temperature increased to 1100℃, Al18B4O33 and Al5BO9 appeared and became the major crystalline phases. With the decrease of B2O3/SiO2 ratio, the density of the glass-ceramic decreased a little, but all of the samples show good properties at high temperature, lower thermal expansion coefficient (5.20×10-6/℃) and higher softening point (1180¹190℃).The optimal crystallization parameters of BAS glass prepared by melting technique should be heated at a speed of 5℃/min to 800⁸50℃and holding for 5h, then heated to 1100℃and holding for 2h. The glass-ceramics obtained using the heating schedule has superior microstructure and properties.