Preparation of Glass-Ceramics in $Li_2O-Al_2O_3-TiO_2-SiO_2$ System by Sol-Gel Technique : (II) Crystallization of $Li_2O-Al_2O_3-TiO_2-SiO_2$ Monolithic Gel Prepared by Sol-Gel Method

Sol-Gel 법에 의한 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 다공성 결정화 유리의 제조 : (II) Sol-Gel 법에 의해 제조된 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 괴상겔의 결정화

The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.