The Study on Fabrication of LAS System Ceramics for Thermal Shock Resistance from Silicate Minerals: (I) Preparation of Eucryptite Powders with Sillimanite Group, Kaolin Group Minerals

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J. Korean Ceram. Soc. > Volume 31(5); 1994 > Article

Journal of the Korean Ceramic Society 1994;31(5): 572.

실리케이트 광물을 이용한 내열충격성 LAS계 세라믹스의 제조에 관한 연구: (I) Sillimanite와 Kaolin족 광물을 이용한 Eucryptite 분말합성

박한수, 조경식¹, 문종수

경남대학교 무기재료공학과
¹연세대학교 세라믹공학과

The Study on Fabrication of LAS System Ceramics for Thermal Shock Resistance from Silicate Minerals: (I) Preparation of Eucryptite Powders with Sillimanite Group, Kaolin Group Minerals

ABSTRACT

With low thermal expansion coefficients, eucryptite (Li2O.Al2O3.2SiO2) and spodumene (Li2O.Al2O3.4SiO2) in LAS ceramic system show good thermal shock resistance. In this study, sillimanite or kaolin group silicate minerals and Li2CO3 were used as starting materials, and if necessary SiO2 or Al2O3 were added for making stoichiometrically formed specimens. By this process, eucryptite powders were synthesized and characterized. The powder mixtures of lithiumcabonate and silicate minerals calcined at 80$0^{circ}C$ for 2 hrs were made into powder compacts. $beta$-Eucryptite single phase was formed via intermediate phases of Li2SiO3 and LiAlO2 et al, by heating at 110$0^{circ}C$ or 120$0^{circ}C$ for 10 hrs from those powder compacts. When using the sillimanite group minerals, Virginia kyanite or andalusite was reacted to form eucryptite at 120$0^{circ}C$and CMK International kyanite were completed at 110$0^{circ}C$. When kaolin group minerals were used, it was found that the synthesizing temperature (100$0^{circ}C$) of $beta$-eucryptite from the mixture of New Zealand white kaolin was lower than that from Hadong pink kaolin (110$0^{circ}C$). The Microstructure of systhesized powder showed the irregular lump shape such as densed crystallines.