Preparation of Porous LiAl5O8 by Reaction bonded sintering

Abstract

The porous LiAl₅O₈ was fabricated by the reaction bonded sintering process. Powders of Al₂O₃ (0.3mm) and Li₂O (1.0 mm) were used as starting materials. They were mixed with ratios of Al₂O₃ and Li₂O in 5:1, 7:3 and 5:5 by mole in the water for 6 hours and were dried at 100^oC for 10 hours. The mixed powder was pressed to form a 10 mm diameter disk specimen. The disk specimens were then sintered at temperatures of 1300^oC for 2 hours. Specimens sintered at 1300^oC for two hours formed two kinds of lithium aluminates, namely LiAlO₂, and the LiAl₅O₈ in the mixture with the ratios of 7:3 and 5:5. The mixture with the ratio of 5:1 formed only the LiAl₅O₈ phase. The specimen mixed by 5:1 molar ratio had a homogeneous grain size and a pore size distribution. The Li₂O reacted completely with the Al₂O₃ even below the evaporation temperature of the Li₂O. In the specimen mixed by 5:5 ratio, the pore of specimens was larger and longer which would be resulted from the evaporation of Li₂O during the sintering process. The thermal expansion coefficient of the specimen mixed by 5:1 molar ratio was lower than that of the specimen with other mixing ration.