溶液含浸法によるスピネル多孔体の作製におけるアルミナ骨格の微細構造の影響

Abstract

Porous MgAl2O4 ceramics were fabricated by impregnating porous Al2O3 bodies calcined at 1250℃ with Mg(NO3)2 saturated aqueous solution under reduced pressure, followed by firing at 1500℃. Porous Al2O3 bodies with continuously long-ranged pore structure and cross-linked one were prepared by a unidirectional freeze casting using aqueous Al2O3 slurries containing urethane latex binder (ULB) and water-soluble binder (PVA), respectively. The effect of the micro structure of Al2O3 bodies on MgAl2O4 formation was investigated. In the case of the porous Al2O3 body with continuously long-ranged pore structure, the amount of MgAl2O4 formed on firing at 1500℃ was larger than that for the porous Al2O3 body with cross-linked pore structure and a single-phase MgAl2O4 porous ceramic was obtained by four times impregnation. However, in this case, the surface of the porous Al2O3 body peeled off gradually with repeating impregnation. On the other hand, in the case of the porous Al2O3 body with cross-linked pore structure, about 10% Al2O3 remained after four times impregnation, but the structural disintegration caused by repeating impregnation was not observed. The cross-linked pore wall was effective to increase the strength of the calcined porous Al2O3 bodies but it was difficult to make the solution of Mg(NO3)2・6H2O into the small pore, resulting in a decrease in the rate of formation of MgAl2O4.