Porous MgAl
2O
4 ceramics were fabricated by impregnating porous Al
2O
3 bodies calcined at 1250℃ with Mg(NO
3)
2 saturated aqueous solution under reduced pressure, followed by firing at 1500℃. Porous Al
2O
3 bodies with continuously long-ranged pore structure and cross-linked one were prepared by a unidirectional freeze casting using aqueous Al
2O
3 slurries containing urethane latex binder (ULB) and water-soluble binder (PVA), respectively. The effect of the micro structure of Al
2O
3 bodies on MgAl
2O
4 formation was investigated. In the case of the porous Al
2O
3 body with continuously long-ranged pore structure, the amount of MgAl
2O
4 formed on firing at 1500℃ was larger than that for the porous Al
2O
3 body with cross-linked pore structure and a single-phase MgAl
2O
4 porous ceramic was obtained by four times impregnation. However, in this case, the surface of the porous Al
2O
3 body peeled off gradually with repeating impregnation. On the other hand, in the case of the porous Al
2O
3 body with cross-linked pore structure, about 10% Al
2O
3 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 Al
2O
3 bodies but it was difficult to make the solution of Mg(NO
3)
2・6H
2O into the small pore, resulting in a decrease in the rate of formation of MgAl
2O
4.
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