Porous mullite ceramics from national clay produced by gelcasting

Gelcasting process has been successfully employed to fabricate porous mulli te ceramics in this work. The specimens based on mullite composition are fo und with open porosity of 58.5-63.9%. mean pore size of 0.7-1.31 mum, and n itrogen permeability of 526-1240 m(3) m(-2) bar(-1) h(-1) by reactively sin tering the gelled mixture of kaolinite and aluminum hydroxide at 1300-1600 degreesC. The porosity, mean pore size, pore size distribution and gas perm eability can be controlled by adjusting raw material ratios and sintering t emperatures. The gas permeability of the specimens is found to be more depe ndent on the average pore size than on the open porosity. In addition, the gas transportation mechanism in porous mullite ceramics is dominated by lam inar flow when the specimens are fired at high temperatures. (C) 2001 Elsev ier Science. Ltd and Techna S.r.l. All rights reserved.