Gelcasting fabrication of porous ceramics using a continuous process

A continuous process for gelcasting fabrication of porous ceramics is reported. The key characteristic of this method is the mixing of slurry and N-2 bubbles, formed from a separated canister containing a surfactant prior to foaming of slurry, in a spiral mixer. The microstructure of the resulting porous ceramic is compared with that of sample fabricated by the conventional discontinuous process with N-2-gas controlling system. Porous ceramic produced using the new method displays lower density, higher open and total porosities, and broad pore size distribution. The obtained porous ceramics by the two routes are further investigated by sound absorption and heat insulation tests. Porous ceramic produced using the new method shows higher value of sound absorption coefficients, which suggests that the large porosity augment the sound absorbing performance of ceramics sample. The pore structure could also affect the thermal conductivity of the porous ceramics. With high porosity, sample fabricated with new method displayed lower thermal conductivity. (c) 2005 Published by Elsevier Ltd.