FABRICATION OF POROUS MULLITE BY FREEZE CASTING AND SINTERING OF ALUMINA-SILICA NANOPARTICLES

摘要

Porous mullite with interconnected porous microstructure is fabricated by freeze-casting and sintering of alumina-silica nanoparticles. The initial alumina and silica nanoparticle concentrations that are the same as mullite composition (3Al_2O_3-2SiO_2) lead to the finest microstructure and the highest porosity (～69%) compared to either alumina-rich or silica-rich starting composition. Upon sintering, alumina and silica nanoparticles interact with each other and diffuse together to form the mullite phase at temperatures 1300℃ or higher. The flexural strength of the composite keeps increasing with the increase of the sintering temperature. The fabricated porous mullite possesses improved strength than the porous alumina-silica composite.