Processing of porous mullite ceramics using novel routes by starch consolidation casting

In this article, the development and characterization of porous mullite bodies prepared using two novel forming routes with native starches were studied with the aim of developing bodies without deformation and with homogeneous porous microstructures. Mullite–starch suspensions specific for each route were prepared by mixing and characterized by measuring viscosity. Mullite green bodies were fabricated by heating the suspensions in metallic molds and by burning out the starch, while final porous materials were obtained by sintering at different temperatures. Bodies obtained before and after the burning-out process, and sintered disks, were characterized with porosity measurements and microstructural analysis by SEM. The phases generated after the sintering process were determined by XRD, and pore size distributions were studied by Hg-porosimetry. The obtained results showed that the use of both routes allowed the shaping of homogeneous mullite bodies without causing cracks or deformations and the consequent development of controlled porous mullite microstructures.