Processing of microcellular mullite

A new processing route for manufacturing partially interconnected open-cell, microcellular mullite ceramics has been developed. The strategy adopted for making microcellular mullite ceramics entailed the following steps: (i) fabricating a formed body from combining polysiloxane, Al2O3 (a reactive filler), polymer microbeads (used as sacrificial templates), and Y2O3 (a sintering additive); (ii) cross-linking the polysiloxane in the formed body; (iii) transforming the polysiloxane by pyrolysis into SiO2; and (iv) synthesizing mullite by reacting SiO2 and Al2O3. By controlling the sintering temperature and the microbead and additive contents, it was possible to adjust the porosity so that it ranged from 38% to 85%. The compressive strengths of the microcellular ceramics with similar to 40% and similar to 70% porosities were similar to 90 and similar to 10 MPa, respectively. The superior compressive strengths were attributed to the homogeneous distribution of small (<= 20 mu m), spherical cells with dense struts in the microcellular ceramics.