Tailored Porosity Gradients via Colloidal Infiltration of Compression-Molded Sponges

A technique for producing ceramic preforms with graded porosity via colloidal infiltration of molded polymer sponges has been developed. Polymer sponges have been compression molded into various shapes with continuous and/or stepwise gradients in porosity. Infiltration of the graded sponge with ceramic slurry, followed by pyrolysis of the sponge and sintering of the ceramic, produces a ceramic component with graded porosity. A relationship between compressive strain and the volume fraction of porosity in the sponge has been derived and compared to measured values. The applicability of this technique to the manufacture of planar and axisymmetric composite shapes is demonstrated.