TAILORED POROSITY GRADIENTS VIA COLLOIDAL INFILTRATION OF COMPRESSION-MOLDED SPONGES

A technique for producing ceramic preforms with graded porosity via co lloidal infiltration of molded polymer sponges has been developed. Pol ymer sponges have been compression molded into various shapes with con tinuous and/or stepwise gradients in porosity. Infiltration of the gra ded sponge with ceramic slurry, followed by pyrolysis of the sponge an d sintering of the ceramic, produces a ceramic component with graded p orosity. A relationship between compressive strain and the volume frac tion of porosity in the sponge has been derived and compared to measur ed values. The applicability of this technique to the manufacture of p lanar and axisymmetric composite shapes is demonstrated.