Polymer derived ceramic foams with additional strut porosity

Abstract

Ceramic foams with additional strut porosity were prepared by a self-foaming process of a polysilsesquioxane. The strut porosity was generated by adding sacrificial pore formers comprising of polymethylmethacrylate or of polyethylene to the self-foaming silicone. The polymer-inherent shrinkage was reduced by adding SiC particulate fillers to the silicone/pore-former mixture. Foaming was carried out on a preheated furnace at 270 °C, and subsequent pyrolysis was performed in argon atmosphere in the temperature range from 800 °C to 1200 °C in order to trigger the polymer-to-ceramic transformation of the polysilsesquioxane. The materials were characterized with respect to the pore size and the total porosity, the microstructure and the mechanical strength. The volumetric mean pore diameter of the strut ranged from 25 μm to 100 μm and the porosity was found to be 40% to 94%. The maximum compression strength exceeded 16 MPa.