Silicon carbide-based foams from direct blowing of polycarbosilane

Macro-cellular porous silicon carbide foams were produced using a polycarbosilane preceramic polymer and a chemical blowing agent (azodicarbonamide). Polycarbosilane (PCS) was mixed with a blowing agent and the mixture was foamed close to the melting point of PCS at 250–260 °C, under nitrogen in order to avoid cross-linking by oxidation. The foamed PCS was then cured under air at 200 °C and pyrolyzed at 1000 °C, leading to the formation of open macro-cellular ceramic components. Porosity ranged from 59 to 85 vol%, and the cell size ranged from 416 to 1455 μm; these values could be modulated by changing the content of blowing agent and foaming temperature. This process is a simple and efficient way to produce silicon carbide-based foam with tailored pore architecture and porosity.