A synergetic poring strategy to prepare high porosity SiC ceramic foam with good mechanical strength

Abstract

Microstructure‐tailored high porosity silicon carbide (SiC) ceramic foams were successfully fabricated using polymeric precursor slurry through a synergetic pore‐forming strategy that combines direct foaming and sacrificial template method together. The slurry is composed of a vinyl‐containing liquid polycarbosilane, poly(methyl methacrylate) (PMMA) microspheres, and composite inorganic fillers. The expandable PMMA served a dual role as both foaming agent and sacrificial template, while the liquid polycarbosilane was used as both binder and preceramic polymer. The green bodies foamed from precursor slurry were pyrolyzed at 1150, 1400, and 1600°C, respectively, to produce corresponding SiC ceramic foams. The pyrolysis behavior of the green body foams and the crystallization behavior of the SiC ceramic foams were studied. Notably, the SiC ceramic foam derived from the slurry containing 65 wt% filler exhibited low density (0.26 g/cm3), high porosity (90.3%), high compressive strength (3.87 MPa), and low thermal conductivity (0.34 W/mK). The SiC ceramic foams displayed attractive oxidation resistance, and the foams with a porosity of 90.3% can retain 75.2% of their initial compressive strength after oxidation for 10 h at 1400°C.