Aqueous gelcasted ZrB2-SiC foams derived from composite poring mechanisms

ZrB2-SiC foams were prepared from composite poring mechanisms of foaming and solid poring (PAA beads) by the application of a gelcasting technique. The porosities and microstructures of sintered bulks were tailored through changing the solids loading of slurries and the amount of added PAA beads. The increase in solid loading caused high viscosities of slurries, and thus resulted in the reduction of porosity and a tendency to form close pores. With increasing the amount of PAA beads, high porosities (up to 91.4%) and obvious connectivity improvement between bubble-derived pores emerged owing to efficient foaming and presence of bead-derived pores. As the porosity increased, the compressive strength (0.4-8.2 MPa) decreased, and the gas permeability (9.7-62.1×10−12 m2) augmented because of the effects of bead-derived pores and the increase in window number and size of bubble-bead pores.