Silicon nitride foams from emulsions

Si3N4 foams with open cells were developed by emulsification of an aqueous powder suspension containing an alkane phase (70 vol% of octane or decane), using a surfactant as emulsion stabilizer. 5 wt% of Y2O3 and 5 wt% of MgO were used as sintering additives, and the samples were pressureless sintered at 1600 °C in N2. Ceramic foams, mainly based on α-Si3N4, with total porosity ranging from ~70 to ~77 vol%, average cell size of ~31 μm for octane and ~55 μm for decane, and compression strength ranging from ~5 to ~20 MPa were produced.