Fabrication of hierarchically porous Si₃N₄ foam ceramics with stamen-like cell structure

Inspired from the stamen structure in nature, hierarchically porous Si ₃N₄ foam with stamen-like cell structure is fabricated by using egg white protein as pore forming agent in the gel casting process. Macropores with micro-interconnected pore on the wall are present which have average pore size of 0.36 μm and 10-400 μm. Graded rod-shaped Si ₃N₄ grains, finer ones with aspect ratios of 10 on the wall and longer ones with aspect ratios of 20 in the interior of the macropores, are synthesized. Such porous Si₃N₄ exhibits good mechanical property, relatively high strength (11.9 MPa) and high porosity (81.7%), indicating it is a potential high-temperature separation materials.