Synthesis of porous biomorphic α/β-Si3N4 composite from sea sponge

Biomorphic alpha/beta-Si3N4 composites were produced from natural sea sponge via replication method. The sponges were impregnated with a Si-containing slurry via dip-coating. After coating, the sponges were submitted to oxidation at 600 degrees C for 1 h to decompose the bio-polymers followed by burning out of carbon, leading to a Si-skeleton. Subsequent thermal treatment at 1,450 degrees C for 5 h under flowing nitrogen promoted the nitridation of the Si resulting in alpha/beta-Si3N4 with an alpha/beta fraction of 67%. The ceramic composite maintained the original morphology of the sea sponge and exhibited a porosity of 88%. The microstructure comprised whiskers, small irregular shaped particles and rod-like hexagonal grains.