Manufacture of Si3N4-SiCN composite bulks with hierarchical pore structure

Si3N4-SiCN ceramic foams with hierarchical pore architecture were formed by protein-based gelcasting and precursor infiltration and pyrolysis. The primary pore structure (>100 mu m) was generated by protein gelation and precursor ceramization, while the secondary pore structure (10-50 mu m) originated from the cell windows after pyrolysis. The network of Si3N4 nanowires and the voids among ceramic particles formed the tertiary pore structure (<2 mu m). The obtained Si3N4-SiCN ceramics had a density of 0.45-0.66 g/cm(3) and an open porosity of 72.7-82.8 vol.%. The porous bulks possessed a compressive strength of up to 16.9 +/- 1.1 MPa (72.7 vol.% open porosity) at room temperature and 8.6 +/- 0.2 MPa at 800 degrees C. A good gas permeability of the ceramics was indicated with a tested value of 3.27 cm(3)cm/(cm(2).s.kPa). The excellent mechanical property, permeability together with the hierarchical pore structure enabled the Si3N4-SiCN composite bulks promising for industrial filtration applications.

Automated summary

Si3N4-SiCN ceramic foams with hierarchical pore architecture were successfully prepared by protein-based gelcasting and precursor infiltration and pyrolysis. The ceramics exhibited low density, high compressive strength, good gas permeability, and showed promise for industrial filtration applications.