ceramics, sintering, porosity, mechanical properties, permeability
Silicon nitride foams with a hierarchical porous structure was formed by the combination of protein-based gelcasting, chemical vapor infiltration, and in-situ growth of silicon nitride nanowires. The porosity of the foams can be controlled at 76.3-83.8 vol% with an open porosity of 70.2-82.8 vol%. The pore size distribution was presented in three levels: < 2 μm (voids among grains and cross overlapping of silicon nitride nanowires (SNNWs)), 10-50 μm (cell windows), and >100 μm (cells). The resulted compressive strength of the porous bodies at room temperature can achieve up to 18.0±1.0 MPa (porosity = 76.3 vol%) while the corresponding retention rate at 800 ℃ was 58.3%. Gas permeability value was measured to be 5.16 (cm3·cm)/(cm2·s·kPa). The good strength, high permeability together with the pore structure in multiple scales enabled the foam materials for microparticle infiltration applications.
Tsinghua University Press
Junsheng LI, Qiuping YU, Duan LI, Liang ZENG, Shitao GAO. Formation of hierarchical Si3N4 foams by protein-based gelcasting and chemical vapor infiltration. Journal of Advanced Ceramics 2021, 10(1): 187-193.