Silicon nitride porous ceramics prepared by sacrificial method

Abstract

In this work, a comprehensive study was conducted to examine the impact of ammonium bicarbonate (NH4HCO3) content, a porogenic agent, on the development of the microstructure, compressive strength, and Young’s modulus of the porous silicon nitride ceramics using the sacrificial method. The porous ceramics were obtained by pressureless sintering at 1650 oC and characterized by scanning electron microscopy and X-ray diffraction. The findings demonstrated that all samples developed a microstructure with β-Si3N4 grains, but α-Si3N4 and wollastonite were also identified. Moreover, grains with a high aspect ratio are predominant in the pore inner structure. The pore morphology was changed from spherical to irregular when the highest NH4HCO3 content was used. Under this condition, interconnected pores were also present. The values of compressive strength and Young’s modulus decreased with increasing porogen content. The reduction was more pronounced for the ceramic prepared with the highest NH4HCO3 content.