Porous Si3N4 Ceramics Prepared by Gelcasting Route and Pressureless Sintering at Different Temperatures

In this work, the gelcasting method was used to prepare porous Si3N4 ceramics, using sodium lauryl sulfate and Isobam 110 as foaming and gelling agents, respectively. Samples sintered at different temperatures were characterized by mercury porosimetry, X-ray diffraction, scanning electron microscopy, and compressive strength. The findings demonstrated that the samples had a porosity ranging from 53.6 to 67.21%, featuring a porous structure with interconnected pores with average pore size varying between 89.20 and 158 µm and pore throats of ~0.3-0.5 µm. α-Si3N4, β-Si3N4, CaSiO3, and Ca3SiO5 phases were identified in all porous ceramics. Increased β-Si3N4 content, density, and compressive strength were observed in ceramics sintered at higher temperatures. Even when the samples reached a porosity of 67.21%, the compressive strength remained relatively high, with a value of 59.36 MPa. As a result, the porosity and strength of the porous Si3N4 ceramics were well-balanced due to the efficient use of gelcasting method