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Journal of Advanced Ceramics

Keywords

porous Si, gelcasting, self-propagating high-temperature synthesis (SHS), porosity

Abstract

Porous silicon nitride ceramics have attracted a considerable attention due to their excellent overall performance, but poor porosity homogeneity and structural shrinkage induced by prolonged high temperature sintering limit its further application. Herein, as a three-in-one solution for the above issues, for the first time we develop a novel approach that integrates the merits of gelcasting-SHS (self-propagating high-temperature synthesis) to prepare porous Si3N4 ceramics to simultaneously achieve high porosity, high strength, high toughness, and low thermal conductivity across a wide temperature range. By regulating the solid content, porous Si3N4 ceramics with homogeneous pore structure are obtained, where the pore size falls inbetween 1.61 and 4.41 μm, and the elongated grains are interlaced and interlocked to form micron-sized coherent interconnected pores. At the same time, porous Si3N4 ceramics with porosity of 67.83% to 78.03% are obtained, where the compressive strength reaches 11.79 to 47.75 MPa and fracture toughness reaches 1.20 to 6.71 MPa·m1/2.

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