Synthesis and mechanical properties of highly porous ultrafine-grain Si3N4 ceramics via carbothermal reduction-nitridation combined with liquid phase sintering

Highly porous Si3N4 ceramics have been prepared via a novel carbothermal reduction-nitridation (CRN) reaction between carbon nanotubes (CNTs) and SiO vapor in a N2 atmosphere. The green bodies consisted of 49.0 wt% CNT, 40.4 wt% α-Si3N4 as seed and 10.6 wt% Y2O3 as sintering additive, and SiO powders were located under the green bodies during sintering. By heating at temperatures ranging from 1550 to 1650 °C, fibrous β-Si3N4 nanograins were...