Preparation of Si3N4 ceramic aerogel by foam-gelcasting combined concerted catalysis nitridation method

Abstract

High-performance Si3N4 ceramic aerogel (CA) prepared by employing commercial Si powders containing impurity Fe as raw materials and Fe powders as catalyst through a simply Fe-concerted catalyzed nitridation technology, CS Si3N4 CAs, were synthesized at 1473 K for 5 h, and thoroughly characterized. It exhibited a porosity of 87.7 %, a compressive strength of 3.3 MPa and a specific strength of 8.7 MPa cm3 g−1, along with its outstanding low thermal conductivity (as low as 0.108 W m−1 K−1 at 373 K). Compared with the Si3N4 CA catalysis nitridation of concerted reactions by Fe(NO3)3·9H2O and in-situ catalytic nitridation by impurity Fe in commercial Si, and the specific strength of CS Si3N4 CA was about 14 % and 22 % higher than that of the former, respectively. This demonstrated that it may be more conducive to the preparation of Si3N4 CAs with high performance via catalysis nitridation of concerted reactions by Fe than Fe(NO3)3·9H2O. This work also provides an ideal method for the cost-effectiveness synthesis of high-performance Si3N4 and/or Si3N4 composites.