Fabrication of Porous Reaction-Bonded Si₃N₄-SiC Composites

Abstract

Porous reaction-bonded Si3N4-SiC composites were fabricated by using potassium chloride(KCl) as pore-forming agent. Green bodies with 20% SiC and 30% KCl in mass were subjected to presinter in Ar atmosphere at 1000~1200 and then reaction-sintered. The results indicated that Si3N4-SiC composites which with about 58.5% porosity could be prepared, and the main phase compositions were α-Si3N4 and SiC. After presintered, the porosity of composites had small decrease, but bending strength increased obviously and little amounts of Si2N2O had been found. The distribution of pores of porous ceramics was homogeneous and SiC grains were surrounded by Si3N4 grains and fibres. Lots of needle-like α-Si3N4, especially in the high porosity ceramics, could be observed.

Porous Si3N4/SiC Ceramics Prepared via Nitridation of Si Powder with SiC Addition

“…While the nitridation reaction between Si and N 2 was an exothermic processing, the nitridation of a Si compact in local areas may be overheat, resulting in incomplete nitridation and a poor structure with large pores and big grains. By incorporating an inert second‐phase material, such as SiC grains or fibers, the second phase was used as diluting fillers into the compacts, which was an effective way to control the nitriding process. In addition, it was also desirable to prepare Si 3 N 4 /SiC ceramics with improved mechanical properties, adjustable porosity, and controllable structure with the addition of SiC particles, which were located at the grain boundaries during the nitriding process.…”