A facile strategy for fabricating self-sealing dense coating grown in-situ on porous silicon nitride ceramics.

This present work explores initially the feasibility of producing in-situ surface oxidized coating on porous silicon nitride (Si 3 N 4) ceramics. Theoretical prediction identifies the applied conditions of self-sealing strategy and oxidation time required to form dense coating. Experimentally, the porous Si 3 N 4 ceramics with different pore structures were selected to fabricate in-situ oxidized coatings. The phase compositions, microstructures and mechanical properties of the porous Si 3 N 4 ceramics were investigated before and after oxidation. The results show that flat and dense coatings are prevailed in all samples, which consist of amorphous SiO 2 and its precipitates besides dominant Si 3 N 4 phase. The strengthened substrate and strengthening effect of coating are the essential mechanisms associated with the improved mechanical properties. Self-sealing method seems to offer an inexpensive and efficient route to prepare coating on porous Si 3 N 4 ceramics. [ABSTRACT FROM AUTHOR]