Combustion synthesis of porous single-phase β-SiAlON (z = 3)

Abstract

Self-propagating high-temperature synthesis (SHS) is widely used for producing nitride and oxynitride powders. To directly synthesize porous nitrogen ceramics with the predetermined size, shape, and structure, it is necessary: (1) to determine the process conditions for maximizing the conversion rate of the initial reagents into the target ceramic phases and (2) to develop the methods for structuring the reactive powder mixtures into a porous block that can retain the pore-channels size-, shape-, and structure during the synthesis. The conditions for SHS of single-phase β-SiAlON (z = 3) porous blocks using the reaction mixture of Al, Si, and microsilica powders diluted with a sialon-based powder self-made by milling the synthesized ceramic at a low conversion rate are described. The effect of the chemical composition, characteristic size and density of the reactive powder sample, and the nitrogen pressure on the parameters of the combustion process and the synthesized ceramics composition are studied. The critical and optimal parameters of the synthesis are revealed. A possibility of synthesizing single-phase β-Si₃Al₃O₃N₅ porous blocks free of melted regions is shown for the cases where the reactive mixture contains at least 50 wt.% diluent powder.