Combustion synthesis and characterization of porous β‐SiAlON fiber‐reinforced foam filters

Abstract Porous β‐SiAlON demonstrates unique physical and chemical properties that make it especially advantageous as a porous filter medium used under extreme operational conditions. Among the various synthesis methods, self‐propagating high‐temperature synthesis (SHS), also known as combustion synthesis, is recognized as one of the most energy‐efficient and rapid approaches for producing of β‐SiAlON powder. However, existing methodologies in the field of SHS are insufficient for producing porous β‐SiAlON with predetermined shapes, porosity, and pore sizes that can be used directly without further technological processing of the combustion products. The primary objective of this study is to develop a method for synthesizing mechanically stable, porous β‐SiAlON in block form, devoid of macro‐defects, and possessing specific foam porosity and pore dimensions through SHS. The developed approach consists of two stages: (1) the initial structuring of the powder precursor, and (2) subsequent nitridation via SHS. The investigation showed the effects of alkali content in the initial slurry, nitrogen gas pressure, and the initial dimensions of the blocks on the combustion characteristics of the pre‐structured samples. Optimal and critical synthesis parameters were determined. A comprehensive analysis of the phase composition, porosity, pore size, chemical composition, and microstructure of the synthesized samples was conducted. The porosity of the nitrided samples ranged from 37% to 77%, predominantly characterized by open porosity, with a maximum pore size of up to 24 mm. Furthermore, the study presents findings related to acid resistance, oxidation resistance, thermal shock resistance, compressive strength, and gas permeability of the synthesized porous β‐SiAlON.