Silicon Carbide–Silicon Nitride Refractory Materials: Part 1 Materials Science and Processing

Silicon carbide and silicon nitride materials were intensively studied in the end of the past century, yet some aspects of its physical chemistry require investigation. The strength characteristics of Si3N4-SiC refractories are moderate; however, these materials sometimes demonstrate “stress–strain” behavior, more typical for composite materials than for the brittle ceramics. These materials may be considered to be ceramic composites because they consist of big grains of silicon carbide surrounded by small grains of silicon nitride, with strict interfaces between them. There is no direct certainty whether Si3N4-SiC compositions may be called composite materials or brittle ceramic materials from the viewpoint of mechanics and strength. The balance of α/β modifications of silicon nitride in Si3N4-SiC composite material and, the occurrence and the role of silicon oxynitride Si2ON2 are also a matter of scientific interest in processing of Si3N4-SiC composite material. The same may be said about the particles of silicon nitride between the grains of silicon carbide—there is no direct understanding whether silicon nitride grains will be isometric grains or needle-like crystals.