Synthesis of Highly Dispersed Powder Ceramic Composition Si₃N₄–SiC by Combustion of Components in the Si–C–NaN₃–NH₄F System

Abstract—The possibility of synthesizing a highly dispersed powder nitride-carbide composition Si₃N₄–SiC by combustion of a mixture of sodium azide (NaN₃) with elemental powders of silicon (Si) and soot (C) and an activating addition of ammonium fluoride (NH₄F) in a nitrogen atmosphere has been investigated. The combustion parameters, chemical and phase composition, morphology, and particle sizes of the synthesized products have been determined. It is shown that, after water washing, the powder combustion product consists of silicon nitride of two modifications (α-Si₃N₄ and β-Si₃N₄) with a predominant content of α-Si₃N₄, silicon carbide (β-SiC) in an amount from 1.6 to 41.8%, and an insignificant amount of free silicon (Si). In most cases, the obtained nitride-carbide composition Si₃N₄–SiC is a mixture of submicron (0.1–0.5 µm) fibers and equiaxed particles, promising for low-temperature sintering of the corresponding structural composite ceramic materials with enhanced mechanical properties.