Effect of mechanical activation on the formation of Si3N4-SiC composite powders

Abstract

The paper examines how the mechanical activation of an initial silicon-carbon powder mixture and the temperature of its subsequent treatment influence the specific surface and phase composition of the end products. It is established that the preliminary mechanical activation of Si-C mixtures significantly increases the nitration rate of silicon and decreases the temperatures of formation of silicon carbide and silicon nitride (1200-1300°C). The products resulting from the nitration of mechanically activated mixtures consist of α-Si 3 N 4 whiskers with an aspect ratio of 10-100, silicon, carbide, and silicon nitride particles to 100 nm in size, and their agglomerates.

Role of Temperature and Nitrogen Flow Rate During the Carbothermic Synthesis of SiC/Si3N4 Nanocomposite Powder from Gel

“…This is according to the facts that the cost of raw materials is relatively low and the simultaneous formation of SiC and Si 3 N 4 guarantees that the SiC and Si 3 N 4 are inherently well distributed. Also, the presence of a higher percentage of CO gas in the reaction media (as a result of carbothermal reduction of the xerogel) will retard the transformation of α‐Si 3 N 4 into β‐Si 3 N 4 30–32 . Li and Riedel 33 have investigated the preparation of SiC/Si 3 N 4 nanocomposite powder via a carbothermal reaction of silica‐phenol resin hybrid gel.…”