Boron Carbide Composites produced by Self-Propagating High-Temperature Synthesis

Abstract

This work is a study of the conditions for obtaining boron carbide, magnesia, and aluminum oxide composites by self-propagating high temperatures synthesis (SHS). The substances used to synthesize the composites were boron oxide, magnesia, and aluminum oxide. The SHS with the reduction stage was conducted as the following aggregate reaction: 2B2O3+6Mg+xC--->ByCx+6MgO, 2B2O3+4Al+xC=2Al2O3+ByCx. The metallothermic SHS using boron oxide seems more attractive than the current carbide production methods characterized by long-time and multistage physico-chemical processes requiring increased material, energy, and financial costs. The thermodynamic calculations of the phase composition of the products and the adiabatic combustion temperature for systems B2O3–Mg– C, B2O3–Al–C were made in the FastStage program. The calculations and tests allowed identifying the optimal conditions of SHS. The products of SHS were examined by X-ray phase analysis and the SEM method. The compositions of the B2O3–Mg–C system obtained by SHS were represented mainly by boron carbide, magnesia, magnesium borate, and Mg3B2O6. The products of the B2O3–Al–C system obtained by SHS contained boron carbide, alumina, and aluminum boride.