Synthesis of Al3BC3particulates by carbo-thermal reduction process - Parameter optimization and mechanism analysis

Abstract

The synthesis mechanism of Al3BC3through carbo-thermal reduction process was investigated and the processing conditions were optimized using Al(OH)3-B2O3-C as starting materials. The mass change and phase formation of the compacts were analyzed with varying temperature. Excess Al(OH)3and B2O3were required compared to the stoichiometric composition due to the loss of the source materials by vaporization at 1,500-1,600°C. At 1,600°C, Al2O gas began to actively react with carbon to form Al4C3on the carbon particles. Al, Al2O and B2O3gases diffused through Al4C3layer and reacted with carbon at and above 1,650°C to form Al3BC3. The formation of hexagonal terrace at the surface of synthesized powder indicated that the gases also reacted at the particle surface with carbon which diffused through the carbide layers. The reactions were completed after calcination at 1,725°C for 4h or at 1,800°C for 1h. Gas-solid reactions were the major synthesis mechanism. The optimum composition for the synthesis of the ternary compound was Al(OH)3:B2O3:carbon = 0.7: 1.4: 0.25 by weight.