In situ synthesis of Al2O3-SiC powders via molten-salt method

Alumina-silicon carbide (Al₂O₃-SiC) composite powder (ASCP) was synthesized by molten salt method with silicon dioxide, carbon black, and Al powder as starting materials and NaCl and KCl together as molten salt medium. Effects of temperature and holding time on the phase composition and morphology were systematically investigated. Possible reactions involved in synthesis process of Al–Si–O–C system were analyzed by thermodynamic calculation, and synthesis mechanism was discussed. As-prepared ASCP was utilized to fabricate Al₂O₃-SiC composite bulk materials by pressureless route. Results show that molten salt is an essential factor to lower synthesis temperature. ASCP was synthesized at 1300 °C by heating for 4 h and template mechanism was found to play an important role. The bulk sample obtained by sintering at 1500 °C for 4 h attained apparent porosity of 42.3%, bulk density of 1.81 g cm⁻³, and higher compressive strength of 16.4 MPa.