LAUSR

Abstract Thermite-based combustion reaction combining MoO 3 and B 2 O 3 as the oxidants, Al as the reductant, with Mo, Si, and B powders was conducted to fabricate Mo 5 SiB 2 –Al 2 O 3 composites. Combustion synthesis involving co-reduction of MoO 3 and B 2 O 3 is less exothermic than that adopting MoO 3 as the sole oxidizing agent. The resulting products with Mo 5 SiB 2 /Al 2 O 3 ratios between 0.8 and 1.3 were synthesized from the MoO 3 /B 2 O 3 -based samples and those between 1.25 and 2.5 from the MoO 3 -based samples. These two combustion reactions were shown to have low activation energies of E a  = 60.7 and 86.5 kJ/mol, indicating that the SHS reactions involving aluminothermic reduction of either MoO 3 /B 2 O 3 or MoO 3 significantly reduce the kinetic barrier of forming Mo 5 SiB 2 . In particular, it was found that prolonged reaction times contributed to the improvement in evolution of Mo 5 SiB 2 from intermediate phases (Mo 3 Si and MoB) for the samples with a reaction front speed slower than 4 mm/s or a pulsating combustion wave. The as-synthesized composites exhibit a dense morphology with connecting plate-like Mo 5 SiB 2 grains.