Combustion Synthesis of Mo5sib2–Al2o3 Composites
Fabrication of Mo5SiB2–Al2O3 composites was conducted by thermite-based combustion synthesis in the SHS
mode. Thermite reagents of MoO3 + 2Al were introduced into two Mo‒Si–B ternary systems adopting amorphous boron and
MoB as their respective boron source. The boron-containing samples were more energetic and were applied to produce
composites with Mo5SiB2/Al2O3 from 1.25 to 2.5. The composites with Mo5SiB2/Al2O3 from 0.8 to 1.3 were prepared from
less exothermic MoB-based samples. Besides causing a decrease in combustion velocity and reaction temperature, the
increase of the Mo5SiB2/Al2O3 proportion led to a transformation in combustion wave propagation from a steady to pulsating
mode. For the samples featuring a pulsating combustion wave, the reaction time at peak combustion temperatures was
extended and then the evolution of Mo5SiB2 from intermediate phases (Mo3Si and MoB) was significantly improved. The
microstructure of synthesized composites reveals that plate-like Mo5SiB2 grains with an average size of 10–15 m are
tightly packed and irregular Al2O3 grains are randomly dispersed.
Keywords - Borosilicide Mo5SiB2, Combustion Synthesis, Aluminothermic Reduction, Pulsating Combustion.