Effects of Boron Source on Combustion Synthesis of Chromium Boride/Al2O3Composites

Chromium boride/Al2O3 composites were synthesized by incorporating the thermite reaction into a self-propagating combustion process. Boride phases formed from the Cr2O3 + 2Al + xB samples were identified as Cr2B, CrB, and CrB2 with respect to their starting stoichiometries of x = 1.2, 3.0, and 7.0, indicative of the need of excess boron. On the other hand, Cr2B, CrB, and CrB2 were yielded from the Cr2O3 + 2Al + yB4C reactant compacts containing B4C of y = 0.25, 0.5, and 1.0, respectively. This shows that B4C as the boron source resolves the problem of boron loss during combustion synthesis.