An experimental study on self-propagating high-temperature synthesis in the Ta–B4C system

Preparation of the TaC–TaB and TaC–TaB2 composites with a broad range of the phase composition was conducted by self-propagating high-temperature synthesis (SHS) with the samples compressed from the Ta–B4C and Ta–B4C–C powder mixtures. Under a preheating temperature of 200 °C, self-sustaining combustion in the reactant compact was achieved. Experimental results showed that the reaction temperature and propagation velocity of the combustion front depended upon the phase and content of the boride formed in the composite. Higher reaction temperatures and faster reaction fronts were observed in the formation of the composites containing TaB than TaB2. Moreover, due to the higher formation enthalpy for TaB than TaC, the combustion temperature and reaction front velocity increased with TaB content when the TaC–TaB composites were synthesized. However, on account of the larger heat capacity of TaB2 than that of TaC, an opposite trend was observed in the synthesis of the TaC–TaB2 composites. The XRD pattern of the synthesized product confirms SHS formation of the TaC–TaB and TaC–TaB2 composites from the reactions of the Ta–B4C–C and Ta–B4C powder compacts under well-designed stoichiometries.