Effects of TiC addition on formation of Ti 2SnC by self-propagating combustion of Ti–Sn–C–TiC powder compacts

Abstract

Preparation of the ternary carbide Ti 2SnC was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) using both the elemental powder compacts and TiC-added samples with TiC contents from 2.6 to 17.6 mol%. On account of the dilution effect of TiC on combustion, the reaction exothermicity was reduced by adopting TiC in the reactant mixture. As a result, the combustion temperature and reaction front velocity decreased significantly with increasing TiC content. Moreover, the self-sustaining combustion front was no longer planar and was confined to localized reaction zones in the samples with high proportions of TiC like 14.3 and 17.6 mol%. On the other hand, the yield of Ti 2SnC was substantially enhanced by the TiC-containing sample. For the elemental powder compact, the final product contains more Ti 6Sn 5 than Ti 2SnC, implying an incomplete phase conversion. In contrast, Ti 2SnC dominates in the products synthesized from the TiC-added samples and increases with TiC content, which is attributed to the prolonged reaction time and appropriate reaction temperature provided by the Ti–Sn–C–TiC powder compacts. The morphology of as-synthesized Ti 2SnC grains is also affected by the addition of TiC in the reactant mixture. The growth of rod-like Ti 2SnC grains was prevailing in the final product of the Ti–Sn–C powder compact, but the TiC-added samples favored the evolution of Ti 2SnC with a plate-like microstructure.