Effects of TiC addition on formation of Ti2SnC by self-propagating combustion of Ti-Sn-C-TiC powder compacts

Preparation of the ternary carbide Ti2SnC 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 Ti2SnC was substantially enhanced by the TiC-containing sample. For the elemental powder compact, the final product contains more Ti6Sn5 than Ti2SnC, implying an incomplete phase conversion. In contrast, Ti2SnC 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 Ti2SnC grains is also affected by the addition of TiC in the reactant mixture. The growth of rod-like Ti2SnC grains was prevailing in the final product of the Ti-Sn-C powder compact, but the TIC-added samples favored the evolution of Ti2SnC with a plate-like microstructure. (C) 2010 Elsevier B.V. All rights reserved.