Effects of Al content on formation of TaC, Ta2C, and Ta2AlC by combustion synthesis with aluminothermic reactions

Abstract

Abstract Fabrication of TaC–, Ta 2 C–, and Ta 2 AlC–Al 2 O 3 composites was conducted by incorporating aluminothermic reduction of Ta 2 O 5 into self-propagating high-temperature synthesis (SHS). Starting materials of this study included Ta 2 O 5 , Al, Al 4 C 3 , and carbon black powders. The effect of elemental Al content was studied by adjusting the proportions of Al, Al 4 C 3 , and carbon. Experimental results showed that the increase of elemental Al facilitated the reduction of Ta 2 O 5 , increased the combustion exothermicity, and improved the evolution of carbide phases. Compared to Al 4 C 3 , elemental Al was demonstrated to be a more effective reductant for Ta 2 O 5 . Formation of Al 2 O 3 -added TaC and Ta 2 C composites with trivial minor phases was achieved by the Al 4 C 3 -free samples with molar ratios of Ta 2 O 5 :Al:C = 3:10:6 and 3:10:3, respectively. For the production of the Ta 2 AlC–Al 2 O 3 composite, a significant loss of Al occurred in the samples especially for those containing Al 4 C 3 . As a result, Ta 2 AlC and Ta 2 C were present as the main carbide phases. The increase of elemental Al improved the yield of Ta 2 AlC, and the need of excess Al was advised.