Reaction between tantalum (Ta) and carbon (graphite or amorphous carbon) in tap-compacted powder mixture state under solar radiation heating was investigated. Although mono-carbide TaC is the final equilibrium product at 1600 degrees C under presence of excess carbon, formation of sub-carbide Ta2C as the interim product was detected under certain circumstances. After 30 min reaction at 1600 degrees C reached by solar radiation heating, Ta powders compacted with graphite powders by pressing into pellet were fully converted to TaC but loosely tap-compacted powder mixtures of Ta and graphite yielded Ta2C coexisted with TaC. On the other hand, Ta powders tap-compacted with amorphous carbon were fully converted to TaC under the comparable reaction condition reflecting the high reactivity and chemical carbon activity of amorphous carbon compared with those of graphite (reference state of carbon). (c) 2006 Elsevier Ltd. All rights reserved.