Electrochemical Synthesis of Nano-Metallic Carbides from the Mixtures of Metal Oxide and Graphite

Nanocrystalline transition metal carbides (TMCs, M = Ti, Zr, Hf, Nb and Ta) have been synthesized by direct electrochemical reduction of solid mixture precursors composed of transition metal oxides and graphite powder (TMOs-C) in molten CaCl 2 at 850°C. The synthesis temperature is much lower than that of the conventional carbothermic reduction process. SEM analysis showed that the particle sizes of the as-prepared TMCs powders were about 15–30 nm. The formation processes of nanocrystalline TMCs monitored by analyzing partially reduced samples were confirmed to be similar to each other and could be divided into three steps: TMOs-C first to CaM a O b and MC x O y , then to pure MC x O y and last to MC. It has been found that the electrolysis production of TM V Cs is much faster than that of TM IV Cs. The formation of intermediate MC x O y during the electrolysis processes was investigated and their stability should be the key influence factor of the electro-deoxidation rate of the mixtures.