Synthesis of tantalum carbide from multiwall carbon nanotubes in a molten salt medium

Tantalum carbide (TaC) nanofibers and coatings were synthesized using multiwall carbon nanotubes (MWCNTs) with different structures as templates and the carbon source in a KCl-LiCl molten salt mixture (41.2/58.8 mol/mol). The TaC and MWCNTs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and selected area electron diffraction. Results indicate that the microstructure of the MWCNTs has a distinct influence on the formation of a TaC coating on the MWCNTs. MWCNTs heat-treated at 2 900 °C have a higher crystallinity and are harder to react with Ta to form TaC than those without the heat-treatment. The formation of TaC nanofibers or TaC coatings on MWCNTs is dependent on the molar ratio of tantalum to carbon nanotubes. The morphology of the polycrystalline cubic TaC nanofibers and the TaC coating is similar to that of MWCNTs. The reaction time and temperature have a great influence on the conversion of carbon to TaC and its crystallite size.