Formation mechanism of nanostructured metal carbides via salt-flux synthesis.

Nanostructured metal carbides are of particular interest because of their potential as high surface area, low-cost catalysts. By taking advantage of a salt-flux synthesis method, multiple carbide compounds were synthesized at low temperatures providing a pathway to nanosized materials. To better understand the reaction mechanism, vanadium carbide (V8C7) synthesis was monitored by quenching samples at 100 °C intervals and analyzed by multiple spectroscopic methods. The reaction was determined to occur through the formation of metal halide and acetylide carbide intermediates, which were repeatedly observed by X-ray diffraction and further supported by IR and Raman spectroscopies. Control experiments were also employed to further verify this mechanism of formation by using different salt compositions and a solid-state metathesis reaction. The reaction mechanism was also verified by applying these techniques to other metal carbide systems, which produced similar intermediate compounds.