Photochemical Effects in Carbide Synthesis of d-Group Transition Metals (Ti, Zr; V, Nb, Ta; Cr, Mo, W) in a Solar Furnace at PSA (Plataforma Solar de Almería)

During the course of our recent series of solar carbide and carbonitride synthesis work for d-group transition elements (Ti, Zr; V, Nb, Ta; Cr, Mo, W), we detected several intriguing evidences apparently indicative of involvement of photochemical effects in some reactions under solar radiation.

1) Acceleration of graphitisation of amorphous carbon during carburisation of W under solar radiation.

2) Promoted formation of high temperature mono-carbide phase of Mo under solar radiation at a temperature lower than the one indicated in equilibrium phase diagram.

3) Formation of sub-carbide Ta₂C besides mono-carbide TaC in the carburisation of Ta with amorphous carbon under solar radiation. Only mono-carbide TaC formed by the carburisation of Ta with graphite under solar radiation in accordance with the equilibrium phase diagram.

Although the results so-far-obtained are rather primitive and still lacking quantitative characterisation, there seems to be no doubt that solar materials processing would open new routes for unique products which cannot be prepared through traditional industrial manufacturing processes.