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 Almerı´a)

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 graphitization of amorphous carbon during carburization 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 carburization of Ta with amorphous carbon under solar radiation. Only mono-carbide TaC formed by the carburization of Ta with graphite under solar radiation in accordance with the equilibrium phase diagram. These features were already published individually elsewhere. This article is the brief summary of the reported facts in our earlier publications. Although the results so-far-obtained are rather primitive and still lacking quantitative characterization, 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.