Tribochemical modification of the microstructure of V₂O₅

The tribochemical activation of vanadium pentoxide V₂O₅ is studied by means of X-ray diffraction, electron microscopy and electron energy-loss spectroscopy. The two-stage process can be described as crushing of large crystals into small ones (macroscopic process) followed by amorphisation and reagglomcration of the fragments (microscopic process). No milling equilibrium state can be found. Energyloss spectra reveal the reduction of vanadium via oxygen loss. The formation and distribution of V⁴⁺ or V³⁺ species depends on the history of milling.