Effect of oxygen on the structural and electrochemical properties of nanocrystalline Ti-Ru-Fe alloy prepared by mechanical alloying

The effect of the oxygen content on the structural and electrochemical properties of Ti-Ru-Fe-O alloys prepared by high energy ball milling was studied. The structural evolution of the materials has been analyzed by x-ray powder diffraction. The identification of the various crystalline phases, as well as the crystallite size, has been performed by Rietveld refinement analysis. In a first series of experiments, oxygen was added to pre-formed beta(2)-Ti2RuFe. It was shown that this causes the beta(2) phase to decompose info Ru, Fe anal TiO. In a second series of experiments, various amounts of oxygen were added at the very beginning of the milling process by keeping the Ti:Ru ratio constant at 2:1 and varying the Ru:RuO2 ratio, it was shown that oxygen is only slightly soluble in the beta(2) phase. X-ray photoelectron spectroscopy reveals that Ti anal Fe at the surface of the material are highly oxidized while Ru is in the metallic state. The electrochemical properties of these materials have been tested in typical chlorate electrolysis conditions. The electrocatalytic activity oft he cold-pressed powders did not show any marked variation with the oxygen content. This is most probably related to the fact that the surface composition of the material is almost independent of the bulk O content. A reduction of the activation overpotential at 250 mA cm(-2) of 200-250 mV is observed when compared to that of a pure Fe cathode. (C) 1998 Acta Metallurgica Inc.