XPS STUDIES OF SUPPORTED TUNGSTEN CARBIDE(S)

The XPS of carburized Al2(WO4)3, 12% WO3, 28% WO3 and (3.9% Pt + 26% W O3) supported on gamma-Al2O3 has been reported. Argon ion bombardment or hydrogen at 1073K enabled to reduce more than 50% of the W(VI) to W (0) in apparent one single step process. Severe conditions of reductio n by H-2 and carburization using CH4/H2 mixture were required in order to transform 90% of the W in Al2(WO4)3 to tungsten carbide. Lesser am ount of WC were obtained in the case of supported systems due to a ver y strong metal-support interaction. Argon ion bombardment employed as reducing agent enabled to optimize the reduction conditions of these t ungsten oxide systems. It has also been observed that WC could be redu ced to the elemental W(0) upon Ar+ bombardment. Although indications a bout the presence of oxycarbide species have been observed, no conclus ive evidence about its exact structure could be formulated.