ISSN:
1572-879X
Keywords:
tungsten carbide
;
surface composition
;
XPS
;
argon ion bombardment
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The XPS of bulk tungsten carbide, partially oxidized WC surfaces at 373 and 573 K as well as tungsten trioxide have been reported. Bulk WC has been prepared from WO3 as a starting material in a mixture of CH4 (20%) and H2 (80%) at 1150 K for 4 h, while partially oxidized WC surfaces were prepared by oxygen chemisorption on a clean WC surface at 200 K, then the temperatures were raised to 373 and 573 K respectively. The XPS of a freshly prepared WC reveals the presence of a small amount of WO3 on the surface and a slightly higher concentration in the bulk. The oxygen-exposed fresh WC surfaces and surfaces treated at temperatures higher than 373 K show the presence of WO3 in a considerable quantity depending on the length and the treatment temperature. Ar+ bombardment of this partially oxidized surface reduces WO3 to WO2 and W(0), while WC is partially reduced to W(0). Isomerization reactions of alkanes on oxygen-exposed WC surface occurs in reality on a composite surface structure containing WC, WO3, WO2 and elemental W(0).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00807119
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