Preparation of tungsten nitride on alumina by chemical vapor deposition

Tungsten nitride was synthesized on gamma-alumina using a chemical vapor deposition method in a stream of WCl6, NH3, H-2, and Ar at temperatures of 773 to 973 K under 70 Pa. The surface area of the W2N/Al2O3 system decreased from 178 to 140 m(2) g(-1) with increasing tungsten loading. The pore volume decreased with increasing deposition of W2N with a constant distribution of pore size. The X-ray diffraction analysis showed the formation of beta-W2N (100) and (111) phases in the 4.9 wt% W2N/Al2O3 but not in the 1.2 and 3.3 wt% W2N/Al2O3. From the X-ray photoelectron spectroscopy analysis, the N 1s/W 4f atomic ratio increased from 1.3 to 1.6 for the 1.2 to 4.9 wt% W2N/Al2O3. W-0, W2+, and W4+ were dominant for the 4.9 wt% W2N/Al2O3.