Application of a molecular precursor to the preparation of tungsten and beta-tungsten nitride coatings and powders

Abstract

The use of the tungsten imido/amido complex (N-H-t-Bu)₂W(N-t-Bu)₂ (Complex 1) (CAS number 72207-45-5) as a precursor to tungsten and tungsten nitride films, coatings and powders is reported. The alkane-soluble Complex 1 exhibits high solubility in solvents such as hexane and toluene, making it amenable to application to substrates via dip-coating or spotspraying. This avoids the necessity of vapour deposition methods and the, presently common, use of tungsten fluorides. Thermolysis in an ammonia/nitrogen, ammonia/argon or exclusively nitrogen atmosphere at temperatures between 600 and 1200°C provided a coating or powder comprised of elemental tungsten (75–95 mol%) and tungsten nitride (25-5 mol%). Oxygen content of these materials is less than 0.5%. Thermolysis in an argon atmosphere produced a coating on AIN substrates which were found to contain no β-W₂N (as detectable by X-ray diffraction), only tungsten metal. The coating was successfully applied to sintered aluminium nitride electronic and structural substrates. A coated aluminium nitride substrate exhibited improvement in erosion resistance when compared to an uncoated specimen.