Compounds of molybdenum and tungsten with high specific surface area: II. Carbides

Temperature-programmed carburization of W₂N and Mo₂N powders in CH₄H₂ mixtures up to 1150 and 970 K, respectively, leads to metastable face-centered cubic carbide phases. The reaction is topotactic in the sense that the face-centered cubic structure of the metal atoms remains unaltered, while the nitrogen and carbon atoms exchange their interstitial positions. Thus, the product retains the structure, crystallite size, and high specific surface area of its nitride parent, namely, 55 and 185 m² g^?1 for β-WC_1?x and α-MoC_0.45, respectively.