Synthesis and classification of WC and W metals via organic–inorganic complex precursors

抄録

Mono-tungsten carbide (WC) and tungsten (W) have been successfully synthesized and classified by controlling organic–inorganic hybrid precursors. Tungstic acid (H₂WO₄) was dissolved into ammonium water and then citric acid (C₆H₈O₇) as a carbon source was dissolved into the H₂WO₄ solution. The precursors, which were obtained by drying the chemical complex solutions, were heated at 1473 K for 1 h with Ar gas flow by a conventional electric furnace. Classification of WC and W was achieved by controlling the precursor processing conditions. In terms of making WC only, two important processing factors were revealed. One, the C/W molar ratio of an organic–inorganic hybrid precursor should be more than 4.0, and two, the obtained chemical complex should be re-dissolved and aged for more than 24 h. Tungstic ions in the re-dissolved chemical complex solution may be changed into polyanions. The sizes of the obtained WC particles and W metal were approximately 100 nm and 2 µm, respectively.