Formation of metastable tungsten tetraboride by reactive hot-pressing

The synthesis of tungsten tetraboride (WB4) powders prepared by reactive hot-pressing in a vacuum from elemental tungsten (W) and amorphous boron (B) powders is reported in this work. This study systematically investigates the effects of the synthesizing temperature, B/W molar ratio, pressure and time on phase formation. The XRD pattern for the as-synthesized powders was analysed. Metastable tungsten tetraboride was synthesized in a vacuum at 1350 °C with a B/W molar ratio of 8.0 under a low uniaxial pressure (30 MPa) for 1 h. The scanning electron microscopy and transmission electron microscopy results showed that the particles had a tendency to form agglomerates. Amorphous boron was found to exist in the final product, and formation of the crystal phase WB4 was confirmed.