Tungsten Borides: On the Reaction of Tungsten with Boron(III) Bromide

The crucible-free reaction between heated tungsten wires and gaseous boron tribromide yields different tungsten borides. The experiments were carried out at various reaction temperatures and times, revealing the formation of W₂ B, WB and WB₂ phases. The underlying reactions were analyzed by using thermodynamic model calculations. The stability of the gaseous tungsten bromides was evaluated using quantum chemical methods. While the developed synthesis of phase-pure borides is only possible to a limited extent, it offers a potential route for a formation of protective coatings with high chemical and thermal resistance.