Tungsten boride is a silver octahedron crystal with high hardness that dissolves in aqua regia and some concentrated acid. But, it is insoluble in water. Its molecular formula is WB2. WB2 may be obtained by heating metal tungsten and boron with electric furnace.
The CAS number of tungsten boride is 234-498-8. The melting point is 2900°C. The density is 10.77g/cm3. And it is decomposed by chlorine under 100°C. The Vickers hardness of WB2 crystals is ~20 GPa.
Structure of Tungsten Boride
WB2 has the same hexagonal structure as most diborides such as AlB2, MgB2, etc.
Properties of Tungsten Boride
1. WB2 crystal has metallic resistivity of 0.3 mΩ•cm.
2. The oxidation of WB2 is significant at the temperature above 600°C. The final oxidation products contain WO3 and probably amorphous B2O3 or H3BO3.
Synthesis of Tungsten Boride
Single crystals of WB2−x, x=0.07–0.17 (about 1cm diameter, 6cm length) are produced by the floating zone method.
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