Synthesis
ReB2 can be synthesized by at least three different methods at atmospheric pressure: solid-state metathesis, melting in an electric arc, and direct heating of the elements.
In the metathesis reaction, rhenium trichloride and magnesium diboride are mixed and heated in an inert atmosphere and the magnesium chloride byproduct is washed away. Excess boron is needed to prevent formation of other phases such as Re7B3 and Re3B.
In the arc-melting method, rhenium and boron powders are mixed and a large electric current (80 amperes) is passed through the mixture, also in an inert atmosphere.
In the direct reaction method, the rhenium-boron mixture is sealed in a vacuum and held at a high temperature over a longer period (1000 °C for five days).
At least the last two methods are capable of producing pure ReB2 without any other phases, as confirmed by X-ray crystallography.
Read more about this topic: Rhenium Diboride
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