Formation of rhenium diboride via mechanochemical–annealing processing of Re and B

Rhenium diboride (ReB2) powder was prepared by mechanochemical processing of Re–B powder mixtures with subsequent annealing at temperatures of 600 °C to 1200 °C. Reactive evolution during the synthesis was investigated; furthermore, the effects of the amount of excess B on the reactions that occurred during the synthesis were assessed. The substantial reaction of Re with B occurred at 700 °C to form Re7B3 with a small amount of ReB2. At 800 °C, Re7B3 converted into ReB2; this conversion was enhanced with increasing temperature and increasing amount of excess B. At 1000 °C or above, single-phase ReB2 powder without trace quantities of Re7B3 was obtained for compositions with 15 wt% or greater excess B. The synthesized ReB2 powder particles were submicrometer with the vast majority being ∼500 nm. In addition, the resulting ReB2 powders were consolidated by hot pressing or spark plasma sintering to examine the sinterability of the powders.