Diborides of Transition Metal of IV-VI Groups: Features of Formation during Mechanochemical Synthesis

Abstract

Highly disperse powders of diborides of IV–VI group transition metals (TiB₂, HfB₂, NbB₂, TaB₂, CrB₂, Mo₂B₅ and W₂B₅) have been produced by mechanochemical synthesis from elements and low-temperature heat treatment of activated charges. The particle size of the powders is ≤1 μm. Differences in periods and groups during formation of diborides of IV–VI group transition metals have been revealed. Diborides Ti and Nb form discontinuosely. Diborides Hf and Ta form through formation stages of lower boride phases, whereas higher borides Cr, Mo, and W form in almost a single-phase state only after low-temperature processing of preliminarily mechanoactiated original charges. The established differences have been analyzed from the point of view of the donor-acceptor capability of atoms of boron and doboride-forming transition metals.