Mechanical Alloying of Refractory Metals with Boron and Carbon as a Method of Nanocrystalline Compounds Powders Obtaining

High enthalpy of refractory metals borides and carbides points that these compounds can be obtained at low temperature. This can be performed with help of a planetary mill where synthesis processes take place at low temperatures. The carbide and boride formation process at a low temperature yields compounds in nanocrystalline state with the specific surface area up to 7 m2/g. The formation of a particular phase through milling of refractory metals with boron or carbon in a planetary mill depends on the physical-chemical properties of starting powders, enthalpy of the final product formation, and on the intensity of milling process. Depending on these conditions, processes of mechanical alloying in the system Me-boron and Me-carbon run by the following mechanisms: mechanically-induced reaction of self-propagating synthesis (MSS), diffusion-controlled process of interstitial solid solutions decomposition and destruction (amorphization) of the initial metals with subsequent formation of carbide and boride nucleation’s. The compounds obtained during mechanochemical synthesis, independently of the mechanism formation, have a nanostructure.