Mechanochemistry of Ti-C powder mixtures

This work focuses on the reactivity of Ti-C powder mixtures during ball milling. The kinetics of the mechanochemical reaction between Ti and C was investigated while systematically varying the chemical composition, the collision energy and the volume of the powder charge. It is shown that at relatively low and high Ti contents mechanical processing results in the gradual formation of crystalline non-stoichiometric TiC. At intermediate Ti contents, self-sustaining high-temperature reactions are ignited. In all cases, chemical transformations occur only when the collision energy is higher than a threshold value. In the intermediate compositional range, an upper collision energy threshold exists, above which the self-sustaining high-temperature reaction is replaced by a more gradual transformation of the reactants into TiC. Additionally, the total volume of the powder charge must be larger than a minimum value for the self-sustaining high-temperature reactions to take place. The experimental findings are rationalized in terms of a phenomenological approach to the kinetics of mechanically activated processes.