Mechanically induced self-sustaining reactions

Resumo

Some kinetic aspects of mechanically induced self-sustaining reactions (MSRs) were investigated. The work aimed at establishing possible relationship between milling conditions, ignition time, and diffusion mechanisms in such reactions. Experimental and modeling results showed that ignition of MSR systems with high ΔH/C_p values (combustion systems) is possible upon simultaneous activation of all three diffusion mechanisms, i.e. surface diffusion, grain boundary diffusion, and lattice diffusion. When the ignition occurs, a set of diffusion mechanisms are activated, which provides proper conditions for immediate production of nanocomposite materials. Scrutiny of several combustion systems testified that there exists a fundamental difference between the self-sustaining and gradual mechanochemical reactions. Incomplete reactions, reappearance of starting reactants, intensity of XRD peaks, and grain growth can be regarded as important distinctions between ignitable (MSR-type) and non-ignitable (gradually reacting) systems.