The kinetic model of Al oxidation in heterogeneous aluminum-water plasma. Negative ions

Abstract

We investigate the mechanisms of formation and death of negative ions in aluminum-water plasma, their role in kinetics of its ionization and recombination, and influence on plasma parameters. Negative ions, in contrast to the positive, do not in fact participate in the heterogeneous processes and require, to enhance their influence on the plasma parameters, first, high electron temperatures (~1.5 eV and higher) and, second, low n_e and [Al] concentrations: in this way, they make a great contribution to the H₂O dissociation at the expense of the electron energy (2–8 electrons per a molecule). We show that, even in the most favorable conditions at low H and O concentrations within the experimental temperature range, T_e = 0.6–1 eV, the negative ions do not, in fact, influence the Al concentration and, in the operation reactor zone, the other parameters, except for the microparticle concentration. We reveal the source, important for the spectral diagnostics of the atomic emission, of recombination populating of the excited Al levels. The main negative ion (OH^–) is established. We have concluded the impossibility of its use in order to optimize the operation of the aluminum-water plasma-chemical reactor.