Kinetic model of aluminum oxidation by water vapor in heterogeneous plasma: Gas-phase kinetics

We propose a kinetic model of gas-phase and heterophase plasma-chemical processes taking place in a gas-discharge aluminum-water reactor with a pumping system. The model leads to a relatively simple system of equations that covers a great variety of reactions and offers an analytical solution for the composition of plasma with microparticles using experimental data. Along with the cycle of reactions typical for these heterogeneous mixtures, two more closed cycles of aluminum transformations are revealed in the plasma: atomic and molecular, generated by a stepwise ionization of $\text{Al}$ and $\text{AlO}$ by plasma electrons. The rate of aluminum oxidation and hydrogen formation through the molecular channel under the experimental conditions was comparable to the rate of heterogeneous processes. The inefficiency of the equilibrium oxidation mode is demonstrated.