A simplified computational model of the oxidation of Zr/Al multilayers

A computational model is developed to describe the oxidation of nanolaminates comprising Zr/Al bilayers. The model is developed in light of recent experimental observations of reactive multilayers ignited in air. These suggest that at early stages following the completion of the formation reaction, the oxidation process is more closely described using a surface-reaction controlled growth regime; however, as the oxide layer thickens, transition to the diffusion controlled growth occurs. A simplified computational model is consequently developed that incorporates both regimes of oxide growth. The evolution of the foil temperature is described using an energy balance equation that takes into account the oxidation heat, oxygen intake and radiative heat loss. The computations are implemented to estimate the oxidation heat release rates and the temperature of the oxidizing foil, and to analyze the impact of radiative heat losses. The temperature measurements are then exploited to characterize the transition from the surface-reaction controlled growth regime to the diffusion-limited growth regime.