Signature of nano alumina condensation during metal combustion

Abstract

The work is focused on thermal radiation originating from aluminum oxide nanoparticles formed during the combustion of an aluminum and copper oxide (Al/CuO) thermite. The light emission signature allows for the identification of condensation features important for the global energy balance of burning metal-containing systems. From a fundamental science perspective, identifying light emission signatures associated with phase changes, and in particular, with condensation that is accompanied by high energy release, will lead to new knowledge with widespread applications. The recently developed calibration-free pyrometry approach is used to isolate the radiation of interest during combustion. Processing the obtained spectra made it possible to detect the solidification of the resulting nano alumina. Knowledge of the phase transition temperature enabled the determination of the temporal behavior of the absolute temperature of aluminum oxide nanoparticles during their formation by condensation from gaseous metal suboxides. This ability to measure absolute temperature, as opposed to its reciprocal value available with the original calibration-free pyrometry approach, further enhances the diagnostic method's capabilities. The general implications of revealed peculiarities of nano alumina formation for detailed modeling of the combustion of metal-containing systems are discussed.