Kinetics of small single particle combustion of zirconium alloy

We present quantitative kinetic information regarding small, 1-10 μm in diameter, single particle combustion of Zr-rich metal alloy foils subjected to either mechanical impacts or laser-ablation. The lights from combustion of metal fragments were recorded on a high-speed camera. The particle size was determined by the motion analysis of individual particle trajectory based on an aerodynamic drag law and further verified by the microstructure and chemical composition analysis of recovered post-burn particles. The measured particle sizes show a log-normal distribution centered at around 3.1 μm in diameter, and the composition of recovered particles is that of fully oxidized ZrO2. The temperature evolution of each particle along the space/time-trajectory is determined based on the thermal emission from combustion using a single-color photographic spectro-pyrometry. The result indicates that the particle has reached the maximum combustion temperature of 4000 K, well beyond the melting temperature of ZrO2, and undergone the solidification of molten ZrO2 during the cooling stage. It also shows that the maximum combustion temperature decreases linearly with increasing the particle diameter, following the correlation t aD1.5-1.8 between the burn time (t) and the particle diameter (D). Combining the particle size, the burn time, and the particle temperature, both temperature and mass burn rates are obtained as a function of particle size. As the particle size increases, the temperature burn rate decreases, whereas the mass burn rate goes in the opposite direction.