Effect of surface tension on the temperature of burning metal droplets

An effect of Laplace pressure resulting in elevated boiling temperatures for fine burning metal droplets is discussed. The effect is evaluated for both Al and Mg. An increase in the boiling temperature suggests that the temperature of fine Al particles can become equal to or even higher than the temperature of the vapor phase Al flame. The high particle surface temperature may be associated with accelerated surface reaction rates. For Al, such surface reactions may generate vapor-phase aluminum suboxides, resulting in a reduced heat effect and extended burn times for fine particles and nanoparticles. For Mg, the particle temperature remains below the vapor phase flame temperature despite an elevated boiling point. For fine particles, surface reaction producing solid MgO growing directly on the particle surface is possible.