Production of nanoparticles of MgO, BaO, and Al$_2$O$_3$ in a premixed flame and its relation to the flame structure

Formation of nanoparticles of magnesium, barium, and aluminum oxides in a fuel-lean oxy-acetylene flame is studied by means of flame sampling. The size distributions and concentrations of particles are measured in various areas of the flame. Possible reaction paths are considered. MgO and BaO nanoparticles are demonstrated to form in the reaction zone where there is a high concentration of radicals. Formation of Al$_2$O$_3$ particles is hindered by the reaction AlO + AlO$_2$ $\to$ Al$_2$O$_3$ being termolecular.