Formation of non-cubic nanoparticles from cubic MgO in intensified self-burning of magnesium

When Mg metal burns in air the resulting rock-salt MgO smoke consists of perfect [100] cubes of about 100 nm. On contrast, we found that intensification of self-burning of Mg micropowder either by injecting it into oxy-hydrogen diffusion flame or under an infrared laser beam switches the growth mechanism producing mostly single-crystalline spheres and terraced nanoparticles. MgO molecule condensation onto primary spherical nanoparticles can account for generation of terraced nanoparticles with regular steps proportional to the nanoparticle size.