Abstract
RF thermal plasma was used to prepare nano-sized boron-rich compounds and the mechanism of nanoparticle formation was investigated by estimating the homogeneous nucleation rate. In order to synthesize aluminum dodecaboride (AlB_<12>), the premixed feed powders in different compositions of aluminum and boron were injected into the thermal plasma operated in different working gas conditions. High boron-ratio and thermal conductive helium were favorable to enhance AlB_<12> synthesis in final product due to higher boiling point of boron than aluminum. In the nanoparticle synthesis process, vaporized raw materials in the high temperature region were rapidly cooled and nucleate in the plasma tail region with a steep temperature gradient. At this point it was predicted that boron nucleates first and then aluminum nucleates. Therefore, AlB_<12> is formed by condensation of aluminum to the boron nuclei.
