Synthesis of AlN nanopowder coated with a thin layer of C, using a thermal plasma reactor

Abstract

High-purity nanocrystalline aluminum nitride powders were synthesized by using a 12 kW non-transferred arc plasma. The synthesis was conducted in a versatile, new designed, one-chamber thermal plasma reactor (TPR). The novel experimental assembly incorporated better working conditions like: high temperature gradient between the crucible and reactor's wall, and high super-saturation of the system by nitrogen and carbon. Thermodynamic modelling of the synthesis was conducted in order to achieve the best conditions for AlN formation. In this study, aluminum discs of Al 1100 were used as precursor material and pure nitrogen was the only gas used as reagent and plasmogenic gas. Nanopowders collected from reactor's wall were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-Ray diffraction (XRD). Synthesized h-AlN nano-powders were found to be free of oxides and aluminum metal. A thin carbon-layer around the particles was detected. TEM results indicated that the carbon-layer was around 5 and 10 nm. This outcome could make a significant difference with other synthesis reported in the literature since the occurrence of the carbon-layer, could delay AlN oxidation, prevent hydration, and could avoid the agglomeration of the particles.