DC transferred arc thermal plasma assisted growth of nanoparticles with different crystalline phases

The control of the crystalline phases of the nanoparticles grown in a direct-current transferred-arc plasma-assisted reactor is reported. The crystalline phases of the as synthesized nanoparticles are shown to critically depend on the operating gas pressure. The paper reports about the change in the crystalline phases of three distinct compounds namely aluminium oxide (Al2O3), aluminium nitride (AlN) and iron oxide (FexOy). The major outcome of the present work is that the phases having higher defect densities are more probable to form at the sub-atmospheric operating pressure. The variations in the crystalline structures are discussed on the basis of the equilibrium defect density formed during the homogeneous nucleation. The as synthesized nanoparticles were examined by X-ray diffraction analysis and transmission electron microscopy. In addition, the confirmatory analysis for the crystalline phases of the as synthesized iron oxides was carried out with the help of Mossbauer spectroscopy.