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

TL;DR

This study demonstrates how varying gas pressure in a DC transferred-arc plasma reactor influences the crystalline phases of nanoparticles like Al2O3, AlN, and FeOx, highlighting defect density effects on phase formation.

Contribution

It reveals the critical role of operating gas pressure in controlling nanoparticle crystalline phases during plasma synthesis, a novel insight for material fabrication.

Findings

Higher defect densities favor phase formation at sub-atmospheric pressures

Crystalline phases depend critically on operating gas pressure

X-ray, TEM, and Mossbauer spectroscopy confirm phase variations

Abstract

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.