Influence of He and N₂ plasma on in situ surface passivated Fe nanopowders by plasma arc discharge

Abstract

DC transferred arc plasma method was employed for the synthesis of core (Fe)-shell (Fe oxide) nanopowders under N 2 and He atmospheres. The phase and elemental compositions were studied by x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS) techniques. The structural and magnetic properties were investigated by high-resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. XRD and EDS results confirmed the presence of iron and iron oxide. From HRTEM, the average particle sizes of 32, 47 and 71 nm and 20, 26 and 37 nm were obtained against processing currents of 50, 100 and 150 A under N 2 and He atmospheres respectively. The average particle size values were found to increase with increases in processing current. Spherical and hollow hexagonal nano-structures were obtained under N 2 atmosphere whereas spherical and distorted cubes were formed under He atmosphere. The elemental mapping revealed the presence of oxygen on the surface and Fe in the core of the nanoparticles.

Morphological, electronic, and magnetic properties of multicomponent cobalt oxide nanoparticles synthesized by high temperature arc plasma

“…The XRD patterns of the Air series samples indicates presence of strains that should be compatible with H c value, seen from the hysteresis curves. Indeed, Koushika et al showed that particle distribution following a particular trend or aligned in a particular direction results in a lower H c [42]. Our HRTEM images hardly show any particular alignment of nanoparticles.…”

“…Magnetic properties also depend on stresses in the system. Due to the thermal stress inside the lattice, the particle-particle interaction reduces H c [42]. The XRD patterns of the Air series samples indicates presence of strains that should be compatible with H c value, seen from the hysteresis curves.…”