The Effect of Dissolved Oxygen in Arc Medium on Crystal Structure and Optical Properties of Iron Based Nanoparticles Prepared via Dc Arc Discharge in Water

Abstract

Electrical arc discharge in liquid is a fast, cost-effective and an environmentally benign way for synthesis of nanomaterials. In this research iron based nanoparticles were synthesized via DC arc discharge submerging in deoxidized water and the effect of dissolved oxygen in arc discharge medium on morphology, crystal structure and optical properties of nanoparticles were studied. For nanoparticle synthesis a discharge current of 40 A was applied between pure iron electrodes which were submerged in deoxidized water and kept about 8cm below the surface of water. Dissolved oxygen removal was performed by nitrogen gas bubbling for long time before arc discharge. Furthermore during synthesis a pressurized stream of nitrogen gas was directed perpendicular to the surface of deoxidized water. In addition, a sample was prepared in water without deoxidization under the same synthesis condition. The nanoparticles were characterized by X-ray diffraction (XRD), UV-visible spectroscopy and scanning electron microscopy (SEM). SEM results revealed that the particles were spherical with aspect ratios of about one. The average size of nanoparticle is below 30nm in both samples. It was concluded that the reaction of dissolved oxygen molecules available in deionized water with iron nanoparticles leads to oxidation of nanoparticles during nucleation, nanoparticles formation and especially after synthesis. Therefore the oxygen atom in water molecules and oxygen ions in arc plasma do not have a significant effect on oxidation of nanoparticles. These results demonstrate the importance of oxygen removal of water in arc discharge method for preparation of pure metallic nanoparticles without considerable oxidation.