Synthesis and Compositional Analysis of Permalloy Powder Prepared by Arc-Discharge.

We report the synthesis, compositional, structural and magnetic properties of permalloy powders prepared using an arc-discharge method under different atmospheres. Ion beam analysis results showed that powder prepared in air had a higher concentration of oxygen than those prepared under nitrogen or argon atmospheres. X-ray diffraction measurements showed that powders prepared in air contained magnetite (Fe3O4) and other phases, while powders prepared under nitrogen or argon predominately contained permalloy. The permalloy powders contained a broad range of particle sizes, and nanoparticles as small as 10 nm were evident from transmission electron microscopy data. The saturation magnetizations were significantly lower for the powders prepared in air than those prepared under nitrogen or argon. This can be attributed to oxidation, where the saturation magnetization is predominately from Fe3O4 for powders made in air. The coercive fields were also significantly larger for powders prepared in air, which is consistent with the powders containing different phases when compared with the permalloy powders. Our results show that permalloy powders can be made in nitrogen and argon, allowing for the production of low oxygen content permalloy powders for device applications. Our results also suggest that the use of an iron anode could result in Fe3O4 powders.

Modulation of field emission properties of znO nanorods during arc discharge.

Zinc oxide (ZnO) nanorods have been synthesized via the arc discharge method. Different oxygen partial pressures were applied in the arc discharge chamber to modulate the field emission properties of the as-synthesized ZnO nanorods. Scanning electron microscopy (SEM) was carried out to analyze the morphology of the ZnO nanorods. The ion beam analysis technique of proton induced X-ray emission (PIXE) was performed to probe the impurities in ZnO nanorods. SEM images clearly revealed the formation of randomly oriented ZnO nanorods with diameters between 10-50 nm. It was found that the morphology and the electrical properties of the ZnO nanorods were dependent on the oxygen partial pressure during arc discharge. In addition enhanced UV-sensitive photoconductivity was found for ZnO nanorods synthesized at high oxygen partial pressure during arc discharge. The field emission properties of the nanorods were studied. The turn-on field, which is defined at a current density of 10 microA cm(-2), was about 3 V microm(-1) for ZnO nanorods synthesized at 99% oxygen partial pressure during arc discharge. The turn-on field for ZnO nanorods increased with the decrease of oxygen partial pressure during arc discharge. The simplicity of the synthesis route coupled with the modulation of field emission properties due to the arc discharge method make the ZnO nanorods a promising candidate for a low cost and compact cold cathode material.