Papers by Author: S.N. Dolia

Abstract: Particle size has significant effect on the magnetic properties of fine particles. In this work, Cu0.2Ni0.8Fe2O4 nano-particles have been synthesized by the co-precipitation method. Different particle sizes were obtained by annealing the samples at various temperatures. The X-ray diffraction (XRD) patterns confirm the formation of cubic spinel structure. The particle size was found to enhance with increasing the annealing temperature. The saturation magnetization and the blocking temperature increase with particle size, which is a typical characteristic of the superparamagnetic behaviour. The dc magnetization measurements show that the samples are superparamagnetic above the blocking temperatures and the blocking temperature of the nanoparticles correlates with the size of the nanoparticles that is found to increase as the function of the particle size. The hysteresis curves show reduction in saturation magnetization in case of nanoparticles as compared to their bulk counterparts. This has been explained on the basis that the magnetic moments in the surface layers of a nanoparticle are in a state of frozen disorder. However, the saturation magnetization increases with particle size, which is a characteristic property of the single domain superparamagnetic particles.

Abstract: Corrosion studies were carried out using potentiodynamic polarization method on amorphous, nanocrystalline and crystalline states of the alloy Ti60Ni40 in 0.5 M H2SO4 and 0.5 M HNO3 aqueous media at room temperature. The nanocrystalline state of Ti60Ni40 was obtained by removing about 10 μm from the air side surface (crystalline state) by polishing. The presence of nanocrystalline phase was confirmed by X-ray diffraction (XRD). It was found from polarization results that the corrosion current density was higher in the amorphous state than in the nanocrystalline state in both 0.5 M H2SO4 and 0.5 M HNO3 aqueous media. These results are corroborated by the weight loss studies which were carried out in both of these media. Results are discussed in the paper in the light of data reported in the literature on similar type of alloys.

Abstract: Potentiodynamic polarization studies were carried out on amorphous, nanocrystalline and crystalline states of the alloy Ti60Ni40 in 0.1 M HNO3, 0.5 M HNO3 and 1 M HNO3 aqueous solutions at room temperature. It was observed that the amorphous state exhibited higher corrosion current density than that by the nanocrystalline state. These results are corroborated by the weight loss studies performed on the different structural states of Ti60Ni40 alloy in 0.1 M HNO3, 0.5 M HNO3 and 1 M HNO3 aqueous media. Thus the nanocrystalline state is least prone to corrosion than the amorphous and the crystalline states.