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We investigate the effect of Co2+ ion doping in magnetite (Fe3O4) on its crystal structure, magnetic properties, and phase stability during air and vacuum annealing. The nanoparticles are prepared by co-precipitation method and the particles are characterized by XRD, small angle x-ray scattering (SAXS), themogravimetric and differential scanning calorimetry (DSC), and vibrating sample magnetometer. The SAXS analysis on the doped samples show the most probable size, shape, and the polydispersity of particles, synthesized with different fractions (0–0.6) of Co2+ ion doping remains almost the same. On increasing cobalt content ferrimagnetic to the antiferromagnetic hematite (α-Fe2O3) phase transformation temperature is found to increase dramatically. For 0.1 fraction of Co2+ metal ion doping, an enhancement of 100 °C in the γ-Fe2O3 to α-Fe2O3 phase transition temperature is observed in the air annealed samples, whereas magnetic nature remains stable up to 1000 °C in vacuum annealed samples. On increasing the...

We investigate the effect of particle size on reduction temperatures in surfactant capped fine iron oxide (Fe3O4) nanoparticles in size ranging from 7 to 3 nm using in situ high temperature X-ray diffraction (HTXRD). The 7 nm size particles are reduced to metallic α-Fe and FeO phase at 400°C and remains stable up to 600°C. On further heating, α-Fe phase grows at the expense of FeO and the growth process completes at 800°C. Above 900°C, α-Fe is converted to γ-Fe phase and at 1000°C, a part of γ-Fe phase is converted to α-Fe2O3. As the size is decreased from 7 to 3 nm, the onset of reduction to metallic Fe and FeO is enhanced by 100 to 200°C, due to the increased surface spin disorder. Irrespective of the initial particle size, the final phase obtained after annealing at 1000°C and cooled back to room temperature was a mixed phase of α-Fe and α-Fe2O3. Thermo Gravimetric Analysis coupled Mass Spectra (TGA-MS) confirm that the evolved carbon from the oleic acid assist the removal of oxygen atom from Fe3O4 lattice, facilitating the reduction of Fe3O4 into α-Fe and FeO. The magnetization data of the final products before and after vacuum annealing are consistent with final phases observed in the XRD.

In this paper, we report the variations in the crystal structure, average particle size, and magnetic properties of ZnFe2O4 nanoparticles on thermal annealing, using in situ high temperature x-ray diffraction (XRD). Fine powder of ZnFe2O4 nanoparticles with an average particle size of 9.3nm, prepared through coprecipitation technique, has been used in these studies. The powder is heated from room temperature to 1000°C, under vacuum in steps of 100°C and the XRD pattern is recorded in situ. A sudden drop in the lattice parameter from 8.478to8.468A is observed at 800°C, above which it increases with increasing temperature. After annealing at 1000°C, the lattice parameter reduces from 8.441to8.399A and the magnetization value increases from 5to62emu∕g, suggesting the possibility of a conversion of the cubic structured ZnFe2O4 from normal to inverse spinel structure due to canting of ions between the tetrahedral and octahedral interstitial sites. During annealing, the Zn2+ ions move from tetrahedral site to o...

Cutting of irradiated zircaloy metal clad ceramic fuel pellets requires a special cutting saw that can be remotely operated. The remote operation is essential because of the pyrophoric nature of zircaloy metal and high radiation field associated with the irradiated fuel elements. Conventional saws cannot meet the operational requirements because these are not readily amenable for remote operation and maintenance. Hence we have developed a new laboratory scale cutting saw for cutting radioactive samples remotely.