Shape and size-controlled synthesis of Ni Zn ferrite nanoparticles by two different routes

Monodisperse Ni-Zn ferrite nanoparticles of different compositions have been synthesized using two different routes, such as sonochemical and polyol methods. In both the cases, the process was attempted in a single reaction in the absence of any surfactant and deoxygenated conditions. X-ray diffraction data on the samples confirmed formation of pure ferrite phase with spinel structure, and indicated that the sonochemical method produces highly crystalline particles compared to the polyol process. Transmission electron microscopy images reveal formation of different shapes, such as cubic, spherical, flower-like and amorphous depending on the method and composition of the ferrite. The magnetic properties of the synthesized Ni-Zn ferrite nanoparticles, measured by vibrating sample magnetometer at room temperature, show that the highest magnetization value was obtained for the composition of Ni0.5 Zn0.5 Fe2O4 in both the synthesis methods. The results of both the methods were discussed by correlating the structure to the magnetism at nanoscales. © 2014 Elsevier B.V. All rights reserved.

Enhanced Ferromagnetic Order in Mn Doped BiFeO3-Ni0.5Zn0.5Fe2O4 Multiferroic Composites

Multiferroic composites of 0.5 BiFeO3-0.5Ni0.5Zn0.5Fe2O4 and 0.5Bi0.95Mn0.05FeO3-0.5 Ni0.5Zn0.5Fe2O4 were prepared by combining sol-gel autocombustion and solid state methods. X-ray diffraction analysis of the composites reveals that the samples are formed as di-phase compounds while retaining the spinel phase for the Ni-Zn ferrite and perovskite phase for the Bi-ferrite. Fourier transform infrared spectroscopy measurements on the composites confirm their structures with the presence of Fe-O and Bi-O bonds. Dielectric measurements on the composites were used to discuss about the possible polarization/conduction mechanisms, phase transitions and magnetoelectric coupling. Room temperature ferroelectric and magnetic hysteresis loop studies on the samples ensure that the Mn doped composite exhibits enhanced remnant polarization as well as saturation magnetization compared to the undoped composite. Moreover, the Mn doping has further translated the composite into magnetically softened with coercivity almost close to zero. The obtained improvements in the dielectric and multiferroic properties of the composites are attributed to the corresponding structural modifications brought about by the Mn doping. Copyright © 2016 American Scientific Publishers All rights reserved.

Fe3O4/TiO2 core/shell nanocubes: Single-batch surfactantless synthesis, characterization and efficient catalysts for methylene blue degradation

Amorphous titania coated magnetite (Fe3O4/TiO 2) nanocubes were successfully synthesized through hydrolysis and condensation of titanium isopropoxide and iron sulfate heptahydrate using single reaction sonochemical process for catalytic applications. X-ray diffractometry, transmission electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy were used to characterize the crystal structure, size and morphology, elemental composition, metal-metal and metal-oxygen bonds of the core/shell nanocubes. Magnetic properties of the samples were measured by a vibrating sample magnetometer at room temperature. Catalytic measurements on the samples showed an excellent efficiency for the degradation of methylene blue, and this efficiency was further promoted remarkably by addition of hydrogen peroxide (H2O2) within only 5 min of reaction time in the absence of ultraviolet irradiation. Even after recycling the sample for six times, the introduced catalyst was found to retain as much as 90% initial efficiency. A possible reaction mechanism for the sonochemical deposition of titania on the surface of magnetite nanocubes and also for the degradation process of methylene blue by the introduced catalyst was discussed. © 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Structural and Magnetic Characterizations of Ni-Zn-Co Ferrite Nanoparticles Synthesized by Sol-Gel Autocombustion Method

Cobalt substituted Ni-Zn ferrite nanoparticles with the formula, Ni0.4Zn0.6-xCoxFe2O4, where x varies from 0.00 to 0.25 in steps of 0.05, were prepared by sol-gel autocombustion method and analyzed for their structural and magnetic properties. The synthesized nanoparticles were subjected to X-ray analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, thermal analysis and magnetic measurements. The X-ray patterns confirm cubic spinel structures with the crystallite sizes in the range from 31.72 nm to 36.87 nm. The particle sizes estimated using electron micrographs are in good agreement with the crystallite sizes obtained from the X-ray data. Infrared data confirms the spinel structure by showing FeA-O and FeB-O stretching vibrations while the thermal data hints at a slight weight gain due to oxidation. The obtained magnetic data suggests a marginal increase in saturation magnetization with the Co substitution at x = 0.10 and 0.25. The results are analyzed in terms of the compositional and structural modifications, and it was found that the variation of magnetic moment was governed by a corresponding change in the oxygen positional parameter in these materials. Copyright © 2016 American Scientific Publishers All rights reserved.

Facile approach for synthesis of high moment Fe/ferrite and FeCo/ferrite core/shell nanostructures

In the present study, we developed a facile approach for synthesis of high magnetic moment monodisperse Fe/ferrite and FeCo/ferrite core/shell nanoparticles. Fe3O4 and CoFe2O4 nanoparticles were at first synthesized through sonochemical process, followed by thermal annealing in presence of hydrogen (H2) gas for 2 h for reduction into Fe and FeCo nanoparticles, respectively. Then, oxidation of Fe and FeCo nanoparticles up to 48 h in air atmosphere resulted in complete formation of Fe/ferrite and FeCo/ferrite core/shell nanostructures. Different analytical techniques such as X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and vibrating sample magnetometer were used to characterize and confirm the successful formation of the core/shell nanostructures. In view of the obtained high magnetic Fe or FeCo core and biocompatible ferrite shell, these core-shell Fe/ferrite and FeCo/ferrite nanoparticles are expected to be promising materials for various bio-sensing applications. © 2014 Elsevier Ltd. All rights reserved.