Joel Espino-Portillo; Dora A. Cortés-Hernández; José C. Escobedo-Bocardo; Héctor J. Sánchez; Mirna M. G. Saldívar-Ramírez; Laura E. De-León-Prado
Abstract
The effect of mixed ferrites nature and that of several coatings on the magnetic properties and thus, on the heating ability of nanoparticles, was studied. The Mg0.4Ca0.6Fe2O4 and Mn0.5Ga0.5Fe2O4 ferrites, synthesized by sol-gel method, followed by heat treatment, were coated with oleic acid + Pluronic® ...
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The effect of mixed ferrites nature and that of several coatings on the magnetic properties and thus, on the heating ability of nanoparticles, was studied. The Mg0.4Ca0.6Fe2O4 and Mn0.5Ga0.5Fe2O4 ferrites, synthesized by sol-gel method, followed by heat treatment, were coated with oleic acid + Pluronic® F-127, carboxymethyl-dextran sodium or polyvinylpyrrolidone. An average particle size of 12 and 15 nm was obtained for the Mg-Ca and Mn-Ga ferrites, respectively. Samples, before and after coating, revealed a heating capacity over 42°C and a superparamagnetic behaviour. The compounds accomplished the requirements of heating ability and specific absorption rate for magnetic hyperthermia treatment. The Mn0.5Ga0.5Fe2O4 system was more efficient than the Mg0.4Ca0.6Fe2O4 system. Copyright © 2018 VBRI Press.
Nandeibam Nilima; Mamata Maisnam; Sumitra Phanjoubam
Abstract
Li-Ni-Co ferrite/SiO2 composites with representative formula Li0.41Ni0.1Co0.08Fe2.41O4+ xSiO2 (i.e., x = 0wt. %, 5wt. %,10wt. % and 20wt. %) were prepared by sol-gel method. The prepared composites were pre-sintered at 600ºC for 2 hrs and then finally sintered at 1000ºC for 6 hrs. X-ray diffraction ...
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Li-Ni-Co ferrite/SiO2 composites with representative formula Li0.41Ni0.1Co0.08Fe2.41O4+ xSiO2 (i.e., x = 0wt. %, 5wt. %,10wt. % and 20wt. %) were prepared by sol-gel method. The prepared composites were pre-sintered at 600ºC for 2 hrs and then finally sintered at 1000ºC for 6 hrs. X-ray diffraction studies showed diffraction peaks indicating single phase with spinel structure. However, peaks of SiO2 were found in composites of higher (x). The microstructure of the samples was studied by using Scanning Electron Microscopy. The crystallite size and average grain size were found to decrease with increase of SiO2 content. The room temperature frequency variation of dielectric constant and dielectric loss was measured from 100Hz-1MHz and they showed a dispersive behavior. The variation has been explained by Verwey mechanism of electron hopping and Koop’s two-layer model. The addition of SiO2 plays significant role in influencing the various structural, microstructural and electrical properties. Uniform and refined microstructures are observed with the addition of SiO2 and this reduces the value of dielectric constant and loss significantly, which is desirable for high frequency applications. The results obtained and mechanisms involved are discussed. Copyright © 2017 VBRI Press.
Sunita Khangembam; Maisnam Victory; Waikhom Surchandra; Sumitra Phanjoubam
Abstract
Recent technological breakthroughs and the desire for new functions generate an enormous demand for synthesizing new materials through different ways and methods which show superior properties compared with their pure counterparts. Presently, polycrystalline zinc doped nickel ferrites having the compositional ...
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Recent technological breakthroughs and the desire for new functions generate an enormous demand for synthesizing new materials through different ways and methods which show superior properties compared with their pure counterparts. Presently, polycrystalline zinc doped nickel ferrites having the compositional formula Ni1-xZnxFe2O4 where x = 0.0, 0.1, 0.2 and 0.4 were synthesized. Sol-gel auto combustion method was adopted for the preparation of these ferrites since it provides a simple and economic alternative technique ensuring good stoichiometric control, production of particles with narrow size distribution in a relatively shorter time, good homogeneity and high sinterability at lower temperature. Structural studies were carried out by XRD. Various structural properties like lattice parameter, crystallite size and density were calculated from the XRD data. Micro structural studies were carried out using Scanning Electron Microscopy (SEM), while the elemental compositions of all the samples were studied by Energy Dispersive X-ray Analysis (EDAX). The frequency variation of room temperature dielectric constant and dielectric loss was studied in the frequency range 100Hz – 1MHz and dispersive behavior was observed. The room temperature dc resistivity of all the samples was also investigated. Zn substituted nickel ferrites are found to be useful in microwave and electronic devices. Copyright © 2017 VBRI Press.
Rakesh Saroha; Aditya Jain; A. K. Panwar
Abstract
The effects of ZnO nanoparticle coating on the physicochemical and electrochemical properties of LiFePO4 (LFP) have been investigated in this work. ZnO-modified LiFePO4 cathode materials were synthesized via sol-gel and modified by ZnO nanoparticle using ball mill method. The amount of ZnO additive is ...
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The effects of ZnO nanoparticle coating on the physicochemical and electrochemical properties of LiFePO4 (LFP) have been investigated in this work. ZnO-modified LiFePO4 cathode materials were synthesized via sol-gel and modified by ZnO nanoparticle using ball mill method. The amount of ZnO additive is chosen as a controlling factor to tune ZnO content over the surface of LFP particles. Structure and morphology of the LFP material with and without ZnO-coating layer were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectra. The XRD patterns reveal that the proper phase of LFP is formed with the ordered olivine-type orthorhombic structure of Pnma space group, and no impurity phase like LiZnPO4 has been noticed. AC conductivity measurements have shown that the ZnO-modified LFP samples significantly assists in lowering the resistance of cathode active material and enhancing the conductivity. It is found that the 2.5 wt% ZnO-doped LFP exhibits the highest conductivity than the 5 wt% ZnO and 1 wt% ZnO doped LFP or the un-doped sample. Among the synthesized samples, LFPZ2.5 displays highest discharge capacity 160 (±5) mAhg-1 (~94% of the theoretical capacity of LiFePO4) at 0.1C rate. These results indicate that 2.5 wt% ZnO coated pristine LFP sample proves to be alternative material for automotive industry and it may be possible alternate of cathode materials in hybrid electric vehicles. Copyright © 2016 VBRI Press
