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Magnetism in CoFe2O4 nanoparticles produced at sub- and near-supercritical conditions of water


The formation of CoFe2O4 nanoparticles has been investigated via three hydrothermal synthesis routes with substantially different heating rates. The syntheses were conducted at various temperatures in the interval 100-390 °C using three different rector setups: 1) conventional Teflon lined steel autoclave, 2) custom-designed spiral reactor and 3) continuous flow reactor. The structural analysis was performed by powder X-ray diffraction and the crystallite size was determined by peak profile analysis employing both Rietveld refinement and whole powder pattern modelling. Transmission electron microscopy was used for morphology characterization and estimation of particles size distribution. Complementary, the crystallites size distribution was found by the whole powder pattern modelling method. The crystallite sizes are highly dependent on the type of reactor used, and crystallite sizes range between 8-15 nm with different morphologies. The continuous flow reactor produced a narrow size distribution compared with the other two types of reactors. At room temperature the as-prepared samples exhibit coercive fields of 0.2-1.2 kOe, with the largest coercive value being 1230 Oe obtained for the sample synthesized using autoclave reactor at 240 °C for 1 hour. Zero-field-cooled/field-cooled susceptibility measurements revealed the blocking temperature to be above room temperature and strong inter-particle interaction was confirmed by Henkel plots. The Curie temperatures measured for the nanoparticles are either comparable or lower than that of the bulk, depending on the particle size.

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Publication details

The article was received on 07 Apr 2017, accepted on 15 Jun 2017 and first published on 15 Jun 2017

Article type: Paper
DOI: 10.1039/C7CE00666G
Citation: CrystEngComm, 2017, Accepted Manuscript
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    Magnetism in CoFe2O4 nanoparticles produced at sub- and near-supercritical conditions of water

    M. Stingaciu, H. L. Andersen, C. Granados-Miralles, A. Mamakhel and M. Christensen, CrystEngComm, 2017, Accepted Manuscript , DOI: 10.1039/C7CE00666G

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