Synthesis and characterization of magnetic cobalt ferrite nanomaterials (original) (raw)
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Journal of Magnetism and Magnetic Materials, 2017
In this work, for first time the ferrofluids based on the cobalt ferrite (CoFe 2 O 4) nanoparticles were prepared by the co-precipitation method at different reaction times (0.5-6.5 hours). Crystal structure, morphology and magnetic properties of the cobalt ferrite nanoparticles and the ferrofluids based on the nanoparticles were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM). The XRD patterns of CoFe 2 O 4 nanoparticles synthesized at different reaction times indicated that all samples are single phase in accordance with inverse cubic spinel structure with space group Fd-3m, and no impurity phase was observed. By increasing the reaction time to 3.5 h, the lattice parameter and the average crystallites size increased and then afterwards decreased by increasing the reaction time. The microscopic studies indicated the formation of nanosized particles with nearly spherical in shape, whereas the average particle size for all samples is found to be less than 50 nm. The results of VSM also showed that the saturation magnetization and coercivity field of the cobalt ferrite nanoparticles and the ferrofluids were influenced by reaction time, whereas the ferrofluids have lower values of magnetic parameters than that of nanoparticles.
Magnetization and stability study of a cobalt-ferrite-based ferrofluid
Journal of Magnetism and Magnetic Materials, 2016
In this study the structural and magnetization properties of a CoFe 2 O 4 -based ferrofluid was investigated using x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), Mössbauer spectroscopy, and magnetic Compton scattering (MCS) measurements. The XRD diagram indicates that the nanoparticles in the ferrofluid are inverse spinel and TEM graph shows that the ferrofluid consists of spherical nanoparticles with an average diameter of 187 1 nm, in good agreement with the size, 19.4 nm, extracted from line broadening of the XRD peaks. According to EDS measurements the composition of the nanoparticles is CoFe 2 O 4 . Mössbauer spectroscopy shows that the cation distributions are (Co 0.38 Fe 0.62 )[Co 0.62 Fe 1.38 ]O 4 . The MCS measurement, performed at 10 K, indicates that the magnetization of the nanoparticles is similar to magnetization of maghemite and magnetite. While the magnetization of the inverse spinels are in [111] direction, interestingly, the magnetization deduced from MCS is in [100] direction. The CoFe 2 O 4 -based ferrofluid is found to be stable at ambient conditions, which is important for applications.
Journal of Magnetism and Magnetic Materials, 2012
Nanostructure of Y-type hexaferrite with composition of Sr 2 Ni 2 Al x/2 Cr x/2 Fe 12−x O 22 (where x are 0, 0.6, 1.2, 1.8, 2.4 and 3) were prepared by sol-gel auto-combustion method. The influence of Al and Cr doping on the structural and magnetic properties has been investigated. The X-ray diffraction (XRD) patterns confirm phase formation of Y-type hexaferrite. The microstructure and morphology of prepared samples were studied by high resolution field emission scanning electron microscope (FESEM) which shows the hexagonal shape for all of the samples. Magnetic properties were characterized using vibrating sample magnetometer (VSM). The magnetic results revealed that by increasing the Al and Cr to the structure, the coercivity was also increased from 840 Oe to 1160 Oe. Moreover it has been shown that with addition of dopants, saturation magnetization (Ms) and remnant magnetization (Mr) were decreased from 39.61 emu/g to 30.11 emu/g and from 17.51 emu/g to 14.62 emu/g, respectively, due to the entrance of nonmagnetic ions into Fe 3+ sites.
Journal of Magnetism and Magnetic Materials, 2019
The magnetic properties of cobalt ferrites nanoparticles prepared using three different processes (thermal decomposition, polyol and co-precipitation synthesis routes) are investigated by X-ray Absorption Spectroscopy and X-ray Magnetic Circular Dichroism. The repartition of cobalt and iron ions amongst the interstitial sites of the spinel structure is determined and correlated with their magnetic properties. The study reports on the influence of the synthesis method on the crystallographic order within a nanoparticle, and hence, on the magnetic anisotropy.
2007
Magnetic nanoparticles with different compositions (Co x Fe 3Àx O 4 , 0pxp0.1) were synthesized from metal salts using a coprecipitation technique to produce magnetic fluids following a peptization technique. The liquid carrier was the hydrocarbon Isopar M and the surfactant was oleic acid. The colloidal-sized ferrimagnetic nanoparticles produced were found to be superparamagnetic. Measurements of the complex magnetic susceptibility were carried out to evaluate the resonant frequency f res , the anisotropy constant K, and anisotropy field H A . f res was found to be a linear function of the cobalt content of the magnetic nanoparticles over the range of cobalt content studied. r
Synthesis and characterization of Fe3O4 magnetic nanofluid
Revista Latinoamericana de Metalurgia y Materiales
Disponible en: www.rlmm.org Trabajo presentado en el congreso "X Iberoamericano de Metalurgia y Materiales (X IBEROMET)"celebrado en Cartagena, Colombia, del 13 al 17 de Octubre de 2008; y se seleccionó para ser remitido a la RLMM para su arbitraje reglamentario y publicación.
Nanomaterials, 2017
Ferrofluids are nanomaterials consisting of magnetic nanoparticles that are dispersed in a carrier fluid. Their physical properties, and hence their field of application are determined by intertwined compositional, structural, and magnetic characteristics, including interparticle magnetic interactions. Magnetic nanoparticles were prepared by thermal decomposition of iron(III) chloride hexahydrate (FeCl 3 ·6H 2 O) in 2-pyrrolidone, and were then dispersed in two different fluids, water and polyethylene glycol 400 (PEG). A number of experimental techniques (especially, transmission electron microscopy, Mössbauer spectroscopy and superconducting quantum interference device (SQUID) magnetometry) were employed to study both the as-prepared nanoparticles and the ferrofluids. We show that, with the adopted synthesis parameters of temperature and FeCl 3 relative concentration, nanoparticles are obtained that mainly consist of maghemite and present a high degree of structural disorder and strong spin canting, resulting in a low saturation magnetization (~45 emu/g). A remarkable feature is that the nanoparticles, ultimately due to the presence of 2-pyrrolidone at their surface, are arranged in nanoflower-shape structures, which are substantially stable in water and tend to disaggregate in PEG. The different arrangement of the nanoparticles in the two fluids implies a different strength of dipolar magnetic interactions, as revealed by the analysis of their magnetothermal behavior. The comparison between the magnetic heating capacities of the two ferrofluids demonstrates the possibility of tailoring the performances of the produced nanoparticles by exploiting the interplay with the carrier fluid.
External magnetic field influence on magnetite and cobalt-ferrite nano-particles in ferrofluid
Chemical Papers, 2018
Using simple optical measurements, the selective spectral behavior of suspended nano-particles of magnetite (Fe 3 O 4) and cobalt-ferrite (CoFe 2 O 4) coated with starch, was observed through switching on/off of external magnetic field. The field strength was varied in the interval 30-300 mT. In these transient regimes, the unexpected and unusually large changes of transmitted light occur. An explanation is suggested, within the model based on ordering of magnetic moments of nanoparticles along the lines of magnetic field into magnetic chains and organization of magnetic chains into spatial structure-a quasi-lattice. This fact indicates the possibility of more efficient local heating of nano-particles in the fast changing magnetic field; for instance when taking magnetic nano-particles for therapeutic purposes.
Journal of Magnetism and Magnetic Materials, 2011
Magnetic fluid based on cobalt ferrite nanoparticles was obtained using a hydrothermal treatment added to the Massart procedure. This treatment increases the average size of the nanoparticles from 11.9 to 18.7 nm and also improves the dispersity and crystallinity of the cobalt ferrite particles. The nanoparticles obtained after the hydrothermal treatment were dispersed in aqueous solvent by the classical procedure for ionic magnetic fluids. The ferrofluid thus obtained is stable at pH 7 and may be useful for hyperthermia applications.
Magnetite-cobalt ferrite nanoparticles for kerosene-based magnetic fluids
Due to the magnetic anisotropy introduced by the Co 2+ ion in octahedral sites of cubic spinel ferrites, it is possible to tailor the magnetic properties by changing the cobalt content. Magnetic fluids with magnetite-cobalt ferrite nanoparticles given by the formula Co (x) Fe (3Àx) O 4 with x ¼ 0, 0.2 and 0.4 were prepared. Kerosene and oleic acid were used as liquid carrier and surfactant, respectively. Spherical magnetic nanoparticles were obtained by coprecipitation from metal salts and ammonium hydroxide; afterwards the magnetic fluids were obtained by a peptization process. Powder properties were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherma (BET), vibrating sample magnetometry (VSM) and fluids by transmission electron microscopy (TEM), thermogravimetric analyzer (TGA), VSM and the short-circuited transmission line technique.