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A. Yu. Zubarev - One of the best experts on this subject based on the ideXlab platform.

  • Kinetics of doublet formation in bi-component magnetic suspensions: the role of the magnetic permeability anisotropy
    Physical Review E, 2017
    Co-Authors: M. Lopez-lopez, F. Nogueras-lara, L. Rodriguez-arco, N. Guigo, N. Sbirrazzuoli, A. Yu. Zubarev, S. Lacis, P. Kuzhir
    Abstract:

    Micron-sized particles (microbeads) dispersed in a suspension of magnetic nanoparticles, i.e. Ferrofluids, can be assembled into different type of structures upon application of an external magnetic field. This paper is devoted to theoretical modeling of a relative motion of a pair of microbeads (either soft ferromagnetic or diamagnetic) in the Ferrofluid under the action of applied uniform magnetic field which induces magnetic moments in the microbeads making them attracting to each other. The model is based on a point dipole approximation for the magnetic interactions between microbeads mediated by the Ferrofluid, however the Ferrofluid is considered to possess an anisotropic magnetic permeability thanks to field-induced structuring of its * Corresponding author e-mail: kuzhir@unice.fr 2 nanoparticles. The model is tested against experimental results and shows generally better agreement with experiments than the model considering isotropic magnetic permeability of Ferrofluids. The results could be useful for understanding kinetics of aggregation of microbeads suspended in a Ferrofluid. From a broader perspective, the present study is believed to contribute to a general understanding of particle behaviors in anisotropic media.

  • Viscoelastic properties of Ferrofluids.
    Physical Review E, 2010
    Co-Authors: Dmitry Chirikov, L. Yu. Iskakova, Sergei Fedotov, A. Yu. Zubarev
    Abstract:

    The paper deals with theoretical study of non linear viscoelastic phenomena in Ferrofluids placed in magnetic field. Our attention is focused on the study of nonstationary flow and Maxwell-like relaxation of the macroscopical viscous stress after alternation of the shear rate. We propose that these phenomena can be explained by finite rate of evolution of chainlike aggregates, consisting of the Ferrofluid particles. Statistical model of the chains growth-disintegration is suggested. In this model the chain-single particle mechanism of the chains evolution is considered, the effects of the chain-chain interaction are ignored. The proposed model allows us to estimate the time-dependent function of distribution over number of particles in the chain. Having determined this function and using methods of hydromechanics of Ferrofluids with chainlike aggregates, we have studied evolution of the Ferrofluid viscosity after stepwise alternation of the fluid shear rate. The estimated time of relaxation is in a reasonable agreement with experimental results. Thus, our analysis shows that the observed macroscopical viscoelastic phenomena in Ferrofluids can be provided by evolution of the chain ensemble.

  • Rheological properties of Ferrofluids with microstructures
    Journal of Physics: Condensed Matter, 2006
    Co-Authors: A. Yu. Zubarev, L. Yu. Iskakova
    Abstract:

    This paper presents results of a theoretical study of the effects of linear chain-like as well as bulk drop-like heterogeneous aggregates on the rheological properties and behaviour of Ferrofluids. The results demonstrate that the appearance of both these internal structures leads to a strong (one–two orders of magnitude) increase of the Ferrofluid effective viscosity under the action of the magnetic field applied parallel to the gradient of the Ferrofluid flow. When the Ferrofluid fills a thin channel (gap) placed into a normal magnetic field, the drop-like structures can overlap with the channel. In the case of a rigid connection between the drop-like domains and the channel walls, the appearance of elastic and yield stress effects on the Ferrofluid is expected.

  • Yield stress in thin layers of Ferrofluids
    Physica A: Statistical Mechanics and its Applications, 2006
    Co-Authors: A. Yu. Zubarev, L. Yu. Iskakova
    Abstract:

    Abstract We present results of theoretical study of quasielastic behavior of Ferrofluid filling a thin flat gap, placed into perpendicular magnetic field. When the field exceeds a certain critical magnitude, magnetic particles form dense discrete domains, elongated along the field, and linking the gap boundaries. Due to these bridges between the gap boundaries, the Ferrofluid exhibits quasielastic properties with respect to shear strain in the plane of the gap. We estimated the elastic modules as well as the yield stress of the system, depending on magnetic field and concentration of magnetic particles in the Ferrofluid. Analysis shows that there are at least two microscopical mechanisms of transition from the elastic to fluid behavior of the Ferrofluid. The first one is connected with the loss of the mechanical equilibrium of the domains, slopped, under the shear stress, with respect to applied magnetic field. The second mechanism is connected with breakup of the “bridge” into two separate drops, when the shear strain exceeds some critical magnitude. Estimates show that for real Ferrofluids the second mechanism is more probable.

Stefan Odenbach - One of the best experts on this subject based on the ideXlab platform.

  • Ferrofluids: Magnetically Controllable Fluids And Their Applications
    2010
    Co-Authors: Stefan Odenbach
    Abstract:

    Synthesis and Characterization.- The Preparation of Magnetic Fluids.- Magnetic Spectroscopy as an Aide in Understanding Magnetic Fluids.- Magnetic and Crystalline Nanostructures in Ferrofluids as Probed by Small Angle Neutron Scattering.- Basic Theory.- Basic Equations for Magnetic Fluids with Internal Rotations.- Ferrohydrodynamics: Retrospective and Issues.- Ferrofluid Dynamics.- Heat and Mass Transfer Phenomena.- Rheological Properties.- Statistical Physics of Non-dilute Ferrofluids.- Magnetic Fluid as an Assembly of Flexible Chains.- Magnetoviscous Effects in Ferrofluids.- Magnetorheology: Fluids, Structures and Rheology.- Applications.- Targeted Tumor Therapy with "Magnetic Drug Targeting": Therapeutic Efficacy of Ferrofluid Bound Mitoxantrone.

  • Capillary viscosimetry on Ferrofluids.
    Journal of physics. Condensed matter : an Institute of Physics journal, 2008
    Co-Authors: L M Pop, Stefan Odenbach
    Abstract:

    Experiments performed for different Ferrofluids under shear flow have shown that an increase of the magnetic field strength applied to the sample yields an increase of the fluid's viscosity, the so called magnetoviscous effect. It has been shown that the magnitude of the effect is strongly related to the modification of the microstructure of Ferrofluids and can be influenced by varying both the dipole-dipole interaction between the particles and the concentration of large particles within the fluid. This result has been further used to synthesize new Ferrofluids which, on one hand, are more compatible for technical applications but, on the other hand, led to difficulties for the experimenters in measuring the viscous behavior in the presence of a magnetic field. To overcome this problem, a specially designed Ferrofluid-compatible capillary viscometer has been developed. Within this paper, the experimental setup as well as experimental results concerning the investigation of the magnetoviscous effect in both diluted and concentrated cobalt-based Ferrofluids are presented.

  • Microstructure and rheology of Ferrofluids
    Journal of Magnetism and Magnetic Materials, 2005
    Co-Authors: Loredana Mirela Pop, Stefan Odenbach, A. Wiedenmann, Nina Matoussevitch, Helmut Bönnemann
    Abstract:

    Abstract Experimental studies made for different Ferrofluid samples under shear flow have shown that increasing the magnetic field strength yields an increase of the fluids viscosity, the so-called magnetoviscous effect, while increasing shear rate leads to a decrease of the magnitude of the viscosity (shear thinning). The change of the viscosity with magnetic field strength is theoretically explained as an effect of chain-like structure formation in Ferrofluids whereas its magnitude depends on the particle–particle interaction. Both effects, the shear thinning and the magnetoviscous effect, can therefore be related to the microstructure and microstructure dynamics of Ferrofluids. Using a specially designed rheometer, Ferrofluids having different magnitude of the magnetoviscous effect were investigated by small-angle neutron scattering. Correlated to the structure formation in the fluid, the scattered intensity shows a variation with the magnetic field and shear rate only in the case of the fluids with a high magnetoviscous effect. The presented results show that there is a strong connection between the rheological behaviour of Ferrofluids and their microstructure.

  • The microstructure of Ferrofluids and their rheological properties
    Applied Organometallic Chemistry, 2004
    Co-Authors: Loredana Mirela Pop, Stefan Odenbach, J. Hilljegerdes, A. Wiedenmann
    Abstract:

    One of the most important features of Ferrofluids is the possibility to change their physical properties, especially their viscosity, by means of moderate magnetic fields. This capability makes Ferrofluids very useful in the fields of engineering, medicine and fundamental research. Rheological experimental results, as well as theoretical studies, correlate the change of the viscosity of a sheared Ferrofluid under the influence of a magnetic field, the so-called magnetoviscous effect, to the internal structure formation under certain external conditions. To obtain information about the microstructure of Ferrofluids, experiments using the small-angle neutron scattering (SANS) technique have been carried out. Three magnetite-based Ferrofluids with different particle-particle interactions, and thus various magnitudes of the magnetoviscous effect, were investigated. Using a specially designed rheometer, SANS experiments were performed for different shear rates and magnetic field strengths in order to observe the modification of the microstructure in Ferrofluids and to associate the SANS information with their macroscopical behaviour. The scattering patterns obtained show a good agreement with the qualitative model that explains the magnetoviscous effect.

  • Ferrofluids: magnetically controllable liquids
    PAMM, 2002
    Co-Authors: Stefan Odenbach
    Abstract:

    The make up, properties and applications of suspensions containing magnetic particles with a size of about 10 nm - usually called Ferrofluids - will be discussed. The specific interest in these fluids bases on the fact that they show normal liquid behavior coupled with superparamagnetic properties. That means that it is possible to control the flow and the properties of Ferrofluids by means of moderate magnetic fields in the order of about 50 mT. The magnetically controllable forces on Ferrofluids open wide fields for basic research as well as for technical applications. Some of the applications of Ferrofluids entered everyday live meanwhile and gained high commercial importance. Beside the discussion of the basic properties of these liquids, particular interest will be drawn to the change of their viscosity in the presence of magnetic fields. This effect usually called magnetoviscous effect is one of the most vivid fields of Ferrofluid research at present.

B Jeyadevan - One of the best experts on this subject based on the ideXlab platform.

  • mn zn ferrite nanoparticles for Ferrofluid preparation study on thermal magnetic properties
    Journal of Magnetism and Magnetic Materials, 2006
    Co-Authors: R Arulmurugan, G Vaidyanathan, S Sendhilnathan, B Jeyadevan
    Abstract:

    Abstract Mn1−xZnxFe2O4 (with x varying from 0.1 to 0.5) ferrite nanoparticles used for Ferrofluid preparation have been prepared by chemical co-precipitation method and characterized. Characterization techniques like elemental analysis by atomic absorption spectroscopy and spectrophotometry, thermal analysis using simultaneous TG-DTA, XRD, TEM, VSM and Mossbauer spectroscopy have been utilized. The final cation contents estimated agree with the initial degree of substitution. The Curie temperature ( T c ) and particle size decrease with the increase in zinc substitution. In the case of particles with higher zinc concentration, both ferrimagnetic nanoparticles and particles exhibiting superparamagnetic behavior at room temperature are present. In addition, some of the results obtained by slightly altering the preparation condition are also discussed. The precipitated particles were used for Ferrofluid preparation. The fine particles were suitably dispersed in heptane using oleic acid as the surfactant. The volatile nature of the carrier chosen helps in altering the number concentration of the magnetic particles in a Ferrofluid. Magnetic properties of the fine particles and Ferrofluids are discussed. Ferrofluids having Mn0.5Zn0.5Fe2O4 particles can be used for the energy conversion application utilizing the magnetically induced convection for thermal dissipation.

  • co zn ferrite nanoparticles for Ferrofluid preparation study on magnetic properties
    Physica B-condensed Matter, 2005
    Co-Authors: R Arulmurugan, G Vaidyanathan, S Sendhilnathan, B Jeyadevan
    Abstract:

    Abstract Co–Zn substituted nanoferrites having stoichiometric composition Co1−xZnxFe2O4 with x ranging from 0.1 to 0.5 were prepared by chemical coprecipitation method. The precipitated particles were used for the preparation of Ferrofluid. Ferrofluids having Co0.5Zn0.5Fe2O4 particles could be used for the energy conversion application utilizing the magnetically induced convection for thermal dissipation. The final estimated cation contents, agreed with the initial degree of substitution. The powder samples were characterized by XRD, TEM, VSM and Mossbauer studies. The precipitated particles showed single-phase fcc spinel structure for all compositions of zinc. The magnetic parameters such as Ms, Hc, Mr, Tc and particle size were found to decrease with the increase in zinc substitution. In the case of particles with higher zinc concentration, both ferrimagnetic nanoparticles and particles exhibiting superparamagnetic behavior were present. The fine particles were suitably dispersed in heptane using oleic acid as the surfactant. Volatile nature of the carrier chosen helped in altering the number concentration of the magnetic particles in a Ferrofluid.

Sophie Neveu - One of the best experts on this subject based on the ideXlab platform.

  • Bad Neighbour, Good Neighbour: How Magnetic Dipole Interactions Between Soft and Hard Ferrimagnetic Nanoparticles Affect Macroscopic Magnetic Properties in Ferrofluids
    Nanoscale, 2020
    Co-Authors: Niéli Daffé, Sophie Neveu, Jovana Zečević, Kalliopi Trohidou, Marcin Sikora, Mauro Rovezzi, Claire Carvallo, Marianna Vasilakaki, Johannes Meeldijk, Nadejda Bouldi
    Abstract:

    Fluids responding to magnetic fields (Ferrofluids) offer a scene with no equivalent in nature to explore long-range magnetic dipole interactions. Here, we studied the very original class of binary Ferrofluids, embedding soft and hard ferrimagnetic nanoparticles. We used a combination of X-ray magnetic spectroscopy measurements supported by multi-scale experimental techniques and Monte-Carlo simulations to unveil the origin of the emergent macroscopic magnetic properties of the binary mixture. We found that the association of soft and hard magnetic nanoparticles in the fluid has a considerable influence on their inherent magnetic properties. While the Ferrofluid remains in a single phase, magnetic interactions at the nanoscale between both types of particles induce a modification of their respective coercive fields. By connecting the microscopic properties of binary Ferrofluids containing small particles, our findings lay the groundwork for the manipulation of magnetic interactions between particles at the nanometer scale in magnetic liquids.

  • size selective chemical synthesis of tartrate stabilized cobalt ferrite ionic magnetic fluid
    Journal of Colloid and Interface Science, 2002
    Co-Authors: Sophie Neveu, Michel Robineau, Delphine Talbot
    Abstract:

    Ionic magnetic fluid (Ferrofluid) is a stable suspension of magnetic nanoparticles in water. Cobalt ferrite nanoparticles are interesting in view of high-density recording storage. The size of the magnetic particles strongly influences the physical properties of the Ferrofluids. In this study, we describe the synthesis of ionic magnetic fluid in the presence of tartrate ions. By varying the amount of organic ligands, nanoparticles in a large range of size are obtained: the mean diameter varies from 3 to 10 nm. The effect of tartrate ions on the stability of the ionic magnetic fluid is also studied in relation with the size of the magnetic particles and the amount of adsorbed ligand.

P.c. Fannin - One of the best experts on this subject based on the ideXlab platform.

  • Theoretical evaluation of the heating rate of Ferrofluids
    Journal of Thermal Analysis and Calorimetry, 2014
    Co-Authors: Catalin Nicolae Marin, Iosif Malaescu, P.c. Fannin
    Abstract:

    This paper presents a theoretical model for the determination of the effective specific heat of a Ferrofluid. With this model, we have evaluated different approximations to the effective specific heat c eff of a water-based Ferrofluid with magnetite particles and propose a practical equation for the computation of the effective heating rate of Ferrofluids. In the case of the investigated Ferrofluid, the heating rate is shown to increase approximately linearly with the increase of the particle volume fraction φ. This result is of practical importance in cancer treatment by magnetic hyperthermia of tissues and other thermal applications.

  • On the use of dielectric formalism in the representation of Ferrofluid data
    Journal of Molecular Liquids, 1996
    Co-Authors: P.c. Fannin
    Abstract:

    Abstract The major advances of recent times in the understanding of Ferrofluids (magnetic fluids), are in no small way due to the application of dielectric formalism in the representation of Ferrofluid data. The magnetic analogues of the equations of Debye, Cole-Cole, Cole-Davidson, Havriliak - Negami and Frohlich, are just a number of examples of those that have lightened the burden of workers involved in the measurement and analysis of Ferrofluids. In this paper it is demonstrated how these equations may be employed to determine the magnetic properties, in particular the magnetisation decay, of Ferrofluids from measured data.