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1.
We propose the methods for studying electrokinetic phenomena in magnetic colloidal systems (magnetic fluids), which make it
possible to use the magnetic properties of particles of the disperse phase. Electrophoresis and the sedimentation potential
in a kerosene-based magnetic fluid are studied. It is shown that only a small part (approximately one-thousandth) of all disperse
particles in the magnetic fluid under investigation are charged, the sign of the particle charge being negative. 相似文献
2.
Seiichi Sudo Hirayoshi TakayanagiShinichi Kamiyama 《Journal of magnetism and magnetic materials》2011,323(10):1348-1353
This paper describes the dynamics of the air cavity created by water entry of magnet-magnetic fluid projectile. The impact of a projectile, permanent magnet coated with kerosene-based magnetic fluid, on the free surface of water is investigated experimentally. The cavity of air in water created by the impact of the projectile is observed with the high-speed video camera system. Effects of the adsorption of magnetic fluid and alternating magnetic fields are revealed. 相似文献
3.
C.N. Marin P.C. FanninI. M?l?escu P. BarvinschiA. Ercu?a 《Journal of magnetism and magnetic materials》2012,324(4):434-439
We report on the frequency and field dependent complex magnetic susceptibility measurements of a kerosene-based magnetic fluid with iron oxide nanoparticles, stabilized with oleic acid, in the frequency range 0.1-6 GHz and over the polarising field range of 0-168.4 kA/m.By increasing polarising field, H, a subsidiary loss-peak clearly occurs in the vicinity of the ferromagnetic resonance peak, from which it remains distinct even in strong polarising fields of 168.4 kA/m. This is in contrast to other reported cases in which the intra-well relaxation process is manifested only as a shoulder of the resonance peak, which vanishes in polarising fields larger than that of 100 kA/m.The results of the XRD analysis connected to the anisotropy field results confirm that the investigated sample contains particles of magnetite and of the tetragonal phase of maghemite.Taking into account the characteristics of our sample, the theoretical analysis revealed that the intra-well relaxation process of the small particles of the tetragonal phase of maghemite may be responsible for the subsidiary loss peak of the investigated magnetic fluid. 相似文献
4.
Hydrodynamic Properties of Fe3O4 Kerosene-Based Ferrofluids with Narrow Particle Size Distribution 下载免费PDF全文
We investigate the hydrodynamic properties of Fe3O4 kerosene-based ferrofluids with narrow particle size distribution. The ferrofluids are synthesized by improving chemical coprecipitation technique. A narrow distribution of 8.6-10.8nm particle sizes is obtained from the magnetization curve with the free-form model based on the Bayesian inference theory. The fitting result is consistent with average particle size obtained from x-ray diffraction. With the increase of applied magnetic field and magnetic particle concentration, apparent viscosity of ferrofluids increases. At concentration 4.04%, the type of flow for the ferrofluid transforms from Newtonian to Bingham plastic fluid as the applied magnetic field increases. 相似文献
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The pair distribution function of a monodisperse magnetic fluid simulated by a liquid made of dipolar hard spheres with constant
magnetic moments is calculated. The anisotropy of the pair distribution function and the related structure factor of scattering
in a dc uniform magnetic field are studied. The calculation is performed by diagrammatic expansion in the volume concentration
of particles and the interparticle magnetic-dipole interaction intensity using a thermodynamic perturbation theory. Limitation
by three-particle diagrams makes it possible to apply the results obtained to magnetic fluids with a moderate concentration.
Even for low-concentration and weakly nonideal magnetic fluids, the anisotropic interparticle magnetic-dipole correlations
in a magnetic field lead to the repulsion of particles in the direction normal to the field and to the formation of particle
dimers along the field. 相似文献
7.
A magnetic field induced agglomeration of magnetic and μm-sized copper non-magnetic particles in magnetic fluid with several
volume concentrations of magnetite and copper particles was studied by means of optical microscope equipped with video camera.
Transmission of light through two crossed polarizers and thin magnetic fluid and magnetic fluid composites film as a function
of magnetic field was investigated. The experimental data showed that the presence of copper particles influences the aggregation
processes of magnetic particles in magnetic fluids and transmissivity of light.
Dedicated to Dr. Anton Zentko on the occasion of his 60th birthday.
This work was supported by the Slovak Academy of Sciences within the framework of Project GAV No. 4001. 相似文献
8.
V. I. Petrenko M. V. Avdeev V. L. Aksenov L. A. Bulavin L. Rosta 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(1):161-164
Magnetic fluids (magnetite/oleic acid/benzene) with excesses of a surfactant (oleic acid) are studied using small-angle neutron scattering. Solutions of oleic acid in benzene are also studied to reveal whether an aggregation of acid molecules can occur. It is shown that oleic acid does not form micelles in benzene in the range of concentrations under study (up to volume fractions of 35%). It follows from our results that the excess of a surfactant (less than a volume fraction of 25%) in a magnetic fluid does not lead to a noticeable aggregation of its particles. At the same time, an increase in the attraction between free surfactant molecules in the magnetic fluid (compared to pure solutions of oleic acid in benzene) is observed. If the excess of a surfactant is greater than 25%, then the stability of the magnetic fluid is sharply violated, which leads to the aggregation of magnetic particles. 相似文献
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10.
Partial slip effect on non-aligned stagnation point nanofluid over a stretching convective surface 下载免费PDF全文
The present study inspects the non-aligned stagnation point nano fluid over a convective surface in the presence of partial slip.Two types of base fluids namely water and kerosene are selected with Cu nanoparticles.The governing physical problem is presented and transformed into a system of coupled nonlinear differential equations using suitable similarity transformations.These equations are then solved numerically using midpoint integration scheme along with Richardson extrapolation via Maple.Impact of relevant physical parameters on the dimensionless velocity and temperature profiles are portrayed through graphs.Physical quantities such as local skin frictions co-efficient and Nusselt numbers are tabularized.It is detected from numerical computations that kerosene-based nano fluids have better heat transfer capability compared with water-based nanofluids.Moreover it is found that water-based nanofluids offer less resistance in terms of skin friction than kerosene-based fluid.In order to authenticate our present study,the calculated results are compared with the prevailing literature and a considerable agreement is perceived for the limiting case. 相似文献
11.
Magnetic particles freely moving in a fluid may organize themselves into dense phases, bulk clusters, or linear chains. The dynamics of particles forming a chain is analyzed theoretically taking into account the magnetic dipole interaction as well as the Van der Waals molecular interaction. The vibrational spectrum has two branches (the magnetic branch associated with the rotation of the magnetic moment of a particle and the elastic branch associated with the displacement of particles). In the case of particles with constant mass density and magnetic moment, which is interesting for applications, these two modes are in fact independent; i.e., the effects of mode hybridization are weak. However, these effects can be manifested for hollow particles. From analysis of the vibrational spectrum, the criterion for the chain stability to a transition to a denser phase is established. 相似文献
12.
A kinetic model is proposed to describe the low-frequency magnetodynamics of antiferromagnetic nanoparticles suspended in a fluid. Because of their small size, apart from an anisotropic magnetic susceptibility typical of antiferromagnets, these particles also have a constant magnetic moment caused by sublattice decompensation. An orientational crossover takes place in such a nanosuspension (colloid) when magnetized by a constant field: the axes of easy particle magnetization that were initially aligned along the field become oriented perpendicularly. This effect changes significantly the characteristics of the system’s magnetic response: the dynamic susceptibility spectrum and the relaxation time in a pulsed field. 相似文献
13.
Henrik Bohr Constan?a Providência Jo?o da Providência 《Brazilian Journal of Physics》2012,42(1-2):68-76
In the present paper the magnetization of a high density relativistic fluid of elementary particles is studied. At very high densities, such as may be found in the interior of a neutron star, when the external magnetic field is gradually increased, the energy of the normal phase of the fluid remains practically constant before extremely high magnetic fields are reached. However, if pion condensation occurs, the energy decreases linearly while the magnetic field strength increases, so that a non vanishing magnetization, independent of the magnetic field, is present. The expression of the magnetization is derived by first considering and solving the Dirac equation of a fermion in interaction with a magnetic field and with a chiral sigma-pion pair. The solution provides the energies of single-particle states. The energy of the system is found by summing up contributions from all particles in the particle fluid. For nuclear densities above 2 to 3ρ 0, where ρ 0 is the equilibrium nuclear density, the resulting magnetic field turns out to be rather huge, of the order of 1017 Gauss. 相似文献
14.
A. V. Nagornyi V. I. Petrenko L. A. Bulavin M. V. Avdeev L. Almásy L. Rosta V. L. Aksenov 《Physics of the Solid State》2014,56(1):91-96
Structural parameters of the magnetite-oleic acid-decalin magnetic fluid at various excesses of oleic acid (up to 25 vol %) have been determined using small-angle neutron scattering. Based on the comparison of the behavior of oleic acid in the magnetic fluid and in the pure solvent (decalin), it has been concluded that the interaction between the molecules of free (unadsorbed) surfactant changes in the presence of magnetic nanoparticles. However, the system remains stable and does not form aggregates of magnetic particles or free oleic acid. These results are compared with the previously presented data for similar benzene-based magnetic fluids. 相似文献
15.
在磁场作用下,在磁流体里添加非磁性颗粒(non-magnetic particles,NPs),可以使得NPs形成不同的结构,操控NPs的运动从而影响磁流体的特性,这种应用逐渐受到了研究者的关注.为了更好地操控磁流体里NPs的运动,本文采用一种多物理模型研究在外加磁场作用下,磁流体中两个NPs沉降的运动过程.其中,用格子玻尔兹曼方法模拟磁流体的运动,外加磁场对磁流体的影响用一种自修正方法求解泊松方程,这个自修正方法可以使欧姆定律满足守恒定律.NPs之间的偶极干扰力采用偶极力模型,同时采用一种相对过渡平滑的共轭边界条件处理NPs与磁流体交界面的流固干扰以避免磁场密度过渡的突变.本文主要探究两个NPs在磁流体中的沉降,揭示磁场作用下NPs的相互干扰原理;同时,对控制NPs运动时的参数进行调节,得到NPs不同的运动轨迹,达到操控颗粒运动的目的.本研究可对NPs在磁流体中的应用提供定量的分析结果,对NPs在工业上的应用提供有力的理论支撑. 相似文献
16.
General equations governing the stability of stratified fluid in a stratified porous medium in the presence of suspended particles and variable horizontal magnetic field, separately, have been derived. Assuming stratifications in density, viscosity, suspended particles number density, medium porosity, medium permeability and a magnetic field of exponential form the dispersion relations have been obtained. Systems have been found to be stable for stable stratifications and unstable for unstable stratifications. A system which was unstable in the absence of magnetic field can be completely stabilized by a magnetic field for a certain wave-number range. The behaviour of growth rates with respect to fluid viscosity, medium permeability, suspended particles number density and magnetic field has been examined analytically. 相似文献
17.
《Journal of magnetism and magnetic materials》2005,293(1):526-531
In this study, magnetic resonance was used to investigate lauric acid-coated magnetite-based magnetic fluid particles and particles which are surrounded by a double layer of phospholipid molecules (magnetoliposomes). The data reveal the presence of monomers and dimers in both samples. Whereas evidence for a thermally induced disruption of dimers is found in the magnetic fluid, apparently, the bilayer phospholipid envelop prevents the dissociation in the magnetoliposome samples. 相似文献
18.
《Journal of magnetism and magnetic materials》1987,68(2):160-170
The magnetic hyperfine splitting in Mössbauer spectra of superparamagnetic particles, induced by an external magnetic field, has been calculated. Numerical results have been obtained both for isolated particles with a finite value of the magnetic anisotropy energy constant and for strongly interacting particles. Moreover, analytical approximations are derived. The theoretical results are compared with results of experimental studies of supported α-Fe particles and magnetic particles in ferrofluids. 相似文献
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20.
Tunable magnetoben-optic modulation based on magnetically responsive nanostructured magnetic fluid 下载免费PDF全文
Magnetic fluid is a kind of functional composite material with nanosized structure and unique optical properties. The tunable magneto-optic modulation of magnetic fluid under external magnetic field, achieved by adjusting the polarization direction of incident light, is investigated theoretically and experimentally in this work. The corresponding modulation depth and response time are obtained. The accompanying mechanisms are clarified by using the theory of dichroism of magnetic fluid and the aggregation/disintegration processes of magnetic particles within magnetic fluid when the external magnetic field turns on/off. 相似文献