Magnetorheological properties of ferrofluids containing clustered particles (original) (raw)
Related papers
Journal of Magnetism and Magnetic Materials, 2011
Rheological experiments on relaxation of shear stress in a diluted ferrofluid with clustered iron oxide nanoparticles (f ¼ 0:1 vol%) have been performed. Changes of the stress appearing in the fluid at constant magnetic field strength after a stepwise change of shear rate g Á have been measured. It has been found that the time of the transient, until the shear stress in the fluid will be steady, depends strongly on the strength of the applied magnetic field and shear rate. For vanishing magnetic field slow relaxation has not been observed. The time of the transient in the presence of a magnetic field can reach several minutes. The change of the transient viscosity Z t ¼ 1=g Á ðg Á Þ as a function of the steady viscosity Z t-1 ðg Á Þ shows a linear behavior and depends on magnetic field strength. Those effects can be attributed to the process of structure formation and destruction due to the simultaneous action of an applied magnetic field and shear flow. A similar behavior is known from the rheology of complex fluids like polymer melts or aggregating colloids. We propose a model of the rheological effects based on the assumption that the clusters form linear chains which size distribution is determined by applied magnetic field and shear rate.
In the present investigation, the rheological properties of bi-dispersed magnetorheological (MR) fluid based on Fe3O4 nanosphere and microsphere of iron particles are experimentally investigated. The MR fluid is prepared by substituting nanosphere of 40nm Fe3O4 particles in MR fluids having microsphere iron particles (7-8 μm). Three different weight fractions (0%, 1% and 3%) of nanosphere-microsphere MR fluids are synthesized. In the absence of the magnetic field, substitution of magnetic nanosphere decreases the viscosity lower than without substituted sample at high as well as low shear rate. Upon the application of the magnetic field, the particles align along the direction of the field, which promotes the yield stress. Here too the yield stress value decreases with magnetic nanosphere substitution. This behaviour is explain based on the inter-particle interaction as well as formation of nanosphere cloud around the magnetic microsphere, which effectively reduces the viscosity and works as weak point when chains are formed. Variation of dynamic yield stress with magnetic field is explained using microscopic model. In any event such fluid does not sediment and is not abrasive so it could be useful if not too high yield stress is needed.
An improved properties of bidispersed magneto-rheological fluids
RSC Adv., 2014
We have investigated the influence of nanosized particle concentration on rheological properties when mixed with a magnetorheological (MR) fluid. We have also studied the structural, morphological and magnetic properties of ferrofluid-based MR fluids (F-MRFs). Field-induced rheological and viscoelastic properties of F-MRFs with varying shear rate and strain amplitude have been investigated. The Herschel-Bulkley model was found to fit well with the flow behaviour of F-MRFs. In the oscillatory strain sweep test, F-MRFs show linear viscoelasticity at low strain and the storage modulus (G 0) is higher than the viscous modulus (G 00), which indicates the existence of strong links among the particles that form the microscopic structures. The storage modulus increases with increasing weight fraction of nanosized particles. Furthermore, the loss factor (ratio of G 00 and G 0) was also investigated as a function of magnetic field strength. In addition, time-dependent relaxation behaviour of magnetically induced chain-like structures has also been described. The study reveals that the addition of nanoparticles to MR fluids increases the viscosity as well as the fluid stability under a magnetic field.
Magnetic and Flow Properties of High Magnetization Nanofluids
2004
The paper reviews recent experimental results concerning a wide variety of magnetic nanofluids with high saturation magnetization. Magnetic, rheological and magneto-rheological properties are presented and discussed, especially related to nanostructural processes and colloidal stability in applied magnetic field.
Journal of Colloid and Interface Science, 2000
Static magnetization curves and the magnetorheological effect were used to study the microstructural properties (agglomerate formation) of magnetic fluids and the properties of dispersed nanoparticles. Improved techniques for magnetogranulometry analysis and a formula for the magnetoviscous effect were proposed. The area of applicability of some existing models was studied. The density, distribution, and dimension of particles, as well as the thickness of the nonmagnetic layer were accurately determined from magnetic measurements. The Shliomis diameter and the effective anisotropy constant were determined from rheological and magnetorheological measurements using information obtained from magnetization curves.
Journal of Rheology, 2017
Comprehensive flow and magnetization data obtained previously on the behavior of ferrofluid based magnetorheological fluids (FF-MRF) [Susan-Resiga and V ek as, Rheol. Acta 55(7), 581-595 (2016)] were correlated using a Mason number (M n) defined for these nano-micro composite fluids and the corresponding Casson (Ca) number, instead of the Bingham number used for conventional magnetorheological (MR) fluids. Practically, agglomerate-free, high colloidal stability ferrofluids with Newtonian behavior in the absence of a magnetic field were used as carrier to keep the off-state viscosity as low as possible and to ensure the reproducibility of the MR response of the composite fluid. The apparent viscosities and magnetization values for samples with various nanosized magnetites and micrometer range iron particle volume fractions (from 2.75% to 22.90% and from 4% to 44%, respectively) at different values of magnetic induction and shear rate collapsed on a master curve by using the nondimensional M n and Ca numbers to correlate the measured data. By controlling the volume fraction both at nano-and microlevels, the magnetic and MR properties of the resulting composite fluids can be tailored to offer a highperformance lubricant for semiactive dampers and brakes, as well as for magnetofluidic rotating seals. The M n and Ca numbers offer a design metric based solely on the properties of FF-MRFs and can be reliably scaled to devices of different sizes and operating conditions. V
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017
We investigate the effect of ferrofluid incorporated (5-20% v/v) flake-shaped iron particles in silicion oil based magnetorheological fluid. Bidispersed magnetorheological fluid samples show improved magnetoviscous and viscoelastic properties due to adsorption and colloidal bridge formation of nanoparticles. Highlights Fe3O4 based ferrofluid was incorporated in flake shaped iron based MR fluid. Enhancement the stability and magnetoviscous properties. 10% ferrofluid concentration was established as optimum value to achieve maximum enhancement in MR fluid properties. An increase dynamic efficiency with ferrofluid incorporation was observed.
Nanoparticle Composition of a Ferrofluid and Its Effects on the Magnetic Properties
Langmuir, 2004
Experiments were carried out on a water-based ferrofluid (γ-Fe2O3 with carboxydextran shell) using photon correlation spectroscopy (PCS), atomic force microscopy, and magnetic nanoparticle relaxation measurements. The experiments were designed with the aim to relate the Néel signals that are in theory generated by large single core particles with nanoscopic properties, that is, particle size, particle size distribution, shell properties, and aggregation. For this purpose, the ferrofluid was fractionated by magnetic fractionation and size exclusion chromatography. Nanoparticles adsorbed onto positively charged substrates form a two-dimensional monolayer. Their mean core diameters are in the range of 6 to about 20 nm, and particles above 10 nm are mostly aggregates. The hydrodynamic particle diameters are between 13 and 80 nm. The core diameter of the smallest fraction is confirmed by X-ray reflectometry; the surface coverage is controlled by bulk diffusion. Comparison with the hydrodynamic radius yields a shell thickness of 3.8 nm. Considering the shell thickness to be constant for all particles, it was possible to calculate the apparent particle diameter in the original ferrofluid from the PCS signals of all fractions. As expected, the small cores yielded no Néel relaxation signals in freeze-dried samples; however, the fractions containing mostly aggregates yielded Néel relaxation signals.
Study of Aqueous Dispersions of Magnetic Nanoparticles by Magnetic and Rheological Measurements
2016
The observed magnetic tunability of light transmission through a ferrofluid can be effectively understood in terms of the inter-particle interaction that can be estimated from the magnetic and rheological properties of these fluids. The present study reports complementary magnetic and rheological measurements of aqueous dispersions of ferrite nanoparticles and a commercial ferrofluid. The room temperature magnetization measured in a SQUID magnetometer up to fields of 1 to 2 Tesla showed superparamagnetic behaviour of the particles and the dispersion with the background signal of the liquid showing a diamagnetic behaviour. The room temperature rheological behaviour in zero magnetic field of the fluids was investigated by measuring the viscosity as a function of shear rate from 1-100 s-1. The particle size and the nature of the carrier liquid determine the viscosity and is expected to have an effect on the inter-particle interaction.