Concentration Of Carbonyl Iron Particles Research Articles

Experimental study of the magnetic field enhanced Payne effect in magnetorheological elastomers.

The dynamic modulus and the loss factor of magnetorheological elastomers (MREs) of various compositions and anisotropies are studied by dynamic torsion oscillations performed in the absence and in the presence of an external magnetic field. The emphasis is on the Payne effect, i.e. the dependence of the elastomer magnetorheological characteristics on the strain amplitude and their evolution with cyclically increasing and decreasing strain amplitudes. MREs are based on two silicone matrices differing in storage modulus (soft, G' ∼ 10(3) Pa, and hard, G' ∼ 10(4) Pa, matrices). For each matrix, the concentration of carbonyl iron particles with diameters of 3-5 μm was equal to 70 and 82 mass% (22 and 35 vol%, respectively) in the composite material. Samples for each filler content, isotropic and aligned-particles, are investigated. It is found that the Payne effect significantly increases in the presence of an external magnetic field and varies with the cyclical loading which reaches saturation after several cycles. The results are interpreted as the processes of formation-destruction-reformation of the internal filler structure under the simultaneously applied mechanical force and magnetic field. Impacts of matrix elasticity and magnetic interactions on the filler alignment are elucidated.

Estimation of magnetic and rheological properties of MR polishing fluid and their effects on magnetic field assisted finishing process

The finishing efficiency in magnetic field assisted finishing (MFAF) process mainly depends on the rheological properties of magnetorheological (MR) polishing medium. A detailed rheological study of MR polishing fluid at different volume concentration of fluid constituents and magnetic field is conducted to predict their contribution on yield stress and viscosity. Magnetic field has the highest contribution followed by carbonyl iron particles (CIPs) concentration to the yield stress and viscosity. It is observed that Herschel–Bulkley model better fits the rheological data than other two models. Also, it has been found that when total solid contents of MR polishing fluid exceeds more than 35%, there is a decrease in the yield stress. From magnetic characterisation, it is observed that saturation magnetisation increases with CIP concentration and decreases with abrasive concentration. The surface finish of stainless steel workpiece improves with an increase in the yield stress and viscosity at higher magnetic field and CIP concentration.

Thermal characterization of magnetically aligned carbonyl iron/agar composites

Composites of magnetic particles into polymeric matrices have received increasing research interest due to their capacity to respond to external magnetic or electromagnetic fields. In this study, agar from Gelidium robustum has been chosen as natural biocompatible polymer to build the matrix of the magnetic carbonyl iron particles (CIP) for their uses in biomedical fields. Heat transfer behavior of the CIP–agar composites containing different concentrations (5, 10, 15, 20, 25 and 30% w/w) of magnetically aligned and non-aligned CIP in the agar matrix was studied using photothermal radiometry (PTR) in the back-propagation emission configuration. The morphology of the CIP–agar composites with aligned and non-aligned CIP under magnetic field was also evaluated by scanning electron microscopy (SEM). The results revealed a dominant effect of CIP concentration over the alignment patterns induced by the magnetic field, which agrees with the behavior of the thermal diffusivity and thermal conductivity. Agar served as a perfect matrix to be used with CIP, and CIP–agar composites magnetically aligned at 20% CIP concentration can be considered as promising ‘smart’ material for hyperthermia treatments in the biomedical field.

Technical Performance of Zirconia-Coated Carbonyl-Iron-Particles Based Magnetic Compound Fluid Slurry in Ultrafine Polishing of PMMA

A kind of zirconia-coated carbonyl-iron-particles (CIPs), which show long-time stability against aqueous, is installed in magnetic compound fluid (MCF) to polish PMMA. Performance (normal polishing force and surface roughness) of zirconia-coated CIP based MCF slurry with different CIP concentrations is investigated. For comparison, the performances of the conventional non-coated CIP (i.e., HQ) based MCF slurry and MRF slurry in which DI-water is employed instead of MF are also examined. In the presence of Al2O3 abrasive particles, the use of zirconia-coated CIP based MCF slurry can not result in better polishing performances compared with conventional HQ CIP based MCF slurry; In the absence of Al2O3 abrasive particles, higher normal polishing force and smoother work-surface were obtained with the zirconia-coated CIP based MCF slurry rather than the MRF slurry; For the zirconia-coated CIP based MCF slurry without abrasive particles, the concentration of zirconia-coated CIP should be less than a certain value (in the current work, 70 wt. %), otherwise MCF slurry shows bad particle dispersion and is easily dried, resulting in the loss of its polishing ability.

Experimental investigations into forces during magnetorheological fluid based finishing process

Magnetorheological fluid based finishing process is a fine finishing process that has been applied to a large variety of brittle materials, ranging from optical glasses to hard crystals. Under the influence of a magnetic field, the carbonyl iron particles (CIPs) and non-magnetic polishing abrasive particles remove material from the surface being polished. Knowledge of forces acting is important to understand the mechanism of material removal. A dynamometer and virtual instrumentation are used to on-line record the normal force and tangential force acting on the workpiece through the magnetorheological (MR) fluid. A full factorial design of experiments is used to plan the experiments and ANOVA to correlate the forces and process parameters. The selected process parameters (volume concentration of CIPs and abrasives, working gap, and wheel rotation) are varied over a range to measure forces during experimentation. The maximum contribution is made by a working gap on the forces developed on the workpiece surface followed by CIP concentration while the least contribution is noticed by the wheel speed.

Study on the properties of magnetorheological gel based on polyurethane

AbstractMagnetorheological gels (MRGs) known as a new kind of magnetorheological material are composite gels containing magnetic particles suspended in polymer gels. In this study, a category of MR polymer gels based on polyurethane (PU) were prepared. The microstructures of these MRGs were observed with a digital microscope. Their rheological properties under both steady shear and oscillation testing were characterized by using a MR rheometer. The viscosity of the PU MRG decreased with the increment of NCO/OH ratio and increased with the increment of the weight concentration of carbonyl iron particles, molecular mass of poly propylene glycol, and applied magnetic field. The storage modulus increased gradually with the increment of applied magnetic field and weight concentration of carbonyl iron particles. The PU MRG exhibits high static shear yield stress (60.8 kPa, at 573 mT) and dynamic shear yield stress (83.9 kPa, at 573 mT) and wide variation range (static shear yield stress: 6–62 kPa, dynamic shear yield stress: 15–85 kPa). These advantages indicate that PU MRG is able to satisfy wide applications. In addition, both static and dynamic shear yield stresses of the MRG samples increase with the increment of molar mass of polypropylene glycol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Magnetic properties of carbonyl iron particles in magnetorheological fluids

Knowledge of the magnetic properties of dispersed magnetic particles is a prerequisite to the design an MR fluid with desired performance. A term specific susceptibility is introduced for characterization of particle susceptibility. The study was performed with the Bartington MS2B magnetic susceptibility system on small samples volume. Specific magnetic susceptibility of iron particles was found to be a linear function of median particle size. Structural change in the fluid, including particle organization, led to susceptibility drift and may affect fluid performance. It was shown that susceptibility data can be used for evaluation of the concentration of carbonyl iron particles in MR fluids.