Abstract
Within the frames of this study, the synthesis of a permalloy to be used as a filler for magnetoactive and magnetorheological elastomers (MAEs and MREs) was carried out. By means of the mechanochemical method, an alloy with the composition 75 wt.% of Fe and 25 wt.% of Ni was obtained. The powder of the product was utilized in the synthesis of MAEs. Study of the magnetorheological (MR) properties of the elastomer showed that in a ~400 mT magnetic field the shear modulus of the MAE increased by a factor of ~200, exhibiting an absolute value of ~8 MPa. Furthermore, we obtained experimentally a relative high loss factor for the studied composite; this relates to the size and morphology of the synthesized powder. The composite with such properties is a very perspective material for magnetocontrollable damping devices. Under the action of an external magnetic field, chain-like structures are formed inside the elastomeric matrix, which is the main determining factor for obtaining a high MR effect. The effect of chain-like structures formation is most pronounced in the region of small strains, since structures are partially destroyed at large strains. A proposed theoretical model based on chain formation sufficiently well describes the experimentally observed MR effect. The peculiarity of the model is that chains of aggregates of particles, instead of individual particles, are considered.
Highlights
Magnetic gels and elastomers feature composite materials consisting of a polymer matrix and fine magnetic particles distributed inside it
The dependence of their macroscopic rheological properties on external magnetic fields is one of their fascinating features, which is attractive from the viewpoint of practical applications and challenging for scientific study
This effect is rather related to a transitional condition of the liquid-gel system. It is worth mentioning some values reported for a soft sample (G0 0 = 30 kPa) containing 30 vol.% of carbonyl iron powders (CIPs) by Böse [45]: influenced by a magnetic field of 700 mT, the material showed ∆G0 /G0 0 and ∆G0 equal to ~90 and ~2.5 MPa, respectively
Summary
Magnetic gels and elastomers feature composite materials consisting of a polymer matrix and fine magnetic particles distributed inside it. It is worth mentioning some values reported for a soft sample (G0 0 = 30 kPa) containing 30 vol.% of CIP by Böse [45]: influenced by a magnetic field of 700 mT, the material showed ∆G0 /G0 0 and ∆G0 equal to ~90 and ~2.5 MPa, respectively. Measuring these parameters at 300 mT, the authors of [46] came up with 10 and 1 MPa, which is quite close. In addition to the experimental study of a permalloy-based composite, we present a theoretical model that sufficiently well predicts the MR-effect
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