Abstract
Dielectric properties of two series of magnetoactive elastomers (MAEs) based on a soft silicone matrix containing 35 vol% of magnetic particles were studied experimentally in a wide temperature range. In the first series, a hybrid filler representing a mixture of magnetically hard NdFeB particles of irregular shape and an average size of 50 μm and magnetically soft carbonyl iron (CI) of 4.5 μm in diameter was used for MAE fabrication. MAEs of the second series contained only NdFeB particles. The presence of magnetically hard NdFeB filler made it possible to passively control MAE dielectric response by magnetizing the samples. It was shown that although the hopping mechanism of MAEs conductivity did not change upon magnetization, a significant component of DC conductivity appeared in the magnetized MAEs presumably due to denser clustering of interacting particles resulting in decreasing interparticle distances. The transition from a non-conducting to a conducting state was more pronounced for hybrid MAEs containing both NdFeB and Fe particles with a tenfold size mismatch. Hybrid MAEs also demonstrated a considerable increase in the real part of the complex relative permittivity upon magnetization and its asymmetric behavior in external magnetic fields of various directions. The effects of magnetic filler composition and magnetization field on the dielectric properties of MAEs are important for practical applications of MAEs as elements with a tunable dielectric response.
Highlights
The development of new smart materials that allow controlling their properties using external stimuli is one of the complex interdisciplinary tasks facing various fields of modern science, such as materials science, chemical engineering, chemical physics, and others.Nowadays, smart materials are widely used in science and technology, and there is an ever-growing need for new materials
InInthis thethe dielectric spectroscopy studies of magnetoactive elastomers (MAEs) containing magnetically thiswork, work, dielectric spectroscopy studies of MAEs containing magnetically hard NdFeB microparticles were performed in a wide temperature range
Two types of hard NdFeB microparticles were performed in a wide temperature range
Summary
The development of new smart materials that allow controlling their properties using external stimuli is one of the complex interdisciplinary tasks facing various fields of modern science, such as materials science, chemical engineering, chemical physics, and others. We demonstrate that MH filler particles within hybrid MAEs give us an opportunity to induce an anisotropy and, to control MDE and conductivity by application of magnetic field after material fabrication. This is promising for the design of magnetic field sensors or controlled shielding materials on the basis of hybrid MAEs. the composition, the method of synthesis and study of MAEs samples are introduced.
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