Magnetic-Field Sensitivity of Storage Modulus for Bimodal Magnetic Elastomers

Abstract

The magnetic-field dependence of the storage modulus for bimodal magnetic elastomers consisting of carbonyl iron with a diameter of 2.8 μm (magnetic) and aluminum hydroxide with a diameter of 1.4 μm (nonmagnetic) was measured, and the effect of nonmagnetic particles on the magnetic-field sensitivity of the storage modulus was investigated. The coefficient of the magnetic-field sensitivity for the monomodal magnetic elastomer increased from 0.018 to 0.026 mT for the bimodal one by embedding nonmagnetic particles of 6.6 vol %. At volume fractions above 5.4 vol %, the bimodal magnetic elastomer exhibited significant nonlinear viscoelasticity at 0 mT and a high storage modulus at 500 mT, simultaneously, the coefficient of the magnetic-field sensitivity demonstrated high values. This strongly indicates that both the particles form a particle network at the off-field, and they make a well-developed chain structure under magnetic fields. The time profiles of the storage modulus for bimodal magnetic elastomers can be fitted by a linear combination of two exponential functions with two characteristic times showing the alignment of magnetic particles. The alignment time for the fast and slow processes was distributed around 3.3 ± 0.3 and 176 ± 12 s, respectively. The alignment time was independent of the volume fraction of the nonmagnetic particles; however, the increment in the storage modulus for the fast process significantly increased at volume fractions above 5.4 vol %. It was also revealed that the coefficient of the magnetic-field sensitivity can be scaled by a power function of the increment in the storage modulus divided by the off-field modulus, ΔG'/G', not only for the bimodal magnetic elastomers but also for the monomodal ones.

Magnetic Elastomers with Smart Variable Elasticity Mimetic to Sea Cucumber

“…A magnetic gel or elastomer with magnetic particles exhibited a significant increase in storage modulus exceeding 500 times with respect to the off-field modulus [18,19]. Moreover, bimodal magnetic elastomers consisting of both magnetic and nonmagnetic particles demonstrated an enhanced magnetic response due to the chains of magnetic particles associated with nonmagnetic ones [20][21][22][23][24][25][26]. These results indicate that the nonmagnetic particle functions as an intermediator of stress transfer between the chains of magnetic particles although the particles are not moved by magnetic fields.…”

Efficient Chain Formation of Magnetic Particles in Elastomers with Limited Space

“…The increase in the storage modulus for bimodal magnetic elastomers containing zinc oxide particles of 12 vol.% was 500 kPa, which was achieved by applying a magnetic field of 500 mT, which is 4.2 times that used for the monomodal one (120 kPa) [9]. The increase in the storage modulus for bimodal magnetic elastomers containing aluminum hydroxide particles of 6.6 vol.% was 3.27 MPa, which is 4.3 times that used for the monomodal one (754 kPa) [11]. Figure 1 shows the schematic illustrations representing the mechanism for the MR effect for bimodal magnetic elastomers in our previous study and the scenario for that in the present study.…”

“…When a magnetic field is applied to a magnetic elastomer, the elasticity increases due to the chain structure formation (restructuring) of magnetic particles, which is called the magnetorheological (MR) effect. So far, we have investigated the MR effect for polyurethane-based magnetic elastomers and found that bimodal magnetic elastomers with magnetic and nonmagnetic particles exhibit a significant MR effect compared with monomodal magnetic elastomers [9][10][11][12][13].…”

“…In our past studies, zinc oxide with a diameter of 10.6 µm or aluminum hydroxide with a diameter of 1.4 µm was used as nonmagnetic particles [9,11]. The increase in the storage modulus for bimodal magnetic elastomers containing zinc oxide particles of 12 vol.% was 500 kPa, which was achieved by applying a magnetic field of 500 mT, which is 4.2 times that used for the monomodal one (120 kPa) [9].…”

Time-dependent electric conductivity and dielectric breakdown for magnetic soft composites at high-electric fields

“…[6][7][8][9] We have also reported that bimodal magnetic elastomers consisting of magnetic and nonmagnetic particles exhibit the enhanced magneto mechanical response compared to the monomodal magnetic elastomers. [10][11][12][13] Recently, magnetic elastomers attract much attention as damping materials which can control the resonant frequency of vibration by magnetic fields. It is because that the elastic modulus of magnetic elastomer can be changed continuously by magnetic fields.…”