Abstract
Carbon-based particles, such as graphite and graphene, have been widely used as a filler in magnetorheological elastomer (MRE) fabrication in order to obtain electrical properties of the material. However, these kinds of fillers normally require a very high concentration of particles to enhance the conductivity property. Therefore, in this study, the nanosized Ni-Mg cobalt ferrite is introduced as a filler to soften MRE and, at the same time, improve magnetic, rheological, and conductivity properties. Three types of MRE samples without and with different compositions of Mg, namely Co0.5Ni0.2Mg0.3Fe2O4 (A1) and Co0.5Ni0.1Mg0.4Fe2O4 (A2), are fabricated. The characterization related to the micrograph, magnetic, and rheological properties of the MRE samples are analyzed using scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and the rheometer. Meanwhile, the effect of the nanosized Ni-Mg cobalt ferrites on the electrical resistance property is investigated and compared with the different Mg compositions. It is shown that the storage modulus of the MRE sample with the nanosized Ni-Mg cobalt ferrites is 43% higher than that of the MRE sample without the nanomaterials. In addition, it is demonstrated that MREs with the nanosized Ni-Mg cobalt ferrites exhibit relatively low electrical resistance at the on-state as compared to the off-state condition, because MRE with a higher Mg composition shows lower electrical resistance when higher current flow occurs through the materials. This salient property of the proposed MRE can be effectively and potentially used as an actuator to control the viscoelastic property of the magnetic field or sensors to measure the strain of the flexible structures by the electrical resistance signal.
Highlights
Magnetorheological elastomer (MRE) is one of the smart materials consisting of micron size magnetic particles embedded in rubber matrix
The results demonstrated that for both the off- and on-state conditions, magnetorheological elastomer (MRE) + A1 exhibited a low electrical resistance as compared to MRE + A2, which implied that MRE + A1 is more sensitive towards the changes in force
The nanosized Ni-Mg nanosized Ni-Mg cobalt-ferrites are randomly dispersed in the MRE samples
Summary
Magnetorheological elastomer (MRE) is one of the smart materials consisting of micron size magnetic particles embedded in rubber matrix. By implementing the nanoparticles as an additive or filler in MRE, the magnetic and rheological properties of MRE can be appropriately tuned. The main technical contribution of this work is to fabricate a new MRE associated with the nanosized Ni-Mg cobalt ferrites with different concentrations of Mg, and to experimentally investigate various properties of the proposed MRE including the field-dependent viscoelastic properties and electrical resistance. The nanosized Ni-Mg cobalt ferrites are introduced as a filler in MRE fabrication to enhance magnetic and electric properties of MRE with the least brittleness. The nanosized Ni-Mg cobalt ferrites exhibit high magnetic remanence and large surface activities [37] Their properties are believed to demonstrate better magnetic, rheological, as well as electrical properties of MRE. Evaluations show that MRE with a higher content Mg exhibits higher electrical resistance, in the range of 1% to almost 400% in off- and on-state conditions, due to the easier movement of the particles
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