Rheological and electrical properties of cobalt-based magnetorheological elastomer

Abstract

In most studies, carbonyl iron particles (CIP) were merged with carbon-based particles such as graphite (Gr) or carbon black (CB) particles as fillers to enhance the electrical properties of magnetorheological elastomers (MRE). Although the electrical properties were improved, excessive implementation of particle in MRE led to brittle phase which caused decrement of properties such as elasticity. Hence, this study examined a single material, cobalt particles, as a filler to enhance the rheological and electrical properties in MRE. The selection of cobalt particles is due to its dual properties – magnetic and electrical. A total of three MREs containing 53, 60 and 67 wt% of cobalt were fabricated through mixing and curing processes. Characterization related to physicochemical properties of MRE samples was analysed by using X-Ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). Then, the rheological properties of the MRE in various strengths of magnetic field intensity between 0 to 0.8 T were conducted by using a rheometer. Subsequently, the effect of the cobalt on the electrical properties was investigated and compared with different applied forces towards the MRE. The physicochemical properties indicate the presence of cobalt has influenced the rheology and electrical properties of the MRE. Both properties were enhanced with the increase of cobalt content that embedded in the silicone matrix. Even though, the initial storage modulus of MRE increased from 0.28 to 0.52 MPa, the magnetorheological (MR) effect has enhanced from 57.14% to 82.69%. On the contrary, the MRE resistance decreased when increasing the applied force from 1 to 10 kg. In sum, the findings show a higher cobalt content in MRE contributed to a higher MR effect, and simultaneously lower the electrical resistance. The finding suggests the potential of cobalt particles as a filler in the MRE fabrication for future sensing applications.