Multi-field processing of micro-platelets for magneto-active applications

The orientation and spatial distribution of magnetic particles in smart mechano-magnetic composites are key to enhancing their actuation capability. In this study, we present a new experimental approach to tune the orientation and assembly of barium hexaferrite (BHF) micro-platelets in liquid polymers by applying uniform magnetic and alternating current (AC)-electric fields. First, we investigated the assembly of BHFs under different electric field amplitudes and frequencies in the silicone elastomer. After establishing the optimum parameters for electric and magnetic alignment, four different microstructures are fabricated namely (a) random (b) electrically aligned (c) magnetically aligned and (d) simultaneously electrically and magnetically aligned. Finally, microstructural and property characterizations are performed using OM, XRD, SEM, and VSM measurements. Our findings demonstrate that a variety of microstructures can be obtained depending on the nature of the applied external field: in the absence of any field, BHF platelets are organized as small stacks, owing to their intrinsic magnetic polarization. In contrast, application of an electric field creates chain-like structures where the orientation of the BHF stacks inside the chains is random. Application of a magnetic field enhances rotation of the BHF stacks, which are found to rotate inside the chain in directions dictated by the magnetic field. Finally, by applying simultaneous electric and magnetic fields while also tuning the processing parameters, BHF-composite film with a squareness ratio of 0.92 is obtained. In order to further extend the actuation capability of resulting composites, we will also experiment with electroactive polymer matrices such as P(VDF–TrFE–CTFE) terpolymer to fabricate a multiferroic material that can actuate under both electric and magnetic field.