On the electric and magnetic alignment of magnetoactive barium hexaferrite-PDMS composites

This study demonstrates how to judiciously use two different external fields to engineer a polymer-based composite that responds to both electric and magnetic fields. Specifically, we demonstrate the electric and magnetic alignment of M-type Barium Hexaferrite (BF) in polydimithylsiloxane (PDMS) to obtain a multifunctional composite whose electrical and magnetic properties depend on the orientation of the BF. First, the BFs are electrically aligned in the polymer matrices by applying an AC electric field. From optical microscopy (OM) imaging, the optimal electrical alignment conditions are determined, and those parameters are used to fabricate the composites. After the composite is electrically aligned and partially cured, magnetic field is then applied. Under the magnetic field, BFs are further aligned in-plane and out-of-plane along their magnetic c-axis within the chains that formed during electrical aligning. Following complete cure, the microstructures from the OM image show parallel chain formation. Vibrating Sample Magnetometry (VSM) and XRD results confirm BFs are crystallographically aligned along their magnetic c-axis. The textured BF-PDMS composites are found to have anisotropic magnetic and dielectric properties. The possibility of electrical alignment of magnetic particles will open up new doors to manipulate and design particle-modified polymers for different applications.