Vertical filler alignment of boron nitride/epoxy composite for thermal conductivity enhancement via external magnetic field

Anisotropic boron nitride (BN) was vertically aligned along the direction of heat transport using a magnetic field. Iron oxide nanoparticles deposited onto the BN surface act as a magnetically responsive material allowing particle alignment. The amount of iron oxide deposited, and therefore the magnetic response, is easily controlled by modulating the precursors. The polarization of paramagnetic iron oxide in the magnetic field leads to the formation of vertical particle arrangements. The thermal conductivity of the synthesized vertically aligned composite increased from 1.765 W m−1 K−1 to 3.445 W m−1 K−1 with 30 vol% filler loading that is a 1.96-fold increase compared with a randomly oriented composite. The filler content affected both particle dispersion and arrangements, with homogeneously dispersed fillers aggregating due to induced dipole interactions into column-like structures with favorable thermal transport properties.