Filler orientation of boron nitride composite via external electric field for thermal conductivity enhancement

Abstract In this study, anisotropic boron nitride (BN) was vertically aligned along the direction of heat transport using an external electric field. A titanium oxide (TiO 2 ) nanoparticle, which has a superior dielectric property, was deposited onto the BN surface to act as an electrically responsive material that allowed for particle alignment. Because of the relatively low dielectric property of BN, it was not observed morphological change under the electric field. After the surface modification using titanium oxide, the polarization of highly dielectric titanium oxide in the electric field led to the formation of vertical particle arrangements. The through-plane thermal conductivity of the synthesized vertically aligned composite increased from 0.78 W m −1 K −1 to 1.54 W m −1 K −1 , while through-plane thermal conductivity was decreased 1.17 W m −1 K −1 to 0.84 W m −1 K −1 , with 20 vol% filler loading. This is a 1.9-fold increase and 0.72-fold reduction compared with the conductivity of a randomly oriented composite. Moreover, this vertically aligned filler composite exhibits better mechanical properties based on the same thermal conductivity.