Magnetic aligned AlN/epoxy composite for thermal conductivity enhancement at low filler content

We report magnetic alignment of aluminum nitride (AlN) platelets and the outstanding material properties of its polymer composite. The magnetic property of AlN was produced by decorating the surface with strong paramagnetic iron oxide (Fe3O4) nanospheres; the amount of iron oxide deposited is easily controlled by modulating the precursors. With the aid of iron oxide nanospheres, randomly dispersed two dimensional AlN in an epoxy matrix are successfully re-arranged in the vertical direction of the film plane by applying an external magnetic field during epoxy heat curing. Vertically aligned AlN effectively generate thermal transport channels and enhance thermal conductivity from 0.915 W/mK to 1.754 W/mK with 20 vol% filler loading which is a 1.92-fold increase at the low filler concentration compared with randomly oriented composites. The filler alignment will be a promising candidate for thermal interface material fabrication which not only significantly improves the performance, but also prevents the mechanical property degradation caused by extremely high filler loading.