Synthesis of AlN whiskers using cobalt oxide catalyst and their alignments for the improvement of thermal conductivity

We synthesized one dimensional (1-D) AlN whiskers by using the cobalt oxide catalyst-assisted carbothermal reduction method. The formation of AlN whiskers is investigated by the thermo-gravimetric and differential thermal analysis, Fourier-transformed infrared spectra, X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy observations. It was found that Co3O4 droplets on the surfaces of Al2O3 acted as a catalyst for the growth of AlN whiskers by vapor-liquid-solid (VLS) mechanism. In addition, AlN whiskers/PVA composites aligned in parallel with the heat flow direction showed an excellent thermal conductivity about three times higher than those of the perpendicularly aligned whisker composites. •AlN whiskers with high aspect ratio were synthesized from Al2O3.•Co3O4 droplets on the surface of Al2O3 acts as a catalyst for the whisker growth.•AlN whiskers are aligned within PVA in perpendicular and parallel with heat flow.•AlN whisker/PVA composite in perpendicular alignment shows a excellent heat conductivity.