Effects of surface nitrification on thermal conductivity of modified aluminum oxide nanofibers-reinforced epoxy matrix nanocomposites

Aluminum oxide (Al ₂O ₃) nanofibers were treated thermally under an ammonia (NH ₃) gas stream balanced by nitrogen to form a thin aluminum nitride (AlN) layer on the nanofibers, resulting in the enhancement of thermal conductivity of Al ₂O ₃/epoxy nanocomposites. The micro-structural and morphological properties of the NH ₃- assisted thermally-treated Al ₂O ₃ nanofibers were characterized by X-ray diffraction (XRD) and atomic force microscopy (AEM), respectively. The surface characteristics and pore structures were observed by X-ray photoelectron spectroscopy (XPS), Zeta-potential and N ₂/77 K isothermal adsorptions. From the results, the formation of AlN on Al ₂O ₃ nanofibers was confirmed by XRD and XPS. The thermal conductivity (TC) of the modified Al ₂O ₃ nanofibers/epoxy composites increased with increasing treated temperatures. On the other hand, the severely treated Al ₂O ₃/epoxy composites showed a decrease in TC, resulting from a decrease in the probability of heat-transfer networks between the filler and matrix in this system due to the aggregation of nanofiber fillers.