Effects of Al particle size and nitrogen pressure on AlN combustion synthesis

This study investigates the combustion synthesis of AlN fibers using an NH4Cl additive and reports the effects of Al particle size (3, 30, and 180 µm) and N2 pressure (0.10, 0.25, and 0.50 MPa) on the purity and morphology of AlN fibers. The combustion temperature was directly measured during the synthesis to elucidate the formation mechanism of the AlN fibers. The phase purity and morphology of the products were studied using X-ray diffraction and scanning electron microscopy, respectively. When the particle size of Al was reduced from 180 to 3 µm, the purity of the AlN product increased significantly owing to the large reaction area, which increased the combustion temperature. Furthermore, lower N2 pressures enhanced the formation of AlN nanofibers due to the accelerated gasification of Al. The optimum values of the particle size of Al and the N2 pressure for the formation of high-purity AlN nanofibers were found to be 3 µm and 0.10 MPa, respectively.