Highly Crystalline AlN Particles Synthesised by SHS Method

Aluminium nitride (AlN) powders were prepared by self-propagating high-temperature synthesis (SHS). Aluminium and AlN powder mixtures with weight ratios of about 60/40, in the presence of 3wt% NH4F and 3wt% carbon powders were ignited in a nitrogen atmosphere of 8 MPa, resulting in highly crystalline AlN particles with regular hexagonal morphology. The microstructure development during the reaction and the influence of additives of NH4F and carbon were determined by SEM/EDS and XRD analysis of the resulting products. For the samples with NH4F and carbon, the combustion temperature could be kept on a high level for longer times compared to the sample without NH4F and carbon. This indicates that an after-burning phenomenon has occurred; Carbon apparently enhances vapour transport through a mechanism that involves reduction and then removal of the surface oxide layer of the particles during afterburning.