Formation of aluminium nitride whiskers by direct nitridation

This work describes novel results on the growth of aluminium nitride (AlN) whiskers by direct nitridation of Al–NH4Cl starting mixtures. The nitridation experiments were carried out in a horizontal tube furnace at 1000 °C for 1 h in 1 l/min N2 gas flow. It is found that the growth of AlN whiskers was principally promoted by NH4Cl which provided a different reaction pathway depends on vapor-phase reactions mechanism instead of normal liquid–gas mechanism. The thermodynamic analysis of possible intermediate reactions in the operating temperatures range confirmed that the AlN whiskers could be grown through spontaneous vapor-phase chlorination–nitridation sequences. The SEM observation revealed that depending on NH4Cl concentration homogeneous AlN nanowhiskers of <150 nm in diameters can be obtained as well as composites of particles-whiskers of AlN which may be potential for preparing useful sintered AlN materials.