Catalytic growth of aluminum nitride whiskers by a modified carbothermal reduction and nitridation method

Aluminum nitride (AlN) whiskers were synthesized by calcining an [Al(Hedta)(acetone)] (H4edta=ethylenediaminetetraacetic acid) complex, which contained a very small amount of iron as a catalyst, under flowing nitrogen in the temperature range 1200-1500 °C, and then burning out the residual carbon. At relatively low reaction temperatures (around 1200 °C), most AlN whiskers were bead-shaped and chain-like, whereas at higher reaction temperatures the whiskers were acicular and six-sided prismatic. An iron droplet was observed on the tip of AlN whiskers, strongly supporting that the whiskers grow through the vapor-liquid-solid (VLS) mechanism. We suggest that whether or not the diameter of the whisker is uniform along its length depends on relative rates between diffusion of AlN vapor into an iron droplet and growth of the whisker.