Effects of NH₃ flow rate on the thermal plasma synthesis of AlN nanoparticles

Abstract

Aluminium nitride (AlN) nanoparticles were synthesized by using a non-transferred arc plasma. A pellet of micro-sized aluminium (Al) powders was evaporated by using an argon-nitrogen thermal plasma flame, and ammonia (NH₃) was introduced into the reactor as a reactive gas. The flow rate of NH₃ was controlled from 5 to 25 L/min at a fixed input power of 10.2 kW. In experiments, unreacted Al powder was found at low NH₃ flow rates at 5 and 10 L/min. The size and the crystallinity of the synthesized AlN particles increased with increasing flow rate of NH₃ until 20 L/min. The maximum particle size of AlN nanoparticle was about 100 nm at a 20 L/min NH₃ flow rate. At an excessive flow rate of NH₃ of 25 L/min, however, the size and the crystallinity of AlN were decreased. In order to analyze the experimental results for the thermal plasma synthesis of AlN nanoparticles, we carried out numerical simulations on the thermal plasma. The vortex flow of the thermal plasma near the Al pellet was gradually enhanced with increasing NH₃ flow rate from 10 to 20 L/min. The strength of the vortex flow, however, was decreased at the highest NH₃ flow rate of 25 L/min.