Vapour phase synthesis of aluminum nitride using a transferred arc plasma system

This work introduces a new concept for the synthesis of ultrafine aluminum nitride powder. A transferred arc plasma torch of 6.5 kW was used as a heat source to vaporize an aluminum ingot as a source of aluminum vapour for the synthesis of aluminum nitride outside the plasma chamber. The aluminum vapour produced in the plasma chamber was carried by the argon plasma gas to a tubular synthesis reactor where it reacted with ammonia injected radially. The effects of arc current, arc length and argon flow rate on the aluminum evaporation rate and the gas temperature reached in the mixing zone were studied. The results show that long arcs, high currents and high argon flow rates were best to maximize the temperature in the mixing zone and short arcs, high current and high argon flow rate were best for high evaporation rates. Experiments were performed to study the effect of arc length, nitriding agent used, ammonia jet momentum, ammonia flow rate, residence time and temperature on the conversion to aluminum nitride. Conversions up to 100% were achieved. The aluminum nitride produced had an average particle size of approximately 20 nm and specific surface area of about 90 m...