Synthesis of Aluminum Nitride Nanopowder with Particle Size Less than 10 nm by Pulsed Wire Discharge in Nitrogen Gas

Abstract

High purity aluminum nitride (AlN) nanopowders were synthesized by pulsed wire discharge (PWD) using aluminum wires in nitrogen gas rather than ammonia gas, which is harmful but traditionally considered mandatory for this reaction. The synthesis was carried out at various relative energies (K) of 24–289, where K was the ratio of the charged energy of the capacitor to the vaporization energy in the wire, and at nitrogen gas pressures (P) of 10–100 kPa. From the measurement of voltage and the current waveforms during PWD, it was determined that the deposited energy in the arc discharge (Ea) after wire heating increased with increasing K. Analysis of prepared nanopowders showed that an increase in AlN content (CAlN) and a decrease in median particle diameter (D50) resulted from an increase in K and/or Ea. The highest CAlN of 97 wt % with a D50 of 6 nm was obtained at K = 289 and P = 10 kPa. The arc discharge after wire heating was considered to generate active species from the nitrogen gas with higher decomposition energies than those observed with ammonia and to drive the nitriding process during PWD.