The electrothermal gun is a relatively new technology that produces various types of plasma vapor using high current pulsed power. A dense metal vapor plasma at extremely high temperature and high velocity is discharged from the electrothermal gun, and introduced into the background gas in the reaction chamber. Then, the discharged metal plasma vapor reacts with background gas and produces nanoscale ceramic particles. Although this method can be applied to make a variety of nanosized ceramic materials by choosing different metals for the cathode/anode/bore ablation and different gases in the reaction chamber, in this investigation, nanoscale alumina particles have been produced by letting a highly ionized aluminum plasma vapor react with oxygen gas in the reaction chamber. The synthesized alumina powder has been characterized by Xray diffraction, BET, SEM, and TEM. XRD patterns confirmed that low energy firing of 44 kJ energy deposition produced high purity γ-phase alumina nanoparticles, which sizes ranging between 5 and 50 nm with an average particle diameter of 26 nm. By contrast, a high energy shot of 96 kJ produced alumina particles of 41 nm average particle diameter and a small amount of δ- and α-phase contents were found even though γ-phase alumina was still dominant. In addition, high-speed video imaging revealed delayed turbulent mixing and reaction between aluminum plasma vapor and oxygen gas to several milliseconds after approximately 1 ms current pulse duration.

Keywords: Electrothermal gun, Metal plasma vapor, Nanoscale alumina powder.