Aluminum particle production on alumina rod surface by continuous-wave laser ablation

Abstract

Continuous-wave laser ablation has been applied to alumina reduction with the eventual goal of lunar resource utilization. Aluminum particles were detected on the alumina rod surface after laser ablation. Impurity precipitation has been proposed as the aluminum particle production mechanism. For this study, distributions of aluminum particles and temperatures after laser ablation on an alumina rod surface were measured using SEM and two-color method. Laser power affected the aluminum particle distribution. The mean aluminum particle radius varied: 0.11–1.7 μm. The minimum value was consistent with the critical radius for aluminum nucleation in heterogeneous nucleation. The time history of surface temperatures was found to be independent of laser power. Therefore, aluminum particle production is expected to change with oxygen deficiency, and to increase with laser power. The obtained condition for aluminum particle production is applicable for an aluminum collection system in the alumina reduction method using laser ablation: the plate temperature of T = 933–2300 K and the cooling rate of 600–800 K/s.