Evaluation of ablation plume temperature for laser intensity and alumina powder particle density in alumina reduction

Abstract

We considered the application of lunar regolith for the construction of a lunar base. To obtain aluminum as building materials, alumina powder reduction was performed using 1-kW-class continuous-wave diode laser ablation. The possibility of reduction, and the temperature dependences of the ablation plume on the laser intensity, ambient pressure, and particle density were investigated, and surface analysis was conducted using SEM and XPS. The laser intensity, ambient pressure, and particle density were set as 0.32–1.3 GW m−2, 10–100 kPa, and 16%–56%, respectively. Alumina reduction was verified by observing the 394- and 396 nm spectra of Al(I). The plume temperature increased with laser intensity in the range of 2700–4500 K. We achieved temperatures of 5200 K and 1000 K higher than with the CO2 laser by powder compression. Spheres that appeared to be aluminum were observed on the irradiated surfaces. However, this could not be proved because of the aluminum oxide layer.