Metallurgical performance evaluation of space-weathered Chang'E-5 lunar soil

Space metallurgy is an interdisciplinary field of planetary space science and metallurgical engineering, and it is a systematic and theoretical engineering technology for planetary in-situ resource utilization. However, without an atmosphere and magnetic field, lunar surface has experienced space weathering. The microstructure of lunar soil is different from the minerals on Earth, which limits the development of space metallurgy. In this study, SEM and TEM analyses were performed on Chang'e 5 powder lunar soil samples. The characteristics of the lunar soil's microstructure may drastically change its metallurgical performance. The main special structures of the lunar soil minerals include the nano-phase iron formed by the impact of micrometeorites; the amorphous layer by solar-wind injection; radiation tracks modified by high-energy particle rays inside mineral crystals etc. The wide distribution of nanophase iron may have a greater impact on the electromagnetic properties of the lunar soil. Hydrogen ions injected by the solar wind may promote the hydrogen reduction process. The widely distributed amorphous layer and impact glass can help the melting and diffusion process of lunar soil. Therefore, while high-energy events on the lunar surface are transforming the lunar soil, they are also increasing the chemical activity of the lunar soil. This is a property that earth samples and traditional simulated lunar soil do not possess. Carrying out space metallurgy requires comprehensive consideration of the unique physical and chemical properties of the lunar soil.