Carbo-thermal reduction of lunar highland regolith simulant for in-situ manufacturing of SiC

In-situ resource utilization is important to ensure sustainability of exploration missions such as establishing a habitable extra-terrestrial base on the moon. Resources available on the lunar surface such as the regolith must be tapped to build structures and manufacture products on moon. This requires raw materials like metals, metal alloys and ceramics to be extracted from the regolith. Regolith contains silicon as an abundant element next to oxygen, and hence synthesis of silicon and its compounds seems pragmatic. Therefore, the objective of this study is to extract silicon carbide (SiC) from lunar regolith which has a wide range of applications in producing abrasives, electronics and ceramic components. The methodology involves heating the regolith to a high temperature so that volatile species such as Na, K, Fe, SiO are liberated and subsequently, the evolved SiO gases are reduced to SiC by using methane. This resulted in the formation of SiC whiskers which are verified by X-ray diffraction and Raman spectroscopy. Electron microscopy images reveal that the majority of the SiC whiskers are formed by vapor–liquid-solid mechanisms with diameters ranging from 0.3 to 2 µm. Detailed electron diffraction and microscopy studies reveal that the whiskers formed are single crystals having a core–shell structure containing SiC and SiO_x respectively. This study provides a foundation for the direct manufacturing of SiC whiskers from lunar regolith which can be used for fabricating electronic devices, construction materials, radiation shields and habitats on the surface of moon.