In-situ resource utilization: ferrosilicon and SiC production from BP-1 lunar regolith simulant via carbothermal reduction

Abstract

A study of carbothermal reductive smelting of the BP-1 lunar simulant, aiming to the in-situ production of ferrosilicon and silicon carbide is reported in the present study. BP-1 simulates a low Ti-content mare regolith and is mined in Arizona. The process was first studied from a thermodynamic point of view, while the final ferrosilicon product was examined metallographically. Reduction experiments were performed, after the enrichment of the simulant in iron oxide through dry magnetic separation, under vacuum. Thermodynamic analysis indicates that the production of a ferrosilicon alloy in smelted form and SiC is possible over 1200 °C. The use of carbon amounts in excess does not have significant effects on the progress of the reduction reaction at 1300 °C. The experimental results showed that reduction at gentle temperature conditions (1300 °C) advances the formation of a granulated ferrosilicon alloy potentially appropriate as a feed for 3D printing. X-ray diffractometry and scanning electron microscopy showed that the synthesized ferrosilicon alloy is a homogeneous metallographic structure but having a high silicon content (average concentration 23.78% by weight) and minor contents of aluminum and titanium (1.80% and 0.94% by weight, respectively). This resulting alloy could be used in various basic lunar building structures such as dwellings and research facilities, as well as to produce the machinery required for mining the ore. The second by-product of the reaction, silicon carbide, can be used as a filler in polypropylene resin/SiC composite that has been proposed as a suitable material for shielding space radiation.