Simulation of nanophase iron production in lunar space weathering

Nanophase iron (np-Fe0) particles produced by space weathering have been widely observed in lunar soil. Current research suggests that np-Fe0 could have important effects on the chemical, optical and magnetic properties of the lunar soil. To investigate the relationship between np-Fe0 and these properties of lunar soil, simulation of the production process of np-Fe0 by space weathering is necessary because of the scarcity of lunar samples for research purposes. New methods using microwave heating and magnetron sputtering techniques to simulate np-Fe0 production both in the glass phase and on the grain surfaces, respectively, are investigated in this study. Both the formation and occurrence of np-Fe0 are taken into account in the experiment. The X-ray Diffraction (XRD) spectra show that metallic iron has formed in the glass phase produced by microwave heating of ilmenite. Using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), the size of np-Fe0 particles produced in a microwave heating experiment, which is held for 8 min at 1300 °C, is determined to be about 100–500 nm. Compared to the glass of lunar sample 10084, the major composition of the glass matrix is formed by microwave heating compares favorably. In magnetron sputtering experiment the size of np-Fe0 particles is about 20–30 nm, and appears on the grain surfaces. The characteristics of np-Fe0 produced in the simulations are consistent with those of lunar samples documented in the literature.