Microstructure evolution during spark plasma sintering of FJS‐1 lunar soil simulant

Abstract

AbstractA spark plasma sintering (SPS) process has been explored to densify FJS‐lunar soil simulants for structural applications in space explorations. The effect of SPS conditions, such as temperature and pressure, on the densification behavior, phase transformation, microstructural evolution, and mechanical properties of FJS‐1 have been examined by conducting the X‐ray diffraction analysis, electron microscopy imaging, and nano/micro indentation testing. Test analysis results were also compared to results from the FJS‐1 powder and sintered samples without pressure. The FJS‐1 powder was composed of sodian anorthite, augite, pigeonite, and iron titanium oxide. When FJS‐lunar soil simulants were sintered without pressure, the main phase evolved from sodian anorthite to the intermediate sodian anorthite, jadeite and glass, and iron titanium oxide at 1000°C, which were further transformed into filiform and feather‐shaped augite and schorlomite at 1100°C. Most densification processes in pressureless sintering occurred at 1050°C‐1100°C. During the SPS process, the main phases were sodian anorthite, pigeonite, and iron titanium oxide at 900°C. These phases were transformed to sodian anorthite, glass, and feather‐shaped augite at 1000°C and 1050°C, with the nucleation of dendritic schorlomite at 1050°C. Significant densification by SPS can be observed as low as 900°C, which indicates that the application of pressure can substantially lower the sintering temperature. The SPSed samples showed higher Vickers microhardness than the pressureless sintered samples. The mechanical properties of the local phases were represented by the contour maps of elastic modulus and nanohardness. Multiscale mechanical test results along with the microstructural characteristics further imply that the SPS can be considered a promising in‐situ resource utilization (ISRU) method to densify lunar soils.