Characterization of volatiles evolved during vacuum sintering of lunar regolith simulants

This work describes an experimental vacuum setup, designed for sintering of lunar regolith simulant materials, and its application to real-time characterization and identification of volatile species, resulting from in vacuo decomposition of the non-lunar components in the materials. We carried out a thorough system characterization, highlighted critical performance aspects with respect to regolith sintering, identified the sample environment, and postulated the need for high-vacuum capabilities in light of the high gas loads, generated by the simulants. We detailed the process of identification of specific gas species (H2O, NO, H2S, CO2, SO2, SO3, HCl, HF, etc.) using mass spectrometry, and advanced their use as markers for thermally-activated processes, such as dehydration of hydrides, decomposition of major non-lunar phases (carbonates and sulfates) and lesser-represented components (nitrates, nitrides, fluorides, chlorites, etc.). Quantification of individual decomposing phases is feasible within reason despite the inherent limitations of mass spectrometry. The methods, detailed in this paper, are intended for direct comparison of lunar regolith simulants with respect to sintering applications.