Enhanced properties by spark plasma sintering of additive-free Martian soil simulants for ISRU applications

The availability of efficient manufacturing techniques to produce highly resistant structural components from Mars regolith represents a key target for accelerating future colonization of this planet. In this regard, the fabrication and mechanical characterization of nearly full dense samples is investigated in this work using additive-free JSC-Mars-1A, MMS, MGS-1, and JEZ-1 regolith simulants. These systems, which have been developed to reliably mimic compositional and structural characteristics of different soils actually present on the red planet, show a diverse consolidation behavior when processed by Spark Plasma Sintering (SPS) under vacuum. Fully dense and rather homogeneous samples are produced at 1000°C from JSC-Mars-1A, originally containing a dominant amorphous fraction, which acts as a sintering aid. Superior mechanical performances, with respect to the other simulants, are displayed by the corresponding bulk material with compressive strength, flexural strength, and hardness values equal to about 310 MPa, 70 MPa, and 1000 HV, respectively. The properties of samples originated from MMS, MGS-1, and JEZ-1, mostly consisting of crystalline phases (> 90 wt.%), are negatively affected by porosity remaining after SPS (up to 5 vol.%), even if higher temperatures are used (1050-1100°C). Nonetheless, hardness, compressive and flexural strengths in the latter materials are still generally better than values reported in literature. It is then apparent that SPS technology represents a powerful tool for producing resistant building components from Mars soil, with no need of sintering aids.