Cold sintering: A promising in situ resource utilisation strategy to densify lunar regolith simulants for construction applications

Sintering lunar regolith simulants as building materials is an effective method to establish long-term lunar bases. However, the high energy consumption of conventional thermal sintering is a challenge for energy-scarce lunars. The cold sintering process (CSP), which densifies ceramics with the assistance of transient solvent, offers a solution to overcome the aforementioned problems. Utilizing the CSP at 150 °C, 200 MPa, and 15 wt% 10 mol NaOH for 90 min, the density and compressive strength of the samples reached 2.44 g/cm³ and 207 MPa, respectively. The energy consumption of CSP equipment is only 0.86 kW·h, which is 6.66 times lower than that of conventional thermal sintering (5.73 kW·h). Furthermore, the compressive strength of the samples after three cool-heat cycles temperature between −196 °C and 150 °C was 205 MPa, indicating that the samples maintained high reliability in a simulated lunar environment. This excellent performance is attributed to the NaOH solution dissolving the oxide clusters on the particle surface, and the precipitation-generated glass phase connecting adjacent particles, making the particles consolidated and densified. Therefore, the cold sintering process presents promising prospects for the energy-efficient fabrication of lunar construction materials with excellent mechanical strength and durability.