Study on Microscopic Mechanism for Thermal Release Behavior of Helium-3 in Lunar Regolith

The problem that the retarding effect of the disordered surface layer on helium-3 cross-interface migration is difficult to characterize in an open system where He-3-bearing ilmenite in lunar regolith is directly exposed to vacuum. In this paper, a nested model consisting of a crystalline ilmenite core and an amorphous TiO₂ coating was constructed, and molecular dynamics simulations were performed over 300–2300 K to examine the cross-layer migration and diffusion of helium-3. Within a fixed 1 ns observation window, the cumulative outward-migration fraction increased markedly with temperature and reached 8.92% at 2300 K; the effective diffusion coefficient of helium-3 in amorphous TiO₂ also exhibited a thermally activated increase. Because no vacuum free surface was explicitly included, the reported cumulative fraction represents atomic-scale migration across the coating rather than engineering-scale extraction efficiency. The results indicate that the dense disordered amorphous TiO₂ layer increases diffusion resistance and, together with the absence of an external escape driving force, suppresses helium-3 migration. hese findings provide a microscopic basis for the subsequent construction of multiscale release models incorporating vacuum boundaries and for the screening of heat treatment conditions.