Mechanisms of 2 μm picosecond laser-induced non-equilibrium structural reconstruction and performance response in Ca-based montmorillonite

Abstract

This study systematically investigates the thermal response and structural evolution of Ca-based montmorillonite under 2μm picosecond laser irradiation by integrating finite element simulations, microscopic molecular motion analysis, and experimental characterizations. The results indicate that increasing laser energy density significantly raises the transient surface temperature and thermal stress, and also alters the lattice stability temperature. Simulations reveal that while the primary layered framework of montmorillonite remains largely intact, interlayer water is progressively desorbed and the local coordination environment of Ca²⁺ undergoes rearrangement, leading to interlayer contraction. SEM and XRD analyses further confirm that laser treatment induces notable surface roughening and loosening, accompanied by a shift of the d001 peak toward higher diffraction angles, indicating reduced interlayer spacing. These findings demonstrate that 2μm picosecond laser irradiation enables effective microstructural regulation of montmorillonite without compromising the stability of its main layered framework.