A novel gasification exfoliation method of the preparation of anhydrous montmorillonite nanosheets for inhibiting restack problem suffering from dehydration

Abstract

The exfoliation of montmorillonite (Mt) into nanosheets with mono or few-layer is significant for controllable preparation of Mt. functional nanocomposites, whereas Mt. nanosheets (MtNS) prepared in aqueous solutions usually encountered restack problems suffering from dehydration. In this work, anhydrous MtNS with few layers were successfully prepared through a novel gasification exfoliation method. The quality of morphology, structural and stability characteristics of MtNS were investigated by an atomic force microscope, scanning electron microscope, BET and turbidity. The anhydrous MtNS with a thickness of 0–5 nm were prepared by the liquid nitrogen (LN2) gasification exfoliation. In addition, MtNS prepared through gasification exfoliation presented a looser interlayer structure, higher BET specific surface area and better dispersion stability than those prepared by ultrasonic exfoliation and freeze drying. Thus, the gasification exfoliation perfectly addressed the obstacle of nanosheet restacking. Moreover, molecular dynamics simulation found the LN2 could enter the interlayer domain of Mt. When heating under 70 °C, the drastic gasification of LN2 destroyed the weak interlayer binding force of Mt., leading to the successful preparation of anhydrous few-layered MtNS. These findings are expected to provide theoretical guidance for the scalable application of MtNS as functional materials.