モンモリロナイト表面のカチオンの原子スケール観察

抄録

The influence of the ion exchange on the atomic-scale structure of clay mineral surface has not been revealed. We conducted the observation of the montmorillonite surface by frequency modulation atomic force microscopy (FM-AFM) in order to compare the atomic-scale change of the montmorillonite surfaces before and after the cation exchange. The sodium ions of natural montmorillonite were exchanged by ammonium and alminium ions before experiment. The montmorillonite surfaces after the cation exchange showed the hexagonal pattern corresponding with the natural montmorillonite. No lattice vacancy was observed, whereas the vacancies should be formed after the cation exchange. It suggests that the lattice vacancies were filled with the water molecules. Our method will lead to in situ observation of the replacement of the ions. We believe that the atomic-scale observation will provide the deeper understanding of the ion exchange property of clay minerals.