Electron microscopic observation of montmorillonite swelled by water with the aid of hydrophilic ionic liquid

• Observation of two different conditions of hydrated montmorillonite was investigated.
• The swelling structure by water molecules was characterized by TEM.
• The observation mechanism of hydrous montmorillonite was revealed.
• Ionic liquid is useful for characterization of hydrated materials with layer structure.

The morphology and structure of hydrous montmorillonite in different swelling condition have been observed with the aid of hydrophilic ionic liquid (IL; 1-Butyl-3-methylimidazolium Tetrafluoroborate) using electron microscope. The observation mechanism of hydrous montmorillonite with layer structure using IL was revealed by swelling behavior as measured by X-ray diffraction (XRD) and transmission electron microscopy (TEM) with selected area electron diffraction pattern (SAED). The morphology of hydrous montmorillonite containing a large amount of water was also successfully observed by field emission electron microscope (FE-SEM). In addition, the inductively coupled plasma (ICP) and thermogravimetric – differential thermal analysis (TG-DTA) results showed the ion-exchange behavior of hydrous montmorillonite during the IL treatment. The technique allowed the exact morphology to be observed of hydrated materials with layer structure in civil engineering, cosmetics, medical and agricultural fields.