X-Ray Diffraction Study on Crystalline and Osmotic Swelling of a Layered Titanate

The swelling of a layered protonic titanate H(0.7)Ti(1.825)square(0.175)O(4)center dot H(2)O(square : vacancy) upon contact with the system of tetrabutylammonium (TBA) ion and H(2)O has been studied by X-ray diffraction. The TBA- intercalated titanate revealed three distinct gallery heights of 1.47, 1.75 and 2.1 nm, depending on water vapor pressure and drying temperature. These are attributable to crystalline swelling, i.e., zero-, mono- and bi-layer hydrates. A much higher degree of hydration was discerned by a series of sharp diffraction lines for a colloidal aggregate centrihged from an aqueous suspension of the titanate and TBA ion. The basal spacing expanded steadily from 4 to > 20 nm with decrease of the TBA concentration. Along this osmotic swelling process, amorphouslike halo was evolved, which suggests exfoliation into single sheets.