Investigation of cation-exchanged montmorillonites by combined x-ray diffraction and positron annihilation lifetime spectroscopy

A characterization of some mineral and organophilic montmorillonites has been carried out using x-ray diffraction and positron annihilation lifetime spectroscopy. The combination of the two techniques supplies information on the microscopic structure of clays, in particular on the fraction of interlayer gap which is occupied by water molecules in the mineral clays. Nanocavities among cations of quaternary ammonium salts inserted in the organophilic clays were also investigated and compared with those existing in the free salt. (C) 2002 American Institute of Physics.