Use of dielectric relaxation for measurements of surface energy variations during adsorption of water on mordenite

International audienceThis paper tries to assess simply and quantitatively the link between classical adsorption theories and dielectric spectroscopy, in order to demonstrate that dielectric spectroscopy can be used as a tool of determination of surface energy variations due to movements of charge carriers at the surface of solids. A simple theory is developed to analyze hops of cations at the surface of mordenite, which are detected by complex impedance spectroscopy during adsorption of water. An energy of extraction of the cation can be determined from measurements and its dependence on the quantity of water molecules adsorbed is shown and qualitatively and quantitatively explained, using relationships developed in order to interpret adsorption phenomena generally. The agreement with other determinations of the adsorption energies and solid surface energy is correct

Aluminosilicate surface energy and its evolution upon adsorption from dielectric relaxation spectroscopy

International audienceWe show that some relevant parameters characterizing the surface thermodynamics of aluminosilicates can be obtained by using dielectric relaxation spectroscopy (DRS). The central assumption is that adsorption at the aluminosilicate surface is mainly related to the presence of extra-framework cations and, as a consequence, the activation barrier for cation displacement, measured from DRS, identifies the surface energy landscape. The modification induced by molecules adsorbed in the cation vicinity is therefore detectable via the evolution of the activation barrier. The methodology is applied to a typical test case: adsorption of water in two Na+-Mordenites characterized by two different Si/Al ratios

Cinescintigraphie renale quantitative a l'hippuran I. Aspects methodologiques, trousse de marquage de l'hippuran

SIGLEAvailable from CEN Saclay, Service de Documentation, 91191 Gif-sur-Yvette Cedex (France) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc