ELASTICITY AND ELECTRICAL-PROPERTIES OF POROUS BODIES DESCRIBED AS AN AGGLOMERATE-OF-SPHERES

The phenomenological characterization of a sintered, pressed or electrolytically produced porous body as an 'agglomerate-of-spheres' (AOS), estimated by the properties of their connections - the so-called necks -, was used to predict its break-force, elasticity and resistance. To this, the previous theoretical description of the AOS could be expanded by the definition of an ideal AOS. Furthermore, it could be shown, that the behaviour of the AOS is re-inforced by the relation of the radii of the sphere and neck. The description of the mechanical properties correlates well in the case of elasticity and break-tension with data of experiments at the University of Kassel with PbO2-electrodes. The theoretically predicted values of the electrical properties are about a hundred times smaller than the experimental ones. This may be caused by the material-specific circuit capacity used for the PbO2, since there are no data concerning the stoichiometric variance of the oxygen phase width in the neck region. An attempt to approach to real electrodes is only a trial, which, for the first time, takes experimental data into consideration. The lack of dependable material-specific sizes of lead dioxide is still the greatest inaccuracy in comparison with experimental data.