SEM-EDS analysis of glass fibers corroded in physiological solutions by dynamic tests with variable flow rates

The dissolution of mineral fibers has been studied in simulated physiological fluids using a dynamic testing procedure. Fibers of different chemical composition and obtained by different processes with a mean diameter of about 1 micron, have been characterized with respect to their solubility under various test conditions of flow-rate. The surfaces were analyzed using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction techniques. SEM examinations show the formation of various corrosion patterns: porous, gel-like outer layers; precipitation zones and even, in some cases, no modification of the surface aspect. EDS analyses performed on the fibers, on the fiber surface layers, or on the deposits show three types of chemical composition: areas enriched in Al, in Ca and P, or in Al, Ca, and P. These surface compositions can be found for the same type of fiber tested, depending on the flow rate of the solution. Surface changes depend strongly on the initial composition of the glass and on the test conditions, particularly the flow rate. It is of particular interest to characterize the remaining surfaces (if any) obtained at the end of the in vitro test run and to compare them with surface analysis of the recovered fibers from the in vivo tests to assess the validity of the in vitro tests.