Small-Angle X-Ray Scattering by Metastable Liquid Immiscibility in Glass

Abstract

AbstractSmall-angle X-ray scattering measurements were made on samples of CaO—MgO—SiO2 as CaO-MgO-SiO2 glass in which met astable amorphous phase separation had been induced by heat treatment. Glass rods drawn from a melt of composition 30.5% CaO, 8.0% MgO, 61.5% SiO2 (by weight) at 1400°C were heat treated for 1, 2, 10, and 15hr at 825°C. X-ray scattering intensities of heat-treated and non-heat-treated samples were measured using an apparatus based on Kratky collimation geometry and equipped with a pulse height analyzer. Particle sizes were calculated from the radii of gyration which were determined from plots of log intensity vs, θ2, according to the method of Guinier. The data show a growth with time of the dispersed spheres from 350 to 1880 Å in diameter and correspond to the growth rate for diffusion-controlled growth of a sphere. Electron micrographs of identical samples prepared concurrently are presented. Inhomogeneity sizes obtained by the two methods are in very good agreement. Results obtained using the Kratky system in conjunction with a pulse height analyzer are compared with those obtained when a slit collimation system and balanced filter monochronmtization were used to study the same sample.