Accession Number : AD0704910

Title :   TOPOLOGICAL MODEL FOR VISCOUS RELAXATION IN CRITICAL OXIDE MIXTURES.

Descriptive Note : Technical rept. Aug 69-Apr 70,

Corporate Author : CATHOLIC UNIV OF AMERICA WASHINGTON D C VITREOUS STATE LAB

Personal Author(s) : Simmons,Joseph H. ; Macedo,Pedro B.

Report Date : APR 1970

Pagination or Media Count : 33

Abstract : A topological model is formulated to analyze results from supercritical viscosity and ultrasonic relaxation measurements in molten oxide glasses. The model assumes that a distribution of relaxation times can be related to a distribution of environments and shows that the change in width of the distribution of relaxation times directly depends upon changes in the local composition. These changes in local composition are formulated in terms of the temperature dependent mean square compositioon fluctuation which appears above the liquid-liquid critical point. A final equation is then obtained which describes the change in the width of the relaxation time spectrum in terms of a parameter defined as the ratio of the range of structural forces to the supercritical correlation length. The final equation is compared to the results from ultrasonic spectroscopy, and is qualitatively extended to non-critical oxide systems. (Author)

Descriptors :   (*OXIDES, GLASS), (*GLASS, RHEOLOGY), RELAXATION TIME, ULTRASONIC RADIATION, VISCOSITY, PHASE STUDIES, FREE ENERGY, MATHEMATICAL ANALYSIS

Subject Categories : Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE