Surface Chemistry and Structural Effects in the Stress Corrosion of Glass and Ceramic Materials.
Final rept. Jan 82-Jan 86,
PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF MATERIALS SCIENCE AND ENGINEERING
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The fracture behavior of glasses in the system Na2O.xAl2O3.3-xSiO2 x0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 has been evaluated, and independently, their chemical corrosion in aqueous solutions was studied. The changes imposed upon the Al2O3SiO2 ratio, were intended to influence the network structure of the glass. The V-K sub I diagrams were obtained using the constant moment double cantilever beam technique in a wide variety of environments. The n-parameter in Region I was found to be independent of pH, whereas the presence of velocity plateaus and thresholds was shown to be very dependent upon the composition of the aqueous environment. This behavior was attributed to interactions between the fracture surfaces behind the crack-tip. The dependence of the n-parameter upon the bulk composition and structure of the glass was correlated with the elastic properties of the glass i.e., the value of the n-parameter did not depend directly upon the corresponding corrosion resistance of the glass. Finally, the static fatigue limit, at least in the case of the Na2O.3SiO2 x0.0 glass, could be explained in terms of crack-healing rather than crack-blunting. Although, this study of fracture within a systematic compositional series of glasses led to critical assessments of the existing models for environment-dependent crack growth in glass. The results of comparable-although less extensive-studies on fluorozirconate glasses and silica solgel materials are also reported.
- Ceramics, Refractories and Glass
- Atomic and Molecular Physics and Spectroscopy