Residual stress profiles in silica glass were measured after water diffusion treatment under 47.33 kPa (355 Torr) water vapor at 350°C and 650°C. Earlier, it was found that water solubility in silica glass exhibited peculiar time dependence: Solubility increased with time exceeding the normal water solubility expected from higher temperatures. Then, the water solubility decreased with time. It was hypothesized that the stress induced by water diffusion and its subsequent relaxation is responsible for the phenomenon. Residual surface stress generation in silica glass was found to correlate closely with surface hydroxyl concentration, systematically increasing until eventual surface stress relaxation results in stress decrease for treatments beyond 265 hours at 650°C. This observation validates previous theories of time dependent diffusivity in silica glass.
Some polymers and oxide glasses exhibit unusual diffusion of liquid or gas, with the depth of diffusion exhibiting a linear increase with time, instead of normal square root of time dependence. There have been many models, but very few experimental data that can help clarify the cause of the phenomenon's existence in glass. Residual stress in sodium trisilicate glass (Na2O–3SiO2) samples was characterized following Case II water diffusion at 80°C in a saturated water vapor environment. The surface‐swelled layer of the glass was removed by dissolving it in water, and birefringence of the newly revealed surface layer was measured. The presence of a constant negative tensile stress gradient was revealed by indicating that Case II diffusion in sodium trisilicate glass originates from this stress gradient, which overwhelms the more typical Fick's law concentration‐dependent flux.
more » « less- Award ID(s):
- 1713670
- NSF-PAR ID:
- 10401180
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- International Journal of Applied Glass Science
- Volume:
- 14
- Issue:
- 2
- ISSN:
- 2041-1286
- Page Range / eLocation ID:
- p. 330-337
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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