Strengthening of Glass by an Electroionic Technique

An electroionic strengthening process for glass which produces a relatively deep surface compressive layer to preserve this strength has been examined. The process consists of using an electric field to drive large alkali ions from a molten salt bath into the glass to replace the small resident alka...

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Bibliographic Details
Main Authors: Kubose,Donald A, Perry,Henry A, Tydings,John E
Format: Report
Language:English
Subjects:
ALUMINOSILICATE GLASS
Ceramics, Refractories and Glass
CRACKS
FUSED SALTS
GLASS
HEMISPHERICAL SHELLS
IMPREGNATION
ION EXCHANGE
ION IMPLANTATION
IONS
MECHANICAL PROPERTIES
Physical Chemistry
POTASSIUM
SOLUTIONS(MIXTURES)
SPHERES
SURFACES
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Summary:An electroionic strengthening process for glass which produces a relatively deep surface compressive layer to preserve this strength has been examined. The process consists of using an electric field to drive large alkali ions from a molten salt bath into the glass to replace the small resident alkali ions. This exchange of ions, carried out at temperatures below the strain point of the glass, produces a compression stress on the glass surface and hence strengthens the glass. Alkali-aluminosilicate glass hemispheres (7.6 an OD, 0.4 cm. thick) and cylinders (4.7 cm diameter, 4.4 cm long) were strengthened using postassium ions from a molten potassium nitrate bath. Maximum compressive stresses on the order of 1,000,000 psi and treatment depths of 0.65 mm were obtained for the cylindrical specimens. Although high strengths were also obtained for the hemispherical specimens there was a large variation in the measured strengths in addition to a very high incidence of specimen there was a large variation in the measured strengths in addition to a very high incidence of specimen breakage during treatment. Oxygen and hydroxyl ion attack accelerated the growth of cracks. (Author Modified Abstract)