Glass-ceramic article and method
Abstract
Abstract THIS INVENTION RELATES TO THE STRENGTHENING OF GLASSCERAMIC ARTICLES IN WHICH THE CRYSTAL CONTENT THEREOF COMPRISES THE PREDOMINANT PART OF THE ARTICLES AND CONTAINING NEPHELINE AS THE PRINCIPAL CRYSTAL PHASE. THE STRENGTHENING IS EFFECTED THROUGH THE CONVERSION OF AT LEAST PART OF THE NEPHELINE CRYSTALS IN A SURFACE LAYER OF THE ARTICLE TO LOW EXPANSION LITHIUM ALUMINO-SILICATE-TYPE CRYSTALS SUCH AS BETA-EUCRYPTITE AND BETA-SPODUMENE SOLID SOLUTION TYPE CRYSTALS, THE CONVERSION CAUSING THE SURFACE LAYER TO HAVE A LOWER COEFFICIENT OF THERMAL EXPANSION THAN THE INTERIOR PORTION OF THE ARTICLE AND THEREBY CREATING AN INTEGRAL SURFACE COMPRESSION LAYER IN THE ARTICLE. THE TRANSFORMATION OF NEPHELINE CRYSTALS TO THE BETA-EUCRYPTITE TYPE CRYSTALS IS ACCOMPLISHED THROUGH AN ION EXCHANGE REACTION TAKING PLACE WITHIN A SURFACE LAYER OF THE ARTICLE WHEREIN LITHIUM IONS FROM AN EXTERNAL SOURCE ARE EXCHANGE FOR SODIUM IONS IN THE NEPHLINE, THIS EXCHANGE ITSELF BEING UNDERTAKEN AT A HIGH TEMPERATURE OR THIS EXCHANGE BEING UNDERTAKEN AT A LOW TEMPERATURE AND BEING FOLLOWED BY A HIGH TEMPERATURE HEAT TREATMENT.
Inventors
- 👤 Bruce R Karstetter
Bibliographic Details
Claims Analysis
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1974-03-29 | 1974-09-28 | 1975-03-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-29 | 1978-09-28 | 1979-03-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-29 | 1982-09-28 | 1983-03-30 | $7700.00 | Window Closed / Lapsed |