摘要 |
<p>This invention is directed to the production of unitary, transparent glass articles demonstrating exceptionally high flexural and impact strengths composed of an interior portion and an integral surface compression layer. The articles are prepared by contacting glass bodies consisting essentially, in mole percent, of 14-24% R20, wherein R20 consists of 0-5% Li20, 0-5% K20, and the remainder Na<Sub>2</Sub>0, 17-21% Al<Sub>2</Sub>O<Sub>3</Sub>, 45-60% SiO<Sub>2</Sub>, 3-6% TiO<Sub>2</Sub> and/or ZrO<Sub>2</Sub>, and 0-2% P<Sub>2</Sub>O<Sub>5</Sub>, the sum of those components constituting at least 85% of the total composition, at a temperature above the annealing point of the glass with a source of Li<Sup>+</Sup> ions to replace at least part of the Na<Sup>+</Sup> ions and, if present, K<Sup>+</Sup> ions in a surface layer with a corresponding amount of Li<Sup>+</Sup> ions and to react the Li<Sup>+</Sup> ions with Al<Sub>2</Sub>O<Sub>3</Sub>, and Si0<Sub>2</Sub> in the surface layer to form crystallites of beta-quartz solid solution nucleated by the Ti02 and/or ZrO<Sub>2</Sub>.</p> |