Ammonia-treated phosphate glasses useful for sealing to metals metals
US5045508A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 30, 1990 |
| Grant date | Sep 3, 1991 |
| Priority date | — |
| Expiry date | Apr 30, 2010 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC03C21/007
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A method of improving surface-dependent properties of phosphate glass such as durability and wear resistance without significantly affecting its thermal expansion coefficient is provided which comprises annealing the glass in a dry ammonia atmosphere at temperatures approximating the transition temperature of the glass. The ammonia annealing treatment of the present invention is carried out for a time sufficient to allow incorporation of a thin layer of nitrogen into the surface of the phosphate glass, and the treatment improves the durability of the glass without the reduction in the thermal expansion coefficient that has restricted the effectiveness of prior ammonia treatments. The improved phosphate glass resulting from this method is superior in wear resistance, yet maintains suitable thermal expansion properties so that it may be used effectively in a variety of applications requiring hermetic glass-metal seals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.