Ammonia-treated phosphate glasses useful for sealing to metals m

Details Ammonia-treated phosphate glasses useful for sealing to metals m Ammonia-treated phosphate glasses useful for sealing to metals m

1990-04-30

1991-09-03

Bell, Mark L.

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

501 45, 105 301, 105 321, C03C 317

Patent

active

050455087

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.

REFERENCES:
patent: 4202700 (1980-05-01), Wilder, Jr.
patent: 4455384 (1984-06-01), Day et al.
Marchand, "Nitrogen-Containing Phosphate Glasses", Journal of Non-Crystalline Solids; vol. 56, 1983 pp. 173-178.
M. Rajaram et al., "Nitrogen Dissolution In Sodium Alkaline-Earth Metaphosphate Melts"; Journal of the American Ceramic Society, vol. 70, No. 4; Apr. 1987, pp. 203-207.
Reidmeyer et al., "Preparation of Phosphorus Oxynitride Glasses", Journal of Non-Crystalline Solids, vol. 85; 1986, pp. 186-203.

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