Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – Process of manufacturing optical fibers – waveguides – or...
Reexamination Certificate
2000-10-11
2003-10-21
Colaianni, Michael (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
Process of manufacturing optical fibers, waveguides, or...
C065S347000, C065SDIG001, C065SDIG001, C501S040000
Reexamination Certificate
active
06634189
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of making chalcogenide glasses. More particularly, the invention relates to a method of making selenium based chalcogenide glasses utilizing liquid encapsulation.
2. Description of the Related Art
Chalcogenide glasses consists of one or more of the elements sulfur (S), selenium (Se), or tellurium (Te). Chalcohalides are glasses containing one or more of the elements S, Se and Te, and one or more halides anions (F, Cl, Br and I). Chalco-oxides are glasses containing one or more of the elements S, Se and Te and oxygen. Chalcogenide glasses are of interest because of their ability to transmit infrared radiation. Selenium based chalcogenide glasses (for example, As
2
Se
3
and Ge
28
Sb
2
Se
60
) are of particular interest due to their chemical durability, moderate glass transition temperatures, and ability to transmit infrared radiation both in the 3-5 &mgr;m and 8-12 &mgr;m regions.
Chalcogenide glasses have been made by a number of techniques. U.S. Pat. Nos. 3,338,728, 3,343,972, and 3,360,649 disclose the production of chalcogenide glasses in sealed ampoules similar to that discussed below in relation to the commercial chalcogenide glass known as TI-1 173. U.S. Pat. No. 3,360,649 relates specifically to a selenium-germanium-antimony chalcogenide glass.
U.S. Pat. No. 4,484,945 discloses a process which involves subjecting a mixture of chalcogenide oxides contained in solution to a simultaneous coreduction reaction. The coreduction reaction is achieved by adding reducing agents to the oxide solution such as hydrazine, sulphur dioxide, thioureas, etc.
U.S. Pat. No. 4,492,763 discloses germanium-free chalcogenide glasses prepared utilizing sealed ampoules.
High purity oxide glasses may be prepared by melting the oxides together in an open crucible. For selenium based chalcogenide glasses, high purity metal selenides are generally not commercially available, therefore, selenium metal is melted and reacted to form chalcogenide glass. Selenium melts at 216° C. and its vapor pressure reaches I atmosphere at 685° C. while the melting points of most other chalcogenide glass components are greater than 700° C. Therefore, reaction in an open crucible will result in the almost complete evaporation loss of selenium.
One selenium based chalcogenide glass was formerly made by Texas Instruments, now Raytheon Company, and is known as TI-1 173. TI-1 173 is a ternary glass composition made according to the formula Ge
28
Sb
12
Se
60
. To prevent the evaporation loss of selenium during the making of TI-1173, the reaction is conducted in a sealed quartz ampoule. The starting materials including selenium metal are placed in a quartz tube and the tube is sealed while under a vacuum. The tube is slowly heated and mixing of the molten metals occurs by rocking and/or rolling the tube during heating. The tube is then quenched to form the chalcogenide glass. The quartz tube is sacrificed to remove the reacted glass. While this method allows for commercial production of TI-1173, there are a number of shortcomings with this method, including: (1) during sealing of the quartz tube, oxygen, an impurity, may be introduced, degrading IR transmission; (2) there is a risk of explosion of the sealed quartz tube during heating if the ampoule is not designed and/or heated properly to prevent sublimation of the selenium melt; (3) the rock and/or roll mixing is not sufficient to produce optical quality glass; the reacted glass must be re-melted, stirred, re-cast and annealed to produce optical quality glass; (4) the quartz ampoule is not reusable, (5) temperatures in excess of 900° C. must be reached to completely melt the germanium; and (6) glass batch size is limited by the size of commercially available quartz tubing, and by the margin of safety required to reduce the risk of explosion.
SUMMARY OF THE INVENTION
Accordingly, a need has arisen for making chalcogenide glass, and particularly selenium based chalcogenide glass, in a safer and more economical fashion.
In accordance with the present invention, a method of producing chalcogenide glass is provided that significantly improves the safety and economy of making the glass. The method includes the steps of: (1) placing about stoichiometric amounts of glass components into a reactor, (2) substantially covering the glass components in the reactor with an encapsulent to prevent the evaporation loss of low boiling point or high vapor pressure glass components, and (3) heating the glass components to a temperature below the boiling points of the components, and (4) actively mixing the components to cause the liquid glass components to react with the solid glass components to form molten chalcogenide glass.
Accordingly, an object of the present invention is to provide an improved method for producing selenium based chalcogenide glasses which is safer and more economical than known methods.
REFERENCES:
patent: 3291585 (1966-12-01), Okamura
patent: 3338728 (1967-08-01), Hilton, Jr. et al.
patent: 3343972 (1967-09-01), Hilton, Jr. et al.
patent: 3360649 (1967-12-01), Brau et al.
patent: 3628932 (1971-12-01), Inoue
patent: 4484945 (1984-11-01), Badesha et al.
patent: 4492763 (1985-01-01), Trotta et al.
patent: 4542108 (1985-09-01), Susman et al.
patent: 5385593 (1995-01-01), Longobardo
patent: 296 427 (1991-12-01), None
patent: 0 564 190 (1993-10-01), None
Autery William David
Hudgens James Jay
Trombetta John Michael
Tyber Gregory Stewart
Baker & Botts L.L.P.
Colaianni Michael
Raytheon Company
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