US 5,779,757 A · Process for removing hydrogen and carbon impurities from glasses by adding a tellurium halide

Abstract

Hydrogen and/or carbon impurities are removed from chalcogenide or chalcoide glasses by the addition of a halide, such as TeCl.sub.4, to the batch composition. During melting of the batch composition, the metal halide reacts with the hydrogen and/or carbon impurities to form a hydrogen halide and/or carbon tetrahalide gas and a metal which becomes incorporated into the chalcogen-based glass. Useful halides include halides of sulfur, selenium, tellurium, polonium, or halides of a metal (such as aluminum, magnesium, zirconium, or a mixture thereof) that forms a stable oxide. Mixed metal halides may also be used. The glass melt is then distilled, outgassed, homogenized, fined, and annealed. An apparatus specially designed for making a fiber preform by the above process is also described. An annealed preform made by this method may be drawn into a low-loss fiber in the 2 .mu.m to 12 .mu.m range.

Claims16

Dependent claims

A method comprising the steps of:

adding tellurium halide to a batch composition, thereby forming a halide-containing batch composition, said batch composition contains hydrogen impurities;
heating said halide-containing batch composition to melt said batch composition thus forming a glass melt, and to react said tellurium halide with said hydrogen impurities to form HCl;
distilling said glass melt to form a distillate essentially free of particulate matter;
and
outgassing said distillate.

2 more elements

A method of forming a glass, comprising the steps of:

providing an apparatus comprising:
a reaction chamber having first and second opposing end surfaces and a longitudinal central axis extending therebetween;
a tailpipe in fluid contact with and extending longitudinally outward from said first opposing end surface of said reaction chamber, wherein said tailpipe forms an airtight connection with said first opposing end surface of said reaction chamber;
and
a tube having a first portion, the entirety of which extends within said reaction chamber, said tube having a second portion extending longitudinally from said second opposing end surface of said reaction chamber and terminating external to said reaction chamber, each end of said tube being closed, said tube defining at least one opening along a circumferential surface of said first portion of said tube, and said tube forming an airtight connection with said second opposing end surface of said reaction chamber;
placing a chalcogenide or chalcohalide batch composition within said reaction chamber, said batch composition containing hydrogen impurities;
adding tellurium halide to said batch composition, thereby forming a halide-containing batch composition;
applying vacuum pressure to said apparatus;
sealing said apparatus under said vacuum pressure;
positioning said apparatus within a two-zone furnace so that said longitudinal axis of said reaction chamber is essentially oriented horizontally, said reaction chamber rests entirely within a first zone of said furnace, and said second portion of said tube rests entirely within a second zone of said furnace;
heating said halide-containing batch composition within said first zone of said horizontally oriented reaction chamber to melt said batch composition to form a glass melt and to react said tellurium halide with said hydrogen impurities to form HCl, while said second zone is at a temperature sufficiently higher than the temperature of said first zone to essentially prevent condensation of any glass or components of said glass melt into said second portion of said tube during said heating;
tilting said reaction chamber so that said second opposing end surface is higher than said first opposing end surface;
distilling said glass melt from said reaction chamber into said second portion of said tube while said second zone of said furnace is at a temperature below the temperature of said glass melt in said reaction chamber, so that said glass melt condenses in said second portion of said tube to form a distillate essentially free of particulate matter;
outgassing said distillate while the temperature of the second zone is at a temperature above the softening point of said distillate, and said first zone is at a temperature high enough to essentially prevent condensation of said distillate into said reaction chamber during said outgassing;
cooling said distillate to form a solid glass;
and
annealing said solid glass.

14 more elements

Dependencies are inferred from the claim text.

Process for removing hydrogen and carbon impurities from glasses by adding a tellurium halide

Life of this patent

Process for removing hydrogen and carbon impurities from glasses by adding a tellurium halide

Life of this patent

Abstract

Claims16