USRE30883E - Method of producing synthetic quartz glass - Google Patents

Method of producing synthetic quartz glass Download PDF

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Publication number
USRE30883E
USRE30883E US06/121,078 US12107880A USRE30883E US RE30883 E USRE30883 E US RE30883E US 12107880 A US12107880 A US 12107880A US RE30883 E USRE30883 E US RE30883E
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free
quartz glass
hydrogen
fluorine
oxygen
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US06/121,078
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Karlheinz Rau
Fritz Simmat
Albert Muhlich
Norbert Treber
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Heraeus Quarzglas GmbH and Co KG
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Heraeus Quarzschmelze GmbH
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Priority claimed from DE19752536457 external-priority patent/DE2536457C3/en
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/01413—Reactant delivery systems
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/01413—Reactant delivery systems
    • C03B37/0142—Reactant deposition burners
    • C03B37/01426—Plasma deposition burners or torches
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
    • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
    • C03B37/01815—Reactant deposition burners or deposition heating means
    • C03B37/01823—Plasma deposition burners or heating means
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/07—Impurity concentration specified
    • C03B2201/075—Hydroxyl ion (OH)
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
    • C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2207/00—Glass deposition burners
    • C03B2207/80—Feeding the burner or the burner-heated deposition site
    • C03B2207/85—Feeding the burner or the burner-heated deposition site with vapour generated from liquid glass precursors, e.g. directly by heating the liquid
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/08—Doped silica-based glasses containing boron or halide
    • C03C2201/12—Doped silica-based glasses containing boron or halide containing fluorine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2203/00—Production processes
    • C03C2203/40—Gas-phase processes

Definitions

  • the invention relates to a method for the production of synthetic quartz glass, to an apparatus for the practice of the method, and to the use of the synthetic quartz glass.
  • a quartz glass doped either with boron oxide or with fluorine As the jacket material a quartz glass doped either with boron oxide or with fluorine.
  • the fluorine-doped quartz glass is obtained by oxidizing silicon tetrafluoride in accordance with the equation SiF 4 +2H 2 O+O 2 ⁇ SiO 2 +4HF, whereby small amounts of fluorine are to be incorporated into SiO 2 .
  • the oxidation can also be brought about by reactive methods in which no hydrogen or H 2 O is present, such as for example in the high-frequency plasma, so that no hydrofluoric acid will form.
  • hydroxyl-ion-free quartz glass which is substantially free of "water” and thus free of absorption bands at wavelengths of 1.4, 2.2 and 2.7 ⁇ m--hereinafter referred to as "hydroxyl-ion-free"--is known from German Pat. No. 1,208,740.
  • the hydroxyl-ion-free quartz glass is obtained by oxidizing a hydrogen-free silicon compound in a hydrogen-free gas stream containing elemental and/or bound oxygen, and depositing the oxidation product as a vitreous mass on a refractory support, the gas stream being passed through an induction-coupled plasma burner.
  • this invention contemplates an improvement in a process for producing a synthetic hydroxyl ion-free quartz glass wherein a hydrogen-free silicon compound is heated in a hydrogen-free gas stream, the gas stream being passed through an induction coupled plasma burner and containing elemental and/or bound oxygen and the oxidation product is deposited on the refractory support as a vitreous mass, the improvement comprising including in said gas stream a gaseous hydrogen-free thermally decomposable compound which yields fluorine in an amount of at least 500 gms per kg of silica to be produced.
  • the objects of the present invention are achieved in a process for the production of synthetic, hydroxyl-ion-free quartz glass by oxidizing a hydrogen-free silicon compound in a hydrogen-free gas stream containing elemental and/or bound oxygen and depositing the oxidation product as a vitreous mass on a refractory support, the gas stream being passed through an induction-coupled plasma burner, by the fact that, in accordance with the invention, for the achievement of a prescribed reduction of the refractive index of synthetic quartz glass, a hydrogen-free, heat-decomposable fluorine compound in vapor form, especially dichlorodifluoromethane (CCl 2 F 2 ), is introduced into the flame of the plasma burner in the amount of at least 500 g per kg of synthesized SiO 2 .
  • CCl 2 F 2 dichlorodifluoromethane
  • a rod of synthetic, hydroxyl-ion-free quartz glass is used as the refractory support and is set in motion relative to the plasma burner, by rotating it for example, during the depositing of the fluorine-doped, synthetic, hydroxyl-ion-free quartz glass, one obtains a foreproduct for the manufacture of light conducting fibers, which consists of a core of the refractory support material and a covering of fluorine-doped synthetic quartz glass.
  • a parabolic decrease of the refractive index in the covering is obtained if the amount of fluorine compound added is increased as the thickness of the covering increases.
  • a light conducting fiber is then produced by drawing a foreproduct of this kind.
  • a rod of synthetic quartz glass can advantageously be used whose refractive index is increased by the addition of refractive index increasing metal ions. It is advantageous to use a doped rod of synthetic quartz glass whose refractive index decreases with distance from the rod axis.
  • Thermally decomposable hydrogen-free-fluorine compounds which can be used according to the invention include the following: CClF 3 , CF 4 .
  • the amount of hydrogen-free thermally decomposable fluorine compound relative to the hydrogen-free silicon compound would depend upon the nature of the glass desired and in particular the relative amount of the fluorine in the compound. Broadly speaking, however, the weight relationship of the fluorine in the thermally decomposable fluorine compound to the silicon in the hydrogen free silicon compound will be in the range of 50 to 800 gms. fluorine per kg of silicon, preferably between 150 and 300 gms. fluorine per kg of silicon.
  • the process is conducted by heating the hydrogen free silicon compound in the presence of the hydrogen-free gas stream containing elemental and/or bound oxygen and thermally decomposable fluorine compound at temperatures generally in the range of 1800° to 2600° C., preferably between 1850° and 2000° C.
  • the temperatures are employed in an amount sufficient to deposit the so-heated mass upon a refractory support as a vitreous mass.
  • the fluorine is present together with the silicon compound for a residence time of between 0.02 and 0.3 seconds, preferably between 0.04 and 0.15 seconds.
  • a burner having three quartz glass tubes disposed concentrically at some distance from one another, the outer tube overreaching the middle and innermost tube and the middle tube overreaching the innermost tube.
  • the working gas and the silicon compound including the fluorine compound present in vapor form are fed through the innermost tube, and a separating gas, preferably oxygen, is fed through the interstice between the innermost and the middle tube and between the middle tube and outermost tube.
  • a separating gas preferably oxygen
  • Reductions of the index of refraction to values of 1.4532 can easily be achieved in the synthetic quartz glass produced by the process of the invention, thereby providing the assurance that this quartz glass will be suitable also for the manufacture of light-conducting fibers, especially also for those light conducting fibers whose core consists of quartz glass of high purity.
  • FIG. 1 is a side elevational view of an apparatus which can be employed to carry out the claimed process.
  • FIG. 2 is a view similar to FIG. 1 showing a further apparatus for carrying out the claimed process.
  • reference numeral 1 indicates a silicon tetrachloride reservoir from which the silicon tetrachloride is pumped by a proportioning pump 2 through the feed line 2 into a heated vaporizing dish 4, via line 3.
  • Oxygen is fed into the vessel 5 containing the vaporizing dish through the line 6.
  • the mixture of oxygen and silicon tetrachloride formed in vessel 5 is delivered through the ground-glass connection 7-8 made of quartz glass, into the plasma burner.
  • the plasma burner is composed of a metal base 9 and the three quartz glass tubes 10, 11 and 12 which are sealed from one another and from the outside atmosphere within the metal base.
  • the induction coil 13, which is supplied by the high-frequency electric power generator 14 is disposed about the free end of the outermost tube 12.
  • the working gas and the two separating gases T-1 and T-2 are delivered through tangentially disposed lines 15, 16 and 17.
  • a quartz glass piece 19 which serves as the substrate on which the fluorine-doped synthetic quartz glass is deposited.
  • the piece of quartz glass 19 is held on a mandrel 20 in a device 21 which makes it possible to rotate and slowly draw back the piece during the depositing process, as indicated by the arrows 22 and 23.
  • the positioning system 24 it is possible to orientate the quartz glass piece 19 in all three directions with respect to the plasma flame.
  • the igniting of the plasma burner is performed in a conventional manner.
  • Argon gas is introduced through the lines 15 and "ignited" by means of a tungsten rod in the vicinity of the coil 13 which is supplied with high-frequency energy.
  • oxygen is slowly fed to the argon, and the argon content of the mixture is reduced until finally only oxygen is being fed.
  • oxygen is fed through lines 16 and 17 as separating gases T-1 and T-2.
  • the quartz glass piece 19 is advanced into the flame and heated with simultaneous rotation.
  • a temperature of about 1900° C. the vaporous mixture of silicon chloride and oxygen is fed from vessel 5 into the plasma burner and then dichlorodifluoromethane (CCl 2 F 2 ) is admixed, at a rate, for example, of 0.7 kg/h, with the oxygen being introduced through line 15.
  • CCl 2 F 2 dichlorodifluoromethane
  • Due to the high temperature of the plasma flame the SiCl 4 decomposes and reacts with the oxygen to form SiO 2 , which deposits itself on the quartz glass piece 19 and vitrifies.
  • the dichlorodifluoromethane is also decomposed by the high temperature of the plasma flame and fluorine is incorporated into the vitreous SiO 2 in a proportion of, for example, 5000 parts per million.
  • the product fluorine-doped synthetic quartz glass, is free of hydroxyl ions.
  • a rod 19' of hydroxyl-ion-free synthetic quartz glass can be used, as represented diagrammatically in FIG. 2, which is held in end mounts 26 which are longitudinally displaceable and contain machinery for the rotation of the rod 19' (arrows 27 and 28).
  • the fluorine-doped synthetic quartz glass is then deposited as a covering 29 on the rod 19'.
  • the product thus obtained is a foreproduct which can then be drawn directly to form a light-conductive fiber.
  • a plasma burner having three concentric quartz glass tubes in a stepped configuration with the outermost tube overreaching the middle and innermost tubes and the middle tube overreaching the innermost tube, and blanketing the innermost and middle tubes with a separating gas, preferably oxygen, has the advantage that no silica can collect on the burner.

Abstract

An improvement in a method for producing a synthetic hydroxyl ion-free quartz glass wherein a hydrogen free silicon compound is heated in a hydrogen-free gas stream while the gas stream is passed through an induction coupled plasma burner, the gas stream containing elemental and/or bound oxygen and the oxidation product is deposited on a refractory support as a vitreous mass, the improvement lying in including in the gas stream a gaseous hydrogen-free, thermally decomposable compound which yields fluorine in an amount of at least 500 gms. per kilogram of silica to be produced; an apparatus for producing a synthetic OH ion-free quartz glass comprising an induction coupled plasma burner which burner has disposed thereabout 3 concentric quartz glass tubes disposed in stepped configuration of which the outermost tube is the longest and the innermost tube is the shortest. The apparatus includes means for passing through the innermost tube a hydrogen-free gas stream containing elemental oxygen and/or bound oxygen together with a gaseous hydrogen free thermally decomposable compound which yields fluorine. The apparatus further contains means for passing a separating gas such as oxygen through the space defined by the innermost tube and the middle tube and the middle tube and the outermost tube.

Description

This is a continuation of application Ser. No. 713,541, filed Aug. 11, 1976 and now abandoned.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for the production of synthetic quartz glass, to an apparatus for the practice of the method, and to the use of the synthetic quartz glass.
2. Discussion of the Prior Art
For the manufacture of light-conductive fibers having a core and a jacket, it is desirable, especially when high-purity quartz glass is used, to have available a jacket material which has a lower refractive index than the core material. To this end it was proposed in French Patent Application No. 2,208,127 to use as the jacket material a quartz glass doped either with boron oxide or with fluorine. The fluorine-doped quartz glass is obtained by oxidizing silicon tetrafluoride in accordance with the equation SiF4 +2H2 O+O2 →SiO2 +4HF, whereby small amounts of fluorine are to be incorporated into SiO2. However, the oxidation can also be brought about by reactive methods in which no hydrogen or H2 O is present, such as for example in the high-frequency plasma, so that no hydrofluoric acid will form.
It is clear that it is not possible by the disclosed method to produce a fluorine-doped quartz glass in which the fluorine doping will result in a predetermined reduction of the refractive index below that of high-purity quartz glass. It is in this light that one must also interpret the statement made in U.S. Pat. No. 3,869,194, that the differences achieved in the refractive indexes of core material and fluorine-doped jacket material in a light-conductive fiber are so slight that such fibers are not suitable for optical signal transmission.
The production of synthetic quartz glass which is substantially free of "water" and thus free of absorption bands at wavelengths of 1.4, 2.2 and 2.7 μm--hereinafter referred to as "hydroxyl-ion-free"--is known from German Pat. No. 1,208,740. The hydroxyl-ion-free quartz glass is obtained by oxidizing a hydrogen-free silicon compound in a hydrogen-free gas stream containing elemental and/or bound oxygen, and depositing the oxidation product as a vitreous mass on a refractory support, the gas stream being passed through an induction-coupled plasma burner.
Accordingly, it is an object of this invention to provide a repeatable process for the production of a synthetic, hydroxyl-ion-free quartz glass especially such a quartz glass having a refractive index of nD ≦1.4570. It is especially an object of this invention to provide such a process for the production of synthetic hydroxyl-free quartz glass having a fluorine content of at least 4 g per kg of synthesized SiO2.
SUMMARY OF THE INVENTION
Broadly, this invention contemplates an improvement in a process for producing a synthetic hydroxyl ion-free quartz glass wherein a hydrogen-free silicon compound is heated in a hydrogen-free gas stream, the gas stream being passed through an induction coupled plasma burner and containing elemental and/or bound oxygen and the oxidation product is deposited on the refractory support as a vitreous mass, the improvement comprising including in said gas stream a gaseous hydrogen-free thermally decomposable compound which yields fluorine in an amount of at least 500 gms per kg of silica to be produced.
Accordingly, the objects of the present invention are achieved in a process for the production of synthetic, hydroxyl-ion-free quartz glass by oxidizing a hydrogen-free silicon compound in a hydrogen-free gas stream containing elemental and/or bound oxygen and depositing the oxidation product as a vitreous mass on a refractory support, the gas stream being passed through an induction-coupled plasma burner, by the fact that, in accordance with the invention, for the achievement of a prescribed reduction of the refractive index of synthetic quartz glass, a hydrogen-free, heat-decomposable fluorine compound in vapor form, especially dichlorodifluoromethane (CCl2 F2), is introduced into the flame of the plasma burner in the amount of at least 500 g per kg of synthesized SiO2.
At the same time it has been found advantageous to add the fluorine compound in vapor form to the oxygen being supplied for maintaining the flame in the plasma burner. To obtain a deposition product whose refractive index is to vary in a prescribed manner, it is advantageous to increase or decrease the amount of fluorine compound added during the depositing procedure. In such a manner there is produced a glass whose refractive index nD is 1.457 to 1.435. If, in the case of increasing the amount of fluorine compound, a rod of synthetic, hydroxyl-ion-free quartz glass is used as the refractory support and is set in motion relative to the plasma burner, by rotating it for example, during the depositing of the fluorine-doped, synthetic, hydroxyl-ion-free quartz glass, one obtains a foreproduct for the manufacture of light conducting fibers, which consists of a core of the refractory support material and a covering of fluorine-doped synthetic quartz glass.
A parabolic decrease of the refractive index in the covering is obtained if the amount of fluorine compound added is increased as the thickness of the covering increases. A light conducting fiber is then produced by drawing a foreproduct of this kind.
Instead of the rod of synthetic, hydroxyl-ion-free quartz glass, a rod of synthetic quartz glass can advantageously be used whose refractive index is increased by the addition of refractive index increasing metal ions. It is advantageous to use a doped rod of synthetic quartz glass whose refractive index decreases with distance from the rod axis. Thermally decomposable hydrogen-free-fluorine compounds which can be used according to the invention include the following: CClF3, CF4.
As sources of hydrogen-free silicon compound which can be used in accordance with this invention to provide hydroxyl-ion-free quartz glass one can employ the following: SiCl4, SiCl3 F, SiCl2 F2, SiClF3.
Generally speaking the amount of hydrogen-free thermally decomposable fluorine compound relative to the hydrogen-free silicon compound would depend upon the nature of the glass desired and in particular the relative amount of the fluorine in the compound. Broadly speaking, however, the weight relationship of the fluorine in the thermally decomposable fluorine compound to the silicon in the hydrogen free silicon compound will be in the range of 50 to 800 gms. fluorine per kg of silicon, preferably between 150 and 300 gms. fluorine per kg of silicon.
The process is conducted by heating the hydrogen free silicon compound in the presence of the hydrogen-free gas stream containing elemental and/or bound oxygen and thermally decomposable fluorine compound at temperatures generally in the range of 1800° to 2600° C., preferably between 1850° and 2000° C. The temperatures are employed in an amount sufficient to deposit the so-heated mass upon a refractory support as a vitreous mass. The fluorine is present together with the silicon compound for a residence time of between 0.02 and 0.3 seconds, preferably between 0.04 and 0.15 seconds.
It has been found advantageous to use a burner having three quartz glass tubes disposed concentrically at some distance from one another, the outer tube overreaching the middle and innermost tube and the middle tube overreaching the innermost tube. The working gas and the silicon compound including the fluorine compound present in vapor form are fed through the innermost tube, and a separating gas, preferably oxygen, is fed through the interstice between the innermost and the middle tube and between the middle tube and outermost tube. The process of the invention differs from the state of the art particularly in that the fluorine doping of the synthetic quartz glass is no longer subject to caprice, but takes place at a specific, predetermined rate. Reductions of the index of refraction to values of 1.4532 can easily be achieved in the synthetic quartz glass produced by the process of the invention, thereby providing the assurance that this quartz glass will be suitable also for the manufacture of light-conducting fibers, especially also for those light conducting fibers whose core consists of quartz glass of high purity.
BRIEF DESCRIPTION OF DRAWINGS
Referring to the drawings herein:
FIG. 1 is a side elevational view of an apparatus which can be employed to carry out the claimed process; and
FIG. 2 is a view similar to FIG. 1 showing a further apparatus for carrying out the claimed process.
DESCRIPTION OF SPECIFIC EMBODIMENTS
Referring to the drawings herein with the understanding that they serve to diagramatically illustrate the process of the invention, reference numeral 1 indicates a silicon tetrachloride reservoir from which the silicon tetrachloride is pumped by a proportioning pump 2 through the feed line 2 into a heated vaporizing dish 4, via line 3. Oxygen is fed into the vessel 5 containing the vaporizing dish through the line 6. The mixture of oxygen and silicon tetrachloride formed in vessel 5 is delivered through the ground-glass connection 7-8 made of quartz glass, into the plasma burner. The plasma burner is composed of a metal base 9 and the three quartz glass tubes 10, 11 and 12 which are sealed from one another and from the outside atmosphere within the metal base. The induction coil 13, which is supplied by the high-frequency electric power generator 14 is disposed about the free end of the outermost tube 12. The working gas and the two separating gases T-1 and T-2 are delivered through tangentially disposed lines 15, 16 and 17. Into the housing 18 which contains the plasma burner there extends a quartz glass piece 19, which serves as the substrate on which the fluorine-doped synthetic quartz glass is deposited. The piece of quartz glass 19 is held on a mandrel 20 in a device 21 which makes it possible to rotate and slowly draw back the piece during the depositing process, as indicated by the arrows 22 and 23. By means of the positioning system 24 it is possible to orientate the quartz glass piece 19 in all three directions with respect to the plasma flame.
The igniting of the plasma burner is performed in a conventional manner. Argon gas is introduced through the lines 15 and "ignited" by means of a tungsten rod in the vicinity of the coil 13 which is supplied with high-frequency energy. After this ignition, oxygen is slowly fed to the argon, and the argon content of the mixture is reduced until finally only oxygen is being fed. In like manner, oxygen is fed through lines 16 and 17 as separating gases T-1 and T-2.
As soon as the plasma burner is burning properly, the quartz glass piece 19 is advanced into the flame and heated with simultaneous rotation. When a temperature of about 1900° C. is reached, the vaporous mixture of silicon chloride and oxygen is fed from vessel 5 into the plasma burner and then dichlorodifluoromethane (CCl2 F2) is admixed, at a rate, for example, of 0.7 kg/h, with the oxygen being introduced through line 15. Due to the high temperature of the plasma flame the SiCl4 decomposes and reacts with the oxygen to form SiO2, which deposits itself on the quartz glass piece 19 and vitrifies. The dichlorodifluoromethane is also decomposed by the high temperature of the plasma flame and fluorine is incorporated into the vitreous SiO2 in a proportion of, for example, 5000 parts per million.
Since only gases or vapors which are free of hydrogen are used in the process of the invention, the product, fluorine-doped synthetic quartz glass, is free of hydroxyl ions.
Instead of the quartz glass piece 19, a rod 19' of hydroxyl-ion-free synthetic quartz glass can be used, as represented diagrammatically in FIG. 2, which is held in end mounts 26 which are longitudinally displaceable and contain machinery for the rotation of the rod 19' (arrows 27 and 28). The fluorine-doped synthetic quartz glass is then deposited as a covering 29 on the rod 19'. The product thus obtained is a foreproduct which can then be drawn directly to form a light-conductive fiber.
The use of a plasma burner having three concentric quartz glass tubes in a stepped configuration with the outermost tube overreaching the middle and innermost tubes and the middle tube overreaching the innermost tube, and blanketing the innermost and middle tubes with a separating gas, preferably oxygen, has the advantage that no silica can collect on the burner.

Claims (12)

What is claimed is:
1. A method for forming a coating of a fluorine containing synthetic OH ion-free quartz glass on a refractory support which comprises passing a hydrogen-free silicon compound, gaseous oxygen and vaporous CCl2 F2, CClF3 or CF4 in a hydrogen free gas stream through an induction coupled plasma burner whereby said hydrogen-free silicon compound reacts with said oxygen to form synthetic OH ion-free quartz glass, the amount of said CCl2 F2, CClF3 or CF4, passed through said burner, being sufficient to yield .[.a.]. fluorine .[.content in the quartz glass.]. in an amount of at least 500 grams per kg of quartz to be produced whereby there is formed a fluorine-doped synthetic OH ion-free quartz glass and depositing said fluorine-doped synthetic OH ion-free quartz glass as a coating on a refractory support.
2. A method according to claim 1 wherein said refractory support is quartz glass having a rod shape and said synthetic OH ion-free quartz glass formed by reaction of said hydrogen-free silicon compound and said oxygen is deposited thereon, the refractive index of the refractory support being increased by refractive index raising metal ions, the refractive index of said support decreasing with the distance from its axes.
3. A process according to claim 1 wherein a sufficient amount of fluorine is passed through said plasma burner together with said hydrogen-free silicon compound and elemental and/or bound oxygen, that the fluorine containing synthetic OH ion-free quartz glass has a refractory index nD of 1.457 to 1.435.
4. A method according to claim 1 wherein said refractory support is in the form of a rod shape and the resultant synthetic OH ion-free quartz glass is deposited in the form of a sleeve on said rod-shaped support.
5. A method according to claim 1 wherein CCl2 F2 is admixed in vapor form with said oxygen.
6. A method according to claim 1 wherein said CClF3 is admixed in vapor form with said oxygen.
7. A method according to claim 1 wherein said CF4 is admixed in vapor form with said oxygen.
8. A method according to claim 1 wherein the amount of said CCl2 F2, CClF3 or CF4 is increased as the synthetic OH ion-free quartz glass increases in thickness.
9. A method according to claim 1 wherein said hydrogen-free silicon compound is selected from the group consisting of SiCl4, SiCl3 F, SiCl2 F2 and SiClF3.
10. A method according to claim 9 wherein said vaporous CCl2 F2, CClF3 or CF4 is thermally decomposed in said plasma burner at a temperature in the range of 1800° to 2600° C.
11. A method according to claim 10 wherein said CCl2 F2, CClF3 or CF4 is thermally decomposed in said plasma burner at a temperature between 1850° and 2000° C.
12. A method according to claim 9 wherein the weight relationship of the fluorine in said vapor CClF2, CClF3 or CF4 to silicon in said hydrogen-free silicon compound is in the range of 50 to 800 grams fluorine per kg of silicon.
US06/121,078 1975-08-16 1980-02-13 Method of producing synthetic quartz glass Expired - Lifetime USRE30883E (en)

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DE19752536457 DE2536457C3 (en) 1975-08-16 Process for the production of synthetic, OH-ion-free quartz glass, device for carrying out the process and use of the synthetic quartz glass
DE2536457 1975-08-16
DE2536572 1975-08-16

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US71354176A Continuation 1975-08-16 1976-08-11
US05/874,965 Reissue US4162908A (en) 1975-08-16 1978-02-03 Method of producing synthetic quartz glass, apparatus for the practice of the method, and use of the synthetic quartz glass

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CH (1) CH620181A5 (en)
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FR2568242A1 (en) * 1984-07-25 1986-01-31 Int Standard Electric Corp PROCESS AND APPARATUS FOR VAPOR DEPOSITION OF DOPED GLASS
EP0173183A1 (en) * 1984-08-18 1986-03-05 Mitsubishi Materials Corporation Radiation-resistant optical conductor
US4716572A (en) 1984-12-19 1987-12-29 Sigri Gmbh Method for coating carbon and graphite bodies
US4880452A (en) 1984-06-04 1989-11-14 Sumitomo Electric Industries, Ltd. Method for producing glass preform for optical fiber containing fluorine in cladding
FR2714371A1 (en) * 1993-12-24 1995-06-30 Cabloptic Sa Coating optical fibre preform by plasma deposition
US5474589A (en) * 1990-11-28 1995-12-12 Sumitomo Electric Industries, Ltd. UV light-permeable glass and article comprising the same
US20020005051A1 (en) * 2000-04-28 2002-01-17 Brown John T. Substantially dry, silica-containing soot, fused silica and optical fiber soot preforms, apparatus, methods and burners for manufacturing same
US20020083741A1 (en) * 2000-12-29 2002-07-04 Pandelisev Kiril A. Hot substrate deposition of fused silica
US20030002796A1 (en) * 2001-05-22 2003-01-02 Thomas Kupper Optical waveguide
US20040028362A1 (en) * 2002-08-07 2004-02-12 Shin-Etsu Chemical Co., Ltd. Optical fiber preform, method for manufacturing thereof, and optical fiber obtained by drawing thereof
US20040187525A1 (en) * 2003-03-31 2004-09-30 Coffey Calvin T. Method and apparatus for making soot
US20050120752A1 (en) * 2001-04-11 2005-06-09 Brown John T. Substantially dry, silica-containing soot, fused silica and optical fiber soot preforms, apparatus, methods and burners for manufacturing same
US20090020705A1 (en) * 2001-02-26 2009-01-22 Pandelisev Kiril A Fiber Optic Enhanced Scintillator Detector
CN111320177A (en) * 2020-04-13 2020-06-23 黄冈师范学院 Method for removing hydroxyl in quartz sand powder

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FR2428618A1 (en) * 1978-06-16 1980-01-11 Telecommunications Sa Optical fibre preform mfr. - by depositing glass soot on rod of same compsn. and diffusion of fluorine into the rod
FR2432478B1 (en) * 1978-07-31 1982-03-12 Quartz & Silice
JPS5537465A (en) * 1978-09-09 1980-03-15 Nippon Telegr & Teleph Corp <Ntt> Production of glass fiber base material
JPS5852935B2 (en) * 1978-11-20 1983-11-26 三菱マテリアル株式会社 Manufacturing method for optical transmission materials
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DE3036915A1 (en) * 1979-10-09 1981-04-23 Nippon Telegraph & Telephone Public Corp., Tokyo METHOD FOR PRODUCING BLANKS FOR LIGHT-GUIDE FIBERS
FR2476058A1 (en) * 1980-02-15 1981-08-21 Quartz Silice Sa SEMI-PRODUCT FOR THE PRODUCTION OF OPTICAL FIBERS, PROCESS FOR PREPARING THE SEMICONDUCTOR AND OPTICAL FIBERS OBTAINED FROM THE SEMICONDUCTOR
JPS57100928A (en) * 1980-12-12 1982-06-23 Nippon Telegr & Teleph Corp <Ntt> Burner for preparing base material for optical fiber
DE3206177A1 (en) * 1982-02-20 1983-08-25 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Process for the production of a preform from which optical fibres can be drawn
DE3304721A1 (en) * 1983-02-11 1984-08-16 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt METHOD FOR PRODUCING A PREFORM FOR LIGHTWAVE GUIDES
FR2540997B1 (en) * 1983-02-14 1987-02-27 Western Electric Co OPTICAL FIBER MANUFACTURING PROCESS
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JP4763877B2 (en) * 2000-05-29 2011-08-31 信越石英株式会社 Synthetic quartz glass optical material and optical member for F2 excimer laser
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US3659915A (en) * 1970-05-11 1972-05-02 Corning Glass Works Fused silica optical waveguide
US3843229A (en) * 1971-11-25 1974-10-22 Siemens Ag Optical waveguide having a graded refractive index core formed of silicon and germanium
DE2247307A1 (en) * 1972-09-27 1974-03-28 Siemens Ag Quartz glass rods for drawing light-guiding filaments - contg doped core in undoped sheath
US3778132A (en) * 1972-10-06 1973-12-11 Bell Telephone Labor Inc Optical transmission line
FR2253723A1 (en) * 1973-12-07 1975-07-04 Passaret Michel Preform for optical waveguide mfr. - by plasma arc spraying a lower RI glass around or inside a higher RI glass
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Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0096878A1 (en) * 1982-06-14 1983-12-28 International Standard Electric Corporation Fabrication of preforms for optical fibers by chemical vapor deposition using a plasma torch
US4880452A (en) 1984-06-04 1989-11-14 Sumitomo Electric Industries, Ltd. Method for producing glass preform for optical fiber containing fluorine in cladding
FR2568242A1 (en) * 1984-07-25 1986-01-31 Int Standard Electric Corp PROCESS AND APPARATUS FOR VAPOR DEPOSITION OF DOPED GLASS
EP0173183A1 (en) * 1984-08-18 1986-03-05 Mitsubishi Materials Corporation Radiation-resistant optical conductor
US4716572A (en) 1984-12-19 1987-12-29 Sigri Gmbh Method for coating carbon and graphite bodies
US5474589A (en) * 1990-11-28 1995-12-12 Sumitomo Electric Industries, Ltd. UV light-permeable glass and article comprising the same
FR2714371A1 (en) * 1993-12-24 1995-06-30 Cabloptic Sa Coating optical fibre preform by plasma deposition
US7089766B2 (en) 2000-04-28 2006-08-15 Corning Inc Method of forming optical fiber preforms
US20020005051A1 (en) * 2000-04-28 2002-01-17 Brown John T. Substantially dry, silica-containing soot, fused silica and optical fiber soot preforms, apparatus, methods and burners for manufacturing same
US20050155388A1 (en) * 2000-04-28 2005-07-21 Burke Gerald E. Substantially dry, silica-containing soot, fused silica and optical fiber soot preforms, apparatus, methods and burners for manufacturing same
US7797966B2 (en) 2000-12-29 2010-09-21 Single Crystal Technologies, Inc. Hot substrate deposition of fused silica
US20020083741A1 (en) * 2000-12-29 2002-07-04 Pandelisev Kiril A. Hot substrate deposition of fused silica
US20090020705A1 (en) * 2001-02-26 2009-01-22 Pandelisev Kiril A Fiber Optic Enhanced Scintillator Detector
US20050120752A1 (en) * 2001-04-11 2005-06-09 Brown John T. Substantially dry, silica-containing soot, fused silica and optical fiber soot preforms, apparatus, methods and burners for manufacturing same
US20030002796A1 (en) * 2001-05-22 2003-01-02 Thomas Kupper Optical waveguide
US7752869B2 (en) 2002-08-07 2010-07-13 Shin-Etsu Chemical Co., Ltd. Optical fiber preform, method for manufacturing thereof, and optical fiber obtained by drawing thereof
US20050229639A1 (en) * 2002-08-07 2005-10-20 Shin-Etsu Chemical Co., Ltd. Optical fiber preform, method for manufacturing thereof, and optical fiber obtained by drawing thereof
US20040028362A1 (en) * 2002-08-07 2004-02-12 Shin-Etsu Chemical Co., Ltd. Optical fiber preform, method for manufacturing thereof, and optical fiber obtained by drawing thereof
US20040187525A1 (en) * 2003-03-31 2004-09-30 Coffey Calvin T. Method and apparatus for making soot
CN111320177A (en) * 2020-04-13 2020-06-23 黄冈师范学院 Method for removing hydroxyl in quartz sand powder
CN111320177B (en) * 2020-04-13 2023-09-15 黄冈师范学院 Method for removing hydroxyl groups in quartz sand powder

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NL176662B (en) 1984-12-17
CH620181A5 (en) 1980-11-14
DE2536457A1 (en) 1977-02-17
FR2321459B1 (en) 1979-06-22
JPS5224217A (en) 1977-02-23
FR2321459A1 (en) 1977-03-18
NL7609083A (en) 1977-02-18
NL176662C (en) 1985-05-17
GB1492920A (en) 1977-11-23
DE2536457B2 (en) 1977-06-08

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