Preparation of a quartz glass body in a melting crucible of refractory metal

Patent metadata

Field	Value
Publication number	US-11299417-B2
Application number	US-201616062658-A
Country	US
Kind code	B2
Filing date	Dec 16, 2016
Priority date	Dec 18, 2015
Publication date	Apr 12, 2022
Grant date	Apr 12, 2022

Abstract

The invention relates to a process for preparing a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate, ii.) Making a glass melt from the silicon dioxide granulate in a melting crucible, and iii.) Making a quartz glass body from at least a part of the glass melt, wherein the melting crucible is comprised in an oven and is made of at least one material comprising tungsten or molybdenum or a combination thereof. The invention further relates to a quartz glass body which can be obtained by this process. Further, the invention relates to a light guide, an illuminant and a formed body, each of which can be obtained by processing the quartz glass body further.

First claim

The invention claimed is:

1. A process for preparing a quartz glass body comprising pyrogenic silicon dioxide, comprising:
providing a silicon dioxide granulate comprising:
providing a pyrogenic silicon dioxide powder; and
processing the silicon dioxide powder to give a silicon dioxide granulate,
wherein the silicon dioxide granulate has a larger particle diameter than the silicon dioxide powder;

making a glass melt from the silicon dioxide granulate in a melting crucible; and
making a quartz glass body from at least a part of the glass melt;
wherein the melting crucible is comprised in an oven,
wherein the melting crucible is made of at least one material comprising tungsten or molybdenum or a combination thereof, and
wherein the quartz glass body comprises:
an OH content of less than 500 ppm;
a chlorine content of less than 60 ppm;
a tungsten content of less than 1000 ppb;
a molybdenum content of less than 1000 ppb;

wherein the ppb and ppm are based on the total weight of the quartz glass body in each case.

2. The process according to claim 1 , wherein the oven has at least one gas inlet and one gas outlet, wherein a gas which is removed through the gas outlet has a dew point of less than 0° C. on exiting the oven through the gas outlet.

3. The process according to claim 1 , wherein the melting crucible does not have a coating selected from a material comprising rhenium, iridium, osmium or a combination thereof on the surface facing the glass melt.

4. The process according to claim 1 , wherein the quartz glass body comprises at least one of:
an aluminium content of less than 200 ppb;
an ODC content of less than 5·10 15 /cm 3 ;
a metal content of metals which are different from aluminium of less than 1 ppm;
a viscosity (p=1013 hPa) in a range from log 10 (η (1250° C.)/dPas)=11.4 to log 10 (η (1250° C.)/dPas)=12.9, or log 10 (η (1300° C.)/dPas)=11.1 to log 10 (1300° C.)/dPas)=12.2, or log 10 (η (1350° C.)/dPas)=10.5 to log 10 (η (1350° C.)/dPas)=11.5;
a standard deviation of the OH content of not more than 10%, based on the OH content of the quartz glass body;
a standard deviation of the Cl content of not more than 10%, based on the Cl content of the quartz glass body;
a standard deviation of the Al content of not more than 10%, based on the Al content of the quartz glass body;
a refractive index homogeneity of less than 1*10 −4 ; and
a cylindrical form,
wherein the ppb and ppm are based on the total weight of the quartz glass body in each case.

5. The process according to claim 1 , wherein the silicon dioxide powder comprises at least one of:
a BET surface area in a range from 20 to 60 m 2 /g;
a bulk density in a range from 0.01 to 0.3 g/cm 3 ;
a carbon content of less than 50 ppm;
a chlorine content of less than 200 ppm;
an aluminium content of less than 200 ppb;
a total content of metals which are different from aluminium of less than 5 ppm;
at least 70 wt.-% of the powder particles have a primary particle size in a range from 10 to 100 nm;
a tamped density in a range from 0.001 to 0.3 g/cm 3 ;
a residual moisture content of less than 5 wt.-%;
a particle size distribution D 10 in a range from 1 to 7 μm;
a particle size distribution D 50 in a range from 6 to 15 μm; and
a particle size distribution D 90 in a range from 10 to 40 μm;
wherein the wt.-%, ppm and ppb are based on the total weight of the silicon dioxide powder in each case.

6. The process according to claim 1 , wherein the silicon dioxide powder is prepared from a compound selected from the group consisting of siloxanes, silicon alkoxides and silicon halides.

7. The process according to claim 1 , further comprising making a hollow body with at least one opening from the quartz glass body.

8. A process for preparing a light guide, comprising:
providing
a hollow body with at least one opening obtained by a process according to claim 7 ;

introducing one or more core rods into the quartz glass body through the at least one opening to obtain a precursor; and
drawing the precursor from in the warm to obtain a light guide with one or more cores and a jacket.

9. A process for preparing a light guide, comprising:
providing
a hollow body obtained by a process according to claim 7 ;

optionally fitting the hollow body with electrodes; and
filling the hollow body with a gas.

10. A process for preparing a formed body comprising:
providing a quartz glass body according to claim 7 ; and
forming a formed body from the quartz glass body.

Assignees

• Heraeus Quarzglas

Inventors

• Otter Matthias
• Lehmann Walter
• Hünermann Michael
• Nielsen Nils Christian
• Whippey Nigel Robert
• Gromann Boris
• Kpebane Abdoul-Gafar

Classifications

• C03B20/00 Primary

  Processes specially adapted for the production of quartz or fused silica articles {, not otherwise provided for (C03B19/01, C03B19/066, C03B19/106, C03B19/12, C03B19/14, C03B37/00 take precedence)} · CPC title

• C03B2201/23

  doped with hydroxyl groups · CPC title

• C03C2203/10

  Melting processes · CPC title

• C03B2207/42

  Assembly details; Material or dimensions of burner; Manifolds or supports · CPC title

• C03C2201/02

  Pure silica glass, e.g. pure fused quartz · CPC title