# US 11,299,417 B2 · Preparation of a quartz glass body in a melting crucible of refractory metal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,299,417 B2 - Document ID: US11299417B2 - Status: Granted - Kind: B2 - Application number: 16/062,658 - Filed: 2016-12-16 - Published: 2019-03-07 - Granted: 2022-04-12 - Earliest claimed: 2015-12-18 - Assignees: Heraeus Quarzglas GmbH & Co. KG - Applicants: Heraeus Quarzglas GmbH & Co. KG - Inventors: Matthias Otter; Walter Lehmann; Michael Hünermann; Nils Christian Nielsen; Nigel Robert Whippey; Boris Gromann; Abdoul-Gafar Kpebane - Web page: https://patentgrep.com/patent/US11299417B2 ## CPC - C03B 37/01211: {by inserting one or more rods or tubes into a tube} - C03B 5/06: in pot furnaces {(C03B5/02 takes precedence)} - C03B 17/04: Forming tubes or rods by drawing from stationary or rotating tools or from forming nozzles - C03B 20/00: 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)} - C03C 3/06: with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)} - C03B 2201/04: Hydroxyl ion (OH) - C03B 2201/07: Impurity concentration specified - C03B 2201/23: doped with hydroxyl groups - C03B 2207/42: Assembly details; Material or dimensions of burner; Manifolds or supports - C03C 2201/02: Pure silica glass, e.g. pure fused quartz - C03C 2203/10: Melting processes - G01N 21/412: {Index profiling of optical fibres} - Y02P 40/57: Improving the yield, e-g- reduction of reject rates - C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES - 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 - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 1) 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. ### Claim 4 (depends on 1) 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 5·1015/cm3; a metal content of metals which are different from aluminium of less than 1 ppm; a viscosity (p=1013 hPa) in a range from log10 (η (1250° C.)/dPas)=11.4 to log10 (η (1250° C.)/dPas)=12.9, or log10 (η (1300° C.)/dPas)=11.1 to log10 (1300° C.)/dPas)=12.2, or log10 (η (1350° C.)/dPas)=10.5 to log10 (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. ### Claim 5 (depends on 1) 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 m2/g; a bulk density in a range from 0.01 to 0.3 g/cm3; 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/cm3; a residual moisture content of less than 5 wt.-%; a particle size distribution D10 in a range from 1 to 7 μm; a particle size distribution D50 in a range from 6 to 15 μm; and a particle size distribution D90 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. ### Claim 6 (depends on 1) 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. ### Claim 7 (depends on 1) The process according to claim 1, further comprising making a hollow body with at least one opening from the quartz glass body. ### Claim 8 (depends on 7) 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. ### Claim 9 (depends on 7) 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. ### Claim 10 (depends on 7) 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.