# US 2010/0167906 A1 · Process of making a dense synthetic silica glass, a muffle furnace for performing the process, and silica glass obtained from said process > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2010/0167906 A1 - Document ID: US20100167906A1 - Status: Published application - Kind: A1 - Application number: 12/647,200 - Filed: 2009-12-24 - Published: 2010-07-01 - Earliest claimed: 2008-12-29 - Inventors: Lars Ortmann; Rolf Martin; Ulrich Strobel; Jens Marzinkowski; Hans-Juergen Schmidt; Hans-Juergen Mueller - Web page: https://patentgrep.com/patent/US20100167906A1 ## CPC - C03B 37/01406: {Deposition reactors therefor} - C03B 37/0142: {Reactant deposition burners} - F27B 5/04: adapted for treating the charge in vacuum or special atmosphere - F27B 5/06: Details, accessories or equipment specially adapted for furnaces of these types - C03B 2207/06: Concentric circular ports - C03B 2207/20: Specific substances in specified ports, e.g. all gas flows specified - C03B 2207/42: Assembly details; Material or dimensions of burner; Manifolds or supports - C03B 2207/60: Relationship between burner and deposit, e.g. position - Y02P 40/57: Improving the yield, e-g- reduction of reject rates - C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES - F27B: FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract The process of making synthetic silica glass occurs in a combustion chamber of a muffle furnace. It includes producing a gas flow containing a fuel, an oxidizer, and a silicon compound that is converted by flame hydrolysis and/or by chemical oxidation to SiO2 particles, and depositing them on a target to form a roll-shaped silica glass body. The combustion chamber is provided with a gas inlet and a gas outlet arranged at opposite ends of the combustion chamber, which widens from the inlet to the outlet. The gas flow is produced by a central nozzle for the silicon compound, a first concentric ring-shaped nozzle for the oxidizer, and a second concentric ring-shaped nozzle for the fuel. The process is characterized by a ratio of areas of ring gaps of the ring-shaped nozzles of from 1:4 to 1:6.1. The apparatus for the process is also part of the invention. ## Claims ### Claim 1 A process of making synthetic silica glass in a combustion chamber of a muffle furnace, said process comprising the steps of: a) producing a gas flow in the combustion chamber, said gas flow containing a fuel, a chemical oxidizing agent, and a gaseous silicon compound, which is converted by flame hydrolysis and/or by chemical oxidation to SiO2 particles; and b) depositing the SiO2 particles on a target surface of a target in the combustion chamber so as to form a roll-shaped silica glass body; wherein the combustion chamber is bounded by chamber walls and has a front end provided with a gas inlet and a rear end provided with a gas outlet, and said chamber walls and said outlets are arranged rotationally symmetric in relation to a longitudinal axis of the combustion chamber and said combustion chamber widens in a direction from the gas inlet to the gas outlet; wherein the gas flow is produced by at least three nozzles, said three nozzles comprising a central nozzle for supplying the silicon compound arranged at said front end of the combustion chamber, a first ring-shaped nozzle for supplying the oxidizing agent arranged concentric to and spaced from said central nozzle, and a second ring-shaped nozzle arranged concentric to the central nozzle, which has a diameter that is greater than a diameter of the first ring-shaped nozzle; wherein the first ring-shaped nozzle has a first ring gap and the second ring-shaped nozzle has a second ring gap and a ratio of an area of the second ring gap to an area of the first ring gap is from 1:4 to 1:6.1. ### Claim 2 (depends on 1) The process as recited in claim 1, wherein SiCl4 is supplied from the central nozzle together with dry oxygen as carrier gas. ### Claim 3 (depends on 1) The process as recited in claim 1, further comprising removing consumed gases. ### Claim 4 (depends on 3) The process as recited in claim 3, wherein the consumed gases are removed by evacuation or suction at a pressure of 3 to 250 mbar. ### Claim 5 (depends on 1) The process as recited in claim 1, wherein at least 99% of the space for the nozzles and suction are accommodated by the walls of the muffle furnace. ### Claim 6 (depends on 1) The process as recited in claim 1, wherein the target surface of the target has a temperature of at least 1600° C. during the depositing. ### Claim 7 (depends on 1) The process as recited in claim 1, further comprising feeding the chemical oxidizing agent and the fuel into the combustion chamber through at least four concentrically arranged alternating ring nozzles arranged around said central nozzle. ### Claim 8 (depends on 1) The process as recited in claim 1, wherein the combustion chamber has a housing that extends at least 200 mm beyond the target surface of the target. ### Claim 9 A muffle furnace for making synthetic silica glass, said muffle furnace comprising a combustion chamber housed within muffle furnace walls, which has a longitudinal axis and is provided with a front gas inlet opening and a rear gas outlet opening, wherein said walls, said inlet opening, and said outlet opening are arranged rotationally symmetrically in relation to said longitudinal axis and said combustion chamber widens in a direction from the gas inlet opening to the gas outlet opening; a central nozzle for supplying a gaseous silicon compound, said central nozzle being arranged in the vicinity of the front inlet opening on said longitudinal axis; a first ring-shaped nozzle for supplying an oxidizing agent arranged concentric to and spaced from said central nozzle; and a second ring-shaped nozzle arranged similarly concentric to the central nozzle, which has a diameter that is greater than a diameter of the first ring-shaped nozzle; wherein the first ring-shaped nozzle has a first ring gap and the second ring-shaped nozzle has a second ring gap and a ratio of an area of the second ring gap to an area of the first ring gap is from 1:4 to 1:6.1. ### Claim 10 (depends on 9) The muffle furnace as recited in claim 9, further comprising an optoelectronic device that detects growth of a roll-shaped silica glass body produced by deposition of SiO2 particles on a target surface in the combustion chamber and controls an adjusting motor, which moves the silica glass body out from the combustion chamber by a distance about equal to a length that the silica glass body has grown. ### Claim 11 (depends on 10) The muffle furnace as recited in claim 10, having a maximum diameter such that a ratio of the maximum diameter to a diameter of the silica glass body is from 1.3:1 to 2.5:1. ### Claim 12 (depends on 9) The muffle furnace as recited in claim 9, wherein the combustion chamber has a housing that extends at least 200 mm beyond the optoelectronic device. ### Claim 13 (depends on 12) The muffle furnace as recited in claim 12, wherein the housing has a lower part and an upper part and the lower part extends out from the upper part by a distance equal to at least 1.1 times a length of the upper part along the longitudinal axis. ### Claim 14 (depends on 13) The muffle furnace as recited in claim 13, wherein one end of the lower part of the housing has a half ring-shaped closure for closing an interior of the combustion chamber. ### Claim 15 (depends on 1) A synthetic silica glass obtained by the process recited in claim 1.