Hydrogen-supported fluorination of soot bodies
The invention relates to a method for fluorinating a soot body. The method involves: a) providing a soot body, and b) treating the soot body with a gas mixture containing hydrogen and C n F 2n+2 (n=1 or 2) at a temperature in the range of (1,280-n*250)° C. to (1,220-n*100)° C.
1. A method for fluorinating a soot body, comprising the steps of
a) providing a soot body, and
b) treating the soot body with a gas mixture comprising hydrogen and C n F 2n+2 , wherein n=1 or 2, at a fluorination temperature in a range of (1,280-n*250)° C. to (1,220-n*100)° C., wherein the gas mixture contains 35 to 95 vol. % nitrogen based on a total volume of the gas mixture at 25° C.
2. The method according to claim 1 , comprising treating the soot body with a gas mixture comprising CF 4 and hydrogen at a temperature range of 1,050 to 1,120° C.
3. The method according to claim 1 , comprising treating the soot body with a gas mixture comprising C 2 F 6 and hydrogen at a temperature range of 750 to 1,000° C.
4. The method according to claim 1 , wherein the gas mixture contains up to 65 vol. % C n F 2n+2 and hydrogen, each based on a total volume of the gas mixture at 25° C.
5. The method according to claim 1 , wherein the gas mixture contains 10 to 60 vol. % C 2 F 6 or CF 4 , each based on a total volume of the gas mixture at 25° C.
6. The method according to claim 1 , wherein the soot body is a porous SiO 2 soot body having a mean density of 0.48 g/cm 3 to 0.77 g/cm 3 and a specific surface area of more than 5 m 2 /g.
7. A fluorinated soot body obtained by the method according to claim 1 .
8. A method for producing a synthetic glass for an optical element comprising the steps of:
i) producing or providing a soot body;
ii) fluorinating the soot body according to claim 1 ;
iii) optionally chlorinating the fluorinated soot body; and
iv) vitrifying the fluorinated soot body at a pressure of less than 0.1 bar at a temperature above the fluorination temperature.
9. The method according to claim 8 , wherein the soot body is produced by depositing SiO 2 particles for mass deposition on a substrate that rotates about its longitudinal axis using at least one depositing burner.
10. The method according to claim 8 , wherein the synthetic glass is a glass tube.
11. A glass obtained by the method according to claim 8 .
12. An optical element produced by the method according to claim 8 .
13. A method of producing an optical fiber from the glass according to claim 11 , comprising elongating the glass while forming a substrate tube and coating the glass on an internal wall of the substrate tube.
14. A method for fluorinating a soot body, comprising the steps of
a) providing a soot body, and
b) treating the soot body with a gas mixture comprising hydrogen and C n F 2n+2 , wherein n=1 or 2, at a fluorination temperature in a range of (1,280-n*250)° C. to (1,220-n*100)° C., wherein the gas mixture contains hydrogen in an amount of up to 15 vol. % based on a total volume of the gas mixture at 25° C.
15. The method according to claim 14 , comprising treating the soot body with a gas mixture comprising CF 4 and hydrogen at a temperature range of 1,050 to 1,120° C.
16. The method according to claim 14 , comprising treating the soot body with a gas mixture comprising C 2 F 6 and hydrogen at a temperature range of 750 to 1,000° C.
17. The method according to claim 14 , wherein the gas mixture contains up to 65 vol. % C n F 2n+2 and hydrogen, each based on a total volume of the gas mixture at 25° C.
18. The method according to claim 14 , wherein the gas mixture contains 10 to 60 vol. % C 2 F 6 or CF 4 , each based on a total volume of the gas mixture at 25° C.
19. The method according to claim 14 , wherein the soot body is a porous SiO 2 soot body having a mean density of 0.48 g/cm 3 to 0.77 g/cm 3 and a specific surface area of more than 5 m 2 /g.
20. A fluorinated soot body obtained by the method according to claim 14 .
21. A method for producing a synthetic glass for an optical element comprising the steps of:
i) producing or providing a soot body;
ii) fluorinating the soot body according to claim 14 ;
iii) optionally chlorinating the fluorinated soot body; and
iv) vitrifying the fluorinated soot body at a pressure of less than 0.1 bar at a temperature above the fluorination temperature.
22. The method according to claim 21 , wherein the soot body is produced by depositing SiO 2 particles for mass deposition on a substrate that rotates about its longitudinal axis using at least one depositing burner.
23. The method according to claim 21 , wherein the synthetic glass is a glass tube.
24. A glass obtained by the method according to claim 21 .
25. An optical element produced by the method according to claim 21 .
26. A method of producing an optical fiber from the glass according to claim 24 , comprising elongating the glass while forming a substrate tube and coating the glass on an internal wall of the substrate tube.