High-purity quartz powder, process for producing the same, and glass molding
View Patent ↗Subjects for the invention are to obtain a quartz powder having a high purity and high quality and a process for producing the same and to obtain a glass molding formed by melting and molding the powder and extremely reduced in bubble inclusion. The invention provides a quartz powder, preferably a synthetic quartz powder obtained by the sol-gel method, which, upon heating from room temperature to 1,700° C., generates gases in which the amount of CO is 300 nl/g or smaller and the amount of CO 2 is 30 nl/g or smaller.
1. A quartz powder which, upon heating from room temperature to 1,700° C., generates gases in which the amount of CO is 300 nl/g or smaller and the amount of CO 2 is 30 nl/g or smaller,
wherein said quartz powder has a bulk density of from 1.3 to 1.7 g/cm 3 and a metal impurity content of 500 ppb or lower,
wherein said quartz powder is a synthetic quartz powder produced by a sol-gel method, which comprises:
(a) forming a silica gel by a sol-gel method; and
(b) subjecting said silica gel to a heat treatment in an oxygen-containing atmosphere and subjecting said silica gel to contact with helium gas,
wherein said subjecting said silica gel to a heat treatment in an oxygen-containing gas is carried out either before or after subjecting said silica gel to contact with helium gas.
2. The quartz powder of claim 1 , wherein said silica gel is contacted with helium gas at a temperature of from 400° C. to 1,300° C.
3. The quartz powder of claim 1 , wherein said silica gel is subjected to a heat-treated at a temperature of 1,000° C. or higher for from 10 to 50 hours in an oxygen-containing atmosphere.
4. The quartz powder of claim 1 , wherein said synthetic quartz powder has a metal impurity content of 200 ppb or lower.
5. The quartz powder of claim 1 , wherein said synthetic quartz powder has a metal impurity content of 100 ppb or lower.
6. The quartz powder of claim 1 , wherein said silica gel is brought into contact with helium gas at a temperature of from 600° C. to 1,300° C.
7. The quartz powder of claim 1 , wherein said silica gel is brought into contact with at least one of helium and hydrogen gas at a temperature of from 800° C. to 1,300° C.
8. The quartz powder of claim 1 , wherein said silica gel has an average particle diameter of from 100 to 500 μm.
9. The quartz powder of claim 1 , wherein said silica gel is brought into contact with a mixture of helium and hydrogen gas.
10. The quartz powder of claim 9 , wherein said mixture of helium and hydrogen gas comprises up to 4% hydrogen.
11. The quartz powder of claim 1 , wherein said silica gel is heat-treated at a temperature of 1,200° C. or higher for from 10 to 50 hours in an oxygen-containing atmosphere.
12. The quartz powder of claim 1 , wherein said silica gel is heat-treated at a temperature of 1,000° C. or higher for from 20 to 40 hours in an oxygen-containing atmosphere.
13. The quartz powder of claim 1 , wherein said silica gel is heat-treated at a temperature of 1,000° C. or higher for from 25 to 35 hours in an oxygen-containing atmosphere.
14. The quartz powder of claim 1 , wherein said silica gel is heat-treated at a temperature of 1,000° C. or higher for from 10 to 50 hours in an oxygen-containing atmosphere at a heating rate of 50 to 200° C. per hour.
15. The quartz powder of claim 1 , wherein said silica gel is heat-treated at a temperature of 1,000° C. or higher for from 10 to 50 hours in an oxygen-containing atmosphere at a heating rate of 70 to 150° C. per hour.
16. A glass molding, which is produced by melting and molding a quartz powder of claim 1 .