Easy removal of a thin-walled tube in a powder-in-tube (pit) process

Patent metadata

Field	Value
Publication number	US-2016257599-A1
Application number	US-201514640584-A
Country	US
Kind code	A1
Filing date	Mar 6, 2015
Priority date	Mar 6, 2015
Publication date	Sep 8, 2016
Grant date	—

Abstract

The embodiments disclosed herein seek to ameliorate high costs associated with the use of ultra-pure silica by using a lower-cost starting material and purifying the lower-cost starting material to an acceptable level of purity during the preform manufacturing process. In one embodiment, a nucleating compound is coated on a thin-walled silica tube, which upon cooling, forms cristobalite allowing for easy removal of the thin-walled silica tube.

First claim

1 . A powder-in-tube preform manufacturing process, comprising:
sealing a bottom of a thin-walled silica tube, the silica tube having a wall thickness of approximately 7 millimeters (mm), the silica tube having an inner diameter that is between approximately 35 mm to approximately 90 mm, the silica tube having a tube length of approximately 1.2 meters (m); inserting a core rod into the silica tube, the inserted core rod being substantially centered within the silica tube; coating the silica tube with a layer of a nucleating compound selected from the group consisting of: aluminum containing salts, calcium, magnesium, and barium. filling the silica tube with mesoporous silica grains, the mesoporous silica grains being substantially monodisperse in size; applying a vapor-phase purification process to the mesoporous silica grains, the vapor-phase purification process being applied at a temperature that is less than approximately 1300 degrees Celsius (° C.); applying a vacuum to the silica tube to decrease the pressure within the silica tube; sintering the mesoporous silica grains in the presence of the vacuum and at a temperature that is greater than approximately 1000° C.; consolidating the silica tube to form a preform; and cooling the preform to below approximately 280° C.

2 . The process of claim 1 , the size of the mesoporous silica grains being between approximately 25 microns and approximately 250 microns.

3 . The process of claim 2 , the size of the mesoporous silica grains being approximately 150 microns.

4 . (canceled)

5 . A preform manufacturing process, comprising:
coating a silica tube with a nucleating compound; filling the silica tube with silica grains; applying a vapor-phase purification process to the silica grains; forming an α-cristobalite layer on the silica tube from the nucleating compound; sintering the silica grains; consolidating the silica tube to form a preform; and cooling the preform to convert the α-cristobalite into 0-cristobalite.

6 . (canceled)

7 . The process of claim 5 , the silica grains being substantially homogeneous mesoporous silica grains.

8 . The process of claim 7 , the mesoporous silica grains having a grain size of approximately 150 microns.

9 . The process of claim 5 , the silica grains comprising an ultra-pure silica powder.

10 . The process of claim 5 , the nucleating compound being selected from the group consisting of: aluminum containing salts, calcium, magnesium, and barium.

11 . The process of claim 5 , the silica tube comprising low-quality silica.

12 - 21 . (canceled)

22 . A product manufactured using the process of claim 1 .

23 . A product manufactured using the process of claim 2 .

24 . A product manufactured using the process of claim 3 .

25 . A product manufactured using the process of claim 5 .

26 . A product manufactured using the process of claim 7 .

27 . A product manufactured using the process of claim 8 .

28 . A product manufactured using the process of claim 9 .

29 . A product manufactured using the process of claim 10 .

30 . A product manufactured using the process of claim 11 .

Assignees

• Ofs Fitel Llc

Inventors

• Trevor Dennis J

Classifications

• C03B37/01211 Primary

  by inserting one or more rods or tubes into a tube · CPC title

• C03B37/01257

  Heating devices therefor · CPC title

• C03B37/0128 Primary

  starting from pulverulent glass · CPC title

• C03B2201/02

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

• C03B37/01237

  to modify the diameter by heat-polishing, e.g. fire-polishing · CPC title