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US 2016/0257599 A1Published application
Easy removal of a thin-walled tube in a powder-in-tube (pit) process
AssigneeOFS Fitel, LLC
InventorDennis J. Trevor
Life of this patent
Estimating the term…
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.
Claims21
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.
8 more elements
(canceled)
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.
5 more elements
(canceled)
12-21. (canceled)
Dependencies are inferred from the claim text.