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

摘要

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.

主权项

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.