Tellurite And Fluorotellurite Glasses For Active And Passive

8. Fibre drawing; MDO 335
glass surface when it came into contact with the aluminium (e.g. 1½TeO2 + 2Al +3
Al2O3 + 1½Te +4 ) at temperatures around its melting point (660°C [8]). Aluminium is only
protected by an Al2O3 layer of the order of nm, and the oxyfluoride melt would be
relatively reactive, on casting in the 670 to 800°C region.
8.1.3. Fibre drawing
Fibre was pulled from glass preforms of 1 cm diameter using a Heathway Soft Glass
Research Tower, in a class 10,000 cleanroom. Fig. (8.2) shows this fibre drawing tower.
Glass preforms were lowered into the hot zone of the furnace, and held there until the
glass softened and necked down. At this point the fibre was pulled manually onto the
drum and attached with tape. The preform was then fed, and the drum rotated and
traversed automatically pulling fibre until most of the preform had been used. Table (8.3)
summarises the draw parameters used for preforms in this study.