Tellurite And Fluorotellurite Glasses For Active And Passive

3. Glass batching and melting; MDO 74
Fig. (3.3) shows a typical temperature profile of the melting and annealing furnace
(Instron TF105/4.5/1ZF using an Instron C130011100 power supply containing a
Eurotherm 2408 controller) at 400°C. The furnace was left to equilibrate for 1 hour,
with laboratory air.
Temperature / o C
410
400
390
380
370
360
350
340
330
320
310
300
290
280
270
260
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Depth / cm
Fig. (3.3): Temperature profile of melting and annealing furnace at 400°C.
After melting the glasses were cast into preheated (to around 10°C below Tg) brass or
aluminium moulds (size and shape depending on the desired end product) and
annealed for an hour just below the glass transition temperature ( ≈ Tg – 10°C) then
slowly cooled to room temperature at around 10°C.hr. -1 . Between melts the inner
surfaces of the moulds were cleaned with acetone. In this study three moulds were
used, a small aluminium mould (SA: internal dimensions 3 × 20 × 60 mm, wall
thickness = 5 mm), a large brass mould (LB: internal dimensions 8 × 40 × 50 mm,
wall thickness = 10 mm), and a cylindrical brass mould (CB: internal diameter =
10mm, length = 110 mm, wall thickness = 4 mm). Fig. (3.4) shows these moulds.