Biomedical Engineering Reference
In-Depth Information
CAUTION! Furnace gloves must be worn while carrying out Step 5.
6. Maintain the furnace at 700 1C for 30 min; then, increase the furnace
temperature to 1300 1C and maintain at this temperature for 3 h.
7. Take the crucible out of the furnace using metal tongs and carefully
pour the molten glass onto a steel plate.
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CAUTION! Furnace gloves must be worn while carrying out Step 7. Also
care must be taken to avoid spillage of molten glass anywhere outside
the steel plate.
8. Leave to cool overnight.
9. Crush glass into smaller fragments using a mortar and pestle. Carry
out further crushing of fragments in a milling machine to obtain
particles in the micrometre/nanometre size range.
10. Pass glass particles through sieves placed on a sieve shaker to obtain
particles of the required size for making glass microspheres.
TIP: In order to reduce the time required to obtain a certain quantity of
glass particles ready to be spheroidised, Steps 9 and 10 can be carried
out in parallel; for example, at intervals of 2 h, the glass particles
present in the uppermost sieve can be reintroduced into the milling
machine for crushing and then placed back in the uppermost sieve for
further sieving.
.
5.2.5 Design of Flame Spheroidisation Apparatus
1. The flame spheroidisation apparatus comprises the following com-
ponent assemblies: (1) blow torch, (2) feed, and (3) collectors (see
Figure 5.1).
2. The blow torch assembly comprises the gas torch fitted to a MAPP-
PLUS gas cylinder. The blow torch assembly is positioned using a retort
stand and three-pronged clamps such that the flame of the gas torch is
horizontal.
3. The feed assembly comprises an aluminium trough with dimensions of
200 mm
20 mm
30 mm, with the edge of one end positioned ap-
proximately 10 mm above the outlet of the torch at a slight angle to the
horizontal by means of a retort stand and clamp. A DC motor (15 800 rpm,
4.5-15 V, 35.8 mm diameter; RS components, Corby, UK) is attached to
the other end of the trough and is connected to an ISO-TECH IPS-405
programmable power supply (RS Components, Corby, UK) by wires
fitted with the required connectors (4 mm banana test plug connectors
for the power supply and alligator test connectors for the motor).
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