GLASS. Glass- not just a functional material to let light into an area Used to add decorative effect. Important to choose the right kind of glass for the right place- to be effective, attractive and safe.
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1. 'Ordinary' sheet glass
2. Float glass (plate)
3. Energy efficient glass
4. Patterned (obscured glass)
5. Toughened (Safety glass)
6. Laminated glass
7. Wired glass
9. Picture frame glass
10. Soda-lime glass (or lime glass)
11. Lead-alkali glass(also called lead glass)
12. Borosilicate glass
13. Alumino-silicate glass
14. Ninety-six percent silica glass
15. Fused silica glass
16. Fused Quartz
17. Colouring Glass
most common glass. It is made of oxides of silicon (SiO2), calcium (CaO) and sodium(Na2O).
cheap to make and can be made into a wide variety of shapes; medium resistance to high temperatures and sudden changes of temperature, fair resistance to corrosive chemicals.
used to make bottles and windows
Borosilicate glass is melted and formed into blown bulbs and small diameter tubing at our Central Falls, RI, facility. This glass has high durability, high thermal shock resistance, and high electrical resistivity. Its optical transmission is controlled to cut off harmful ultraviolet radiation. Borosilicate glass is designed for HID (high-intensity discharge) lighting applications, in which hot lamps are exposed to outdoor conditions for many years.
The tubing drawn from this glass seals well to both the tungsten lead wires and the blown bulbs, and therefore is used for flare and exhaust tubing in HID applications.
Fused quartz products are melted and formed at our Exeter facility. Major applications include both the lighting and semiconductor industry.
In lighting products, fused quartz is widely used in high-temperature arc and filament lamps requiring high purity to minimize devitrification and provide optimum sag resistance. These attributes contribute to the long life of these lamps at high operating temperatures.
Major semiconductor manufacturers worldwide use OSRAM SYLVANIA's fused quartz for its high chemical purity, high-temperature resistance, and precise dimensional tolerances. Common applications include furnace tubes for oxidation, CVD and diffusion processes, end caps, transfer carriers, thermocouple tubes, wafer carriers, end plates, baffles and bell-jars for epitaxial reactors.
Electrical conductivity in fused quartz is ionic in nature.
Alkali ions exist only as trace constituents.
Fused quartz is preferred for electrical insulation and low loss dielectric properties.
The electrical insulating properties of clear fused quartz are superior to those of the opaque or translucent types.
Both electrical insulation and microwave transmission properties are retained at very high temperatures and over a wide range of frequencies.
Fused quartz is a solid material at room temperature, but at high temperatures, it behaves like all glasses.
It does not experience a distinct melting point as crystalline materials do, but softens over a fairly broad temperature range.
This transition from a solid to a plastic-like behavior, called the transformation range, is distinguished by a continuous change in viscosity with temperature.
The growth rate of cristobalite from the nucleation site depends on certain environmental factors and material characteristics.
Temperature and quartz viscosity are the most significant factors, but oxygen and water vapor partial pressures also impact the crystal growth rate.
Consequently, the rate of devitrification of fused quartz increases with increasing hydroxyl (OH-) content, decreasing viscosity and increasing temperature.
High viscosity, low hydroxyl fused quartz materials produced , therefore, provide an advantage in devitrification resistance.
The phase transformation to Beta-cristobalite generally does not occur below 1000ºC. This transformation can be detrimental to the structural integrity of fused quartz if it is thermally cycled through the crystallographic inversion temperature range (250 ºC). This inversion is accompanied by a large change in density and can result in spalling and possible mechanical failure.
The molten core glass is placed in the inner crucible. The molten cladding glass is placed in the outer crucible.
The two glasses come together at the base of the outer cucible and a fibre is drawn.
Long fibres can be produced (providing you don't let the content of the crucibles run dry!).
Step-index fibres and graded-index fibrescan be drawn with this method.
A rod of core glass is placed inside a tube of cladding glass. The end of this assembly is heated; both are softened and a fibre is drawn.
Rod and tube are usually 1 m long. The core rod has typically a 30 mm diameter. The core glass and the cladding glass must have similar softening temperatures.
This method is relatively easy: just need to purchase the rod and the tube.
However, must be very careful not to introduce impurities between the core and the cladding.
causes a reaction to take place and then fuses the deposited material.
Plasma-Enhanced Modified Chemical Vapour Deposition is similar in principle to MCVD. The difference lies in the use of a plasma instead of a torch.
The plasma is a region of electrically heated ionised gases. It provides sufficient heat to increase the chemical reaction rates inside the tube and the deposition rate.
This technique can be used to manufacture very long fibres (50 km).It is used for both step index and graded index fibres.
The chemical vapours are oxidised in a flame in a process called hydrolysis.
The deposition is done on the outside of a silica rod as the torch moves laterally.When the deposition is complete, the rod is removed and the resulting tube is thermally collapsed
The deposition occurs on the end of a rotatingsilica boule as chemical vapors react to form silica.
Core preforms and very long fibres can be made with this technique.
Step-index fibres and graded-index fibres can be manufactured this w
Heating the preform
Drawing the fibre