Ultra low expansion glass
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Ultra low expansion glass (ULE) is a registered trademark of Corning Incorporated. ULE has a very low coefficient of thermal expansion and contains as components silica and less than 10% titanium dioxide. Such high resistance to thermal expansion makes it very resistant to high temperature thermal shock. ULE has been made by Corning since the 1960s,[1] but is still very important to current applications.
There are many applications for ULE, but by far the most common is for mirrors and lenses for telescopes in both space and terrestrial settings. One of the most well known examples of the use of ULE is in the Hubble Space Telescope's mirror. Another good example of its application is in the Gemini telescope's mirror bank. This type of material is needed for this application because the mirrors on telescopes, especially very large, high-precision units, cannot bend or lose their shape even slightly. If this were to happen, the telescope would be out of focus.[1] Some other examples and uses of ULE are:
- Ultra-low expansion substrates for mirrors and other optics
- Length standards
- Lightweight honeycomb mirror mounts
- Astronomical telescopes
- Precision measurement technology
- Laser cavities
Another newer use for this material that is showing promise is in the semiconductor industry, this again because of the purity and extreme low expansion of ULE glass.[1]
Structure
The structure of ULE is completely amorphous; because of this it is a glass, not a ceramic. The amorphous structure of the material comes from there being no crystal phases within the structure, so there is no long range order.
