Vycor is the brand name of Corning's high-silica, high-temperature

glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...

. It provides very high

thermal shock Thermal shock is a phenomenon characterized by a rapid change in temperature that results in a transient mechanical load on an object. The load is caused by the differential expansion of different parts of the object due to the temperature chang ...

resistance. Vycor is approximately 96%

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

and 4%

boron trioxide Boron trioxide or diboron trioxide is the oxide of boron with the formula . It is a colorless transparent solid, almost always glassy (amorphous), which can be crystallized only with great difficulty. It is also called boric oxide or boria. It h ...

, but unlike pure

fused silica Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO2) in amorphous (non-crystalline) form. This differs from all other commercial glasses, such as soda-lime glass, lead glass, or borosil ...

, it can be readily manufactured in a variety of shapes. Vycor can be subject to prolonged usage at 900 °C. Vycor products are made by a multi-step process. First, a relatively soft alkali-borosilicate glass is melted and formed by typical glassworking techniques into the desired shape. This is heat-treated, which causes the material to separate into two intermingled "phases" with distinct chemical compositions. One phase is rich in alkali and boric oxide and can be easily dissolved in

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

. The other phase is mostly silica, which is insoluble. The glass object is then soaked in a hot acid solution, which leaches away the soluble glass phase, leaving an object which is mostly silica. At this stage, the glass is

porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

. Finally, the object is heated to more than 1200 °C, which consolidates the porous structure, making the object shrink slightly and become non-porous. The finished material is classified as a "reconstructed glass". For some applications the final step is skipped, leaving the glass porous. Such glass has a high affinity for water and makes an excellent

getter A getter is a deposit of reactive material that is placed inside a vacuum system to complete and maintain the vacuum. When gas molecules strike the getter material, they combine with it chemically or by adsorption. Thus the getter removes small ...

for water vapour. It is widely used in science and engineering. Vycor has an extremely low coefficient of thermal expansion, just one quarter that of

Pyrex Pyrex (trademarked as ''PYREX'' and ''pyrex'') is a brand introduced by Corning Inc. in 1915, initially for a line of clear, low-thermal-expansion borosilicate glass used for laboratory glassware and kitchenware. It was later expanded in the 1 ...

. This property makes the material suitable for use in applications that demand very high dimensional stability, such as

metrology Metrology is the scientific study of measurement. It establishes a common understanding of Unit of measurement, units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to stan ...

instruments, and for products that need to withstand high thermal-shock loads. Vycor also has

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

transmission to about 250 nm and is used in some germicidal lamps. Based on a reference thickness of 1mm, Vycor glass has an approximately 90% transmission spectra from ~300 nm to 3100 nm. Immersing the porous glass in certain chemical solutions before the final consolidation step produces a colored glass that can withstand high temperatures without degrading. This is used for colored glass filters for various applications. Corning manufactures Vycor products for high-temperature applications, such as evaporating dishes. Porous vycor is a prototypical matrix material for the study of confined liquid physics. Vycor can also be used for removal of ²³¹Pa and ²³³Pa in fuel recycling.

References

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External links

Corning Inc.
Manufacturer's website
Momentive Performance Materials, Inc.
Quartz and Low Softening Point Glass (LSPG) Manufacturer
Phase separation in borosilicate and alkali earth silicate glasses
{{Glass makers and brands Glass trademarks and brands Transparent materials