VYCOR

VYCOR denotes one hand, a process for preparing porous glass and quartz glass at relatively low temperatures and on the other hand, the resulting glass.

History

The fact that many glasses to segregation tendency and the resulting micro- phases are different resistant to water, acids and bases, and can thereby be completely removed in the extreme case, a phase, let the early thirties caused the VYCOR process developed by Corning Glass Works. VYCOR glasses were first time in 1934 registered by ME Nordberg and HP Hood for a patent.

The VYCOR process

The advantage of this process is the production of a silica glass at low temperature. Conventionally, for the production of quartz glass temperatures of 2000 ° C is required, the process permits a reduction VYCOR 1000 to 1300 ° C.

The VYCOR process can be described by the following steps.

In the last step, the porous sintered glass under a 30 percent contraction in volume in a clear and nearly pure silica glass together.

In VYCOR glass base, the sodium ions can be replaced by other ions, such as lithium or potassium. But doing so also changes the optimal VYCOR base glass composition, as the Borsäureanomalie in the binary Li2O - B2O3 and K2O - B2O3 glass systems is other alkali concentrations than in the binary Na2O - B2O3 glass system. Sometimes the VYCOR glass melt is also a small amount of aluminum oxide ( Al2O3 ) was added, causing the phase separation and leaching process can be better controlled. It is then in VYCOR quartz glass, a certain Al2O3 residual determine.

Properties of Vycor glass

VYCOR glasses have the following composition and properties:

Properties of Vycor glass

• Linear thermal expansion α = 7-8 × 10-7 K-1
• Maximum thermal load at about 1100 ° C
• Continuous thermal load 800-900 ° C
• Density ρ = 2.18 g · cm -3
• Chemical resistance ( acid, lye and water resistance ) = Class 1
• Softening point of 1500-1530 ° C

Composition of the starting glass and the glass VYCOR

The porous Vycor glass obtained according to step 7) is an opaque, highly porous glass, having a specific surface of 100-300 m² / g, a porosity of 25-40 vol % and a pore diameter of 2-5 nm possesses.

Applications of VYCOR glass

In the production of thermally highly stressed halogen lamps Vycor glass is used primarily in the form of tubes used. Furthermore, it has been found important in the production of simple laboratory equipment, in which case the contraction in volume is taken into account in the manufacturing process.

Applications of porous glass VYCOR

Porous Vycor glass can be used in chromatography, as carriers for catalysts, and in the membrane technology. Being versatile ways it has quickly lost its intermediate character. However, since it is manufactured only in a very narrow range of pore sizes, various studies have been made to modify them by subsequent procedures.