HITEGLA BLOG
Combining quartz glass with other materials in high-temperature environments
Quartz glass, also known as fused quartz, is a material that is exceptionally resistant to high temperatures, thermal shocks and chemicals. Thanks to its properties, it is used in the chemical, electronic, optical and vacuum technology industries. One of the technological challenges is to permanently and tightly bond quartz glass with other materials – such as metals, ceramics or other types of glass – under extreme temperature conditions.
Due to the large difference in thermal expansion between quartz glass and other materials, thermal stresses arise which can lead to joint failure.
Joining methods
A. Welding and melting
Quartz can be welded to quartz by local heating to a temperature above 1700°C (e.g. with a hydrogen-oxygen torch).
Welding to other types of glass (e.g. borosilicate) is difficult due to different softening temperatures and expansion coefficients.
B. Bonding
In high-temperature applications, traditional epoxy adhesives are not suitable.
Ceramic or glass adhesives can be used, but they must be chemically and thermally compatible.
Sol-gel (so-called silica adhesives) can form joints with good resistance up to 1000°C.
C. Active soldering
Active soldering with solder containing Ti, Zr or other active metals is used to join quartz glass with metals (e.g. molybdenum, titanium).
The process usually takes place in a vacuum furnace or protective atmosphere at temperatures of 800–1000°C.
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D. Diffusion and anodic seals
Less commonly used, but possible when joining conductive materials.
They require very clean surfaces and precise control of temperature conditions.
Problems and solutions
Thermal stresses: materials with similar expansion coefficients should be selected.
Joint leaks: it is important to use appropriate buffer coatings or transition layers (e.g. intermetallic alloys).
Chemical reactions at the interface: these can weaken the joint; reactive metals without a passivation layer should be avoided.
Examples of applications
Quartz-metal vacuum feedthroughs (e.g. for vacuum furnaces)
High-temperature lighting (e.g. halogen and HID lamps)
Sensors and optical systems operating in industrial furnaces
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