Greases for Cryogenics
What is cryogenics?
A large portion of the scientific community consider cryogenic temperature to be -150°C and below. In North America -180°C is also used which is derived from the boiling points of atmospheric gases. At the opposite end of the cryogenic temperature range is absolute zero (-273°C) which is the temperature at which all molecular motion ceases. Due to quantum mechanics it isn’t possible to fully reach absolute zero, however scientists have been able to get as close as -272.999999999999°C!
At these low temperatures atoms and molecules move much more slowly. This is important for a lot of current cutting edge scientific research, such as quantum technology, which is often performed in cryostats at temperatures as low as possible.
What are the best greases for cryogenic applications available from Apiezon?
Apiezon N Grease is one of the most widely used vacuum greases in cryogenics. This cryogenic grease is specially formulated to exhibit craze-free performance characteristics at low temperatures and withstand frequent cycling between cryogenic temperatures as low as -273°C and +30°C.
Manufactured by M&I Materials Ltd, Apiezon’s cryogenic N Grease is hydrocarbon based and does not suffer from the problem of creep, traditionally associated with indium. Its ability to fill the micro pores between adjacent surfaces improves thermal transfer across the complete surface area.
As a thermal coupling medium, Apiezon N grease is important for any system that is required to reach cryogenic temperatures quickly, such as coupling cooling systems, superconducting magnets, cryostats or temperature sensors. Low levels of magnetic susceptibility also make it ideal for superconductor manufacturing applications.
Apiezon N Grease is also ideal for sensor mounting, pliable at room temperature; it solidifies at cryogenic temperatures to allow for easy mounting and removal of sensors without causing damage. Apiezon N grease is used to improve thermal contact between the sample and sample boat or the sample boat and cold finger of a cryostat. This thermal contact grease ensures that samples are at the lowest possible temperatures to improve test sensitivities.
To achieve the best possible vacuum, low vapour pressures are imperative for any vacuum sealing medium. Apiezon N grease exhibits extremely low vapour pressures at ambient temperatures, which are further improved by reductions in temperature to the cryogenic region.
Apiezon N Grease is widely used to ensure vacuum tight seals in vacuum lines, cold traps, and optical parts on electron microscopes, ground glass joints, stopcocks, taps, Schlenk lines and liquid helium hoses. It can also be used to improve o-ring seals.
Apiezon greases for cryogenic applications FAQs
Q: How do you clean off Apiezon hydrocarbon greases?
A: Wipe off any excess grease with a soft clean lint free cloth. Any residues of grease can be washed away with warm soapy water or by using any aromatic hydrocarbon solvent (toluene, xylene). For a more environmentally friendly solvent, we recommend limonene. They cannot be cleaned using alcohols (ethanol, IPA) or ketones (acetone, MEK).
Q: What happens to Apiezon N grease above its melting point?
A: All the greases (apart from H grease) liquefy but then return to their normal state and properties on cooling, providing the temperature rise has not been excessive