Apiezon® N Cryogenic High Vacuum Grease
Technical information
Introduction:
Apiezon® N grease is one of today's most widely used vacuum
greases within the field of cryogenics, where its ability improve heat
transfer and its craze-free performance characteristics at low temperatures
are especially important. The product is also widely used at ambient
temperatures. To place an order, return to our Apiezon N product page.
Thermal Coupling Medium
Apiezon® N grease is important for the coupling of cooling
systems to superconducting magnets, cryostats, temperature sensors or any
system which is required to reach cryogenic temperatures as quickly as
possible.
With its ability to fill the micropores of adjoining surfaces, and its
resistance to cracking and crazing at low temperatures, Apiezon N grease
increases the area of contact and therefore improves thermal coupling across
the whole contact area.
Although the absolute thermal conductivity value of Apiezon N grease is less
than that for indium, the NASA Ames Research Center has shown a significant
practical improvement in heat transfer across pressed metallic joints
augmented with Apiezon N grease compared to those augmented with indium. As
more information about this work becomes known, we will add it to this
webpage.
In addition, Apiezon N grease does not suffer from the problem of creep,
which is traditionally associated with indium, and is ideal for applications
where thermal cycling occurs, as it has the ability to withstand frequent
cycling between temperatures in the range of -273° C and + 30° C. Low levels
of magnetic susceptibility also make it ideal for certain superconductor
manufacturing applications.
Easy to apply, the grease provides a simple, efficient and cost effective
means of increasing thermal conductivity at liquid helium temperatures and
is widely used in the manufacture of all types of cryogenic equipment,
including magnetic resonance imaging (MRI) magnets, cryostats, and scientific
instruments, including electron microscopes.
Sensor mounting medium
Apiezon N grease is an ideal sensor mount, which is especially suited for
the mounting of sensors within holes. Pliable at room temperature, it
solidifies at cryogenic temperatures to ensure the easy mounting and removal
of sensors without causing damage.
Sample mounting medium
Important in low temperature testing of semiconductor chips, laser diodes,
and crystals, etc., 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 ensures samples at the lowest possible temperatures and
improved test sensitivities. The grease is hydrocarbon based and subsequently
luminescent in UV light. For optical testing, the grease should be covered
by the sample, alternatively calibration may account for emissions caused
by the grease.
Cryogenic vacuum seal
Low vapor pressures are imperative for any vacuum sealing medium to ensure
the best possible vacuum attainable. Apiezon N grease exhibits extremely
low vapor pressures at ambient (room) temperatures, which are further
improved by reductions in temperature to the cryogenic region, as
demonstrated by extrapolation of the vapor pressure data above.
It slow temperature resistance to cracking is of particular benefit in the
vacuum sealing of cryosystems where Apiezon N grease can be relied upon to
maintain an effective, crack free seal for long periods, even in applications
which are subject to frequent thermal cycling.
Apiezon N grease is widely used to ensure vacuum or pressure tight seals in,
among other, vacuum lines, cold traps, optical parts on electron microscopes,
ground glass joints, stopcocks, taps Schlenk lines and liquid helium hoses. It
can also be used to improve cryogenic o-ring seals by filling any surface or
o-ring imperfections.
Migration Resistant
Since Apiezon N grease is pure hydrocarbon in composition, it does not suffer
from the problems of "creep" or "carry over" traditionally associated with
silicone greases, therefore avoiding the risk of sample contamination or clouding
of optical surfaces.
Heat Capacity as a Function of Temperature
Properties of Apiezon "N" Grease, Density = 960. kg/m3.
Temp
K | Cp
J/kg-K | delH
J/kg | Diffus
m2/s | Cond
W/m-K | I(KdT)
W/m |
|
| 1.4 | 0.771 | 0.000 | 0.240-3 | 0.177-1 | 0.000 |
| 4.2 | 1.70 | 1.80 | 0.582-4 | 0.950-1 | 0.153 |
| 10.0 | 21.0 | 57.8 | 0.595-5 | 0.120 | 0.850 |
| 20.0 | 89.6 | 85. | 0.151-5 | 0.130 | 2.12 |
| 50.0 | 375 | 0.730+4 | 0.389-6 | 0.140 | 6.21 |
| 77.0 | 471 | 0.190+5 | 0.318-6 | 0.144 | 10.0 |
| 100.0 | 560 | 0.306+5 | 0.279-6 | 0.150 | 13.4 |
| 150.0 | 900 | 0.670+5 | 0.208-6 | 0.180 | 21.6 |
| 200.0 | 0.116+4 | 0.118+6 | 0.189-6 | 0.210 | 31.4 |
| 250.0 | 0.182+4 | 0.190+6 | 0.132-6 | 0.230 | 42.4 |
| 273.0 | 0.240+4 | 0.237+6 | 0.104-6 | 0.240 | 47.8 |
| 300.0 | 0.365+4 | 0.317+6 | 0.685-7 | 0.240 | 54.3 |
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Friday October 10, 2008
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