Molecular sieve and similar materials

[DAN MCKENNA]

Posted to CCD-world:
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Roy,

Activated Charcoal is a physisorption getter .  Its adsorption as a function
of temperature follows
the vapor pressure curve of the gas under consideration.
For example H20 has a vapor pressure of  10 ^-16 torr at 77k and 3 *10^-6 at
 173K (-100C).
Next is CO2 10^-8 torr at 77K  and  10 torr at 173K .  

I have found that the dust created by thermal cycling  is a problem for
these kinds of getters .
We are testing a ceramic to see if it is more pratical.

There is a company that builds custom getters 

SAES Getters  (719) 576-3200

They sell both chemisorption and physisorption devices.
In general one needs to heat chemisorption getters to a much
higher temperature to regenerate > 400C.

Dan

mckenna at cfht.hawaii.edu





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