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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Does any one know of material that can be used at cryo temp ?
Im not sure about acetal, polyethylene or teflon. it doesnt have to last long, like staying in shape without cracking for 15 minutes at cryo temp is all thats needed. It would close a narrow gap and not see much force.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Patrick wrote ...
Does any one know of material that can be used at cryo temp ?
Im not sure about acetal, polyethylene or teflon. it doesnt have to last long, like staying in shape without cracking for 15 minutes at cryo temp is all thats needed. It would close a narrow gap and not see much force, and only used once or twice.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
indium foil is the standard choice (read the MSDS first, and use proper gloves): a. Clean with Acetone b. Etch with dilute 10% hydrochloric acid to remove oxides c. Rinse with DI water to remove the HCl c. Dry in nitrogen gas d. Tension bolts immediately on prepped mated surfaces (see car head-gasket bolt pattern for tutorial) e. Re-tension bolts at operating temperature
Similar instructions with safety precautions are mentioned here:
indium remains malleable at low temperatures, and can form a unique surface bond with some alloy parts. It is very common in aerospace, as is trying to use the same alloy for a complete assembly.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Like carbon rod said, indium will work well as long as it only needs to work at cryogenic temperatures (indium melts at like 100C). The business with etching and whatnot is not really necessary, we routinely seal vacuum chambers to better than a trillionth of an atmosphere with just wiping down the surfaces with ethanol and clamping down on a 1mm indium wire. The wire flows under the pressure and forms a cold weld to most metals (we have used aluminum, copper, and stainless successfully). The really important part is to put pushoff screws so that you can pry the two parts apart after they are bonded
For higher temperatures or applications that need to be re-usable teflon is good. I have even heard that silicone will work but I have not tried it myself, AAIK even the low temperature silicones become brittle at about -150C.
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Cryogenic pressure gasket material.
