DIY cryotreatment

[summilux]

I have access to liquid N2 and a ultra-cold freezer (-80oC) and I would like to cryo treat some wire for DIY interconnects and maybe even try a tube. Any idea how this is done commercially? Do they put in right into N2 or do they try to cool it first. I've read that 100 hours is a good time in N2, but do I snap thaw to room temp after that?
Jonathan

[planet10]

Cool off slowly. Warm up is usually just letting the LN boil off slowly. With tubes you have to be very careful not to shock them to death. Practise on useless tubes. Make sure your "fridge" won't implode.

Now that is just what i understand. The pros have a lot of experience, and i know that the guys who do the best tubes do a lot more than just the LN.

dave

[bearberry]

Summilux, you have mail.

bb

[Cal Weldon]

You also have a PM.

[Damon Hill]

Cryogenics - Wikipedia, the free encyclopedia

Start there, then follow some of the links at the bottom of the page for more details.

Liquid nitrogen boils at -321F; be careful.

Generally, it's important to s-l-o-w-l-y change temperature in both directions, and 'dwell time' is important as well. Check for local companies that specialize in cryogenic treatment; you might be able to piggyback on a run for a nominal fee.

If you do this at home, chose a well-ventilated area so nitrogen boiloff doesn't displace ambient oxygen to a hazardously low amount. Breathing nearly pure nitrogen is the same thing as drowning; people >have< died this way.

[timpert]

You should never just plunge an object in LN2, and even when cold, contact of the object with the LN2 should be avoided, unless shock cooling is your goal. It should be cooled to that temp very gradually, you could do this by placing the object in a container that can withstand immersion in LN2 while staying completely tight, and then placing the object to be cryo-ed in a thick and hermetic styrofoam "coffin" inside that container. The object will eventually cool down to LN2 temperature, because the container is fully immersed, but evenly and very slowly, because of the good insulation of the styrofoam. Also, dry your specimen very thoroughly before treating, because any water present will cause havoc at these low temperatures.

You'll need a cryostat (basically a large dewar) to place the container in. Be very careful with admitting LN2, as you want to gently cool the thing off to LN2 temperature. Now, the tricky part is to estimate/control the time it takes for your object to be cryo-ed to reach target temperature. Any measurement probe will give you a significant thermal leak, so this calls for a sophisticated design of your cryo setup.

The whole thing is not trivial, and I'd be very hesitant to try it with valuable tubes before you've figured out a controllable and repeatable process. Its effectiveness is another debate though, I personally doubt if it is worth all the trouble.