Hello, Monday, November 3, 2014, 5:40:30, Chuck Harris wrote: C> I would think that making the teflon coating would be pretty easy. C> What I would try is to put a nichrome boat, and some teflon into the C> vessel, and pull it down to a good vacuum. Then heat up the boat, C> and the teflon should sublime, and condense on the walls of the C> vessel. C> The nichrome boat could be something as simple as wrapping the nichrome C> into a solenoid form around some teflon rod. C> -Chuck Harris Teflon decomposes at high temperatures, releasing some sublimate and a lot of really nasty chemicals, like fluorfosgen. There is a chance that really thin even coating can be produced this way, but a lot of experimentation would be needed. I would try to take samples of PTFE-insulated hookup wire (from different manufacturers, say white Alfa or Belden wire and russian MGTF wire that use slightly different PTFE formula) and try to make coating inside glass tube samples, using copper wire as heater by itself. I doubt that there will be good results, though. "Classic" way with thin slurry application and heating to teflon melt point to make solid film may be more "realistic". C> Bob Camp wrote: >> Hi >> >> It’s been way too many years since my last Maser play session … >> >> Will it fire up *without* the Teflon coating on the bulb? Yes it works *better* >> with the Teflon (less wall interaction). Getting the bulb re-coated might be a >> major pain. It does look ugly in it’s current state. I’m wondering about just >> stripping the bulb and then seeing what works and what does not. >> >> Bob C> _______________________________________________ C> time-nuts mailing list -- time-nuts@febo.com C> To unsubscribe, go to C> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts C> and follow the instructions there. -- Best regards, Yuri mailto:yuri@ostry.ru

Hi Yuri, It would be a very good idea to keep the temperature of the nichrome wire low, and that might be the biggest problem with the vacuum deposition technique... the wire could get too hot in some places, and stay too cool in others. A really uncontrolled experiment, aka: a thermal wire stripper, gets covered with white snow from the teflon vapor released while stripping teflon wire. -Chuck Harris Yuri Ostry wrote: > Hello, > > Monday, November 3, 2014, 5:40:30, Chuck Harris wrote: > > C> I would think that making the teflon coating would be pretty easy. > > C> What I would try is to put a nichrome boat, and some teflon into the > C> vessel, and pull it down to a good vacuum. Then heat up the boat, > C> and the teflon should sublime, and condense on the walls of the > C> vessel. > > C> The nichrome boat could be something as simple as wrapping the nichrome > C> into a solenoid form around some teflon rod. > > C> -Chuck Harris > > Teflon decomposes at high temperatures, releasing some sublimate and a > lot of really nasty chemicals, like fluorfosgen. There is a chance > that really thin even coating can be produced this way, but a lot of > experimentation would be needed. > > I would try to take samples of PTFE-insulated hookup wire (from different > manufacturers, say white Alfa or Belden wire and russian MGTF wire that use > slightly different PTFE formula) and try to make coating inside glass > tube samples, using copper wire as heater by itself. > > I doubt that there will be good results, though. "Classic" way with > thin slurry application and heating to teflon melt point to make solid > film may be more "realistic".

There's been a fair number of papers from Hahvahd about bulb coating for masers. Interestingly enough, here's a patent: http://www.google.com/patents/US3859119 from 1972. I had to figure this out, but Yuri is referring to flourophosgene a.k.a. carbonyl flouride. If you'd like to read a really nice detailed paper on bulb coating for Rb cells, try this one out: http://walsworth.physics.harvard.edu/publications/1999_Phillips_otherdoc.pdf On Mon, Nov 3, 2014 at 3:46 PM, Chuck Harris <cfharris@erols.com> wrote: > Hi Yuri, > > It would be a very good idea to keep the temperature of > the nichrome wire low, and that might be the biggest problem > with the vacuum deposition technique... the wire could get > too hot in some places, and stay too cool in others. > > A really uncontrolled experiment, aka: a thermal wire stripper, > gets covered with white snow from the teflon vapor released > while stripping teflon wire. > > -Chuck Harris > > Yuri Ostry wrote: > >> Hello, >> >> Monday, November 3, 2014, 5:40:30, Chuck Harris wrote: >> >> C> I would think that making the teflon coating would be pretty easy. >> >> C> What I would try is to put a nichrome boat, and some teflon into the >> C> vessel, and pull it down to a good vacuum. Then heat up the boat, >> C> and the teflon should sublime, and condense on the walls of the >> C> vessel. >> >> C> The nichrome boat could be something as simple as wrapping the nichrome >> C> into a solenoid form around some teflon rod. >> >> C> -Chuck Harris >> >> Teflon decomposes at high temperatures, releasing some sublimate and a >> lot of really nasty chemicals, like fluorfosgen. There is a chance >> that really thin even coating can be produced this way, but a lot of >> experimentation would be needed. >> >> I would try to take samples of PTFE-insulated hookup wire (from different >> manufacturers, say white Alfa or Belden wire and russian MGTF wire that >> use >> slightly different PTFE formula) and try to make coating inside glass >> tube samples, using copper wire as heater by itself. >> >> I doubt that there will be good results, though. "Classic" way with >> thin slurry application and heating to teflon melt point to make solid >> film may be more "realistic". >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >