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Evaporating aluminum from tungsten (or tantalum)

eosraptor1 All Messages By This Member #3730 Well, the problems I was having were all thermodynamic in nature.? My little 500 BTU per hour water chiller simply could not take out the 6000 BTU's / hr that the diff pumps were putting into the water loop.? When I switched back to flowing 75 deg F tap water at about a gallon per minute once thru the diff pump water jackets and dump to the ground the problems went away.? I am now dedicating the little chiller to the vapor traps so they are running at like 55 deg F.? I can now run the diff pumps for the 3 hrs it takes to get the chamber down to aluminizing vacuum levels. ? ?? I am noticing that if I heat the tungsten coils slowly that the aluminum candy canes fall off the coils much more often.? When I heat the coils fast the aluminum canes melt in about 5 seconds and wick onto the tungsten as they should.? Not sure how to fix this.? For now, I will heat the coils fast and pay the price of some tungsten oxide getting driven off the coils before the aluminum.? Drew in sunny Florida ------------------------------------------------------------------------------------------------------------------------------ toggle quoted message Show quoted text On Mon, Sep 26, 2011 at 11:11 PM, SVC <donmattox@...> wrote: ? When heating tungsten filaments to evaporate aluminum the first thing that is vaporized is the tungsten oxide. This is why you either need to strip the oxide off (electropolising or by chemical cleaning using an oxidizing agent) before heating or you should use a shutter (closed while premelting the aluminum on the tungsten).? The aluminum will melt and wet the tungsten at temperatures way below what is needed to evaporate the aluminum. When the temperature is increased the aluminum will evaporate Then open the shutter).? Don
Jarvis Krumbein All Messages By This Member #3731 Drew, in a previous reply I suggested that you get a copy of "Proceedures in Experimental Physics" (attached).? That advice still applies.? If you can't find a copy, I can copy the appropriate pages and e-mail them to you.? I think that your filament wetting problem could be solved . ? Jarvis Krumbein ? toggle quoted message Show quoted text From: Andrew Aurigema To: VacuumX@... Sent: Wednesday, October 5, 2011 6:18 AM Subject: Re: [VacuumX] Evaporating aluminum from tungsten (or tantalum) ? Well, the problems I was having were all thermodynamic in nature.? My little 500 BTU per hour water chiller simply could not take out the 6000 BTU's / hr that the diff pumps were putting into the water loop.? When I switched back to flowing 75 deg F tap water at about a gallon per minute once thru the diff pump water jackets and dump to the ground the problems went away.? I am now dedicating the little chiller to the vapor traps so they are running at like 55 deg F.? I can now run the diff pumps for the 3 hrs it takes to get the chamber down to aluminizing vacuum levels. ? ?? I am noticing that if I heat the tungsten coils slowly that the aluminum candy canes fall off the coils much more often.? When I heat the coils fast the aluminum canes melt in about 5 seconds and wick onto the tungsten as they should.? Not sure how to fix this.? For now, I will heat the coils fast and pay the price of some tungsten oxide getting driven off the coils before the aluminum.? Drew in sunny Florida ------------------------------------------------------------------------------------------------------------------------------
eosraptor1 All Messages By This Member #3732 Jarvis, I have that book somewhere.? I will look for it again.? But the fix for me is to warm up the coils a little then turn them up to high and melt the aluminum onto them.? I have tried it many ways and that is what keeps the aluminum from falling off the coils. Drew --------------------------------------------------------------------- toggle quoted message Show quoted text On Wed, Oct 5, 2011 at 12:00 PM, Jarvis Krumbein <kpjarvis2003@...> wrote: ? Drew, in a previous reply I suggested that you get a copy of "Proceedures in Experimental Physics" (attached).? That advice still applies.? If you can't find a copy, I can copy the appropriate pages and e-mail them to you.? I think that your filament wetting problem could be solved . ? Jarvis Krumbein ? From: Andrew Aurigema <eosraptor@...> To: VacuumX@... Sent: Wednesday, October 5, 2011 6:18 AM Subject: Re: [VacuumX] Evaporating aluminum from tungsten (or tantalum) ? Well, the problems I was having were all thermodynamic in nature.? My little 500 BTU per hour water chiller simply could not take out the 6000 BTU's / hr that the diff pumps were putting into the water loop.? When I switched back to flowing 75 deg F tap water at about a gallon per minute once thru the diff pump water jackets and dump to the ground the problems went away.? I am now dedicating the little chiller to the vapor traps so they are running at like 55 deg F.? I can now run the diff pumps for the 3 hrs it takes to get the chamber down to aluminizing vacuum levels. ? ?? I am noticing that if I heat the tungsten coils slowly that the aluminum candy canes fall off the coils much more often.? When I heat the coils fast the aluminum canes melt in about 5 seconds and wick onto the tungsten as they should.? Not sure how to fix this.? For now, I will heat the coils fast and pay the price of some tungsten oxide getting driven off the coils before the aluminum.? Drew in sunny Florida ------------------------------------------------------------------------------------------------------------------------------
Ed Phillips All Messages By This Member #3733 开云体育 'Strong' was written about 1938 and? covered pnysics department practices at Caltech at that time.? Very widely respected book and there really isn't a modern equivalent.? A lot of his stuff on instruments is of course obsolete after over 70 years but the basics are as good today as they are then.? I'd recommend a copy for anyone doing any kind of experiments. Ed Andrew Aurigema wrote: toggle quoted message Show quoted text ? Jarvis, I have that book somewhere.? I will look for it again.? But the fix for me is to warm up the coils a little then turn them up to high and melt the aluminum onto them.? I have tried it many ways and that is what keeps the aluminum from falling off the coils. Drew --------------------------------------------------------------------- On Wed, Oct 5, 2011 at 12:00 PM, Jarvis Krumbein <kpjarvis2003@...> wrote: ? Drew, in a previous reply I suggested that you get a copy of "Proceedures in Experimental Physics" (attached).? That advice still applies.? If you can't find a copy, I can copy the appropriate pages and e-mail them to you.? I think that your filament wetting problem could be solved . ? Jarvis Krumbein ?

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