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Re: [VacuumX] Evaporating aluminum from tungsten (or tantalum)

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  • Andrew Aurigema
    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
    Message 1 of 14 , Oct 5, 2011
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      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.     

      http://www.youtube.com/watch?v=NvmUV5lQziY

      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

      ------------------------------------------------------------------------------------------------------------------------------



      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
      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
      Message 2 of 14 , Oct 5, 2011
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        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
         
        <Andrew, see if you can get a copy of "Proceedures in Experimental Physics" by John Strong.  Originally <published by Prentiss-Hall and later reprinted , I think by Willmann-Bell.  While no longer in print it contains the <answers to many of your problems.  The chapter on coating (evaporation & sputtering) includes detailed <instructions for prepareing evaporation sources and prefusing aluminum to tungstan coils.

        From: Andrew Aurigema <eosraptor@...>
        To: VacuumX@yahoogroups.com
        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.     

        http://www.youtube.com/watch?v=NvmUV5lQziY

        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

        ------------------------------------------------------------------------------------------------------------------------------




      • Andrew Aurigema
        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
        Message 3 of 14 , Oct 5, 2011
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          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
           
          <Andrew, see if you can get a copy of "Proceedures in Experimental Physics" by John Strong.  Originally <published by Prentiss-Hall and later reprinted , I think by Willmann-Bell.  While no longer in print it contains the <answers to many of your problems.  The chapter on coating (evaporation & sputtering) includes detailed <instructions for prepareing evaporation sources and prefusing aluminum to tungstan coils.

          From: Andrew Aurigema <eosraptor@...>
          To: VacuumX@yahoogroups.com
          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.     

          http://www.youtube.com/watch?v=NvmUV5lQziY

          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
          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
          Message 4 of 14 , Oct 5, 2011
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            '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:
             

            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
             
            <Andrew, see if you can get a copy of "Proceedures in Experimental Physics" by John Strong.  Originally <published by Prentiss-Hall and later reprinted , I think by Willmann-Bell.  While no longer in print it contains the <answers to many of your problems.  The chapter on coating (evaporation & sputtering) includes detailed <instructions for prepareing evaporation sources and prefusing aluminum to tungstan coils.


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