On Jan 17, 2006, at 10:49 AM, Ian White, GM3SEK wrote:
>
> Just arrived home to read Rich, Karl-Arne, then Rich again...
>
> > On Jan 17, 2006, at 3:25 AM, Karl-Arne Markström wrote:
> >
> >> If I understand the physics correctly, the zirconium getter simply
> >> dissolves and binds the
> >> gas molecules in its own molecule structure.
> >>
> >> An interesting treatment of getters in general can be found in
> >> http://www.thevalvepage.com/valvetek/getter/getter.htm
> >>
> >> Zirconium getters have their own section at about mid-page.
>
> Thanks, Karl-Arne, that's a very interesting reference.
>
> >>R. Measures wrote:
>> Interesting indeed. Thanks, Karl Arne. So Nitrogen doesn't form a
>> compound with Zr, the Zr acts as a N2-sponge?
>
> It's hard to choose exactly the right words to describe what happens
> at the metal surface. At the microscopic scale, the surface is very
> rough and it might have internal pores like a sponge... but 'acts as a
> sponge' isn't really the right image.
>
> 'Dissolved' isn't really right either, because the gas-metal
> interactions take place almost exclusively with the atoms right on the
> surface of the metal.
>
> At the atomic scale, the metal surface has many 'unsatisfied' chemical
> bonds, so gas atoms can attach to those. Oxygen tends to form strong
> bonds with metals, while species like molecular nitrogen (N2) don't
> have much chemical affinity with metals; but they can still be held by
> weaker chemical forces.
>
> Since the reaction doesn't involve all the metal atoms, it doesn't
> form any distinctive chemical compound.
What element would easily form a co-valent bond with N2?
>
>> Haveyou ever seen a Zr gettering wire wrapped around a a
>> thoriated-tungsten filament? Have you ever observed that the leakage
>> current of a 3-500Z that has long been in storage decreases after the
>> filament has been lit for 100 or so hours?
> The 3-500Z has its getter on the anode, so heating just the filament
> isn't going to make much difference, is it?
>
>
So there is nothing to be gained by running the filament? In the past
I have always operated new 3-500Zs at normal anode temperatures without
delay.
>
> 73 from
> Ian GM3SEK
>
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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