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Re: [TCML] Tungsten Electrode Dust



Ian & All,
Hmm That's rather changed things Ian, so there is a possibility it seems
according to the chemistry at any rate. The empirical experience of Brian
(and myself to some extent)  made me think it wasn't, but the fact it has a
metallic origin made me question that.
The rotating electrodes are W (Tungsten) while importantly I forget to
mention that the fixed electrodes are in fact Cu/W alloy. So this could
enhance the effect even more.
The query arose because I lost another SRSG motor at a recent UK teslathon,
and this time I am reasonably sure a streamer strike was not to blame. I am
therefore eliminating possibilities.
Another possibility, a more likely one, and a ** point to watch **  for
anyone running a SRSG with a Fraeu controller, is that maybe I had too much
voltage rise across the motor. In my case I think it was 10 volts or more.
Now that hasn't been a problem on previous motors, but some are more capable
than others obviously (some are also more Chinese in origin than others as
well <grin>)


Regards
Phil T

www.hvtesla.com

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of AusTesla
Sent: Saturday, November 09, 2013 10:09 PM
To: 'Tesla Coil Mailing List'
Subject: Re: [TCML] Tungsten Electrode Dust

Hi,
I've never seen this sort of arc over either, but looking at it purely from
a chemistry viewpoint, the dust is partially conductive.  It is a rather
complex mix of four compounds + intermediates formed when tungsten is heated
in air.  The resulting four primary oxidation products are:

Brown colored tungsten nitride which is conductive
Copper/bronze colored tungsten (IV) oxide, which is highly conductive
Yellow colored tungsten (VI) oxide, which is not conductive (used as a
yellow pigment, WO3)
Blue colored tungsten pentoxide, which is not listed anywhere I have seen as
been conductive, however this one has quite a complicated structure, so I am
not sure about it.

Tungsten (III) oxide is also known but not formed from this process.

Mix these together and you end up with a greyish white powder which is
partially conductive.

Ian

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Phil Tuck
Sent: Sunday, 10 November 2013 3:28 AM
To: tesla@xxxxxxxxxx
Subject: [TCML] Tungsten Electrode Dust


All,
Does anyone know for fact if the fine white dust that you find around a
rotary spark gap, from the ablation of the electrodes, is actually
conductive? One supposes it is, but logic and reality can be differant.
Regards
Phil T

www.hvtesla.com


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