[NewCandle] Anodizable metals and essential conditions for glowdischarge?

[Keith Nagel]

Hi Horace + Nick,

Thanks kindly for the thoughts. What you say generally jibes with
my own experiences doing glow work. I do agree with you that the glow occurs
at the surface of the oxide layer. In the case of a barrier layer,
one that is pore free like what you get with boric acid, the glow would be
at the surface
of the oxide layer as horace reports. In the case of a porous layer, like
what you
get with oxalic acid, the glow occurs inside the pore near
the surface of the aluminum. The active region in both cases
is the same, the thin barrier layer separating the electrolyte
from the aluminum. But in the case of a porous layer, that region
is deep inside the pore. You can actually see the thick oxide
layer covering the glow region in that system.

Here is a cross sectional picture of some pores,

http://www.kpnconsulting.com/newcandle/download/alpore1.jpg

You can see that the pore diameters are quite small, on the
order of 10-100 nm, hence our problem seeing them clearly with
the scope.

In this next picture, the shaded area is the region I think
the glow is occurring in. This is the ion transport region,
and the actual oxide growth occurs here.

http://www.kpnconsulting.com/newcandle/download/alpore2.jpg

So if we all agree on the experimental evidence showing glow
for both barrier and porous oxide layers, my earlier speculation
was obviously in error and my explanation above would cover
both cases. Does that seem reasonably to you?

It's worth noting that in the case of the porous
oxide layer that the appearance of the glow will be altered
as the bulk of the oxide is sitting between the viewer and the
glow region. I've seen this with the oxalic acid system;
the oxide layer grows quite thick and I remember clearly seeing it
interposed between the glow and the solution.

I'll have to give that zinc system a try. It also struck me
this morning that I had left magnesium off the list. A
dangerous experiment, but we haven't ignited aluminum yet
so perhaps the magnesium won't catch fire... that would be
very messy, water and magnesium fires are pretty evil.
Fortunately, I now have a safe area I can do these tests
without fear of rousing the ire of the NYFD.

K.

PS: Here's a pic of the results of a lot of tedious sorting,

http://www.kpnconsulting.com/newcandle/download/MVC-002F.JPG

Never again will I paw through a box of resistors or caps looking
for that specific part...


-----Original Message-----
From: newcandle-bounces at ipdiscover.com
[mailto:newcandle-bounces at ipdiscover.com]On Behalf Of Horace Heffner
Sent: Tuesday, September 16, 2008 5:01 AM
To: New energy for the new world.
Subject: Re: [NewCandle] Anodizable metals and essential conditions for
glowdischarge?



On Sep 15, 2008, at 12:08 PM, Nick Reiter wrote:
>
> Could one take say a sputtered conformal coating of
> Al2O3, or SiO2, or ZnO, make it 1000A thick on an
> aluminum or other metal substrate, and get an AGD from
> it?  Does the oxide coating have to be constantly
> re-generating, or native, or just there as dielectric
> layer for tunneling?
>
> It may be a couple of weeks until I can try this out,
> but I do have the ability to sputter some SiO2 as a
> dielectric barrier.

My experience with this, again if memory serves, is that operating in
pure DC mode, in some conditions, tends to build up a barrier until
the width reduces the current. You then have to push voltage to
continue the same glow.  This can eventually lead to operation in
electrospark mode.   Running in AC tends to delay or avoid this.
Running in a reduced concentration electrolyte can avoid an excessive
anodizing rate.

Electron tunneling rate is *very* sensitive to barrier width d.
Width d is in an exp(d*k) term.  Tunneling is limited to layers a few
atoms thick, I think.  Impurities in the the barrier layer permit
tunneling between islands of potential, and thus a much thicker
barrier. This kind of stage-wise tunneling may also be glow related.

The big old electrolytic cells used by phone companies as voltage
regulators exhibited the glow, and they ran for years without any
problems, so that kind of stability can be achieved, but I think it
may be achieved using very large anions, like those in acetic acid.

It also may be significant that the conditioned layers act not only
as a tunneling barrier, but as a diode.  The capacitance effect, the
i vs V "eye" occurs when AC is used, thus when the two electrode
surface diodes are opposed.

Ordinary semiconductor diodes, when pushed very near failure voltage,
I think also can glow. They also breakdown conduct sporadically,
mimicking the electrospark mode, until final failure occurs. There is
no electrolyte handy there to heal them.

Best regards,

Horace Heffner
http://www.mtaonline.net/~hheffner/





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