chief
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electrolyzing Glass ~ making silicon ¬@
Somewhere I read about the effects of electrycity on glass:
==> While it isolates at room-temperature and maybe is an ionic conductor at elevated temps
==> it was reported, that at 200 Celsius it let's a small amount of DC through, and gets black at the points, where the electrodes are applied ...
So maybe the black stuff was silicon (?) and one can manufacture silicon by the electrolysis of glass ? Then It could be possible to make solar cells
somehow this way ?
=====================
Also it wouldn't be necessary to use electrodes, the charges could be sprayed onto the surface ...
==> Once I electrolyzed a copper-sulfate crystel that way, using the 5 kV anode-DC from a small TV ... : After a while elemental copper could be
seen at the point where the charge went into the crystal from the 5 mm distance through the air ...
=====================
Also if silicon could be generated this way, then maybe simple circuits could be realized ... eg. by previously doping the glass superficially (thin
layer) with the one or other element ...
Silicon may usually be somewhat hard to make, but electric current is almost good for anything, and the inertness of the atmosphere,
==> where only heated glass, some kV DC and maybe air (or vacuum) would be present could maybe allow a direct generation of a thin layer of
silicon on glass ...
... most of you get the idea ... ....
How about it ?
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12AX7
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Kilovolts, when volts are needed, is insanely inefficient. Glow discharges are necessarily low current, so it will take a very long time indeed to
form anything of use.
Tim
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IrC
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"So maybe the black stuff was silicon"
I would want to know what the electrodes were. Are you sure it is not as simple as the black material is deposition of electrode material onto the
glass rather than the formation of elemental Si? I am not as good as a lot of you out there at this to where I could calculate the energy required but
I do know this. It takes a hell of a high temperature which represents very large energy. Magnesium burns in sand, or glass (SiO2 in general) ripping
the O2 right out of the sand leaving the Magnesium oxide as powder and elemental silicon. Look at the temperatures required for this reaction. Far
more energy than your few kilo-volts at mere milli-amps. Even if the energy density at a tiny point is high (compare to a record stylus of 3 grams
putting tons of force in the groove at the tiny point as an analogy) for what I mean by this. Even if you were correct solar cells need a large area
to collect light to produce worthwhile power so the idea seems bad from this factor alone. Not to mention the color does not sound right for pure
silicon.
I have pounds of pure silicon and it is silver gray not black.
"Science is the belief in the ignorance of the experts" Richard Feynman
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chief
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The source said: "Tha glass" was colored black ... ; that means it was a effect of the glass, nothing with the electrodes ...
==> Standard glass does not contain anything that could give any such color, except the silicon ...
If 2 Volts are needed and 2 kV are used: Whatever ; we're talking about a thin surface layer, not about converting the entire mass ...
==> Lots of thechnical steps could be spared, so thereby it well would be economically doable ...
Besides: The Temperature of magnesium burning in sand is maybe 3000 K: That is equivalent to 0.25 eV (!)...  , see here: http://physics.nist.gov/cuu/Constants/energy.html
==> Electricity is a high and mighty sort of energy ...
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Contrabasso
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As powdered silicon is available to buy online for sensible money by the kilo, WHY would you want to make it from fused glass? Why would you want to
effectively do electrolysis with KV and milliamps when you need thousands of amp hours to actually achieve any product.
Now getting a sensible method for the purification of lab portions of Si into something semiconductor grade could be interesting. Probably involving
vacuum furnaces and lots of induction heating.
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bquirky
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my first thought would be that the black mark on glass may well just be electrode sputtering.
an esey way to rule this out would be to wash the glass in an acid that would devolve the metal the electrode was made of.
I cant think of any good reason why it would NOT be possible to electrically reduce silicon oxide (regardless of practicaly) but im having trouble
imagining how to set up might look..
I suppose youd want to make your glass the cathode but what whould be the electrolyte ? prehaps H2 with say a graphite annode. but that
discription sounds more like a plasma furnace than an electrolytic cell.
however I do remember when i was reading about sodium sulfur battery's that regular glass becomes a sodium ion conductor at elevated temperatures and
small glass capillary where used as a electrolyte in early NaS battery experiments.
i dont recall any mention of the glass becoming Si.. however they seemed to give up that strategy pretty quickly 
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Sedit
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Quote: Originally posted by chief  | Somewhere I read
==> While it isolates at room-temperature and maybe is an ionic conductor at elevated temps
==> it was reported, that at 200 Celsius it let's a small amount of DC through, and gets black at the points, where the electrodes are applied ...
|
Glass will conduct electricity in the molten state and this effect can be seen by heating a small area of beer bottle with a torch until its glowing
red hot and then placing it in a microwave. In a matter of a minute or so you can melt the whole bottle but if its not red hot first it won't heat up
much at all. There is a video demonstration of this on W-beatys website(not sure if I got the name right but im sure you all heard of him).
As far as using the open air setup you discribed on copper sulfate crystals I must ask. Was the electrod copper? It seems much more likely that what
you where seeing is an example of charge deposition AKA sputtering. This is normaly done in a vaccume but 5mm should be small enough distance to show
some kind of effect. If you look at the mirror coating on the inside of most old tube rectifiers you can see this plain as day since most start off as
clear bulbs but are now coated in a mirror finish.
I say heat a piece of glass until charge starts to flow and then it can be selfsustaining if enough current is passed in to keep the heat up like they
do with Sodium cells.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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12AX7
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| Quote: Originally posted by Sedit | | If you look at the mirror coating on the inside of most old tube rectifiers you can see this plain as day since most start off as clear bulbs but are
now coated in a mirror finish. |
FYI, there are two effects at work here. One, the metallic getter is deposited intentionally, during manufacture. Over time, as it does its job, it
may be consumed, leading to a hazy, sometimes iridescent coating. The getter can be recognized by the support loop on a nearby structure (usually on
the top, but often in the bottom, or one or two on the side) where the material came from.
The other effect grows with use. Often, a shiny spot is seen axially above the cathode, particularly on "hot" tubes (rectifiers and power output
types), which is due to tungsten or nickel evaporation from the heater or cathode. I doubt this is an ionization (sputtering) mechanism, because it's
generally outside the electron beam.
There is a third, but it's more unusual and doesn't occur in normal operation (or at least what seems like normal operation). Abusive use, driving
the tube over rated current, dissipation, temperature and so on, leads to gassiness, which leads to ion bombardment and true sputtering. The direct
symptom of this is a darkened or metallic deposit on the glass outside of holes in the plate structure.
Tim
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not_important
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Note that there is a discussion on producing sodium via electrolysis of hot glass, the metal migrating onto the inside of electric lamp bulbs. If
sodium is the result there, it seems somewhat doubtful that silicon would form under similar conditions.
| Quote: | | Abusive use, driving the tube over rated current, dissipation, temperature and so on, leads to gassiness, which leads to ion bombardment and true
sputtering. The direct symptom of this is a darkened or metallic deposit on the glass outside of holes in the plate structure. |
This was often seen in the output tubes of audio amps used by small time rock bands back in the 1960s, where loudness was equated with skill.
Occasionally, in practice sessions or when stage lighting was correct, you could see the the output stages glowing in thermal red and ion violet. I
suspect Tim could rattle off a list of tubes that were good investments for a sound man to keep on hand :-)
[Edited on 18-4-2010 by not_important]
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