Sciencemadness Discussion Board

Silicone as anode?

Fantasma4500 - 24-5-2013 at 06:31

i searched around for this first and found only results about silicone rubber material for cells..

but..
we know that SiO2 is pretty chemically resistant.. and also

''It is less reactive than its chemical analog carbon''
https://en.wikipedia.org/wiki/Silicon

apparently silicone isnt very reactive..?
it can be made somewhat easily by thermite reaction of aluminium, sulfur and sand powder..

worth a try? silicone is doubtful as expensive as other common well functioning anode materials.. and i guess its conductive as its a metalloid

Finnnicus - 24-5-2013 at 06:53

Silicon*? The element, right?
And pulled this off a quick google search "From a practical sense, silicon behaves like an insulator at less than 700 deg K and as a conductor at much higher temperatures."
I guess its worth a shot though, if you can be bothered.

[Edited on 25-5-2013 by Finnnicus]

[Edited on 25-5-2013 by Finnnicus]

Fantasma4500 - 24-5-2013 at 08:38

Quote: Originally posted by Finnnicus  
Silicon*? The element, right?
And pulled [url=http://wiki.answers.com/Q/What_is_silicon's_electrical_conductivity]this[/url off a quick google search "From a practical sense, silicon behaves like an insulator at less than 700 deg K and as a conductor at much higher temperatures."
I guess its worth a shot though, if you can be bothered.

brilliant.. i know silicon powder is somewhat readily available from fireworks suppliers as a very fine powder.. possibly this could substitute PbO2 on epoxy-PbO2 anodes..

papaya - 24-5-2013 at 11:42

Even betters idea seemed to me using SiC rods (heating elements) to electrolyze brine. However I got contradicting results out of my experiments, sometimes it holds well, when most times it breaks apart quickly(in mechanical terms) and when it happens conductivity falls down radically - I think due to SiO2 formation. Only thing I figured out based on my tests - when the pH raises it starts to fail. Another thing I tried - to put some PbO2 on it from nitrate solution (not controlled very unscientific tests, as I didn't have materials) and here also - once it held a long time, some PbO2 deposited, but as there was not enough Pb in solution it just started to bubble there (stand well). Next time with a fresh nitrate /HNO3 solution it fell apart, not a single PbO2 crystal grew on it...
If you have materials, precious scales and enough patience - try to play with SiC - it's better than graphite, at least more conductive, hard and durable, you may get good results (I gave up too early here, also I never heard any discussion on this promising thing).

Fantasma4500 - 24-5-2013 at 15:02

oh thats pretty sad.. carbon can be held together with microfiber cloth ive heard, should keep it in place, i havent tried it myself tho.. also using oil on the surface should do a great difference

but SiC.. sounds hard to make or get a hold of..?

phlogiston - 24-5-2013 at 15:47

You can buy silicon wafers on ebay. Doped silicon (N or P) is conductive.

Example:
http://www.ebay.com/itm/6-150mm-Silicon-Wafer-Wafers-With-Gr...

Without specifying what the electrolytic reaction is you would be using it for, no one will be able to tell if silicon is a good choice or not. Given your comment on PbO2, I am guessing you would like to make chlorate/perchlorate. In that case, no idea how well it would work.

Diablo - 24-5-2013 at 17:22

I think that silicon would probably form an oxide lay if used as an anode.

papaya - 25-5-2013 at 00:17

SiC is used as a heating element in the form of tubes/rods for high temperature furnaces, the one I had is a multi-walled tube, consisting of pressed crystalline SiC. Don't thing making is possible for amateur, it is made of sand+graphite powder by heating (putting voltage at the ends).
Also I consider my experiments with it very inconsistent/unfinished, so I never want state the word ''impossible''.

[Edited on 25-5-2013 by papaya]

Fantasma4500 - 25-5-2013 at 14:26

Quote: Originally posted by phlogiston  
You can buy silicon wafers on ebay. Doped silicon (N or P) is conductive.

Example:
http://www.ebay.com/itm/6-150mm-Silicon-Wafer-Wafers-With-Gr...

Without specifying what the electrolytic reaction is you would be using it for, no one will be able to tell if silicon is a good choice or not. Given your comment on PbO2, I am guessing you would like to make chlorate/perchlorate. In that case, no idea how well it would work.



could be plausible.. the thing i find interesting is that its even less reactive than carbon.. hope i might one day bump into some silicon metalloid of some sort.. heard they put them in computers, or read that in some book of the elements under silicon.. never saw it tho, it was supposed to be plates looking abit like glass but being actually pure ''metallic'' silicon

Fantasma4500 - 25-5-2013 at 14:28

Quote: Originally posted by Diablo  
I think that silicon would probably form an oxide lay if used as an anode.


perhaps perhaps not.. its stated to be less reactive than carbon

Fantasma4500 - 25-5-2013 at 14:31

Quote: Originally posted by papaya  
SiC is used as a heating element in the form of tubes/rods for high temperature furnaces, the one I had is a multi-walled tube, consisting of pressed crystalline SiC. Don't thing making is possible for amateur, it is made of sand+graphite powder by heating (putting voltage at the ends).
Also I consider my experiments with it very inconsistent/unfinished, so I never want state the word ''impossible''.

[Edited on 25-5-2013 by papaya]


tubes / rods.. thats just perfect as a anode.. does these things go by any specific or fancy names?
doubt they call it SiC rods (:

i mean carbon and silicon.. very surely this sounds better than just plain graphite in which i HAVE HEARD should be possible to keep from falling apart by wrapping microfiber cloth around it
basically the current can and will pass through the cloth through the liquid it soaked up, and the graphite particles should be kept in place by the microfiber cloth
then conbining that with SiC rods would be a interesting mix

papaya - 25-5-2013 at 14:44

It is also called carborundum, but the exact name for elements will vary from brand to brand. There's a page on it in wiki. Another important difference from graphite - it's structure is similar to diamond(well it seems it has lot's of modifications, but let's dream) with 50% of carbon atoms replaced with silicon, so it's very tough mechanically(must stand better) in contrast to graphite. Even if it's not durable enough alone, it must be easier to plate with PbO2 than graphite (which's getting oxidized) or titanum (passivation), and the surface is rough so may be less cracking there.

[Edited on 25-5-2013 by papaya]

12AX7 - 25-5-2013 at 15:24

Aluminum silicon alloys are apparently excellent for anodizing. Maybe not general info but it doesn't sound good.

Regarding wafers, it has to be doped -- commercial grade lump is probably quite conductive, but lightly doped (usually P) or intrinsic (~pure) material makes a passable insulator.

Tim

Diablo - 25-5-2013 at 19:18

Quote: Originally posted by Antiswat  
Quote: Originally posted by Diablo  
I think that silicon would probably form an oxide lay if used as an anode.


perhaps perhaps not.. its stated to be less reactive than carbon


Although I don't know about this as an anode silicon will develop a nonconductive oxide lay with exposure to steam and air. But if this means it will develop an oxide layer as an anode then it could be used as a substrate for other anodes kind of like titanium.

[Edited on 5-26-2013 by Diablo]

jock88 - 27-5-2013 at 05:49


The wafers on ebay are also only highly doped in small regions and the whole wafer is not conductive. It cannot conduct electricity from one end to the other.
It's all been tried before. AFAICT.

Fantasma4500 - 27-5-2013 at 06:21

im very sure this will be better than just graphite in several ways, also considering that usually graphite rods are made by clay and graphite powder being heated.. the clay very surely playes a significant role in the corrosion

sadly i found this on wiki..

''Pure SiC is colorless. The brown to black color of industrial product results from iron impurities. The rainbow-like luster of the crystals is caused by a passivation layer of silicon dioxide that forms on the surface.''

question is.. how long time does this take to happen, and since this should be a quite tough material, wouldnt that mean you could use this as a substrate anyways..?
perhaps if this was used as a cathode and was constantly kept wet it might work..
it could however happen to react with water forming SiO2 and H3O (not balanced i know, but you get the idea)

i have found on alibabba a heater stick (i take heater stick as being water heater..?)
this could perhaps show potential of not reacting with water, but then again it doesnt need to be conductive to keep on heating water up.. could this material be used to form glass objects by controlled oxidizing it?

aluminium oxide and silicon carbide could probably work, question would be if aluminium oxide would ruin the conductivity?

what im most worried about is the availability of this thing.. if i ever happen to find an easily available source of SiC i will 100% run stress tests on its performance as cathode and anode

papaya - 27-5-2013 at 11:22

The impurities in SiC are even wanted, because very pure SiC is non-condictive, like diamond, and highly doped by impurities it's conductivity is close to metals(OK,not) rather than semiconductors. Also from my test - even if it passivates, it takes hours (unlike titanium), current gets down slowly and degradation is observed by naked eye. I even think, that conductivity loss is caused not by SiO2 between crystal/liquid interface, bet between pressed crystals (it's not monocrystalline). Also there may be conditions under which it'll not degrade at all - for example I noticed in NaCL solution it'll not happen from the beginning, but starts from some moment and then gets worse, which I think indicates, that it's not stable in alkaline medium, but may hold well in neutral. Also using as a substrate is attractive compared to Ti, which cannot be easily coated with PbO2 under anodic conditions (passivates instantly or oxidized by PbO2 later) and needs another layer between them. I'm not advocating this type of anode, since I don't really know much about what can be done with it, just that it's kind of not investigated opportunity.
I don't know what you found on alibaba, but you must be sure it's SiC, which is usually used in high-temperature furnaces for metal smelting,for example (it doesn't need an inert atmosphere as high as 1600°C if I remember correctly), it may be for water heaters also (I don't know), but I've heard there's also MoSi2 type of thing exist, which is also used as a heating element not to confuse (also another option?).

Fantasma4500 - 29-5-2013 at 06:57

Quote: Originally posted by papaya  
The impurities in SiC are even wanted, because very pure SiC is non-condictive, like diamond, and highly doped by impurities it's conductivity is close to metals(OK,not) rather than semiconductors. Also from my test - even if it passivates, it takes hours (unlike titanium), current gets down slowly and degradation is observed by naked eye. I even think, that conductivity loss is caused not by SiO2 between crystal/liquid interface, bet between pressed crystals (it's not monocrystalline). Also there may be conditions under which it'll not degrade at all - for example I noticed in NaCL solution it'll not happen from the beginning, but starts from some moment and then gets worse, which I think indicates, that it's not stable in alkaline medium, but may hold well in neutral. Also using as a substrate is attractive compared to Ti, which cannot be easily coated with PbO2 under anodic conditions (passivates instantly or oxidized by PbO2 later) and needs another layer between them. I'm not advocating this type of anode, since I don't really know much about what can be done with it, just that it's kind of not investigated opportunity.
I don't know what you found on alibaba, but you must be sure it's SiC, which is usually used in high-temperature furnaces for metal smelting,for example (it doesn't need an inert atmosphere as high as 1600°C if I remember correctly), it may be for water heaters also (I don't know), but I've heard there's also MoSi2 type of thing exist, which is also used as a heating element not to confuse (also another option?).


well heating elements arent that interesting really..
they just transfer energy as in heat but no actual electricity (:
anyhow as of what i remember Mo is pretty resistant stuff, i base this idea on the fact that the higher Mo content a steel type has the more corrosion resistant it is (yes.. SUPER steel.. cant remember the names of it now tho)

the none the less i hope to get around the thing with graphite with fibercloth to keep it from falling apart, sounds very logical that it would last nearly unlimited that way

papaya - 29-5-2013 at 11:52

"well heating elements arent that interesting really..
they just transfer energy as in heat but no actual electricity (:" :o:o
You PRODUCE heat by passing electrical CURRENT through SiC rod (wires to both sides), do you understand how it works?

Fantasma4500 - 30-5-2013 at 15:25

Quote: Originally posted by papaya  
"well heating elements arent that interesting really..
they just transfer energy as in heat but no actual electricity (:" :o:o
You PRODUCE heat by passing electrical CURRENT through SiC rod (wires to both sides), do you understand how it works?



well yes and no.. i dont really see this as acting as an anode or cathode in this case still, but rather still just as resisting the current and thereby picking up energy in form of heat..? yes?
apart from that i dont know much on electricity.. but i do know that if you lead electricity through something thats really poorly conductive it gets hot in little time (nichrome wire for instance)

hyfalcon - 30-5-2013 at 16:30

Quit playing around and just get some MMO. Lasared is at it again on ebay.

http://www.ebay.com/itm/EXPANDED-TITANIUM-MESH-STRETCHED-SCR...

Fantasma4500 - 31-5-2013 at 02:59

Quote: Originally posted by hyfalcon  
Quit playing around and just get some MMO. Lasared is at it again on ebay.

http://www.ebay.com/itm/EXPANDED-TITANIUM-MESH-STRETCHED-SCR...


true true.. i already have MMO tho.. but its not the idea of taking a and b and then getting c.. its about experimenting and perhaps finding something new and better..
people didnt just sit down and clap their hands when they found out about black powder, did they?
no offense whatsoever.. but graphite is often used for beginners and if it would appear that SiC or Si would be easily available by chance it could be a brilliant substitute to graphite
also possibly as substrate that doesnt break easily or tear up when the coating wears off

the thing is you need to see the possibilities and not only the shining product

papaya - 31-5-2013 at 09:43

Antiswat, it's not really a poor conductor, I would say it is as conductive as graphite is and even more close to metals. And in it's application as a heater they put a HUGE amperage through it, even metals will get red hot, it not that this is just a high resistance.. Though, look up for exact parameters (resistance, etc) somewhere and compare, I don't know exact numbers.

Fantasma4500 - 2-6-2013 at 05:35

oh.. so it cant be because its poor when it comes to leading electricity.. it must be something about its chemical resistance after all..
the problem with these types of materials is that theres very little information on them..
ill try

papaya - 2-6-2013 at 10:05

Is this you are trolling on something you never held in your hands? Please make more constructive comment hereafter, there's a FB to express personal opinions, housewives will highly regard!