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Author: Subject: Multilayer Metal Oxide / Titanium Anodes for Chlorate/Perchlorate
dann2
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[*] posted on 17-3-2008 at 14:39


Hello,

There is some info here on Perchlorate formation which you may have seen before.

http://www.geocities.com/lllwolly/further/perkform.zip

I have not really read up on it myself, but will now!. (I know sfa about it).
In the patent (@100) they may be just referring to the fact that if you have cups (as opposed to not having any) then the cathodes WILL be surrounded with the 'hydroxid liquid', and not the usual bulk Perchlorate cell electrolyte (whatever that usually is).

I had not intended to try this myself but I am beginning to wonder. It's may be a good way for the home producer to go.

Would flower pots, red unglazed ones with no hole in the bottom, do. Xenoid used them for something somewhere.
Like most of these's things, the only way is to 'suck it and see' (as put very elegantly my someone else in here).:D

I have me doubts about their being some combination(s) of coatings that when put together will suddenly create a Perchlorate cell resistant, Perchlorate producing anode.
May be wrong though. Xenoid is has done a hugh amount of work.

Dann2

[Edited on 17-3-2008 by dann2]
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microcosmicus
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[*] posted on 17-3-2008 at 14:51


As far as choice of material, pretty much any (SiO2)x(Al2O3)y + fluxes
material should work because all that matters is that it be inert. Since no
specific composition was specified, I would by default assume that they
used porcelain. I think that your flowerpot would be just fine since
nineteenth-century sources often talk about porous cups of earthenware.

If you can't or don't want to make or improvise your own porous cup, you
can purchase one from SK/Boreal for $6.95:

http://sciencekit.com/student-cell-and-porous-cup/p/IG002471...

For $32.95, they will throw in a cell and some electrodes.


[Edited on 17-3-2008 by microcosmicus]
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dann2
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[*] posted on 17-3-2008 at 15:09


Hello,

What reaction is going on at the Cathode?
It would appear that all the 'action' is at the Anode only.

Cheers,
Dann2
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chloric1
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[*] posted on 17-3-2008 at 17:10


@dann2- cathode attracts positive ions. In the case of sodium, sodium hydroxide can be generated in a separated catholyte. I did this myslef with steel electrodes, a flower pot impregnated with magnesium hydroxide, and NaCl.

The system is by no means 100% separated but is is significant. Significant enough to yield perchlorate I think. I wonder if maybe what would happed is if the acid in the anolyte releases some chlorine dioxide which creates some perchloric acid with water and so on until little or no chlorate remains.




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dann2
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[*] posted on 17-3-2008 at 20:37


Hello,

@Chloric1. T'was yourself that was using the flower pot, now that I think of it, though I think Xenoid was doing something that caused a hole to appear in the bottom of the flower pot due to the magnetic stirrer bar.

Anyhow, the cell would be in interesting project. It may make Perchlorate easily achievable using Graphite alone, or MnO2 for total 'mess free' Perchlorate.
You could always start with just one flower pot with the anode in it, as opposed to a number of pots with cathodes in each of them, and see how it goes (suck and see, SAS :D).

Graphite as far as I can tell (from my own experience) will not make Perchlorate in significant quantities. Apart from the erosion, there is damm all Perchlorate available from the cell ( Perchlorate cell using Graphite), when it is run for a ridiculous amount of Amper Hours. The Graphite just does not seem to have the required catalytic effect in the normal Perchlorate cell. But that may all change in this type of cell where conditions are different (apart from having less erosion). The time I ran my Perchlorate cell, using Graphite, the pH was inclined to go acidic though.
Some info. here for what it's worth (you seen this before).
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

Two refs. for Perchlorate making with Graphite are here:
Sihvonen, G., Suomen Kemistilehti, 10B, 27 (1937)

Ullman, Frits, "Enzyklopadie der technischen Chemie", Vol. 3, p 299-307, Berlin, Urban & Schwarzenberg, 1929

...........if anyone is rambling around the more dustier shelves of their favourite library.......

@JP Smith. About the MMO (at least the anode I have, which is an anti corrosion anode. I think it consists of Ir Oxides on the outside), I attempted to make Perchlorate with it some time ago. No Perchlorate formed at all. (120mA per square cm, 0.5 liter cell with 250g Na Chlorate in it. Ran cell for 25 days
But conditions are different in the cell with the diaphram, so who knows. Also with different MMO's things will be different too.

Dann2
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[*] posted on 18-3-2008 at 05:39


Dann2, what happened with the MMO during the 25 day test, it just made ozone or something? Did it deteriorate over that time?
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[*] posted on 18-3-2008 at 13:43


Instead of trying to come up with some cell configuration scheme trying indirectly to make an unsuitable anode coating material work , a coating which has already shown it doesn't have the catalytic selectivity and activity for making perchlorate .......
wouldn't it seem more likely to produce positive results to followup on the reported ways of toughening anode coatings which have already been shown to produce perchlorate , but which only need improvement in their
service life ?

Xenoid showed that cobalt and manganese dioxide makes perchlorate . That agrees with the literature .

dann2 showed that antimony and tin oxide does *not*
make perchlorate . That also agrees with the literature .

Which scheme of the two is more likely to be improved
by any sort of tweaks or fine tuning ?

The cobalt spinel is evidently the catalytic component
which accounted for Xenoids results . That cobalt spinel
being used substantially in the place of antimony in dann2's scheme would probably produce perchlorate as well . The problem with the antimony appears to be
a selectivity for *oxygen* along with high oxygen overvoltage , the problem being the selectivity should
be for *chlorine* with a high oxygen overvoltage .....
so the ATO is not going to work regardless of the cell design , it's just going to sit there happily making plenty of oxygen and zero perchlorate .

I believe the coatings which work for perchlorate are those which have the ability to form conductive peroxides
or peracids on the surface of the anode which are active
intermediates , being themselves reduced in the handoff
of their oxygen to the chlorate , and being regenerated
electrolytically again , continuously recycled to the peroxidized state . So any of the coatings , or dopants
which will be useful are those which are capable of achieving a peroxidized form , however transiently stable ,
and then dropping back down to a more reduced form to be recycled again by nascent oxygen from the electrolysis
of water . But a second parameter *has* to be a preferential evolution of chlorine from brine . Both
qualifiers *must* apply or you simply haven't got a perchlorate anode .......in *any* cell design .

With regards to carbon anodes , there is IIRC an unstable
"graphitic acid" which is possibly reponsible as a catalytic intermediate and might make it possible to make perchlorate
using a carbon anode , but the erosion would likely be severe because the stuff continually sloughs off instead of
remaining adherent to the anode substrate as a permanent catalytic coating . It erodes into fresh carbon as the process
goes along , leaving a mud of spent carbon in its wake which
is not regenerated .

[Edited on 18-3-2008 by Rosco Bodine]
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[*] posted on 18-3-2008 at 14:24


Hello,

@JP

The MMO just sat there with bubbles coming off of it. I presume they were Oxygen. I never noticed an Ozone smell, though I never actually put my nose into/over the cell.
The coating did deteriorate on the upper surfaces of the Anode. The black layer (the outside layer) came off or you could easily rub it off after the run. The anode was still producing bubbles in all areas so it appears that the outside (black) layer is not the only layer. The substrate is Ti BTW.
Pics of anode here (Chlorate cell).
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
Page above this one here:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
The black coating got a bit damaged in a Chlorate cell too when anode was used to make Chlorate but all areas of the anode seemed to continue to work OK (bubbles formed on surface).
The Anode was sent to me about 9 years ago when I was in the USA. I presume it is a corrosion control anode, the same or similar to 'Lida' wire. I only got around to setting it up some months ago. It is a great Chlorate maker, clean and high CE.

Dann2
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[*] posted on 19-3-2008 at 16:44


(Clipped from Rosco's post back about page 4)
What would be the optimum composition for the mixture
I am not sure but my *guess* about a good starting point
would be precursors in mixture resulting in proportions
of the oxides based on the metals on a molar basis
Mn 73% Sn 24% Bi 3% .....up to a mixture having about double that amount of Sn and Bi in the same proportions ,
such as Mn 46% Sn 48% Bi 6% . There is something of a contradiction between the two Shamrock patents here and it may be that the final coating would be better having MnO2 as a relatively minor ingredient in the final coating which could be more like Sn 85% Bi 10% Mn 5% ,
or even a final coating having no Mn at all , such as
Sn 90% and Bi 10% .
(End clip)

Want to suggest a composition to try? I'm thinking of attempting a SnO2-BiO3-Co3O4-MnO2 coating soon. I got my SnCl4 and PbO also, packaged nicely, but they are just in tough ziplock bags, inside another (much less tough) bag, in a box of peanuts. Still, the price was good and I have my bag of SnCl4 gravel.

If I make the stannic nitrate, there's no reason I can't dope with my other nitrates. I already have dry Co and Mn nitrates. I have plenty (1lb) of BiO3 now as well.
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[*] posted on 19-3-2008 at 20:03


Quote:
Originally posted by tentacles
Want to suggest a composition to try? I'm thinking of attempting a SnO2-BiO3-Co3O4-MnO2 coating soon.


Okay I'll go out on a limb .

What I have been thinking about is a mixed nitrates derived mixed oxides of that similar configuration having a percentage basis expressed as the sintered oxides of SnO2 82% , MnO2 8% , Co3O4 5% , Bi2O3 5% , ....used as an interface coating as well as a build coating . If it doesn't work well as an initial interface coating , then what I would try next is to use *one coat* of straight Co3O4 as the interface coat baked , followed by *one coat* of plain tin oxide baked , and then proceed with build coatings of the above proportions . It may work better with the MnO2 omitted if porosity problems occur , in which case the SnO2 percentage would simply raise to 90% . It's sort of coin toss on whether that porosity will occur , my best guess is it won't be a problem .

There are more complicated alternating schemes that I have been thinking might be good but the above is about the simplest in the way of a mixed nitrates or mixed nitrates and chlorides precursor salts mixture which likely would be a sealing as well as being a working coating . This is just an educated guess however , based upon a collection of
references , and unproven hypotheses of my own , derived
from what I think it all means :P so there are no guarantees .
What I think is the SnO2 and Co3O4 and MnO2 will function as a tertiary solvent oxide system , something like fluxes for the Bi2O3 . This mixture is something expected to be more like a glass , a ceramic glaze than the more usual dopant filled tin oxide lattice polycrystalline layer ...
although it works the same way ....what I am theorizing
is that the polycrystalline structure from this mix will be something like a complex spinel structure itself , having
bi-electrode regions of amorphous glass mingled with definitely structured crystalline regions of varying composition. The whole surface should end up tiled with slightly differing composition adjacent tiles of nanometer dimension , some having crystallinity and some a having glass like character plates with fused boundaries like grout
between the tiles *if* my guess is correct .

This scheme possibly may be enhanced as alternating coats with the mixed valency stannic/stannous nitrates/chlorides
"dyers tin mordant" sort of composition described in that
Ordway paper . There is probably enough dopant in the alternating layers that diffusion would take care of any
doping for conductivity .

Quote:

I got my SnCl4 and PbO also, packaged nicely, but they are just in tough ziplock bags, inside another (much less tough) bag, in a box of peanuts. Still, the price was good and I have my bag of SnCl4 gravel.

If I make the stannic nitrate, there's no reason I can't dope with my other nitrates. I already have dry Co and Mn nitrates. I have plenty (1lb) of BiO3 now as well.


Yeah , I think the *stannic* nitrate , perhaps in some mixture
with stannic chloride , or some other entirely stannic composition may be required in order to prevent the dopant
salts from being reduced to their metals , as might occur
with stannous salts or mixed valency tin precursors . However there definitely are Pytlewski model mixed valency stannic oxide polymers , hydrosols , where the dopant is actually substituted in the complex monomer unit and does not precipitate , and is not reduced to the metal . So how the precursor is prepared to include the dopant is important where an intermediate is formed in the mixture . The sequence and technique in preparing the precursor mixtures
could become more complicated than simply dumping everything together and mixing , where mixed valency materials are involved .

There is a surplus of oxygen provided from the nitrate precursors which could be useful in the conversion of other precursors to the desired oxide , but compatability in a mixture that is entirely nitrates for example would be likely , absent the manifestation of some insoluble multiple salt which could complicate things . There's one way to find out for sure , try it and see what mixes okay :D

[Edited on 20-3-2008 by Rosco Bodine]
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[*] posted on 20-3-2008 at 08:52


This is going to make for an interesting precursor solution. To get 1 mol of Co3O4, I need 3 moles of Co(NO3)2, etc. I'm trying to get a handle on the math now...

Ok, here's what I came up with...

SnCl4-5H2O 7.05g
Co(NO3)2-6H2O 1.12g
Mn(NO3)2-6H2O 0.59g
Bi2O3 0.60g

I will be starting from these ingredients, reacting the Bi2O3 with HNO3 to make the bismuth nitrate in solution, and neutralizing the SnCl4 to make stannic hydroxide, which will be filtered and used to (mostly) neutralize the nitric acid solution.

Rosco, do you have a procedure for making the alpha stannic oxyhydroxide from SnCl4? I am also considering attempting this coating using the SnCl4 - it is worth a shot anyways.


[Edited on 20-3-2008 by tentacles]
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Rosco Bodine
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[*] posted on 20-3-2008 at 10:50


The math on the stoichiometry which relates back to the
precursor quantities , I haven't done yet . I'll check the figures later when I have time .

I don't hold much hope for the oxyhydroxide being useful directly as a coating , it would seem too disperse and having too much water content , that it would seem likely to dust rather than to adhere on baking .

From what I have seen of the old references in many places the stannic nitrate is described as the *neutral* nitrate of tin . The procedure is to just neutralize a solution of SnCl4 with ammonium hydroxide in no excess ,
and rinse by decantation the precipitated alpha stannic oxyhydroxide with water to free it from any adhering residue of byproduct NH4Cl . ( This rinsing is not essential IMO as any residual trace of NH4Cl is likely stabilizing as an impurity in the stannic nitrate to follow , so simply draining the precipitate is probably sufficient ) Order of addition may or may not matter . Most likely IMO , to the
alpha stannic oxyhydroxide as a paste in minimal H2O and *in the cold , and with cooling and stirring* is dropwise added HNO3 of medium strength to form the stannic nitrate .

I'm not sure how the pH compatabilities will work out
for Bi(NO3)3 and stannic nitrate , as there has to be a
high acidity for the Bi(NO3)3 to remain soluble , and that much excess of HNO3 might destabilize the stannic nitrate , causing metastannic acid to precipitate . This
is a place where I thought the Bi(NO3)3 addition product
with a polyol like glycerin , sorbitol , mannitol ect. , possibly ethylene glycol or erythritol ....may be useful in
mixture with the closer to neutral stannic nitrate , for
keeping eveything soluble without having to go too extremely acidic for the precursors mixture , which could
lead to problems with the stannic nitrate . There's nothing
in the literature I have found to clarify these details ,
so what to expect will happen , I can't tell you . BTW these
addition products of Bi(NO3)3 with polyols are *alcoholates*
according to a similar scheme as is gotten with mixing and refluxing chlorides precursors with butanol or other alcohols .
With Bi(NO3)3 evidently the alcoholate forms spontaneously
simply by dissolving the Bi(NO3)3 with the polyol where it resides in substitution for two hydroxyls , forming a soluble
alcoholate organometallic complex or chelate-like material .

The Bismuth doping might be accomplished via the formation of that Bi substituted monomer unit described by Pytlewski .
And the ammonium stannate / ammonium bismuthate sol
is another alternate possibility if the nitrates mixture proves
unworkable . There's a couple of other strategies also for
dealing with the Bismuth if it proves to be troublesome
getting a stable mixture . Glacial acetic acid inhibits precipitation of the nitrate , and acetone may be helpful
also as added solvent in a nitrates precursor mixture .

Anyway if one mixture scheme should prove unworkable , it's not a dead end because there's likely to be another mixture which will blend okay . There's several possible ways of getting the desired precursors in mixture which
should end up being the same composition after sintering .


[Edited on 20-3-2008 by Rosco Bodine]
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[*] posted on 20-3-2008 at 14:23


Well, I had to leave for work before I could really get down to it (which sucks).

BUT the SnCl4 doesn't seem to react with the mixed nitrates in ethanol solution. Or at least, there's no precipitate, bubbling, or any indication something is going down.

I did get a chance to try coating twice - the first time I just haphazardly dip n baked, and got a streaky coating. The streaks were very glassy, and highly conductive - low single digit ohms on my meter. The uncoated Ti streaks were virtually non conductive by comparison. I sanded, etched again and tried coating again, and it's a bit different for the second coat, I think I need to optimize the solution concentration or application. I did one by letting it dry completely and then baking it, that did help but there is a tendency for it to bubble in spots, making a sort of (BiMnCo)TO foam.

There was a *slight* excess of HNO3 in the solution - by my calcs, the Bi2O3 conversion needed .33ml of my HNO3 to dissolve, but that's a damn hard amount to dispense (no pipettes). So I probably sloshed about 2ml in there. I dissolved the Bi2O3 before adding the alcohol. ~100ml total volume for the whole solution, undried denatured alcohol.

I'll let you guys know if the solution works the same tommorow, or if it looks different tonight when I get home.

[Edited on 20-3-2008 by tentacles]
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[*] posted on 20-3-2008 at 16:06


The figures have been posted before but it's been awhile
and I forgot , will have to go back and check ...but there is
an optimum concentration for the precursors coating solution with regards to film formation and IIRC it is about 8% solids loading , expressed as final SnO2 basis . That works out to be a pretty concentrated mixture of precursor salts , and
some viscosity is desirable also , so if it is a bit syrupy ,
even better .

One of the described compositions in those
old writings about tin mordants IIRC regarded one of the tin nitrate mixtures which was syrupy , which is good :P ,
and which would gell suddenly when heated :D , which is
grrrrreat . Because if that behavior held true when the dopants are mixed with it , the gelling would tend to set
the coating with all the dopants distributed and trapped
in a dispersed state in that gell , where there would be no
tendency to separate and the film would not sag but would
keep an even thickness . An idea I had is to chuck the anode rod in a slow speed stir motor like a zero max ,
( I have one ) and dip it , then rotate it horizontally at slow speed like a barbecue rotissierie while manually sweeping
it with gentle heating from the heat gun , to gell and dry
the coating pretty good , before the sintering bake . That
should set the coating at a very even thickness which shouldn't creep during sintering .

[Edited on 20-3-2008 by Rosco Bodine]
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[*] posted on 21-3-2008 at 14:04


I can at least report a few things: the solution does not seem to have changed in the ~28 hours since I mixed it up. I wonder if the HNO3 keeps the SnCl4 oxidized, or all the nitrate ions, or god only knows?

I have one anode that is 6 coats of BMC-TO, and the other one that didn't coat so nicely, I re-etched, and put 1 coat of cobalt down, and I will put 6-7 coats of BMC-TO over top. This way I could at least avoid passivating parts of the Ti with a bad first coat.
The coating is really quite pretty, thin coats are a light yellowish, oily looking, glossy coat. I will try to take some pics later.

EDIT: I got a bit worried when I could no longer get conductivity with my voltmeter, but a quick test in weak (~150g/2L) NaCl solution shows some results, although not very much current seems to be flowing (I didn't hook my voltmeter up, just my 0-50A inline meter).

PICS:
http://www.apcforum.net/files/DSCN7238.JPG
http://www.apcforum.net/files/DSCN7236.JPG

If I had any more 6-32 screws, I would setup a quick test cell with some KCLO3. Or, if any damned hardware stores were open today!

[Edited on 21-3-2008 by tentacles]
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[*] posted on 21-3-2008 at 15:07


Quote:
Originally posted by tentacles
I can at least report a few things: the solution does not seem to have changed in the ~28 hours since I mixed it up. I wonder if the HNO3 keeps the SnCl4 oxidized, or all the nitrate ions, or god only knows?

You have no worries about the SnCl4 being stable or interacting with other precursors . Unless you put a lower valency or a basic material in a relatively neutral solution
of SnCl4 it is going to stay SnCl4 , however that same stability is something that works against its desirability as a precursor , plus its oxygen deficiency , as it is a longer way
from being SnO2 and requires higher temperature for its pyrolysis than does the nitrate .
So you should probably
raise your sintering temperature considerably using the
SnCl4 .....maybe to even 550C . It could be that the
oxygen surplus of the dopant nitrates has considerably lowered the development temperature for the SnO2 , compared with what temp would be needed if only chloride precursors were being used .
Quote:

I have one anode that is 6 coats of BMC-TO, and the other one that didn't coat so nicely, I re-etched, and put 1 coat of cobalt down, and I will put 6-7 coats of BMC-TO over top. This way I could at least avoid passivating parts of the Ti with a bad first coat.

Have you tried evaporating the precursor solution down to
achieve that concentration which results in about 8% as SnO2 basis , for the SnO2 precursor concentration ?
Quote:

The coating is really quite pretty, thin coats are a light yellowish, oily looking, glossy coat. I will try to take some pics later.

The color is something I really couldn't guess , or even if it might be clear actually , but I was thinking it could be blue
to brown . That it is shiny tracks with guess about the
tertiary solvent property of the SnO2/MnO2/Co3O4 fluxing the Bi2O3 into a glass . Because the dopant percentages
for MnO2/Co3O4/Bi2O3 at 20% would already be double
what would be expected to rupture the usual SnO2 lattice
and result in an opaque coating , even a black coating ,
unless everything was basically dissolved in solid solution ,
in particles so small that it is less than the wavelength of light :D , where usually what would be black is now lightly colored or clear :D This is great news and it means the
level of dopant saturation is intermediate and could be increased if wanted . The bismuth would be the dopant percentage to attempt increasing . The color would be expected to deepen and darken with increased doping and
it might shift color also , probably to a brown or coffee color .

The way you describe the shiny oily look of the coating it almost sounds like a lacquered gold anodizing sort of appearance . That sounds like it probably has good adhesion and clarity , like it's definitely a dense coating .


[Edited on 21-3-2008 by Rosco Bodine]
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[*] posted on 21-3-2008 at 15:08


I think maybe you put too much BMTO on and your conductivity is down. Since it forms such a hard varnished look, I would build up Co3O4 and Ni2O3 layers then one perhaps 2 coatings of your sealant. Try that and compare conductivity.



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[*] posted on 21-3-2008 at 15:20


chloric: that could be... I made up a quick and dirty cell...

The 6 coat BMCTO delaminated after about... 1 minute. Current draw (~8v) was 2A at the start, and very quickly tapered down to 900mA, then dwindled. At that time I noticed the flakes swirling around, took the anode out, and proceeded to wipe off over half the coating. Not good!

I have #2 in there now, with the Co3O4 undercoat, it already looks to be doing better. This one started at about 600mA and is holding steady around 340mA.

Anode surface area (immersed) is about.. 40cm^2. Current density is actually super low!

One *very* strange thing.. Almost nothing is evolved at the cathodes! A few bubbles, but *nothing* compared to dunking in one of the MnO2 anodes at a comparable current. The scent coming off the cell is neutral, no chlorine smell. Looks like BMCTO needs tweaking, at the least!

edit: And this was just a chlorate cell! I have serious doubts it would fare better in a perchlorate cell.

more edit: If it matters, the crud I wiped off is a dark blueish color.

[Edited on 21-3-2008 by tentacles]
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[*] posted on 21-3-2008 at 15:26


That sounds like it never got hot enough to sinter
the coating .

That first image you posted , I enlarged and looked closer
at the coating which has an uneven appearance , like
it segregated on baking . Those greener areas are contrasted with yellowish areas , where the mix with the
blue probably from the cobalt is unevenly distributed .

Maybe the differences in the precursors decompositon temps is causing the problem . Your Co and Mn and Bi nitrates are decomposing first , before the SnCl4 , and wicking it to their islands . If a nitrates derived stannic oxide precursor was being used , it would decompose first and that problem shouldn't occur .

[Edited on 21-3-2008 by Rosco Bodine]
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tentacles
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[*] posted on 21-3-2008 at 15:34


I'll rework that one at a higher temp, then.

#2 is doing a bit better, but it's dwindling down - it's already down to ~150mA.

Rosco: won't the MnO2 go gamma if I get it too hot? Or will that not be a problem in this configuration?

[Edited on 21-3-2008 by tentacles]
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Rosco Bodine
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[*] posted on 21-3-2008 at 15:50


See my edit above , I think the SnCl4 is the culprit .

The Mn and Co and Bi should be so dispersed in solution
that their crystalline habit is moot .

[Edited on 21-3-2008 by Rosco Bodine]
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[*] posted on 21-3-2008 at 16:41


I was a bit concerned about the difference in decomposition temp as well, but it was worth a shot. Maybe Sunday I will have time to whip up some stannic nitrate and try with that.
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Rosco Bodine
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[*] posted on 21-3-2008 at 18:23


Yeah the whole idea of using the less stable stannic nitrate SnO2 precursor is to get the hydrated SnO2 matrix formation to *precede* the dopant decomposition so all the dopant is entrapped in a dispersed state . Then the dehydration and dopant pyrolysis proceeds and the SnO2 lattice collapses locking everything in place on sintering .

Having the reaction order reversed would royally screw up that whole plan :P

The only way to use the SnCl4 in a dip coating is probably to convert it to an alcoholate which has less stability than the SnCl4 itself . IIRC the only way that straight SnCl4 alone was ever useful was as a spray pyrolysis precursor .
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[*] posted on 21-3-2008 at 19:03


Well, it *is* behaving much differently with the coating I just put on (and killed my heatgun... AGAIN). The color after sintering at ~540C was a yellow-blue-grey. Unfortunately, the last coat didn't get hot enough - I only took it to 460C. So my dumb ass decides to try finishing er off with my torch (hell, why not?) and I pretty well hosed the whole job.

I'll get another replacement heatgun tommorow.. I have GOT to remember, don't restrict the flow on the low setting! Both times, that's what killed the piece of crap.

I put it in the cell anyways, and I am getting chlorine evolution, and quite a lot better current. I don't think this one will last, but given the circumstances...

[Edited on 21-3-2008 by tentacles]
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[*] posted on 21-3-2008 at 19:54


Tell me what precursors you have and I will
do / double check the math on the stoichiometry .

Is it the same ones as you listed above ?
The Mn(NO3)2 you show should be a tetrahydrate ,
not a hexahydrate .
If you are working from alternate precursors like
carbonates , ect. , tell me as that may simplify things .
Do you have ammonium hydroxide , nitric acid , what strengths ?
Do you have any glycerin ?

[Edited on 21-3-2008 by Rosco Bodine]
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