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jpsmith123
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Cobalt Oxide Anodes
As per Xenoid's suggestion...
And I'll open the discussion with this:
The electrodeposition of cobalt oxide doesn't seem to be working very well, for both Dann2 and for me. If my last attempt fails, I think I'm going to
give up on this method altogether and try something else.
The "something else" I'd like to try first is something similar to the following procedure specified in one of Beer's patents (basically with the
ruthenium oxide replaced with cobalt oxide).
"Niobium was degreased and subsequently provided with an oxide coating of a thickness of at least 1 micron. This can be effected either
electrolytically or thermally.
Subsequently a paste was prepared of:
10 cc. ethanol
1 g. ruthenium oxide
4 g. titanium oxide
This mixture was intimately admixed, heated, sintered, comminuted, and again mixed with 10 cc. ethanol. The
resulting paste was applied to the oxidized niobium in a thin layer, and subsequently heated at a temperature of
450-700" C. This treatment was repeated until at least 10 g. of the desired mixture per m^2 was present on the
surface. A niobium plate thus treated is excellently suitable for the electrolysis of electrolytes."
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Rosco Bodine
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Circling back five months into the PbO2 thread seeking convergence huh ?  Long
live the marathon blog 
The cobalt spinel portion of the "ceramic bronze" mixture will still be what is forming the boundary layer , the conductive interface with the
titanium substrate . The TiO2 will simply function as a dopable thixotropic thickener for the cobalt .
One of the earliest Co related patents US4115239 that I looked at used something similar as a build coating , but IIRC the interface on the Ti was
still a direct application of cobalt . See example 2 .
previous attachment:
US4115239 Baked Co(NO3)2 Direct Coated Titanium anode.pdf (65.57 KiB)
http://www.sciencemadness.org/talk/viewthread.php?action=att...
Many of the Dow patents related to the spinel directly
formed on the Ti as the interface formed from baking .
It can be used on top of DTO , and can possibly be used underneath it as well , but that is not established yet
AFAIK .
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Xenoid
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Thanks jp - see the "more on PbO electrodes" thread for the initial discussion of cobalt oxide anodes.
Here's an image of my simple 200ml chlorate cell running with the single cobalt oxide spinel coat over Ti anode. After 7 hours it is still stable,
it's running in constant current mode and the voltage topped out at 4.0 Volts after a couple of hours. The black slime around the top looks worse than
it really is, it's spread out by the bubbles and the meniscus. I wish I'd taken a photo of the anode before putting it in the cell, but too late now,
I'm not going to touch it...
Edit: That SS canister in the background is completely separate and is not wired to the cathode of the chlorate cell, it just looks like it is because
of the camera angle!
Regards, Xenoid
[Edited on 2-12-2007 by Xenoid]
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dann2
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Howdy Folks,
Good idea.
Wonder what Janger would make of the new thread!
Good and bad news.
My Cobalt Oxide (plated) on DTO'ed Ti has made Perchlorate.  I got a
purple color with Methylene blue test.
Since DTO does not seem to be capable of making Chlorate it is surly the Co Oxide.
The bad news is that all the Co Oxide has stripped off. It lasted a few hours. No good, it was only a thin coat but a thicker (8 hours plating) would
not last much longer.
The DTO is still soldiering on.
The more you think about the baking (as opposed to plating) the simpler you reasize it is. Once you have an oven (a shambolic one like I have is
sufficient) your in business.
The attached file is from Kirk Othmer, may be of some use.
Dann2
Attachment: cobalt.pdf (162kB)
This file has been downloaded 2841 times
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jpsmith123
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I give up on the electrodeposition idea.
Well let's see, three of us tried it...to no avail. I tried putting it over graphite, platinum, TiH2, TiO3 and Co, and it readily came off, every
time.
So I don't know if patent #3399966 is just total BS, or perhaps the inventors deliberately left out some critically important detail; regardless, I
can't see wasting any more time on trying to electrodeposit the stuff.
One last, related idea, which I may yet try, is to electrodeposit a layer of cobalt over Ti, and then try to convert it to Co3O4 by heating it in air
with a heat gun.
(This is as per the paper I uploaded a while back regarding the Co3O4 field emission study where the authors stated that, after heating cobalt foil,
the surface oxidized and the oxidized layer "remained tightly connected with the Co substrate").
@Dann2: It's good to know that it is capable of making perchlorate. Maybe baking it on will turn out to be the answer. I'd like to see you or Xenoid
or someone with access to some kind of furnace mix up a slurry of oxides or at least add some TiO2 powder to the Co Nitrate or Acetate solution, and
then paint and bake.
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Rosco Bodine
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The Dow Patents
What I have gotten as the gist of the Dow patents is that
cobalt spinel has the similar and perhaps even better solvent property for other oxides , as does Tin Oxide ,
but additionally forms distinct bimetal or polymetal substituted spinels which are distinct molecular compounds
arising from the solid solutions . These substituted or expanded spinels also have solvent and doping properties ,
inherited from the cobalt spinel on which they are based .
Further , in regards to those solid solutions where a distinct molecular substituted spinel does not form , the cobalt spinel functions as a dopant ,
in much the same way as antimony dopes tin oxide , so does cobalt spinel dope tin oxide , only in that combination , both the cobalt spinel and the
tin oxide have solvent properties towards each other . The solvent effect of the cobalt spinel is probably higher than the tin oxide , so the easy
solid solution between the two is likelier than is the use of antimony with tin oxide . In fact in a competition for the solubility as a dopant of
tin oxide , there is some indication that cobalt spinel may be superior to antimony . Cobalt spinel is something of an economical
substitute in many respects for Ruthenium .
See US4369105 attached
Charts show a nearly flat conductivity response across a fairly wide baking temperature range for the doping of a
plain tin oxide interface layer , which picks up its doping from
a subsequently applied and baked layer of cobalt spinel .
However , if the interface layer of tin oxide is doped with antimony content during the initial baking , and the antimony
doped tin oxide is then overcoated with a baked cobalt spinel , the conductivity fluctuates with the baking temperature range , some indication that
the cobalt spinel
is trying to swap places with the antimony in the tin oxide
later or otherwise modify the composition of that existing interface layer . So if an antimony dopant is to be used with
the tin oxide for purely physical reasons , a much reduced amount of it is needed in the presence of cobalt spinel .
And not only could the cobalt spinel be applied as a subsequent coating over the tin oxide layer , but it would seem likely it could be mixed with the
tin oxide as an intimate dopant from the outset .
With regards to the formation of ceramic bronzes as a
filler for the cobalt spinel mixtures , these bronzes may
be included as " modifier oxides " whose precursors are
blended with the cobalt nitrate so they form in situ .
Zirconium nitrate was the "filler" oxide precursor found to work best , but others may be used . Bismuth would seem to be a good modifier oxide to
include in the final coatings as a small percentage , for the benefit of its catalytic effect in perchlorate production .
Related patents are
US4061549 US4428805 US4366042 US4368110
[Edited on 3-12-2007 by Rosco Bodine]
Attachment: US4369105 Substituted_cobalt_oxide_spinels on Tin Oxide coated Titanium Substrate.pdf (157kB)
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Xenoid
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Well, the anode has made it through the night, its now been running for 19 hours. The voltage has risen again slightly to 4.1 volts however. Its a bit
hard to know if this is an accellerating trend or a levelling (plateauing(sp?) out) hopefully the latter. It took a longer time to get from 4.0 to 4.1
volts than the other incremental shifts. Not counting the actual etching and baking times, this anode probably required about 5 mins. of my time to
make.
I wonder if having pure Co(NO3)2 is any particular advantage, since just about any element seems to be able to substitute in that spinel structure. I
see Ca is listed for the "M" position. Maybe having cobalt nitrate contaminated with CaSO4 is an advantage! Although I recall from the MnO2 coating
exercise, SO4-- is an undesirable addition.
BTW what is the longest time any of you have got a Ti anode to run.
Regards, Xenoid
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jpsmith123
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I'm glad to hear that it's still running.
If you make another, I'd like to suggest adding some TiO2 to the solution before painting it on the titanium (see patent #4222842, example #2; 1g
Co(NO3)2, 1cc H2O, and 1cc isopropyl alcohol + TiO2 in suspension).
My longest running anode ran for about two hours until I stopped and wiped it...and that's when the coating came off like slime. It actually didn't
passivate.
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Rosco Bodine
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IIRC the sulfate was a peculiar contaminant antagonist with regards to beta MnO2 formation . I'm not sure it
has the same deleterious effect in other coatings .
Sulfamate salts have not been reported test results
but they have been mentioned as possibly useful .
I have been dubious about any of the cold processes
alone as being sufficient for a durable interface with
Ti . I have generally regarded the baking schemes as probably unavoidable to develop the solid solutions
as a vitreous layer even for those materials which may be deposited in the cold . Heating is required for the reactions involved to form these
coating materials which
are a sort of "fired glaze" process similar to the production
of enamelware , the glaze in this case being electrically conductive to the metal substrate below .
I still think these coatings could be developed over a burner , especially on the larger diameter solid rods ,
held horizontally over the burner and rotated for even heating . sheet Lead and sheet Zinc strips wrapped around the rod and twist tied snugly with
wire could be used as temperature markers by observing their melting points . A particular setting for the gas flow could be found where the heating
is right in the range where it is needed .
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dann2
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Hello,
About the small increase in anode voltage. It may be just an accumulation of bubbles. Try taking the anode out, wipeing the bubbles off and see if V
drops again. I noticed this with the DTO on Ti strips I was testing.
Regarding how long I have got an anode to run I cannot answer. The DTO'ed Ti has been going now for about 70 hours. It's not really an anode as such.
Going back to what kick started myself with Ti substrate LD anodes.
http://www.sciencemadness.org/talk/viewthread.php?tid=1425&a...
This guy has been running them for a considerable time.
There is a discription of the anode way up the 'more on PbO2 anode' thread.
Dann2
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Rosco Bodine
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| Quote: | Originally posted by Xenoid
I wonder if having pure Co(NO3)2 is any particular advantage, since just about any element seems to be able to substitute in that spinel structure. I
see Ca is listed for the "M" position. Maybe having cobalt nitrate contaminated with CaSO4 is an advantage! Although I recall from the MnO2 coating
exercise, SO4-- is an undesirable addition.
Regards, Xenoid |
Thinking more about this , the sulfates would probably be a bad thing with the cobalt spinels , simply because of their elevated decomposition
temperature being above what is healthy for spinels .
This is probably why the nitrates are favored precursors and really this might apply for the tin oxide precursor as well if it is applied mixed with a
cobalt spinel . Something other than a chloride , something which fully decomposes at a lower temperature would possibly be better .
Very possibly cobalt spinel doped SnO2
could be as good a dopant for SnO2 as fluoride . It would probably be highly colored though as opposed to glass clear .
One advantage of a highly colored coating is you can see where it is providing good coverage by the tint .
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jpsmith123
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So Dann2 you're done experimenting with cobalt? You're not going to try any kind of baked on coating?
(BTW how do you know Alembic's LD anodes are not having problems like everyone else's?)
[Edited on by jpsmith123]
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Xenoid
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Hmmm.. over 24 hours now, the voltage is 4.2 volts. When I examined the anode (about 10 hours ago, there was a small lenticular area which was bare.
This has now doubled in size. The important thing about this however is that it "grades" out at the edges and the coating is not lifting off in
flakes. It looks like it was an especially thin area and it is just "wearing away", it even looks a bit like a brush stroke, where it went on too
thinly.... he says hopefully!
I think my next move will be to try and purify the cobalt nitrate, at least then I'll be working from a "known" point. I'm wondering if the organic
salts of cobalt would work as well as the nitrate, eg cobalt acetate, tartarate, oxalate, citrate. They would be very easy to prepare pure from
"household" chemicals and cobalt carbonate.
I would also like to compare different concentrations of cobalt nitrate for coating, and the difference, 1, 2, 3 etc coats makes. For example there is
probably a huge difference in reliability going from just one coat to two and remember the anode I have produced only has one coat!
Also the hydriding should be checked out, to see if this improves the bonding.
There are heaps of possibilities to try and it is a huge undertaking, it would be best to get the "basics" out of the way before trying to modify the
cobalt spinel in any way! Well thats my feeling, anyway!
Regards, Xenoid
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Rosco Bodine
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Of those alternate cobalt salts I would say the oxalate
would be most interesting and perhaps even having a bit
of free oxalic acid maybe a couple of percent , all finely powdered , mixed with the cobalt nitrate as a thickener .
I still think the wet sanding of a freshly etched or hydrided
rod with some abrasive mixed in with the cobalt salt(s) and some glycerin or glycol might produce a sort of
Cobaltating effect similar to chromating . A bit of phosphoric acid , for example Ospho might be an additive to this Cobalto-Zud concoction .
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jpsmith123
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If you can heat to about 300 degrees C, the acetate should work nicely, as it is highly soluble in water and ethanol (exactly how soluble I don't
know, as I can't find and published data).
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Rosco Bodine
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I was thinking that the oxalic acid would by etching bring up some titanium oxide bronzing as a modifying oxide ,
somewhat emulating that Beer patent mixture . The titanium oxalate would decompose to the oxide during baking and simulataneously be doped by the
cobalt .
Might have to bake a bit on the hot side to insure
complete decomposition of the oxalate , or maybe just bake it five minutes longer .
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dann2
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Hello,
| Quote: | Originally posted by jpsmith123
So Dann2 you're done experimenting with cobalt? You're not going to try any kind of baked on coating?
(BTW how do you know Alembic's LD anodes are not having problems like everyone else's?)
[Edited on by jpsmith123] |
From page 8 (for me anyways) of 'More on PbO2 anodes' thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=2465&a...
__Quote__________________________________________-
That specific anode was only used for two batches of perchlorate, starting from NaClO3, which means that is has seen about 200 hours of use at a
current of 35-40 A. It still looks pretty much exactly the same. I have made other anodes (using the same process) that I've used in chlorate cells
for hundreds of hours with no visible signs of wear.
______________________________________________
Since the guy does not write patents I am inclined to believe him. He is a guy
who I communicated with many moons ago about LD anode. He had (the only person I ever knew) some homemade Graphite Substrate LD Anodes that were long
lasting and were a success. Interesting to note that even he moved from Graphite to Ti.
I do intend to hopefully do some Cobalt baking. Have no nitrate and may take a trip to ceramics store to purchase some Co Carbontat or make some from
Co SO4 + CaCl2.
Right now I am still bogged down in DTO stuff + I want to wheel out the LD tank.
Regarding getting Perchlorate with Co Oxide I am not now 100% sure if it was the Co Oxide or DTO that has made the Perchlorate. I have been running
the same cell with a DTO Anode in it (just testing the DTO anode) and the Perchlorate concentration is rising (as seen by a drop of Methylene blue.
DTO does not appear to make Chlorate (or at least it is very bad at it, as a chlorate cell (300ml) that I have ran for 50 hours at 0.5amps will not
give a ppt of K Chlorate when some K Chloride is added). Yet it appears to make Perchlorate. It may be making very little Perchlorate though as the
Methylene blue test is very sensetive.
Dann2
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Rosco Bodine
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combining technologies
| Quote: | Originally posted by jpsmith123
Well let's see, three of us tried it...to no avail. I tried putting it over graphite, platinum, TiH2, TiO3 and Co, and it readily came off, every
time.
So I don't know if patent #3399966 is just total BS, or perhaps the inventors deliberately left out some critically important detail; regardless, I
can't see wasting any more time on trying to electrodeposit the stuff.
One last, related idea, which I may yet try, is to electrodeposit a layer of cobalt over Ti, and then try to convert it to Co3O4 by heating it in air
with a heat gun.
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There's a variation on the theme which hasn't been tried
and very well may work .
I refer to US6228241 attached
Suppose we don't hydride , but simply etch with oxalic acid
and rinse off with distilled water . A thin but pore filled
passivation layer begins to form on the Ti immediately . Now suppose that this sample of Ti is then made the cathode for a brief time in the cobalt
nitrate electrolyte . Where is the first place that atoms of cobalt metal are going to deposit but at the most conducting spots , which just happens
to be at the bottom of those pores in the TiO2 layer that is growing .
The little deposits of Co metal will immediately stop the further growth of that virgin TiO2 or actually Ti mixed oxide
which resides at the bottom of those pores . And this doesn't take very long either , a few seconds to a few minutes , no longer , creates those
cobalt metal plated
pore bottoms .
Now the current is reversed , and the process of US3399966
is carried out . When the current is reversed the mesa of TiO2 begins to grow in thickness under the anodic oxidation ,
but it is also behaving as a reverse biased diode whose
valve metal behavior makes it conduct poorly from the start
and even more poorly as time passes and its thickness increases . But happily nearby down at the bottom of pores
is some freshly deposited cobalt metal that is conducting just fine in the anodic direction , and filling up that pore
with a growing column of electrodeposited cobalt suboxide . The rate at which that column of cobalt suboxide grows in height is faster than the rate
at which the mesa of TiO2 is growing , so in time the column of cobalt suboxide reaches the surface and then spreads across the mesa blanketing the
whole surface into which it is keyed with all those filled pores .
At this point we remove the sample of Ti , and let it soak
in a heated bath of saturated Co nitrate for awhile , and then bake it . This strategy should produce a very adherent and well doped coating . The
tenacious habit of the TiO2 itself as well as the porosity of the TiO2 layer is exploited , as well as the electrical properties . This might work
very well since it exploits the natural behavior and properties of the materials .
You could come back over the top of this with a vitreous
SnO2 and Co3O4 combination . And it might be good to go
at that point as a finished anode . Looks good on paper
and in theory to me . And I haven't seen such a process
described anywhere .
BTW , Dow and BASF are the two largest chemical technology
corporations on planet earth . And that technology involving
the pores and mesas is compliments of NASA , who occasionally think outside the box . Putting these three technologies together makes sense . No
guarantee that
Ti will follow the model of Al , but they are both valve metals ,
and they both have porous oxide coatings , so there's a very good chance it will work .
[Edited on 4-12-2007 by Rosco Bodine]
Attachment: US6228241 Electrically_conductive_porous_anodized_aluminu.pdf (87kB)
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jpsmith123
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Dann2 I went back and read that part of the thread, and you're right, he does sound legitimate.
However, making a PbO2 anode using his process is not something I would ever want to attempt.
I am still hoping that cobalt oxide can be used in a very thin coating...just like Beer's MMO but with the noble metal oxide replaced by cobalt oxide.
I bought a cheapo heat gun yesterday so I will soon be able to experiment with small-scale baked on coatings myself.
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dann2
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Hello,
Making the LD Anode on Ti with DTO undercoat is probable more simple that this thread would have you believe. I have done a hugh amount of tooing and
frowing mainly because I was trying to avoid using SnCl4:5H2O (out of a jar) as it is not available to me ( not OTC either), but I managed to get
500grams.
Once the DOT'ing is done it's (hopefully) just plain old Lead Nitrate plating bath(which is a PITA I will admit).
If Cobalt turnes out to be good at making Perchlorate(and Chlorate), fairly long lasting and farily easy to make than LD will be confined to the 'good
old days'.
Dann2
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Rosco Bodine
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All of the indications are that the Co based spinels and solid solution oxides should be more forgiving mixtures ,
developing at lower temperatures , and having greater
chemical resistance , operating at better electrical efficiency , and cheaper to make than the next closest
thing which is precious metal oxide doping schemes .
Another thing that might be worth looking at with regards to lead free solders is that other alloys than the 95/5
might be workable with Co , as Sb isn't even really needed
and the other alloying metals may function simply as modifying oxides incorporable into an expanded cobalt spinel , serving as a dopant for the SnO2
on baking ,
perhaps to even better effect than would the Sb serve
in the case where an ATO was derived from 95/5 .
This could also get the difficultly soluble Sb completely out of the picture as any issue , along with its tendency to phase separation in the baked
SnO2 coatings .
But the real advantage which may be realized is that the
baked coatings may function as a finished working anode , requiring no PbO2 at all , and actually working at better efficiency than a PbO2 anode . So
the cobalt schemes are
very promising in that regards , and not just as a substrate preparation for PbO2 , but as a finished working anode .
The PbO2 could be reserved as a sort of plan B , which could
then be added if the Co coatings just don't hold up without it
as an overcoating .
[Edited on 4-12-2007 by Rosco Bodine]
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Xenoid
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Well guys! The cobalt oxide spinel coated "5 minute" anode has been running for 48 hours (2 days) now, at 1 Amp (~50mA/cm^2) the voltage has risen
slightly again, it's now 4.3 Volts. This is not surprising because it is starting to look the worse for wear!
Edit: Actually, now that nearly half the active coating has worn away, I guess it's running at closer to 100mA/cm^2.
I removed the anode, rinsed it, dried it with warm air and took the images seen below showing both sides. What is left of the cobalt oxide is still
well bonded, but smudges to produce an incredibly black smudge (like carbon black), this is sort of like a reactive top layer.
When I put it back in the cell, quite vigorous bubbles began to issue from the surface with no connections made - weird, this is strange stuff, highly
catalytic perhaps, able to split water into H2 and O2 maybe, with unlimited energy for all, but I digress...!
When connected up, and I set the current for 1 Amp the voltage has gone back up to 4.2 V and the cell is continuing as before, although there seem to
be more bubbles coming from the anode!
I am finding this is really interesting!
I've sort of purified some cobalt nitrate, and I intend to do a triple coat with a concentrated solution, to see how it goes!
Edit: I forgot to point out, that the electrolyte level is only a bit above half way, its below the area where the smudge marks are, and can just be
made out as a faint line with a colour change.
Regards, Xenoid
[Edited on 4-12-2007 by Xenoid]
[Edited on 4-12-2007 by Xenoid]
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Rosco Bodine
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Looks like a good early "proof of concept" experimental result . Anything which doesn't passivate immediately
or within a few minutes is moving in the right direction
Wonder what alternating coats of Co(NO3)2 and a low temp decomposing SnO2 precursor might do , with the Co being the first coat and the last , making
a sort of sandwich . Maybe ammonium stannate would do the trick
or any syrupy hydrosol form of the Sn . There is a tin nitrate and this could work also , mixed with the Co nitrate .
Tempil heat indicators might be very handy for the
heat curing process .
http://www.tempil.com/product_display.asp?form.findapp=206
http://www.tempil.com/company.htm
[Edited on 4-12-2007 by Rosco Bodine]
Attachment: Tempilaq.pdf (516kB)
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Xenoid
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I just went to have a look at my semi-purified Co nitrate solution, which I had left in the fridge, only to find that it has crystallised....
I've poured off most of the supernatant liquid and I will add a small quantity (a few mls) of water to these crystals to make up my next coating
solution. Only a small amount of water is needed because they just about dissolve in their own "water of crystallisation".
The image below shows about 20g of crystals of cobalt nitrate hexahydrate sitting in the bottom of a 100ml beaker, which is lying on its side.
To get this stuff to recrystallise requires having just the "right" concentration level before cooling in a fridge.
Edit: I forgot to mention that the Co nitrate solution is kind of interesting in that it's thermochromic (is that a word). When it's boiling it's a
intense purple, beetroot juice, K-permanganate colour but when it's cooled down to 0 oC or -10 oC it's more of a reddish colour like strawberry syrup.
Don't leave it lying around where there are little kids, they might drink it!
Regards, Xenoid
[Edited on 4-12-2007 by Xenoid]
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jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
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Mmmm...doesn't that look tasty! And to make it even better, I suggest adding some powdered sugar, er, make that TiO2.
Anyway, I'll be making up a concentrated Co Acetate solution tomorrow...hopefully my "Chicago Electric" heat gun is up to the job of thermally
decomposing it.
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