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Xenoid
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Well, I just popped it in a perchlorate cell and the OO must be low, because as I turned up the current, oxygen just started to be evolved at 3.1V and
.27A, this corresponds to a current density of only 13mA/cm^2.
In addition there is also the dreaded "hint of pink" permanganate. I'm crossing my fingers its just from a bit of unconverted Mn++, residual in the
anode.
I've pulled it out and I will make some Pb nitrate tomorrow and put a couple of doped MnO2 layers on top.
I don't want to put Co spinel on top, because its baking temperature (370 oC) is getting a bit high for the stability of beta MnO2, which I baked at
~310 oC.
The anode actually has an almost metallic, peacock-blue hue, there was no need to wipe between coats, as absolutely nothing came off!
BTW does anyone know why, in all these "baking" patents, ethanol, iso-propyl alcohol or combinations with water are used for the coating solutions.
What effect is this supposed to be adding!
Oh! and also BTW, the 4 coat anode is still running after 7 days, but current has dropped to 1.77 Amps. I might even get a batch of chlorate from
this....!
[Edited on 13-12-2007 by Xenoid]
[Edited on 13-12-2007 by Xenoid]
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Rosco Bodine
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I think the stability of the MnO2 should be okay higher like up to the same 370C. If you are using plain MnO2 as a coating , there is reportedly
benefit in using 10% of the carbonate with the nitrate . It improves the range of temperature over which the Mn nitrate smoothly decomposes to MnO2 .
See US3553087 . There is also some indication here that the yield from thermal decomposition is not 100% , so that may account for some of your pink
leachate . It may just be a tansient leaching of the residue of the small amount which did not decompose completely , which will stop
leaching pretty quick .
The color development is probably some bimetal spinel formation where some cobalt and manganese are actually combined . This is something you want to
occur , probably
with some Pb added also .
There are reports of baked MnO2 used alone which do not hold up at all . See US4180445 . This patent contains an
electrodeposition method for Delta MnO2 from MnCl2 which may be of interest to jpsmith123 .
[Edited on 14-12-2007 by Rosco Bodine]
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R.P.Wang
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ethanol, iso-propyl alcohol or n-butanoln is used for dissolve the salts(MnNO3, SnCl4, SbCl3 etc) and make them fine distributed on the substrates.the
n-butanoln is the best dispersant and solvent, however,MnNO3 only dissolved in ethanol.
Xenoid : congratulations for your first chlorate!
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R.P.Wang
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| Quote: | Originally posted by Rosco Bodine
It's just a convenient stable conductive interface material for preventing passivation of a Ti substrate .
Working anode coatings like Bi2O3/SnO2 or PbO2 ,
must be used to prevent erosion , and increase oxygen
overvoltage for perchlorate cells .
Potentially other complex spinels may be useful as working anode coatings .
[Edited on 13-12-2007 by Rosco Bodine] |
From my experience in lab, the best conductive interface material is SnO2+Sb2O3, sometime a MnO2 oxide is also add in it . Ti/SnO2+Sb/alfa-PbO2/PbO2
maybe the most practical anode use for perchlorate cells.
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Xenoid
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| Quote: | Originally posted by R.P.Wang
Xenoid : congratulations for your first chlorate! |
Thanks for the information on solvents!
The chlorate is not my first, but all the previous chlorate was produced with graphite rods. This is my first chlorate with a Ti anode... 
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dann2
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Hello,
I have used Ethanol, Iso-Proply, Methanol and a water Methanol for my DTO coatings because they are what I had.
The vast majority of patent examples for DTO use Buthanol. I have none.
Don't know about the MnO2.
Regarding O2 evolution on anode. It will vary as the Chlorate conc. goes down.
There is no general agreement regarding mechanisms amongs scientists AFAIK.
Mechanism depends on anode material, conc's, pH, bla bla.
I have papers about the mechanisms of Perchlrate formation at anodes. Will post.
Know little about it myself.
Dann2
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R.P.Wang
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| Quote: | Originally posted by dann2
Hello,
I have used Ethanol, Iso-Proply, Methanol and a water Methanol for my DTO coatings because they are what I had.
The vast majority of patent examples for DTO use Buthanol. I have none.
Don't know about the MnO2.
Regarding O2 evolution on anode. It will vary as the Chlorate conc. goes down.
There is no general agreement regarding mechanisms amongs scientists AFAIK.
Mechanism depends on anode material, conc's, pH, bla bla.
I have papers about the mechanisms of Perchlrate formation at anodes. Will post.
Know little about it myself.
Dann2 |
the Ethanol, Iso-Proply also work well if you don't have butanol.
About the preparation of perchlorate on an anode:
First the materials can stand strong acid. Must be stable!
Second the oxygen evolution potential on such anode materials must be high. It is better to oxidize the ClO3- to ClO4 before the oxygen evolution. So
I still believe the Ti/Co3O4 anode is not a good choice for perchlorate production. Eventhough they are stable in acid solution.
[Edited on 14-12-2007 by R.P.Wang]
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Rosco Bodine
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The use of alcohol can be for several reasons depending on the solid materials being dissolved or dispersed . It
is a reactive solvent leading to alcoholates as a dispersed phase ( a sol system ) in the alcohol when reacted with
some salts . In procedures where the mixture is refluxed ,
this can be not only for producing the alcoholate , but also
for azeotroping away the water contained in certain salts , so that a lower water content or anhydrous mixture
results . Some salts also have high solubility in the alcohol
and it is simply a solvent which dries more quickly from
a mixture of salts which otherwise may be inclined to attract more moisture from the air after coating , before baking , and the consistent thickness
of the film adversely affected during the exposure to air between coating and baking .
With regards to the Co3O4 alone and the electrode potential for ClO4 , that is probably correct and I have
expressed the same idea . However , the Co and
some other materials in mixture or compounded together
can raise the oxygen overpotential , and/or lower the
ClO4 potential by catalytic effect . Some of the bimetal
spinels of Cobalt may have the desired overvoltage .
This may also be true for certain tertiary spinels .
One of them which may do it , I don't know for sure ,
is the cobalt-nickel-manganese spinel .
Some of the perovskite materials might also have the
desired effect . Some of the stannates may be useful .
There is also the bi-electrode effect which can be involved
for certain mixtures .
And there is always PbO2 particularly with Bismuth and fluoride as ClO4 catalysts .
Anyway , the interface and substrate materials are
irrelevant to the matter of ClO4 production by the
working coating for the anode , so long as the undercoatings are chemically stable and conductive
materials , that is their purpose as a support for the
working coating which is specific for the desired product
of the electrolysis . Even for the case where the substrate is solid platinum , working coatings that are
useful for the desired product are applied over the platinum , because the platinum itself may have zero
ability to produce the desired product because of having
an overpotential that makes its selectivity wrong , so
it produces another product preferentially .
The substrate and interface layers simply serve as a
chemically compatable and conductive
"electrocatalyst support" for the working coating .
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Rosco Bodine
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| Quote: | Originally posted by R.P.Wang
| Quote: | Originally posted by Rosco Bodine
It's just a convenient stable conductive interface material for preventing passivation of a Ti substrate .
Working anode coatings like Bi2O3/SnO2 or PbO2 ,
must be used to prevent erosion , and increase oxygen
overvoltage for perchlorate cells .
Potentially other complex spinels may be useful as working anode coatings .
[Edited on 13-12-2007 by Rosco Bodine] |
From my experience in lab, the best conductive interface material is SnO2+Sb2O3, sometime a MnO2 oxide is also add in it . Ti/SnO2+Sb/alfa-PbO2/PbO2
maybe the most practical anode use for perchlorate cells. |
Yes we are all well aware of that particular layering scheme .
No news for us there .
Has your work ever inolved cobalt - nickel spinel at the Ti ,
as an added interface ? ( With everything else the same )
For example:
Ti/Co2NiO4/SnO2+Sb/alpha-PbO2/beta-PbO2
@ Xenoid , that "peacock blue" dust free material
and coating you have there may not quite be there yet
for ClO4 , but it just might happily make ClO3 till hell freezes ,
(if porosity isn't there) , so it might be fine for chlorate ,
I don't know . Anyway that color development is very interesting , because the single spinel is black and so is the
single MnO2 , and black plus black isn't blue , unless something *very interesting* has occurred like a
bimetal spinel of Mn and Co , even though you did not
mix the two precurors , a solid solution migration must have occurred from the underlying cobalt spinel layer , by diffusion
at high temperature , the two different layers merged and
reacted to form the bimetal spinel . And because the shamrock patent described the mixture of Mn and Co precursors as useful for two of the parts of
a ClO4 selective
mixture , then the bimetal spinel might be headed suffciently
in the right direction to at least make a good chlorate anode ,
even if it stops short of the ClO4 capability for lacking the third element . Anyway , it's a pretty color so even if nothing else it would be good
as a decorative finish
[Edited on 14-12-2007 by Rosco Bodine]
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dann2
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Hello Folks,
| Quote: | Originally posted by Rosco Bodine
| Quote: | Originally posted by R.P.Wang
From my experience in lab, the best conductive interface material is SnO2+Sb2O3, sometime a MnO2 oxide is also add in it . Ti/SnO2+Sb/alfa-PbO2/PbO2
maybe the most practical anode use for perchlorate cells. |
Yes we are all well aware of that particular layering scheme .
No news for us there .
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Indeed!
Thanks to Alembic (my hero  ), we are aware of it. Took a bit of hammering home though.
NONE of us in here has *actually* manufactured a working anode of this scheme yet though (apart from yourself R.P.). That's a very important point.
I am at the DTO stage only, currently running a DTO Anode in a Perchlorate cell.
Keep up the good work all.
Dann2
[Edited on 14-12-2007 by dann2]
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Xenoid
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@ Rosco
If I put a couple of extra coats of ??beta-MnO2 on to "Gertrude" which are doped with Pb and Co, how are these elements incorporated into the
beta-MnO2 structure. For example Pb nitrate decomposes into PbO (massicot) at low temperature (no fusing) which is slightly soluble (.002). It does
not form the desirable PbO2 unfortunately. 20% Pb nitrate is a large substitution, will it not form a separate phase!
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Rosco Bodine
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I'm not sure what the story is on the Pb , probably some goes into solid solution and whats exposed gets anodic
oxidized in situ . I suspect what they are doing is creating
a hodge podge mottled field of surface regions which have a bi-electrode effect between the islands of different
materials ....rather than some uniform composition .
This is probably one when idle , you don't even want to leave wet , much less open circuit , because of the
"mini-batteries" all across its surface .
[Edited on 14-12-2007 by Rosco Bodine]
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Xenoid
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4 - Coat Anode - Chlorate Cell
When I inspected the cell this morning, current had dropped to 1.67 Amps. There was a lot of salt build up on the cathode connection as this cell was
a bit (quick & dirty) and there was no provision for venting or corrosion protection.
I decided to dismantle it and clean the cathode connection. After I washed the salt off it didn't look too bad, so I cleaned it a little and put it
back together. The anode has lost about 20-30% of its black coating, revealing a golden yellowish film (is this the real interface) underneath. Most
of the black coating had been lost on the side of the rod closest to the cathode, understandably. So I rotated the anode, 180 degrees. After assembly,
the current is now back up to 1.76 Amps. This is a drop in current of only about 5% over 8 days.
@ Dann2 - How are your Co oxide coated anodes going?
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dann2
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Hello,
Firstly, regarding mini-batteries:
Looks like the simple way around that problem is to use the anode twentyfour, seven, 365
| Quote: | Originally posted by Xenoid
............
The anode has lost about 20-30% of its black coating, revealing a golden yellowish film (is this the real interface) underneath. Most of the black
coating had been lost on the side of the rod closest to the cathode, understandably. So I rotated the anode, 180 degrees. After assembly, the current
is now back up to 1.76 Amps. This is a drop in current of only about 5% over 8 days.
@ Dann2 - How are your Co oxide coated anodes going? |
I have seen the gold coating, (failed anode in Perk. cell) with naked eye and looked at it with microscope. I guessed at the time it was Co Metal
(bullshit??? probably). Is certainly looks like metal but Cobalt is not gold coloured but silver grey AFAIK.
I must confess I only got around to setting up my Co Oxide anodes this morning. They are going now for about 12 hours.
The anode have cathode on both sides. Two cells are in series with a PSU power supply + resistor. Chlorate cells.
Current density is higher on one anode as it is smaller.
316 and 150 approx mA per square cm.
Voltage accross cells similar @ 3.8 volts.
No problems to report yet.
Still have not set up the Li Perk. cell using DTO Anode 
Dann2
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Rosco Bodine
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@Xenoid
There may be a problem with having a cylinder form anode
horizontally oriented the way you describe because you can't get an even current density across the surface .
The high spot closest to the cathode gets "scorched"
in the noontime sun while the backside freezes to death at midnight  , and every
other point gets something
of an average value of current density in between the
two extremes . Much better would be to have a coaxial
arrangement of cathode rods maybe 6 or 8 , and put
the anode right in the center , so the current density
is more evenly distributed across the surface . Do that
and it should last way longer and operate way more efficiently .
[Edited on 14-12-2007 by Rosco Bodine]
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jpsmith123
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Dann2 the Co Oxide coated anodes you're referring to, are they baked on coatings or electrodeposited?
Also, what's underneath the Co oxide, is it one of your DTO coatings?
[Edited on by jpsmith123]
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Xenoid
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| Quote: | Originally posted by Rosco Bodine
The high spot closest to the cathode gets "scorched"
[Edited on 14-12-2007 by Rosco Bodine] |
Yeah! I realise this now Rosco! It actually makes a mockery of my current densities, they were probably closer to twice what I have reported!
When you are testing stuff it's so much easier to have a simple set up, anode one side cathode the other, you can see whats going on! I have some
cylindrical cathodes, I'll use them for more serious testing, if it gets to that stage!
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chloric1
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| Quote: | Originally posted by R.P.Wang
ethanol, iso-propyl alcohol or n-butanoln is used for dissolve the salts(MnNO3, SnCl4, SbCl3 etc) and make them fine distributed on the substrates.the
n-butanoln is the best dispersant and solvent, however,MnNO3 only dissolved in ethanol.
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Xenoid-I feel it has more to do with wetting capabilities of the alcohols. The same reason why you add isopropanol to a glass cleaning formula. With
water it acts as a co-solvent of sorts.
Fellow molecular manipulator
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dann2
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Hello,
| Quote: | Originally posted by jpsmith123
Dann2 the Co Oxide coated anodes you're referring to, are they baked on coatings or electrodeposited?
Also, what's underneath the Co oxide, is it one of your DTO coatings?
[Edited on by jpsmith123] |
The anodes I have just set up to test are baked on Co Oxide (from Nitrate). 7 coats onto bare Ti. The Ti sat in the open for about 14 hours after
etching if that will make a difference. (Does not seem to do so.)
My other Co Coating was plated. When put onto bare Ti it passivated as soon as it went into a cell. The one on DTO worked but was eroding from the
start. I would say the coating probable lasted 5 hours or so (guess). It continued to work with the DTO.
Other DTO in Perchlorae cell still going fine. 10 days is the run time for the cell (pumping in 200% of required theoretical current needed, 2.1 moles
cell) . It will be interesting to see how low the Chlorte level is. Will try to titrate with Fe Sulphate
Dann2
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Rosco Bodine
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Sherlock and Shamrock
| Quote: | Originally posted by Xenoid
@ Rosco
If I put a couple of extra coats of ??beta-MnO2 on to "Gertrude" which are doped with Pb and Co, how are these elements incorporated into the
beta-MnO2 structure. For example Pb nitrate decomposes into PbO (massicot) at low temperature (no fusing) which is slightly soluble (.002). It does
not form the desirable PbO2 unfortunately. 20% Pb nitrate is a large substitution, will it not form a separate phase! |
I have been looking more at the cryptically described coatings
of US4072586 , and with your observation concerning
the PbO in mind have been trying to gain better clarity on
the "undisclosed fact" hidden within the "patentese" language . This is like trying to break some wartime radio cypher , to translate the
generalities into what seems to be most likely specifics . To help solve the riddle of what components among those the "patentese" language
discloses as groups of materials from which to select , I am looking at some relevant data from a more definitive patent which reveals something about
co-solubility of other oxides ,
within SnO2 . It was a patent I posted a long time ago and
does contain relevant information specific to this sort of
coating chemistry , as applies to the coating itself , information from Corning which is a division of Dow . The
patent is US2564707 attached again here , because it is
significant and enlightening and *pertinent* to what we are doing if SnO2 containing coatings are involved .
The patent shows many ternary systems of oxides soluble
in SnO2 , possibly as their stannates . Anyway this gives
a listing of some of oxides of interest to us with regards
to the listed *perchlorate specific* catalytic oxides of US4072586 which are co-existent in the anode coating with
the MnO2 .
The language of the patent was ambiguous as to the scenario involving "modifier oxides" or as the patent said up to 20% oxides added to "stabilize"
the coating . The choice was from 3 different materials listed in and/or fashion to complicate things further . Among these metal oxide precursors ,
one very noteworthy to me because it so unusual was *tin nitrate* , and tin is mentioned again in the next group of catalytic oxides as well , but
cobalt is mentioned as being preferred .
Later in the US4072586 patent section describing the catalysts found useful for perchlorates , again a choice is described between 3 materials ,
arsenic , antimony , and bismuth . Perhaps not scientific but intuitively I think the
arsenic can be ruled out as being an unlikely candidate .
And that leaves antimony and bismuth as the perchlorate
catalysts . Continuing with the decryption of the patentese ,
I looked for what seemed most likely solubility for the plural components in consideration , and deduced that tin oxide
would most likely be the solvent oxide for the others .
The Corning ternary system solubility data makes it likely
that in addition to the MnO2 , there is SnO2 in order to
provide "solid solution bonding" for the other components
listed , including the MnO2 , the cobalt spinel , along with
antimony or bismuth as catalyst for perchlorate . The tin oxide is the thing which would bind together the other
materials ......whereas it is unlikely that the PbO would have such an effect . The stannates bonding seems far more
plausible than any plumbate , and the silicon "third choice"
has been ruled out because it is said in the patent to exhibit no overvoltage , which is something desired , for a perchlorate selective anode coating
.
The claims however in referencing the perchlorate selective
variant , calls up the anode configuration of claim#1 ,
which would seem to point to an anode having not the
maximum 20% SnO2 as a stabilizer ( which is claim#2 not #1 ) The problem there is that the 20% SnO2 would
almost certainly be required as the solvent for properly bonding the other materials , including the Sb and/or Bi
catalysts required for perchlorate selectivity . It is probable
that the confusion created by this duality is quite deliberate
on the part of the authors .
So , my sleuthing has brought a bit more understanding
of what is most likely required for the perchlorate anode
which they are deliberately not describing in its full particulars . I will later plug in some numbers for some
try and see proportions which seem to reside within the
percentage ranges specified by US4072586 , and see if
the predicted solubilities in SnO2 square with what is
known from the Corning patent . Hopefully from this
little effort at decryption of Diamond Shamrocks "patentese"
their secret proportions of specific components which they very deliberately aren't listing in plain english can be discovered . Reverse engineering
from the possible
ratios allowable by the solubilities in the SnO2 might
reveal a likely "data convergence" where certain proportions
match up and withstand scrutiny as likely formulations ,
defined within the claimed selections and ranges .
Wouldn't it be nice if they just stated in plain english the
full details of what was the coating configuration they tested
as being so efficient as a baked perchlorate anode ?
Anyway , the Corning patent pretty much assures there won't be any compatability problems between spinels
and ATO or DTO ....as it appears they will fuse together
nicely .
Edit: It is looking more like Bismuth doped Tin Oxide
*is* the likely catalytic combination for the perchlorate selectivity anode .
See later Diamond Shamrock patent US4272354 .
Also of possible interest is US4267025 which
is also perchlorate anode specific . Both of these however
involve coatings having high percentages of precious metal
oxides , bonded by the DTO mixtures so the information
is more general for the DTO phase than definitive for a
different anode coating where the filler material is not
precious metal oxides .
[Edited on 15-12-2007 by Rosco Bodine]
Attachment: US2564707 Sb2O3 doped SnO2 and tertiary compositions.pdf (479kB)
This file has been downloaded 702 times
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Xenoid
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4 - Coat Anode - Chlorate Cell
My God.... the Co Oxide Anode thread was in danger of dropping of the bottom of the "Today's Posts" list... 
Thought I better post something, the cell is still running after 9 days, current has now dropped to 1.71 amps.
This Co oxide spinel is pretty tough stuff!
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Rosco Bodine
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Yes Co spinel is pretty tough . The Ni analogue is too I think , and the bimetal spinel of the two is synergistic . I think it is probable there is
some polymetal Co spinel that is catalytic for perchlorate . Figuring out which one(s) are specific in that usefulness could be quite a journey .
Looking at the usual peroxidation catalysts seems the logical place to start along with whatever hints may be gotten from the patents .
Also Co spinel is very conductive and a great solid solution component . That Corning patent which I referenced above also shows the easy mutual
solid solution between the Tin Oxide and Cobalt Oxide which I had mentioned before in a summary of some general things I was concluding from the Dow
patents , even though neither patent mentions the easy co-solubility of the Co-Sn oxides specificially , the data shows it is something of a
solid solution mixed solvent for other metal oxides , parallel to the idea of certain mixed organic solvents
having special power to dissolve organic materials .
I seems likely that the mixed oxides system
Sn-Sb-Co-Bi-Mn would result in the baked MnO2 coating ,
perhaps even with added Pb as well , as the diffusion
product and doping in the SnO2 vitreous composite ,
carrying MnO2 as a crystalline separate phase .
I haven't yet inserted any "try values" to make an educated guess as to the proportions , but at this point
these components appear likely in my contemplation of
the mystery formula for the Shamrock patent US4072586 which touted such unusual high efficiency for a perchlorate anode .
Anyway , if the baked anode coating "secret recipe" proves enigmatic and elusive , there is still relief in simply sealing the spinel under SnO2 or
ATO , and then applying
the old and well proven electrodeposited PbO2 as the working coating .
About the cathode geometry , a coil form is good too ,
and easy to make from soft drawn solid wire or small
diameter tubing .
The Lithium Perchlorate thread and some of the little
discussion about oxygen overvoltage got me to wondering
what might happen if an MnCl2 solution was electrolyzed
using an MnO2 anode . I wonder if some LiCl in the electrolyte would cause the MnCl2 to be converted all the way to perchlorate , with zero attack of
the anode ,
because of the anode self-healing effect of the common Mn ion in the electrolyte ?
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dann2
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Hello,
| Quote: | Originally posted by Rosco Bodine
Anyway , if the baked anode coating "secret recipe" proves enigmatic and elusive , there is still relief in simply sealing the spinel under SnO2 or
ATO , and then applying
the old and well proven electrodeposited PbO2 as the working coating .
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Why bother with a Co Spinel when the DTO will do on its own under LD?
Dann2
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dann2
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Hello,
Regarding the 'Old Chestnut' US2564707, the enclosed doc.
is illuminating for the resistance measurement that they are doing on the DTO.
I was inclined to think that the resistances shown for the different %'s of Sb were rather high.
They are not. The patent mesures the films 'in squares' end to end (as it were) as opposed to 'through' the films (the thin way).
The actual resistace 'seen' by the current going from an anode is very very little little. Have not had time to figure it out but an acutal figure on
the RESISTIVITY of actual bulk ATO for different Sb % would be nice.
I propose the following table for resistance seen by 200mA of current coming out through (as it were) a DTO film
Sb = 1%-------------------> Resistance = SWF
Sb = 9%-------------------> Resistance = Slightly more that SWF
Sb = 18% -------------You get my drift.
The patent also states that a high Sb content is needed for
to keep the coat from degenerating when the coating is thich. (Anode coats are thick).
page 5 col 6 line 0
Another reason for high Sb in *Anode* coats may be to give the anode coatings a more favourable
higher O2 and/or lower Cl2 evolution protential.
(as per the Bi2O3 in SnO2)
Dann2
[Edited on 16-12-2007 by dann2]
[Edited on 16-12-2007 by dann2]
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Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
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| Quote: | Originally posted by dann2
Hello,
| Quote: | Originally posted by Rosco Bodine
Anyway , if the baked anode coating "secret recipe" proves enigmatic and elusive , there is still relief in simply sealing the spinel under SnO2 or
ATO , and then applying
the old and well proven electrodeposited PbO2 as the working coating .
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Why bother with a Co Spinel when the DTO will do on its own under LD?
Dann2 |
Because Co spinel appears to be a superior interface which gets past difficulties involved with ATO at the interface . It seems like you would be the
first person to understand this usefulness for all the problems that you have encountered with ATO as an interface material .
And why bother with catalytic baked coatings or PbO2
if all it takes to make perchlorate is ATO ?
@dann2 , please edit that attachment down to 550-600 pixels width so it doesn't foul up the page formatting .
X number of electrons flowing through Y amount of
resistance are going to dissipate the same net IR loss
no matter how you work the geometry you think applies ,
sideways, lengthwise , or through the thickness .
Your proposed 16% Sb in SnO2 creates a separate phase
for more than half of the Sb , even in its maximum dispersed form . The saturation limit has been identified by more than one source as below 8% , and
the optimum conductivity at a third of that . As for your reference , did you notice that they were giving a figure of 1% Sb in a film already more
than double the thickness at which the increased Sb percentage was needed ? The disruptions of the lattice are accompanied
by the development of tint in coatings which are transparent
below that saturation point where the dopants begin to appear as a separate phase . It is that dispersion of particles which causes the color
development and opacity .
Separate phases and their attendant porosity might be beneficial on the outer working coating , but you sure don't want that sort of scenario at the
interface because it
decreases conductivity and it is not mechanically or chemically stable .
I found examples 2, 3, 10, 11, 13 to be interesting ....
and also 15 , 18 , 19 , 21 and 22 .
The data involving the inclusion of bismuth and cobalt
manganese , vanadium , nickel and chromium is useful since these are probable catalysts .
[Edited on 15-12-2007 by Rosco Bodine]
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