Sciencemadness Discussion Board

Multilayer Metal Oxide / Titanium Anodes for Chlorate/Perchlorate

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dann2 - 25-2-2008 at 22:21

Hello,

I mistook my wife today for a hat, but apart from that my mind is OK.

Some more patents

4028215 is a patent that gives a description of Electroplating MnO2 and thermally decomposing painted on Mn Nitrate in alternat layers. They brush off excess MnO2.
Pat. also uses DTO. This patent has been on the board before AFAIK.



Also 4,267,025 is a patent that mixes Platinum group Oxides with Tin Oxide for Perchlorate production.
J.P. Smith (are you still reading!!!!!!!!) was wondering (a long time ago) wheather or not Pt Oxides would make Perchlorate. They do, (along with Tin Oxide), according to this patent. Perhaps this was discussed here before and I missed it (or plain forgot).

Take a look at the bottom of this page. It states that the electrodeposited MnO2 is Gamma, heating gives Beta (what we want).
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

A study of Manganese Dioxide electrodes for Perchlorate production was covered in:
Howard H.C.,Trans. Am. Electrochem. Soc., 43, 51-53 (1923)
Is this article available do yiz think?

Dann2

Rosco Bodine - 26-2-2008 at 00:41

Quote:
Originally posted by dann2
A study of Manganese Dioxide electrodes for Perchlorate production was covered in:
Howard H.C.,Trans. Am. Electrochem. Soc., 43, 51-53 (1923)
Is this article available do yiz think?

Dann2


Couldn't find that online , only in libraries old collections , and on microfilm . That's the older journal name before ECS ,
which is available online only from 1948 to present .

From what I have found it looks like unmodified , undoped
MnO2 won't do the job efficiently or have much endurance in a chlorate or perchlorate cell because it evolves oxygen preferentially . So there is a need for mixing it with other
oxides in a baked coatings scheme to change the selectivity
to evolve chlorine and to raise the oxygen overvoltage for perchlorate . That probably means doping with cobalt
for the chlorate and/or doping with bismuth for chlorate / perchlorate . And Tin needs to be there in the mix .

The MnO2 can perhaps be omitted entirely , as the BTO may very well do what was hoped that ATO would do but doesn't , produce chlorate and perchlorate directly from
a DTO which can function as a baked working coating itself .
Here's what I mean . And this is using nitrates precursors ,
or nitrates with some chlorides in oxygen balanced mixture .

Ti or TiH2 / Co2O3(1 or 2 coats) or
..................Co2O3-Ni2O3 (1 or 2 coats)/
..................SnO2(1 or 2 coats)/
..................SnO2-Bi2O3(many coats)

The first coating would probably also work okay and perhaps better with the spinel dopant nitrates ~6%-8% mixed with the tin nitrate . Maybe three or four coats of that mixture and then follow with the Bi doped SnO2 the same way .

tentacles - 27-2-2008 at 12:23

Quote:
A study of Manganese Dioxide electrodes for Perchlorate production was covered in:
Howard H.C.,Trans. Am. Electrochem. Soc., 43, 51-53 (1923)
Is this article available do yiz think?


My local Uni has this - I will have a copy of the article later today to share with everyone. Hopefully it is useful!

tentacles - 27-2-2008 at 15:38

So I went and copied the pages out of that 1923 article, which is actually not about MnO2, although it does mention it..

http://www.apcforum.net/files/DSCN7227.JPG

http://www.apcforum.net/files/DSCN7228.JPG

http://www.apcforum.net/files/DSCN7229.JPG

I did look in the index of journals 21-41 for any references perchlorate and did not see anything. I'm sick as a dog and was illegally parked so I couldn't look through other indexes.

[Edited on 27-2-2008 by tentacles]

dann2 - 27-2-2008 at 18:19

Hello,
Thanks for that Tentacles, hope you get OK.
My mistake I guess.
Cheers,
Dann2

tentacles - 27-2-2008 at 19:00

No big deal really, it was fun checking out the science library. I think we'd need to find newer research on doped MnO2, if anyone has tried?

Rosco Bodine - 27-2-2008 at 19:52

I need to edit my above post , but the editing time limit has expired , I put down the formula wrong for the spinel
component . It should read

Ti or TiH2 / Co3O4(1 or 2 coats) or
..................Co3O4-Ni3O4 (1 or 2 coats)/
..................SnO2(1 or 2 coats)/
..................SnO2-Bi2O3(many coats)

Also in the antimony tin nitrate thread I found an excerpt
from a paper posted by not_important which tends to confirm what I have been thinking is probably the case concerning stannic nitrate being neglected as a precursor ,
not for any undesirability or unworkability really , but for
its being considered to be an "exotic" precursor , for its unavailability from suppliers due to its short storage life ,
requiring it to be made by the end user . It is then
a matter of convenience which has motivated the use
of alternatives , not necessarily any technical superiority for those alternatives .

I think a bit of ferric nitrate might serve as a stabilizer ,
and reportedy NH4NO3 is a stabilizer although it could be problematic . Acetic acid is another possibility .
One thing I like about the idea of using a stannic nitrate composition as a dip and bake , is the rapidity with which the dipped coating should gel when heat hits it . It should produce very even coatings staying put long before it
is dried out completely and baked . Its tendency to
vitrify on dehydration instead of dusting is also a desirable
characteristic .

anomalously soluble stannic oxalate

Rosco Bodine - 1-3-2008 at 07:21

There was a mention of this patent US4924017 material about six months ago in the PbO2 thead , but the patent was not attached then . http://www.sciencemadness.org/talk/viewthread.php?goto=lastp...

This particular organotin derivative should be noted because of its relatively easy synthesis , and that it is reportedly possible to use bismuth as a dopant in this system , as well as other dopants . This is a non-volatile precursor which can develop hard high quality films on baking , and it *may* also be compatable in mixture with nitrates based precursor
mixtures at low pH . Some additional information on the formation of nitrates and mixed nitrates with chlorides of tin
has been posted in the antimony tin nitrate thread .
http://www.sciencemadness.org/talk/viewthread.php?goto=lastp...

The old tin mordants used by dyers to deposit adherent residues of tin oxide upon cloth for securely binding colorants
to the fiber , is curiously similar technology in several respects with our own efforts at producing doped tin oxide
adherent coatings on titanium . This is precisely the reason
for my recent interest in those old dyers formulations for tin mordants , looking for those compositions which may have value in both arts because of that similarity . That ancient dyers art is very pertinent and parallel to the present work .

[Edited on 1-3-2008 by Rosco Bodine]

Attachment: US4924017 Stannic_acid_anhydride from oxalate and H2O2.pdf (155kB)
This file has been downloaded 747 times


Rosco Bodine - 2-3-2008 at 10:38

Quote:
Originally posted by tentacles
No big deal really, it was fun checking out the science library. I think we'd need to find newer research on doped MnO2, if anyone has tried?


Xenoid has the inside track on the patents which are relevant there . Cobalt is definitely a dopant which seems to successfully change the selectivity from oxygen to chlorine and raise the oxygen overvoltage for MnO2 , and reportedly Bi doping moves things in the same direction and further ,
which gives the performance required for a perchlorate anode . MnO2 seems to behave similarly as SnO2 in response to both dopants , the usefulness of MnO2 seems to be that it is a much more conductive material for use as
a solvent oxide for the dopants , and in the combination of
MnO2/SnO2 behaves as a "hybrid SnO2" solvent oxide "eutectic" or cosolvent of a sort for the dopants like
Co and/or Bi . But it is the dopants , the Co and/or Bi , which
are the essential materials which provide activity for chlorate and/or perchlorate .

What that would mean for Xenoids experiments where plural
coatings of MnO2 alone were baked on top of plural coatings
of Co3O4 , and an anode resulted which for however long it lasted did produce chlorate and perchlorate , is explained
in terms of the Co which diffused upward into the MnO2 and
functioned as a dopant to give that MnO2 the activity it revealed . MnO2 could likely have been substituted with
MnO2/SnO2 , or perhaps MnO2 could have been omitted entirely and SnO2 or Co doped SnO2 may have resulted in
similar activity at least for chlorate .....proving that it was the Co which had more to do with the activity of the anode ,
than was the MnO2 alone .

I would have to go back and reread the thread to see if Xenoid even tried it , but mixing in 5%(or more) Co with the Mn would probably have resulted in a tougher and longer lasting MnO2 coating after baking while the activity of the coating should have increased also . And similarly some added SnO2 would have made the coating more durable
but probably all of the activity of the MnO2 for chlorate and/or perchlorate is attributable to the Co .

[Edited on 2-3-2008 by Rosco Bodine]

bismuth compounds solubility

Rosco Bodine - 4-3-2008 at 10:10

Some of the following references differ from one source and another . But a few interesting things have been found concerning bismuth salts which reveal anomalous solubility .
Mannitol forms an addition compound with Bismuth Nitrate ,
sorbitol and dulcitol are mentioned also , as well as ordinary glycerin , and the usual hydrolysis of Bi(NO3)3 - 5H2O upon dilution is inhibited greatly for these mixtures . All of these materials are polyhydric alcohols and the anomalous solubility may possibly be due to formation of a bismuth alcoholate or "alcoholoxide" substituted hydroxide sol .

Also a citrate salt of bismuth may be gotten from boiling the subnitrate in suspension in citric acid , and the precipitated bismuth citrate rinsed and filtered . This material acts as a monoacid towards ammonia and when neutralized is freely soluble in H2O so long as the solution is neutral to very slightly basic with ammonia . A bismuth acetate crystallizes from the double decomposition of lead acetate and Bi(NO3)3 solutions . A bismuth oxalate can be precipitated from a nitric acid solution of Bi(NO3)3 on boiling with oxalic acid ,
and I could find no information specific to the formation of
a possible peroxalic anhydride derivative with H2O2 as is reported for the stannic anhydride sol , but this seems a good possibility . At the bottom left corner of the attached image the Lowe reference is interesting concerning the
hydrolysis inhibiting effect of acetic acid or 1/300 part of
ammonium nitrate . NH4NO3 was also mentioned in
connection with the citrate in an obscure early pharmaceutical text , as having been used to form more concentrated solutions of Bismuth Ammonium Citrate , but
that older formulation was obsoleted and I could find nothing
further concerning the use of ammonium nitrate for stabilizing bismuth in solutions .



[Edited on 4-3-2008 by Rosco Bodine]

Total Failure

Xenoid - 7-3-2008 at 14:23

My latest perchlorate anode was my most sophisticated attempt to date, and utilised UMLT* and featured NTT**.

I applied 2 coats of Co3O4, baked at 410 oC to an etched Ti rod.
This was in turn coated with 4 layers baked at 380 oC. These 4 layers each comprised 1 dip 'n dry Co3O4, 5 dip 'n dry MnO2 and 1 dip 'n dry Bi2O3 layers!
After this I considered that the Co and Bi levels might be a "bit" high, so I overcoated all this with another 4 baked layers as above but with about 10 dip 'n dry MnO2 layers!
On top of all this I added another 8 layers each baked at 380 oC. of MnO2 which was doped with Co and Bi.

Total layers was about 88...... :o

The anode lasted about 48 hours in a perchlorate cell. The cell was a dark permanganate colour at the end (it put "Purple Haze" to shame) there was also black MnO2 on the bottom of the cell.

The cell started at 4.4 volts, 2 amps (60mA/cm^2) the voltage dropped to 4.2 volts as the cell warmed up and then steadily rose to 6 volts as the anode passivated and was switched off.
The idea for this anode was based on the concept that if you put on enough layers of variable composition, somewhere in there will be a layer that is "just right". Rosco alluded to this some time ago.

Interestingly, when I did the the first bake with the Bi(NO3)3 dip (I actually did two dip 'n dries, not the one in the "ideal" sequence above) shiny, metallic Bismuth was produced on the outside of the anode (that's why it was reduced to one dip 'n dry). Hints of metallic Bi also appeared in some of the later sequences.

Even with this extensive pyrolytic coating, it was still possible to see deep scratches in the underlying Ti rod, this suggests the coating is still only, what, 50 - 100 um thick! It is difficult to see how this type of anode can compete with a plated on layer of PbO2 which can be millimetres thick, and also more catalytically active for perchlorate. A plated coating would also appear to be a lot easier to apply than 88 pyrolytic coats which took me about 1.5 days to do.

*UMLT - Ultra Multi Layer Techniques
**NTT - No Tin Technology
UMLT and NTT are registered trademarks of the Anode Division - Xenoid Chlorate - Perchlorate Corporation.

dann2 - 7-3-2008 at 18:13

Hello Xenoid,

It's no wonder you were not posting for a while!!! (PHEW). You put us all to shame.


I attempted to coat LD (Alpha from a Lead Tartrate bath) on top of Cobalt Oxide spinel (Ti substrate). It plated for a few hours untill my 'set up' went up in smoke. The bench caugh fire (smouldered away), beaker tipped over etc. Luckily that is all that happened before I got to it. The LD is very soft and very easy to scrape off.
I have since purchased a magnetic stirrer hot plate and may have another go.

My LD anode is giving very poor CE. Have tried lowering temp. from 55 to approx. 22. CE went up from 20 to 24%.
Lowered CD on anode, temperature approx 32C. Still 20% CE.
So I have not had my head in the clouds either.
I am currently running at very low CD, will measure CE. Then I intend to run at a large CD (300mA per square cm) and keep temperature low by putting cell in large bucket of water and measure CE.

I keep thinking it may be the cathodes (Ti) but that has to be bullshit. I could attach some mild steel to them easily (then measure CE) to put my mind (what left of it) at rest.

Will run cell to end (low Chlorate conc.) and start a pure Perchlorate cell.


Hashashan has gotten around 50% CE (Chlorate stage). It was estimated by the time it took the cell to start forming Perchlorate.
I am doing titrations.

Am also setting up a Magnetite anode cell. Last time I tried it I ran the anode at far too high CD which was not a fair test of the Magnetite.




Dann2

tentacles - 8-3-2008 at 06:34

xenoid: I've gotten thickness increases out of successive layers, but maybe that just means I'm laying it on too thick? I do wipe between dip n bakes, though - I always figure if I get more than a token smudge that I need to thin the solution (and do). Perhaps your dry but unbaked coats are redissolving when you dip again? That would probably be quite visible however.

It sucks the MnO2-BiO3 doesn't seem to want to work. I will be making up some Bi(NO3)3 tommorow as well as some stannic nitrate via Rosco's method from SnCl2. I think I even have some SnCl2 that is dry, or at least damp to start with a known quantity. I can dope with ~10% Bi by adding with the stannic oxohydroxide when I neutralize with nitric acid.

The plan is to work on this tommorow, or possibly tonight.

Xenoid - 8-3-2008 at 11:38

Quote:
Originally posted by tentacles
Perhaps your dry but unbaked coats are redissolving when you dip again? That would probably be quite visible however.

I will be making up some Bi(NO3)3 tommorow as well as some stannic nitrate via Rosco's method from SnCl2.


Yes, to some extent the "dried" coats were redissolving, this was evidenced by the Mn solution getting darker from Co solution contamination, the Bi solution also took on a slight pink hue as well. It was not possible to obtain a completely "dry" coat in a reasonable time frame, usually they were slightly "gummy". Even if all the coats were perfect and intact the "build up" is still only going to be a few hundred microns at the most (ie. tenths of a mm.) whereas plating can quickley build up coats of a few mm.

Unfortunately my procedures were not very quantitative but at least I expected something that would last longer in a perchlorate cell than just the "straight" MnO2 coating, this was not the case however!

Good luck with the Sn, I had a third attempt at tin nitrate, but just got the same cloudy solution and ppt. as previously. That's why I used NTT .... :D

Bismuth nitrate solution was no problem, I used about a thumbnail pile of crystals, in a test tube, a few drops of nitric acid and diluted with water up to halfway, this was enough solution to "dip my rod in"....

*Mixed* metal oxide = "doped" (including tin) oxide

Rosco Bodine - 8-3-2008 at 14:11

Doing the math ......

NTT (no tin technology) = SOL (shit outta luck) :P

Really , there's probably no getting around the SnO2 .

As for your Mn(NO3)2 becoming cross contaminated with
Co(NO3)2 ......well that's a good thing , and it would probably help the MnO2 to deliberately mix in about 5%
of the Co precursor . The MnO2 without the Co3O4 is an oxygen selective anode coating , and it is only the diffusion which you have been getting from the Co3O4 in underlying layers which has allowed the MnO2 to make chlorate and perchlorate , if the literature which I have seen is correct on this point , as MnO2 alone makes only oxygen and at too low a voltage for chlorate or perchlorate . Tin shifts the selectivity in the right direction also , and both tin and cobalt
toughen the MnO2 mechanically . SnO2 and MnO2 and Co3O4 are all solvent oxides towards each other so they diffuse freely on baking . But there are desirable proportions
which will make for a mixture which sinters to a tough film better than some different proportions .

That old 1857 Chemical Gazette article by Ordway which describes the formation of stable mixtures of tin nitrate and tin chlorides is enlightening . The existence of a mixed valency tin oxide , a "sesquioxide" , and a series of salts
derived from it is something which I have have suspected could be useful in anode precursor mixtures . There seems
to be a niche condition for stable solutions where the higher and lower valency species tend to buffer each other and the result is anomalous solubility and stability for the sol or solution . This should facilitate mixing with precursors for
the dopant materials . Anyway the Ordway article is significant , and I am attaching a cleaned up file which can
be read and printed better than the first attached file I put
in the antimony and tin nitrate thread .

There have been identified several thermally decomposable
precursors for stannic oxide which are highly loaded solutions or sols that are stable across a range of pH values which should make possible mixtures with various dopant precursors . What mixture is best I'm not sure , but I am
pretty certain a *mixture* of the precursors is definitely going to be required to achieve the best MMO end result , as
diffusion alone will be too variable and produce not nearly so intimate a mixture as can be gotten from mixing the precursors before baking .

As an example of compatable pH , what I was thinking for
the Bi doping is using "ammonium stannate" ( ammonia peptized alpha stannic oxyhydroxide sol ) which is alkaline
with the Bismuth Ammonium Citrate which is highly soluble
in alkaline medium ....hoping the two don't immediately react preferentially to precipitate Bismuth Stannate :P

For a highly acidic compatable pH , what I was thinking for
Bi doping is the Bismuth Oxalate or perhaps the Bi Nitrate ,
along with the peroxalic "stannic anhydride" of the patent
US4924017 and related US4873352 . Glacial acetic acid is
also a solvent for Bi(NO3)3 compatable with a low pH mixture .

For a more neutral pH system like some of the Tin Nitrate
mixed valency compositions described by Ordway in 1857 ,
possibly using the anomalously soluble Bi(NO3)3 addition compound with a polyol like glycerin or mannitol would be
workable . Bi(NO3)3 is also reported soluble in acetone ,
but the reports are conflicting concerning the pH useful ,
so this might be workable either in the middle pH or low pH
mixtures , depending on how that reported acetone solubility sorts out .

And beyond these possible schemes there are always the
alcoholate derivatives , of which those polyol addition compounds are a type . The chemistries involved for
Tin , Bismuth and Antimony are similar , so there should
be possible some reasonably stable mixtures of precursors
useful for dip coating .

Anyway , there are possible mixtures across the entire pH range for dopants useful with SnO2 , so the issue becomes
which combination will produce the best quality , most adherent film on baking . There's really not a lot of help
in the literature in the way of predicting what is best .

One more thing , regarding the sesquioxide of tin in solution as the chloride . This still has a reducing properties , but
it is less reducing than SnCl2 . So this mixture might possibly have usefulness as an oxidative soak deposition precursor ,
as it is already "halfway there" ....it might not attack a spinel
in the same way as does SnCl2 . But really I think a more likely to succeed mixture would be cobalt nitrate or chloride
mixed directly with one of stannic oxide precursors would be better , or a single or double coating of spinel alone , followed by the stannic oxide or cobalt doped stannic oxide
precursor mixture . Getting some Bi doping in that interface
mixture too would be ideal . The goal would be to get the
SnO2 lattice of the interface layer as close to saturation as possible with Bi doping , without phase separation . That
would create the oxygen migration barrier needed for protection of the substrate . The Co3O4 doping would
provide conductivity and toughening also . If Sb doping is added as a grain modifier , it should be held to 1/2 % .
Guessing on the proportions of Co and Bi , I would try 4% Co
and 6% Bi ...the rest Sn .

Edit: Reminder that the terminology of the year 1857 differed in its meaning for "equivalents" than is the usage of the term today , due to chemists misidentification of molecular versus atomic weights for gases like chlorine and hydrogen ,
in which case stannous chloride would be mistakenly identified as SnCl instead of SnCl2 , and stannic chloride would be misidentified as SnCl2 instead of SnCl4 , and water
would be mistakenly identified as HO instead of HOH , ect.
Also I suspect the term "equivalents" may sometimes simply be equal parts by weight without any strict reference to molecular weights be they correct or incorrect , so some
interpretation and verification must be applied to these older texts in order to revise and correct the equations for the described reactions so they are accurate using the modern formulas . Experiments should clarify the meaning for proportions that may be unclear from these old texts .

[Edited on 9-3-2008 by Rosco Bodine]

Attachment: Tin Nitrate stable solutions Ordway (Chemical Gazette 1857) legible printable.pdf (489kB)
This file has been downloaded 626 times


tentacles - 8-3-2008 at 15:56

Xenoid: did you try making the SnCl2 > stannic oxyhydroxide > stannic nitrate or the cold dissolution of tin in 28% nitric acid with a dash of HCl?

Rosco Bodine - 8-3-2008 at 17:40

There are definitely intriguing possible reactions which would be generally aligned
with Ordway and Pytlewskis observations .

I was wondering if cobalt carbonate , manganese carbonate , or bismuth carbonate , and/or their nitrates might react in the same way as lead nitrate and lead carbonate was described by Ordway , as reacting with the mixture of SnCl2 and SnCl4 which was made from "tin crystals" (SnCl2) . The K ion and/or KCl from the KClO3
may or may not be simply spectator ions in the reaction Ordway described , as stannic salts do form double salts
with both K and Ammonium chlorides . For our uses the
ammonium salt would be better , if a double salt being present is essential to the stability of the system .

Instead of using KClO3 plus SnCl2 and then reacting with lead nitrate or a different nitrate , it might work similarly
to simply treat the SnCl2 solution with a little NH4Cl and a quantity of HNO3 insufficient for its complete oxidation to
the mixed stannic salts , and then treat the resultant mixture with a carbonate ....perhaps just until a thickening
occurs and then "back titrate" with a little more HCl ,
or perhaps acetic acid to thin it back out again , if it is reversible .

Whatever is the mixture used , it is likely going to have the
electrostatic and wetting properties of the Pytlewski polymer . The subsequent coating of something like
the ammonium stannate sol would be electrostatically opposite to the Ordway-Pytlewski precursors mixture ,
and alternating these differing characteristic mixtures could lead to a highly dense coating with good wetting out
since they should undergo an in situ electrophoresis ....
like a sort of "powder coating" scheme at a nano particulate level , sticking to each other like magnets .
The coatings thickness could build at a rate several times
what the usual sequence of the same precursor builds ,
absent that electrostatic attraction . A tenfold increase
in the coatings thickness build rate would not be unreasonable .
Eight coats of electrostatically enhanced
deposition could be as thick as eighty without it .

[Edited on 8-3-2008 by Rosco Bodine]

Using dichromate

Ioxoi - 13-3-2008 at 14:32

First and unrelated is that Xenoid is my savior now. I've run a sodium chlorate cell with gouging rods and gotten tons of KCLO3 from adding KCl, but it's so messy it's crazy. Seeing pictures of your cobalt oxide substrate + betaMnO2 anodes (purple haze, etc) work perfectly gladdens my heart. I so want to make an MnO2 anode now! You are awesome.

Second, and on topic: have you tried using K2Cr2O7 with your MnO2 anodes? I know that dichromate is terribly bad for PbO2 anodes, but what about your MnO2 anodes? You should see whether dichromate improves chlorate-making efficiency using your MnO2 anodes, or drastically reduces it.

Rosco Bodine - 13-3-2008 at 16:44

Chromium and Vanadium both have been high on my
list of suspects as likely catalysts for perchlorate ,
because each have the ability to form transiently stable
peroxidized forms which are very active oxidizers .
These are definitely candidates for experimenting in combination with MnO2 and SnO2 .

But it would be better to use the ammonium salt like
dichromate , or to use chromium nitrate , than to use
the potassium salt , since you need to keep potassium out of the composition after sintering .

Really if you are using MnO2 , it should be doped with
a second material like these , or cobalt , nickel , or some other dopant which produces an altered selectivity for
the mixture favoring evolution of chlorine . Whether
the chromium would achieve that I'm not sure , but it
is a definite possibilty . Chromium is also interesting because
it reportedly forms that anomalously soluble metastannic acid
mixture which is dervied form the nitrates of chromium and tin , as a concentrated hydrosol , so it would be a very intimately dispersable dopant with SnO2 and likely also with MnO2 as a tertiary mixed oxides coating . This could be one of the easier mixtures to use , among some of the other combinations which are contemplated .

[Edited on 13-3-2008 by Rosco Bodine]

Xenoid - 13-3-2008 at 17:38

Quote:
Originally posted by Ioxoi
Second, and on topic: have you tried using K2Cr2O7 with your MnO2 anodes? I know that dichromate is terribly bad for PbO2 anodes, but what about your MnO2 anodes? You should see whether dichromate improves chlorate-making efficiency using your MnO2 anodes, or drastically reduces it.


@ Rosco - I think Ioxoi is meaning adding potassium dichromate to the cell solution!

No, I haven't tried it!

Actually I never got around to posting a footnote to "Hubert" and "Purple Haze" the final yield of KClO3 was 945g, (recrystallised, dried and clean). I used 2299 amp hours and the efficiency was 53.9% - not too bad.

What would be desirable is if the dichromate extended the lifetime of the anode!

Sorry for not posting for a while, but after my last disasterous attempt at an anode I thought I would have a break for a while! I'll wait for someone to make a breakthrough.... ;)

Image shows dried KClO3 from "Purple Haze" in roasting dish.

KClO3.jpg - 41kB

MnO2 (or Co Oxide) in Diaphram cell

dann2 - 13-3-2008 at 19:08

Well OK,

Here is my break through ;)

Rosco, a long time ago posted a patent for making Perchlorate using Graphite in a cell that had a diaphram. It is an old patent but probably perfectly workable.
Would it work with MnO2 anode (instead of Graphite)?? That would allow MnO2 to make Perchlorate and not erode???

What do ya's think.

Patent attached:

Dann2

Attachment: us1279593.pdf (173kB)
This file has been downloaded 524 times


Rosco Bodine - 13-3-2008 at 20:02

@Xenoid
Yeah it could be good for dichromate in the electrolyte too .
It may work via similar mechanism wherever it is in the system , but in the electrolyte it could have effect at the cathode also .

@dann2
Hmmm , I'm not sure , but it seems simpler to work out a coating scheme that doesn't need a divided cell . I think the MnO2 will toughen up with added SnO2 , Co3O4 , Bi2O3 .

Time for my diva fix ;)

http://www.youtube.com/watch?v=zo5n0HwaRmQ&feature=relat...

http://www.youtube.com/watch?v=rh-q8RNLr3Q&feature=relat...

http://www.youtube.com/watch?v=nDVgb4pJMdI&NR=1

jpsmith123 - 17-3-2008 at 11:15

@Dann2: Is that divided cell idea something you plan on trying? If it works with graphite maybe it will work with MMO anodes too?

I wonder what kind of diaphram material would be suitable for a cell like that?

Anyway, it's not exactly clear to me what's going on with the cathodes in the cell depicted in that patent...are they cups filled with electrolyte? And what's the "hydroxid solution" [sic] they're talking about...are they're just referring to the OH generated at the cathode as the cell operates?

@Rosco: Wouldn't this be more appropriate for you:
http://www.youtube.com/watch?v=2IlHgbOWj4o

chloric1 - 17-3-2008 at 13:37

Xenoid is not posting on this thread and jpsmith resurfaces from the abyss of ambiquity??:o:o What happened here?


@jpsmith-They stated porous cup many times in that patent which basically means unglazed pottery. If kilnless like myself, find one of those outfits that lets you fire your wares and simply make your own "cups". I have wanted to do that but not sure what the best clay is yet.
@rosco-Well, I do not think the divided cell idea is too difficult. The main disadvantage is using higher voltage to drive the current needed. I was a little suspect of the patent becuase they mention perbromates as if they can be whipped up by the kilo. AFAIK perbromates where not successfully isolated until at least 50 years after this patent was published and that was done via fluorine oxidation. So, I wonder if this design is not some electrochemist's wetdream scribbled on a coffeehouse napkin.

jpsmith123 - 17-3-2008 at 14:16

Chloric1 I see mention of a "porous cup", yes, and if that means/includes unglazed pottery, that's fine with me; it just would have been nice if they'd given some specific examples of such suitable porous materials.

In any case, the statement that has me a little confused is this one (@100):

"As the current passes the usual cathode reactions take place in the hydroxid solution 6, provided of course, such a solution surrounds the cathodes 4;"

The "hydroxide solution" whatever it is, is optional? WTF are they talking about?

dann2 - 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]

microcosmicus - 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]

dann2 - 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

chloric1 - 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.

dann2 - 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

jpsmith123 - 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?

Rosco Bodine - 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]

dann2 - 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

tentacles - 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.

Rosco Bodine - 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]

tentacles - 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]

Rosco Bodine - 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]

tentacles - 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]

Rosco Bodine - 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]

tentacles - 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]

Rosco Bodine - 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]

chloric1 - 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.

tentacles - 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]

Rosco Bodine - 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]

tentacles - 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]

Rosco Bodine - 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]

tentacles - 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.

Rosco Bodine - 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 .

tentacles - 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]

Rosco Bodine - 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]

tentacles - 21-3-2008 at 20:11

I have household ammonia, I think it weighs out to about 11%, my nitric is at least 97%..

I already have Co(NO3)2 and Mn(NO3)2 prepared, and dried. I have Bi2O3 (pyro grade) to make Bi(NO3)3 and I was planning on using the SnCl4 to make the alpha etc and neutralized with some diluted nitric acid.

SnCl4 7.03g - I will start with the appropriate amount, neutralize with NH4OH, wash and HNO3
Co(NO3)2 1.126g
Mn(NO3)2 0.59g
Bi2O3 .60g

I made a spreadsheet if you want a copy to check the math.. I'll just label some shit and post it up...

edit: I have some glycerin for my beer brewing (to preserve yeast samples)

[Edited on 21-3-2008 by tentacles]

Attachment: BMC-TO anode calcs.xls (15kB)
This file has been downloaded 655 times


tentacles - 21-3-2008 at 21:31

dann, I made a writeup (word doc), a sort of how-to on making a Ti/Co/Mn chlorate anode. I'm not sure I want to spoon feed anyone, but if you want it for your site, you are welcome to it.

One of these days I will try to compile a list, or spreadsheet, of all the various anodes that have been reported on here. At least, the tested ones.

Rosco Bodine - 21-3-2008 at 21:37

I have the pdf Merck tables for densities / molarities on common acids and bases including NH4OH , I can post if needed . The tetrahydrate of Mn nitrate should be mole weight of 251.01 .

I think the easiest way of calculating the precursor solution
would be to use "precursor equivalents" which provide
the correct percentage ratios of oxides after pyrolysis ,
and then account for the dilution to whatever matches the
~8% SnO2 . I have a good idea how to dilute to the required
concentration , based on weight , using an adjusted reciprocal of 8% as a mulitplier to determine the end weight for the mixed composition . I'm working it out and I'll post the details along with the weights .

IIRC the 8% SnO2 loading was about maximum before the smooth SnO2 coatings transitioned to cracked mud sort of coatings on sintering . It's exactly like the scenario with coatings of lacquer , there's an optimum solvent to "resin"
ratio which forms the best continuous film residue as the solvent leaves .

This whole thing will need to be done on weights to get it
accurate , the first time , not knowing the solution densities
for such a mixture .

I think the easiest way to do this is simply to look at the
percentages as being grams in a total of 100 grams of
total oxides after pyrolysis . So 82% SnO2 becomes 82 grams of SnO2 , 8% MnO2 becomes 8 grams MnO2 , ect .
Then just calculate the molar equivalents of precursors required for the x number of grams needed for that oxide .

The dilution weight will then have to be derived from the outcome of those calculations .

From what I can see already .....
we do arithmetic differently :P
Here's a quick look based on the first calculations I have done on parts totaling 100 of the mixed oxides as related
to precursors for producing 82% SnO2 , 8% MnO2 , 5% Co3O4 , 5% Bi2O3 .......precursor quantities as follows
should produce 100 grams total of the above mixed oxides
represented in their designated percentages .

82 g SnO2 from 190.77 g SnCl4 - 5 H2O (nitrate precursor)

190.77 g SnCl4 - 5 H2O ------> 199.6 g Sn(NO3)4

8 g MnO2 from 23.1 g Mn(NO3)2 - 4 H2O

5 g Co3O4 from 18.13 g Co(NO3)2 - 6 H2O

5 g Bi2O3 from 5 g Bi2O3 (nitrate precursor)

with 4.06 g HNO3 -----> 10.41 g of Bi(NO3)3 - 5 H2O

A solution weighing 1025 grams containing the above
precursors would have an 8% SnO2 loading .
That dilution involves ~784 ml H2O , less whatever
small additional weight of acid , glycerin , ect. is used .

A reasonable sized experimental batch would probably
be one tenth to two tenths the above quantities .

My inclination would be to not dilute it that much and
try it at the syrupy stage first to see how it goes .
It may be that the "glassiness" expected of this mixture
is not as susceptible to the cracked mud kind of problem
as appears at 8% loading on ordinary SnO2 sols and
it may stand a much higher loading which would be good
because it will build thickness faster if it does work out
that way .

It might also be worthwhile to use a mixture of chlorides
and nitrates to possibly utilize the oxygen surplus of the nitrates in aiding the conversion of the chlorides to the oxides , as something towards an "oxygen balanced"
mixture . I would still keep it on the oxygen rich side
however by perhaps 150% of theory for O2 balance if that modification is tried , and still the higher temps are going to be needed to assure completion . This is another totally unreferenced idea , so I can't point to any justification .
It could aid the stability of the precursor solutions , and spread the pyrolysis and diffusion process across a range of temperature , improving the coating by gradualizing the sintering . Or it may not help at all .


[Edited on 22-3-2008 by Rosco Bodine]

9.75% Bi2O3 doped SnO2 optical quality film US6777477

Rosco Bodine - 22-3-2008 at 20:21

The question was asked earlier about possibly using the alpha stannic oxyhydroxide directly as a coating precursor .
It can't be used directly , but after peptization which is very easy :D , it definitely can be used . This is the exception I should have mentioned before .

The patent US6777477 has been brought up several times before as being of possible ( probable) interest , and this seems like a good point to bring it up once again . This patent was mentioned most recently on page 7 of this same thread
http://www.sciencemadness.org/talk/viewthread.php?goto=lastp...
where I was observing that all of these coatings schemes
involve a sol transition , and indeed there are a few schemes
where the peptized , relatively pure hydrosol gotten from
the alpha stannic oxydroxide and its dopants can be used
as a baked coating precursor . This is the exception for
the matter where the directly precipitated alpha oxyhydroxide cannot be used as a coating , as its particle size is too large and it does not sinter to an adherent film
but dusts instead . Ammonia or organic amines change the
surface property and reduce the size of the colloidal particles , acting something like a detergent or emulsifier ,
so that the precipitated larger particles resuspend , and
"redissolve" , something like a controlled reversal of the
neutralization which precipitated the oxyhydroxide , to
form a hydrosol , which is something like an induced supersaturated solution , a colloidal dispersion of the hydrated oxides . Upon evaporation of the water , along with
loss of the volatile amine which is acting as the dispersant , this system will dehydrate and sinter to an adherent film .

See Example #2 for the 9.75% Bi2O3 doped SnO2
http://www.sciencemadness.org/talk/viewthread.php?action=att...
Attachment: US6777477 Sb2O3 doped SnO2 via ammonia soluble derivative.pdf (67.31 KiB)

This patent method avoids the nitrates of tin and avoids alcoholates , yet reports a way of making use of chloride precursors to produce optical quality films via dip coating , which are highly doped with either antimony or bismuth ....
a result which fits our purpose nicely .

When the oxidative soak deposition proved unworkable
using SnCl2 because of it reducing the cobalt spinel interface
coating , this patent method was suggested as an alternative for applying a "sealing layer" over the spinel ,
and it still seems like this should work fine .

This 9.75% Bi2O3 doped SnO2 could serve as a working anode coating , it may even work as an interface coating
but my guess is it would do best to use the Co3O4 spinel
as the interface and then seal it and overlayer it with this
patent composition . The Bi doping is in the range of those
Bi doped SnO2 described in US4272354 as useful , at about
the lowest Bi2O3 in the 9:1 to 4:1 SnO2 to Bi2O3 preferred ratios . The Bi doping percentage could likely be increased
above the 9.75% which provides the optical quality film of
the US677477 patent , to achieve the higher percentage doping described in the US4272354 perchlorate anode patent .

Earlier on page 6 of this thread Xenoid pointed to this
US4272354 patent as a principal interest , and indeed there is something of a nexus between the US4272354 patent
and the US677477 patent Example #2 , for Bi2O3 doping of SnO2 . Sorry for the aggravation if this seems circular ,
once again , but these two patents are very significant
if indeed the Bi2O3 doping should prove out as valuable
for the working coating dopant which indeed is the required
"special ingredient" catalytic for perchlorate .

Simply combining the cobalt spinel interface method which
is already proven , with this Bi2O3 doped SnO2 sealing and working coating , may be the simplest baked coating scheme
which is workable for a perchlorate anode .

tentacles - 22-3-2008 at 22:15

Rosco: the only information I could find said that Mn(NO3) was a hexahydrate - hence the higher mass. Even if it is a tetrahydrate, my crystals are still a bit damp.

I tried to get another damn replacement heatgun today and got the "you need a receipt" runaround, even though I have the box and it's clearly not a year old. So I picked up a B&D unit at HD marked to hit 540C. It's also a bit higher amperage.

Rosco Bodine - 22-3-2008 at 23:07

Yeah I knew the heatgun will be pressed harder on the temp needed for the SnO2 compositions . I still need a few parts for my tube furnace .

CRC gives for Mn(NO3)2 - 4 H2O colorless to pink d 1.82
mol.wt. 251.01 mp 25.8C bp 129.4C
sol 100ml H2O @0C 426.4g , v sol al

from a manufacturers product data

Mn(NO3)2 anhydr. mol.wt. 178.95
d @25C 1.54 50% sol H2O

http://www.sigmaaldrich.com/catalog/search/ProductDetail/RIE...

tentacles - 23-3-2008 at 20:57

Pink? All of the Mn(NO3)2 that I've made is definitely brown. The crystals are also brown.

My CRC (CD version) lists a hexahydrate as well as a tetra - it says the tetra is pink and the hexa is rose. So why are my Mn(NO3)2 solutions, and crystals, brown?

[Edited on 23-3-2008 by tentacles]

Rosco Bodine - 23-3-2008 at 21:17

My 35 year old CRC says colorless to rose monoclinic
d 1.82 . IIRC there is a hexahydrate which exists in solution at ordinary temperature . But if you have the solid at room temperature it is probably the tetrahydrate .
Using a prepared reagent which is so hygroscopic ,
what I would do is go by solution density entirely for
an already existing nitrate solution , or boiling point
indicating the tetrahydrate . But the way to be sure
of molarity is probably to make the nitrate from the carbonate with nitric acid .

The brown color may be some decomposition , or impurity .
A drop of nitric acid may clear it up , it is probably pH sensitive . Seems like I have seen the commercial 50%
packed with as much as 5% HNO3 .

I have looked into this further and found conflicting references , as well as some acknowledgement in the literature of conflicting references and some attempts at explanation of why . The composition of the hydrates of manganese nitrates will usually be a mixture of different hydrates which can have very close melting points which
confounds identification , and it is also possible for a
manganic as well as a manganous oxidation state to be coexistant , complicating the matter further .

This is why it is difficult to be sure precisely what quantity of
manganese is actually present , absent analysis of a sample ,
or direct preparation from a more easily quantifiable intermediate like the carbonate . Know you got to love that :D


[Edited on 24-3-2008 by Rosco Bodine]

Attachment: US2017980 Crystallization Process for Manganese Nitrate Hydrate.pdf (44kB)
This file has been downloaded 540 times


tentacles - 24-3-2008 at 08:05

Hell, If I'm already going to be dissolving crap in nitric acid, no reason I can't measure out mn carbonate too. I might as well just start with Co carbonate as well. I have changed my spreadsheet to reflect this, plus I fixed a bunch of the crappy math I had developed. I guess I shouldn't work on spreadsheets after a few beers.

SnCl4-5H2O 8.16g
CoCO3 .68g
MnCO3 .35g
Bi2O3 .80g

And it looks like it will consume ~6.47mL of HNO3

I do have something to say about that roasted anode - when I went to etch it, I sanded it very briefly with an old piece of sandpaper. (I use 1000 grit to remove anode coatings) I didn't remove all the coating, apparently, because after etching it in hot HCl for 20 minutes, I pulled it out and the coating was still there. This seems like a pretty good sign to me, the previous coatings such as Co, Mn, would dissolve in the HCl.

[Edited on 24-3-2008 by tentacles]

Rosco Bodine - 24-3-2008 at 09:53

You are right , that is a very good sign .

The coating which did sinter is tough enough to endure an etching bath and not just rinse away . It reveals the vitrification to an adherent film of ceramic material did occur . So *if* the conductivity and catalytic activity remain present for that vitrified coating .....bingo! ,
one baked coating perchlorate anode
is what it (very probably:P) will be .

The dopant levels may bear significant increasing of
their percentages for increased activity of a working coating , but for the interface and near interface sealing coatings it is probably best to keep the dopant levels
conservative , aiming for conductivity and a good sealing effect .

From the higher percentages allowable for Bi2O3 doping
of SnO2 , even to the point where it would seem the
SnO2 is the dopant for the Bi2O3 ....the physical compatability is much better for bismuth and SnO2 than
is the case with antimony . The Bi2O3 is a sinterable
film former all by itself , as is SnO2 but of course there
isn't enough conductivity for the pure films to be useful ,
as they are quite good dielectrics . But with added
conductivity from the cobalt and manganese doping ,
then a ceramic semiconductor material is produced .

I wonder if silver oxide or lead oxide might even be useful as an included dopant in a composition like this . If it is
well entrapped in a glass like coating it may be perfectly
stable and could have catalytic activity .

tentacles - 25-3-2008 at 08:59

Making the stannic oxohydroxide - it takes rather more ammonia than I expected. Also, it comes out almost like a jelly for a few minutes. It does settle out at least somewhat. I rinsed and it's settling better now. I probably won't have time to make the stannic nitrate and do a decent job of testing it, so I will wait until tommorow to add the nitric acid and carbonates/oxide.

[Edited on 25-3-2008 by tentacles]

Rosco Bodine - 25-3-2008 at 12:29

Dumping the gell into a larger volume of very faintly alkaline cool ammonia water ( pH 7.5 - 8 ) may facilitate breakup of the gell and settling as a manageable , rinseable precipitate .

You have to be careful with the excess of ammonia because it will only to a point help settle the precipitate , but then more will begin to peptize that hydrated oxide to
a hydrosol , with some conversion to ammonium stannate .

From what I have gotten from a couple of patents the
alkalinity should be 7 to 8 pH , higher pH will peptize ,
lower pH will gell .....so it is quite sensitive .

Also it looks like solutions in the range of 5-10% SnCl4
will gell , so it may be that lower concentrations would be
better . I have never done this precipitation so this would
need to be checked , but what I would suggest is using
relatively dilute SnCl4 in water , say a cold 2-3% solution ,
mixed with cold ammonium hydroxide also of 2-3% concentration with good agitation , the quantities being
calculated at the neutralization equivalents . For convenience what I would do is simply match the two prepared equivalent solution volumes by dilution of the lesser to match the greater volume , and then do a
simultaneous rapid pouring of the two cold solutions together into a beaker with a large stirbar already spinning , and check the pH immediately on the still cold solutions , adjusting it as needed with dilute NH4OH or HCl
until about 7.5 to 8 pH is achieved , then gradually warm
the stirred mixture to perhaps 60C - 70C .

*If* my guess is correct .....
( yeah another one of those maybe huge "ifs" :D )
this sort of manipulation should facilitate a controlled precipitation of a settling and decantation rinseable ,
filterable precipitate , as opposed to having a beaker full of white jello :D .

I have looked for a published preparation but so far
haven't found one .

Edit: deleted remarks about suggesting possible usefulness
of NH4NO3 in part substituted for some of the NH4NO3 as per Lowenthal , as it appears likely that the hydrated metastannic rather than the hydrated alpha stannic oxide
desired would be the product of the Lowenthal method .

[Edited on 25-3-2008 by Rosco Bodine]

tentacles - 25-3-2008 at 14:42

I must have done something right for once, I just kept adding NH4OH solution until the SnCl4 turned and stayed turbid. I had it in a beaker on my stirplate while I added the ammonia from a 20ml syringe. I initially dissolved the ~8g of SnCl4 in 40ml of cold water. By the time I was done I must have had 100ml in the beaker. It definitely got a little soupy there, then I added 30ml of 35% H2O2 and heated. Turned the beaker into skim milk, at about 60C I'd say. I wasn't monitoring the temp. I gave it a few minutes and the temp went up to 80C or so, then I turned off the heat and stirrer and let it cool. The presumed stannic OHO settled down, I pulled off the clear part and washed with ~400ml. Pulled off as much liquid as possible and then put it in the fridge for tommorow.

Also mixed up 18ml ~50% HNO3. A bit strong but I'll be adding it to however much water ends up with the stannic OHO, probably 30-50ml. The HNO3 is in the freezer.

Rosco Bodine - 25-3-2008 at 15:49

That's a coincidence you should mention the H2O2 , as I remembered H2O2 being mentioned in a couple of references as producing precipitation similarly as does NH4NO3 , even in acidic but dilute solutions . I have been looking for a couple of hours to try to find that reference which was basically two sentences with no elaboration .
I think I even wrote something about it in one of these threads but I can't remember where . There's so much data I have been accumulating I can't keep track of it anymore :D

Those proportions that I put down above which were
derived from the parts per hundred , totaling one hundred
are correct . But you would have to adjust the carbonate weights if you use the carbonates instead of the nitrates
of cobalt and manganese . Instead of what I showed above for the cobalt nitrate hexahydrate , you would
use 7.4 grams of cobalt carbonate and 10.6 grams of
manganese carbonate , 5 grams Bi2O3 , and the stannic nitrate derived from conversion of 190.8 grams of stannic chloride pentahydrate . The additional HNO3
for the two carbonates will be 19.5 grams HNO3 pure basis plus 4.1 grams HNO3 for the Bi2O3 , 25 grams HNO3
pure basis would probably be required . And water about 750 ml for these quantitites would put the SnO2 loading at about 8% , but I would try it more concentrated .
An additional 137.2 grams HNO3 pure basis , will be needed for conversion of the stannic oxyhydroxide to stannic nitrate.
For the neutralization of the 190.8 grams of SnCl4 - 5 H2O
would be needed 141.35 ml of 29.4% 26 degree Baume
NH4OH .

You can derive a multiplier for any desired quantity
and multiply with these figures to make a different sized batch .

BTW I found a published English translation of the Lowenthal article today , which is the same article as woelen translated
a few weeks ago . And please note that the SnCl2 shown
in the article is actually in todays corrected formula SnCl4 ,
as the numerical formulas of the time had the number of Chlorines wrong by one half , even though the designation
of stannous compounds and stannic compounds with respect
to oxygen content of oxides is correct . The "protochloride"
designation is the stannous salt , while the "perchloride" designation is the stannic salt .

Edit: Some references say that the precipitate of hydrated
stannic oxide gotten by the Lowenthal method may be rinsed with 10% nitric acid , which indicates that is the metastannic hydrated oxide , rather than the alpha stannic hydrated oxide which is required for dissolution in HNO3 to form the nitrate . So the Lowenthal method is likely useless
if the intention is producing an intermediate for conversion
to stannic nitrate .

[Edited on 25-3-2008 by Rosco Bodine]

Attachment: Lowenthal translation Chemical_Gazette.pdf (234kB)
This file has been downloaded 638 times


tentacles - 25-3-2008 at 17:21

Well, as far as the H2O2 causing the oxohydroxide to precipitate while still acid, I'm not sure how acid yesterday's solution was, but it did not even begin to precipitate. Could have been too concentrated. It worked fine as it was today, though.

I was just using the procedure you've mentioned a few times on the board in various places (here, and in the tin nitrate thread).

Rosco Bodine - 25-3-2008 at 17:52

From what I have read it seems that the alpha stannic oxyhydroxide is unstable , so it is a delicate matter to
precipitate it in manageable form where its density and level of hydration are just right . The concentration of the precursor solutions should be dilute and the neutralization
and precipitation condition controlled . There's other
materials which show similar difficulty .

I know in that US6777477 patent they describe pH 8
as precipitating , but then pH 10.5 is peptizing and that
isn't a very wide transition . That's where the NH4NO3
and heating could help . But then heating tends to polymerize the alpha to the meta form .

You may have the H2O2 use mixed up with another purpose . I can't find the reference on H2O2 and I'm thinking it may have applied to the stannous salt for another purpose and product , like for raising the SnCl2 to SnCl4 .....so you may not have what you think ,
but a metastannic oxyhydroxide instead . It's the hydration state and level of polymerization which
determines which isomer you have . The only other place I recall H2O2 being used was with the peroxyorganic acid
substituted metastannic acid sols .

Wait a minute ....I found that obscure reference on H2O2
See page 6 of the attached excerpt , (page 270 item #14) .
This may be a variation on the Lowenthal synthesis because
a careful neutralization is used in the Lowenthal method
also whose purpose is in fact to produce an easily filtered
and clean and pure precipitate to facilitate analysis . However
the precipitate is not really the hydroxide but a basic hydroxide or "oxyhydroxide" for the Lowenthal method ,
and I suspect these may be the same products . Very interesting , I meant to look into this before but something else came up and I forgot about it .

*Stannous* salts are used with this H2O2 here though , I
was right about that :D . I suppose what probably happens
here is something similar to the oxidative soak deposition ,
but here the process is a bulk precipitation so rapid that
the hydration level is maintained . This could be a shortcut
method from the metal or SnCl2 , however to a precipitate
which might be filterable . Somehow I don't think this
would go as well as working from the already oxidized
stannic salt , as per Lowenthal or ordinary neutralization
with NH4OH . Later references have indicated the Lowenthal method likely produces the metastannic hydrated oxide which is unreactive with nitric acid .

However ammonium carbonate , and likely ammonium bicarbonate , should produce the desired alpha stannic oxyhydroxide in the same manner as does ammonium hydroxide , and use of these carbonate of ammonia makes
the neutralization pH less critical , as the precipitated alpha
stannic oxyhydroxide is insoluble in excess of ammonium carbonate , not forming ammonium stannate and peptizing
as would be the case with an excess of ammonium hydroxide .

[Edited on 25-3-2008 by Rosco Bodine]

Attachment: Pages from 265 Analytical_Chemistry.pdf (299kB)
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tentacles - 25-3-2008 at 18:23

Ah, reading back I realize it may/was not needed since I started with the stannic chloride. No big loss, certainly. What I seem to be getting from all this discussion and whatnot, is that I really need to get my hands on a pH meter. Better yet, a pH controller which could serve as both meter and a cell regulator.

Rosco, any idea how a pH probe would hold up in a chlorate/perchlorate cell environment? I'm thinking maybe not so good, if for no other reason than the plastic won't hold up to that kind of abuse. Let us know what you think.

I guess I'll find out if it's the metastannic oxyhydroxide tommorow when I try to dissolve it with the HNO3.

Rosco Bodine - 25-3-2008 at 18:31

I'm not sure about the pH monitoring . What would
be great is some sort of color indicator , nothing to break or corrode:D

See my edit above , I found that H2O2 reference .

BTW , using only 8 grams of SnCl4 , is that just a test run ,
because you are making not much , like a large test tube amount .

After doing some more reading , it appears that the most desirable reagent for neutralization of the stannic chloride
to produce alpha stannic oxyhydroxide with least difficulty ,
is ammonium carbonate . The neutralization pH is not
critical , as the precipitate is not soluble in an excess of
the ammonium carbonate . Now that I have rediscovered
this , I am nearly certain this was declared in one of the patents which has been posted , or perhaps one that I have
already but have not posted .....this bicarbonate and/or
carbonate neutralizer seems extremely familiar and I know I have seen it somewhere before .

[Edited on 26-3-2008 by Rosco Bodine]

tentacles - 25-3-2008 at 22:05

I don't really see any reason to make more than a test batch, after all, how many anodes can ~80ml of solution make? A crapload, anyways.

How would I make ammonium carbonate? Ammonia + carbonic acid? I suppose it's a bit of a moot question, if the current method works without too much trouble at least.

No reason I can't hook up my carbonation chamber and crank out some fizzy water if that's what it takes.

Rosco Bodine - 25-3-2008 at 22:27

If you do careful work , the carbonate or bicarbonate isn't really necessary .

It's really only useful for reducing the need for pH accuracy.
By using the bicarbonate of ammonia , there is no need for
simultaneous addition sort of mixing of cold solutions kept
slightly acidic and then titrated after mixing to a barely alkaline pH for precipitation on warming .

Using the bicarbonate allows simply running in the stannic chloride into a large volume of the bicarbonate , where the
instantly precipitated stannic hydroxide is not affected by
the excess bicarbonate . See US4775412 which uses
this method .

This is the same result as using the method described in preparing the intermediate of US6777477 . Actually
I have rediscovered this too , and searching I found
the exact same parallel had been noted before in another thread , about a year ago .
I *knew* I had seen the bicarbonate used before , but forgot what was the advantage for it . You just have to have more accurate measuring of your reactants when alternately using the ammonium hydroxide and watch the pH so it doesn't go basic enough to peptize - redissolve the precipitate you want to filter and keep for conversion to the nitrate . Keep the endpoint pH 7.5 to 8 and you're fine .
Let it go to pH 10 - 10.5 and you will have a peptizing system underway . How reversible the peptization is I'm not sure , maybe not reversible at all . It could very well be that
the peptization product involves a conversion to a metastannic acid hydrosol , and that involves a change
not reversible by something trivial like a change in pH .
Fortunately the peptization requires some hours to proceed , so if you overshoot the target pH you have time to adjust if you don't delay .
http://www.sciencemadness.org/talk/viewthread.php?goto=lastp...



[Edited on 26-3-2008 by Rosco Bodine]

tentacles - 26-3-2008 at 09:22

It would seem I don't do careful work, because the nitric didn't dissolve the precipitate in the least.

How much ammonium carbonate would you expect I'd need? It looks like I'd have to make it myself to get any reasonable quantity. I've tried to find baker's ammonia (NH4HCO3) here but no place seems to carry it. Going to try a pharmacy next.

Rosco Bodine - 26-3-2008 at 11:41

The problem likely was the H2O2 .

The H2O2 evidently polymerized the alpha stannic oxyhydroxide to the metastannic oxyhydroxide ,
which is something I had a worry may occur .

Try the dilutions and procedure I first suggested and
it will probably work okay . It may precipitate fine from those dilute solutions even slightly incompletely neutralized and slightly acidic . In other words it may be better to err on the side of incomplete neutralization by
a percent or two , to prevent peptization by going to far
with the ammonium hydroxide .

The neutralization of one mole stannic chloride requires
4 NH3 , so that would be 2 moles of the normal carbonate , or 4 moles of the bicarbonate .

If all of this proves awkward then just use one of the
Ordway described methods of dissolving the tin metal in
an aqua regia that is predominately nitric acid , and bear
the lesser percentage of SnCl4 that is mixed product .
The bulk of the tin will be present as the nitrate and
will still likely be at an oxygen surplus . And there will
probably be enough excess acid there for simply adding
your dopant precursors to neutralize that excess acid .

tentacles - 26-3-2008 at 14:03

I will try again with the ammonium hydroxide, without the H2O2. The carbonate is proving difficult to find, up here at least. And it just seems like a bitch to make if I go the ammonia + carbonic method, plus that would be a very dilute solution by that time.

Rosco Bodine - 26-3-2008 at 21:12

As sort of a side experiment ....

If you haven't tossed out the metastannic acid , try
adding about a quarter to three tenths gram of iron filings
and some nitric acid , boil it down to a residue after the iron dissolves but don't overheat it . See if a little water
then dissolves everything .

tentacles - 26-3-2008 at 22:25

It's already long gone.. but who knows, tommorow's may turn out just as badly.

tentacles - 28-3-2008 at 14:58

Well, I've got more white almost-sludge precipitate in a beaker again. It sat there all day after I made it wednesday - was it wednesday? Anyhow, I was all set to try making the stannic nitrate again, and I decided to test the B&D heatgun I picked up - what a piece of garbage! The box said 280/540C, but my thermocouple said very differently! I only got to 10mV - a pathetic 247C or so, and the damn thing died! So I scrapped plans to do anything useful until I got a new heatgun.

Today I picked up another replacement unit (number 3!) and am considering disabling the low setting of death. I also looked at Rona up here, they have a few models that look much more promising, including a Makita thermocouple controlled unit, and a standard industrial type heatgun. The Makita is rated to 600C.

Rosco Bodine - 28-3-2008 at 18:49

Quote:
Originally posted by tentacles
Well, I've got more white almost-sludge precipitate in a beaker again.


You might try the precipitation conditions described in US6777477 .

Alternately try limiting concentration of the SnCl4 to the 2 to 3% level , and doing a rapid simultaneous pour mixing of cool solutions into a like volume of cool H2O containing the bare neutralization equivalent of NH4OH .

I am going to say limit the warming I suggested earlier to more like 40C , barely warm because of the attached reference which reports 60C will convert the alpha to the meta stannic acid . This confirms what I suspected about the
instability of the alpha form , but describes the alpha as being even more prone to polymerization to meta at a lower temperature than I expected . Evidently the precipitation temperature will be determinate on whether the alpha or the meta form is produced .

The attached patent US2460734 describes that the SnCl4 diluted in H2O to less than 4% concentration hydrolyzes completely in one hour at room temperature to a dispersion , a sol of alpha stannic acid , and free hydrochloric acid .
So it is simply a matter of then neutralizing the free HCl and salting out the hydrated SnO2 by destabilizing the already existing sol .

I am going to get some ammonium bicarbonate so the method of US4775412 can be followed for precipitation of the alpha stannic oxyhydroxide .
Technically , this looks the easiest sure way .

A heat gun is going to be really pressed to do the job on the
tin oxide sintering . A well insulated furnace tube and maybe even some sort of thermal breaked holder for the anode substrate is probably needed .

The pure stannic nitrate which is being made here is not going to have good stability by itself . There may be improved stability required by addition of a small amount of
ammonium nitrate , if there isn't sufficent residual ammonia
in the precipitated alpha stannic acid to supply it when the nitric acid is used for conversion to the nitrate . Also
a small amount of acetic or tartaric acid may be needed
to stabilize .

The compositions described in the Ordway article which are
complex mixtures have better stability than pure stannic nitrate , and may prove to be better precursors . Those
complex mixtures have stability better than straight stannic nitrate , but lower stability than the chlorides derived sols or alcoholates . The patents which mentioned the usefulness
of the tin nitrate did not specify anything about the nature
of the tin nitrate composition to be used , so there could be
some tuning of that nitrate precursor required to get it right .

For example the precursor which works best could not surprisingly turn out to be a mixture of stannic nitrate and stannic chloride with acetic acid or tartaric acid in small amount , or the mixture most desirable could be one of
the Ordway mixtures . Or it could fit the composition of
one of the Pytlewski mixed valency sort of polymers which
are also involved in some of the Ordway described mixtures .

Stannic nitrate alone may not prove to be the single answer
as an SnO2 precursor but only a component . Just pointing this uncertainty out concerning the stannic nitrate and the
context in which it is useful , is a long way from being fully described in any existing literature .....so what we are doing
is basically pure experimentation with regards to the finer points which do involve a few unknowns . :D

Attachment: US2460734 Alpha Stannic Acid process.pdf (123kB)
This file has been downloaded 1064 times


Rosco Bodine - 1-4-2008 at 23:39

Here is a hypothetical coating scheme based
upon a combination of spinels which are known .

An interesting series of bimetal spinels which
may have usefulness has caught my notice ,
in particular because of the known application
of zinc chloride as a flux in soldering and brazing .

TiZn2O4
SnZn2O4
TiCo2O4
SnCo2O4
ZnCo2O4

This series of spinels formed from a mixed nitrates and chlorides precursor system may form a very good interface
on a titanium substrate , *if* the fluxing property of the
zinc chloride at high temperature is effective on the
titanium . This would follow something like the idea of
the Beer patents where an increased thickness of mixed
oxides involving doped titanium oxide itself is included
in the interface layer ...thickened enough that it becomes
really a working coating . If the molten zinc chloride component does indeed attack and etch into the titanium itself or any oxide of titanium during baking , the associated
possible spinels of TiZn2O4 and TiCo2O4 might function in
a manner which mimics ruthenium with regards to the doping effect on the titanium oxide . The unreacted Zn and Co
dopants could then further react with each other to form
a bimetal ZnCo2O4 spinel , and/or could form bimetal spinels
with the Sn , SnZn2O4 and SnCo2O4 . In an excess of SnO2
as the solvent oxide .....all of these possible spinels could form and all would be expected to be electrolytically active .
The ZnCo2O4 bimetal spinel has already been reported as useful for chlorate production . The usefulness of the other
possible spinels is unknown .

This is a possible combination of materials which could be good as an interface and sealing and working coating ,
all in one . Bismuth doping might also be added .

I haven't attempted to work out what precursor proportions would seem right . All of these spinels are expected film formers themselves and should participate in the usual
DTO scheme where the SnO2 is the major phase .
It may be possible to work up the precursor
mixture by simply making with SnCl4 in minimal H2O a slurry of the carbonates of the cobalt and zinc and possibly bismuth , and then drip in nitric acid to clear the mixture , and maybe add a few drops of acetic acid and perhaps glycerin .

tentacles - 2-4-2008 at 10:18

Well, in absence of further messing with making tin nitrate - I have instead made another small batch of SnCl4 based precursor, baked at 546C for two coats, whereupon heat gun #4 said it's farewell.

I put down a Co interface layer and then two coats of the SnO2 based scheme as before. I did a little bake and checking, and it seems that it really needs to bake hot to sinter in. I took it out at 515C and this was not hot enough; at that point I decided to just get it over 540C.

I guess it's time for a different brand of heatgun. I just hope I can get the bastards to refund me for this one w/o a receipt.

edit: I dunked this one in a KCl cell for now, it is evolving chlorine aggressively. I'll check on it again when I get home from work. Cell is running on a 5V computer PSU. 25mA/cm^2 density. The anode is a bit far from the cathodes, about 5-6cm

another edit: Good thing I checked on it before I left - the anode started eroding from under the coating, at the edges at least. It's got sort of pock marks on the edge, like round serrations. Perhaps it just needs to be sealed better, and I should probably smooth the edges of the Ti strips better.

[Edited on 2-4-2008 by tentacles]

Rosco Bodine - 2-4-2008 at 12:15

Inorganic polymers and their quasi-inhibited precursors
are a barrel of fun , huh ? :D

From everything I have read the alpha stannic hydroxide
is definitely unstable and heat sensitive , as is the stannic nitrate . So it may very well be better to go the Ordway route where some mixed chloride and nitrate , as well as mixed valency polymer is present , in order to achieve stability .

There are references to alpha stannic acid which has been precipitated via hydrolysis of a heated very dilute solution
of a stannic salt , being converted to metastannic acid
if the solution is boiled more than just briefly . It may be partly polymerized at lower temperature over longer time .
So dilution , temperature and pH influence the precipitation and obviously there is a reaction conditions window which is favorable , but there is a time window also , as the alpha form will tend to polymerize to the meta form at some unknown rate made worse by passing time and also by heating .

It would probably be best to avoid letting the alpha stannic acid precipitate stand for any extended time as it is unknown what its half-life may be .

The higher temperatures being required for complete conversion of the SnCl4 to SnO2 is a good reason by itself
to use something else as the precursor .

[Edited on 2-4-2008 by Rosco Bodine]

another MMO of possible interest

Rosco Bodine - 7-4-2008 at 00:19

Here's another mixed oxide which would be on my list of
prime suspects as having possible catalytic activity
for chlorate and perchlorate .

http://dx.doi.org/10.1016/S1293-2558(02)01356-0

Pb3Mn5V2O16: a new lead manganese vanadate with double MnII/MnIV valence

[Edited on 7-4-2008 by Rosco Bodine]

chloric1 - 7-4-2008 at 06:49

DOI not found

The link....its dead Jim.

Rosco Bodine - 7-4-2008 at 08:43

Fixed the bum link . I forgot to use the url prefix and suffix and the forum software seems to not register the pasted link correctly without that detail .

Above it was mentioned that these MMO compositions
are "inorganic polymers" , and that would seem to be
correct also in regards to the "isomers" of hydrated SnO2 .
The various forms of stannic acid all appear to be SnO2
differing only in their level of hydration and polymerization with the highest level of hydration and lowest level of polymerization being stannic hydroxide , and the next dehydration step providing alpha stannic acid , which is
also unstable and polymerizes to a five unit molecule metastannic acid , which further dehydrates to SnO2 .
There are mixtures and degrees of dehydration and polymerization which may exist between those distinct
materials , and these are likely the "sols" where the
composition is indefinite and/or in transition with regards
to its state of hydration and polymerization of the precursor for the contained SnO2 component .

Dopant materials which have similar chemistry can substitute and cross link with the SnO2 , forming
complex inorganic polymers and glasses , ceramic
materials , or spinels , and possibly other complex
crystalline MMO compounds . Temperature has significant effect on the composition of the hydrated precursor mixtures and also what the end composition of these mixtures will be after dehydration and sintering .

These materials behave similarly to "bakelite" formaldehyde resins as their organic analogue .

There is reportedly a lead ferrite , or lead-iron spinel which might be worth an experiment . It is PbFe2O4 . Have absolutely no information on it . Reportedly also there are
similar spinels of iron with cobalt and manganese and titanium . CoFe2O4 , MnFe2O4 , TiFe2O4 . So a mixed precursor system containing as dopants , lead , cobalt , manganese and iron could have usefulness as a chlorate or perchlorate anode .


[Edited on 7-4-2008 by Rosco Bodine]

Plate MMO

Ioxoi - 14-4-2008 at 11:53

Hi guys,

I've seen Xenoid's coating procedure for Co / MnO2 onto titanium rods. He dips them and then bakes in a heat gun. Can this procedure be applied to Ti plate? I'm going to get Mn(NO3)2, Co(NO3)2, and a big thin plate of Ti (12" x 5") for my birthday in a few months, and I'm gonna see if I can make strip anodes. I'll cut the plate into strips and coat them with the solution.

What I'm gonna have to figure out is how to "bake" 'em. It'd be great if you could just shove the plates into a toaster, a la Pop Tarts, but I doubt the coatings would come out good. Any ideas before I destroy a good Ti plate? Oven? Campfire?

Xenoid - 14-4-2008 at 13:35

@ loxoi

I don't want to put you off experimenting, but if you are actually more interested in the chlorate and perchlorate rather than making anodes you may be better off getting a "commercial" MMO and/or platinised Ti anode. Several of the pyrotechnics suppliers now have them in stock.

A toaster won't get hot enough for baking, a small toaster oven with maybe an extra element added might do the job, there is a discussion in (I think) the Cobalt Oxide Anode thread. There is no reason you couldn't use a hot air gun with a strip Ti anode rather than a rod, provided it doesn't "blow around" too much or is too big.

I have wondered about Ti sheet, I'm not sure what the coefficient of expansion is for Ti, but perhaps with a large surface area, bonding of coatings may not be as effective as with a rod, due to contraction and expansion during the heat cycles.

tentacles - 14-4-2008 at 16:32

It's certainly POSSIBLE to use strips of Ti sheet - I haven't done any grueling tests to see how long they last though. The Co/Mn anodes seem to work just fine for the couple hours I've run them. I just used a heat gun + tube oven for those. There's wasn't any problem with them swinging in the breeze, at least with the gun I used. I just drilled a hole at the top and ran a piece of SS wire through, twisted it tight to make a handle and spread the ends to support it.

chloric1 - 14-4-2008 at 19:13

Quote:
Originally posted by Rosco Bodine
Here's another mixed oxide which would be on my list of
prime suspects as having possible catalytic activity
for chlorate and perchlorate .

http://dx.doi.org/10.1016/S1293-2558(02)01356-0

Pb3Mn5V2O16: a new lead manganese vanadate with double MnII/MnIV valence

[Edited on 7-4-2008 by Rosco Bodine]



The abstract seems to suggest PbO2 found in "lattices". If this oxide cannot produce perchlorate, it should be amiable to LD plating

diva update

Rosco Bodine - 15-6-2008 at 10:29

Nothing new on the anode project because my time has been otherwise thoroughly occupied with other pressing business.

However, it does seem long overdue for a diva update,
so ....on this father's day especially for the other fathers
of daughters as myself, but for everyone else as well ....
enjoy


To Where You Are
http://www.youtube.com/watch?v=qZiS_Purjhg&feature=relat...

Walking In The Air
http://www.youtube.com/watch?v=Sfm0qNBZo1I&feature=relat...

Going Home
http://www.youtube.com/watch?v=oHBCXi7Ckuk&feature=relat...

Winter's Light
http://www.youtube.com/watch?v=GL_ag3NQ0o0&feature=relat...

Someday
http://www.youtube.com/watch?v=E9PLU6JYYpg

When You Believe
http://www.youtube.com/watch?v=nBUhGkMUoEI&feature=relat...

Leander - 6-10-2008 at 03:19

Sorry for the topicbump, but this could be interesting. According to patent CA 1083337 a dense and uniform coat of MnO2 can by applied on a substrate (aluminium and tantalium mentioned here) by means of a slurry of Mn(NO3)2, Mn(OH)2 and NH4NO3 in H2O with some methylcellulose for viscosity. This has a couple of advantages over the traditional method of dipping your substrate in salt solution, and then thermal decomposing it. My gues is that a much thicker coat can by applied this way, drasticly reducting the ammount of dips required for a nice coat.

Since English isn't my 1st language I haven't been able to find out yet what kind of industrial applications this invention is ment for. Production of chlorate or perchlore is not mentioned.

interesting recipe

Rosco Bodine - 6-10-2008 at 22:13

Attached here is the US issue of the same patent as

US4148131

Actually the presence of microdispersed free carbon has been reported to lower the development temperature and baking time for nitrate precursors of metallic oxides, and likely the same is true as well for easily carbonized precursor thickeners like methylcellulose. I have a journal article related to that and I will try to find and post it as well.
Polyvinyl Alcohol has also been reported useful as a precursor solution thickener to increase the thickness building rate for doped tin oxide films which are based
on stannate / bismuthate precursors.

Attachment: US4148131 MnO2 Baked Coating Method.pdf (719kB)
This file has been downloaded 745 times


possibly adaptable to MnCo2O4 spinel

Rosco Bodine - 6-10-2008 at 23:13

The above patent is possibly applicable also in benefitting
the formation of better baked coatings of mixed nitrate precursors for bimetal spinels like MnCo2O4, or for mixed Co and Ni spinel , or the monometal spinels.

The technique could certainly be easily enough tested to see if indeed a tougher baked coating results. The photosensitivity of the precursor mixture is certainly new information that is noteworthy.

Attached is the journal article I mentioned earlier about the
effect of carbon in reaction with the nitrate precursors. I have hypothesized that mixed valency precursor salts
where some of the nitrate oxygen is available for reaction
with the lower valence metal ion should have a similar effect on promoting the pyrolysis.

Decomposition of mixed Mn and Co nitrates supported on carbon ( attached )

Definitely time for a diva break :D:D:D:D

http://www.youtube.com/watch?v=VRFS_WxtMoA&feature=relat...

[Edited on 7-10-2008 by Rosco Bodine]

Attachment: Decomposition of mixed Mn and Co nitrates supported on carbon.pdf (236kB)
This file has been downloaded 2180 times


Niobium DTO anti-depassivation coated Ti Anode

Rosco Bodine - 20-10-2008 at 11:56

Bismuth has already been identified in the literature as having good effect as a dopant for tin oxide useful as an oxygen diffusion barrier , anti-depassivation coating on Ti substrate anodes, the Bismuth also having catalytic activity in the production of perchlorate.

Niobium (formerly Columbium), a closely similar sister element of Tantalum found intermixed in their ores the same as Nickel and Cobalt, is also reported in the literature to
have a similar value as a barrier to oxygen diffusion caused
passivation of a Titanium substrate anode. What may be
if any catalytic activity in the production of perchlorate is unknown. The patent US4471006 Niobium DTO enhanced oxygen anti-passivation Anode describes how the combination of 5-valent Nb2O5 as a dopant material with
4-valent indigenous TiO2 or SnO2 also applied thereon,
results in an N-type semiconductor coating which is
anti-depassivating , allowing anodic current flow.

Probably Vanadium Pentoxide, V2O5 would behave similarly
and may even have catalytic effect via an unstable pervanadic state. This is something I have postulated earlier in some of these threads, but have done no experiments to confirm. IIRC in one of the patents posted by
JPSmith a baked coating containing vanadium doping on a hydrided Ti substrate was a successful scheme.

Niobium compounds are probably three times as expensive
as Bismuth, but this still is much less expensive than Ruthenium / Platinum series candidates for the intermediate layer or DTO coatings, and because of the excellent oxygen
diffusion barrier anti-depassivation performance reported for Niobium, this seemed worth making note . Niobium might find
usefulness in combination with other dopants or layered MMO schemes where the "labrynth effect" of differing oxygen
overvoltages for differing sequential layers is applied, testing
another one of Rosco's postulates , of course :D

And obviously ....that's right , now it's time for another diva break :P

http://www.youtube.com/watch?v=YNlpxJO1Uiw&feature=relat...

http://www.youtube.com/watch?v=koi_f3fB2h8&NR=1

Other Niobium related patents of possible interest are
US3950240 Niobium Doped Tin Oxide Anode
US4873352 Niobium DTO via Oxalate H2O2

Attachment: US4471006 Niobium DTO enhanced oxygen anti-passivation Anode.pdf (140kB)
This file has been downloaded 1042 times


another organic precursor MMO of possible interest

Rosco Bodine - 10-12-2008 at 20:29

The last part of page 172 and all of page 173 in this book preview shows use of citric acid and ethylene glycol as useful carbon donors in a pyrolytic decomposition of metal nitrate precursors, in the intermediate precursor form of a dispersed and polymerized sol-gel, which smoothly react to produce
on pyrolysis a substituted spinel-perovskite ferrite material
with no byproducts.

http://books.google.com/books?id=GHUttThdotcC&pg=PA172&a...

Bismuth, cobalt, and iron are the metals involved in this particular spinel-perovskite, which might be an interesting
material to use as a component in a doped tin oxide scheme,
seeing that chemistry of the precursors and the pyrolysis temperatures are compatable.

Swede - 27-1-2009 at 14:58

This slightly aged thread seems a good place to kick-start a bit - alternate anodes for electrochemistry as regards perchlorate.

We've beaten PbO2 to death. I'm playing catch-up on the Bismuth, tin, and cobalt options. Now it's time to explore boehmite. I've got the three different varieties of boehmite on hand, and the following reagents:

Cobalt nitrate
Cu nitrate
Nickel nitrate
Tin (II) Chloride
Bismuth hydroxide
Bismuth Subnitrate
Lead nitrate
Lead dioxide
Lead monoxide

And assorted other reagents, in support of an anode attempt. I've been reading the literature as much as I can, and if you google "alumina tubules catalyst", that sort of thing, the research is on in the "real world" at a fast and furious pace. Nano is the future, apparently, of catalytic chemistry.

I'm looking for thoughts, an "angle", towards an alternate anode. I do have a precision furnace, good from 250 to 2000 f. Sand blaster too. Looking at options! Really, the only thing I'd like to avoid is Platinum and Palladium, due to costs, both for me, and for anyone else if an anode actually works.

[Edited on 27-1-2009 by Swede]

jpsmith123 - 27-1-2009 at 15:37

Hello Swede,

With the nice workshop, resources, time, etc., you seem to have at your disposal, maybe you'd like to experiment with electrolytic DLC films?

The main equipment required would apparently be an adjustable HV power supply, say 0 to 1000 VDC @ 50 to 100 ma or so.

I'm presently trying to get my hands on a decent HV power (so far with no luck), and once I get one, I plan on trying to make DLC films from DMSO and methanol (using boric acid as a boron source).

Rosco Bodine - 27-1-2009 at 20:51

@Swede, Among those other reagents is there nitric acid, acetic acid, ammonium hydroxide, ammonium carbonate or bicarbonate, ammonium fluoride or bifluoride, hydrogen peroxide, citric acid, glycerine ?

BTW with regards to soluble Niobium salts, US5419824
describes a preparation of ammonium niobate which reportedly has good solubility in water.

There may be a fair amount of surplus Niobium-Titanium alloy wire available cheaply, as an associated scrap from the Cern supercollider project.....and maybe some other relatively exotic materials also. I have been anticipating getting my hands on some of this scrap at some point and contemplating possible uses for it .....like superduper anodes:D

[Edited on 27-1-2009 by Rosco Bodine]

Swede - 28-1-2009 at 07:42

@jps - A High voltage supply is something that I am currently lacking. DLC films - yet another resource to investigate! :D

@RB - Of the additional reagents you mention, I am LACKING ammonium hydroxide in any real strength, acetic acid, and the ammonium fluorides... the others I do have.

I'm digging through some of the boehmite literature right now - there is a lot of it. The basic problems - introduction of the catalyst into the boehmite pore structure, transition of the catalyst(s) to active oxides, and dipping/adhering the slurry to an appropriate shank. I have some niobium metal, and the possibility exists to create salts of niobium.

One limiting factor is temperature - above 400C, apparently the boehmite breaks down and the desirable microtubule structure is destroyed.

The anode obviously must conduct, and like the traditional electrodeposited lead dioxide anode, the barrier between PbO2 and Ti must not passivate. Perhaps once again, the commercial MMO substrate may be the material of choice.

Rosco Bodine - 28-1-2009 at 15:40

Hold your horses on the MMO if you mean noble metal oxide ( NMO ) variant. And the literature you can read endlessly looking for ABC - 123 that you will be lucky to ever find, particularly if it is stuff that is known already
ten different places but is kept in shop and proprietary with regards to a niche application end use like a perchlorate anode. Most of the metal oxide technology literature is specific for sensors, other electronic devices, optical devices and other mass production items, and
perchlorate anodes are simply *not* a mass production item but an obscure kind of proprietary "factory utensil".
You are very possibly looking for a trade secret that isn't going to be found published anywhere.

There's a lot of stuff in the literature that is "read between the lines" and figure it out how it translates to whatever you are trying to do. Have you got a blueprint
and drafting supply shop nearby? They keep and usually sell ammonium hydroxide of exceptional purity for use
as a developer in the diazo process for blueprints. You can probably get a gallon of 26 Baume ammonia ( NH3 29.4% solution in H2O ) for under twenty bucks.

[Edited on 28-1-2009 by Rosco Bodine]

Some notes on MMO/MnO2 anodes from a while back!

Xenoid - 14-3-2010 at 17:34

Whilst not wanting to return to the heady days of early '08, I've been spending the last few months experimenting with an MnO2 anode aimed at perchlorate production. Rather than try to coat etched Ti directly or via the Co2O3 interface layers, I decided to thermally coat some MMO mesh as it is so readily available now.

I re-examined De Nora et. al's (Diamond Shamrock) 1978 US Patent Number 4072586 which among other things mentions applying thermally decomposed coats of beta-MnO2 over thin layers of RuO2.TiO2 on Ti (aka MMO). Beta-MnO2 is apparently isomorphous (rutile structure) with RuO2 (and TiO2) and thus bonds well to the MMO surface. In particular my attention was drawn to column 5 (lines 22 - 54), which mentions the suitability of beta MnO2 for perchlorate production, especially when enhanced with up to 5% As, Sb or Bi (actual element not specified).

Indeed the thermal beta-MnO2 does indeed bond well to the MMO coating and will form a thick, hard, crusty coating. It will even bond directly to non-etched oxide coated Ti, because of the rutile structure, but will of course be non-conducting.

Because of the size, instead of dipping the anode in the coating solutions, I used painting and eventually a spray technique. For mesh material, spraying is ideal as it is easy to coat all surfaces of a complex electrode assembly. A small (30 ml) plastic perfume sprayer proved ideal.

For thermal decomposition I used the same hot air gun technique as described earlier. Because of the larger electrode size I used a larger diameter tube and mounted it on a stand, otherwise the set-up was basically the same. The sprayed on coating was dried over the turned down hot air gun, this prevents drips and runs. The electrode was then baked for 10 mins at about 380 oC. Initially 25 coats of Bi-doped MnO2 were applied.

MnO2coat.jpg - 32kB
Crusty, black MnO2 thermal coating over MMO dual anode assembly.

Stock Solutions:

Mn(NO3)2 - made from pottery grade MnCO3 (31g) and 68% nitric acid (50 ml). This should fully react, may need a little more depending on purity of MnCO3. Solution was filtered and made up to 100 ml, it contains 48.25g Mn(NO3)2 or 14.8 g Mn.

Bi(NO3)3 - crystals made by dissolving Bi metal in 68% nitric acid (see thread). 6g of moist (nitric acid) Bi(NO3)3.5H2O crystals were placed in a small beaker and covered with 20 ml 68% nitric acid, diluted to 40 ml with water and stirred until dissolved. This solution was made up to 50 ml with water in a volumetric flask and contains about .0635 g Bi / ml.

Co(NO3)2 - crystals made by double dissolution of CoSO4 and Ca(NO3)2 or reacting CoCO3 with 68% nitric acid (see thread). 10 g of moist crystals (Co(NO3)2.6H2O) were dissolved in about 25 ml of water and made up to 50 ml in a volumetric flask. This solution contains .0405 g Co / ml

Dipping / Brushing / Spraying Solutions:

These are loosely based on Pat. #4072586, but are by no means definitive. They are just what I came up with for initial tests.

Pure MnO2: 16 ml of the Mn(NO3)2 stock was transferred to a 50 ml volumetric flask, along with 5 ml of isopropyl alcohol, and made up to 50 ml with water.

Bi doped MnO2: 16 ml of Mn(NO3)2 stock was transferred to a 50 ml volumetric flask, along with 1 ml of the Bi(NO3)3 solution (.051 g Bi) and 5 ml of isopropyl alcohol and made up to 50 ml with water. This solution is roughly 50g / litre Mn with 1.3% Bi in MnO2.

Co doped MnO2: 16 ml of Mn(NO3)2 stock was transferred to a 50 ml volumetric flask, along with 3 ml of the Co(NO3)2 solution (.121 g Co) and 5 ml of isopropyl alcohol and made up to 50 ml with water. This solution is roughly 50g / litre Mn with 3.0% Co in MnO2.





Some results with the MMO/MnO2 anode.

Xenoid - 14-3-2010 at 17:53

I'll be the first to admit I have been less than scientific in testing this anode. Hopefully, because it's so simple to make, others will have a go at evaluating it's performance as well. From the earlier work with MnO2 anodes, I knew they would make both chlorate and perchlorate, I really wanted to test their practicality in this new configuration.

Assembly.jpg - 32kB
Electrode assembly, note 3 titanium cathodes and 5mm spacing!

All testing has been carried out in a 1 litre cell.

1. The anode assembly along with 3 Ti cathodes (5 mm spacing) was placed in a 100 g/L KClO3 solution (saturated at 30oC.). The pH was reduced by the addition of 1 ml conc. HCl to about 2.8 this in an attempt to shift the Mn stability away from the wide end of the MnO4- field (high pH) and into the region of maximum stability for MnO2. The idea behind this was to try and avoid the "Purple Haze" effect which plagued earlier efforts with MnO2 anodes. Sadly this had no effect whatsoever, and the cell turned pink within 15 mins. The cell was run at a conservative 3.8 V / 3.5 A, this limited the temperature rise to 30oC. The cell was run for 48 hours (168 Ah), no perchlorate was detected during this time. A little, brown hydrated MnO2 was deposited on the cathodes and the cell bottom and sides.

KClO3cell.jpg - 35kB
First assembled 1 litre test cell, note permanganate "Purple Haze" and MnO2 scum!

Thinking that perhaps the cell voltage was a little low for perchlorate production (industry use 5 - 6 Volts) I dismantled the cell and removed the close spaced cathodes and replaced them with a single Ti mesh cathode spaced about 4 - 5 cm away. This had the immediate effect of raising the required voltage to 5.7 V at 3.5 A. After a further 17.5 hours (61.2 Ah) in this new configuration there was still no positive test for perchlorate!

Disheartened, I tried an NaClO3 cell

2. The 1 litre cell was filled with 500g / L NaClO3 solution. The single cathode with 4 -5 cm spacing was retained and the cell operated at 4.8 V / 3.5 A. Cell colour was pale pink and a test for perchlorate was negative after 3 hours. The next day after 23 hours (80.5 Ah) a positive test for perchlorate was obtained.

Heartened by this, I dismantled the cell and added another 10 coats of Bi-doped MnO2 to the anode assembly, although it still looked in good condition. The electrode was reassembled with the original 3 Ti cathodes with 5 mm spacing, and the cell was connected to a new power supply and now running at about 4.6 V / 7.8 A. The cell was run for a further 68 hours (530.4 Ah). Positive perchlorate tests were obtained directly from the warm liquor.

3. The cell was dismantled and refilled with the 100 g/L KClO3 solution from earlier. The anode assembly was coated with an additional 5 coats of Co-doped MnO2. A single Ti cathode with spacing of 5 to 10 mm was used. The cell was operated at about 5.8 V / 9.5 A for about 21 hours (199.5 Ah), no perchlorate was detected.

4. The cell was dismantled and the anode assembly had an addditional 5 coats of pure (un-doped) MnO2 added. The reassembled cell was operated at about 5.2 V / 7.6 A for 21 hours (160 Ah), no perchlorate was detected.

5. Added 5 coats of Bi doped MnO2 to anode assembly and placed in a 300g / litre NaCl cell in an attempt to progressĀ all the way to perchlorate. The cell was operated at about 8 - 9 Amps. After about 6 days and 1188Ah the presence of perchlorate was indicated. This became stronger, and after about 12 days (2376Ah) the cell was shut down (pH=8.3). The anode still appeared to be in good condition (still plenty of coating).

6. Started a new 1 litre cell containing about 80g / L KClO3 solution, this was mainly to test if the pink colouration was generated with well-used (leached) MnO2 anodes. I used the anode assembly from the NaCl -> NaClO3 -> NaClO4 run. A pink colouration appeared in the cell within 15 minutes. I left the cell running at about 5.0V / 8.0A, after about 48 hours I got a positive test for perchlorate (384Ah).

7. I made 4 identical test strips of MMO coated with 5 coats of pure MnO2, 1.3%Bi/MnO2, 3.9%Bi/MnO2 and 3%Co/MnO2. I carried out some electrical measurements with these anodes in NaClO3 solution, but there was no obvious difference in their performance.

Summary: Poor man's lead dioxide!

Pros: Very cheap, readily available, non-toxic and easy to make. Easy and quick to apply to an existing MMO coating (5 coats in an hour). Coat seems to last quite well, and a few more can be added quickly before a run. Will make chlorate and perchlorate and will convert NaCl to NaClO4.

Cons: Contamination with pink MnO4- and brown MnO2. Not very efficient and require solutions to be highly concentrated. The low solubility of KClO3 means particularly low efficiency in this system.





[Edited on 15-3-2010 by Xenoid]

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