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Rosco Bodine
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Yeah electricity must be really cheap in Tibet or
wherever that translation came from  That
would be a whole lot of light bill and oven time .
Maybe it was cold in the lab and such an experiment
became a scientific mandate as a countermeasure
for prevention of cryogenic castration .
I got some more articles requested that are relevant to
these type coatings . Found out you can't mix the
tin oxides precursors with the cobalt spinel precursor
because on baking the cobalt must have air exposure to
complete its oxidation , and tin oxide stops that oxidation before it completes . So you can use the layers applied
one over the other , but each must be baked separately
to completion before the next layer goes on . It looks like about 450C is the upper limit for the Co3O4 and past that
it decomposes to its separate oxides .
Also found out you definitely can combine electrodeposition methods with baking methods .
More later .
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Xenoid
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| Quote: | Originally posted by dann2
The DTO coat on Ti still going strong. (Approx. 120 hours) I put up the current density to hurry up it's destruction. The damm thing will still be
going at Christmas at this rate. 
It is making Perchlorate.
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@ Dann2 - What's the current density and voltage on that anode, you probably mentioned it somewhere, but I can't be bothered searching for it!
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jpsmith123
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Rosco thanks for posting that.
I wonder how the cobalt acetate solution became a sol-gel? They didn't go into any detail on that for some reason.
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jpsmith123
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It's too early to give up electrodeposition!
Solo came through on the papers I requested!
http://www.sciencemadness.org/talk/viewthread.php?tid=9319&a...
After reading these papers, my hope is restored!
Looks like cathodic deposition is the way to go. In fact the paper by Barrera et al. suggests to me that Beer's AC method might work.
I was able to get very excellent cathodic deposits of gray material (pure cobalt?) on titanium using concentrated cobalt acetate (much nicer than with
the sulfate) with a little acetic acid, at a low current density.
After reading these papers, I'm thinking that, had I bumped up the current density or tried a somewhat less concentrated solution, it may have worked.
I may also have been successful if I'd added a pinch of nitric acid or maybe just some ammonium nitrate.
Lots of room here to experiment.
Xenoid put away your heat gun and grab your power supply!
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Rosco Bodine
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more on sol gel derived Cobalt spinel
| Quote: | Originally posted by jpsmith123
Rosco thanks for posting that.
I wonder how the cobalt acetate solution became a sol-gel? They didn't go into any detail on that for some reason. |
No problem , I was looking up your references and came across some other related stuff which seemed pertinent .
I haven't even had time to read these articles through yet ,
so consider these as "this just in" possible interest items .
Probably a natural hydrolysis on dilution combined with air oxidation leads to a similar sort of mixed valency scenario
as applies in the oxidative cold soak process , where it is my theory anyway that an inorganic polymer is the intermediate .
Many of the polyvalent salts may follow this scheme .
Cobalt oxide films grown by a dipping sol-gel process
Enrique Barreraa, , , Tomas Viverosb, Alejandro Avilac, Patricia Quintanad, Miguel Moralese and Nikola Batinae
Abstract
Cobalt oxide thin films were prepared by the dipping sol-gel process, using two different inorganic precursors: cobalt chloride and cobalt nitrate
salts. Also, samples with a different number of dipping-annealing cycles (3, 5, and 7) where prepared. Composition, structure, surface morphology and
optical properties of such films have been characterised by means of X-ray diffraction, differential thermogravimetric analysis (DTA), transmittance
spectra and atomic force microscopy (AFM). The results show that starting from distinct precursors leads to different properties: film water contents,
surface roughness, crystallite size, total film transmittance, absorption coefficient and refractive index. Absorption coefficients higher than 104
cm−1 where found for all the samples. Refractive indices vary from n ~ 1.9–2.8 in the near infrared region. Our study shows that using a
relatively simple preparation method like the sol-gel process, cobalt oxide films with specific properties, can be made.
[Edited on 7-12-2007 by Rosco Bodine]
Attachment: Co3O4 Sol-gel derived Thin Solid Films 316 (1999) 138-143.pdf (805kB)
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Rosco Bodine
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Electrodeposition of Co oxides
A new cobalt oxide electrodeposit bath for solar absorbers
Enrique Barreraa, Ignacio González, b, , and Tomás Viverosc
Abstract
A study was carried out in a Hull cell in order to optimize the deposition conditions of cobalt xide (black cobalt) in an electrolytic bath, which
uses cobalt nitrate for direct obtention of black cobalt. Thermal stability of the material was surveyed on several samples of black cobalt prepared
on stainless-steel with a thickness of approximately of 2.5 μm. It was found that the optical properties change, in respect to the initial
values, with time of treatment until an equlibrium is reached. This equilibrium depends on the substrate and the temperature of the treatment used.
[Edited on 7-12-2007 by Rosco Bodine]
Attachment: Solar Energy Materials and Solar Cells 51 (1998) 69-82.pdf (621kB)
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Rosco Bodine
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Pyrolytic decomposition of Cobalt Nitrate
On the thermal decomposition of some cobalt hydroxide nitrates
L. Markov, K. Petrov and V. Petkov
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1040 Bulgaria
Abstract
The thermal decomposition of cobalt hydroxide nitrates of single and double layered lattice type has been studied. It has been shown that both types
of compounds decompose to oxide spinels, passing through stages of partial oxidation to intermediate Co(II)-Co(III) oxide hydroxide nitrates. The
observed differences in the stoichiometry of the final oxide products have been associated with the lattice type of the initial hydroxide nitrate as
well as with the decomposition mechanism.
Attachment: Thermochimica Acta Volume 106, 15 September 1986, Pages 283-292.pdf (735kB)
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Rosco Bodine
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sneaking suspicion about polymer thickening
Possibly just putting an airstone into a stirred solution
of these polyvalent capable materials and letting them
aerate for awhile is all that is needed for the gradual development of a sol-gel system . A bit of ammonium hydroxide and/or H2O2 might accellerate
the process ,
if it was a very dilute and gradual infusion .
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dann2
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Hello,
Current density is low on my DTO anodes.
30mA per square cm for first 100 hours or so. I have double this to approx. 60mA now going ok.
Voltage was rock steady at 5 volts at the lower corrent density.
It was about 6 volts at 60mA per square cm. The voltage is going up now a small amount. Dont know if it the andoe starting to fail or the fact there
the cell is becoming a finished Perchlorate cell.
BTW Magnetite is a reverse spinel, not a Spinel. It is important to get our facts right. :-|
Dann2
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Rosco Bodine
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It wouldn't be any surprise if there is a "breaking point"
current density operating limit which is applicable to any of these anode coatings . Staying below that limit ,
the anodes may last for months to years , and going
above that limit they will crap out pretty quickly .
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jpsmith123
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Well I don't yet have all the chemicals I need to try the specific electrolyte compositions mentioned in the two papers, but in fooling around a
little bit I can see that the cathodically deposited films are much more sensitive to species type and concentration, current density, etc., than the
anodic depositions I've been getting.
For example cobalt acetate in 5% acetic acid solution plates out a really nice layer of firmly adherent cobalt, whose "brightness" seems to vary with
current density, whereas the layer deposited from sulfate solution, although adherent, looks like crap.
Anyway, I wonder if I should try adding some KNO3 to my acidified acetate solution?
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Xenoid
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In Search of the Holy Grail - Not!
Well my second anode didn't do too well in a perchlorate cell and has completely eroded away after 14 hours at initially 100mA/cm^2 and then
50mA/cm^2. Maybe I shouldn't have changed all those variables simultaneously! A methylene blue test indicates the presence of perchlorate, which is
encouraging, although initially the anode seemed to be producing a lot of bubbles and ozone!
@ jpsmith123 - Obviously a perchlorate cell can exert more force than anything in the known universe!
The first anode still seems to be running OK in the chlorate cell.
| Quote: | Originally posted by Rosco Bodine
It wouldn't be any surprise if there is a "breaking point"
current density operating limit which is applicable to any of these anode coatings . Staying below that limit ,
the anodes may last for months to years , and going
above that limit they will crap out pretty quickly . |
Well, I think to be practical, 50mA/cm^2 is a lower limit, with 100mA/cm^2 desirable!
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Rosco Bodine
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The cell pH is probably a factor too especially after
a cell has been running for awhile .
The spinel could turn out to be just a dandy one shot interface coat , and require sealing with tin oxide , and then a wearing coating of some sort .
Anyway , by observation of the very low cell voltage , it is at the very least a damn good interface coating .
Looking at the anode , it still has that "stained" appearance , and I'm wondering , was it passivating
with voltage rise when you pulled it .....or did you pull it because it was looking naked ?
I'm thinking if it isn't passivated , then what you have done is to electrolytically scrub off the softer stuff , and get the anode ready for a baked
on DTO sealing layer , as opposed to being back to square one .
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jpsmith123
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Xenoid this might be a good time to try the electrodeposition method one last time (cathodic electrodeposition, that is).
You already have cobalt sulfate and nitrate lying around. If you can get some boric acid, you could try the method of Barrera et al. (of course they
claim it works best with some cobalt chloride added, too, but it also works without, apparently).
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Xenoid
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Still off topic but...
Here's my pool chlorinator electrode assembly after cleaning the Na carbonate off with dilute HCl (the vinegar idea just didn't cut the mustard). This
model sells for about A$400 new. The outside surface of the two outside electrodes still has 100% MMO (multi-metal oxide) coating, the rest of the
electrode surfaces look to be roughly 75% worn out! It will be a bit difficult to disassemble because the top of the electrode straps and electrical
connections are embedded in epoxy. The plastic straps around the electrodes are also epoxied in place but should be removable. I think I will just
snip the electrode straps at the point where they enter the epoxy. I can then get an engineering shop to spot weld some additional Ti strap onto the
stubs to make them into usable chlorate cell electrodes. They can also re sandblast them so I can put a new coating on them like.... like.... like....
cobalt oxide
Anyway, 6 Ti mesh electrodes (200mm x 65mm) for nothing, can't complain about that!
@ Rosco - Yeah, the voltage was rising rapidly and it was passivating. I had another play around with it at high voltage and high currents. I didn't
get any useful information from the exercise, but I managed to generate a strange corrosion hole at one point about 4mm wide and ~.5mm deep in a VERY
short time. I've had to file the surface to smooth it over - bugger!
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Rosco Bodine
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cell electrolyte additives
It seems I may be absolutely wrong in what I
supposed about not needing additives to the electrolyte
when using a spinel coated anode .
This is very preliminary information , first hit in a search
for anything looking relevant to perchlorate plus spinel .
The patent concerns chlorate production , and says that
the chloride(s) of the metals comprising the spinel coating on the anode , should be used as additives in the electrolyte ,
and further that the brine concentration also has importance .
I would suppose that having cobalt chloride in the electrolysis
mixture would be protective of a cobalt oxide containing anode coating , by virtue of the common ion then shifting the equilibrium , so that for
cobalt to depart from the anode and enter solution , it would be "swimming against the crowd" of
other cobalt ions wanting to replace it . It makes sense ,
but how effective it may be I do not know .
US3329594
Another thing I have been checking is the Dow patents
which were a co-application and sort of overlap .
US3977958 and US4142005 are sort of part A and part B .
The first one focuses on use of organic salt precursors ,
and the later patent gets improved spinels using nitrate precursors .
One of the bimetal spinels which really raised an eyebrow
for me was the one conataining ~ 10 molar percent of
molybdenum . It is charted in the first patent but wasn't tested for an extended time .
This is similar to the bimetal spinel mentioned in one of the technical papers above which showed an improved spinel
was a bimetal spinel having a percentage of nickel ,
which was superior to zinc as a substituent with cobalt .
I am interested in these *bimetal* spinels because they are tougher and have better conductivity , but also because
I have an idea that subsequent layers of different spinels
*may* form a better bond with each other , by reacting and diffusing , due to their differing composition .
What I am thinking is it may be possible to increase the thickness of that "stained" layer which has a jewel like hardness , and usually resides
beneath a thicker softer coating of the monometal cobalt spinel , by starting with
a much thinner coating , just enough to form the interface ,
and then coming back over it with a different composition
spinel , the idea being that spinel reacts with spinel in an alternating layer fashion as the thickness builds .
I think its a coin toss whether it would result in a thicker solid solution sort of spinel stew at the boundaries between layers , or if it would
provoke crystallization , which might not be bad either . Only experiment would tell .
[Edited on 7-12-2007 by Rosco Bodine]
Attachment: US3329594 Chlorate production using spinel anodes.pdf (187kB)
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Rosco Bodine
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summary of previous information
Providing some logical continuity here , is helped by
referencing a *perchlorate* related patent , which
was the genesis of my own interest in spinels .
| Quote: | | The anodes of the present invention are also particularly well suited for the electrolytic production of perchlorates |
It is a beta MnO2 related Diamond Shamrock patent US4072586 (attached)
whose first reading six months ago led to my interest in cobalt spinel , first as a catalytic additive for baked MnO2 coatings , but later discovering
that the Cobalt spinel was also useful for an interface layer on the Ti substrate itself .
This was published by the Dow patents but also confirmed independently by US4115239 . This was the patent which
used a titanium bronze as a modifier oxide , bonded with
cobalt spinel directly to a titanium substrate , which correlates with the in situ formed "modifier oxide" of the
Dow patents , and parallels the Beer patents , but using
the cobalt spinel as a cheap substitute for precious metal oxides . Zirconium is a good modifier oxide but is not a commonly available material .
However , according to the original MnO2 patent which
started this pursuit , modifier oxides for the MnO2 baked coating , include as in situ precursors Pb(NO3)2 , or as
*Tin Nitrate* , along with up to 5% Co(NO3)2 , serving
a similar purpose as "modifer oxides" .
And all these materials are *isomorphous* upon baking
so then all should form the reacting and bonding layer
interfaces which lock these coatings together forming
a multiple metal oxides anode having isomorphous diffusion boundary spinel layer interfaces stacked all the way down to the Ti metal substrate .
Theoretically it should all lock together like layers of hot melted glue .
And by using the nitrate of tin , it is possible that sufficient
oxygen would be present for the full development of the cobalt spinel , in which case there could be mixed precursors
for both stannic oxide and cobalt spinel , especially with
lead nitrate also added , as there is a surplus of oxygen
present in that mixture , removing atmospheric supplied
added oxygen being required for the formation of the cobalt spinel on baking . This should also enhance the consistency
of the coatings which are built up as a wearing outer layer ,
since the chemistry is present in the mixture for anaerobic
reaction , the composition would be consistent through the entire depth of the coating , no matter the thickness or how many coats are applied .
Alcohol solutions are used for
these precursors , and in the case of tin nitrate , that may be
essential as the salt hydrolyzes in water . There is no extensive description nor examples for the tin component
in the patent so more information about this is needed ,
although it is not an essential component of the MnO2
baked coating .
For the interface spinel an electrodeposition of MnO2 directly onto etched Ti , followed by baking the electrodeposited MnO2 layer did *not* produce
succesful anode
coatings . But applying alcohol solutions of the nitrate
and baking did evidently produce working interfaces of a Manganese Oxide and Ti Oxide bimetal spinel . The
best result was on Ti alloyed with 1.5% Co alone .
A parallel may exist here for the cobalt spinel , where
baking of the nitrate precursor produces a conductive interface which is lasting , but baking of an electrodeposited oxide does not result in a
durable interface . The particular alloy used for the interface may also have signifcant bearing
on the durability of a cobalt spinel baked interface coat ,
when it is used "as is" without some further wear coating .
Without detailed results specified for a particular commercial alloy , this is an unknown . To get beyond this uncertainty ,
for our pursuits the deeper the substrate interface is buried under protective coatings , the better .
The electrodeposited Cobalt suboxide might still work
as a wearing coating if it was applied to a Ti substrate
which first had a baked interface . It might be useful
to use the electrodeposition as a layer thickness building
method , alternated with other materials , baked or also
electrodeposited , in some alternating combination .
But I am suspecting at this point that the first interface layer
has to be bake developed from a chemical decomposition precursor , rather than from an anodically deposited oxide
then baked to "set" it . A cathodically deposited oxide
like jpsmith123 is looking at as an alternative for the
first interface , might work , but I wonder if there is any advantage to be gotten there over a baked coating from
decomposition of a nitrate , for the initial interface coating anyway . A hydrided or non-hydrided Ti substrate may
make a difference for electrodeposited Co oxide , later baked , or it may make no difference at all , working neither way , whether anodic or cathodic
deposition is used .
There remains the possibility also of electrodeposited PbO2 being applied over the baked spinels , incuding being applied
over the MnO2 . A labrynth of layers of differing composition conductive coatings may be required to produce a truly permanent anode .
At this point it seems , so far , so good . More experiments
will be needed to learn and/or prove what steps will
be required for creating a long life perchlorate cell anode .
Attachment: US4072586 Baked Mn(NO3)2 Manganese_dioxide_electrodes.pdf (156kB)
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jpsmith123
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Didn't Xenoid or someone already try MnO2 by way of thermal decomposition of Mn(NO3)2, or was it only electrodeposition that was tried?
What leaps out at me in patent #4072586 is the question: How well would straight beta MnO2 (from thermal decomposition of Mn(NO3)2) have fared if the
Ti substrate had been hydrided or given a controlled coat of TiO2 first?
Anyway the big picture I'm seeing here seems to be that you either need some kind of a "mixed oxide" coating on the outside, or, if you use a single
oxide like straight PbO2, MnO2 or CoO etc., then you need an intermediate layer.
As far as deposition methods are concerned, I've given up on straight *anodic* electrodeposition of anything, but, both the cathodic and AC
electrodeposition of single and mixed oxides still need to be investigated, IMHO.
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Xenoid
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| Quote: | Originally posted by jpsmith123
Didn't Xenoid or someone already try MnO2 by way of thermal decomposition of Mn(NO3)2, or was it only electrodeposition that was tried?
What leaps out at me in patent #4072586 is the question: How well would straight beta MnO2 (from thermal decomposition of Mn(NO3)2) have fared if the
Ti substrate had been hydrided or given a controlled coat of TiO2 first?
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Yeah, I did, I tried both! Your line of thinking is exactly what I have been considering over the last 24 hours. The cobalt oxide ( or some variation)
is looking quite good for a chlorate cell anode. But is not working too well for perchlorate. I've been thinking about revisiting MnO2 (god I hate the
stuff). As far as I can see the only good performers in a perchlorate cell are platinum, PbO2 and MnO2. When I was messing with MnO2, I was trying to
coat gouging rods. Now that I have Ti and know how to prepare it I've been thinking about having another go, since I have the Mn salts on hand. The
things I am going to try next are as follows; MnO2 plated onto etched and hydrided Ti, MnO2 baked onto Ti and then the same but on Ti with a baked on
layer of Co oxide.
Guys, I think this has all got to be kept relatively simple, (simple chemicals, simple procedures and simple equipment) and in perspective!
From my point of veiw an anode that would last long enough to do a single run from NaCl ---> NaClO4 would be perfectly adequate. It doesn't need to
last for hundreds of days, provided it could be recoated cheaply and simply as needed! If I could treat several Ti sheet/rod anodes simultaneously in
a morning, put them in a cell of several litres volume and produce a Kg or two of perchlorate over say a couple of weeks, that would be fine. How much
perchlorate does one need! Even if you are into pyrotechnics or model rocketry in a big way, surely that would be enough!
Note: Co oxide spinel anode in chlorate cell was still going fine when I checked it, coating was still 100% intact and electrical parameters stable.
The baked on Co spinel coating is bonding well, when it does fail, it is from wearing away from the outside, not flaking off at the interface, I think
this is a big step forward, at least from what I have achieved in the past!
[Edited on 8-12-2007 by Xenoid]
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jpsmith123
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Xenoid there are a couple of things that, IMO, really need to be tried ASAP, either to eliminate them from the list of candidate processes, or because
of the potentially very high pay-off if they work.
As of right now, I have no Mn compounds lying around, so I would have to order them.
I also need to buy a variac on ebay or somewhere as I presently have no variable AC source.
I wonder, do you have any Mn Sulfate lying around?
I'd like to see some AC electrolysis (after Beer) of a mixture of Mn and Co sulfates. IIRC, Beer's electrodeposited coatings involved AC and more
than one oxide, but he claimed that they were successful.
You're right about keeping it simple. That's what I want to do. The 3399966 patent was so compelling because of its simplicity. Even if an anode only
works for a few runs before failing, so what, as long as it's easy to make another one.
This is why I'm interested in electrodeposition.
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Xenoid
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Yeah! I have 5Kg of hydroponic Mn sulphate!
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jpsmith123
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Are you up to an experiment using two pieces of Ti as electrodes, driven by AC (preferably of variable voltage), using a mixed Mn and Co sulfate bath?
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Xenoid
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Yeah! Yeah! Where's that Beer Patent, I can't find it. I downloaded 3,234,110 but thats not the right one?
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Rosco Bodine
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It would probably be good to not overlook the hydrided Ti
with the low temperature baked MnO2 / PbO2 interface .
These are isomorphs also , forming an interface MMO which is a tertiary solid solution with TiO2 . This is similar to the idea with the spinel but
evidently develops at a lower temperature . The TiH2 thread gives the relevant patent .
Interesting that a similar mixture of Pb(NO3)2 with
Mn(NO3)2 is described in the US4072586 patent which
claims usefulness for perchlorate production . This suggests an MMO interface coating composition which may also have usefulness as a wearing coating
in perchlorate service .
These are very similar schemes for mixed metal oxides ,
the only thing really distinguishing about the spinels
being that at certain ratios , a distinctly crystalline
molecular compound may appear in the solid solutions
involving MMO materials which form polyvalent oxides ,
as is the case with these materials . As I see it , the
relationship in the mixture MnO2 with PbO2 is not
much different in principle or chemistry than what
is occuring with bimetal spinels , the significant difference
being only for identification of distinct compounds like
"double salts" which arise in the case of spinels ,
whereas the other solid solutions are only mixtures .
I haven't even checked the long list of identified spinels for these , and they may well be named spinels also , even though not specifically flagged
with that distinction in the patents which describe their usefulness . Indeed there are many many possible spinels which form over a wide range of
temperatures , and probably quite a few of them are of interest for interface materials with Ti and / or may have value as perchlorate anode coatings
. The
spinel(s) associated with cobalt and a few others are
noteworthy because of observed oxygen selectivity ,
and catalytic effect , similarly as for manganese dioxide ,
which seems likely an oversimplification in naming for what
is possibly a spinel there also .
None of these coatings should be left in open circuit condition , while still in the electrolyte . And I think
as a general rule if you are getting excessive gassing at the anode then your current density is too high . What exactly is excessive depends on cell
efficiency and the
ability of the anode to endure that condition .
PS: Sulfate reportedly is poison to the MnO2 baked coatings
[Edited on 8-12-2007 by Rosco Bodine]
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jpsmith123
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Here's one of the procedures I took from one of the patents; unfortunately I've forgotten which one. I will look and see if I can find others.
Example XVI
Two titanium rods were degreased and pickled and subsequently placed in a galvanic bath having the following composition:
100 cc. ethanol
100 cc. water
1 g. ruthenium chloride
10 g titanium chloride
and subsequently connected to a source of alternating current of 13 volts and a current density of 15 amp/m^2, temperature 20-30 degrees C., for a
period of about 20 minutes.
After about 20 minutes both rods were coated with a mixture of titanium oxide and ruthenium oxide, the adhesion of which was still further improved by
heating at 400 degrees C for 5 minutes.
The anode thus made is excellently suitable for use in various electrolyses at low current densities.
Edit:
This may be a generally useful method that may work for us. I think it's worth a quick test. The proportions of the various salts might need to be
experimented with a bit, but I can't imagine it being too critical.
[Edited on by jpsmith123]
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