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dann2
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Hello,
The Anodes sound like a bargain to me. A great investment no doubt.
But if I were to purchase one of them what on earth would I do with all my spare time?? 
Swede can be found here:
http://www.amateurpyro.com
I don't know when he posted last. He would be interested in an Anode I would be inclined to think. Perhaps not.
Any chance of a picture?
@jp
The following were painted onto etched Ti and baked at 480C. They all just give passivated Ti which would not conduct any current at all (not even a
decaying, slow (few seconds) pulse at the start).
The formula is the same or similar to the 'standard' formula for ATO that is used all over the place in patents and Journal Articles except the
Bismuth Chloride and Bismuth Nitrate was used instead of the Antimony Chloride. Ti was etched using HCl.
15ml Alcohol (distilled methylated spirits)
4cc 27%HCl
7.5 grams SnCl4:5H20 (lab reagent)
0.8 grams of 'liquid' Bismuth Trichloride (a liquid that contains 53.16%Bi (made as described below)).
[this is a 15% Bi / 85% Sn formula]
My ATO works OK with this (above) formula using 'liquid' Antimony Chloride made in a similar way to the 'liquid' Bi Chloride and therefor I presumed
it would work with the 'liquid' Bi Chloride. It does not.
The formula below was also tried:
15ml Alcohol (distilled methylated spirits)
4cc 27%HCl
7.5 grams SnCl4:5H2O (lab reagent)
1.6 grams Bi Nitrate (Enough Bi Nitrate to give a 21% / 79% Bi/Sn ratio.)
The above is too much Bi as I was aiming for 15% Bi. (bad calculation) but I do not think that is what stoped the
Anode from forming.
I also tried the method of using SnCl2:2H2O by rufluxing the liquid Bi Chloride with the Stannous Chloride for 5 hours (as per my page using
the ATO via SnCl2 method) but this did not work. I got passivated Ti when baked. The precursor became cloudy when let sit for 24 hours with quite a
lot of ppt sitting on the bottom (Bi Oxide?)
I also tried refluxing Bi Nitrate with SnCl2:2H2O but the Stannous Chloride reduced the Bi Nitrate and I got Bismuth metal (I presume it was Bismuth
metal and not Tin metal?) in the bottom of the rufluxing flask. I did not proceed any further with that precursor.
I will get back to the process this week and have another go at it using smaller percentages of Bi.
I could try putting on an ATO coat on Ti (easy to do) and put on 'BTO coats' on top of the ATO, but I do not think that simply going through the
motions of painting on a BTO precursor onto something (in this case an ATO Anode) will simply give you a working BTO coat. The Ti will not be
passivated but you will just end up with 'BTO powder' (no good) on an ATO Anode and the Anode will 'work OK' when put into a cell to test it. You
would need to test it in a Perchlorate cell to see if it is makeing Perc I guess.
If the above worked then you could simply paint BTO precursor onto say MMO but you may only end up with an MMO Anode with some BTO powder sitting on
the MMO and not really bonded/stuck to it in a meaningful way.
I could also try refluxing Bi Chloride (the liquid that I made) with Anhydrous SnCl4 + Amyl Alcohol as per US 3627669 (EXAMPLE 1)(see page). It's
using Antimony Chloride but perhaps Bi Chloride may work with SnCl4 (anhydrous).
To make a long story short it appears that you just cannot simply substitute Bi Chloride for Sb Chloride (I am using liquids rem, if that matters) in
the 'standard formulas' that I have been using for ATO and expect to get a working BTO coat on Ti.
The patent that put me going on the BTO is US272354. It does not go into detail how the BTO precursor solution was made(example 3). It just mentions
SnCl4 (does not state the :5H20 stuff (a solid BTW) but seems? to suggest the Anhydrous stuff(a liquid BTW)) + Bi Nitrate and no acid in the
precursor.
Perhaps if I use SnCl4 (anhydrous) + Bi Nitrate + Alcohol it will work OK?????????????
I have no SnCl4 (anhydrous) only SnCl4:5H2O. It a bit of a pain to make involving dry Chlorine gas + Tin Metal.
Perhaps the patents bullshit????????
Reading a completely unrelated patent, US 7494583, near the bottom of columb 12, it shows a precursor formula for an Sn/Bi coating using Bi Oxide +
HCl + Anhydrous SnCl4.
Next precursor formula shows an Sn/Sb coating using Sb Oxide + HCl + SnCl4:5H2O.
It seems strange that the Bi doped formula specified Anhydrous SnCl4 and the other (Sb doped) uses the SnCl4:5H2O stuff???
Perhaps only the Anhydrous works with Bi. Seems a bit strange (Dann2 grabbing at straws?? as they add water to the precursor anyways).
The post is a bit of a ramble but I think it conveys my current position!
Does US 272354 demand Anhydrous SnCl4 for the BTO precursor formula???
_______________________________________________________________________
Making Bismuth Chloride:
Bismuth Trichloride from Bismuth metal + Aqua Regia
60cc 35% HCl was added to 12ml 70% HNO3. (an excess of HCl)
20.14 grams (use approx. this amount but weigh accurately) Bi metal consisting of pieces approx. the size of cubic mm's were added.
A very gentle heat was applied to hurry up the reaction. Brown fumes were released and these
must be vented outside as they are dangerously toxic. After approx. 5 hours the reaction slowed
and another 6cc of HCl were added to speed things along. When all the metal had reacted the
liquid was placed on an oil bath at 130° C in order to boil off solvent. When the liquid
was reduced to approx. half volume another 3cc HCl was added to make sure there was no Nitrate
left. The volume of liquid was reduced to approx. 12cc. This liquid was cooled and weighed and found to be 37.88 grams.
This give a percentage Bi of 53.16%. This liquid is used as the source of Bi when making BTO.
Regarding Aqua Regia (from SciMadness)
As long as you keep to the 3:1 ratio (3 of 35%HCl to 1 of 70%Nitric), (maybe add a little bit extra HCl to be sure) no Nitrate will form as it is
completely consumed according to;
HNO3 + 3 HCl ==> NOCl(gas) + 2H2O + Cl2(gas)
Nitrosyl Chloride is a gas that boils at -5.5C
__________________________________________________________________
Dann2
Attachment: US7494583.pdf (134kB)
This file has been downloaded 752 times
[Edited on 27-10-2010 by dann2]
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patsroom
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Hello Dann2
Your 100% right, there are those who prefer the hunt and then there are others that would whether just go to the supermarket and get the end
results.
[Edited on 27-10-2010 by patsroom]
[Edited on 28-10-2010 by patsroom]
I think Swede is lost. He has not been on APC since about 6 Jul of this year. I am starting to worry about him.
Also I can not seem to post my picture here I have one to post but I just tried twice and no results. I have posted over at APC a picture or two.
[Edited on 28-10-2010 by patsroom]
[Edited on 28-10-2010 by patsroom]
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patsroom
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My picture is over size 3.51 mb know wonder I can not get it to post sorry about that. but there are some at APC.
Pat
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not_important
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Try downsizing the photo. If you run Windows, download Irfanview and install. Load the image, Image - Resize/Resample will let
you scale it down to fit the 800 pixel max width, Save As a JPEG with a Quality setting of less than 70, which will give a higher degree of
compression - you might want to try several settings to chec the results. Or upload it to someplace like tinypic and post the resulting lin.
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patsroom
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http://www.amateurpyro.com/forums/topic/5220-chlorate-cell-s...
if all is right you can go to the above link and find the picture I have been trying to download..........Pat
[Edited on 28-10-2010 by patsroom]
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12AX7
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You posted a bitmap on the internet?
Open it in Windows Paint. Select Save As. Select File Type, PNG. Save a new file and upload it.
Tim
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dann2
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Hello,
I think Swede is probable busy flying airplains. He said on APC that he may be busy for a time (in some post or other.) I don't post on APC but read
it.
I downloaded the picture from APC, cropped out the actual Anode and reposted below as a JPG.
I'm no photographer BUT a picture of the Anode (not in the bag) would be nice. Go up closer to it and hold camera steady..........
The strap looks a bit thin for 50 Amps but I cannot see how thick it it. 50 Amps into that Anode would be a high current density.
Cheers,
Dann2
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jpsmith123
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Hi Dann2,
Firstly, with regard to your MnO2 anode experiments.
I've often wondered what would happen if some TiO2 was present with the MnO2.
In the early Beer patent, the TiO2 (or some other valve metal oxide) was considered a critical component for durability and performance. IIRC other
patents I've read (DeNora?) mention the use of TiO2 as a "stabilizer".
So I'm wondering, how hard is it to make or buy Titanium Nitrate? What would happen if you added some to your Mn(NO3)2 solution?
Who knows, you might end up with a really rugged MMO type anode with MnO2...maybe it will hold up in a perchlorate cell. Maybe DeNora didn't bother
with it 'cause of Beer's patents?
Now onto the #4272354 patent.
This is a mystery. The first time I looked at it, I thought that the wording of the first paragraph under example 3 was somewhat ambiguous, and that
maybe they were still using the MMO precursors too, with the only change being the substitution of the Bi Nitrate for the Chloride, for some reason.
But the text of the following paragraphs clearly seem to imply that example 3 has no MMO stuff.
So, based on your results, I'm tempted to say that the patent is simply wrong for some inexplicable reason.
This conclusion seems to be supported by the fact that the other patent you cited, 7494583, implies that an anti-passivation layer is necessary
between the Ti substrate and the SnO2-Bi2O3 outer layer.
If it were me, I would try, as a first step, putting the Sn-Bi oxide mix on over something else, just as a test to see - does it make perchlorate? If
it does, then it might merit serious further experimentation.
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dann2
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What temperature does Ti Nitrate decompose at. It would need be at or below 400C as you cannot (I believe) go above that temperature when making MnO2
Anodes.
Ti Tetrachloride is usually used when making MMO stuff and Ti02 is wanted in the coating. I don't know what temperature it need to go to to form TiO2.
I can try putting on a 'coat' of BTO on top of ATO. (or on top of MMO), but simply making up a precursor of BTO (using SnCl4:5H2O + Bi Nitrate (or
Chloride) + Alcohol + (perhaps) some HCl) painting and baking may simply give a coating of powdery BTO that not really a useful viable coating.
Anyhow I am currently looking for Anhydrous SnCl4 to see if that will work (for BTO) on bare Ti. (as per US 3627669, Example 1)
It's an ATO patent but this method may work with BTO.
Dann2
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Rosco Bodine
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Let me make sure I have this straight. The patent says an anti-passivation interface layer is required for a Ti substrate ???? ..... hmmmm ....now
there's a revelation huh, .....I mean, ........who woulda thunk it ?
Alternately to ruthenium....maybe cobalt or (even better) nickel-cobalt spinel
could be good for that "anti-passivation interface" for a Ti anode substrate.
Then, over the "anti-passivation interface" the patent says a sealing layer is needed ....another huge "revelation" huh.
How about a syrupy Pytlewski type polymer / or tin methanolate in methanol like the precursor used for the spun ATO fiber ? Or alternately .....
How about an ammonium bismuthate / ammonium stannate sol thickened with 100% hydrolyzed PVA which has a detailed process description ?
As for adding a Ti oxide component to a coating mixture, a Ti alcoholate might be useable in an anhydrous precursors mixture. It may be possible to
form the alcoholate of Ti in a similar way as is possible for making an aluminum alcoholate, via an amalgam. Pieces of freshly cleaned and etched Ti
are dropped into the anhydrous alcohol containing a small amount of HgCl2 and the Ti alcoholate should form from reaction of the alcohol with the
elemental Ti dissolved in the film of amalgam, the reaction continuing with evolution of hydrogen split off from the alcohol as it reacts, with the
amalgam dissolving more and more of the Ti as the reaction proceeds until the Ti is completely consumed and a few droplets of mercury remain as a
residue, along with any Ti oxide which may be byproduct of reaction with any moisture. The anyhdrous alcohol solution of the Ti alcoholate
can be decanted or filtered off from the residue. This Ti alcoholate may be miscible with other alcoholates of Tin and Bismuth for example or with
their alcohol suspended sols. I do not know if the titanium oxide component may
also form a stable hydrosol or peptized aqueous colloidal suspension, but it very well could form at least a temporarily stable hydrosol. A Ti
oxalate or tartrate or acetate, citrate are other potential possible precursors.
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jpsmith123
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As far as adding some TiO2 to the MnO2 is concerned, IIRC the only Mn compound known to decompose to beta-MnO2 is the nitrate, right?
So to add TiO2, I guess we have to find a soluble Ti compound that thermally decomposes to TiO2 and is compatable with an alcohol solution of
Mn(NO3)2.
I read somewhere that Titanium Tetranitrate Ti(NO3)4, CAS 12372-56-4, is used to make thin films of TiO2 and that it's highly soluble. So it might be
a good candidate, but it seems hard to find and apparently it's hard to make?
I wonder if Titanium Ethoxide would work? Can it be bought inexpensively?
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Rosco Bodine
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The decomposition of many different compounds would lead to the oxide and the carbonate does it pretty easily. The nitrate probably decomposes most
easily to the oxide but many other compounds are also valid precursors. Tartrates and oxalates tend to have reducing properties during decomposition
because of the byproduct carbon monoxide during pyrolysis. In mixtures where the idea is to limit the oxidation state for the Ti oxide so that a
conductive suboxide or doped oxide (mixed oxide) is formed, then tartrates and oxalates, perhaps acetates and citrates or chelated metal compounds
could have usefulness. Alcoholates are used for similar reason, the carbonization during pyrolysis tends to have a reducing effect on the deeper
layers while there is complete oxidation of the surface layer from atmospheric oxygen. Nitrates definitely can be made from
Zirconium, Titanium, Tin and Bismuth but these type compounds are unstable and highly reactive ....you don't just dissolve them in water and get
solutions of the nitrates but you get products of hydrolysis, precipitates or sols depending upon pH and concentrations, temperature, ect. Dissolve
in alcohols and the reactivity leads to alcoholates or "alcholosols" colloidal suspensions of the oxide in the parent alcohol. Some such systems may
be only quasistable transiently stable precursor "paints" which won't keep for use longer than minutes to hours, they may be "reactions in progress"
from the moment they are made, as opposed to being stable solutions. The mixed precursors may react with each other as well as undergoing
decomposition by themselves or interaction with the solvent.
It is precisely this problematic instability, reactivity and interactivity which is causing problems with formulating precursors mixtures evident in
some of the described experiments.
If titanium nitrate forms a stable solution with water, then it should form from
amalgamated Ti metal in moderately diluted HNO3. The amalgam should nullfiy
the usual TiO2 passivation layer, and the HNO3 would react with the nascent
Ti(OH)2 simultaneously oxidizing the Ti with formation of the Ti(NO3)4.
However only TiO2 would result from the pyrolysis of the oxidized +4 Ti ,
therefore the nitrate could not be expected to operate as precursor for any
content of desired TiO or conductive Ti "suboxide", as would be the case for
an Ti salt of an organic acid in an anhydrous solvent.
Amalgamated Ti in a glycerin solution of Bi nitrate could also lead to compounding between the Ti and the Bi or likewise for interactivity of their
alcoholates, forming Bi titanate or Ti bismuthate (exist?) .....so there is no simple predictability what will or may occur. There could even occur a
"gilding" of metallic bismuth/titanium/mercury "alloy" as a penetrating surface layer attaching to the Ti substrate, becoming sufficiently loaded
with Bi that the reaction then stops at an undetermined depth. Such a substrate upon baking might form a viable anode substrate, after volatization
of the mercury and pyrolysis of the mixed Bi and Ti oxide "interface" layer which may be an effective anti-passivation layer. Similarly other doped
Ti oxide using other metals for the "gilding" alloy could also lead to anti-passivated Ti anode substrates upon pyrolysis.
All of those "unknowns" should have dann2 running towards
ammonium stannate - ammonium bismuthate - PVA as a precursor mixture having validity and stability.
That would presently be the most promising "problem solver", unless of course the goal here is "redefining the problem" rather than solving it.
Sorry, I just get the feeling I am talking to a brick wall. Some patents are better than others at revealing anything about the chemistry involved.
Coating precursors that are not described in detail and are not claimed as a specific process and formulation by a patent does not necessarily mean
that the more pertinent subject matter of the patent has no validity, the precursors for the coating being beyond the scope of the subject matter of
an invention being covered by the patent claims. The chemistry of the precursor materials is a technical aspect which has greater importance than does
an oversimplified description of the precursors which is found in any patent that may be deliberately vague about exactly how the coating mixture was
prepared.
[Edited on 30-10-2010 by Rosco Bodine]
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jpsmith123
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I can't seem to find out much about Ti Nitrate, e.g., at what temperature does it decompose.
And I couldn't find it for sale anywhere off-the-shelf except in some ultra high purity grade at Sigma-Aldrich, IIRC.
I did read that TiO2 will dissolve in hot HNO3 so that's a possibility.
As far as Ti alkoxides are concerned, that might be the way to go. I don't have any of the patents in front of me, but I think Beer used them in his
examples.
Anyway, according to Wikipedia:
"Many alkoxides can be prepared by anodic dissolution of the corresponding metals in water-free alcohols in the presence of electroconductive
additive. The metals may be Co, Ga, Ge, Hf, Fe, Ni, Nb, Mo, La, Re, Sc, Si, Ti, Ta, W, Y, Zr, etc. The conductive additive may be lithium chloride,
quaternary ammonium halogenide, or other. Some examples of metal alkoxides obtained by this technique: Ti(OC3H7-iso)4, Nb2(OCH3)10, Ta2(OCH3)10,
[MoO(OCH3)4]2, Re2O3(OCH3)6, Re4O6(OCH3)12, and Re4O6(OC3H7-iso)10."
So is it possible that Dann2 could just take his Mn(NO3)2 in alcohol solution, stick a piece of Ti in it, and anodically dissolve the Ti?
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Rosco Bodine
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The amalgamation method which I suggested would possibly be a simpler, easier and more direct approach for Ti isopropoxide, which has
similarities in its chemical properties with Al. I have been able to find nothing so far in early searching for any description of Ti amalgamation,
so this idea may or may not work. No experiment has been done by me to confirm this idea, Ti is a peculiar material in its reactivity. Under very
specific conditions it can be reactive, and when the conditions are changed even slightly it is passivated. So the help provided by an electric
potential
to force it to react may ultimately be required. Referencing the industry corrosion data for Ti shows a 3% HCl at boiling point attacks Ti very well,
but increasing to 5% HCl the rate of attack is reduced forty fold towards passivity, and a similar effect occurs for reduced strength below 3% HCl.
Therefore, there is a kind of 3% window concentration for the HCl where the attack of the Ti is effective according to the industry corrosion data
found on the following page.
http://www.titaniumprocessingcenter.com/titanium-corrosion-d...
If (and that is a big "if") the Ti can be amalgamated in an aqueous solution, it would probably be a good starting point to try etching the Ti with
boiling 3% HCl and adding HgCl2 to the hot solution after the Ti has been etched for awhile by the 3% HCl. If the Ti does amalgamate, it should be
visible as an effect of mirroring and/or increased evolution of hydrogen. If the amlagamation is successful then the solution can be poured off
quickly and the isopropanol introduced for production of the isopropoxide, or dilute nitric acid may produce the nitrate. That's another unconfirmed
possibility. I have gleaned a bit more information about Ti amalgams and one patent stated that the solubility of Ti in Hg is low, on the order of 5%
and that the Ti is prone to "dewetting" by the amalgam. Also there are formed at high temperatures intermetallic compounds Ti3Hg and TiHg.
There are possible complications then due to a potential self-limiting effect of the attack of Ti by the mercury even when Ti is wetted, where the
amalgamation may not progress in increasing depth at a good rate. However, if the amalgamated Ti is high fired in an inert or reducing atmosphere, a
spongy porous sintered Ti surface structure
is left behind when the mercury vaporizes. This could be a potentially useful substrate surface treatment for creating a rough surface that would
retain dopants for the interface which could be left physically entrapped in the porous structure. Potentially this could be an ultimate kind of
surface preparation for a Ti substrate, where the surface is to a limited depth transformed into a rigid yet porous structure that is integral with
the solid Ti substrate.
The conventional and published descriptions for preparation of Ti isopropoxide involve reaction of TiCl4 with isopropanol.
The isopropoxide of Al forms very actively and vigorously from clean and etched Al in anhydrous isopropyl alcohol, to which some HgCl2 is added
(perhaps 1% to 2% the weight of the Al or Ti), hydrogen being split off from the hydroxyl of the alcohol as it is replaced by the Al, actually 3 of
the isopropyls per atom of Al. Ti should work the same way only there will be 4 isopropyls as a result of the +4 Ti versus +3 Al. Hydrogen gas is
evolved profusely and the reaction is exothermic, could even boil the excess of alcohol from heat of reaction, so a capacious vessel should be used.
The alkoxide is air and moisture sensitive. In fact there will be some insoluble precipitate of TiO2 possibly even as a gel from the reaction and
decomposition of some of the isopropoxide being formed until the alcohol present is rendered completely anhydrous, as there will always be some trace
moisture present in the alcohol.
Glycerin and ethylene glycol are other potential alcohols which may be useful. Bi nitrate forms an alkoxide with glycerin and with other polyhydroxy
alcohols which may possibly be a compatible dopant scheme in sol-gel processes for Ti alkoxide. The Ti alkoxide is going to be a lot more moisture
sensitive than the Bi nitrate / alkoxide. Lowering the pH with HNO3 could help keep everything in solution if a soluble Ti(NO3)4 does form.
Anyway, a much simpler approach which should work for producing an anti-passivation conductive interface of Co-Ni spinel and sealing that interface
with Bi doped SnO2 has been suggested by information gotten from a pretty extensive survey of the literature, broader than just the anode patents.
And given the fact it became evident a long time ago that the patents don't tell the whole story, I have more confidence in proposing a different
approach gotten from combining the specific information about compositions that are best for doing specific things.
It is like putting together a tactical rifle where the barrel may be made by Hart, the stock and bedding by Accruglas, the action by Sako, the trigger
by Canjar, and the micrometer mount by Buhler, and the scope by Nikon, and so on ....you put the parts together to build the system you want.
That spun fiber DTO patent gave me an idea that it may be possible to blend the fibers of DTO maybe 70% DTO fiber with 30% borosilicate glass fiber or
glass powder, perhaps blended in suspension in stannous fluoride, drained, dried, compressed at high pressure and sintered under high heat and
pressure into a ceramic / glass composite anode. There was some discussion about a ceramic substrate anode and this is a similar idea. Particles of a
catalytic material could also be entrapped and sintered into the fibrous structure.
Something like this could represent a new state of the art.
http://www.youtube.com/watch?v=hqzDqF1VF38&fmt=18 Glenn Miller tribute - Moonlight Serenade - Carly Simon
[Edited on 2-11-2010 by Rosco Bodine]
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dann2
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Some Ti info.
Attachment: titanium.pdf (420kB)
This file has been downloaded 1534 times
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dann2
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Manganese Dioxide on Ti
Hello Folks,
I have been running a number of MnO2 Anodes in various cell for the last month or so to see how they perform.
All Anodes consist of five coats (and five bakes) of the same MnO2 percursor solution (approx. 50% Mn Nitrate
solution in water) baked at approx. 390C on etched Ti.
One Anode had 2 coats of Co Oxide put on first.
All Anodes were run under similar current desity of 50mA per square cm and had a similar Cathode arrangment.
2.5 Amps into one litre cells with temp. in the twenties C.
I have come to the rather bizarre conclusion that the MnO2 Anode performs much better in Potassium Chlorate cells
compared to Na Chlorate cells. Also Co Oxide undercoat is not required and seems to be an actual disadvantage.
The MnO2 on bare Ti run in a Na cell (no pH controll) give 28% CE (current effeciency) and lasted 30 days.
The Sodium pH controlled Chlorate cell that I ran (still running actually) using MnO2 on bare Ti
give only 52% CE for the first ten days and has been going now for 28 days so far with more to go .
The Anode that had the two coats of Co Oxide as a first layer (+ five coats of MnO2 on top) had the shortest run time
of only approx. 20 days and give 26%CE in a non pH controlled Na cell.
The liquor coming from the Na cells was a rather ugly brown colour but most of this settled to the bottom after some
days but its very hard to pour off the liquid without stirring up the brown ppt. The liquid left had a yellow colour.
Any pink colour that did appear in the Na cells after a day or two of operation give way to the brown colour after approx. five days.
With my K Chlorate cell (non pH controlled) I am getting a high CE% (at least 56%, have still to dry the product that I have removed)
for the first 9 days of running. Lots of Chlorate on bottom of cell. The liquid is a very clear pink colour and there is little (but some)
discolouration in the raw Chlorate. This cell is still running.
Will run a pH controlled K cell when I get a free power supply.
Dann2
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avi66
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i bought a new 2 mmo anodes which design for chlorate manufacture, i want to use one of them as a cathode in my non-ph controlled k chloride cell ....
is it destroy the anode coating and i will stay with bare ti ? or is it work ? and if it work as a cathode, what is the anti-chlorate reduction
potential ?!
i got an idea of a process of easy manufacture mno2 anode....
if we take bare etched ti metal, put it in mn(so4) 90g 500ml water, 90c, 12ml conc h2so4, at current density up to 10ma/square cm, as in nurdrage
video, and then burn the thick mno2 electrolytic coat with heat gun at 380c, we will convert all the thick coat of mno2, to the beta-mno2 ... then we
will receive a thick strong coat of beat mno2 ?!
thanks for the helpers, hope to get your opinion on my technique idea of mno2 anode manufacture.
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dann2
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Hello,
A good way do find out how the Pb/Ag substrate would hold up in a Perchlorate cell (or Chlorate) would be to make a small amount of the alloy and cast
an Anode. Use this Anode in a Perchlorate cell and see how long it lasts. If it lasts quite a long time, like MMO or Tin Oxide on Ti then it will ge
OK for a substrate.
If it erodes like Graphite then it will not make a good substrate and will be comparable to Graphite as a substrate. It will need a perfect coating
of Lead Dioxide which is not good in the Amateur world.
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dann2
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Did you purdchase the Anodes or make them
I think MnO2 will strip off if used as a Cathode. The bare Ti is OK as a Cathode.
You cannot put on a thick coat of MnO2 using electricity (plating) as it peals off as Nurdrage said.
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avi66
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thanks for the information about the mno2 anode... now i will not try this experiment for nothing.
i bought some ruthenium based mmo anode, now i wonder how could i remove the coating, soo i will be able to use the titanium beneath as a cathode ?
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dann2
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Hello,
You can use MMO as a Cathode if you want as they use it as a Cathode in Bipolar cells in industry (cells where a sheet of MMO material is a Cathode on
one side and an Anode on the other side). It sounds like a terrible waste IMO. Purchase Ti as it should be cheaper than MMO and use that as a Cathode
or just use good stainless steel as a Cathode.
Keep Cathodes small and this will help to stop Cathodic reduction (or use additives).
BTW I posted the first post above in the wrong thread!!!!!!!!!! (O dear)
Dann2
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Xenoid
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All the pool chlorinator electrode assemblies from around here are now wholly manufactured from MMO. This is because they are all self cleaning now,
so that the electrode polarities are switched back and forth regularly to stop build-up on the cathode. This also simplifies construction and
inventory for the chlorinator companies as they don't need to worry about plain Ti electrodes.
I am currently running a 5 litre chlorate cell with an all MMO 10 element pool chlorinator electrode. I switch polarity two or three times per run at
which time any whitish "crud" that has built-up on the cathode immediately flakes off when it becomes the anode.
Incidentally, I now note most companies are switching over to solid plate electrodes rather than mesh, they last longer I guess.
MMO is now so cheap and common
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tnphysics
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Ti is corroded by:
-Strong base (forms Ti(OH)<sub>6</sub><sup>2-</sup>
-Fluoride + acid (forms TiF<sub>6</sub><sup>2-</sup>
-VERY strong acid + water (forms TiO<sup>2+</sup>
-Anhydrides of strong acids (same)
-Strongly acidic, highly reducing conditions (forming Ti<sup>3+</sup>
It passivates under almost any other conditions. The chlorate cell without pH control is probably the first such condition, as the pH can become very
high. With pH control, there should be no problem. Is this what has been observed?
[Edited on 31-12-2010 by tnphysics]
I LOVE science!
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avi66
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the mixed metal oxide anodes, corrode more as a cathode or a anode ?
[Edited on 7-1-2011 by avi66]
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dann2
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Hello,
Running some MnO2 Anode cells. There is a marked contrast between Na and K cells. Still running the K Chlorate (no pH controll). If the Voltage
accross the cell is anything to go by the Anode is going to last approx. 80 days. (5 coats MnO2)
A similar Anode only lasts 30 days in an Na cell and gives half the CE.
I cannot get the table to post.
Still to run a pH controlled K cell.
MMO will corrode more as an Anode IMO. I am beginning to wonder do those bipolar Anodes (picture way above from a guy who works in the industry) have
MMO on one side of the plate and perhaps bare Ti on the other side?
I had Ti corrode when I had Fluorine in a cell that had a Lead Dioxide Anode in it with the Ti exposed in places.
Ti will also corrode if a stupidly high Voltage is applied to passivated bare Ti.
I have never heard of anyone having Ti corrode in high pH chlorate cells. It does make a difference if you put the Voltage to bare Ti suddenly.
If you put a piece of bare Ti into a (say) Chlorate cell and connect (approx. don't remember the exact Voltages) 12 Volts to it you might well get
current flowing in places and erosion of Ti. But if you were to connect a similar piece of Ti to the power supply at 2 Volts and them raise the Voltag
slowly (say one Volt per sec) then you may have to go to 15 or 16 Volts before the corrosion starts. The TiO2 layer I guess gets a change to thicken
with the slower rise of V
"MMO is now so cheap and common "
 Shouldn't be allowed
Dann2
[Edited on 10-1-2011 by dann2]
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