More on PbO2 electrodes

DON'T USE IRON

Not wishing to start a long, high bandwidth, low content rant (would I do that ).......I would not recommend Iron as a temporary substrate.
Iron is mentioned (along with Cobalt) as a contaminant in Lead Nitrate plating baths as something you do not want. If you do not control pH very well (especially at the start when Iron is exposed) then some will dissolve into plating solution and pollute.

Dann2

Iron has reportedly (from numerous sources) worked for the purpose so why not try it instead of guessing that it won't work ..... just because it is simple ? Does it sound good to be true ?

I see it this way .....

If your plating electrolyte is low dissolved iron content initially , ( and it will be at a mildly acid pH , because Iron
salts will have low solubility , and likewise the corrosion of metallic iron at that low solibility for iron salts pH will not be favored ) .......
And you are using a stainless or copper or nickel or graphite cathode , there shouldn't be a problem . You see if metallic iron tried to dissolve into the lead salts solution , it would tend to deposit lead metal at the site of erosion . But that site being held at a reverse polarity and the anodizing voltage should result in PbO2 being formed there instead , sealing off the site . Obviously
the deposition of PbO2 is favored over the corrosion of the iron , so the iron is quickly buried beneath PbO2 ,
in effect being anodized by the PbO2 and thus protected from corrosion .

Beginning the plating at a neutral or just slightly acidic pH
the iron should not be attacked , especially if the degreased iron is connected to a live voltage feed outside
of the bath , so that plating begins at the very instant
it is immersed , the PbO2 should seal it immediately .

Perhaps some method could be used for primer coating the iron if that is desired .....but I would expect the initial plating of PbO2 to effectively seal the surface . If resorting to a nickel plating , then you may as well
use an aluminum substrate .

It is possible that you could make the iron cathodic for initial immersion so that metallic lead is initially plated onto the iron as a "strike" plating , and then after 30 seconds or so , reverse the voltage and establish the PbO2 simultaneously
from oxidation of that metallic lead strike with added PbO2
that is "incoming" from the electrolyte .

The surface of the iron could be converted to magnetite
if you wanted to go to the extra trouble , but I don't think that is necessary .

As for pH control ....that is going to be necessary anyway
with a bath containing lead nitrate . Only an acetate bath
for the alpha PbO2 would be capable of self-buffering to
any reasonable extent , perhaps using an added component like sodium acetate or ammonium acetate . With a mineral acid salt of lead , and lead being plated out , the pH will rapidly go highly acidic in the absence of some pH control and that variation is known to produce an inconsistent and lowered strength deposit of PbO2 .

Pickling and Pretreating the iron with chromic acid has been reported for iron to be plated with PbO2 from an acidic
lead sulfamate bath .....so here's another industry reference
concerning plating of PbO2 onto IRON


[Edited on 15-6-2007 by Rosco Bodine]

Attachment: US2430304 PbO2 on iron group metals from suphamate bath.pdf (118kB)
This file has been downloaded 792 times

In-situ PbO2 plating again!

Some chromating methods of interest

A known conductive chromating for aluminum

This is interesting

DTO coated Ti

I know titanium is expensive to experiment with
so maybe some rods and test tubes would be the best way to go for economy of many coatings test scenarios .

The simplest "combination" titanium dopant system I found using Tin compounds was a 70-30 mix of tin chloride - tin fluoride . See US5756207 , US5683567 , perhaps also US4510219 , and US2564707 .
The tin compounds convert to oxides during baking ,
with the fluoride functioning as both a flux and a dopant
for the tin oxides as well as the titanium oxide boundary layer .
The tin oxides doped with fluorine have about three times the conductivity of graphite or about the same conductivity as PbO2 . Now ....if only it is an non-polarized ohmic resistance , then you're in business


I apologize for recently getting completely ass backwards turned around on the polarity of the Schottky diode structure
that I had right at first , then reviewed and studied it carefully until I had it completely reversed in my mind . It must be age telling on me . Anyway I went back and deleted my "corrections" post concerning what I earlier had right in the first place when I first mentioned the Schottky architecture , the natural behavior of which is to block
anode current flow .

The whole idea of the doping of the titanium *is* to decrease the reverse breakdown voltage of that metal to semiconductive oxides rectifying junction , and make a chemically resistant barrier to any new growth of a rectifying layer - junction there .... which most definitely is in the wrong polarity for the conductivity of current by the anode .

The Ruben patent US2711496 which I attached a couple of pages back is still very relevant in terms of its detailing of the
etching of the titanium and the subsequent plating of alpha PbO2 . And it may also be relevant in its description of the
formation of a substoichiometric titanium dioxide layer which
is conductive via an electrolytic process . This layer is reportedly immeasurably thin in dimension and also reportedly porous ....so this may be an ideal material for
adsorption of dopants , or being subject to other techniques
to lower its resistance to anode current .

[Edited on 18-6-2007 by Rosco Bodine]

pH regulation

PbB2O4 , possible quick and easy TiO2 dopant

This is definitely a titanium dopant that should be experimented with to see what results .

In another thread ,
http://www.sciencemadness.org/talk/viewthread.php?tid=8612&a...
12AX7 and I were discussing spinels which may be semiconductors like magnetite and lead borate came up .

PbB2O4 m.p. 490-510C

Red lead Pb3O4 has a tetragonal crystalline structure .
It may be that the lead borate likewise has that tetragonal structure which would qualify it physically as a candidate material for use as a dopant in the tetragonal TiO2 boundary
layer , and the lead and boron ions both also qualify it as
a candidate dopant . Further , the lead borate has a low
melting point so this would enhance its performance in baking and possibly dissolving into the TiO2 to form a desirable fusion reaction at a relatively low temperature .
Lead borate is also a glass former ...and it may be formed from soluble precursors which may be applied to a porous substrate .

The idea is that plain boric acid and lead nitrate or acetate
could be used as dopants applied in sequence to a titanium substrate , perhaps one having a very thin substoichiometric
TiO2 layer already prepared as in US2711496 . Or perhaps
a freshly etched sheet of titanium could simply be rubbed with a paste of boric acid and a lead salt and then fired .
There could be different ways of applying this mixture of
lead and boron values so that lead borate is the resulting
residue .

Vanadium pentoxide and lead oxide similarly are dopants for TiO2 and form a relatively low melting combination , which likewise could be formed in situ from soluble precursors .

The same applies to Chromium and Phosphorous , which could use a dichromate and phosphoric acid as commonly
available precursors .

All of these combinations of dopant ions and/or oxides for increasing the *anodic* conductivity of TiO2 are listed separately and individually in US3948751 , but *not* as specific paired combinations ruled in or out , and all have relatively low melting temperature to develop a possible melt phase solution reaction with the TiO2 which is the goal .

Of course then you may come over the top of these with the
Tin Oxides doped with Antimony or Fluoride if desired to
create the conductive and chemically resistant layer if the
preceding materials are not themselves adequate in chemical resistance .

Anyway , the ready availabilty of the precursors for the Boron - Lead combination , and the Chromium - Phosphorous combination , and their low heat developing temperatures ,
would seem to make these two combinations definitely worth looking at as TiO2 dopants . What their performance may be I have no idea because I can find no examples of these combinations having been tested . That obscurity makes these possible combinations even more interesting as complete unknowns

Another possible TiO2 dopant combination from easily available precursors , but not listed in the above patent , is manganese chromite , MnCr2O4 . In fact , Mn is not even listed as a dopant ion for TiO2 and it may not be , but IIRC it has been mentioned in some other patents . I am not sure about the crystalline habit of this spinel being tetragonal either . But it is conductive and it is chemically resistant ,
and some data on it is in US6054231 , which describes a fuel cell application . Anyway this is another combination possibly worth looking at with an experiment .

[Edited on 18-6-2007 by Rosco Bodine]

Hello,

I refluxed 10 grams SnCl2 with about 70 grams Ammonium Moly in 1N HCl for about 6 hours.
There is a dark blue colour. When washed with Dietyl ether there is nothing visible dissolved in the ether. Should I evaporate the ether to dryness to see if there is anything there? ...or abandon

My patence with Ammonium Moly + Tin Cl2 is wearing thin.

Cheers,

Dann2

H2SO4 or SO3 will also probably evaporate out of the coating compounds at 500C, leaving just the mixed oxides.

You sure do come up with some good patent references.

[Edited on 6-20-2007 by Eclectic]

Quote:

Originally posted by Eclectic H2SO4 or SO3 will also probably evaporate out of the coating compounds at 500C, leaving just the mixed oxides. You sure do come up with some good patent references. [Edited on 6-20-2007 by Eclectic]

Hello,

You sure answer posts quickly

So you think we could use Stannous Sulphate instead of Stannic Chloride (5H2O or the dry stuff). Stannic Chloride is not easily got or made.
Perhaps Stannous Sulphate is just as difficult. It's back to the search engine for me...........

I think Rosco posted the patent first actually.




Dann2

The PbO process wasnt good' i added about 3 times more NaNO3 then needed and still not even half of the lead reacted(decided to continue the normal route) ill make some Pb(OH)2 from the nitrate and thats it.

About the lead subtrace anode, i will try it as soon as ill make all my reagents. ill coat the lead with lead dioxide (beta) with the sulfuric acid method. and then attach a cloth(of course i wanted to do so) and grow a massive anode over it.

About the two tanks, Any good method recommended(i only have about 1 literr of concentrated lead nitrate solution(and i dont want to make any more of it) also i have only one pump(if it wont dissolve ) the pump isnt contollable in any manner. i thought to use an flask with one pipe going to the bottom where ill have the lead hydroxide(oxide maybe? or any other suggestions)) and another pipe from the top will go back to the solution. near the plated anode(so the little water jet will also wash the bubbles away from the anode(thus i wont need a vibrator).

100g / liter HNO3 plating bath for beta PbO2

Hello Rosco,

My, you ARE going to be busy! There is enough material and possibilities here to keep a team of scientists going 24/7 for the next six months
Patent 4,026,786 does not mention making Chlorate or Perchlorate for the anodes, if that makes any difference. Only electro-winning metals.
It is a bit like US 3,634,216. This is also a high nitric acid bath but the Lead Dioxide is being produced for production of powdered Lead Dioxide only.

Cheers,
Dann2

cobalt oxide anode

Quote:

Originally posted by dann2 Hello Rosco, My, you ARE going to be busy! There is enough material and possibilities here to keep a team of scientists going 24/7 for the next six months

Patent# US3399966

Dipped and Baked Cobalt Oxides works too

See US6001225 for a similar cobalt oxide which may be formed from the same cobalt nitrate solution simply by a baking of the dipped substrate . A Diamond Shamrock patent US4243503 , Ex.#8 describes 80 g. of the hexahydrate of cobalt nitrate plus 20 ml of H2O as a dip and bake at 350C for 15 minutes produces the cobalt spinel Co3O4 , also useful as an anode coating . Natrosol thickening agent can also be used on these coatings to give a heavier buildup , and the cellulose soluble fiber burns out on baking , the same way as it does when used in ceramics glazes . Duh dip dip dip

Sheesh I don't know . With the price of nickel having gone up so much recently ...and cobalt being a byproduct of nickel refining ...I wonder if cobalt has gotten expensive also .

And yeah the coating should be , probably is , versatile on many different substrates , and is both a semiconductor *and* a catalytic material . The effect with MnO2 is probably similar as to what occurs with Bi and PbO2 . A coating having catalytic properties on top of good low resistance semiconductivity and chemical erosion resistance specific to the intended use is three wins . I wonder if Cobalt has usefulness as a dopant for Tin or Bismuth ? There are probably a lot of references concerning the cobalt containing spinels and cobalt containing catalysts . I haven't yet searched the literature to see what is there . Mostly what
I ever thought about with regards to cobalt is the pink to blue color change used for a hydration indicator on drierite ,
and as a minor alloying metal in some steels . Looks like it is good for a few other things as well

[Edited on 24-6-2007 by Rosco Bodine]

Solder Chloride Solution

I just dissolved the remaining 325 gr. of my 95/5 solder in 800 ml 31.5 HCl on a heading bath overnight, with 400 ml HCL added this morning. Evaporated for a while and decanted from the insoluble residue, I got 250ml of water white solution I'm assuming is fairly pure SnCl2. I was able to dissolve the insoluble residue in my previously made bright yellow SnCl4/SbCl3 solution with the addition of about 25ml 30% H2O2 in 50 ml 31.4% HCl. The yellow compound decolorized until the last bit of peroxide was added. I suspect it's SbOCl3, which shouldn't cause any problems, but if it bothers you you can heat the solution with a few snippets of tin to decolorize it. So now I have ready to go Sn/Sb oxide coating solution with 15-20% Sb, all from OTC materials. I can add some of the SnCl2 solution to reduce the Sb concentration if needed, otherwize I'll use it as a tinning compound for circuit board work and soldering.

Rosco, I like the bismuth dopant for a PbO2 overplate, also the alpha, beta PbO2 layering to reduce plating stresses. With an inert conductive substrate and good adhesion, this should work VERY well.

[Edited on 6-24-2007 by Eclectic]

magnetite related

My first PbO2 plating attempt

It turns out lead acetate does produce PbO2.

It's just that it produces a shitload of stringy dendritic crystals that would be beautiful if I wanted them, and razor-sharp if they were anything other than lead. I got this result before, but didn't notice that PbO2 formed because it's as black as the graphite anode I started with. I tried this with a dash of thiourea (to smooth out the cathode deposit), to no avail (at least at the current density I was running).

The reactions are:
Anode: Pb(2+) + 2 H2O --> PbO2(s) + 2 e- + 4 H+, Eo = 1.46V (this will be higher in an acetate solution, since it's rather hard to get 4M H+ from acetic acid...)
Cathode: Pb(2+) + 2e- --> Pb(s), Eo = 0.13V
Acetate spectates (though one could make the argument that peracetate is made and that produces PbO2, but I don't know what the potential is), and it appears OH- doesn't need to be involved, which makes sense, since this all works in acid solution.

As lead is consumed, acetic acid is produced (my remaining solution is stanky!), so lead hydroxide or carbonate (preferrably, well purified material) could be added. And that's all fine and dandy, up until the lead stringers short the cell and make it boil away (yes, last night I left the cell running; 16 hours later I find the liquid level about 30% of what it was, and the electrodes quite warm).

So why doesn't the lead metal plate out of a nitric solution? Or, does it, and no one talks about it? Seems to me it kind of HAS to happen.

I was running at somewhere between 2 and 4V. I didn't measure it at the electrodes. Current was probably a few amps. Cathode was some tangled copper wire.

Anyway, pictures, ah, yes, sure...

Tim

[Edited on 6-25-2007 by 12AX7]

In the above picture, you can clearly see the strained areas that delaminated from the graphite. The bottom end, due to gravity and evaporation of the solution, is about 1/8" thick. The surface over the wider area is lustrous, while the bottom end is botrydial with an average diameter of less than 1/32" (~1.5mm).

In this picture, the gray color is most likely the sky shining off the lustrous area. The material, overall, really is about the same black as the graphite it's on.

Tim

[Edited on 6-25-2007 by 12AX7]

Copper Nitrate saves Lead Ions

electrolytically etching stainless steels

more concerning baked cobalt oxides

Damn, Rosco. What am I going to do with all my solder chloride?
I'm going to have to dissolve some more scrap carbide in HCl with electricity now to get some Cobalt salts.

If anyone needs an acid solution of SnCl2 or SnCl4, I can report that dissolving any of the common lead free solders in hydrochloric acid seems to yield a fairly pure, water white solution of SnCl2. The alloying elements do not seem to dissolve without adding H2O2 and remain as a dense precipitate. It's not particularly tedious, just time consuming, as it takes about 12 hours to dissolve a 1lb wad of solder in 1 liter of 10-12N HCl at 90-95C (over simmering water bath).

Shapiro Supply on Ebay is a good source of titanium cut to size at about $10/lb.

HeHeHe , you can still use dopey(sp.?) tin as an intermediate layer if you can spare a couple of tenths of a volt overhead

Actually its a price that might have to be paid if the chemical resistance of the cobalt oxides doesn't pass tests in a perchlorate cell . But it looks like for at least the first layer onto the titanium the baked on cobalt oxide wins the conductivity contest .

Strange things can happen going from one semiconductor to another , so it is unknown what the additional interfaces with other metal oxides may do , and cobalt loves to form an assortment of mixed spinels , even having
three or four different oxides .....and lead and tin and bismuth are included in that group . But probably just keeping to the cobalt oxides should produce a serviceable anode . I can't find one single definitive
reference though , that describes any perchlorate production experiment using the cobalt oxides as
a working anode surface . So don't throw away the
HCl solution of 95/5 wire solder just yet . The cobalt
nitrate baked onto the outside of it could also be a working anode surface . Nothing like a layer cake for
solving transition problems .

Baked on manganese dioxide should go onto the cobalt oxide
with no problems . And the manganese dioxide has been tested in conjunction with cobalt doping , as useful for perchlorate production ( US4072586 ) although the layering was different ....I'll have to go back and review it , but at first thought it seems like it would work fine , and I was thinking about that combination originally when cobalt first came up .

[Edited on 26-6-2007 by Rosco Bodine]

Camping Gear As A Source Of Titanium

great minds think alike

@dann2
Those very patents were being read today as part of my
stroll along cobalt avenue to the intersection with titanium boulevard .
Some flashy ladies were there sporting zirconium and indium jewelry asking me if I wanted to party ,
said ruthenium might even be next and I said no thanks ,
I'll keep looking Maybe I'll try sitting at the intersection myself ,
playing a harmonica and holding a tin cup between my feet . Then I got to reading a later Dow Chemical patent
by the same inventors , US4428805 (attached) . Column 9 ,
Example 3 , Table 2 was especially interesting along the
top line where increasing current clearly showed the substituted Cobalt Zinc spinel Co2ZnO4 ahead , and the straight Cobalt Oxide Co3O4 pulling ahead of the exotics if the same trend increases to the triple or quadruple that current density where a perchlorate cell would be running . The exotics shine at the lower current density .....but crank up the amps and they fall behind the cheaper and less complicated materials . Bye bye ruthenium , ect.

Actually a couple of patents listed on your further references page provide similar examples of Cobalt Nitrate alone or
in combination with Zinc Nitrate being used to provide a superior conductive and non-passivation layer when applied directly to a titanium substrate and baked .
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

US4061549 and US4142005 on your page have examples that are included in the later patent US4428805 mentioned above and attached below . In the comparative example
on page 6 of US4061549 , a commerical titanium anode having a ruthenium doped titanium substrate tested slightly
higher voltage requirement than a Zinc Cobalt spinel directly deposited on titanium . The superiority of the spinel becomes even clearer from the current density chart in the later patent attached below .

[Edited on 27-6-2007 by Rosco Bodine]

Attachment: US4428805 Baked Cobalt Spinel Anode Coatings on Titanium Substrates.pdf (202kB)
This file has been downloaded 1067 times

may want to get some zinc also

I wonder how pure are the chems from ceramics shops?

cobaltous acid

I thought that possibly this cobaltous acid might make a good first treatment for a freshly etched and possibly hydrided titanium , as it might react at normal temperature with the bare titanium to form a desirable interface layer ,
as a sort of sealant and primer layer , possibly improving
the adhesion and conductivity at the interface of titanium metal to any following layers of oxides , whose precursors
may be applied and then baked to form the subsequent heavier layering of oxides . This would seem applicable
especially for the bimetal spinel formed from cobalt and zinc nitrates , but would possibly also benefit the mixed tin and antimony oxides .

The cobalt hydroxide reaction with hydrogen peroxide reminded me of the peracid formation which occurs with vanadium pentoxide , and I thought perhaps a useful
combined vanadium cobalt peracid or persalt complex , might also form under these conditions . Also the peracid of vanadium is known to form very soluble peracid complexes with higher alcohols like tertiary butanol , and this complex
or some mixed complex with cobalt might be possible .
These might also form soluble complexes with organic peroxides which may be capable of "doping" an initial interface layer on bare titanium *in the cold* , which would likely be evident as a colored film or haze on the metal .

This is something that was just an idea which occurred to me
and I can't find anything in searching that is related to this idea . But it seemed like a good candidate for an experiment , if only as an alternative to or in combination
sequence with some electrodeposition scheme for a first interface layer on the bare titanium .

Hello,

Seen this on amazon. If anyone has a copy feel free to post

Lead dioxide-plated titanium anode for electrowinning metals from acid solutions (Report of investigations - Bureau of Mines) (Unknown Binding

Dann2

Hello,

Do you mean more baking at a higher temperature?

I tried baking for half an hour. This made no difference.

I wheeled out an oxy propane torch and heated Ti coated strip watching it as I heated. The 'coating' did not go black.

Think I will have to go back to basics with Tin metal + Chlorine gas and Antimony Metal + Chlorine gas.
I may be able to make SbCl3 using HCl + Metal.

The solution I am using has far more HCl, (and no alcohol) than the patent. Would this make a difference?

Alan also suggested I may need a convection oven to carry away decomposition products and heat up the Ti quicker etc.
The oven I am using is a very simple homemade affair. No sealed but not a convection oven by any standards.

Dann2 and getting more



[Edited on 15-7-2007 by dann2]

[Edited on 15-7-2007 by dann2]

Pick a recipe and stick with it. You can't expect to make things work by blindly mixing items from column A,B,C,D,etc.

Advice tends to work (when it rarely does) only when you follow ALL the suggestions from a given source.

Make sure you understand the basic principles of what you are doing before you make arbitrary changes to the procedures.

(Sorry, I'm suffering frustration by proxy )

Look, you need a very concentrated solution of SnCl4 and SbCl3 dopant with enough HCL to keep it from precipitating oxides until you bake off the solvent. It's not going to make a bit of difference what your starting materials are, just what you end up with in solution.
These chlorides are VERY soluble. I have the equivalent of 3 moles SnCl4 in only 500ml solution with no alcohols added.


[Edited on 7-15-2007 by Eclectic]

Hello Electic,

You have enough solution there to coat an airport runway

I must admit I have 'messed around' quite a bit with the instructions etc. I am not too hot in the Tin chemistry department, or the Sb one either.

Will read what I have written and come back to you but I basically ended up with a solution of the SbCl3 and SnCl4 in HCl (+H2O2? or does it all go away when you boil the solution). I could not reduce the solution volume anymore as I was starting to get a ppt as I distilled off the acid so I painted and baked. I do not think this will work but perhaps there is something I have overlooked. My ratio is greater than yours. Mine is 23%Sb to 77%Sn.

I have since tryed SbCl3 (homemade) + SnCl2:2H20 (ebay)
in HCl and Iso-Propyl Alcohol with more success but not a workable undercoat.


Dann2

[Edited on 16-7-2007 by dann2]

DTO undercoat using SbCl3 + SnCl2:2H20

If ect. ect. includes my two cents worth .....

~10% Antimony oxides is the upper limit of dopant solubility in the Tin Oxides , and that amount is only attainable using different precursors than chlorides , along with a high temperature decomposable organic dispersant which holds the oxide and oxide precursor particles well dispersed and separated until above ~200C . When the mixed oxides layer forms it is a limited fusion , which then solidifies ....it is not the same as a completely melted phase of totally blended different liquified components ....as it never gets hot enough for that sort of blending . It is a vitreous glaze sort of layer
which forms and sets during baking , the same as an
enamelware sort of coating as is applied to steel cooking pots .

What you will get with so much antimony is a two phase deposit full of cracks and holes which will take twenty coats to overlap and fill in the pores and cracks .....
instead of the perfectly sealing level film of a conductive
glass in one to three coats . And the more undissolved antimony in the layer , the worse will be the conductivity and adhesion . So it is better to have too little dissolved completely than too much having most of it not dissolved .

Using mixed chlorides , try 2% antimony instead of ten times that amount .

I think your experiments will lead straight to the glass substrate experiments where optical quality coatings were the result . And no it's not back to that again ,
but more like *forward* to that again

[Edited on 16-7-2007 by Rosco Bodine]

Quote:

Originally posted by Rosco Bodine If ect. ect. includes my two cents worth ..... ~10% Antimony oxides is the upper limit of dopant solubility in the Tin Oxides , and that amount is only attainable using different precursors than chlorides , Snip Using mixed chlorides , try 2% antimony instead of ten times that amount . I think your experiments will lead straight to the glass substrate experiments where optical quality coatings were the result . And no it's not back to that again , but more like *forward* to that again [Edited on 16-7-2007 by Rosco Bodine]

Hello,

How do you figure that 10% is the max. solubility of Antimony Oxide in Tin oxide?

I will try lowering the Antimony to 5% (I will meet you half way + some )
When I say 5% I mean I will have 5% Sb, 95% Sn by weight in the initial Chlorides. I am calculating the Sn and Sb as if no other 'stuff' is in the coating. ie. no Cl-, or acid etc.
Does that make sense.? It will be (say) 0.95 grams Sn + 0.5 grams Sb, as SnCl2:2H2O and SbCl3.
I still have SnCl2 and my homemade SbCl3 as I did not use it all in the above coating attempt.
I accept the glass coating etc use smaller amounts of Sb than I have used. Surly DTO on glass is not directly comparable to DTO on Ti. Another Pat. that Electic quoted uses Pallidium (Chloride) mixed into the bakable paint. This uses low Sb too but it surly is not directly comparable to putting DTO (using Sb alone as the dopant) on bare Ti.
Perhaps I am missing some very obvious point.
When you say that 10% is the limit of solubility of Sb Oxide in Tin Oxide, is US 4040939 Example 1 not correct, not feisable, wasting Sb? It uses Chlorides. It uses (approx) 23% Sb.
Perhaps you have a Tin Oxide/Antimony Oxide phase diagram that you do not want to put in the public domain.............


Thanks for input.

Cheers,
Dann2

Well just had a look at the thread title and i noticed it is somehow related to PbO2 so i decided to ask a question about this.
Made a batch of PbO' in order to use it neutralize the HNO3 from the plating tank. How would you guys recomend me to do it. I am planning to pumb the liquid through another flask where it will be neutralized' but how can i store the PbO there without it running back to the main cell? Teabags? how can i make those teabags so they will hold the PbO inside and still allow it to react with the HNO3?

another question, more related to basic chemistry, what is the PH of a lead nitrate solution? it should be acidic, so i think there is no reason to maintain a certain flow through the neutralizer. If i just neutralize all of the acid that i can i should get an acidic Pb(NO3)2 solution and some traces of HNO3' just what i need.

so what do you say?

Quote:

I will try lowering the Antimony to 5% (I will meet you half way + some )

No no nooooo ....I'll say 0.85% is ideal for the chloride system , but only if you promise to double that and compromise at 1.7% , calculated as Sb2O3 weight in
the total oxides .....and let that be meeting me halfway ,
but only if you want to do it right for the first time
See the Corning patent which sprayed the coating onto a hot substrate for that one . I forget the number , but it dealt with a chlorides based precursor mix .

Here it is US2564707
http://www.sciencemadness.org/talk/viewthread.php?action=att...

Quote:

Perhaps you have a Tin Oxide/Antimony Oxide phase diagram that you do not want to put in the public domain............. Thanks for input.

Quote:

Originally posted by hashashan Well just had a look at the thread title and i noticed it is somehow related to PbO2 so i decided to ask a question about this. Made a batch of PbO' in order to use it neutralize the HNO3 from the plating tank. How would you guys recomend me to do it. I am planning to pumb the liquid through another flask where it will be neutralized' but how can i store the PbO there without it running back to the main cell? Teabags? how can i make those teabags so they will hold the PbO inside and still allow it to react with the HNO3? another question, more related to basic chemistry, what is the PH of a lead nitrate solution? it should be acidic, so i think there is no reason to maintain a certain flow through the neutralizer. If i just neutralize all of the acid that i can i should get an acidic Pb(NO3)2 solution and some traces of HNO3' just what i need. so what do you say?

I have only seen two patents concerning DTO on Ti for LD Anodes for (Per)Chlorate work??? Where are all the rest. I will surely quote them if they have high Sb....
This is pure speculation. The Corning glass works may be full of spongers too



And now I am going home to try a 5% Sb + the rest Sn coating. Then a lower Sb% if that does not work.
I think I need to see my head shrinker............


Dann2

You should be getting doped SnO2 growing out of a SnCl4.(H2O)2 melt during the baking process with HCl being driven off.

Use only enough H2O2 to convert the SnCl2 to SnCl4. If a drop of TiCl3 solution does not stay blue, back titrate with SnCl2 and retest.

You didn't like like my explanation of SnCl2 +2HCl +H2O2 --> SnCl4 +2H2O when I gave it in one of the other related threads? Are you keeping everything compartmentalized in your head? Doublethink? We're WAY past 1984!

[Edited on 7-17-2007 by Eclectic]

@dann2

BTW , Corning glass works is a place where they work mostly with *vitreous* materials ....imagine that

I'll try to keep in mind that the doped SnO2 layer isn't a vitreous coating . It only deceptively appears to fuse into a perfectly clear glasslike material when it sinters and sets as a solid solution ....perfectly emulating in every parameter what would be thought to be a vitreous enamel like layer . Of course it cannot be everything it appears and and tests and is reported to be ,
since dann2 has established the impossibility of any depression of melting point for pure materials mixed with property modifying impurities Depression of melting point .....hmmm ever heard of it ?


Further , now you are citing US4361905 , which I posted
( once again probably ) four or five posts above on this page .......which is saying *exactly* what I have been trying to tell you .....that the SnO2 is the solvent portion
of the solid solution ( vitreous intermediate layer ) in which the other oxides are dissolved as dopants .....
whether it is the deliberately added Sb , or it is oxides
diffused from the substrate .....be those SiO2 or TiO2 ,
which are themselves dielectrics when pure , but dissolved by diffusion into SnO2 as impurity dopants ,
the otherwise poorly conductive SnO2 becomes a hundred to ten thousand times more conductive than
pure SnO2 . Typically such semiconductor doping is
done at levels of tenths of a percent to a few percent ,
*not* tens of percent . You don't have a solid solution doped tin oxide then , but a mixture of tin oxide doped to saturation , mixed with undissolved aggregate of excess
dopant solids which detracts from every quality about the intermediate layer which was desirable at a much lower percentage where the dopant quantity was well below saturation .....like 14% of saturation for example .

Your focus on the Sb content as being so crucial is nonsense .....it is the SnO2 that is the solvent , or
matrix into which the other materials diffuse , so to account for the upward diffusion of Ti oxides from the substrate , Sb would function as a competition solute ,
not as an enhancer of the Ti to SnO2 diffusion layer .
If the SnO2 is already loaded with more Sb2O3 than it can dissolve , then it can't interact very well as a diffusion layer for the Ti interface ....because it is already *saturated* with Sb dopant . It will be like trying to dissolve sugar in honey , because the SnO2 is already
thick with dopant . And BTW best conductivity is a very definite desirable parameter for the intermediate layer ,
and when the Sb dopant percentage exceeds ~2%
for a chlorides derived mixed oxides .....the conductivity
drops exponentially .

There is a possiblity I suppose of some tertiary eutectic effect
that could exist for the Sb / Ti doped SnO2 ...but that would seem unlikely , given the examples where SnO2 alone is used
and relies for doping only on whatever diffusion occurs indigenously from the substrate below and the spinel above .
The voltage data for the anodes having undoped SnO2 alone is a good indicator that very little added doping is needed . I would fully expect that a lower Sb content than they are using , would be much better . What I get from their charting is that the SnO2 used alone is dopant poor ,
and their ratio of Sb to Sn in the doped SnO2 is dopant overloaded .....they went above and below the optimum ,
but never tried to extrapolate from there by more experiments , precisely what the optimum doping would be .
That's where the Corning patent data becomes helpful ....
not conclusive ...no ....but giving you something more to go on .

Hey if you want a grungy poorly conducting pore and crack filled poorly adherent flaking off mess for your intermediate layer .....go ahead and follow the high dopant percentage model .

Or if you would prefer a highly conductive , optical grade coating ....then invest some confidence in the relevant data .

[Edited on 17-7-2007 by Rosco Bodine]

Quote:

Originally posted by Eclectic Snip You didn't like like my explanation of SnCl2 +2HCl +H2O2 --> SnCl4 +2H2O when I gave it in one of the other related threads? Are you keeping everything compartmentalized in your head? Doublethink? We're WAY past 1984! [Edited on 7-17-2007 by Eclectic]