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More on PbO2 electrodes

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dann2 - 15-6-2007 at 04:11

Hello,

There is a patent (would you believe) that uses a Lead Layer on top of Titanium. An Alpha Lead Dioxide layer is put on top of the Lead metal with Sulphuric acid (like you are doing). Then a Beta is plated on, from a Lead Nitrate bath.

There is no mention of using the anode in a Chlorate or Perchlorate application, only a Fluoride electrolyte.
I think that if the anode could be use in a (Per)Chlorate cell they would have mentioned it.
I think that the (Per)Chlorate cell is a very unfriendly environment compared to a lot of applications (including Chrome plating).

Patent here:


http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

Dann2

hashashan - 15-6-2007 at 13:11

Well i seem to loose any track of the discussion about coating PbO2 on metals. What would be the best metal(just not platinum etc. ) for deposition of PbO2 over it? The metal is only temporary substrace, it will be eroded off after the coating.

Rosco Bodine - 15-6-2007 at 13:54

IRON

jpsmith123 - 15-6-2007 at 15:16

Thanks for the info, Xenoid.

I hope it works, as we need a cheap and quick way to make some perchlorate; but even if it doesn't work, there are so many ideas floating around, it's useful to get the ideas that don't work out of the way, so as to narrow down the field of contenders and concentrate on something else.

DON'T USE IRON

dann2 - 15-6-2007 at 17:31

Greetings all,

Quote:
Originally posted by Rosco Bodine
IRON


Not wishing to start a long, high bandwidth, low content rant (would I do that :P).......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

Rosco Bodine - 15-6-2007 at 18:16

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 :D


[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 706 times


In-situ PbO2 plating again!

Xenoid - 15-6-2007 at 20:10

I plated my previously described Pb electrode for about 2 hours to get a thicker, more impervious coat, although it didn't look all that different to the first attempt.

I used some of my finest quality NaClO3 (triple recrystallised, to try and avoid any problems with chloride) to make a saturated chlorate solution.

When I placed the anode in the solution, it was immediately covered with a wispy white precipitate (with no current flowing). The ppt. washed away when the anode was agitated and didn't form again.

When the current (1-2A) was turned on, no oxygen was generated and the anode looked like it was doing its job (making perchlorate)!

After about 5 mins. I turned off the current and removed the anode for examination. The part of the PbO2 coating which had been immersed seemed to be lighter in colour. When I tried squirting it with some water from a wash bottle it started to slough off in parts, revealing a shiny Pb surface.
Meanwhile the Ti cathode which had happily been producing H2 was coated in a dark grey non-adhesive sludge (presumably Pb).

Thus endeth my attempts at in-situ PbO2 plating, unless anyone has any suggestions!

Regards, Xenoid

Eclectic - 15-6-2007 at 20:34

If anyone wants to actually MAKE an iron substrate lead dioxide anode, you might try soaking the iron in concentrated nitric acid first to passivate it. This effectively forms a coating of magnetite (?), preventing further dissolution. Maybe preventing Fe contamination of the plating bath? Experimentation will tell...

Some chromating methods of interest

Rosco Bodine - 16-6-2007 at 09:19

Here are a couple of methods for chromating ....
which is to say modifying the surface oxide layer
of a metal substrate to form a mixed chromium oxide layer which is adherent and has improved resistance to corrosion
and differing electrical conductivity from the unmodified
natural oxide which would otherwise be present .

The first of these patents is an old method which involves
simply dipping or brushing the cleaned metal with a mixture of phosphoric acid and sodium dichromate and then baking
at a mild heat to develop and complete the reaction .
It is not known to me at this point if the electrical conductivity
of this type of chromating layer is good or not . There are variations on the process and I am still looking at these to see if I can learn more specifically concerning the electrical
conductivity . I am hopeful that the electrical property of the chromate coating is conductive , and it would seem that
such a process is applicable also to titanium and other metals . Chromium and vanadium are both dopant materials
useful for improving conductivity of oxide coatings .

Attachment: US2030601 Chromated Steel from sodium dichromate and phosphoric acid dip and bake treatment.pdf (207kB)
This file has been downloaded 727 times


A known conductive chromating for aluminum

Rosco Bodine - 16-6-2007 at 09:30

This method for chromating aluminum is specifically for
improving the conductivity at the surface for the making of good electrical connections .

Whether this method is directly applicable also to other metals besides aluminum ....I am not certain , but it would seem likely . I especially thought of the case involving
the "blue titania" which was described in that earlier
lead peroxide on titanium rectifier patent ...that this
chromating method could be applied to that and the result
could be a desirable and easily made conductive modified
oxides for the "primer layer" on the titanium to be further
coated with other conductive oxides .

Attachment: US2993847 Conductive Chromating for Aluminum.pdf (79kB)
This file has been downloaded 806 times


This is interesting

Rosco Bodine - 17-6-2007 at 02:23

Looking through patents concerning "conductive anodized"
I found this patent which would seem to also have more general applications ....possibly for many of the valve metals .

Very neat process , which is also related to the manufacturers art of producing colored anodized coatings
by the use of dyes which are absorbed by a porous
anodized coating .

Attachment: US6228241 Electrically_conductive_porous_anodized_aluminu.pdf (87kB)
This file has been downloaded 762 times


hashashan - 17-6-2007 at 02:36

Will Iron will be any good for a cell where the PH isn't maintained?
how about copper? Graphite isnt really good because as the PH drops it gets eaten away.

Rosco Bodine - 17-6-2007 at 10:00

Iron will be attacked without pH control . The lower limit
on the pH is reportedly a bit over pH 2.0 and the range
for an iron substrate is reportedly good up to pH 3.5
by one source .....and higher by other sources . Going more basic doesn't seem to bother iron , but increasing acidity does erode it .

The added problem with no pH control and a lead nitrate bath is that it doesn't really matter what substrate is used , as the resulting PbO2 quality will be poor due to
the varying composition of the electrolyte , the nature of
the deposited material will vary by the minute .

With an acetate bath or an alkaline bath you would be more likely to get by without a pH controlled electrolyte ,
but using a lead nitrate bath without any pH control is IMO an exercise in futility for anything but the very thinnest of PbO2 platings . Understand that for every
molar amount of PbO2 being deposited that *TWICE* that molar quantity of freeform nitric acid is appearing in
increasing concentration in the electrolyte , and you can see that in a couple of minutes of plating you have driven the pH nearly to the low end of the scale unless you are
continuously counteracting that acidity . It takes very little
addition of freeform nitric acid to decrease a pH from around pH 4 to below pH 2 where the iron would be attacked . You could literally watch the current meter reading climb with the increasing conductivity of the bath
due to the changing acidity .....and the changing composition would be all over the place so quickly that
with manual additions and pH checks and adjustments ,
you could *never* maintain a constant reaction condition
unless your bath was the size of a swimming pool ,
and you were pumping the electrolye past the anode
like it was sitting in a Jacuzzi .

hashashan - 17-6-2007 at 13:06

Ok im getting the point.
I just dont want to make lead carbonate (quite a mess) can i neutralize the acid with another substance(i mean non-lead) ?

Rosco Bodine - 17-6-2007 at 13:29

If you did that , then you would be looking at a continual decrease in the available Pb in the bath as lead plates out as PbO2 . You kill two birds with one stone if you just flow the electrolyte through a bed of some lead compound which will act as a neutralizer , it controls the pH at an equilibrium and it keeps the Pb content of the
electrolyte constant . This also conveys some honest rate control to your power supply settings , which sort of become meaningless if the composition of the electrolyte is constantly changing .

[Edited on 17-6-2007 by Rosco Bodine]

DTO coated Ti

dann2 - 17-6-2007 at 16:04

Hello,

Got around to coating a Ti strip with Doped Tin Oxide.
Had problems with getting Oxalic acid to etch the Ti. It etched the first piece OK but for some reason or other it would not etch a second piece even though I added a further 60grams Oxalic acid into the 700ml water. There was already 60grams in there.
Switched to hot sulphuric acid which seem to do OK.

The DOP was made up using info in US Pat. 3,940,323. They used SnCl4:5H2O + (NH4)2MoO4 in Example one. I used SnCl2 + Ammonium Molybdate. The SnCl2 + Ammonium Moly. give a dark green ppt. The SnCl2 had problems dissolving due to formation of hydrates (meta stannic acid??) The Ammoniom Moly. had problems dissolving too. There seems to be a portion that will not dissolve. The patent calls for from 0.1% to 15% Mo based on the moles of Tin. I used 10 grams SnCl2:2H2O + 1.47 grams (NH4)6Mo7O24:4H2O (I am guessing the water content as my chemicals are ebay with simply the names Ammonium Molybdate and Stannous Chloride written on tubs). That works out at just over 15% Mo based on the moles of Tin (Welcome to check the math...please).
To make a long story short I baked four times at about 480C. Each bake consisted of three coats of the 'stuff' that I had in the jar after mixing the SnCl2 + Ammonium Moly. I dried each coat with a heatgun. 12 coats total. The whole thing looked good. I decided to try the coated Ti in a Chlorate cell just too see how it would hold up but it was not very conductive. It needed 11 volts applied to get current to flow. Then the current started to drop as the coating was eroded and the Ti then started to passivate. This took about one minute. Bollox. (Sorry about that).

I may try again with a lower Moly content. Also the Pat said to bake at 400, I baked at 480, I do not think it would make any difference.
Also the patent says that Ammonium Molybdate can be used (it lists lots of compounds). The formula for Ammonium Moly is (NH4)6Mo7O24:4H2O coming for a chemical supply house catalogue. The compound the Pat used in their Example 1 (with SnCl4) is (NH4)2MoO4. What compound is this? I presumed it is Ammonium Molybdate?, it is 'nearly' Ammonium Moly:-)

SnCl2 will dissolve in Methanol without any problems (no formation of hydrates) but I cannot get the Ammonium Molybdate to dissolve in any organic solvent that I have. Alas.




If I obtained Antimony Trichloride instead of the Ammonium Moly would it dissolve in Methanol? This would give a clear solution without the complications of Tin hydrates forming.
I could try HCl as Rosco suggested but I did not get around to it.
Perhaps all the Tin Hydrates (or whatever is in there) will decompose to Tin Oxide anyways when they are baked?

It may be better for me to go back to SnCl4 + SbCl3 as all or most of the patents seem to use that combination.
Lead free solder and Chlorine perhaps.

Thats enough rambling for one post.

Regards,
Dann2

Eclectic - 17-6-2007 at 17:05

You want a heteropoly acid called stannomolybdic acid. 12 moly-oxide units in a cage around a tin atom. If it's anything like silicotungstic acid, it should be extremely soluble in acidic ethyl ether. Try boiling a mix of 1-2 parts tin compound to 12 parts molybdenum compound by mole in 1N HCl for a few hours, cool, and extract 2-3 times with ether. Combine and evaporate ether layers (they may be DENSER than water, make sure you don't discard the wrong layer!)

Rosco Bodine - 17-6-2007 at 20:23

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:D


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]

hashashan - 18-6-2007 at 01:38

Quote:
Originally posted by Rosco Bodine
If you did that , then you would be looking at a continual decrease in the available Pb in the bath as lead plates out as PbO2 . You kill two birds with one stone if you just flow the electrolyte through a bed of some lead compound which will act as a neutralizer , it controls the pH at an equilibrium and it keeps the Pb content of the
electrolyte constant . This also conveys some honest rate control to your power supply settings , which sort of become meaningless if the composition of the electrolyte is constantly changing .

[Edited on 17-6-2007 by Rosco Bodine]


and how would you recomend maintaining the PH? i dont have any PH sensors (got only the papers)
so for what i see the only method i can think of is hanging a tea bag with lead hydroxide in the tank. but wouldnt that make the solution basic?

pH regulation

Rosco Bodine - 18-6-2007 at 08:35

The teabag idea was simply a "better than nothing" sort of comment . It surely wouldn't make the bath go basic IMO .
It would probably be an evolution of the teabag idea to have a lower sump pump section in a deep plating tank . A submersible pump under a grate with a filter sock - bag wall to wall across inside the tank and sitting atop the grate so that the pump draws electrolyte through the neutralizer and discharges the neutralized electrolyte back into the main plating section above . This would work in the same way as a power sand filter in a large aquarium , a sort of filtered sump pump arrangement could be a "one tank solution" .
The conventional aquarium power filter arrangement may also be directly applicable .

Figuring out a completely effective way of controlling the pH is exactly the task that has been in my mind .
The recirculation pump and percolation or fluidized bed
with filtering scheme would hold a steady pH . The
pH equilibrium value would depend upon which neutralizing lead salt was chosen to be used . I have no chart or information on what are the pH values associated
with a saturated solution of lead nitrate at various temperatures in contact with various neutralizing lead salts , like lead oxide , or lead oxide hydroxide , or lead carbonate or basic lead carbonate . This method would also reach a pH operating equilibrium value at a pretty concentrated solution value , perhaps an even saturated solution value for the temperature of the neutralized electrolyte ....
so temperature control of the plating tank would have to be used in combination with filters that would prevent any crystallized lead nitrate particles in suspension . The neutralizer sections output solution would need to be warmed further slightly above the temperature of the neutralizer and the plating tank warmer still . When handling
nearly saturated solutions , the temperature gradients across the lines and tanks has to be regulated to prevent
crystallizations from plugging up filters and lines and the pump itself , so the arrangement of things has to consider
the temperature gradients which are needed to prevent clogging .

In a very real sense , the cell itself can function as its own
pH meter once you know the baseline pH , if you have a laboratory power supply operating in constant voltage mode , an increasing current reading will indicate a dropping
pH . You see when the composition of the electrolyte is being maintained constant at a constant temperature and
the plating volatge is constant .....then the plating current
should hold at a steady reading as the plating proceeds .

Anyway , the activities of my internet alias are about to be curtailed by some pressing business which must occupy me
otherwise to keep the lights on and the family fed , so I am
going to have to set this aside for awhile and get back to it .

PbB2O4 , possible quick and easy TiO2 dopant

Rosco Bodine - 18-6-2007 at 18:31

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 :D

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]

dann2 - 18-6-2007 at 20:10

Quote:
Originally posted by hashashan



and how would you recomend maintaining the PH? i dont have any PH sensors (got only the papers)
so for what i see the only method i can think of is hanging a tea bag with lead hydroxide in the tank. but wouldnt that make the solution basic?


Hello Hashashan,

If you can get Litharge, PbO, it is inclined to react less vigerously with the Nitric acid formed and therefor may not raise the pH too much.
Another way may be to make a slurry with the Lead Hydroxide and water and add small amounts every minute or so. This of course requires staying and 'baby sitting' the plating tank.

Dann2

hashashan - 19-6-2007 at 01:04

i believe that i can make some PbO by fusing Pb and NaNO3 (btw do you think that a simple gas burner will do the work?)

and just got another thought. why not to use lead as the temprorary substrate? or maybe even lead coated with the alpha layer of PbO2 (that wouldnt have to be so strictly controlled PH)

Rosco Bodine - 19-6-2007 at 06:51

the lead salts preparation thread is your friend

http://www.sciencemadness.org/talk/viewthread.php?tid=5490&a...

You should look at US3497382 , if an exceptionally high purity , easily made lead oxide is the goal .

dann2 - 20-6-2007 at 07:46

Quote:
Originally posted by Eclectic
You want a heteropoly acid called stannomolybdic acid. 12 moly-oxide units in a cage around a tin atom. If it's anything like silicotungstic acid, it should be extremely soluble in acidic ethyl ether. Try boiling a mix of 1-2 parts tin compound to 12 parts molybdenum compound by mole in 1N HCl for a few hours, cool, and extract 2-3 times with ether. Combine and evaporate ether layers (they may be DENSER than water, make sure you don't discard the wrong layer!)

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:o

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

Cheers,

Dann2

Eclectic - 20-6-2007 at 09:52

Make sure your solution is still very acidic after neutralizing the ammonium. Extra HCl won't cause any problems. Maybe add a bit of hydrogen peroxide (BEFORE you've added any ether, you don't want to make ether peroxides) to discharge the blue color, evaporate ether extracts to dryness. You get tungsten and molybdenum blues under reducing conditions with these polyacids. Maybe the ammonium is acting as a reductant?

I'm extrapolating from a procedure I've used to make silicotungstic acid, which is over 80% by weight soluble in water to make a liquid with a density over 3. Great for flotation separation of minerals with slightly different specific gravity, ie: quartz and beryl.

In any case, even if the stannomolybdic acid is not as soluble in ether as silicotungstic, if you've gotten everything completely solublized, you should be able to take some of your resulting solution, add the proper amount of tin compound to get your mole ratios correct, paint it on and give it a try. The extra HCL and ammonium ions will evaporate at the baking temps.


I plan on going with the 95/5 solder dissolved in concentrated HCL with a bit of peroxide and ammonium bifluoride added. I don't think the bifluoride is needed, but it won't hurt, and I have some.



[Edited on 6-20-2007 by Eclectic]

Rosco Bodine - 20-6-2007 at 10:09

A mixture of stannous and molybdenum fluoborates might solve the interactivity problem and produce a good dispersion of the two oxides when baked.....if the additional doping by boron and fluorine is not a problem ....and it might even be an enhancement .

Eclectic - 20-6-2007 at 12:29

Actually, the only critical thing here is likely just the need to have everything solublized, with nothing unwanted in the solution that will remain in the finished baked coating. Preforming the stannomolybdic acid just ensures solubility of the molybdenum and avoids the formation of insoluble molybdic oxides. The ether extraction is not needed, and may not work for stannomolybdic acid like it does for silicotungstic (where the silicon comes from sodium silicate).

Sorry if the ether extraction turns out to be a blind alley. Lots of interesting variables to experiment with here.

dann2 - 20-6-2007 at 15:20

Hello,

Will try to do this with the refluxed Tin/Moly.
Thanks for help.


The cut from below is from US 4,028,215 Example 13
__________________________________________

A strip of porous titanium having a surface area of approximately 7 square inches (45 square centimeters) was coated with a solution of tin and antimony compounds by use of a vacuum to suck the solution through the porous material. The solution consisted of 5.27 grams of stannous sulfate, 2.63 grams of antimony trichloride, 10 milliliters of hydrochloric acid, and 20 milliliters of butyl alcohol. This was done four times with the baking of one-half hour at approximately 500.degree. C. between each pass through the porous titanium material. A 50 percent aqueous solution of manganese nitrate was passed through the material in the same fashion with a baking between each pass of 45 to 60 minutes at approximately 200 degrees centigrade until a weight gain in the range of 3.36 to 3.56 grams of manganese dioxide is contained therein.
______________________________________

It uses Stannous Sulphate (as opposed to Stannic Chloride as in all other examples).
I presume this is a typo in the patent???

Dann2

Eclectic - 20-6-2007 at 15:25

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]

dann2 - 20-6-2007 at 15:35

Quote:
Originally posted by hashashan
i believe that i can make some PbO by fusing Pb and NaNO3 (btw do you think that a simple gas burner will do the work?)

and just got another thought. why not to use lead as the temprorary substrate? or maybe even lead coated with the alpha layer of PbO2 (that wouldnt have to be so strictly controlled PH)

Hello Hashashan,

I tried this and it works fairly good. Enough heat to melt the Lead is all you need. A gas burner is plenty, it may heat too much. Put a tray of sand about a quarter or half inch in dept between the burner and your reaction vessel to keep heat more controlled. I used a stainless steel soup bowl as the reaction vessel. Plenty of stirring.
You will be adding lots of Nitrate. Far more than the stoioc. amound as I presume lots of the oxygen escapes. A suction filer system would be great as you can then pour lots of water though you PbO to get rid of the Nitrate/Nitrite.
You will stirr the whole lot up first in a fairly large vessel with water and decant the suspended PbO to get rid of unreacted Lead.
Is your Lead pure. You could try measuring its melting/solidification temperature to see is it at the melting point of pure Lead.

If you are going to go down the pH controlling path I would suggest using two tanks and a pump.
If making massive anodes (temporary substrate) you could try rapping/attaching a cloth (or scoth scrubber) to the substrate so that the Lead Dioxide will grow and envelope the cloth and you may get a reinforcing effect.
Massive anodes will need a GOOD plating set up.



Dann2

dann2 - 20-6-2007 at 15:41

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 :D

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

Eclectic - 20-6-2007 at 16:04

I think your best bet is just dissolve 95/5 solder in 12N HCl with a small amount of H2O2 added to help the reaction along and avoid SbH3.

It's no problem to dissolve tin in HCl.

The sulfates are going to be more resistant to decomposition and evaporation of H2SO4 and/or SO3, and will be less soluble in organics. The butanol is maybe to lower solubility, increase evaporation rate, and possibly avoid dissolving away the layer you just baked on in the previous step?

Ok, I'm doing a proof of concept experiment: 125g of common 95/5 solder (approx 1 mole Sn) in 3-4 inch lengths siting in a loosely stoppered flask with 250 ml common muriatic acid (approx 3 moles HCl). It's fizzing merrily without heating up too bad or foaming up out of the flask. More later... 1 hour later 100ml more HCl added and flask transfered to coffee maker hot plate. The reaction isn't going to run away with some heat added to speed it up...6 hours later reaction has slowed down. Most of the solder has dissolved with brown-black precipitate remaining. Cooled and decanted clear liquid, added 200 ml muriatic acid to residue and slowly added dropwize 25 ml 30% H2O2 with stirring (caution, much heat and boiling if added too fast). Heating on coffee maker hotplate continued until everything has dissolved (1 hour). This liquid was combined with the previously decanted liquid and placed in a glass bowl over boiling water to reduce the resulting clear light yellow solution to a smaller volume.

I had to cool the solution so I could add a further 100 ml 30% H2O2 and 100ml HCl. It looks like SnCl2 reduces SbCl3 to something insoluble (same brown-black precipitate). When you've added enough H2O2, the solution turns chlorine green and the precipitate dissolves.

[Edited on 6-22-2007 by Eclectic]

I was able to evaporate the solution to about 200ml before it started to crystalize on the steam bath. I diluted this to 400ml with more muriatic acid (31.5%HCL). Figured as SnCl4.5H2O, this shoult be ~350g in 400 ml solution, with 5% by mole Sb.

If I needed to do this again I'd treat the clear solution from the initial dissolution of solder in HCl with dropwize addition of H2O2 and stirring before adding to the dissolved residue solution.. I estimate 75 ml would be needed. If you start the whole process with mixed HCl, H2O2, the dissolution of the solder will boil violently, and most of the peroxide will be wasted in catalyzed decomposition.

By adding H2O2 dropwize as the reaction proceeds, you end up with a solution of SnCl4/SbCl3 instead of SnCl2 and brown-black precipitate.




[Edited on 6-22-2007 by Eclectic]

[Edited on 6-23-2007 by Eclectic]

[Edited on 6-23-2007 by Eclectic]

hashashan - 21-6-2007 at 00:16

Quote:
Originally posted by dann2
Quote:
Originally posted by hashashan
i believe that i can make some PbO by fusing Pb and NaNO3 (btw do you think that a simple gas burner will do the work?)

and just got another thought. why not to use lead as the temprorary substrate? or maybe even lead coated with the alpha layer of PbO2 (that wouldnt have to be so strictly controlled PH)

Hello Hashashan,

I tried this and it works fairly good. Enough heat to melt the Lead is all you need. A gas burner is plenty, it may heat too much. Put a tray of sand about a quarter or half inch in dept between the burner and your reaction vessel to keep heat more controlled. I used a stainless steel soup bowl as the reaction vessel. Plenty of stirring.
You will be adding lots of Nitrate. Far more than the stoioc. amound as I presume lots of the oxygen escapes. A suction filer system would be great as you can then pour lots of water though you PbO to get rid of the Nitrate/Nitrite.
You will stirr the whole lot up first in a fairly large vessel with water and decant the suspended PbO to get rid of unreacted Lead.
Is your Lead pure. You could try measuring its melting/solidification temperature to see is it at the melting point of pure Lead.

If you are going to go down the pH controlling path I would suggest using two tanks and a pump.
If making massive anodes (temporary substrate) you could try rapping/attaching a cloth (or scoth scrubber) to the substrate so that the Lead Dioxide will grow and envelope the cloth and you may get a reinforcing effect.
Massive anodes will need a GOOD plating set up.



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).

hashashan - 21-6-2007 at 03:22

I gave it a thought. If i am planning to use some PH controll(i still would like to hear some details about it) then i dont see any reason to use a temporary metal substrate, i will just use graphite.
ill sand down some gauging rods flatten their surface, after that ill arrange them in a way i want to and glue them together, stratch some fabric over them and then ill plate them over, erode the graphite away and ill have a nice anode.

dann2 - 22-6-2007 at 16:45

Quote:
Originally posted by Eclectic
Make sure your solution is still very acidic after neutralizing the ammonium. Extra HCl won't cause any problems. Maybe add a bit of hydrogen peroxide (BEFORE you've added any ether, you don't want to make ether peroxides) to discharge the blue color, evaporate ether extracts to dryness. You get tungsten and molybdenum blues under reducing conditions with these polyacids. Maybe the ammonium is acting as a reductant?

[Edited on 6-20-2007 by Eclectic]


Hello,
Soluion is pH 0. I added some H202 and the opaque blue/black solution turned a yellow colour whit a blue ppt.
Decanted off yellow liquid and extracted with Diethyl Ether. There is nothing visible in the ether. Will try evaoprating to dryness.
Is there anypoint in drying the yellow liquid to dryness and using whatever is in it.

Dann2

dann2 - 22-6-2007 at 16:47

Quote:
Originally posted by hashashan
I gave it a thought. If i am planning to use some PH controll(i still would like to hear some details about it) then i dont see any reason to use a temporary metal substrate, i will just use graphite.
ill sand down some gauging rods flatten their surface, after that ill arrange them in a way i want to and glue them together, stratch some fabric over them and then ill plate them over, erode the graphite away and ill have a nice anode.


Hello,
I have never used pH control.
A word of advice I can give is to make small anodes so that pH and Lead Ion conc. will not vary too much.

Dann2

100g / liter HNO3 plating bath for beta PbO2

Rosco Bodine - 22-6-2007 at 20:05

The patent US4026786 describes a PbO2 plating method that could be useful , as it can be much easier to maintain a very low pH which is less sensitive to changing composition during plating , than to maintain a pH much nearer neutral where a very small change in composition causes a drastic change in pH . There can also be other advantages .

For more advanced work .....
The high level of acidity could also simplify the automated maintenance of both the Pb(NO3)2 concentration and pH ,
by means of recirculating the electrolyte across a sacrificial
sheet Pb anode which is energized by an adjustable low voltage ....the voltage level of which could be regulated
automatically by an op amp controller to hold the composition of the electrolyte constant . Conductivity could be sensed by a very low voltage conductivity probe . An automatic controller would probably not be too difficult to design nor expensive to build . I believe that very likely
such an automatic controller is used on the commercial plating equipment , even though no details are provided concerning such equipment , in these patents . It just makes sense that such automated process regulation is being used where larger scale and production quantities of anodes are being made .

Also concerning the preparation of Titanium for plating of
conductive coatings .....aside from the various brute force
methods of grinding and sandblasting , there is an alternative which has been mentioned , generally callled cathodization , or "hydriding" ....where the substrate is made a cathode in an acid solution and run for an extended time at a level of vigorous hydrogen evolution which scours
away and reduces any oxides and leaves a very clean metallic surface ...ready to receive a conductive coating which should be applied immediately ....before any significant
dielectric oxide layer can form . Some comparisons of the
usefulness of cathodization of Titanium as a preplate treatment with other methods of "etching" ect. are described in another patent US4153742 . This preplate cathodization
can even be continued with a plating of the actual free metal
precursor of the same metal whose oxide is then formed
when the polarity is reversed .....so that initially for example
there is a substrate metal to plated metal interface , which
can improve adhesion and conductivity . This hydriding and metallic lead flash preplate technique is possibly better than nothing , if a bare titanium substrate is to be used as above with the acidic Pb(NO3)2 bath .

The alternatives are the Ruthenium , or Tin - Antimony ,
or perhaps MnO2 - Co3O4 intermediate layer methods .

Attachment: US4026786 Perforated Ti uncoated substrate for PbO2 from HNO3 100 g. per liter Pb(NO3)2 bath.pdf (121kB)
This file has been downloaded 849 times


Twospoons - 22-6-2007 at 20:37

Thats a really interesting patent. Perhaps the ceramic particles they mention could be made from magnetite?

Rosco Bodine - 22-6-2007 at 23:00

I'm not sure what the ceramic is , but it is probably something that has near neutral buoyancy in the electrolyte so it stays suspended and scours the surface lightly like a polishing compound does in a rock tumbler . Any inert material of the right density and mesh size would probably work . Having a good flow velocity for the electrolyte should tear any bubbles away pretty fast . Adding some vibration to a scheme having microspheres , the impacts could have a peening and burnishing effect which would tend to close off any pores and shift around the nucleation sites for new bubble formation so that an evenly coated surface results even for very thin layers . The throwing power is probably great enough that this *extra* technique is probably not absolutely necessary but is only an enhancement .

I have been looking for information on the possibility of using
a PbO2 overplating of a Co3O4 doped MnO2 intermediate layer on a titanium substrate , and also looking at the possibility of loading magnetite into a Co3O4 doped MnO2
intermediate layer . There is a perchlorate cell tested variant
using a doped MnO2 anode having titanium substrate described in US4072586 . Evidently a bit of Co(NO3)2 added
to Mn(NO3)2 increases the conductivity and life of the anode .
An addition of 10% of the carbonates to the nitrates and
baking out at 300C for 5 minutes is optimum . ( US3553087) After the first three coats are baked , a thickener can be added (hydroxyethylcellulose) to get a heavier build on subsequent coats . (US4243503) Additionally Sb or Bi dopants to the finish layers of MnO2 have a catalytic effect on perchlorate production .

Further , a titanium alloy having 1.5% cobalt is better than pure titanium for a substrate , and so is a 1.5% manganese alloy . I have no idea what is the composition of various commercial grades of titanium alloys , but it may well be that
certain existing alloys could be better suited for substrates
than the pure material .

BTW , on page 8 of this thread I posted another patent which
related to a bismuth doped PbO2 having increased conductivity and improved wear resistance , and in the plating bath containing a small quantity of bismuth nitrate
it was found necessary to use a higher HNO3 content plating bath ....and amounts even up to 150 g / liter were charted ,
but this would seem excessive . Anyway the same fine grain deposits were reported for the bismuth doped PbO2 anodes
gotten from a highly acidic bath , although they were brittle and cracked when thick layers were attempted .

Attachment: US4101390 Bismuth modified thin layer Lead Dioxide Perchlorate Anode.pdf (977.42 KiB)
http://www.sciencemadness.org/talk/viewthread.php?action=att...

[Edited on 23-6-2007 by Rosco Bodine]

Attachment: US4072586 Baked Mn(NO3)2 Manganese_dioxide_electrodes.pdf (156kB)
This file has been downloaded 940 times


dann2 - 23-6-2007 at 15:23

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 :D
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

Rosco Bodine - 23-6-2007 at 18:42

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 :D

Just glean what information is useful and put it together in one system .
Quote:

Patent 4,026,786 does not mention making Chlorate or Perchlorate for the anodes, if that makes any difference. Only electro-winning metals.

The bismuth doped PbO2 patent US4101390 is analogous to US4026786 , and it is for a perchlorate anode .
Quote:

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


5-20 g HNO3 per liter for US3634216 is a lot lower acidity than the 100 - 120 g HNO3 per liter of US4026786 which relates nicely with the even slightly stronger 150 g. HNO3 per liter for the Bismuth doped PbO2 of US4101390 . Bismuth is a catalytic dopant for MnO2 anodes destined for perchlorate production , as is antimony ....and evidently this is also true for PbO2 anodes .

Finer grained and more conductive platings produced
under less pH sensitive conditions is something that
is worth consideration for a one tank setup where
a relatively thin layer is going to be deposited .

When it comes to the oxide plating ,
there is actually an electrodeposited cobalt oxide which is supposedly superior to PbO2 in conductivity and resistance to erosion . This might also be used as an intermediate layer .

[Edited on 23-6-2007 by Rosco Bodine]

Attachment: US3399966 Substoichiometric Cobaltic Oxide Electrodeposited Anode.pdf (180kB)
This file has been downloaded 764 times


Patent# US3399966

jpsmith123 - 24-6-2007 at 04:29

That's a great patent!

If we can take that information at face value (and I realize that's a big "if"), that may be a big advancement.

Seems you can easily apply the oxide electrolytically over almost anything, including Ti and graphite, with no other substances (e.g., dopants), and no other treatments (e.g., baking), required.

Moreover, on page 4, the inventors state:

"The anode of deposited CoO is not perfectly insoluble in a solution with pH under 1 containing bromide, iodide, or other anions haviing discharge potential of under +0.7v.; however it is perfectly insoluble in the solutions of pH above 1 containing chloride, sulfate, nitrate or the like. Then it is most effective for the electrolysis of sodium chloride, chlorate or the like."

So apparently it will make chlorate and perchlorate! Sounds like it would be definately worth a try. Now, where's the cheapest place to get cobalt salts?

Dipped and Baked Cobalt Oxides works too

Rosco Bodine - 24-6-2007 at 08:31

Quote:
Originally posted by jpsmith123
That's a great patent!


Yeah , and another interesting aspect is the possibilities for any of the conductive oxides which may be applied by either
electrodeposition or by the relatively low temperature decomposition of a salt . I am not sure what might result if
the techniques of electrodeposition and thermal decomposition to the oxide were sequenced , but there
is the possibility for interesting results . I have thought about the enamelware pots and pans where a low melting
ceramic is applied as a "powder coat" which then fuses on baking , possibly reacts as some refractory materials do to
form a thermosetting material ....and if this same idea can be exploited for a semiconductive oxides coating , then there
could be some interesting modified spinel type of glasses or
ceramics for anodes , which possibly could be applied to just about any conductive substrate .....or possibly even sintered into a solid stick of conductive ceramic .
Quote:

If we can take that information at face value (and I realize that's a big "if"), that may be a big advancement.

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 :D
Quote:

Seems you can easily apply the oxide electrolytically over almost anything, including Ti and graphite, with no other substances (e.g., dopants), and no other treatments (e.g., baking), required.

Moreover, on page 4, the inventors state:

"The anode of deposited CoO is not perfectly insoluble in a solution with pH under 1 containing bromide, iodide, or other anions haviing discharge potential of under +0.7v.; however it is perfectly insoluble in the solutions of pH above 1 containing chloride, sulfate, nitrate or the like. Then it is most effective for the electrolysis of sodium chloride, chlorate or the like."

So apparently it will make chlorate and perchlorate! Sounds like it would be definately worth a try. Now, where's the cheapest place to get cobalt salts?


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 :D

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

Eclectic - 24-6-2007 at 08:55

Cobalt is the binder metal in tungsten carbide materials, up to 20% in some, but more typically 3-5%. Thin carbide slitting knives used in cardboard and plastic sheeting manufacture are +10% cobalt.

With nickel going for over $22/lb, I wouldn't be surprised if cobalt salts are more than $100/lb. You can get some from pottery suppliers, as it is the pigment responsible for Wedgewood Blue.

There is a patented conductive Titanium suboxide ceramic anode material marketed as Ebonex.

Rosco Bodine - 24-6-2007 at 09:56

Looks like cobalt carbonate is not too expensive ,
about $26.50 / lb
http://store.ceramicstoreinc.com/cocacooxcoca.html

Quote:
Originally posted by Eclectic
There is a patented conductive Titanium suboxide ceramic anode material marketed as Ebonex.


Back on page 13 of this thread I had actually mentioned Ebonex , ( I just removed the quotation marks which prevented a search from returning hits on it )
Ebonex has actually been investigated for usefulness
as a perchlorate anode , but the one report I found in the literature did not give it a favorable result for that application as a substrate when coated with PbO2 , its efficiency was low . Perhaps some other coating , like cobalt or manganese oxides would fare better . Evidently perchlorate cells are pretty specific in what combinations of materials work well for anode construction and coatings and there are only a few combinations that work okay while most fail for one or more reasons .

One curious thing is the profound catalytic activity of bismuth even at microscopic trace levels as a dopant for PbO2 in perchlorate production . Reportedly simply dipping a PbO2 anode into a bismuth nitrate solution leaves enough residual bismuth on the surface to produce a significant lowering of the cell voltage for perchlorate production by that anode when it is put into a perchlorate cell ...several tenths of a volt difference IIRC and tens of percentile increases in cell efficiency ....simply from trace levels of bismuth on the PbO2 .
So clearly , catalytic dopants do matter and can be key actually in whether a particular anode works beautifully or not well at all .

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

Solder Chloride Solution

Eclectic - 24-6-2007 at 11:36

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. :D

[Edited on 6-24-2007 by Eclectic]

dann2 - 24-6-2007 at 12:13

Hello,
Cobalt Sulphate (Cobaltous Sulphate, Cobalt II Sulphate) can be purchased down at the local farm store as a trace element supply for sheep (!!). Sheep run low in Cobalt in certain areas. (I'm not joking).
It is about 40 dollars per KG.
With Calcium Nitrate you can make Cobalt Nitrate my dissolving and letting Ca Sulphate ppt.

Dann2

jpsmith123 - 24-6-2007 at 14:07

Hello Dann2,

Example 2 of the patent uses the sulfate. And in the claims part of the patent, they mention nitrate, sulfate, acetate and fluborate. So it looks like you wouldn't have to bother converting to nitrate.

dann2 - 24-6-2007 at 18:31

Hello JP,

This anode making just gets easier and easier!
I used to think that Cobalt Sulphate and Cobaltous Sulphate were different compounds. Not so.
It would (as others have said here) be great to get away from Lead Compounds altogether.

I tested the product from my Magnetite coated with Lead Dioxide anode cell today and it is Perchlorate (as expected). Since the coating of PbO2 was so thin on the Magnetite it is hard to tell if it is still there or not. Both substances are black and that makes it harder to see the Lead Dioxide. After cleaning the anode there still seems to be a difference in texture where I put on the LD.
I intend to properly coat a piece of Magnetite tomorrow and run a Chlorate cell taking note of amounts of product, current, etc, etc.

I coated the top end of Magnetite with Copper. Silver does not seem to suit Magnetite. Copper is best.
I used a 'standard' Copper bath for plating Copper. 78 grams Copper Sulphate:7H2O, 18.5 grams Sulphuric acid, 500 grams water. 32C, Anode is pure Copper. Current density about 60mA per square cm. Good Copper coat after about half hour.


Dann2

magnetite related

Rosco Bodine - 24-6-2007 at 19:04

Don't remember if you have this one posted or not ,
but it may reduce or eliminate the annealing requirement .

I have seen other patents also say that it is beneficial to the conductivity to have ratios for the mixed oxides that are a little away from the exact stoichiometry for compounds like magnetite , spinel , perovskite , ect.

Attachment: US931513 Cast Magnetite Anode using crystallization modifiers.pdf (117kB)
This file has been downloaded 930 times


My first PbO2 plating attempt

12AX7 - 25-6-2007 at 13:37

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]

PbO2ated_Graphite1.jpg - 84kB

12AX7 - 25-6-2007 at 13:41

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]

PbO2ated_Graphite2.jpg - 63kB

Copper Nitrate saves Lead Ions

dann2 - 25-6-2007 at 16:36

Hello,

Copper Nitrate is added to Lead Nitrate plating bath to stop Lead from being deposited on the cathode.
I received the following explanation some time ago.
It in on me page.


________________________
The function of Copper Nitrate in the plating bath is to stop Lead metal from plating onto the cathodes and wasting Lead ions.


If I understand this process correctly, the Copper(Nitrate)
is added to the solution in order to plate out
first. After this initial Copper plating at the
cathode, some Lead will start to deposit, but due
to the fact that there is already a layer of
Copper on the cathode, the Lead and Copper will
form a shorted galvanic couple, and the Lead,
being placed above Copper in the electrochemical
series, will be corroded or re dissolved. This
couple can supposedly also cause Hydrogen to be
evolved at the cathode, instead of any metal
plating out. I have always used a cathode with a
larger area than the anode being plated in order
to (hopefully) allow the Lead deposited there to
be re dissolved as fast as it forms. I do not know
of any magic area ratio, but I suppose you could
expect some unusual things to happen if you used a
very small cathode.

There is no need for to use Copper Nitrate if you are using a 'high' Nitric acid (100g/l HNO3) bath
____________________________________________

Perhaps you can add Copper Acetate to your plating bath to stop the Lead from being wasted.

The coating of Lead Dioxide on the Graphite that is in the pictures (I take no pleasure in being the bearer of bad news) will not protect the graphite from (Per)Chlorate solution.
Would stirring the plating solution help.? It seems that the plating is worse as you get to the bottom of the anode.

Dann2

Xenoid - 25-6-2007 at 16:59

Hi Tim,

A while back I too had an experimental go at plating a graphite rod using lead acetate solution and a Ti cathode. The plating looked OK whilst wet, but flaked off when dry. I used a current of about 5 mA/cm2, I later came across a paper where the authors were talking about 30 A/m2 being a HIGH plating current. By my calculations thats only 3 mA/cm2. So maybe PbO2 plating needs to be carried out at only 1-2 mA/cm2. Incidently the back of my anode where the current would have been lower, had started to develop a well bonded multi-coloured hue suggestive of a thin oxide layer!

Regards, Xenoid

12AX7 - 25-6-2007 at 18:57

Yeah, I got some iridescence on the layer. Little was visible at the time I took the pictures above.

FWIW, I have since scraped off most of the PbO2, adding it to my pile of the stuff (it's by far the blackest; the next most recent produce, from a divided cell anodizing on lead ingot, was darker brown than stuff I made previously, but brown nonetheless). What remains on the graphite appears to be well bonded. I suppose a reducing agent will be necessary to remove it (HCl I guess, but it doesn't go with lead very well).

If it forms a couple with copper, that doesn't make sense because my cathode IS copper wire! Cathode area is a good point though. BTW, the lead acetate I'm using was still green from copper impurity, although that isn't really saying much given the strength of the color.

Right now, I'm trying a stainless anode (about 1" wide, 3" long, 18 gauge, probably 304 or 316) with a copper strip cathode (almost the same dimensions; flattened 1/2" flexible tubing). I noticed the solution turning deep orange around it (in a few minutes, with some stirring, the solution had changed color noticably, so the color is strong), so I've pulled it out to only 1/4" submerged (if it doesn't fall over farther).

I had attempted to prepare the anode, first by cleaning it (sandpaper, detergent and then isopropyl alcohol), then I heated it red hot to attempt to grow a layer of Cr2O3 or Fe3O4. The color is varying iridescent shades of gray.

Tim

electrolytically etching stainless steels

Rosco Bodine - 25-6-2007 at 21:45

Stainless steel is something which might be possible to use as a substrate , and I found an interesting patent which
could be useful in preparing it for use as a substrate .

The process was intended to be used for manufacturing
filtering screens by etching tiny holes completely through
a very thin 3-5 thousandths inch stainless steel sheet ,
by selectively dissolving out the grain boundaries and leaving mostly a sheet of chromium having 15 thousand
holes per square inch . But I was thinking that if a thicker material was used , it would simply etch many tiny cavities
all over the surface .....like so many crevices a few thousandths of an inch deep , which should provide good adhesion for any conductive intermediate layer or plated on
lead oxide . Perhaps a hydriding treatment and then a tin oxide doped with antimony could be applied the same way
as would be done with titanium , followed by PbO2 .
Or maybe the electrodeposited cobalt oxide and then a
baked cobalt oxide , followed by PbO2 .

Anyway it seemed like it might be worth a try , since
the process of etching the stainless deliberately as a pretreatment would sure get rid of whatever was most easily corroded first .....leaving something of an already
pre-corroded substrate , the legacy of which is a porous
substrate which might have a tenacious grip on subsequent coatings keyed into its crevices .

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

Attachment: US3352769 Electrolytically Etched , pitted , and MICROPERORATED Stainless Steel.pdf (266kB)
This file has been downloaded 698 times


hashashan - 25-6-2007 at 23:21

12AX7 i once had the same results as you did. and i do have advice for you. first do add copper ions because of what dann2 explained to you. I always add a lot of copper ions because after all your copper is deposited the lead begins to deposit and for some reason it doesnt redisolve like dann said.

Also you use an unbelievably high current. i use 3V with quite a resistor attached to it(i dot remember what is its value, but i never plate above 200ma

more concerning baked cobalt oxides

Rosco Bodine - 26-6-2007 at 10:56

From everything I have been reading , it looks like
that if a titanium substrate is going to be used ,
and if precious metal dopants are to be avoided ,
then there are very limited choices of what intermediate
oxide layers can be used to prevent passivation of the titanium . Tin oxide doped with Antimony oxide is the cheapest , but builds slowly and involves some tedious
preparation of the chlorides which must be applied as an
acidic solution .

Cobalt nitrate is much more soluble and may be applied
directly to the titanium and baked , and it builds thickness
faster , while producing a conductivity on par or even better
than the antimony doped tin oxide .....but does this as a single substance . Additionally another conductive cobalt oxide can be electrodeposited , and *if* these different
oxides can be applied sequentially , then a thick deposit can be achieved easily . The baked coating alone may be a durable enough anode for perchlorate production , and if not then it could likely be overplated with PbO2 .

In the attached patent US4115239 see Example #2 where a direct coating of titanium with Co(NO3)2 is described as being
used for the interface layer between the titanium substrate and a modified cobalt oxides working coating . The conductivity is excellent even at curent densities twice what
would be used for perchlorate production . The conductivity is on par (or better) than the ruthenium oxide performance , yet cobalt is far less expensive and it evidently has better conductivity than the tin oxide , while being easier to prepare the cobalt nitrate reagent and faster to build up thickness of the baked oxide .

Cobalt oxide looks very promising as a perchlorate cell anode material or intermediate material in several respects .

Attachment: US4115239 Baked Co(NO3)2 Direct Coated Titanium anode.pdf (66kB)
This file has been downloaded 1048 times


Eclectic - 26-6-2007 at 11:16

Damn, Rosco. What am I going to do with all my solder chloride? :P
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.

Rosco Bodine - 26-6-2007 at 11:35

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

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]

12AX7 - 26-6-2007 at 13:35

The solution is more or less purple today. Chromium acetate complex?

Have cleaned off the anode, which seems to be well pitted at the bottom, except for some areas which looked kind of brown.

I cooked it hotter this time -- about 1600°F / 850°C, giving a dark gray color with some iridescence. If I were to guess at the XRD pattern, I'd put my money on something like FeCr2O4.

Any bets on what the mixed solution will do? At worst, iron will oxidize to ferric, chromic to chromate, and possibly nickel peroxide will form (maybe doping the PbO2, if any forms). Nickel and lead are similar in reduction potential (to metal) so are likely to plate out as has been going.

If I have 2V across 20 ohms, I'll have 0.1A, or for roughly 3 in^2, around 6mA/cm^2. Still high? Meh, I don't care about finish just yet, I have to find out if the anode even remains stable.

Tim

dann2 - 26-6-2007 at 15:59

Quote:
Originally posted by Rosco Bodine




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


Some info. here (at bottom)
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

uses Indium Nitrate an an interfacial coating between Co+other stuff and the Ti substrate.

I have seen a ref. to using Co to make Perchlorate, cannot remember where. Will look up.
Dann2

Camping Gear As A Source Of Titanium

jpsmith123 - 26-6-2007 at 16:45

This place has 7" titanium tent pegs for $3.56, and all kinds of titanium cups, plates, cookware, etc., made by "Snow Peak".

My guess is that it is probably not CP Ti but an alloy.

http://www.backcountry.com/

great minds think alike

Rosco Bodine - 26-6-2007 at 17:11

@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 :D 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. :P

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 976 times


garage chemist - 26-6-2007 at 17:17

My grade 1 titanium strips have arrived, though I have yet to buy a quartz tube for my tube furnace and make TiCl4 in order to be able to properly coat them.

Also, the preparation of titanium tetrabutoxide from TiCl4 is not as straightforward as one may think. The reaction between TiCl4 and 1-butanol only takes place in the presence of a base which binds the HCl. Ammonia is used: TiCl4 is dissolved in a large excess of dry butanol and dry ammonia gas is added. The NH4Cl which precipitates is filtered and the filtrate distilled in order to separate the Ti(OBu)4 from the excess butanol.
The problem is that no excess of ammonia must be used, as more than the theoretical amount of it will destroy the ester as fast as it forms it. So I will probably have to weigh the reaction mix in order to find out when the addition of ammonia must be stopped.
Or I'll weigh the ammonia as NH4Cl and liberate it with NaOH, in order to only generate the theoretical amount in the first place.

And of course theres the RuCl3 problem, which will be more difficult to solve than the Ti(OBu)4 problem.

So its all going to take a lot of time.

Rosco Bodine - 26-6-2007 at 18:00

Hmmmm..... No problem , because you don't need all that .

Clean and acid etch / cathodize - hydride your titanium .

Paint with Co(NO3)2 and bake at ~360C for 10 minutes .

Repeat twice .

Then apply whatever subsequent build coats of oxides
that suit your fancy , via electrodeposition or baking
or combinations .

Or you can get about the same thing using the antimony doped tin oxides initially .

You don't need to involve separately made titanium oxides
with reducing schemes for making suboxides , nor do you need exotic or noble metals to get a non-passivating
and good conducting intermediate layer on titanium .

Twospoons - 27-6-2007 at 13:53

Given that my local pottery supplier has both cobalt oxide and carbonate, which is going to be easier to convert to the nitrate? ( I have large amounts of nitric acid).
Rosco, my heartfelt thanks for sharing all these patent pdf's with us - I never seem to have enough time to do all the patent trawling you seem to manage!

Eclectic - 27-6-2007 at 14:09

The carbonate is probably more reactive.

may want to get some zinc also

Rosco Bodine - 27-6-2007 at 15:46

Quote:
Originally posted by Twospoons
Given that my local pottery supplier has both cobalt oxide and carbonate, which is going to be easier to convert to the nitrate? ( I have large amounts of nitric acid).

The carbonate for sure will be easiest . It will probably go easiest if you make a thin slurry with plain water , and then
add the nitric acid by drops while stirring . If you get the drip rate just right , each drops sudden effervescence will subside
just as the next drop arrives , and it will go faster as the
mixture gets hot and more fluid . I do it that way with basic copper carbonate which is similar and it goes very smoothly
to a strong solution of the nitrate . It may heat up to b.p.
if you have a lot of it in the beaker , so a cool water bath
may help to speed the addition if it gets too exothermic and
slows down the addition too much for patience .
Quote:

Rosco, my heartfelt thanks for sharing all these patent pdf's with us - I never seem to have enough time to do all the patent trawling you seem to manage!

No problem , I have a backlog of experiments for spending way too much time researching , but then it usually saves time in the long run not to be reinventing the wheel .
Most stuff I would do an experiment to learn , somebody else was thinking the same thing and already did it , so it saves me the time if I run across it .

About the zinc .....that cobalt and zinc bimetal spinel looks like the one that tested best .
I have some zinc carbonate
which was precipitated from the sulfate . But I am concerned
about any sulfate impurity that may still come across into the
nitrate . I am thinking it may be good to use a barium salt
getter for the sulfate , and some further purification . I think I have some reagent zinc granules and I may just dissolve those directly in HNO3 to save the trouble of purification .

With semiconductor chemistry like we are doing , the purity requirements on some of these compositions could be unusually stringent . I know that certain impurities in many of the semiconductor compositions is intolerable ....and to what extent that applies here is unknown . I have a feeling that QC is pretty rigid for a lot of these schemes to work , reagent purity , bake times , current densities ....ect.
The QC may not be as bad as clean room conditions for
microcircuits .....but it possibly is sensitive more than what
may be usual for not too exacting general hobby chemistry .
On some of this stuff it may absolutely matter that glass
containers were used , instead of plastic like polyethylene
or polypropylene or PFA , simply for whatever impurities may
leach from the glass . This is where I pull out my 2 liter
PFA beakers which have been sitting idle for too long .
That "traffic light patent" for colored lead oxides in the lead salts preparation thread is a specific case where even trace silicate can complicate a particular semiconductor oxide formation ....for example . That same story could hold
true for these other semiconductor materials where a
very specific structure for the material is required . How
sensitive they are to process variables and impurities is a huge unknown .

That series of Dow patents involving the cobalt spinels is
the most interesting thing I have seen . I like the idea
of using the Sn - Sb oxides interface because it makes
the baking temperature less critical for the cobalt spinel
that would go over it . I think that maybe the best system
would be to use a perforated sheet titanium substrate ,
with the Sn - Sb intermediate layer , a spinel coating of
the ZnCo2O4 , and then an electrodeposited PbO2 outer layer . That would seem to be about as nearly permanent as possible for a perchlorate anode , as can be made without expensive exotic materials .

Relevant substrate patents are US4061549 , US4369105 , US4428805 .

[Edited on 28-6-2007 by Rosco Bodine]

I wonder how pure are the chems from ceramics shops?

jpsmith123 - 28-6-2007 at 17:10

Somewhere online I happened upon a discussion in a newsgroup or forum somewhere regarding buying cobalt compounds from ceramic supply stores.

As I recall, one of the participants in the discussion felt that he had purchased some cobalt carbonate that was cut with something else...something less expensive. He felt that with the high price of cobalt compounds, there was an incentive for vendors to cheat a little bit.

Anyway, according to the patent Rosco found, the acetate salt supposedly works, too, so maybe you could save your nitric acid and mix the carbonate up with some distilled vinegar instead?

Quote:
Originally posted by Twospoons
Given that my local pottery supplier has both cobalt oxide and carbonate, which is going to be easier to convert to the nitrate? ( I have large amounts of nitric acid).
Rosco, my heartfelt thanks for sharing all these patent pdf's with us - I never seem to have enough time to do all the patent trawling you seem to manage!

Twospoons - 28-6-2007 at 18:21

Thanks, but I don't really need to save nitric. I have about 12 litres of 68%, just sitting around, not being used for anything much.
Its possible the carbonate isn't deliberately 'cut', just that the impurity is of no consequence in pottery. Cobalt is a *very* strong glaze colorant.

Supposing purification was needed: plate out the metal, then redissolve in nitric, maybe?

not_important - 28-6-2007 at 19:37

The carbonate is est, pottery cobalt oxide is generally the mixed II/III oxide and seems a little slow going into solution in oxidising acids.

A simple thing that can help with purity is to not use an excess of acid, but have some of the oxide/carbonate/hydroxide left. Gently boil the mix for awhile, then let cool and filter. In some cases you want to then add enough nitric acid to have an excess, or add H2O2, and bring to a boil again, then add enough of the carbonate or hydroxide to push it back alkaline and have some solids in suspension; this converts iron the the Fe(III) state and then pulls it out as the hydroxide.

Plating out from solution isn't going to do too much purification. You can get some by plating from a Co metal anode and plate onto the cathode with as low a voltage as will cause a decent plating rate. Just pulling the metal out of solution using carbon anodes tends to plate out other metals not too different in electromotive standing.

Crystallisation is the other route, leaving a fair amount of the salt in solution. In the case of cobalt nitrate, the solubility in alcohol is high enough that you can do a crystallisation from alcohol, then another from high purity water.

Rosco Bodine - 28-6-2007 at 23:22

Maybe purification isn't even needed . Heck at first , I think just make the nitrate solution , perhaps leaving slight amount of undissolved carbonate as mentioned ,
give it a good boil and rapid filtering through a cotton plug in a funnel to polish the hot solution .
Then boil it down until some crystals of the trihydrate ?
Co(NO3)2 start appearing , and when the temperature
drops to ~70C , decant the liquid and repeat . Taking the trihydrate product at well above the 56C where the hexahydrate formation occurs should clean it up pretty good as a first pass .

Then make a 50% ( or stronger ) solution in alcohol (based on the hexahydrate) , adding 3 equivalents of H2O if needed but it probably won't be needed .

I don't have specific information , but I expect the anhydrous salt or maybe a monohydrate could likely be crystallized out readily from cooling a saturated hot alcohol solution.....unless this is a wierd one that has an alcohol of crystallization .

Just that much manipulation is probably sufficient .

If it proves not to be good enough , then later maybe
a chemical reduction to the free metal , using vitamin C
or formaldehyde or glucose , and then redissolving the
metal in acid for another pass ought to do it . But it probably wouldn't come to that .

cobaltous acid

Rosco Bodine - 2-7-2007 at 17:03

While reading a pretty comprehensive article on cobalt
on the following page
http://www.1911encyclopedia.org/Cobalt
the following sentence caught my notice
Quote:
By suspending cobaltous hydroxide in water and adding hydrogen peroxide, a strongly acid liquid is obtained (after filtering) which probably contains cobaltous acid, H2CoO3.


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* :D , 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 .

dann2 - 7-7-2007 at 10:57

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

alancj - 7-7-2007 at 16:51

You might try a worldcat.org book search to find it in a library. I got 23 results; nearest one to me is 350 miles. I searched "Lead dioxide-plated titanium anode for electrowinning metals from acid solutions"

-Alan

dann2 - 14-7-2007 at 17:09

Hello,


I made 10 grams alloy, consisting of 7.6 grams Sn and 2.4 grams Sb added to 100 ml (35%) HCl. Refluxed for 36 hours.
Tin dissolved (after a few hours), Antimony did not. Added 5cc of (30%)H2O2, refluxed for 20 hours.
Sb dissolved. It may have dissolved before 20 hours had passed, I did not check.

Distilled off about 40cc liquid. Cooled and added 15cc 30% H2O2.
The liquid turned light yellow. A Ti Oxide indicator test turned from blue to Orange.
Ti indicator was added to very small sample of flask and then discarded.
The solution was then boiled for five minutes and cooled.
I checked a tiny sample of the solution with Ti indicator (blue) indicator again
and I had to add a few drops H2O2 to the solution to make it capable of changing
the indicator from blue to Orange.

Solution consists of 16.7 grams SnCl4 (SnCl4 is 45.5% Sn)
+ 4.5 grams SbCl (SbCl3 is 53.4% Sb)
in 38cc liquid (HCl + H202 + Water)

Ratio is 76% Tin, 24% Antimony.

The ratio is similar to the Patent below.
________________________
US 4040939 EXAMPLE 1
________________________________________________________________
A solution for the semi-conductive intermediate coating was prepared by mixing 30 milliliters
of butyl alcohol, 5 milliliters of hydrochloric acid (HCl), 3.2 grams of antimony trichloride SbCl3),
and 15.1 grams of stannic chloride pentahydrate (SnCl4.5H2O).
A strip of clean titanium
plate was immersed in hot HCl for 1/2 hours to etch the surface. It was then washed with water and dried.
The titanium was then coated twice by brushing with the solution described above. The surface
of the plate was dried for ten minutes in an oven at 140.degree. C. after applying each coating. The
titanium was then baked at 500 C. for 7 +-1 minutes. The theoretical composition of the
semi-conductive intermediate coating thus prepared was 81.7 percent SnO2 and 18.3 percent
antimony oxides (calculated as Sb2O3). The strip was then buffed with a wire brush until
a high gloss black surface appeared. The weight of the semi-conductive intermediate coating was
about 3.8 milligrams per square inch (6 grams per square meter).
__________________________________________________________________
The full patent is available here:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...


I etched two pieces of Ti strips with hot HCl and painted with the solution above.

Note:
When etching Ti it is important to heat the acid and then dunk in the Ti. If you put
the Ti into the acid when it is cold and heat up the acid + Ti strips there will be
no reaction between the HCl and the Ti. It would seem that the Oxide coating on the
Ti is capable of getting thicker and thicker as the challange gets greater (acid gets
hotter). It will sit there and will not be etched. The same goes for Oxalic and Sulphuric
acids as I dumped theses acids thinking there were useless after making the above miskake.

I baked one piece three time (three coats of solution per bake). I dried each coat
with a heat gun before applying the next. 9 coats total.
It did not work.
The coating did not turn black as per the patent. There was a yellowish appearance
to it when it was hot coming out of the oven. It then became more white than black.
If you buffed the surface the coating came off. NO GLOSS BLACK BY ANY MEANS.
I put the coated Ti into a NaCl solution as on anode. It passivated as per
pure uncoated Ti.

Suggestions please...


I have SnCl2 (solid). Perhaps I could try that with SbCl3 (make from Sb Metal + HCl + H202).

Dann2

12AX7 - 14-7-2007 at 20:08

More fire? Idunno...

dann2 - 15-7-2007 at 05:07

Quote:
Originally posted by 12AX7
More fire? Idunno...


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 :mad: and getting more :mad:

:D

[Edited on 15-7-2007 by dann2]

[Edited on 15-7-2007 by dann2]

Eclectic - 15-7-2007 at 07:29

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 :P)

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]

dann2 - 15-7-2007 at 18:43

Hello Electic,

You have enough solution there to coat an airport runway:D

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

dann2 - 15-7-2007 at 20:10

Hello,



Following on from my adventures with home produced SnCl4.... which were not successful
I decided to try SnCl2:2H20 for to obtain a Doped Tin Oxide undercoat for
LD on Ti. All %'s are by weight below. The ratio's of Sn to Sb are guided
by US 4040939 Example 1, a few posts up.

Dissolved 10 grams Sb metal (ebay) in 80mL 35% HCl and 24mL of 30% H2O2.
Not all the HCl and H2O2 were added at the start. I added them as
the Sb dissolution went along. I used a reflux apparatus (flask + condenser).
It took quite a long time. Sb pieces were probably too big.
I was left with a clear yellow solution. Is yellow the proper colour?
I distilled off all of the acid/water/H202 I dared and was left with
SbCl3 solution that had a weight of 23.4 gram (approx. 11cc).
This solution was yellow and viscous and contains 0.41 grams Sb per gram.
(allowing for some loss of Sb when solution was poured from flask to jar)
There was a small amount of fluffy ppt.

The SnCl2:2H2O was obtained as Tin Mortant (white solid).

The 'painting' solution consisted off:>>>
5 grams SnCl2:2H20 {2.63 grams Sn (77% of Sn/Sb ratio of final paint)
1.92 grams of SbCl3 solution {0.787 grams Sb (23% of Sn/Sb ratio of final paint)
2.2 grams 35% HCl
10 ml Iso-Propyl alcohol (surgical spirit used)

This 'paint' was a clear solution with a small fluffy ppt at the bottom of the container.

A piece of Ti was etched in hot 12% HCl (hardware store variety)
The Ti was painted with two coates of 'paint'. Each coat was dryed using a heat gun.
The Ti was then baked at approx. 415C to 450C for 10 minutes.
Two more coats + bake.
Two more coats + bake. 6 coats total, 3 bakes.

This time (unlike the last time with SnCl4 etc) the coating turned black.
Rubbing with steel wool seemed to remove the coating on the high places of the
Ti.
The coating was much more adherent that the last attempt (with the SnCl4 etc).
The coated Ti was put into a Chlorate cell as an anode to see how well the coating
would stand up to current.
It took a few minutes for the Ti to passivate. Much slower that uncoated Ti but
the coating is (IMHO) useless as an usable interface between Ti and LD.

A second piece of Ti was coated similar to above except a ligher coating
of 'paint' was used. It was applied as a single stroke of the brush.
The brush consists of a piece of polyester cloth attached to a stick.(don't LOL).
When used as an anode the Ti passivated but I though there was an improvement
in resistance to passivation.

When 'paint' was dried (using heat gun) you could see crystals formed on
the surface of the Ti.

The temperature that the Ti reaches in the oven was checked by bolting a
thermocouple to a piece of 'painted' Ti plate and placed into oven.
The temperature rose to 370C after 2 minutes
It was at 440C after 5 minutes and reached a steady 450C after 7 minutes.
Ti was baked for 10 minutes. The 'oven' thermoucouple was reading 480C.
No forced convection or air added to oven.
I guess I should run my oven a bit hotter to get Ti to about 480C.

Flames, suggestions, comments etc etc.

Don't take the three decimal places too seriously as my scale only weights
to 1/10 of a gram.


Dann2




[Edited on 16-7-2007 by dann2]

Rosco Bodine - 15-7-2007 at 21:38

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 :D

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

dann2 - 16-7-2007 at 09:42

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 :D

[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 :D )
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.............:D


Thanks for input.

Cheers,
Dann2

hashashan - 16-7-2007 at 11:21

Well just had a look at the thread title and i noticed it is somehow related to PbO2 :D 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?

Rosco Bodine - 16-7-2007 at 12:14

Quote:
Originally posted by dann2
Hello,

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


From reading patents like US6777477 which are more specific concerning the doped tin oxide composition itself , rather than patents which are focused more generally on anode construction .
Tin oxide which is doped with various other materials to form a solid solution (glass) which is conductive , has been used
for making heating elements which have a glass or ceramic substrate ....and also the transparent formulations have been studied for use in electrically heated glass for windshields or freezer compartments , to defrost or defog the glass . These applications have studied the properties of the doped and conductive tin oxide as a specific interest ,
the whole matter of interest actually , so the data is applicable as well to other uses where the conductive oxide
film would be used .....such as for an intermediate layer in
anode construction .

Quote:

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


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 :P ,
but only if you want to do it right for the first time :D
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:

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 already worked out the multiplier for converting the percentage basis of the Sb metal to Sn metal , to the percentage of Sb2O3 as weight of the combined oxides . It is posted somewhere back in one of these threads . That multiplier will apply to *any* combined salts derived from the
alloy or equivalent .

from earlier post :

Example #2 of the patent US2564707 is 1.4647% Sb2O3 for example which is less than a third of the antimony content of 95/5 .

For purposes of calculation the percentage of Sb2O3 derived from the antimony of a tin antimony alloy converted to the chlorides SnCl4 and SbCl3 and then to the oxides on baking ,
is 94.57% of the percentage value based on the metals .

For example , a 5% antimony / tin alloy will become a
5 X .9457 = 4.7285% Sb2O3 / SnO2 composition .

Quote:

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.


Why not ? If diffusion is necessary for doping (and it is)
then a more liquid phase will diffuse better than a mud .

Quote:

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.

It is precisely equivalent where doping is concerned ....
as there is nothing magic about a precious metal dopant , except in possible greater solubility as a solid solution .
All a dopant does is provide free electrons , possibly have reducing or competing effect which prevents the complete oxidation of the TiO2 interface , but stops it at a substoichiometric O value number that is conductive to AC ,
like TiO1.75 or somewhere thereabouts . This might be accomplished by physically smothering the Ti surface from
exposure to air during baking , or by way of an interfering chemical oxidation of the intermediate oxide acting as a getter for the oxygen which the Ti would otherwise use to passivate at TiO2 formation .

Quote:

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.


IMO ....all of the above answer in the affirmative ,
only if semiconductor theory applies . But as I said , the focus of the patent was not on the optimization of the intermediate layer , but on the construction of a "system"
in which the intermediate layer was likely not at all optimized
and in fact was probably not well done anywhere even near what it could be in terms of an optimization . They were just seeing what might work , not looking for what would work best . The "bean counters" would fine tune the thing later after the general idea was covered in the patent . This is not unusual in patents , and sometimes a careful reading of the ranges desribed in the actual claims will reveal that "preferable" isn't necessarily limited to what is described in the main body of the patent description .
Quote:

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


Thanks for input.


Actually the phase diagram would directly correlate with the electronic values for conductivity based on the percentage of the dopant . The "eutectic" would likely be the most conductive . Electron mobility in the solid solution and physical fluidity of the melt would probably track together
at the same ratio .

I think the variable which *may* require higher levels of Sb in the chlorides precursors is because of the formation of a thicker Ti oxides layer during the baking ,
via a chloride of Ti ....but even if a little extra Sb was needed
it is hard to believe it would be even 20% more ....certainly not a thousand percent more , for the added doping which might be needed for the TiO2 to be reduced or form a mixed oxides ....which it would probably do just as easily with the Tin Oxides . On first examination there would seem to me nothing magic about a TiO2 interface which would have an appetite for so much more Sb ...if you follow , as it would seem to go after the Sn component which is the "solvent"
oxide component of the solid solution , whether it is the Sb2O3 or the TiO2 dissolving to make that doped SnO2 mixed oxides diffusion layer . It is the SnO2 that is the major player ...the carrier and solvent for the dopants .

Look at the Dow patent US4369105 and you will see comparisons of intermediate layers which are undoped SnO2 compared with Sb2O3 16.6% / Sb2O3-SnO2 total . There is very little difference , as the SnO2 does not actually remain
"undoped" during the baking , as it picks up enough doping
from diffusion from the Ti substrate below , and the spinel baked on top ...to increase what would otherwise be its
"undoped conductivity" . Essentially the SnO2 can be used
all by itself ....but the dopants are only to increase its adherence and improve its conductivity ....and those parameters were studied and optimized only on the
parallel technologies involving heating and optical quality coatings on glass substrates ....where any defect would be visibly unacceptable . I can't believe you don't follow what I am trying to say , and I don't know what more I can say to try to connect the dots on this to justify the parallel for
TiO2 and SiO2 substrates . Here they are likely very close cousins and not worlds apart in this sort of layer chemistry .

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

Attachment: US4369105 Substituted_cobalt_oxide_spinels on Tin Oxide coated Titanium Substrate.pdf (157kB)
This file has been downloaded 866 times


dann2 - 16-7-2007 at 20:15

Hello,



Quote:
Originally posted by Rosco Bodine
From reading patents like US6777477 which are more specific concerning the doped tin oxide composition itself , rather than patents which are focused more generally on anode construction .

These's patents are more concerned with getting clear, min.
resistance coatings on glass. They focus on that, not on the
SnO2/ Sb Oxide semiconductor coating thing IMHO.
I am making anodes, not trying to achieve clear transparent coatings of Tin Oxide on glass
that have min. or close to min. electrical resistance.
The optimum ratios of Sn to Sb for Glass, (max. transparency, min. resistance etc)
may not (and probably will not) correspond to what is best for an interface coating between
Ti metal and Lead Dioxide in a severe invironment. I want a coating that stops Lead Dioxide
from Oxidizing Ti and also is resistant to (Per)Chlorate cell conditions and has fairly low
electrical resistance, not a coating that is transparent and has min. resistance.

To put it another way. If we were having a conversation about putting DTO coatings on glass
and someone introduced a patent about DTO in relation to anodes, would it be sensible to
firstly try the higher amounts of Sb?. No.

Quote:

Tin oxide which is doped with various other materials to form a solid solution (glass) which is conductive , has been used
for making heating elements which have a glass or ceramic substrate ....and also the transparent formulations have been studied for use in electrically heated glass for windshields or freezer compartments , to defrost or defog the glass . These applications have studied the properties of the doped and conductive tin oxide as a specific interest ,
the whole matter of interest actually , so the data is applicable as well to other uses where the conductive oxide
film would be used .....such as for an intermediate layer in
anode construction .


You cannot simply extrapolate the facts and data regarding DTO used on glass/ceramic for
certain applications and bluntly state that it is directly relevant for using as an
interface coating between Ti metal and Lead Dioxdie to stop the Lead Dioxide from
Oxidizing the Ti in a hell environment.







Quote:


IMO ....all of the above answer in the affirmative ,
only if semiconductor theory applies . But as I said , the focus of the patent was not on the optimization of the intermediate layer , but on the construction of a "system"
in which the intermediate layer was likely not at all optimized
and in fact was probably not well done anywhere even near what it could be in terms of an optimization . They were just seeing what might work , not looking for what would work best . The "bean counters" would fine tune the thing later after the general idea was covered in the patent . This is not unusual in patents , and sometimes a careful reading of the ranges desribed in the actual claims will reveal that "preferable" isn't necessarily limited to what is described in the main body of the patent description .


There is no basis to say that the people that put the DTO on
Ti patents together were simply cobblying together patents
in a hurry to make a claim.
They may have spent hugh amounts of time getting a
coating that suits the particualr application. Hell environment,
with LD trying to oxidixe Ti.
Have I read a single patent yet that had not got the word
'preferable' in it. :-)




Quote:

Actually the phase diagram would directly correlate with the electronic values for conductivity based on the percentage of the dopant . The "eutectic" would likely be the most conductive . Electron mobility in the solid solution and physical fluidity of the melt would probably track together
at the same ratio .

Snip

That may be true, but will the doping percentages used for desirable parameters
in the conductive glass coating applications give us desirable
parameters that we want for our coating between Ti and Lead Dioxide.
I have me doughts.

Quote:


SNIP SNIP.


Essentially the SnO2 can be used
all by itself ....but the dopants are only to increase its adherence and improve its conductivity ....and those parameters were studied and optimized only on the
parallel technologies involving heating and optical quality coatings on glass substrates ....where any defect would be visibly unacceptable . I can't believe you don't follow what I am trying to say , and I don't know what more I can say to try to connect the dots on this to justify the parallel for
TiO2 and SiO2 substrates . Here they are likely very close cousins and not worlds apart in this sort of layer chemistry .



SiO2 and TiO2 may be worlds appart in these's applications.
I certainly don't know.
You may of course be correct.
Is using the 'correct' amount of Sb in the anode patents ruinging my DTO coatings?


Perhaps I am using too much Sb and this is ruining my coat. I will certainly try
less Sb.
It is interesting to note that **ALL** examples used in the DTO patents, let they
be Glass or Ti substrate with LD or Cobalt or whatever on top have used SnCl4 (or
SnCl4:2H20) as the source of Tin Oxide. None have used SnCl2 or other Tin compounds.
It would seem that the actual source of the Tin Oxide is important.
I do not have much faith is using SnCl2. The SnCl4 (via. SnCl2 + Peroxide)
should work I guess. Perhaps I should go back and start again.

Could some good soul write me an equation or explanation of how
H2O2 converts SnCl2 to SnCl4?

If the lower Sb does not work I will be going back to SnCl4 made the hard way
and will be following the DTO patents that are specifically related to achiving
a robust, sufficiently conductive layer between Ti and LD in a hell environment.
A 'substitute for Platinum' layer versus a see-through, max. conductance layer :-)
If that does'nt work then I will start on the conductive coatings on glass stuff...


Dann2

dann2 - 16-7-2007 at 20:25

Hello Hashashan,

Lead Dioxide?????? did you say.......


Quote:
Originally posted by hashashan
Well just had a look at the thread title and i noticed it is somehow related to PbO2 :D 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?


You could just put the PbO in a second tank and use a filter to catch any PbO that is going back to the plating tank.
You may need to heat the second tank to keep the temperature in the plating tank from varying as fluid comes accross.

A figure often quoted in the patents is to have a few grams of free HNO3 acid per liter of the plating tank. This may be hard to achieve as PbO can sometimes not react too readily with HNO3 and will sit at the bottom of the tank and not react. It depends on the way the PbO was make. Try reacting some of it with weak nitric acid solution to see how reactive it is.
Are you using a pump?
If the PbO is not too reactive you may get away with leaving it in the plating tank and the acid will react with it there.
This may save you the bother of the second tank.

Dann2

hashashan - 16-7-2007 at 21:39

The second tank is not really a bother' i already made it(put 2 pipes into the second erlenmeyer' one inside and the other will be pumped back to thye main cell because the flask will get full.
I do intend to use a pump with a pipe going all the way down to the second tank so increasing the chance for the PbO to react with the nitric acid.
Wont the PbO just fill the liter and get it jammed? thats why i prefer to use some sort of teabags

another thing : my PbO is kind of weired' it comes like a mixture of 3 colors mostly golden and some white and red.

[Edited on 17-7-2007 by hashashan]

hashashan - 16-7-2007 at 21:40

Sorry double post

[Edited on 17-7-2007 by hashashan]

Rosco Bodine - 17-7-2007 at 00:10

@dann2

On the peroxide reaction .....probably

SnCl2 + 2 HCl + H2O2 -----> SnCl4 + 2 H2O


I surveyed the published *relevant* technology from many sources and gave you my interpretation of what it means and why it is relevant .

I don't think there is anything I can say to make you understand that the SnO2 is the operative component of the intermediate layer .

You seem to be zeroed in almost obsessively on one patent process as the be all to end all concerning ultimate knowledge about the Sb dopant percentage ,
when Sb doping isn't at all the principal focus of the patent . And you seem to reject what might fill in the blanks about that intermediate layer , if the information that is more specialized is drawn from a parallel technology . Take off the blinders for a minute and just see that what is being described is a vitreous enamel
having special electrical and mechanical properties ,
and that is primarily what it is about ....not what it is
melted onto , but is like hot resin poured onto a tabletop and meant to stick well and set up to a tough coating .

The purpose for the intermediate layer is more of a sealant against electrolyte permeation than is it a
protectant for the titanium to prevent its being oxidized chemically by the PbO2 . And the PbO2 can actually be plated directly onto the titanium without any intermediate layer and it will be a conductive interface . See US4026786
http://www.sciencemadness.org/talk/viewthread.php?action=att... which I posted
about halfway down page 18 of this thread relating to the 100 g HNO3 per liter highly acidic Pb(NO3)2 plating
method used on bare titanium . There have been other examples for titanium and also examples of bare metals more easily oxidized than titanium being plated with PbO2 .

For the purpose of sealing the titanium better , a vitreous baked on coating provides a second barrier , so that the
titanium is not exposed to the electrolyte by any permeation which might get through a less perfectly
sealing electroplated working coating of PbO2 or whatever else . The same sealing layer might have
a spinel working layer over its outside , and certainly there is no need there to protect the titanium from oxidation by the spinel which is virtually inert . So
is the intermediate layer then serving a different function , not at all ...it is the same .

The highest conductivity , most adherent and physically tough vitreous layer is what is desired .....and those
parameters were not optimized for a titanium substrate
nor for any other substrate for that matter ....but with regards to the composition of the vitreous coating itself .
Putting that fired baked on vitreous coating onto gold or glass , porcelain or platinum , or titanium is most likely and largely irrelevant to the chemistry of the coating itself .

And about the series of Diamond Shamrock patents ....
Quote:
There is no basis to say that the people that put the DTO on
Ti patents together were simply cobblying together patents
in a hurry to make a claim.


That was precisely what was my impression of what they were doing .....hurried work ....and repetitive patents
concerning a tiny incremental progress , bleeding their employer with patent fees on a dozen patents of
dubious value for improvements ....when two or three
at most would probably do .

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

dann2 - 17-7-2007 at 11:04

Hello Rosco,


Quote:
Originally posted by Rosco Bodine
@dann2

I don't think there is anything I can say to make you understand that the SnO2 is the operative component of the intermediate layer .

You seem to be zeroed in almost obsessively on one patent process as the be all to end all concerning ultimate knowledge about the Sb dopant percentage ,
when Sb doping isn't at all the principal focus of the patent . And you seem to reject what might fill in the blanks about that intermediate layer , if the information that is more specialized is drawn from a parallel technology . Take off the blinders for a minute and just see that what is being described is a vitreous enamel
having special electrical and mechanical properties ,
and that is primarily what it is about ....not what it is
melted onto , but is like hot resin poured onto a tabletop and meant to stick well and set up to a tough coating .


The Sn02/ Antomony Oxide 'system' or whatever we like to call it is absolutely not a Vitrous enamel. Max. baking temp. we go to is about 480C. Melting temp. of Tin Oxide is 1800 to 1900C.
We are converting decomposable Tin + Sb compounds to Oxides. The starting materials, ratios, and carryiers and substrate may have very important roles. Saying they have not is guessing.

Quote:

The purpose for the intermediate layer is more of a sealant against electrolyte permeation than is it a
protectant for the titanium to prevent its being oxidized chemically by the PbO2 .


ALL industrial Titanium substrate Lead Dioxide anodes have had a coating of Platinum applied to the Ti. They fail other wise. We are looking for a cheap alternative to Platinum.

Quote:

And the PbO2 can actually be plated directly onto the titanium without any intermediate layer and it will be a conductive interface . See US4026786
http://www.sciencemadness.org/talk/viewthread.php?action=att... which I posted
about halfway down page 18 of this thread relating to the 100 g HNO3 per liter highly acidic Pb(NO3)2 plating
method used on bare titanium .

Electro winning of Metals in acid solutions only. This is a relatively 'easy' job for anode. Lead + Silver anodes (amongst others) have been used in this application. Try using a Lead + Silver anode in a Chlorate cell. Big mess.

Quote:

There have been other examples for titanium and also examples of bare metals more easily oxidized than titanium being plated with PbO2 .


Most of the 'attackable' substrate anode have been used as massive anodes. ie. once made, the substrate is ignored and the electrical connection made to the Lead Dioxide or were experimental anodes in a journal artical.


Quote:

For the purpose of sealing the titanium better , a vitreous baked on coating provides a second barrier , so that the
titanium is not exposed to the electrolyte by any permeation which might get through a less perfectly
sealing electroplated working coating of PbO2 or whatever else . The same sealing layer might have
a spinel working layer over its outside , and certainly there is no need there to protect the titanium from oxidation by the spinel which is virtually inert . So
is the intermediate layer then serving a different function , not at all ...it is the same .



My bottom line is that you cannot treat the DTO layer is theses applications in isolation. The substrate, on one side, and the outer coating, on the other side, are part of the 'system'.
A DTO interface + Spinel patent is here:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
Quote:
________________________________________----
It is believed that the interface layer of the present invention functions by reacting with the valve metal oxide as it is formed on the surface of the substrate, rendering it electrically conductive. The mechanism by which this is accomplished is uncertain. Trivalent metals such as indium may function as conventional semi-conductor dopants in the (tetravalent) valve metal oxide lattice; tetravalent metals such as tin may form conductive solid solutions with the valve metal oxide, analogous to RuO.sub.2 -TiO.sub.2 solid solutions_____________________________---

The substrate in involved. *fact*.
The outer coat may be too.
The spinal patents are also not directly relevant to our discussion regarding DTO between Ti and LD for (Per)Chlorate making.
The Spinel pat's and the Corning pats have there own problems to overcome and goals to achieve.
Does Si02 alloy with Tin Oixde?? I don't know.
But TiO2 does.


Quote:

And about the series of Diamond Shamrock patents ....
Quote:
There is no basis to say that the people that put the DTO on
Ti patents together were simply cobblying together patents
in a hurry to make a claim.


That was precisely what was my impression of what they were doing .....hurried work ....and repetitive patents
concerning a tiny incremental progress , bleeding their employer with patent fees on a dozen patents of
dubious value for improvements ....when two or three
at most would probably do .

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


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 :D



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............ :o


Dann2

Eclectic - 17-7-2007 at 13:10

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! :o

[Edited on 7-17-2007 by Eclectic]

Rosco Bodine - 17-7-2007 at 16:58

@dann2

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

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 :P 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]

dann2 - 17-7-2007 at 20:39

Hello,

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! :o

[Edited on 7-17-2007 by Eclectic]


Sorry, I missed that.

I have just tried a lower Sb dopant amout (about 5 %) using SnCl2:2H2O.
I got a similar coating to the higher dopant amounts.
I also tried converting SnCl2:2H2O to SnCl4 via H202 in HCl.
I got a ppt when I added the Sb Chloride.
Will give a more detailed explanation later.
Coated anyways but it was not resistant to Chloride electrolysis.

Away past 1984. Don't get it. Do you mean the date of some patent???

Why do all (or all as far as I can see) use SnCl4:5h2O (or Anhydrous SnCl4) to achive the DTO coatings? In all the examples they use SnCl4 (5H2O). They list Tin compounds in the patent body's but never seem to have actually used them.

Cheers,

Dann2

dann2 - 17-7-2007 at 20:54

Hello,

Rosco, your bottom line is that the reason I am not getting good coatings of DTO is that I am using too much Sb.
I will lower my Sb (have already gone to 5% with failure) to see how things go.
Some of the 'dodgy' Shamrock patents have electrolysed Brime for hours using the DTO (high Sb) alone.
I can do even better with lower Sb?
At 5% there is no improvement but I am using SnCl2 so that may not be good.

Dann2

Rosco Bodine - 17-7-2007 at 22:34

Quote:
Originally posted by dann2
Hello,

Rosco, your bottom line is that the reason I am not getting good coatings of DTO is that I am using too much Sb.
I will lower my Sb (have already gone to 5% with failure) to see how things go.


Yeah and possibly a part of the problem is the volatility
of SnCl4 which causes an increase of the relative percentage
of dopant , since an unknown amount of the Sn is lost during drying and baking . The proportions you end up with in the
deposited oxides could be much different from what you were intending . The properties of the SnCl4 itself make it a user unfriendly material as a tin(IV) oxide precursor. That's another reason I liked the idea of the ammonium stannate / ammonium antimonate dopant system ....it has a better
sol / gel dispersion during the decomposition and transition
to a solid solution on baking and it isn't volatile nor corrosive nearly so much as are the chlorides . However that corrosiveness may be necessary for the diffusion layer at the titanium interface ...and this is the one point of possible difference that I do recognize concerning a titanium substrate . That accounts for my interest in the possibility
of a "cold bluing" using cobaltous acid , or a chromating ,
as a strategy for producing a transient protective layer
which would itself transform into a conductive doped diffusion layer during baking ....eliminating the need for
a corrosive and volatile chlorides precursor for the intermediate layer . It is also along the same line of thinking
that made the "blue titania" titanium suboxide anodization
by electrolytic treatment with KOH , attract my attention
in that rectifier patent US2711496 ....as that seemed like
a controlled surface oxidation which might well take a cold
depassivation treatment with a chromate or some other cold process surface treatment which would then diffuse on baking into an intermediate layer . These sorts of strategies
would seem much more controlled than the baking schemes
using corrosive chlorides . I haven't really liked the idea of chloride precursors from the beginning because there is a lot that can go wrong . Rate of heating , viscosity of the solution
are two huge variables .

Quote:

Some of the 'dodgy' Shamrock patents have electrolysed Brime for hours using the DTO (high Sb) alone.
I can do even better with lower Sb?


IMO yes it is keeping the Sn percentage up that is going to be the challenge . Maybe the higher Sb was for chemical resistance at the cost of all other parameters ....or maybe it was an anomalous tertiary mixed oxide peculiar to titanium ,
but I think it was more likely just not a fully quantified and evaluated parameter .

Quote:

At 5% there is no improvement but I am using SnCl2 so that may not be good.

Dann2


When I first saw these patents specify SnCl4 , I thought it must be a typo and that they were probably using SnCl2 ,
wondering how you would bake SnCl4 onto anything since it
boils at 114C . It still seems like an awkward precursor for
any baking scheme .....because how much stays where you put it and actually deposits as SnO2 during decomposition ,
minus that which blows away on the wind ? Evidently the
"drying" temperature rate and time is important , to allow for
evaporation of HCl and progressive hydrolysis of the SnCl4
to non volatile decomposition products *before* the higher temperature baking .....or else the SnCl4 will simply flash boil away in significant amount . Yet nearly instant heating much hotter will overcome that , according to the Corning patent ....so there seems to be some contradiction . Some finesse is evidently required to make this baking scheme work using the SnCl4 precursor . Perhaps a bit of ethylene glycol added to the mix , may smooth the decomposition and lower the volatility of the SnCl4 .

[Edited on 18-7-2007 by Rosco Bodine]

Eclectic - 18-7-2007 at 10:32

SnCl4.(H2O)x is not going to be volatile like the anhydrous SnCl4 is. You will get hydrolysis to SnO2 as the HCl is driven off.
SbCl3.(H2O)x, however, will dehydrate and volatize to some extent.

1984 is a novel by George Orwell.

Rosco, I'm fairly sure you will need a strongly acidic system to get through the surface layer of TiO2 and keep it dissolved, unless, perhaps, you do the HCl pre-etching with strong HCL with a lot of SnCl4 dissolved in it and try to get a Sn flash coating to prevent surface oxidation.

I'm fairly sure the SnCl4 coating solution needs to have a bare minimum of water in it to avoid formation of powdery SnO2 as it dries. That's why I recomended evaporating to crystalization and redissolve with a minimum amount of HCl. Some precipitate will remain and can be settled out or filtered with a glass fritt funnel and cellite filter aid. Too much H2O2 makes more poorly soluble precipitate.

dann2 - 18-7-2007 at 13:44

Hello,



Quote:
Originally posted by Eclectic


Snip

I'm fairly sure the SnCl4 coating solution needs to have a bare minimum of water in it to avoid formation of powdery SnO2 as it dries. That's why I recomended evaporating to crystalization and redissolve with a minimum amount of HCl. Some precipitate will remain and can be settled out or filtered with a glass fritt funnel and cellite filter aid. Too much H2O2 makes more poorly soluble precipitate.


I missed that along the way.
You would recommend crystallizing out the SnCl4:5H20
and going from there?



Anyways I attempted some DTO coats.

Note that my source of Sb is from homemade SbCl3 in HCl.
This (stock) solution contains 0.41% Sb.

I attempted to obtain a DTO coating using Sb at 5%

2 grams SnCl2:2H2O
0.13 grams of my SbCl3 (stock) solution in HCl (contains 0.41% Sb)
4ml ISO-Propyl alcohol (surgical spirit)
0.7 grams HCl (35.4%)
I obtained a water clear solution for painting with.

Painted using quick single strokes. One coat only per bake.
3 bakes total (ie. three coats total)
The coating could be rubbed off using small strokes of Steel wool.
The Ti strip passivated soon after it was put into a Chlorate cell.

I do not have much faith is SnCl2 as all patents use SnCl4 in their
examples. It is easily obtainable for me though.




I preformed another coating attempt using SnCl4 made from
SnCl2:2H2O + H2O2 + HCl.
This was a (high) 20% Sb content coating.

Added 4 grams SnCl2:2H2O to 2.4 grams HCl. Cooled down and also cooled down
H2O2 using salt and ice. Added one drop of Ti indicator solution.
Added a untill Ti indicator went orange. (about 3g 30% H2O2)
Added 12.3ml surgical spirit.
Added 1.28 grams SbCl3 (stock) solution in HCl (solution contains 0.41% Sb)

As soon as I started to add the SbCl3 solution I got a white PPT.
The solution went milkey white.
Went ahead and painted and baked. Three bakes, one coat per bake.
The Ti passivated after about 1.8 minutes in Chlorate cell.
I will attempt to dissolve ppt using HCl some other time and try again
with this solution.

I repeated the above paint formula only this time I added in the SbCl3 stock
solution before I converted the SnCl2 to SnCl4 (using H2O2).
Towards the end of adding in the H2O2 the milkey white ppt appeared.

What is the ppt do you think?

Just before posting this I see Eclectic mentioned too much H2O2 will give a
poorly soluble ppt. Would too much H2O2 cause a Sb ppt.?




The 'test' I am peforming on the DTO coated Ti consists of
connecting a current limited power supply to the anode.
The current is set to 40mA per square cm on the anode. This
takes about 4.5 volts to achieve. The voltage will rise up and up
as the Ti passivates. When it gets to 10 volts I consider the
DTO/Ti anode to have failed. This took about 1.8 minutes to happen
on the last coating attempt.



I hope to do another coating/baking attempt using 'home made' SnCl4
(make from SnCl2 + H2O2) with a lower Sb content.


Is this forum the appropriate place for 'blow by blow' details like this??

Dann2

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