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dann2
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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
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alancj
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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
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dann2
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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
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12AX7
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More fire? Idunno...
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dann2
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| 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  and getting more
[Edited on 15-7-2007 by dann2]
[Edited on 15-7-2007 by dann2]
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Eclectic
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Pick a recipe and stick with it. You can't expect to make things work by blindly mixing items from column A,B,C,D,etc.
Advice tends to work (when it rarely does) only when you follow ALL the suggestions from a given source.
Make sure you understand the basic principles of what you are doing before you make arbitrary changes to the procedures.
(Sorry, I'm suffering frustration by proxy  )
Look, you need a very concentrated solution of SnCl4 and SbCl3 dopant with enough HCL to keep it from precipitating oxides until you bake off the
solvent. It's not going to make a bit of difference what your starting materials are, just what you end up with in solution.
These chlorides are VERY soluble. I have the equivalent of 3 moles SnCl4 in only 500ml solution with no alcohols added.
[Edited on 7-15-2007 by Eclectic]
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dann2
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Hello Electic,
You have enough solution there to coat an airport runway
I must admit I have 'messed around' quite a bit with the instructions etc. I am not too hot in the Tin chemistry department, or the Sb one either.
Will read what I have written and come back to you but I basically ended up with a solution of the SbCl3 and SnCl4 in HCl (+H2O2? or does it all go
away when you boil the solution). I could not reduce the solution volume anymore as I was starting to get a ppt as I distilled off the acid so I
painted and baked. I do not think this will work but perhaps there is something I have overlooked. My ratio is greater than yours. Mine is 23%Sb to
77%Sn.
I have since tryed SbCl3 (homemade) + SnCl2:2H20 (ebay)
in HCl and Iso-Propyl Alcohol with more success but not a workable undercoat.
Dann2
[Edited on 16-7-2007 by dann2]
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dann2
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DTO undercoat using SbCl3 + SnCl2:2H20
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]
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Rosco Bodine
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If ect. ect. includes my two cents worth .....
~10% Antimony oxides is the upper limit of dopant solubility in the Tin Oxides , and that amount is only attainable using different precursors than
chlorides , along with a high temperature decomposable organic dispersant which holds the oxide and oxide precursor particles well dispersed and
separated until above ~200C . When the mixed oxides layer forms it is a limited fusion , which then solidifies ....it is not the same as a completely
melted phase of totally blended different liquified components ....as it never gets hot enough for that sort of blending . It is a vitreous glaze
sort of layer
which forms and sets during baking , the same as an
enamelware sort of coating as is applied to steel cooking pots .
What you will get with so much antimony is a two phase deposit full of cracks and holes which will take twenty coats to overlap and fill in the pores
and cracks .....
instead of the perfectly sealing level film of a conductive
glass in one to three coats . And the more undissolved antimony in the layer , the worse will be the conductivity and adhesion . So it is better to
have too little dissolved completely than too much having most of it not dissolved .
Using mixed chlorides , try 2% antimony instead of ten times that amount .
I think your experiments will lead straight to the glass substrate experiments where optical quality coatings were the result . And no it's not back
to that again ,
but more like *forward* to that again
[Edited on 16-7-2007 by Rosco Bodine]
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dann2
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| Quote: | Originally posted by Rosco Bodine
If ect. ect. includes my two cents worth .....
~10% Antimony oxides is the upper limit of dopant solubility in the Tin Oxides , and that amount is only attainable using different precursors than
chlorides ,
Snip
Using mixed chlorides , try 2% antimony instead of ten times that amount .
I think your experiments will lead straight to the glass substrate experiments where optical quality coatings were the result . And no it's not back
to that again ,
but more like *forward* to that again
[Edited on 16-7-2007 by Rosco Bodine] |
Hello,
How do you figure that 10% is the max. solubility of Antimony Oxide in Tin oxide?
I will try lowering the Antimony to 5% (I will meet you half way + some )
When I say 5% I mean I will have 5% Sb, 95% Sn by weight in the initial Chlorides. I am calculating the Sn and Sb as if no other 'stuff' is in the
coating. ie. no Cl-, or acid etc.
Does that make sense.? It will be (say) 0.95 grams Sn + 0.5 grams Sb, as SnCl2:2H2O and SbCl3.
I still have SnCl2 and my homemade SbCl3 as I did not use it all in the above coating attempt.
I accept the glass coating etc use smaller amounts of Sb than I have used. Surly DTO on glass is not directly comparable to DTO on Ti. Another Pat.
that Electic quoted uses Pallidium (Chloride) mixed into the bakable paint. This uses low Sb too but it surly is not directly comparable to putting
DTO (using Sb alone as the dopant) on bare Ti.
Perhaps I am missing some very obvious point.
When you say that 10% is the limit of solubility of Sb Oxide in Tin Oxide, is US 4040939 Example 1 not correct, not feisable, wasting Sb? It uses
Chlorides. It uses (approx) 23% Sb.
Perhaps you have a Tin Oxide/Antimony Oxide phase diagram that you do not want to put in the public domain.............
Thanks for input.
Cheers,
Dann2
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hashashan
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Well just had a look at the thread title and i noticed it is somehow related to PbO2 so i decided to ask a question about this.
Made a batch of PbO' in order to use it neutralize the HNO3 from the plating tank. How would you guys recomend me to do it. I am planning to pumb the
liquid through another flask where it will be neutralized' but how can i store the PbO there without it running back to the main cell? Teabags? how
can i make those teabags so they will hold the PbO inside and still allow it to react with the HNO3?
another question, more related to basic chemistry, what is the PH of a lead nitrate solution? it should be acidic, so i think there is no reason to
maintain a certain flow through the neutralizer. If i just neutralize all of the acid that i can i should get an acidic Pb(NO3)2 solution and some
traces of HNO3' just what i need.
so what do you say?
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Rosco Bodine
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| 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 )
|
No no nooooo ....I'll say 0.85% is ideal for the chloride system , but only if you promise to double that and compromise at 1.7% , calculated as Sb2O3
weight in
the total oxides .....and let that be meeting me halfway ,
but only if you want to do it right for the first time
See the Corning patent which sprayed the coating onto a hot substrate for that one . I forget the number , but it dealt with a chlorides based
precursor mix .
Here it is US2564707
http://www.sciencemadness.org/talk/viewthread.php?action=att...
| Quote: |
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.............
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
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dann2
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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 .
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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
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dann2
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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 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
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hashashan
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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]
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hashashan
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Sorry double post
[Edited on 17-7-2007 by hashashan]
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Rosco Bodine
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@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]
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dann2
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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 .
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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 .
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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 .
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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 .
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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 .
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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
And now I am going home to try a 5% Sb + the rest Sn coating. Then a lower Sb% if that does not work.
I think I need to see my head shrinker............ 
Dann2
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Eclectic
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You should be getting doped SnO2 growing out of a SnCl4.(H2O)2 melt during the baking process with HCl being driven off.
Use only enough H2O2 to convert the SnCl2 to SnCl4. If a drop of TiCl3 solution does not stay blue, back titrate with SnCl2 and retest.
You didn't like like my explanation of SnCl2 +2HCl +H2O2 --> SnCl4 +2H2O when I gave it in one of the other related threads? Are you keeping
everything compartmentalized in your head? Doublethink? We're WAY past 1984!
[Edited on 7-17-2007 by Eclectic]
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Rosco Bodine
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@dann2
BTW , Corning glass works is a place where they work mostly with *vitreous* materials ....imagine that
I'll try to keep in mind that the doped SnO2 layer isn't a vitreous coating . It
only deceptively appears to fuse into a perfectly clear glasslike material when it sinters and sets as a solid solution ....perfectly emulating in
every parameter what would be thought to be a vitreous enamel like layer . Of course it cannot be everything it appears and and tests and is reported
to be ,
since dann2 has established the impossibility of any depression of melting point for pure materials mixed with property modifying impurities Depression of melting point .....hmmm ever heard of it ?
Further , now you are citing US4361905 , which I posted
( once again probably ) four or five posts above on this page .......which is saying *exactly* what I have been trying to tell you .....that the SnO2
is the solvent portion
of the solid solution ( vitreous intermediate layer ) in which the other oxides are dissolved as dopants .....
whether it is the deliberately added Sb , or it is oxides
diffused from the substrate .....be those SiO2 or TiO2 ,
which are themselves dielectrics when pure , but dissolved by diffusion into SnO2 as impurity dopants ,
the otherwise poorly conductive SnO2 becomes a hundred to ten thousand times more conductive than
pure SnO2 . Typically such semiconductor doping is
done at levels of tenths of a percent to a few percent ,
*not* tens of percent . You don't have a solid solution doped tin oxide then , but a mixture of tin oxide doped to saturation , mixed with
undissolved aggregate of excess
dopant solids which detracts from every quality about the intermediate layer which was desirable at a much lower percentage where the dopant quantity
was well below saturation .....like 14% of saturation for example .
Your focus on the Sb content as being so crucial is nonsense .....it is the SnO2 that is the solvent , or
matrix into which the other materials diffuse , so to account for the upward diffusion of Ti oxides from the substrate , Sb would function as a
competition solute ,
not as an enhancer of the Ti to SnO2 diffusion layer .
If the SnO2 is already loaded with more Sb2O3 than it can dissolve , then it can't interact very well as a diffusion layer for the Ti interface
....because it is already *saturated* with Sb dopant . It will be like trying to dissolve sugar in honey , because the SnO2 is already
thick with dopant . And BTW best conductivity is a very definite desirable parameter for the intermediate layer ,
and when the Sb dopant percentage exceeds ~2%
for a chlorides derived mixed oxides .....the conductivity
drops exponentially .
There is a possiblity I suppose of some tertiary eutectic effect
that could exist for the Sb / Ti doped SnO2 ...but that would seem unlikely , given the examples where SnO2 alone is used
and relies for doping only on whatever diffusion occurs indigenously from the substrate below and the spinel above .
The voltage data for the anodes having undoped SnO2 alone is a good indicator that very little added doping is needed . I would fully expect that a
lower Sb content than they are using , would be much better . What I get from their charting is that the SnO2 used alone is dopant poor ,
and their ratio of Sb to Sn in the doped SnO2 is dopant overloaded .....they went above and below the optimum ,
but never tried to extrapolate from there by more experiments , precisely what the optimum doping would be .
That's where the Corning patent data becomes helpful ....
not conclusive ...no ....but giving you something more to go on .
Hey if you want a grungy poorly conducting pore and crack filled poorly adherent flaking off mess for your intermediate layer .....go ahead and
follow the high dopant percentage model .
Or if you would prefer a highly conductive , optical grade coating ....then invest some confidence in the relevant data .
[Edited on 17-7-2007 by Rosco Bodine]
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dann2
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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!
[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
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dann2
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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
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Rosco Bodine
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| 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]
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Eclectic
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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.
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dann2
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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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