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dann2
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Hello,
I have had success using the procedure described in the above paper to obtain a coating of Tin Oxide using SnCl2.
I used Sb as opposed to Ce as the dopant.
Anode has ran in a Chlorate cell for 30 hours or so. It's good to go as an undercoat between LD and Ti.
The procedure eliminates the need for SnCl4:xH2O which can be difficult to obtain.
Dann2
[Edited on 8-9-2010 by dann2]
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dann2
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Hello,
I thought someone might be interesed in the exact procedure I used to obtain Tin Oxide coating VIA SnCl2
Conductive Tin Oxide coating via Stannous Chloride (SnCl2)
Most Tin Oxide coatings on Ti have been achieved via SnCl4 (Stannic Chloride) which is somewhat difficult to obtain and not very easy to make.
The following scheme works well and uses Stannous Chloride which can easily be made from Tin metal and HCl or purchased.
It is taken from J. Material Sci. Technol., 2010, 26(2), 187-192.
"Active Stainless Steel/SnO2-CeO2 Anodes for Pollutants Oxidation Prepared by Thermal Decomposition."
(The paper is two posts above)
The procedure requires a reflux apparatus which need not be very elaborate. The prodedure from the article is as follows:
The precursor solution of SnO2-CeO2 was prepared by dissolving 4.52g SnCl2:2H2O and
0.09g CeCl3:7H2O in 50ml Ethyl alcohol. Firstly, the solution was stirred at room temperature
for 30 min. Secondly, the solution was heated and refuxed at 80C for 5 h. And then, after
sealing at room temperature for 24 h, the precursor solution was finally formed, which was
light yellow and transparent.
Antimony or other compounds can be substituted for the Ce dopant.
Detailed description
2.5 grams SnCl2:2H20 was dissolved in 15ml Distilled Methylated spirits.
0.52g of a liquid containing 31.8% Sb was added. (The Sb liquid was made from Antimony metal + HCl + H202.)
The solution turned slightly milkey due to the presence of water. (It went clear when reflux started.)
The solution was then stirred for approx. half an hour at room temperature and then refluxed for 5 hours. At the end of reflux the solution was
slightly cloudy.
The solution was put into a stoppered bottle and let sit 24 hours. At this stage it was very slightly yellow and slightly cloudy.
A piece of Grade 1 Ti that had been etched for approx. 2 hours in 12% HCl at 90°C was washed in clean water and dried with a heat gun. The Ti was
then liberaly brushed with the solution and let drip dry for 5 minutes.
The Ti was then shaken to remove excess solution and dried using the heat gun. The Ti was kept moving while the drying was taking place so that
puddles of solution did not form on any areas of the Ti.
This solution application and drying procedure was carried out twice more and the Ti was then baked in an oven at 480°C for approx. 7 minutes.
The Ti received three more coats of solution + bake and then three more coats of solution + bake (9 coats and three bakes total).
The Titanium was a deep blue colour when finished.
It was placed into a Chlorate cell and was still running OK after a week with 4.2 Volts accross the cell at an Anode current density of approx. 70mA
per square cm.
Distilled Vodka (90% Ethanol + 10% water) was also used as the solvent instead of distilled Methylated spirits. When the Antimony liquid was added the
solution went very cloudy with a large precipitation of white Antimony Oxide. The solution was refluxed and most of the cloudyness disappeared. This
solution was also successful at forming conductive ATO coatings on Ti. Anhydrous Ethanol is probably best if you can obtain it.
Would F do as a dopant?
Dann2
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bbartlog
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Nice, detailed description. Might try this some time. One question: is the baking temperature of 480°C necessary? My regular household oven obviously
doesn't reach such temperatures and while I can easily get it that hot in a vessel heated by other means the temperature control I can get at higher
temps is not currently that great.
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dann2
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Hello bbartlog,
AFAIK you need to go to these temperatures when working with Tin Oxide. All Tin Oxide coatings on Anodes (however they are achieved) seem to be always
given a final bake at close to 500C.
I think it's fair to assume that you can substitute Tin/Antimony solder dissolved in HCl + H2O2 for the solid (ebay) SnCl2 + Antimony liquid (metal +
HCl + H2O2) that I used. That make the whole thing OTC.
The Anode made above using the distilled Vodka (6% water 94% Ethanol) has failed after a few hours testing so I am guessing that water is a no no.
Dann2
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dann2
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ATO from OTC solder
Hello,
I attempted the procedure above using Tin/Antimony (95/5) solder and had success. I do not have any solder so I had to actually make some from Tin and
Antimony. I had spend some time trying to achieve this approx. 2 years ago without success. The procedure I used is below. It's the same as the
procedure above except that you just make the Chlorides from the solder.
________________________________________
Tin/Antimony solder can be had OTC in some places so it was decided to attempt an ATO coating using 95% Tin + 5% Antimony solder. First a small amount
of the solder was made from Sn and Sb. If purchasing solder the contained flux (if present) may have to be removed by heating the solder and burning
it off.
3.25 grams Tin and 0.17 grams Antimony were melted together and mixed in an Iron timble. The still molten contents were emptied out onto a piece of
glass so as to form a thin sheet. This was cut into a number of small pieces and added to 30 ml (about half this amount would probably suffice) of 20%
HCl and refluxed in a round bottomed flask with stirring. After approx. 45 minutes all the Tin had dissolved leaving the Sb as a fine powder. Two ml
of 35% Hydrogen Peroxide was added dropwise (careful) and the Antimony reacted within a few seconds. A clear solution (very small amount of
cloudyness) resulted. The solution was heated on an oil bath at 150°c with stirring untill there was just a very small pool of liquid (approx. 2 cc)
left at the bottom of the flask. As HCl was coming off ventilation was needed. Some solid Chlorides deposited on the sides of the round bottom flask.
It may be helpful to attach some vaccuum to the flask to speed things up. The small amount of liquid solidified when the flask cooled down and when
dissolved in 30ml of solvent it was found that the weigh of the Chlorides was 6.8 grams. A further 38ml of distilled Methylated spirits (68ml total)
was added to the Chlorides in the flask and stirred at room temperature for half an hour. The solution was then refluxed for 5 hours and then let
stand for 24 hours in a stoppered bottle (ie. same procedure as above using purchased SnCl2 and Antimony Chloride).
An attempt to use 12% HCl for reacting with the solder was first made but a large amount of Oxides formed. The water content was probably too high.
20% HCl or greater is needed. Anhydrous Ethanol would probably be better than the distilled Methylated spirits of you can get it. 190% proof Ethanol
is NOT OK. The Methylated spirits was distilled using a fractionating column. The first 10% of distillate and the last 5% (still in boiling flask) was
discarded.
The ATO precursor solution now had a very slightly yellow colour.
A piece of Ti was etched in 12% HCl for approx. one hour at 90°C , washed in water and dried using a heat gun. The Ti was painted liberally with the
solution and let drip dry for 5 (this may be important) minutes. The Anode was then given a good shake and dried using the heat gun. The Ti was kept
moving when drying so that no puddles of precursor were formed on the Ti. This was repeated twice more and the Anode then baked at 480°C for about 8
minutes. The Anode then received two more bakes with 3 coats per bake. (Total of 9 coats and 3 bakes).
The Anode did not passivate when used to electrolyze NaCl solution. The Voltage accross the cell when the Anode was placed into the cell for the first
time was low at 3 Volts. This is always a good sign of a successful ATO coat on Ti.
______________________________________
Dann2
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Eclectic
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FINALLY! YAY! Almost verbatim what I suggested 2 years ago...
(Well, to be fair, you DID cleverly use the alcohol bit after prepping the aqueous chlorides mixture.)
[Edited on 10-4-2010 by Eclectic]
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dann2
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Quote: Originally posted by Eclectic  | FINALLY! YAY! Almost verbatim what I suggested 2 years ago...
(Well, to be fair, you DID cleverly use the alcohol bit after prepping the aqueous chlorides mixture.)
[Edited on 10-4-2010 by Eclectic] |
Huh!!!
That would have been the ShakeAndBake® 
The H202 was to get the Sb to react with HCl.
What happens when the Tin and Antimony Chlorides are refluxed in the Alcohol for the 5 hours?
Does some sort of Tin/Antimony Alkoxy compound form?
________________________________________
Eg. from US 3627669
A solution of an alkoxy-tin compound was prepared by boiling under reflux for 24 hours a mixture of 15 g. of stannic chloride and 55 g. of n-amyl
alcohol. Into the resultant solution were dissolved 2.13 g. of antimony trichloride.........
____________________________________________
Cheers
Dann2
[Edited on 4-10-2010 by dann2]
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Aqua_Fortis_100%
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| Quote: Originally posted by dann2 | Hello,
I have had success using the procedure described in the above paper to obtain a coating of Tin Oxide using SnCl2.
I used Sb as opposed to Ce as the dopant.
Anode has ran in a Chlorate cell for 30 hours or so. It's good to go as an undercoat between LD and Ti.
The procedure eliminates the need for SnCl4:xH2O which can be difficult to obtain.
Dann2
[Edited on 8-9-2010 by dann2] |
Hello Dann2, I think you will like that article, it was made in 2005, but I found it ocasionally today:
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S... (pdf format: http://www.scielo.br/pdf/qn/v27n6/22271.pdf )
Here, they use both SnCl2-SbCl3 and SnSO4-Sb2(SO4)3 to compare with regular SnCl4*5H2O method.
As spected, SnSO4 baked anode was hopeless and will not be good (MEV pics very diverging with SnCl2 anode).
Its an interesting read, since they found that even with less coats/bake cycles, you can achieve a thicker ATO film than with SnCl4 method. The SnO2
from SnSO4 method only showed somewhat good on platinized Ti.
"HOW TO":
| Quote: |
EXPERIMENTAL PART
Pretreatment of the substrate
The pretreatment of the substrate (Ti) is one of the most important factors to control the quality of the coating of SnO2. However, there are a
variety of methods of pretreatment, and significant differences are observed in their results. We chose to use the procedure reported by Lipp and
Pletcher [4], who had electrodes with good reproducibility. Thus, the working electrodes (strips of titanium - 0.25 mm x 1 cm x 4 cm - from Aldrich
®, 99.7% purity) were subjected to the following pre-treatment:
a) Blasting the surface of Ti using glass microspheres with grain size from 60 to 70 micrometres followed by ultrasonic cleaning bath for 20 min,
immersed in 2-propanol;
b) Before preparation of the oxide film, etching of Ti in boiling concentrated HCl for 1 min, followed by profuse rinsing with water and air drying.
In some cases, the substrate so pretreated was platinized through a galvanostatic electrodeposition (250 mA cm -2), using a solution of H2PtCl6 (20 g
L -1) + HCl (300 g L -1) at 65 ° C for 10 min; a cylindrical platinum net was used as counter electrode.
Preparation of SnO2 films
After all the pre-treatment steps have been completed, the oxide films were prepared as follows:
a) Application, with a soft brush, a thin layer of an alcoholic (2-propanol) solution of SnCl2*2H2O 13% w/v 3 + SbCl3 0.2% w/v or SnSO4 12.3% w/v +
Sb2(SO4)3 0.15%, evaporating the excess alcohol in air oven at 90°C for 10 min;
b) After two applications, formation of oxide layer thermally in an oven at 500°C for 20 min with a slow, continuous flow of oxygen;
c) Repetition of steps a) and b) by 10 times;
d) Annealing the film in the oven at 500°C for 60 min with a slow, continuous flow of oxygen.
The thickness of obtained films was estimated from their mass, taking into account the density of the oxide and its coverage area (see below).
|
.....
Now, see this:
| Quote: | Thickness estimative of the SnO2 films
...
In the case of films using the precursor salts SnCl2*2H2O and SbCl3, the mass of films and their thicknesses varied in the range from 22.2 to 33.5
g*m-2 and 3.2 to 4.8 micrometres respectively, for a total of 10 applications, so the average value of the estimated thickness (and standard
deviation) for these films is (3.8 ± 0.6) micrometers. Lipp and Pletcher, using a precursor salt of Sn[+4] doped with Sb[+3], reported mass and
thickness in the range of 16-25 g*m-2 and 2.2 to 3.4 micrometres, respectively, for a total of 24 applications.This shows that the precursor
Sn[+2] studied in this work, even with fewer applications, features SnO2 films thicker than those reported by Lipp and Pletcher. It should be noted
that in all cases the content of Sn[+2] in the solution used was the same as that of Sn[+4] used by Lipp and Pletcher.
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If you folks wants the full translation I can make it in few days.
Cheers
[Edited on 25-1-2012 by Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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dann2
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They could get SnCl2 to work by a simple 'paint & baking' process. I could never get it to work. I always had to use SnCl4:5H2O.
Just wondering who are Lipp and Pletcher?
Dann2
[Edited on 25-1-2012 by dann2]
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Aqua_Fortis_100%
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I dont understand, there are minor diferences in your procedure that give it to work properly. Of these the major difference is applying 3 coats +
bake whereas they bake after every coat and give the final annealing after 10 applications/bake cycles. I dont know what could be wrong in your
process to apply/bake/apply/bake/etc, but they apparently did succeed in obtaining stable SnO2 coating from SnCl2 baking. Note air is always present,
they used (slow) air flowing when at baking stage.
Lipp and Pletcher are authors of the article using SnCl4 procedure referenced in abovementioned study:
| Quote: |
"The preparation and characterization of tin dioxide coated titanium electrodes"
Abstract
The selection of an appropriate pretreatment of the substrate as well as coating procedure allows the preparation of stable SnO2 coated titanium
electrodes. Such electrodes have been operated in O2 evolution for > 1000 h without unacceptable loss of activity and may be used as anodes for the
oxidation of redox couples and organic molecules.
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http://www.sciencedirect.com/science/article/pii/S0013468696...
Unfortunately I can get the full document on my hands, this seems to go for references board.
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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jpsmith123
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SnO2 + CeO2 Over Stainless Steel
Here's an interesting paper about anodes made using a precursor solution of SnCl2.2H2O and CeCl3.7H2O in ethyl alcohol. The substrate was stainless
steel. Although the anodes in this case were intended for wastewater treatment, it might be worth testing for ClO3 and ClO4 as well.
Attachment: Active+Stainless+Steel_SnO_sub_2__sub_-CeO_sub_2__sub_+Anodes+for+Pollutants+Oxidation+Prepared+by+Thermal+Decomposition (473kB)
This file has been downloaded 756 times
[Edited on 28-1-2012 by jpsmith123]
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jpsmith123
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I see that Dann2 already posted that paper a while ago. I don't know how that escaped me.
Anyway, hopefully this coming week I'll be doing my first experiments trying to electro-co-deposit SnO2 & Bi2O3.
I'll report on it when I do it.
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dann2
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mogana100
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Hi
I have few questions about the SnO2 coating.
1. is it possible, or has anyone tried to use stainless steel as the substrate, as mentioned in the patent (for a chlorate cell, of course)?
2. @dann2: why did you use Sb as a dopant instead of Ce? CeO2-powder is aviable as high grade polishing paste for optics.
3. why refluxing the solution? are the chlorides reacting with the alcohol, or is it just for stirring (like when dissolving NaCl in water)?
[Edited on 9-2-2012 by mogana100]
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dann2
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Hello,
Some reading here:
http://www.oxidizing.110mb.com/chlorate/semi.html
I spent alot of time trying to obtain SnO2 coatings (doped with Sb) using SnCl2. The process is simple. You dissolve the SnCl2 + some Antimony
Chloride in alcohol, paint onto (clean and etched) Ti metal and bake in an oven to obtain the SnO2 (doped with Sb) coating.
I could never get it to work.
I had to use SnCl4:5H2O instead of the SnCl2 in the simple bake and paint process.
I seen the paper that describe the procedure whereby SnCl2 is refluxed with Alcohol (+ dopent, Ce is used in the article) and decided to try it with
Sb.
It worked fine. When SnCl2 is refluxed with alcohol a Tin Alkoxy (also called Tin Alcoholate) (spelling may be off) compound is formed which works
well to create coatings via the simple paint and bake process.
The only disadvantage with using SnCl4:5H2O is that it is difficult to obtain. SnCl2 can be made (or purchased) easily.
Tin Oxide Anodes, doped with Antimony, are not much use at making Chlorate or Perchlorate BTW.
Perhaps doped with Bismuth they may be good for Perchlorate. I don't know myself. I have never been able to make a Tin Oxide Anode doped with Bismuth.
I just end up with pieces of passivated Ti metal after I bake the Anode.
What are you ultimately trying to do with the Tin Oxide (doped with whatever) Anode?
I mainly use the Tin Oxide, doped with Antimony coatings as an coating between Lead Dioxide and Ti metal (ie. in a Lead Dioxide Anode). It is much
simpler to use MMO for this job (if you can get MMO).
Dann2
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mogana100
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Hi
I want to use it as an precoat between the substrate and a lead dioxide coating.
I want to use stainless steel, because here in Germany, Titanium is pretty damn expensive: a sheet of Ti, 10cm*10cm 3,2mm thick costs 104€ (104€
~= 140$ ). The price for an ingot of the same weight would be 2,8€ , ~= 4-5$.
This is the reason why I want to use a SS/CeO2:SnO2 anode as a kind of fault tolerant substrate instead of Titanium, because I can't get it cheaply.
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dann2
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Stainless steel will be hopeless IMO.
Grade 5 Ti will be much much much better if you cannot get Grade one or two.
http://www.ebay.de/itm/3-x-Titanblech-Titan-Blech-1-5-mm-3-7...
Try bicycle shops and they might give you some scrap from an expensive bike.
Dann2
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mogana100
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Thank you for the link.
But I don't understand why it shouln't work for making Chlorate, can you explain please? What is the chemical difference (at the anode of course)
between this application (making chlorates) and the original application (oxidizing organic compounds in aqueous solutions), and why is the stainless
steel not passivating like the titanium does? I'm just wondering because in both cases hydroxide ions are formed, so i can't see major differences.
(sorry for the noob-style questions, but I'm not experienced at this stuff, but I want to understand)
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dann2
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I don't know much about oxidizing organic compounds but a Chlorate or Perchlorate cell will rapidly corrode any Stainless Steel that is exposed.
Tin Oxide coating (or any Oxide coating) will not protect something that is going to corrode as these coating have 'cracked mud morphology'. They look
like cracked mud when viewed under a microscope. They do not 'seal' anything. You are depending on the nature of Valve metals (Ti, Nb, Ta) to form
their own very tough coating to protect themselves anywhere the Tin oxide (or Ru Oxide if MMO) coating is not alloyed to the metal or anywhere the Tin
Oxide coat wears away.
Read up on Valve metals. Stainless steel will not passivate in a Chlorate or Perchlorate cell.
Dann2
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