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Eclectic
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Look up thread and see that there is a procedure for dissolving the normally unreactive oxide you get from dissolving tin in nitric acid. It involves
digesting the oxide for some time in boiling SO2 solution before adding hydrochloric acid.
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12AX7
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| Quote: | Originally posted by woelen
The commercial SnO2 does not dissolve at all in any acid, no matter what concentration and what temperature. It simply is inert.
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Not even any reaction with HF? I would expect SnF6(2-) or something to exist.
If it's so inert, why don't they make SnO2 crucibles? Do they? :shock:
Tim
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alancj
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Thanks, guys. I ended up just buying some tin shot on eBay instead. Digesting SnO2 with SO2 sounds like a royal pain (though interesting)... as well
as fusing with a hydroxide. Considering that more round-about ways are just more likely to introduce unwanted impurities, I'm going with easier and
more direct methods. So, Tin metal it is!
-Alan
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woelen
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Be aware that the tin from eBay probably is VERY pure, something like 99.9+ % or better. This sounds good, but it actually isn't. Such pure metal
dissolves in HCl, but VERY VERY slowly. Dissolving a single granule of the shot (2 mm diameter or so) takes days at least in 25% HCl. When there is
some impurity in the metal, then it dissolves much faster. You could cast the shot to rods (or buy some rods off eBay, they are available frequently
very cheaply) and use these as anode in a HCl-electrolysis setup.
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alancj
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The stuff I bought was technical grade shot and is supposed to be 99.96% so I thought "well, kinda impure, but at 17 bucks for a pound and for my use
it's probably ok." I also bought 30g of antimony shot 99.999% for about the same $. I might treat my metal with Cl gas and go for anhydrous... or put
it in a flask and be patient, or do as you say and pass a current through it. Will pure antimony be as slow as Tin in HCL?
-Alan
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woelen
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IIRC antimony does not dissolve in HCl, you need an oxidizing acid like concentrated HNO3, or a concentrated mix of HCl and H2O2.
You are calling 99.96% impure  ?? Most chemicals you have will probably be less
than 99% and many of them probably less than 95%!
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alancj
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| Quote: | Originally posted by Eclectic
As long as the Sn:Sb ratio is near 90:10, it may not be that critical.
Dissolve your metals or oxides in concentrated HCL, mix, maybe add some HNO3 or H2O2 to bring up the oxidation state, evaporate to syrup, add alcohol,
paint, bake, and repeat.
(That's what I plan to try. Let me know if you get it working first.)
[Edited on 4-24-2007 by Eclectic] |
Would the HNO3 react (or for that matter, the HCL) with isopropyl alcohol? Also, does HNO3 just help form the chlorides but doesn’t create nitrates?
That is... if you were to evaporate the solution, would you get a mix of nitrates and chlorides or what?
Would electrolysis help the antimony get into solution of HCL without the use of HNO3? I have some, but my retort broke, and don't have much left to
go around.
Edit: HA! I managed to fix it. I welded a piece of broken flask over the hole in the bottom. It hasn't cracked yet, now that I've been distilling
water in it for a few hours.
-Alan
[Edited on 16-5-2007 by alancj]
[Edited on 16-5-2007 by alancj]
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not_important
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You'll want an excess of HCl. When starting with elemental Sb you'd cover it with an excess of concentrated hydrochloric acid, warm it, and slowly add
HNO3 until most or all of the Sb had dissolved - but don't overdo the HNO3 as you're just wasting the excess. Boil the solution briefly to finish
decomposing any excess of HNO3 and drive off Cl2 and NOCl. So long as there is an excess of HCl no nitrates are going to stay around.
H2O2 might work, but it should be fairly concentrated. Too dilute of H2O2 will result in the formation of oxychlorides and oxides, which will slow do
the reaction of the elemental Sb. If you do get white ppt, you'll have to add more HCl, possibly evaportating down the reaction mix first.
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Eclectic
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If you start with 95/5 solder, you can just dissolve it in concentrated HCl solution, maybe with a dash of H2O2 to prevent SbH3 formation. (OUTSIDE or
with good ventilation!) There was a paper referenced upthread that said highest conductivity is at ~5%Sb.
Too much HNO3 will make insoluble oxides.
[Edited on 5-17-2007 by Eclectic]
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alancj
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Isn't that just with 3-4% fluoride ion (?) You said that ammonium bifluoride is available as aluminum cleaner. Who might sell that do you think? I
have 500g of sodium fluoride; I don't suppose there is anyway to convert some into the ammonium salt without sodium contamination?
If anyone has access to the paper that Eclectic mentions, feel fee to post it 
Thanks
-Alan
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Eclectic
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I think that's 5%Sb with or without F-, but lower resistance if the F- is in there too.
Ammonium bifluoride is in aluminum wheel cleaners and refrigeration coil cleaners. I don't think it's really vital to the coat and bake process, but
could help to strip residual surface TiO2.
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Rosco Bodine
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conductivity data for doped tin oxides
This data is from a Corning patent US2564707 concerning conductive tin oxides baked on a glass substrate , such as might be used for heating elements
and other purposes . This patent was posted in another thread but the information is so pertinent also to this thread that I am attaching it here
where it will be more easily found .
Attachment: US2564707 Sb2O3 doped SnO2 and tertiary compositions.pdf (479kB)
This file has been downloaded 1216 times
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Rosco Bodine
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state of the art coating from 95/5
This is the most advanced reference which I have found
that is directly applicable to the mixed chlorides gotten from
95/5 .
A transparent , pore and crack free optical quality coating
having four to eight times the usual single baked coat thickness and superior conductivity and adhesion results from the use of polyvinyl alcohol as a
thickener .
US6777477
http://www.sciencemadness.org/talk/viewthread.php?action=att...
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dann2
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The best ratio
Hello,
Reading the patents that use Doped Tin oxide (With antimony) the perchantage of Sb used is variable.
Two patents that are doing what we want to do are
US 4040939 Example 1
US 4028215 Example 1
They use a ratio of SnCl4 to SbCl3 of 3.5.
This equated to a ratio of Sn to Sb in a starting alloy (assuming you are making your Chlorides from metals) of around 24% Sb the rest Tin. The solder
at 5% Sb is very far from that percentage.
I am currently making my own solder from Sb and Tin from EBAY.
The conductive coatings on glass patent(s) may not be directly applicable to putting the DTO on Ti. They use lower amounts of Sb.
Can I make SnCl4 by dissolving SnCl2 in HCl and adding H2O2?
Cheers,
Dann2
[Edited on 11-7-2007 by dann2]
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Rosco Bodine
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The baked coating technology of 30 years ago is very likely not better than the newer technology of 3 years ago for the same type of conductive
coating .
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Eclectic
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SnCl2+2HCl+H2O2-->SnCl4+2H2O
Of course it's a lot more complicated than that, but that is the net result. The reaction makes a lot of heat. Some of the H2O2 will be lost as H2O
and O2. Premixing 2 parts 10-12N HCl with one part 30% H2O2 can reduce the localized heating and spatter. (Don't try to keep the mix, and the
glassware must be very clean to avoid catalytic decomposition of the H2O2 and foam up)
A few drops of Ti dissolved in HCl can serve as an indicator of the endpoint. Blue until all the SnCl2 is converted, orange when there is an excess
of H2O2.
Unless you are planning a series of tests with different concentrations of Sb, I'm fairly confident that anywhere between 3 and 10% Sb in the final
coating solution will be "good enough", and in the same range as "best".
[Edited on 7-11-2007 by Eclectic]
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dann2
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| Quote: | Originally posted by Rosco Bodine
The baked coating technology of 30 years ago is very likely not better than the newer technology of 3 years ago for the same type of conductive
coating . |
Hello,
But they are on glass, not Ti. This may make a difference.
Don't know myself.
Dann2
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dann2
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| Quote: | Originally posted by Eclectic
SnCl2+2HCl+H2O2-->SnCl4+2H2O
Of course it's a lot more complicated than that, but that is the net result. The reaction makes a lot of heat. Some of the H2O2 will be lost as H2O
and O2. Premixing 2 parts 10-12N HCl with one part 30% H2O2 can reduce the localized heating and spatter. (Don't try to keep the mix, and the
glassware must be very clean to avoid catalytic decomposition of the H2O2 and foam up)
A few drops of Ti dissolved in HCl can serve as an indicator of the endpoint. Blue until all the SnCl2 is converted, orange when there is an excess
of H2O2.
Unless you are planning a series of tests with different concentrations of Sb, I'm fairly confident that anywhere between 3 and 10% Sb in the final
coating solution will be "good enough", and in the same range as "best".
[Edited on 7-11-2007 by Eclectic] |
Hello,
I added some of my 'Ti dissolved in HCl (blue)' indicator. It turned orange (or at least the blue colour went away) after fairly small addition of
H202. I am using 10 grams Tin. The H2O2 is 30%.
The 10 grams Tin dissolved in HCl was yellow to start with. I mean it was yellow after all the Tin had dissolved in the HCl.
I refluxed the HCl and Tin to get it to dissolve.
This yellow remained as far as I could see after the addition of H2O2. The orange of the Ti was hard to see along with the yellow colour of Tin in
HCl.
I need to start with alloy though.
Thanks for help.
What do you get if you feed Chlorine gas to Tin/Antimony Alloy. The Tin goes to SnCl4 (anhydrous). Will the Antimony go to SbCl3?
Dann2
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Eclectic
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My solder dissolved in hardware store muriatic acid was water white before adding any H2O2. Are you sure your acid is pure? No dissolved Fe? Mine
was a very pure grade also used to adjust swimming pool pH.
Cl2 should react directly with the dry alloy to make SnCl4 and SbCl3, but then you have to get it hydrated. You could also bubble Cl2 into the alloy
dissolved in HCl solution, but I see no advantage over using HCl/H2O2, and much greater hazard.
[Edited on 7-11-2007 by Eclectic]
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Rosco Bodine
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| Quote: | Originally posted by dann2
| Quote: | Originally posted by Rosco Bodine
The baked coating technology of 30 years ago is very likely not better than the newer technology of 3 years ago for the same type of conductive
coating . |
Hello,
But they are on glass, not Ti. This may make a difference.
Don't know myself.
Dann2 |
Technically , the interface is SiO2 for glass (or silicon) and TiO2 for the titanium , which shouldn't be any problem . There is a similar diffusion
layer that will be there in either case , and a better solution of the dopant will increase the adhesion and increase the conductivity for either
interface .
Whatever produces a more homogeneous solution of the
antimony oxide in the tin oxide will benefit the interface ,
and the solution of the antimony dopant is increased in
the fusion product of precursors derived from the ammonium salts , as compared with the solubility of the antimony oxide
in the fusion product of precursors that are the chlorides .
Think of it as epoxy part A and part B , the better the two
are mixed and dispersed .....the more complete will be the
reaction .....no matter what materials are being glued together by the mixture .
It shouldn't make any difference because of the mechanism for the way these coatings work .....they are solid solutions ,
essentially a tin oxide based glass in which is dissolved the
antimony oxide . When the antimony content gets very large like the proportions you are referencing , not all of the
antimony dopant is dissolved in the tin oxide , but exists as a separate distinct phase which disrupts the continuous glass with pores and cracks and
islands of particles of undissolved antimony oxide which makes the coating full of bumps and ridges , not as adherent nor strong , and certainly not
as electrically conductive nor chemically resistant as a smooth and even layer of homogeneous glass .
The antimony oxide is the thing that dissolves in the tin oxide
and it is highly unlikely that increasing the amount of the thing difficult to be dissolved and decreasing its potential for being dissolved can be
better for the integrity of the end resulting coating .
The substrate is vulnerable to undesired oxidation during the baking , so whatever melts soonest and most completely to a coating that seals it
.....is going to be better than something which requires numerous coats to fill in all the
cracks and pores of the coatings which preceded .
So my bet is that the optical grade coatings that form a perfect coating in one bake from the first coat are going to
perform better .....no matter what the substrate .
If anything , the TiO2 layer will be more porous and thicker
than the SiO2 layer , and a more fluid , better dispersed fusion coating is more likely to be soaked into the TiO2 to produce a good diffusion layer
....as it will more easily wet that porous surface , than will a less dispersed coating .
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dann2
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| Quote: | Originally posted by Eclectic
My solder dissolved in hardware store muriatic acid was water white before adding any H2O2. Are you sure your acid is pure? No dissolved Fe? Mine
was a very pure grade also used to adjust swimming pool pH.
Cl2 should react directly with the dry alloy to make SnCl4 and SbCl3, but then you have to get it hydrated. You could also bubble Cl2 into the alloy
dissolved in HCl solution, but I see no advantage over using HCl/H2O2, and much greater hazard.
[Edited on 7-11-2007 by Eclectic] |
Hello,
My HCl is lab grade (Analar, same as AR I think)
The Tin is 'very pure' from ebay. It was purchased from the element collector people.
The Ti oxide(s) indicator will not turn back to blue (from orange) when you add SnCl2 into the Tin dissolved in HCl + H2O2. When you add some more
indicator (blue) it will remain blue as the H2O2 has been knocked out by the added SnCl2.
What I am trying to say is: the indicator seems to only go from blue to orange when all SnCl2 is converted by H2O2. If you then add SnCl2 (solid) the
solution will go back to having no H2O2 but the indicator will not indicate this. You have to add fresh indicator(blue) which remains blue. Add more
H2O2 and it will go orange...........
The SnCl2 (solid) I have is ebay stuff sold as Tin Mortant. I presume it is hydrated as I added some to HCl and it did not fume or warm just dissolved
(as suggested by Eclectic).
The HCl I am using is 35% AR grade.
Dann2
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Eclectic
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That's good to know about the Ti indicator. I was thinking the SnCl2 would reduce TiCl4 (colorless) and the Ti peroxide complex (bright orange-red)
back to TiCl3 (intense blue). Still it seems usable in this application to determine when enough H2O2 has been added. With the SbCl3 also in
solution, there is a color change to bright yellow-green when enough H2O2 is added, also the brown-black precipitate dissolves .
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Rosco Bodine
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The agony and the ecstacy of conductive enamelware
To ammoniate or not to ammoniate ?
*That* is the question 
[Edited on 11-7-2007 by Rosco Bodine]
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Eclectic
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Nah. It's just reducing effect of SnCl2, easy to cure with H2O2.
I don't think ammonium chloride is going to have much of a fluxing effect in this system compared to all the other stuff, especially before it
evaporates at baking temps.
[Edited on 7-11-2007 by Eclectic]
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Rosco Bodine
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One thing I like about the idea of a cobalt spinel over a glass clear type of intermediate over a titanium substrate .....the color could possibly be
very striking ,
and even a thin layer would probably look ten feet deep ,
something like a sapphire , jewel like finish instead of
a dull black . A pretty anode is certain to be superior Many of the spinels
are likely to be highly colored materials having that gem like flashy effect you might see on fancy custom auto paint jobs .
Anyway , I was thinking about the ammonium stannate and ammonium antimonate precursors absent chloride .
[Edited on 11-7-2007 by Rosco Bodine]
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