| Pages:
1
..
12
13
14
15
16
..
48 |
Swede
Hazard to Others
Posts: 491
Registered: 4-9-2008
Member Is Offline
Mood: No Mood
|
|
dann2 - I couldn't download that patent for some reason - what was the date on it? My hopes for this particular MMO mesh is that it was engineered
from the beginning to be exceptionally durable. I'm hoping that patent (stripping MMO) deals with early coating processes that aren't as tenacious.
The anode I attempted to make perc with looks to be 100% intact. There were no black flakes in the electrolyte, no discoloration of the coating.
Tentacles - first, nice job on the adapter. Your fittings look professional, and the adapter plates themselves look stout and effective. How did you
manage to slot that thick PVC sheet for the electrodes? I'm guessing you used a bandsaw and simply sealed up the excess slot with PVC cement.
The fact that you are smelling O3 or something similar is a good sign. I took some careful whiffs when my MMO-only perc cell was operating, and there
was NOTHING, no smells at all.
The current that you are seeing is about what I would have expected, and is in line with my own very limited experience. To get 30 or 40 amps in my
previous perc cell required about 7.5V. My electrode spacing is similar to yours, a bit more than 1/2". I think the only way to get them closer with
any safety is to machine or adapt some inert plastic spacer brackets that hold the edges of the electrodes. But if they are brought too closely
together, I think there will be problems with crystal growth within the electrode set.
How heavy are your cables to your cell? If not heavy enough, you are going to lose significant voltage in the lines. 14 gauge cables will drop about
half a volt before the juice ever gets to the electrodes. Use a DVM and measure the voltage at the supply, then at the electrode shanks, and you'll
see some difference.
Power supplies are easily set up in series, and even dissimilar supplies tolerate this fairly well. it is only in parallel that you require a more
complicated setup. If you have 2X 5V supplies with adjustment pots, you might consider placing them in series and turning them to 4V each. Just a
thought.
RB - on that alumina slurry, I read the patent and it is intriguing. Is that material commercially available? I'd like to give it a try.
[Edited on 24-11-2008 by Swede]
|
|
|
tentacles
Hazard to Others
Posts: 191
Registered: 11-11-2007
Member Is Offline
Mood: No Mood
|
|
I used some 4 gauge wire I've been carrying around for about 2000 miles through various moves.. It's all red but I've got like 20 feet of the stuff. I
may just run the PS's in series, but I will need to figure out WTF with the 5.5v/200A supply. It's probably something stupid I overlooked in the
manual, or the voltage is simply cranked too high.
I may just remake the bucket lid adaptor.. and space the cathodes like 3/8 or even 1/4" from the anode, although that will require bending and or
welding.
Current came back up to 13.8A overnight, probably just the electrolyte is warmer. I may wrap some paper or bubble wrap around the bucket if I can find
some.
edit: Fixed the 5v power supply and cranked it up to 8v / 30A, decided to take a peek at the anode.. Quite a lot of the PbO2 had flaked off - it
looked worse than it was in the cell, I decided to pull things apart and inspect it more closely..
The MMO coating looks a bit unhappy in a couple places, but nothing major. Some of the PbO2 is quite adherent, I think I'll remove what I can and try
plating alpha PbO2 with the alkaline bath and then plating beta with the standard acid bath. If I knew where my methylene blue was, I'd test for
perchlorate. I'll look for it in a little while.
The cathodes are hydriding at a remarkable rate, considering the current. They are already starting that flexing BS. Swede, did you switch to CP
cathodes in the T cell? Or are those alloy as before? Maybe all I need is to constrain them at the bottom as you did.
[Edited on 24-11-2008 by tentacles]
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
Hello,
The patent that mentions Bi for Perchlorate is US 4272354 dated 9 June 1981 from DeNora et al (Diamond Shamrock Technologies).
It's not much use to us IMO. They also suggest that half the metals in the Periodic table are useful as an ingredient in the coatings.
The bending cathodes must be related to the fact that they are not pure Ti (they have Al in them).
Is your cell at a very high temperature like Swede's was?
The coating of LD, as you know is very thin. It may not be very wise to judge the LD (Beta anyways) on MMO with such a thin coating.
Dann2
|
|
|
tentacles
Hazard to Others
Posts: 191
Registered: 11-11-2007
Member Is Offline
Mood: No Mood
|
|
dann: Agreed, I'm going to plate it proper this next time, using a tartrate bath like you successfully used on your LD over DTO anode, and plating a
much heavier layer of PbO2 over that. I might even plate it on in layers, alternating alpha and beta to alleviate stress per the various patents.
Any suggestions as to layer thickness?
[Edited on 24-11-2008 by tentacles]
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Ceria as a perchlorate catalyst
Does anybody use ceria in anodes for perchlorate manufacture?
All the discussion of anode materials got me wondering about rare earths. Just a bit of digging led me to consider ceria = cerium (IV) oxide,
CeO<sub>2</sub>. There are a number of interesting things about it.It's an ionic conductor of oxygen. Atoms of
oxygen can move through the lattice, although it's probably sequential displacement.
Doping (with Gd or Sa) improves its ionic conductivity.
It has a stable sesquioxide, cerium (III) oxide, which means that it can be reduced without becoming ionic and entering the electrolyte.
Most cerium oxide compositions are really not stoichiometric.
There are lots and lots of stable crystal phases, which means good mechanical stability against perturbation in operating parameters and oxygen
content.
It's readily available in graded particle sizes for use as an abrasive.
It's refractory, which enables ceramic construction techniques. The thing that's struck me is with all the different ways that ceria
interacts with oxygen that it's a good candidate for an oxygen donor to take chlorate to perchlorate.
Suppose that a chlorate ion strikes a planar electrode surface in a random orientation and sticks. In will stick in one of two geometric
configurations: one with (A) three oxygen atoms touching and another with (B) two oxygen and the single chlorine. Assuming the probability of sticking
is independent of orientation (it's certainly not, but go with this approximation) and assuming central-tetrahedral bond angles for chlorate (another
approximation), the ratio of A:B is 1:3. In configuration (A), the new oxygen can come from the electrolyte. In configuration (B), the new oxygen has
to come from the surface, adsorbing and then sliding sideways. It's pretty clear that the reaction rate for configuration (B) is much, much slower
than for (A). Thus the population of chlorate ions adsorbed on the anode surface is going to be dominated by configuration (B). Enter the oxygen
mobility in ceria. If the oxygen to react can come from within the anode surface, even being donated from the anode material, the reaction rate in
configuration (B) should be much higher.
I'm not set up to try this. Steal this idea.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
That follows somewhat my own idea that the materials which form peracids like vanadium, manganese and chromium would be good candidates. However
there would by necessity be required some sort of oxygen impermeable barrier layer interposed between the outer coating of anodes bearing such
materials in order to prevent the ionic oxygen from tunneling straight to the substrate and passivating it. That is the function for which bismuth
doped tin oxide excels, and similarly niobium doping of the Ti substrate interface can also function as an oxygen barrier. Bismuth can serve a dual
purpose because it not only is an effective oxygen permeation barrier in DTO, but it also raises the oxygen overvoltage to a value above the potential
required for the oxidation of chlorate to perchlorate, so that perchlorate is preferentially produced. Bismuth in small percentage added to MnO2 and
also to PbO2 , and probably to other metal oxides as well, should raise the oxygen overvoltage in that manner. This is not reported in only one
patent, but is mentioned in several. Even for
anodes where platinum group metals or oxides are used, the durability of such anodes is increased several times by using Bismuth as a component.
Experiments were begun by a couple of people here, I think Xenoid was going to look at this in combination with the baked MnO2 coating,
and tentacles was looking at the Bi doping of SnO2 , but whatever was found I don't recall. Any updates on those experiments ?
@ dann2
If bismuth has been decided not to be useful, then what is the basis for that opinion, since it contradicts what has been reported in several patents
?
|
|
|
Swede
Hazard to Others
Posts: 491
Registered: 4-9-2008
Member Is Offline
Mood: No Mood
|
|
Tentacles - The warped cathodes were a Ti alloy. The cathodes that did NOT warp were CP. Very interesting, I never made that connection. I stopped
accumulating Ti alloy sheet mainly because I did not care for how it cut and drilled... it is very tough stuff. CP is much softer and easier to work.
The PTFE bar clamps were there just in case, and were not needed. I'm 98% convinced that the alloying elements in sheet such as 6Al-4V are the
culprit in cathodic warping.
Another observation - the warped cathodes have returned to their normal position in the days since the cell was halted, without any intervention at
all.
Your #4 cable is obviously heavy enough. Sorry to hear that the plating failed. Rather than reinvent a wheel that doesn't work, I look forward to
any thoughts on a more successful plating process.
I am very interested in the alumina (boehmite) slurry process mentioned earlier. Some informative links:
http://www.catalysts.basf.com/main/process/adsorbents/alumin...
http://www.chemicals-technology.com/contractors/catalysts/al...
Now, to get my hands on some of this stuff!
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by Rosco Bodine
That follows somewhat my own idea that the materials which form peracids like vanadium, manganese and chromium would be good candidates.
|
What got me thinking about rare earths was the 4f screening of valence electrons. What got me hooked was
oxygen ion conduction. I forgot to mention that ceria is also used in SOFC = Solid Oxide Fuel Cells, which is an area where the material used share
two important requirements: resistance to oxidizing environments and conductivity. YSZ = Yttrium-Stabilized Zirconia is a common material here.
Importantly, ceria has a flourite-shaped crystal structure at room temperature, which YSZ does not—it transitions to that structure at a
higher temperature. There are also perovskite materials used.
Conductivity for both at aqueous temperatures is still pretty high, but the difference with perchlorate is that you don't need a mechanically strong
membrane. A thin layer deposited on a solid substrate is sufficient.
| Quote: | | However there would by necessity be required some sort of oxygen impermeable barrier layer interposed between the outer coating of anodes bearing such
materials in order to prevent the ionic oxygen from tunneling straight to the substrate and passivating it. |
That's certainly right. If the ionic conduction is high enough, it seems to me that corrosion, not merely passivation, is the risk.
On the other hand, if this oxygen-impermeable layer is strong enough, is there still a need to use a titanium substrate? It would seem that copper,
much more flexible, would work better for mechanical stability. Or perhaps better, a steel mechanical substrate with a plated copper layer.
| Quote: | | That is the function for which bismuth doped tin oxide excels, and similarly niobium doping of the Ti substrate interface can also function as an
oxygen barrier. Bismuth can serve a dual purpose because it not only is an effective oxygen permeation barrier in DTO, but it also raises the oxygen
overvoltage to a value above the potential required for the oxidation of chlorate to perchlorate, so that perchlorate is preferentially produced.
|
Ceria doping creates an "oxygen semiconductor", which has oxygen vacancies in the lattice structure. (It's
because the dopants are in oxidation state III rather than IV.) It's occurred to me that if the ceria is adequately doped, oxygen production at the
anode isn't as problematic, since a free oxygen atom can immediately diffuse into the ceria matrix rather than combining with another oxygen and
escaping as a gas. Having said that, the trick is going to be to match oxygen oxidation at the anode with the combination rate of conductive oxygen
and chlorate ion. Bismuth, with a complete 4f shell and a compatible ion radius, is a good candidate for a dopant toward that goal.
|
|
|
tentacles
Hazard to Others
Posts: 191
Registered: 11-11-2007
Member Is Offline
Mood: No Mood
|
|
Rosco: Bi doped tin oxide I believe to require tin (iv) nitrate, or some other +iv decomposable tin salt. edit: +IV decomposable tin salt compatible
with a soluble decomposable bismuth salt.
Doping a lead nitrate bath sounds feasable.. What sort of percentage do you think I should shoot for? Couple-ten grams/l to ~300g/l Pb(NO3)2?
[Edited on 25-11-2008 by tentacles]
|
|
|
Xenoid
National Hazard
Posts: 775
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline
Mood: Comfortably Numb
|
|
| Quote: | Originally posted by Rosco Bodine
Experiments were begun by a couple of people here, I think Xenoid was going to look at this in combination with the baked MnO2 coating,
and tentacles was looking at the Bi doping of SnO2 , but whatever was found I don't recall. Any updates on those experiments ?
|
@ Rosco
My final effort was outlined in the Multilayer Oxide Anode thread on page 9;
http://www.sciencemadness.org/talk/viewthread.php?tid=9783&a...
It is headed "Total Failure" I spent 1.5 days putting 88 baked layers on Ti, it only lasted a few hours in a perchlorate cell. It was the final
product from the Anode Division of the Xenoid Chlorate - Perchlorate Corporation. Xenoid now procures his anodes by out-sourcing. 
@ tentacles
I too have wondered about adding, say 5% bismuth nitrate to a PbO2 plating bath. I was going to ask Rosco what he thinks would happen during the
plating procedure. Bismuth is closer to Cu than Pb on the electrochemical scale so perhaps it "plates out" on the cathode and none would end up with
the PbO2 on the anode. Or perhaps minor amounts are adsorbed as either Bi or Bi2O3 onto the PbO2 anode.
Any ideas on what mechanisms would be operating in this situation - Rosco?
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Xenoid you gave up too soon ...prosperity is just around the corner , tomorrow might have been a better day
There was more to look at there, if you investigate the possiblities in the same way as you first checked out the cobalt spinel and the cobalt
manganese combination.
The reduction of bismuth to metal is very odd, and the rapid passivation seems odd also. You shouldn't need 88 coats to find out if you are on the
right track. Maybe you did something different at the start which botched everything that followed subsequently. I've been too busy to go back and
review or test what I was suggesting but I think it was on the right track.
There's been patents posted on the electroplating of Bi2O3 simultaneously with PbO2, with details on how the concentration of the Bi in the plating
bath corresponds with the analysis of the coplated material. IIRC there
is about ten times the amount percentagewise of the Bi2O3 which co-deposits as is its relative concentration in the plating bath.
|
|
|
Swede
Hazard to Others
Posts: 491
Registered: 4-9-2008
Member Is Offline
Mood: No Mood
|
|
Slightly OT - surfactants. I spent the whole morning going bat-s**t trying to find a source for nonionic polyoxyethylene surfactants that might be
helpful in plating. I think I found one: Triton X-100:
http://www.2spi.com/catalog/supp/triton-x-100-concentrate.sh...
Another option is Tween 20 or even Kodak's Photo-flo. Locating a surfactant that is not highly processed for molecular biology (hence big $$) is not
a simple matter
|
|
|
tentacles
Hazard to Others
Posts: 191
Registered: 11-11-2007
Member Is Offline
Mood: No Mood
|
|
I wonder if my local photo shop has the kodak product. I might go check tommorow if my wife doesn't take the car... Forming a "perfect" coat of LD
wouldn't hurt anything.
Rosco: Do you have a link to that patent? I'd be interested in reading it to see if there's any information on the percentages of Bi in solution to
produce a suitably doped PbO2. Otherwise I might just put in 5-10g of Bi2O3 into the acidic plating bath (and allow it to dissolve as Bi(NO3)3).
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
Hello,
@ Tentacles.
I would be inclined to keep coating the mesh untill all the holes disappeared and then some more. (have not practiced what I preach, but my thin
coating (1.5mm) lasted three months and is still good for more)
There is a picture of an Anode of Ti + SnO2 + LD below from this board.
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
The anode measures 5 by 30 cm. Quite large.
You can see the traces of the holes that were in the Ti. It will take quite a lot of LD to do that, ie. a large tank or replenishment of Lead ion or
better, large tank and replenishment.
With Patent US US 4272354 (posted 24/11/08) when I said 'it was no good for us', it was in relation to the anode construction method (it involves
plasma spraying).
A patent that adds Bismuth to the LD plating tank is US 1038170 (Attached).
It states (line 25) that it may be advantageous to only add the Bismuth to the surface layer dept so that you get a best bond with the substrate (No
Bismuth at interface).
The Bismuth if for decreasing wear rate, not increasing cathylitic activity AFAICS.
My own 2 cents worth would be just make a plain Beta Lead Dioxide (perhaps with Alpha at interface) and test that for a few months. If it proves good
then start tweeking the plating with (half) the elements in the Periodic table.
Another LD + Bismuth patents is US 4101390 (same as above)
US 4353790 is a Bi Oxide anode for Oxygen making only, they don't mention Chlorate or Perchlorate or anything like them.
I don't know of any more patents that add Bi to LD.
From postes by JPSmith, Diamond is said to be good for Chlorate (thats Boron doped diamond).
I wonder would ordinary diamond powder have an ability for making Chlorate or Perchlorate.
It is easy to add to LD. Just put diamond powder in the LD plating tank and stirr. The dust will get incorporated into the plating (as happened with
my Al Oxide grit that I had in taplating tank).
@Swede CTAB is touted to be a good surfactant. Relieves stress too. I would suggest to forget about surfactants. Use glass beads or similar and
stirring. It will not complicate matters with breakdown products etc.
If you want to spend money there is nothing better than investing in a large plating tank for LD, IMHO.
Some propaganda for addtives in LD plating tanks is included below for your (not) enjoyment.
+++++++++++++++++++++++++++++++++++++++++
The surfactant will not allow a bubble to stick to the anode and therefor you get an improved coating of Lead Dioxide. There is also a mention of the
surfactant Cetyl Trimethylammonium Bromide alleviating stress in the electro deposited Lead Dioxide in JES Sept. 1976 p1294 (see elsewhere on this
page) but that is the only place that surfactants are claimed to reduce stress in the dioxide.
An alternative strategy for the elimination of bubbles is to spin (cylinder) or rock to and fro (flat plat) the substrate which keeps bubbles from
sticking to the anode. The movement has also the added advantage of keeping the bath stirred.
Adding ceramic particles to the bath has been mentioned in patents 4,026,786 and 4,159,231. The bath is stirred and the particles brush against the
plating anode and keep bubbles swept off it. This method has no complications like breakdown products etc.
There are other additives that are mentioned in the literature including
Nitric acid!, limited to 4 to 6 grams per liter, US 1038170
Nickle Nitrate,as a grain refiner
Gelatin, as a deposit leveller
Fluoride, to improve plating current efficiency, reduce bubbles on anode and for to dope the Lead Dioxide. Na Fluoride has an approx. saturation value
of 4.5 x 10 ^-2 M, at which point Lead Fluoride precipitates. (JOURNAL OF APPLIED ELECTROCHEMISTRY 10 (1980) 511-525)
Iron, Cobalt, Nickle and F to increase catalytic effect, (J.Serb.Chem.Soc. 66(11–12)835–845(2001))
Flourine resin, (Environ. Sci. Technol. 2005, 39, 363-370)
Hydrogen Peroxide, to oxidise Nitrites, that are formed at the cathode, back to Nitrates (US 2994649).
NaClO3, ???
Sodium/Lead Acetate to relieve stress and as a pH buffer (Electrochimica Acta. 1971. Vol. 16, pp. 1301 to 1310).
Ta & Nb Oxide powder to reduce stress (US 5545306 & 4822459).
Teflon emulsion to reduce stress.
Bismuth Nitrate to make the anode much more resistant to wear (US 4038170 & 4101390).
Bismuth has also been touted as having increased cathylitic effect for the formation of Perchlorate.
CTAB to decrease stress (JOURNAL OF APPLIED ELECTROCHEMISTRY 12 (1982) 171-183) though they say that high temperature and low CD do a better job that
the CTAB
and more.....
Surfactants will improve the coating of the Lead Dioxide but it is not essential to get an excellent coating of Lead Dioxide when using an inert
substrate or inert fibre mesh reinforcement as theses materials have resistance to the Chlorate/Perchlorate electrolyte.
The addition of surfactant has the added complication of the break down products produced by the surfactant in the plating bath which will eventually
stop the bath from plating successfully. Some have suggested resting the neutralised bath for 24 hours for to allow the breakdown products to
recombine. After a lot of plating the tank has to be washed using amyl alcohol, which is a lot of extra work. See US Patent No. 2,945,791.
+++++++++++++++++++++++++++++++++++++
Dann2
[Edited on 25-11-2008 by dann2]
Attachment: US4038170.pdf (529kB)
This file has been downloaded 735 times
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Plasma spraying was not the only method described for bismuth doping of SnO2 and numerous patents have been posted by concerning this and it has
absolutely zero to do with "half the elements of the periodic table" .....
but very specifically to do with bismuth. I am pretty sure there was one of those patents which used a dip and bake scheme for Bi doped SnO2 which
was specifically stated to be useful as a *perchlorate* anode. Indeed it is the same patent where the plasma spraying is described as an alternative
method, US4272354 . Column 1 line 60 basically says that Bi doped SnO2 makes a perchlorate anode.
Seems simple enough to me.
The bismuth related stuff with regards to PbO2 was I think posted back in the PbO2 thread, and the bismuth doping with regards to MnO2 and SnO2 was I
think posted already in the MMO thread...but we have sort of overlapped discussions so I'll have to go back through it to find the specific patent
numbers.
Anyway I think I had arrived at a proposed composition
based on a survey of the various references and tentacles
seemed interested but burned up a heat gun or something and never did anything else with it.
@dann2 you have a good oven IIRC, so how come you haven't tried doing something on it ? Think of bismuth as the antimony that works .....maybe. You don't have to worry about some large assortment of combinations
that are possibles as candidates for experiments as there aren't but a few which seem likely and bismuth is one of them. You have to keep a positive
outlook when it comes to anodes .....they are very sensitive to "negative waves"
[Edited on 25-11-2008 by Rosco Bodine]
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
Diamond Electrodes
Dann2 with regard to diamond, there is a patent application (attached) for the use of doped diamond electrodes for making perchlorates.
I think one day doped diamond will make Pt and PbO2 obsolete but it may be a while before that happens.
From my reading, it seems that CVD methods result in higher quality DLC films than electrolytic methods, but CVD methods are slower, more complicated,
more expensive, and not easily scaled-up.
Apparently the choice of substrate and/or interface layer is very important, and as I understand it, an unexpected and so far unexplained
adhesion/wear failure mode of DLC films in aqueous environments has been discovered.
I've often thought that, for us, a diamond anode could be made by electrophoretic deposition of diamond powder, or maybe by way of a paint-and-bake
slurry using TiH2 or something, but I can't find anybody selling any kind of conductive diamond powder.
Attachment: 2007_0170070A1.pdf (612kB)
This file has been downloaded 738 times
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Bismuth doped tin oxide has been reported to make a perchlorate anode......so what are you guys saying exactly, that it must be a typographical error
or something ?
|
|
|
Swede
Hazard to Others
Posts: 491
Registered: 4-9-2008
Member Is Offline
Mood: No Mood
|
|
Rosco Bodine, I have a computer-controlled furnace capable of excellent control up to 1200 C; I would love to try some sort of baking or sintering
process. The death of most anodes seems to lie in the poor adherance of the active coating, and often a baking process, high heat, seems to do the
trick.
My skills lie in fabrication more than chemistry, but given a basic process, I think I can replicate it. Does anyone have a link or more information
on the Bi doped tin oxide process? I'll dig through the MMO thread to see if I can find it. There's SO much information here, it's hard to keep
track of it all.
Diamond dust - I am assuming the doping occurs during the creation of the industrial diamond dust, so unless someone has their own home setup for
creating industrial diamonds, I think we are hosed there.
One process that might be adaptable to this process is plain old powder coating. Those who have worked with powder coat paint know that once it is
baked and cured, it is incredibly tough stuff, requiring abrasive blasting to remove. The "paint" is a powder... how about adulterating the paint
with appropriate conductive oxides? My guess is it would not work due to the resistance of the coating, but with a sufficient percentage of
conductive oxides in the powder, over a substrate like Cu, it might work. The baked coating is quite thick and should protect the underlying
substrate VERY well.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by Swede
Does anyone have a link or more information on the Bi doped tin oxide process? |
I don't specifically, but I
can mention that indium-doped tin oxide is widely used as a transparent resistive heating element on glass. The fabrication processes, I have to
imagine, share a lot in common.
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
| Quote: |
Diamond dust - I am assuming the doping occurs during the creation of the industrial diamond dust, so unless someone has their own home setup for
creating industrial diamonds, I think we are hosed there.
|
If the prospective anode is to be made by electrophoretic depostion of diamond dust onto a substrate, then, yes, I believe we would need boron-doped
diamond dust, which I have been unable to find as a commercial commodity.
If the anode is made by electrolytic deposition of a DLC on an appropriate substrate, then we would need to add a boron compound to the electrolyte
(according to published results this has been accomplished with NaBH4, and boric acid may also work).
If the anode is made by RF plasma CVD, methanol + water + methyl borate (and maybe boric acid) can be used as feedstock.
BTW attached is a paper on electrochemical synthesis of DLC films.
Attachment: Electrolytic Diamond.pdf (728kB)
This file has been downloaded 852 times
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
| Quote: | Originally posted by Swede
Rosco Bodine, I have a computer-controlled furnace capable of excellent control up to 1200 C; I would love to try some sort of baking or sintering
process. The death of most anodes seems to lie in the poor adherance of the active coating, and often a baking process, high heat, seems to do the
trick. |
There have been identified in separate places in different threads, most or all of the subtleties of conditions which should be considered, the
technical considerations are pretty well identified but as a random scattering of discussion or isolated posts in different threads. I am tooling for
the experiments I would like to do, but nearly all of my time and money is being drained on other priorities so my pursuit is crippled by that
indefinitely. What would be six months of happy tinkering could end up waiting six years......so don't anyone wait on me. I put my energy into
fetching the data,
and got plenty of good data, if only dann2 will cease ridiculing it as if it was meaningless somehow. Good experiments are not being considered, not
because of technical merit considerations, but because of incorrect ideas which are driven by bias.....the idea that some simultaneous
etching of Ti substrates during an interface producing pyrolysis is somehow essential, has been a seemingly insurmountable myth to dispel.
| Quote: |
My skills lie in fabrication more than chemistry, but given a basic process, I think I can replicate it. Does anyone have a link or more information
on the Bi doped tin oxide process? I'll dig through the MMO thread to see if I can find it. There's SO much information here, it's hard to keep
track of it all. |
That's the rub for me too, I'll have to research my own research at this point to gauge the breadth of what has gone uninvestigated. And I can't do
that now. There have been at least four different doping schemes for bismuth doping of SnO2 already posted by me, which are dip and bake
straightforward methods ...probably more like five or six different schemes, so it is pick one and go for it. And
with regards to the adhesion, well the benefit of hydriding the subtrate is one which is probably certain for some interface schemes, but not
necessarily for all of them.
That fibrous alumina is the latest thing I have found and the Pytlewski polymers may have similar structure although the matter was never elucidated.
Cobalt doping would possibly be of interest there with the fibrous alumina, because of the spinel cobalt aluminate, as well as the Ti interface. And
a bismuth doping example for SnO2 is included in the Pytlewski polymer patent. I have posted a hell of a lot of good references and the dots are
there to be connected.
Another adhesion possibility was oxidative cold soak deposition onto a hydrided Ti substrate, followed by a
dip into the dopant before baking to develop. There are
definitely experiments galore which could be made from the
information presented, but it seems that instead, a proven recipe is being sought ....something already published in completeness ABC, 123, when there
may not be one, and if there is it may not be anywhere near state of the art as
might be discovered by experiments involving some of these other methods.
dann2 seems hell bent on reading into as well as reading out information by his own inference, what is or is not stated explicitly in any reference or
patent and it is unscientific to do research wearing blinders ....it is frustrating for me trying to come to terms with people who won't accept yes
for an answer 
Anyway, my time does not allow me the luxury of argument.
So for whatever I have been able to contribute, take it for what is worth and do with it what may be done or whatever you will, as this whole thing
has become circular. And I really do have other fish to fry right now, and most of the rest of the time, being involved in two separate huge lawsuits
simultaneously which were problems visited on me
by some real a**holes who are trying to rob me and destroy me, and are losing badly in that endeavor but just won't give it up. I'll keep checking
in, but I really can't work on this now.
[Edited on 26-11-2008 by Rosco Bodine]
|
|
|
Swede
Hazard to Others
Posts: 491
Registered: 4-9-2008
Member Is Offline
Mood: No Mood
|
|
I totally understand the time required, and the distractions you face. I will simply start going back in the various threads and also looking through
patents, but patent search to me has always been a bit of a headache, mainly because there is no proof that a particular patent actually works. But
there are certainly some good nuggets to be found in many of them.
I always appreciate the info gleaned from posts by just about everyone.
The boehmite fibrous substrate patent shows promise to me. The problem is obtaining the boehmite itself. There is a process that apparently can
produce fibers of good length and geometry from more commonly available precursers. That may be the way to go. One of them involves aluminum
propoxide:
http://www.nano-biology.net/showabstract.php?pmid=16851437
A coating that would ferociously adhere to a conductive substrate, limit oxygen travel, and carry just about any catalytic components imaginable,
would be a valuable tool.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Really though what I said about the Pytlewski polymer is important and it contains the bismuth dopant in the polymer which very well may be a
stannous analogue of sorts to the fibrous alumina. If so it could basically kill two birds with one stone, adhesion and doping ....you see? The Bi
variant Pytlewski polymer could function as if it was the fibrous alumina carrying a separate catalyst ....but in the case of the Pytlewski polymer
the catalyst would actually be an included part of the polymer fiber. This is theoretical however as I have no idea if the polymer remains intact
after pyrolysis or if it disintegrates to a purely amorphous structure ...it could go either way or some intermediate transformation. But this would
be one of those unknowns worth looking at to see what does happen. US3890429 example 11 is the bismuth containing polymer. There was another bismuth
doped SnO2 derived from ammonium stannate ammonium bismuthate US6777477 example 2. And there was an oxalate derivative route, and several others in
other patents I can dig up later.
Basically where there is a will there is a way. The nitrates of tin are real but there's been arguing on that too just because they can be tricky to
make, but it's been done for at least a couple of hundred hundred years by dyers.
If you are going onto a hydrided substrate , the Schottky layer is going to be a few molecules thick ..no etching (during pyrolysis) required. IIRC it
is a reverse breakdown voltage junction there, Schottky junction in Zener operation, and added thickness only makes the conductivity worse. Co spinel
or Co/Ni binary spinel or Co/Zn binary spinel ahould do fine there...possibly even a Co/V binary spinel ( that one is my hypothesis) may be good to go
with even one coat. There's your conductive interface and all the rest of added DTO thickness is simply an oxygen barrier for more substantial
anti-passivation armoring , and/or the catalytic working layer beyond that . In the case of bismuth doping of SnO2 the intermediate layer and working
layer are one in the same, if the Diamond Shamrock patent US4272354 is right. And there is another patent which indicates that a MnO2 baked layer
with Bi in small percentage produces a perchlorate anode, if you have to go on out to a third working layer. Or at last chance you could come over the
outside with plated PbO2.
[Edited on 26-11-2008 by Rosco Bodine]
|
|
|
Swede
Hazard to Others
Posts: 491
Registered: 4-9-2008
Member Is Offline
Mood: No Mood
|
|
From a practical viewpoint, a durable LD coating over a substrate that will not passivate is all that is needed to make a good perchlorate anode.
I've got half a dozen 2" X 3" MMO sections cut out. Each of them is going to be plated with LD, in an attempt to find a plating process that produces
a durable and functional coating.
At least one of them I am considering periodic polarity reversal by the simple expedient of a DPDT relay on a timer, or some other mechanism.
Picked up two varieties of polyoxyethylene non-ionic surfactants, Triton X-100, and Tween 20, with the Triton being the longer-chained of the two.
Another, easy and cheap option would be Kodak's Photo-flo, which can be found in most good camera shops that sell chemicals and such for B&W
photography.
I am going to gather chemicals for some of the more "exotic" methods, but only if a reasonably simple means of LD plating simply cannot be achieved
over MMO. I've abused this stuff (the MMO) horribly on two occasions, and it has held together well. I think it'll be a good substrate. All we need
to do now is create a LD plating method that works, and is repeatable.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
A couple of references have turned up saying that fibrous alumina is the form of the oxide which grows at a visible rate from the surface of
amalgamated aluminum exposed to the air, and the fibrous form is made stable by heating the material. There is a book on alumina which I have
requested through references, wanted books by members, which describes this and other methods and use of alumina in ceramics.
The surfactant which is used as a wetting agent and sold
in garden shops as a spray additive called a spreader-sticker is a polyoxyethylene non-ionic surfactant and it
probably could be used also, if a surfactant is needed.
It would be my choice to try the patent described low iron impurity plating schemes which require no surfactant being used, since a surfactant is
going to become a contaminant after it is oxidized and its byproducts accumulate.
[Edited on 28-11-2008 by Rosco Bodine]
|
|
|
| Pages:
1
..
12
13
14
15
16
..
48 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
