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chemkid
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with some effort i am sure i could get my toaster oven up to 300 C, but at that point a small foudry or furnace might be nice instead.
Chemkid
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jpsmith123
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Making it go from 250 to 500 C sounds more like "redesign" than "modification"  .
Anyway, what I'd like to do is find a large sized rectangular "microwave kiln", but the only ones I've ever seen are rather small cylindrical ones.
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Rosco Bodine
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Lead melts at 327C . I wonder if you couldn't just lay
your coated Ti in a trough of melted lead where it would float like a cork and bake in the bath . If the lead didn't
react with the oxide , this might be an easy way of getting a good even heating .
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dann2
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Hello,
or would a alloy of Sn and Sb melted at 500C cause an oxide coat (a doped one) to form on freshly etched Ti that was dunked into it.
A pipe dream perhaps.
Dann2
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12AX7
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I doubt it. Possibly you might have some luck if you got a fluoride-based titanium flux and tinned the base metal with that alloy, then annealed in
air.
Tim
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Rosco Bodine
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A few helpful references to follow
Effect of addition of lead acetate during the deposition of lead dioxide from the nitrate bath
Attachment: Effect of addition of lead acetate during the deposition of lead dioxide from the nitrate bath.pdf (657kB)
This file has been downloaded 1447 times
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Rosco Bodine
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The fabrication of lead dioxide layers on a titanium substrate
Attachment: The fabrication of lead dioxide layers on a titanium substrate.pdf (1.7MB)
This file has been downloaded 2690 times
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Rosco Bodine
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Oxygen overpotential of graphite-substrate lead dioxide anode
Attachment: Oxygen overpotential of graphite-substrate lead dioxide anode.pdf (183kB)
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Rosco Bodine
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Lead dioxide coating obtained by pulsed current technique
Attachment: Lead dioxide coating obtained by pulsed current technique.pdf (501kB)
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chloric1
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| Quote: | Originally posted by Rosco Bodine
Effect of addition of lead acetate during the deposition of lead dioxide from the nitrate bath |
Thank you ofr all these wonderfull references Rosco!! I sincerely appreciate it. I especially took notice about the acetate addition to lead dioxide
plating bath as a pH buffer. This seems analgous to jpsmiths post about plating cobalt metal from cobalt sulfate and cobalt acetate. He stated that
the sulfate yeilded crappy deposits while the acetate yielded smooth shiny ones. After reading this I was thumbing through cobalt chemistry in my
Merk index and noticed they said a dilute solution of cobalt acetate had a pH of 6. I thought to myself this is pretty high for a semicovalent
metallic salt. My understanding is that most nickel and cobalt salts of strong acids had pH's of like 4 or 5 in dilute solution. With this thinking
I came to this conclusion that wild pH flunctuations caused stressed out crap electrodeposits.
Not only do I want to try a lead acetate addition to the nitrate bath but I would also like to use cobalt acetate on titanium hydride to plate cobalt
metal prior to baking spinels.
Fellow molecular manipulator
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Rosco Bodine
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Yeah that article supports an idea that I had expressed earlier in the thread when observing an overlap in the
optimal pH ranges for the conditions for plating alpha PbO2 from an acetate bath and the conditions for plating the beta PbO2 from a nitrate bath . I
supposed
( informally hypothesized ) that by varying the voltage using a mixed acetate - nitrate electrolyte , a mixture of alpha and beta PbO2 might result ,
giving a stress free deposit in thick layers .
IIRC , I didn't really think then about the possibly useful fringe benefit of the acetate acting as a buffer , as of course it is recognized now that
it may solve that headache of pH regulation needed for quality platings , simply to use a mixed acetate - nitrate plating bath for that reason alone ,
avoiding the misery of pump circulation
of the electrolyte through neutralizers .
This would probably work pretty well also for the
MnO2 plating scheme which uses MnCl2 to advantage
over the sulfate , using an acetate as a buffer .
The limiting factor with this method is that it is a
spin coating . All of the stationary samples showed pinholes . So that's a complication which may rule out
this particular method from consideration . It may be that a surfactant or nickel nitrate or NaF additive could improve the results for the stationary
plating , along with the current pulse deposition scheme .
I think probably the bismuth containing PbO2 or one of the other patent processes would probably give satisfactory results . But this mixed acetate -
nitrate scheme could be an area for experimentation .
[Edited on 22-12-2007 by Rosco Bodine]
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chloric1
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| Quote: | Originally posted by Rosco Bodine
The limiting factor with this method is that it is a
spin coating . All of the stationary samples showed pinholes . So that's a complication which may rule out
this particular method from consideration . [Edited on 22-12-2007 by Rosco Bodine] |
Rosco, I don't understand this. The article gives specific rpm speeds and only an appropriate drill in a drill press setup with sliding anode
contact possibly made of brass.
Fellow molecular manipulator
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Rosco Bodine
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| Quote: | Originally posted by chloric1
| Quote: | Originally posted by Rosco Bodine
The limiting factor with this method is that it is a
spin coating . All of the stationary samples showed pinholes . So that's a complication which may rule out
this particular method from consideration . [Edited on 22-12-2007 by Rosco Bodine] |
Rosco, I don't understand this. The article gives specific rpm speeds and only an appropriate drill in a drill press setup with sliding anode
contact possibly made of brass. |
You are right it's not a problem if you are using a cylindrical
form anode  Maybe a vibrator of some sort would do
better for a plate form anode . Really that's what I was
thinking about using anyway . I think vibration , might
keep the bubbles shaken loose for the stationary anode .
This is one of the uncertainties which would have to be addressed by experiment if a plate substrate is used .
Actually I favor a solid rod form anode since it is the most
convenient for many reasons .
[Edited on 22-12-2007 by Rosco Bodine]
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chloric1
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Well, I have read more often than not that rods are usually the recommended shapes and I have seen where plates need to have there edges rounded. I
just won about 20 1/4" Ti6Al4V rods on ebay for $45! I will now be able to
expand and play with more baked on interface ideas. Also, I will be able to easily make a profit reselling most of what I bought back on ebay.
Fellow molecular manipulator
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Rosco Bodine
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The 1/2" CP grade is probably best all round candidate but the other alloys may work okay too .
A common diameter for patent test examples is 1/2" and that up to maybe 3/4" is good for a solid substrate anode . IIRC the larger you go thereafter
runs the risk of differences in the thermal expansions causing stress fractures in the coatings for solid cores ,
and a hollow tube , or perhaps a perforated sheet is
then needed .
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dann2
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Hello Folks,
I enclose some correspondence I have had with RongPeng regarding [DTO (alone) and DTO with LD on top]
anode making. He had made many DTO (alone) + LD anodes(LD on top of DTO, Ti substrate).
He has not made any Chlorate or Perchlorate with andoes as he uses an accelerated electrochemical test
for to test them, Electrolyzing H2SO4 .
I wonder how relevent to (Per)Chlorate making the accelerated test is?
Our Chlorate cells have high pH. The pH of Perchlorate cells seems to be all over the place
+ the added complication of the different species thrown in for good measure!
Dann2
Attachment: rp for SciMad.txt (18kB)
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tentacles
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Has anyone tried plating PbO2 on a valve metal other than Ti? Specifically Nb and Ta, as mentioned in several patents, are supposed to make good
adhering, long lasting anode cores. I have been wondering if anyone has tried? I know Ta and Nb can be pricey, but so can things like SnCl4 et al.
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Xenoid
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@ tentacles
If people are having problems with Ti, I don't think trying to use even more expensive and exotic metals is going to help. The same problems will
apply, perhaps even more so.
I would like to see someone with PbO2 plating facilities and chemicals, try plating over a Co3O4 baked on interface layer. The Co3O4 layers are
extremely easy to put on Ti and it costs virtually nothing to do. Two layers would be enough!
If someone doesn't do this soon, I will try it myself .... 
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dann2
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Hello,
| Quote: | Originally posted by tentacles
Has anyone tried plating PbO2 on a valve metal other than Ti? Specifically Nb and Ta, as mentioned in several patents, are supposed to make good
adhering, long lasting anode cores. I have been wondering if anyone has tried? I know Ta and Nb can be pricey, but so can things like SnCl4 et al.
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Same problems apply. Seen a Ta substrate anode but it was a massive anode. Substrate was ignored when it went into service.
I tried putting DTO on Tungsten but did not succeed. I used SnCl4:5H20 + other bits (had success using Ti with same solution).
About to wheel out the lead plating tank..........
Dann2
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tentacles
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I've been plating another anode, this time using (almost) hashashan's method. Here's a chop of my post from (APC)
"I kicked my ass into gear today and am trying another plating session. I sanded the Ti strip with P220 sandpaper, and then used my dremel to round
the edges nicely, wet sanded (EtOH) with 1000 grit SiC paper, and then painted the side that I hope to not plate with some cheap black spray paint. I
covered the edges with hot melt glue, making sure to heat the Ti up so it would stick, and also covered the painted side with more hot melt glue. I
then sanded the working side again with 1000 grit paper, then tacked on the scotch brite.
I prepared 2L of solution as my bath:
250g/l of Pb(NO3)2
1.65g/l of NaF
15g/l of Cu(NO3)2
2.2g/l of 50/50 200/325 mesh SiO2
10ml/l of 80% HNO3
I'm running it at 52C on my hotplate, with the stir bar running.
Current density is 15ma/cm2, running off 3.3v on my new (and cheap) ATX PSU. PbO2 started plating immediately when I turned on the power.
edit: Came home last night and it was pulling 845ma, which was a bit high for my liking - I know it's in the acceptable plating current range, but I
bumped the voltage down to 1.7V (5.0v - 3.3v). It's pulling ~5ma/cm2. Plating continues."
Today:
"Anyways I decided to stop plating this anode, weird things were starting to happen.. I peeled it off the Ti, which wasn't so much peeling as breaking
off a few little bits to release it.. It actually curved while plating, which is very strange. After I got it off, it was somewhat broken, so I
lassoed it with some wire and dunked it in to plate it back together.. The result.. 168.7g of very ugly PbO2. I doped the plating solution with NaF,
the resulting PbO2 is smooth, and shimmers."
http://www.apcforum.net/files/DSCN6808.JPG
http://www.apcforum.net/files/DSCN6803.JPG
http://www.apcforum.net/files/DSCN6800.JPG
http://www.apcforum.net/files/DSCN6798.JPG
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hashashan
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Way to go .. looks just like my own but a bit smaller.
Seems like my method is good 
however the Pb nitrate seems quite low 250 g/l ... i used more then 500
[Edited on 4-1-2008 by hashashan]
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tentacles
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I need to make more, but I'm out of calcium nitrate.
hashashan: Did your anodes end up curling like mine did? Interestingly, the curved sections didn't crack, I wonder if they are from the compression
stress, or if they are from the NaF doping. I can't wait to get home and silver/copper plate this thing, and pump chunky amps into it.
[Edited on 4-1-2008 by tentacles]
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hashashan
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My Ti plate was very strong so there was no bending ... but the bending issue is known
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chloric1
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So you guy are using titanium as a substrate to form the massive lead dioxide? I think the bending is from stresses from not ashering to the
passivated titanium and the dropping pH of you plating bath. Try baking a cobalt spinel anoded and plating that with PbO2. Also, you are plating at
WAY too high current density.
Fellow molecular manipulator
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tentacles
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chloric: the current for the *whole anode* was 845ma - it actually topped at about 1100ma at one point, but that's for a 14x2cm area. 39ma/cm2 is
maybe a bit high for my liking but most patents suggest going as high as 50ma/cm2.
hashashan: The Ti plate didn't bend, it was only the lead dioxide. The plate is actually 1mm thick 6-2-2-2 Ti, so it's pretty stiff. I looked at the
bits I broke off to remove it from the Ti, and there are probably pinholes - I'll take a super closeup with the camera later. The plating is very
smooth, the nodule shapes that always seem to form are largeish, and the shimmering effect is quite striking.
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