387 replies to this topic

[Anders Greenman]

I'm also working. My Pb(NO3)2 will soon be dried and I can begin my second attempt.

[hashashan]

Why do you dry your lead nitrate? do you have a death wish? or you just want to suffer all youyr life ... fluffy lead salt powders are EVIL.

keep it moist or in solution.

[hashashan]

Well guys I think I have an update.
Recently I was working on a massive anode.
The anode was grown from a piece of Ti through a thick (about 4mm) piece of plastic fiber cloth(aka scotchbright). The setup had controlled temperature of 50-58(sometimes it went higher.... I wasn't around to babysit it, corrected it as soon as I could) at the begining it even had PH controll (some PbO that I dumped inside and a magnetic stirrer) but later I ran out of PbO so added NaOH solution from time to time to keep the acid down. Also I added some ceramic dust and shreads as dann2 wrote, It seems like it helped, almost no bubble pitting at all.
I ran about 1 amp(30-40 ma/cm) current for 3 days and today my setup caught flame, probably because of the heating system that was just a thermosensor and a heating element in a plastic bath with water(I guess the it ran out of water and inflaminated). So I had to take the anode out, however the anode was already nearly complete, it is about 5mm thick in the center and really overgrown on the sides(I tried to prevent it by building a hot melt glue farame for it to grow inside but it overgrew it on the first day, so on the sides its about 1cm thick.
It peeled quite easily from the Ti strip.

The anode is big, about 3.5cm*10cm and it weighs 175gr.
Ill post some pictures today when Ill get back home from work.

[tentacles]

I have a tidbit to add - I've been following and reading up on PbO2 anodes for quite some time now, and I made a test anode the other day as a sort of proof of concept.

I used a furnace filter cloth as the substrate for my anode - it's from the pleated type of filter so the material is quite similar to scotch brite, but denser and thinner. I took a piece of titanium wire and ran it through the cloth to serve as electrical connection while plating. I sprayed on a solution of acetone + NC (ping pong ball type) and pasted on powdered PbO2. It worked quite well, after drying the electrical conductivity was fairly good, with most of the well pasted regions being no more than 5k ohms. I would like to add that I only pasted in a 4cm wide strip on this substrate - I had two small vials of PbO2 and used only one, not knowing if this method would work.

I plated it out at 5ma/cm2 for about 18 hours, and took it out to weigh and examine it - I had forgotten that the process shouldn't be interrupted! I continued plating after reimmersing it at about 10ma/cm2 for another 24 hours.

Despite the interrupted plating, the second layer does not seem to have poor adhesion to the first.

I continued my experiments, silver plating it using the process on the geocities site (actually I read the referenced patent). The plating was successful and I subsequently plated on copper.

Here's a picture of the anode (quite ugly). I cut off the part of the anode that I did not originally plate with PbO2 (wasn't submerged in the plating bath). That is the end that I plated with silver then copper. The splotchy look is because it is still damp after rinsing it.



The silver plating bath I used was:

Part A:
300ml water (tap)
3.0g Ag(NO3)2
10 drops NH4OH (household ~7%)

Part B:
.2g Ag(NO3)2
.166g Rochelle salt (I actually used .2g)
100ml water (tap)

The part A solution is very simple - mix and then filter. The ammonia is added until the PH reaches 10, but I didn't accurately measure this at all. It worked despite my carelessness.
Part B is prepared by dissolving the Ag(NO3)2 in 10ml water and then adding the remaining 90ml as boiling water, then add the Rochelle salt. Boil for 20 minutes and then combine the two in the plating tank. Technically by the patent's proportions I should have used only 58.6ml of my part B solution but it doesn't seem to have hurt anything that I used more.

The patent says to plate at 2.5A but having not researched deeply, I just fed it some current - about 450mA until the solution turned from reddish brown to mostly clear. I got some black scum at the cathode (which is the PbO2 being plated), most likely from using sterling silver as the plating anode. I only plated it with the silver once, while the patent reccomends doing this several times for a thicker plating - I felt that since my area to plate is very small, this should be sufficient.

The plated on copper can be soldered to - this might seem obvious, but I was not sure if the lead dioxide would decompose at the temperature required.

Despite having said I wasn't going to try this anode in a cell, I may just try it anyways for the hell of it.

Edited by tentacles, 12 November 2007 - 12:39 AM.

[marble]

That thing looks ugly as sin

Let us know if it works

[Anders Greenman]

Why do you dry your lead nitrate? do you have a death wish? or you just want to suffer all youyr life ... fluffy lead salt powders are EVIL.

keep it moist or in solution.

So I can weigh it and have some kind of idea on how much nitrate is in the solution. I could have calculated using mole, but it tend to be too inaccurate.
Thanks for the tip though! I will be very careful.

[hashashan]

Why do you need to know how much is in solution. I use the most saturated solution I can get.
Just take your solution and put it in the sun and wait for the first crystals to appear, then add some water and you good for go

[Anders Greenman]

Okay, will do. You saved me a lot of trouble there

[tentacles]

Here's something interesting - "glassy" carbon. I wonder if it would make a good substrate for a LDA? It seems to be pricey but that could just be this source.

http://cgi.ebay.com/...3QQcmdZViewItem

[marble]

phew

Thats expensive for such a small piece, would be interesting to see how it holds up.

Im thinking about trying to make a anode out of manganese dioxide powder mixed with conductive epoxy glue

[tentacles]

marble, I put my anode in a test cell yesterday and the NC bound PbO2 started eroding immediately; your mileage may vary with an epoxy binder (the trick is probably in getting the perfect percentage). The plated on layer is holding up very well so far; I was running it at 5.5A until around noon today and changed the power supply with something beefier; it's now at 11A. The water is all brown from the PbO2 powder.

For cathodes I'm using 8 coils of .028" Ti wire (it's what I've got). Total about 18 feet of it. There's some Ti sheet on the way for when I make a more permanent cell, but this seems to be working okay. The Ti heats up where I've connected it to a Cu wire, but I doubt there's anything I can do about that.

Edited by tentacles, 18 November 2007 - 05:59 AM.

[marble]

I saw the pictures, im Warezwally on APC. I imagine the Ti would act like a heating coil similar to a kettle

[marble]

Google just found me a holy grail, a photographic supplier who sells stuff for developing photos.

Among many thing i purchased:

500ml conc nitric acid
100g lead nitrate

anode here I come

[tentacles]

Marble, try and get some PbO as well, you can dump it in your PbO2 plating tank to control PH and provide more lead ion to plate out. Try ceramics shops and mining/assay suppliers.



Things I've noticed regarding perchlorate manufacture, various stuff here..

If you're using copper cathodes, don't bother with Cu(NO3)2 - the copper anodes supply the same function without the hassle.

The lowest current density I've seen in a patent for PbO2 is 100ma/cm^2 - their efficiency rate was similar to the other tests in the patent. It was a patent for using NaF in a chloride to perchlorate cell. (in other words, there may not be a minimum current density to generate perchlorate)

It is possible that plating PbO2 at a lower current gives a smoother plating - I have no reference for this, only my own minimal experience.

Also, for those who haven't seen it, there was a reference on science madness to a substitute for sufactants in PbO2 plating:
"Ceramic particles are preferably incorporated in the electrolyte solution because these particles, when suspended in the electrolyte as by constant agitation, prevent oxygen bubbles from clinging to the substrate anode during the electrolysis and consequently eliminate the formation of holes in the lead dioxide deposit. Typical ceramic particles are minus 325 mesh ceramic beads and, when employed, are used in a typical concentration range of 1 to 10 grams per liter. "

I plan on trying some "silica flint" from my local pottery shop; it's listed as 325 mesh SiO2.

The shop I've ordered some nitric acid from (40L of 30%) sells greenhouse and lawn care supplies; I may see if they have some surfactant and try a combo of surfactant and silica.

Edited by tentacles, 18 November 2007 - 05:49 PM.

[marble]

Damn, they wont ship the acids and I wont be in the area for at least a few months.

Is the nitric acid used to lower the ph vital?