Thoughts On Anodes

With regard to bubble elimination during plating.

When I finally get around to experimenting with LDO plating, I intend to vibrate the anode rather than rotate it. The anode is mounted at the end of a semi-flexible plastic strip (perspex - 20cm x 2cm x 4mm) along with a small motor with an offset weight on the shaft.

The motor is quite good quality, from an old VCR and appears to be nominally 6V but operates from about 3 - 9 volts. By connecting to a variable power supply you can vary the "buzzzzzz" on the anode. I may need to put a slightly heavier weight on the shaft when the anode is immersed in liquid but otherwise it should do the trick to prevent bubble build up.

Please, no vibrator jokes -

Before Xenoid suggested vibrating an anode during plating, I was already 90% done with a deluxe rotational rig. Given all the work that went into this, I'll probably give it a try. I still have to set up a good plating tank using sheet Cu cathodes.

The hard part about a rotating setup is good, solid, continuous electrical contact with the rotating shaft. I decided to use 3/8" (~ 10mm) hard Cu tubing, and an extruded aluminum column. I thought about making a springy Cu finger to press against the shaft, but then decided to do it properly, with a carbon brush.

I milled a brush holder out of aluminum, slotting the rear to hold the circular spring cap:



The extruded aluminum is good stuff, because it is T-slotted, and allows the repositioning of the motor head to various locations on the vertical upright, which is affixed to a piece of plywood. The motor is enormous and total overkill, but it is the best one that I had. I took two surplus timing sheaves and mounted them on the gearmotor and Cu shaft...





The small brush assembly is inverted and mounted on the horizontal boom arm:



The continuity checks well with an ohmmeter. All that remains is to slot the end of the Cu rod and mount that to the anode strap, and set up a good plating bath.

Hello,

The (gruesome) details of the Ti/SnO2/LD anode runs are here:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

The CE for going from (Na) Chloride all the way to Perchlorate was 17%. That's not too bad as they only get 55-62%% CE from the industrial manufacturing facility that was doing the same thing. They would have of course used pH control, I did not.
I think that back when the folks in Navada where making Perchlorate from Chloride, they were getting electricity for half nothing from the Hydro dam owners that were begging people to take some power off there hands.
Sometimes I wonder have we latched onto the (lazy) idea of going from Chloride to Perchlorate, without any intermediate processing, too much.
See here for original by Upuda and folks.
http://www.geocities.com/lllwolly/further/jes1976.html
+
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

Note that they add NaF in order to raise the overpotential for Oxygen evolution at the (LD) Anode. (stop it happening)
I has wrongly thought it was to stop reduction at the cathodes?, o dear.

The efficiency of by (Pure) Na Perchlorate cell was not too hot. It varied from day to day. See link at top. Bear in mind I was 'more testing the anode than making Perchlorate'.
Perhaps pH control would have helped? I did use additive.

Going all the way to low concentration of starting material (let it be Chloride when making Chlorate or Chlorate when making Perk.) is always going to be a low CE business when compared to industry who are not going to do it unless they can get power for half nothing.

The anode should be made with a much thicker coating of LD on it but that's another story.

@ Swede. The coating setup is looking more and more impressive.
YOU WILL NOT BE GETTING ANY PICTURES OF MY COATING SETUP + BENCE BACKGROUND!!!

Anyways I am in the process of setting up a cell using poor-mans-MMO* that I intend to pH control to see what erosion will be like.

Dann2

*Graphite

Nice spinning jig. A floor standing drill press with a flange
bearing on the rotating vise table would work too, passing
the shaft through the table to a second chuck below.
When you do the actual plating are you going to use a coaxial arrangement of tubular cathode of some sort?

One of the advantages I believe is likely for the coaxial electrode assembly, having a pumped electrolyte, which I have mentioned, is that by changing the electrolyte composition to a lead nitrate-bismuth nitrate plating bath, the anode can be plated in situ, and then the tubing and pump and reservoir emptied and rinsed, refilled with the brine used for the oxysalt production. If the inlet and outlet holes for the electrolyte flow were angled and surrounded by chambers like hollow collars at each outside end portion of the cathode tubular housing, a cyclonic flow of the electrolyte would possibly achieve the same effect across the surface of the anode during plating, as would spinning the anode in a static or stirred plating bath. Also I am thinking there may be enough intermixing of hydrogen and chlorine in the
electrolyte exiting the electrode assembly during electrolysis of brine, that a turbulent flow in a transparent glass coiled tube like a graham condenser , illuminated by a halogen lamp, may reconstitute the HCl needed to hold the electrolyte pH relatively stable. So there are a couple of more possible advantages to a coaxial cell arrangement.
Another of course is the localized heating would keep the electrode clear of crystallization , which would occur in the
cooling solution in its receiving tank from which the electrolyte is returned by the magdrive circulator pump
back to the coaxial anode assembly , in a continuous loop. Supplementing the electrolyte with fresh feedstock
materials, testing and adjusting pH if needed, and regulating temperature, as well as harvesting crystallized
product from the process would be easier using a pumped electrolyte and a coaxial electrode assembly. This could run continuously at an optimum operating point as opposed to a batch process which runs a lot of the time
at an inefficient range of concentration for the electrolyte
and other less than optimum parameters. For convenience
in carting away the product you could just use a poly wheel barrow as the reservoir and cooling tank, having a pair of wheelbarrows side by side so that when one is full you simply switch over to the other so that the process remains
uninterrupted.

The coaxial arrangement would also allow for use of tubular titanium for both the anode and cathode and the orientation
could be reversed possibly to advantage using the inside
of the outer tube as the anode , since this is agreeable in
shape and form for the plating of PbO2 moreso than any other shape, due to the natural deposition properties of the PbO2 it tends to form the most dense and durable deposit
when plated onto the inside of a tubular form anode. This is the form used industrially for producing massive PbO2 anodes which are later stripped by being sawn in curved slats something like the curved pieces in a venetian blind,
by lengthwise sawing of the substrate into segments, and then etching away the *iron* substrate . But the same idea
should work just fine on a DTO or possibly a spinel coated
Ti substrate, the DTO being preferable IMO, with some Bi doping there also.

[Edited on 21-11-2008 by Rosco Bodine]

RB, I like the way you think! Taking industrial processes and scaling them down. The thought of plating the inside of a tubular form with LD is an interesting one. Given a tube of say 50mm ID, give that a nice LD coating, install a coaxial cathode of 25mm OD. Apply a very high current density, and by varying the flow, you just might be able to create a "1-pass" system, meaning the electrolyte passes through (probably vertically) once, and given the high current density, the effluent is depleted of chloride or chlorate.

The used effluent exits and flows to a cooling chamber, where the crystals settle in the case of potassium. 50 to 100 amps, and a flow rate calculated to deplete the starting species with one pass through the system.

One way to set such a system up would be to have the tubular electrodes in a cannister, like a water-filter container.

Watson.fawkes - I thought of trying to weigh the anodes. My best scale has a 0.01g resolution. With a larger anode, it might work, but I wish I had a milligram scale or balance.

Plating tank: I'd like to find a durable container of 2 to 4 liter capacity, with an effective lid, that will both store and be able to heat, and plate, LD. Glass can be set on a lab heater, but glass is expensive. Plastic requires an immersion heater. I'll probably end up using a 2 or 4 liter beaker for now, and just storing the toxic liquor in a nalgene or similar HDPE container.

We've discussed rotating anode plating already, but I did have a thought... If I can find a section of copper tube of sufficient diameter, by cutting it into two sections, I can create the proper shape of two hemispheres. If not, I'll just bend some sheet copper.

If rotation fails, I'll try vibration or simply stir the electrolyte.

All: There is a guy on ebay that's selling items of interest, including lead nitrate ($10 for 500 grams!) and Bismuth metal. His store is Chem-Wise Chemical Solutions. He also has NaF but the shipping is lethal.

US3506561 Fibrous Alumina Conductive Catalyst Carrier

Here's one which I don't believe has been posted before although I did post the patent for fibrous alumina sol preparation in the old cobalt oxide anode thread, I think with
regards to using this as a "modifier oxide" or perhaps in regards to making a cobalt aluminate hybrid spinel of some sort.....I don't remember exactly. Anyway this fibrous alumina hydrate is another inorganic polymer which forms as microscopic whiskers having a thixotropic effect and forming a sol-gel system, which on drying leaves a tightly adherent
felt of randomly oriented fibers, which dehydrate on baking
to a chemically resistant, conductive, enamel like coating,
which is however porous and can entrap particles of other
catalyst oxides or finely divided metals like palladium black,
platinum or lead oxide, formed in situ from thermodecomposible precursor salts which have been mixed into the fibrous alumina hydrate sol. This sol seems very similar to the Pytlewski polymers based on tin oxide ,
in that it acts as a wetting agent even to teflon and is even capable of bonding teflon to metals. But for our interest it would seem that it's possible usefulness is for making a PbO2 baked anode. See column 6 line 47 of the patent.
Supposedly this works on different substrate materials like graphite, or steel, or perhaps aluminum, and titanium may not be strictly necessary as a substrate. The fibrous alumina
has been patented for use as a photographic plate coating process material for aluminum plates, where the deposited
fibrous alumina has a matte appearance after bonding to
the indigenous shiny oxide film of polished aluminum, and
provides a porous hard film which can then bond the photgraphic gel coat emulsion. So this fibrous alumina may solve adhesion problems in baked anode schemes, as a bonding layer for the substrate or as an inert matrix for carrying catalysts. I think with certain dopants, on baking it probably also forms aluminate spinels at least partially.
Inorganic polymers hmmmm, the stuff even sticks to teflon .....now that's some superduper super glue
See US4500444 column 2 line 14 referencing the bonding capabilities.

[Edited on 23-11-2008 by Rosco Bodine]

Attachment: US3506561 fibrous alumina electrode coating.pdf (202kB)
This file has been downloaded 795 times

Ceria as a perchlorate catalyst

@ 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?

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.

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]

Diamond Electrodes

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]

US3039849 Amalgam Derived Fibrous Alumina

Amalgamated Aluminum at ordinary conditions

commercial availability

The fibrous alumina is commercially available since it is used as thickener for lubricants, cosmetics, ect. as well as being used in papermaking, water purification, ceramic materials and assorted other uses.

http://www.sasoltechdata.com/alumina_group.asp

There is no technical difficulty in making the material as a sol by various schemes which involve hydrothermal decomposition under autoclave conditions of solutions of various unstable hydrolyzable aluminum salts. Simply heating a solution of aluminum nitrate at 50 psi autogenous pressure for several hours results in a sol of fibrous alumina. The patent US2915475 describes many different precursor solutions and hydrolysis conditions.

Anyway, *all* of this "fibrous alumina" discussion seems to point back favorably to the Pytlewski polymers based upon tin, which are formed more easily under less extreme conditons of hydrolysis, and should result in a conductive material after pyrolysis. There has not been any followup on this which can be cited for reference, but the described properties of the sols gotten by Pytlewski are similar in many ways to the properties of sols of fibrous alumina, and it seems highly probable to be a similar nanowhisker material that is produced there by Pytlewski. IIRC there are several of the hydrous metal oxides which will polymerize under various extremes of conditions, and hydrogen peroxide has been used as a catalyst to facilitate some of these polymerizations. In the making of some of the stannic chloride precursor solutions which have been experiments by forum members, where H2O2 has been used to oxidize Sn II+ to Sn IV+ , there have been reported observations of "syrupy" liquid products and these are very probably the result of stannic oxide polymers having some fibrous structure of the colloidal SnO2 which is present to enough extent to have a thixotropic effect for the sol. The thickening effect would be pronounced even for the presence of the fibrous colloid at extremely small percentages of the total weight of the liquid, only hundredths to tenths of a percent would be needed to completely gel the liquid....so it doesn't take much fibrous colloid to produce the desired thickening. All of these aqueous precursor mixtures which are prone to hydrolysis are also likely under certain "notch conditions" of pH and temperature to undergo polymerization to some extent resulting in the formation of sols and the particles would be expected to be fibrous ....for *all* of them

Perhaps I am going a long way around the block here, using the better documented description of "fibrous alumina" and its implications for MMO anode coatings, to try to make folks understand why I was pointing out the significance of Professor van Leent's anomalously "soluble" stannic oxide gotten from dissolution of tin in nitric acid when in the presence of iron, chromium AND *aluminum* ( hehehe there's that metal !!! ) and say Hey Folks !! , do you maybe see the analogy, the nexus here ??? Do you see why old Rosco is turning somersaults about this "sol" stuff which van Leent was writing about a hundred years ago, and later Pytlewski was decribing as "polymers" ??????? These things are all related to our "fibrous alumina" ....they are all cousins in the same family of materials in terms of their physical chemistry. And van Leent and Pytlewski are absolutely both relevant to these MMO precursor schemes, if not as the precursor itself , then at the very least as "modifier oxides"
and thickening, viscosity modification of the precursor liquids used in the coating schemes. And van Leent's aluminum stannate or stannous aluminate sol should be especially intriguing, if you can connect the dots here. It is very likely fibrous and very likely conductive and requires no autoclave conditions to produce.

Here is another possible supplier
http://www.wesbond.com/colloidal_alumina.htm
and another
http://www.nyacol.com/information.htm

I have wondered if fibrous alumina or colloidal silica (cab-o-sil) is the thickener used in 20% HCl toilet bowl cleaner. It is probably one or the other. Little else could withstand the acidity.

Yeah the materials chemistry, the physical chemistry on the "closeup view" of this stuff is amazing, it is the ultimate kind of nano scale scaffolding, open framework
sponge-like material. And it is within this structure where
the chemical reactions occur that transforms and gives birth to all the little ions of chlorate or perchlorate that
we are wanting to be happening. On the surface visibly it may look like a sheet of glasslike ceramic, while it actually will be a labrynth cellular matrix where the current flows, with a whole lot of ion traffic descending as one thing and jumping back out as something else But don't get tunnel vision for boehmite, it is simply an example that is better described, and the other materials are similar. Even MnO2 can do these structural tricks, and SnO2 certainly can also. Understanding what is actually going on with these materials is not any waste of time when an effort is being made to improve the integrity of baked MMO coatings. Commercial manufacturers who make the MMO anodes which are near indestructable have covered this same ground. These mixed ceramic coating materials are a specialized scientific art to themselves.

The anodization / cathodization strategy for anchoring an interface coating into a columnar welled mesa of TiO2 is something which was brought up in discussion in one of these threads before, and yes it has an analogous use in color anodizing of aluminum, whereas our purpose would be focused on conductivity and coating adherence rather than colorfastness, but indeed the technology there may be adaptable. This fibrous alumina would add a subsequent layer of horizontally oriented fiber structure
to the vertically oriented structures gotten by anodization.

[Edited on 30-11-2008 by Rosco Bodine]

Well, I went a bit wild and bought enough stuff to create a really deluxe plating rig... plenty of lead nitrate, bismuth salts, litharge, a polypropylene tank of sufficient capacity, and an immersion heater + temp controller. A bit of NaF and nickel nitrate too to play with, if needed.

The tank, heater, and controller will also see use with anodizing and other processes requiring a good, stable heat source.

Maybe my "sample" of boehmite will arrive today! More likely, it got kicked out of the system because it wasn't an order from MIT, 3M, the U.S. military, or some other gigantic corporate conglomerate. On the other hand, I've gotten product samples before that have exceeded my wildest expectations, like pressure sensing film and other useful goodies. I'm hoping for at least 25 pounds.

RB, I know what you're saying about "tunnel vision." I've been looking at tin salts as well. Both tin (II) and tin (IV) chlorides are available commercially, but they are pricey, no doubt. Manganese, not so bad. I just need to take this stuff in order, and priority 1 for me right now is investigation of PbO2.

Esteemed assembly - question on immersion heaters. For a two gallon bath, the wattage requirement comes in at several hundred watts minimum, unless you insulate very well and don't mind waiting 4 hours to heat the bath to 60 or 70 degrees. The best heaters have a PTFE/PFA coating on them, but expen$ive doesn't begin to describe them. 316SS would normally be suitable, but stray Fe ions in the bath = bad juju. I found that certain heaters sheathed in an inconel alloy will shrug off nitric with ease, especially at these concentrations, and I am going to try and adapt an inconel-sheathed cartridge heater for immersion duties.

The question is this... how would any of you heat a plastic 2 gallon plating bath to 80 degrees C, and hold it there for hours if needed? No iron allowed. It sounds simple, but it's not! I like the idea of cobbling relatively cheap surplus heater elements into immersible constructs, and save a lot of $$. Thoughts?

Omega ..Oh man ...grab your wallet before they do ....
sheesh

On those cartridge heaters, if you get those in a standard size diameter which corresponds to the tubing sizes used
with plumbing compression fittings, then you can stick them
right through the compression fitting for mounting. Those
fittings available in some plastics would probably work fine
or you could simply spiral wrap with teflon tape and forcibly
twist it as an interference fit in a teflon bushing.

[Edited on 5-12-2008 by Rosco Bodine]

Omega wasn't too bad this time. I think they are loading up a bit more with the Taiwanese/Chinese goods. The temp controller was something like $70. I could have saved some on ebay, but I'm sick of eBay a bit, mainly because when you are putting a project together like this, and you need many items from several different sellers, there is ALWAYS one seller who is sloooooow, and the whole thing drags to a halt. At least with Omega, I get the stuff in two days.

Learned something... wattage density is important. You don't want the watt density to be too high. But the LOW watt density models have the less desireable 304SS sheath, not the incoloy. Solution: Order 240V high-density heaters, that come with an incoloy sheath, and run them on 120V. Watt density cut in half.

They look good. The ones I have are a decent fit in a 1/2" copper pipe. I bought enough fittings and such to create a copper "L" shape. Pics to follow of the deluxe plating rig at roughly 75% complete.

Actually the watts drops to 25% at half voltage because the amperage also halves ....I favor incoloy also , the original calrod material you can go to an orange heat
with it no problem, and self oxidizes to that nickle black
finish. Accept no substitutes when it somes heater elements, or refreshing the barrel on your well used machine gun, use incoloy , the proven performer

As for Omega, I was recently the proud recipient of a
few quartz sheathed dual element type K thermocouples,
which I got surplus for cheap, but I checked the list price and they are over two hundred smackers each.

After a couple days of work, using the surplus cartridge heaters, and the stuff from Omega, the heater controller is finished. Programming the stupid thing was typical Chinglish, but I managed to get through it.



The heater chosen was a 240V 1 kilowatt, running at 120V, encased in Cu. 4 liter beaker, cold water. I was tempted to set it up for a simple "on/off" control, but instead went for the full PID cotrol, and I'm glad I did. Fired up, the 250 watt heater brought the 4 liters to temp inside of an hour. Best of all, it NAILED the selected temp, and held +/- 0.1 degree C all day long. it turned out nice... I'm happy with it.



For more info than you'd otherwise care about, in a simple language:

http://www.apcforum.net/forums/blog/swede/index.php?showentr...

I'm still trying to find some titanic, intergalactic alumina corporation to send me, a peon, some colloidal boehmite. No luck yet, but I've got some leads.

Nickel Nitrate - the patent calls for some, I believe as a grain refiner. It is complexed with .6H2O, and I tried a simple experiment to dehydrate a 10g sample. Into a stainless bowl, furnace fired up to 250, a standard dehydration temp, and 6 hours later, I had a molten puddle of green, carcinogenic goo. WTF? 6 hours at 250 should have driven off every speck of water. Then I looked up the characteristics of nickel nitrate. melts at 57??!! BOILS at 137?! What exactly is boiling off? The water? I can see it decomposing, but not boiling. Am I turning it into Nickel Oxide and various nitrogen oxides? Weird stuff. You're paying a lot of money for water with Ni(NO3)2.6H2O Can anyone elaborate on the decomp mechanism?

All that remains is enough lead nitrate to stock the big bath. I am going to try several micro setups so that I do not ruin a lot of lead nitrate with additives like surfactants, Bismuth and nickel salts, etc.

You can't dehydrate nickel nitrate by heating without decomposing it to a basic nitrate and then to an oxide.
The hexahydrate is the normal stable form and is gotten
by gentle evaporation at below 57C of solutions. Quantifying
what you have from the solubility data for saturated solutions is close enough for this sort of work, and you shouldn't really need to make up solutions from a previously isolated hexahydrate crystal form, if that is inconvenient.
From the following chart it would appear there is also a stable trihydrate which would crystallize from cooling hot solutions above 57C , transitioning to the hexahydrate for evaporative crystallizations at below 57C. For our purposes it should be accurate enough to stipulate that at room temperature a saturated solution of nickel nitrate is 50% by weight nickel nitrate, calculated on the anhydrous molecular weight basis of 182.7 g/mole. The hexahydrate is 290.8 g/mole. These figures reconcile with the molar water ratio
charted at 20C, confirming the percentage solubility is expressed on the basis of the anhydrous salt.





[Edited on 11-12-2008 by Rosco Bodine]

Some simple updates - I'm waiting on my big Chemsavers 10kg lead nitrate delivery. I've got 1 kg currently, and am tempted to do some mini experiments. The two big things are the completion and successful testing of the heating system. The cartridge heaters have exceeded my expectations, with one caveat... it is important to keep the wattage density as low as possible, yet still have sufficient power to heat and hold the bath in weather that's pretty damned cold. The way to do this is run them at reduced voltages. This in itself presents problems. A 240VAC cartridge heater that is listed as a kilowatt can be a bulky beast. I've got a pair of them, and their dimensions are 1/2" diameter by about 7" long. At 120V, they will put out 250 watts apiece. Singly, or paired, they will raise a 2 gallon bath of ice water to near boiling in about an hour. BUT (big but) the entire heater needs to be immersed, or you end up with a hot section above the liquid.

This may or may not be a problem. The incoloy sheathes can handle complete air exposure. The sheathe will turn gray, and my guess is there just might be a visible glow if the watt density is high enough. But this is simply too concentrated a heat, and for a liquid bath, it needs to be spread a bit by some sort of additional sheathing which conducts heat well, OR using multiple, lower-wattage devices strategically placed in the bath.

In my freebie "bonus" bunch of cartridge heaters, there are a pair of 120V micro-heaters about the size of a pencil perhaps 3" long. I'm trying to figure out a material that I can drill and install these heaters into, which I can them immerse in the bath, with no ill effect to the chemistry of the plating reaction.

Cu is a good choice, but I worry - if the Cu is not tied to the cathodes electrically, will there be a problem? As the nitric acid concentration increases, the Cu sheathes will begin to dissolve, donating Cu++ ions to the bath, not necessarily a bad thing.

Titanium would work, but Ti has very poor heat conductance. Plus, I have no thick slabs of Ti. Aluminum? I have a massive stock of aluminum in all shapes, sizes, and alloys, but again, I am concerned about pollution of the plating bath with unwanted metals. Nickel would work, but I have no pure Ni in an appropriate form.

My original plan to rotate is still the plan. The shape of the cathode(s) will be hemispherical, with the spinning anode on the convex side. I originally planned on two cathodes, but if the anode spins, what's the point in two? I can simplify things by using a single cathode, and this in turn will allow for smaller test baths.

Xenoid's idea of vibration was simply genius, and I decided to incorporate a vibrational system into the boom arm suspending the anode. An old Pittman DC motor was cannibalized, and mounted:



Part of the system is an adjustable weight. When combined with a variable DC supply to the vibration motor, the effect is amazing... I can go from a gentle, high-frequency pulsation, to a vibration so intense, the entire rig will walk off the bench. Somewhere in between is a good setting! Ive got a dual DC lab supply that will take care of both plating and vibration.





I worked hard at using quality wiring for most of this rig, especially things such as extension wired for the RTD probe. A good source of PTFE-coated wire is surplaus aviation wire off eBay. Like everything else for aircraft, it is top-quality stuff.




Note the waxed polyester cord to secure wire bundles. Infinitely better than cable ties.

I guess my real question today is the use of oddball metals in this plating bath for the cartridge heaters. Attaching the Cu heater sheathe to the cathode will work, but it's a bit limiting. I'm curious espeially about Al. If Al has no problems, I will be all set.

The way this thing is turning out, if the plating fails,it will be in my technique, not the hardwer. I think I've got a system hat should plate well.

Suggestions?

Kaowool and a blender maybe

I would try the long fiber stuff and low porosity, specify
a filler reenforcing fiber material like is added to plastics for strengthening and the previously calcined dispersible
stuff would be good. Gamma whiskers is what you want.

First you crawl through the high grass just before dawn
when the gammas are known to feed ,

Well it's about the middle of Advent,
so maybe you'd like this other pretty one too.
I mean things are supposed to gradually become more cheerful and celebrative

http://www.youtube.com/watch?v=nKIPMMPPcu4&feature=relat...



[Edited on 12-12-2008 by Rosco Bodine]

On my recent trip, I went through several of the patents relating to lead dioxide plating, and learned quite a bit. One of them is that the cathode current density should be 2x to 3x the current density of the anode... this means a fairly small cathode. Question - do we count the entire surface area of the Cu cathode, or only the portion exposed to the flow of electrons? If I've got a sheet Cu cathode in there, do you ignore the side away from the anode?

The impression I got was that this process should be well within the reach of the average home chemist. Obviously, this is not the case, and hundreds or thousands of failed PbO2 anodes attest to this fact.

I've got everything... got the temp controller, the correct surfactants, Cu and Ni nitrates, Bi salts, NaF, got a rig that will rotate, vibrate, do both, or neither. Good power supplies. Lead nitrate (lots) and PbO, sheet Pb too. THIS WILL WORK! IT MUST!

I've had some thoughts unrelated to the patent description. None of the patents I read discussed PbO2 over MMO... they were using graphite, tantalum, Ti, and other substrates, with success. My thoughts related to the preparation of the substrate. Obviously, it must be clean, but there are different definitions of clean.

Under a microscope, the MMO surface is quite rough, and probably ends up containing quite a bit of air trapped in pores as it enters the plating bath. I was thinking about a pre-plate dip or etch, using one of these three solutions:

1) Pure water, or water with a minute amount of surfactant
2) dilute HNO3
3) a small amount of the actual plating electrolyte

THEN, pulling a vacuum. Get the air out, get the liquid into every single crack or crevice, so once the plating starts, it will be 100% coverage.

For a substrate like Ti, I think using an abrasive blaster on it would be an excellent preparatory step, or failing that, a scotch-brite pad to mechanically and minutely score the metal surface; then, into the etch/prep bath.

Sound good? Or a waste of time? I'm going to try plating one of my small test anodes probably tomorrow.

Patent No. US 4444642 is a LD over MMO. It's the only one that I know of. This patent was mentioned before here somewhere.

Can you remember the patent number that said the current density on the cathode should be 2 or 3 times the CE on the anode when plating LD?
Hard to know if you should count the total area of Cathode.

Are you going for an Alpha coat (Tartrate bath, or high CE in Nitrate bath at the start) before a Beta coat with the anode you are going to make?

With a tank the size that you have you are going to have excellent anodes (unless you are going to make absolutely huge anodes).
Plating Ti mesh (or flat plate with lots of holes), as opposed to a flat plate or rod, greatly alleviates the adhesion problem IMO. It will be unlikely that the LD will start to flake off. Substrate and LD are simply married like wire and concrete!
The big issue is electical contact between LD and Ti, or to put it another way, the lack of electrical contact because of the dreaded formation of Ti Oxide. The interface coat looks after that aspect. Pt, Tin Oxide, MMO and Ebonex (a conductive Oxide of Ti) are the only interface coats mentioned in the patents etc that I am aware of.

As far as cleaning the MMO, I would give it a wash in some solvent to degrease it, alcohol sounds good. Try to avoid handling it in the first place.
Don't go near the MMO coated Ti with an abrasive or an etch bath.
If you were starting from scratch (no pun intented) making MMO coated Ti you would of course etch and abrade the Ti.

Dann2

Quote:

Originally posted by dann2 Hello Folks, Patent No. US 4444642 is a LD over MMO. It's the only one that I know of. This patent was mentioned before here somewhere. Can you remember the patent number that said the current density on the cathode should be 2 or 3 times the CE on the anode when plating LD? Hard to know if you should count the total area of Cathode. Are you going for an Alpha coat (Tartrate bath, or high CE in Nitrate bath at the start) before a Beta coat with the anode you are going to make? With a tank the size that you have you are going to have excellent anodes (unless you are going to make absolutely huge anodes). Plating Ti mesh (or flat plate with lots of holes), as opposed to a flat plate or rod, greatly alleviates the adhesion problem IMO. It will be unlikely that the LD will start to flake off. Substrate and LD are simply married like wire and concrete! The big issue is electical contact between LD and Ti, or to put it another way, the lack of electrical contact because of the dreaded formation of Ti Oxide. The interface coat looks after that aspect. Pt, Tin Oxide, MMO and Ebonex (a conductive Oxide of Ti) are the only interface coats mentioned in the patents etc that I am aware of. As far as cleaning the MMO, I would give it a wash in some solvent to degrease it, alcohol sounds good. Try to avoid handling it in the first place. Don't go near the MMO coated Ti with an abrasive or an etch bath. If you were starting from scratch (no pun intented) making MMO coated Ti you would of course etch and abrade the Ti. Dann2