Sciencemadness Discussion Board - Thoughts On Anodes

Thoughts On Anodes

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Xenoid - 18-11-2008 at 19:19

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 -

Swede - 19-11-2008 at 08:06

Xenoid, that is an awesome idea! I never would have thought of that. Your rig is assembled, you need to try it! Are you lacking chemicals or something?

By running the vibrator motor with a variable DC supply, you can fine-tune it during the actual plating process so as to achieve a sort of low frequency, higher amplitude "waving motion" through an arc of maybe a mm or two. I think that would work better than a higher frequency. To get a low frequency, you'd need a larger weight on the motor, and maybe some sort of a thinning of the support arm. Very clever concept.

What are some thoughts on heating methods for the bath? I've got a standard all glass immersible aquarium heater, but I suspect it'd need to be hacked so as to bypass the thermostat. One device I've always wanted is a variac, a variable AC transformer, for this sort of job. Bypass the heater thermostat, hook the heater up to the variac, and use the variac to control the heater output.

The MMO --> perchlorate test cell has a faint dusting of perc, meaning the solution is saturated, and it's starting to fall out. The liquor tests a strong positive using methylene blue for perchlorate. It's been 40 hours so far at 15 amps, (600Ah) and the liquor started as pure chlorate, no dissolved perc. The bath temperature is about 60C. 2.5 liters at 60C should hold about 200 grams of perchlorate, probably less as we are dealing with mutual solubilities here. For the sake of the argument, let's assume the cell has produced 180 grams of potassium perchlorate.

At 100% efficiency, it requires 53.25 Ah to convert 1 mole of chlorate to perchlorate. Simplifying the math a bit yields:

Efficiency of a POTASSIUM chlorate --> perchlorate cell

E = Efficiency
W = Weight of yield, in grams
Ah = Ampere-Hours used

E = (38.42 * W) / Ah

The very early, preliminary, and very much guessed-at efficiency is: 11.5%

This presumes that the cell is in the state that I believe it to be, namely saturated with 180 grams of perc and just now beginning to fall out a bit.

There is no smell of ozone. In fact, there is no smell at all that I can detect. I'm going to let it run another day or three and see if perchlorate does in fact continue to accumulate. But efficiency-wise, it's not looking good.

[Edited on 19-11-2008 by Swede]

tentacles - 19-11-2008 at 09:13

Swede: I use my hotplate/stirrer for heating the bath.. I've found that a setting of just over "1" gives me about 65C after a couple hours. I usually heat it up on a higher setting and then back off.

jpsmith123 - 19-11-2008 at 09:46

IIRC, in Beer's MMO patents he states a belief that the MMO coatings are porous with a large surface area. I wonder if this could be the reason for the low efficiency?

Maybe ClO3 ions, because of their size relative to typical MMO pore size, do not have access to most of the active surface of the MMO coating, so it has no choice but to make more O2/O3 (more than it would if all species had equal access to the surface)?

Are the surfaces of PbO2 coatings relatively non-porous? Maybe PbO2 is useful for ClO4 production mainly because of this physical property?

Swede - 19-11-2008 at 14:10

I pulled the plug on the test cell. Since this morning, there was no additional visible perchlorate production. There remains a light dusting, about a teaspoonful floating around in there. It was going nowhere.

Without any reasonable efficiency, I see no reason to continue testing or modifying any parameters like pH or temperature, or using additives. MMO alone (this formulation at least) is not sufficient for perchlorate production.

jpsmith123 - 19-11-2008 at 15:32

Rats. Well I'm sorry to hear that. Sounds like it went from making ClO4 at low efficiency, to not making any more ClO4 at all. Can I ask, what was the cell voltage and current when you began vs when you pulled the plug?
Also, is there any visible wear of the MMO coating?

Edit:
I had a few more thoughts about your MMO test.

Your cell did make perchorate, but it apparently stopped doing so at some point. If the coating was not damaged, then I take this to mean that the efficiency is a strong function of the chlorate level.

Maybe if you were using NaClO3 rather than KClO3, at a much higher concentration, the cell might have made lots of perchlorate at an efficiency much higher than 11.5%

So although your results were discouraging, it's possible the MMO anode might still be useful in a cell using NaClO3, especially if the chlorate concentration is kept up.

[Edited on by jpsmith123]

Rosco Bodine - 19-11-2008 at 15:45

There's quite a few MMO formulations which are selective and efficient for producing O or Cl for example but won't efficiently produce perchlorate.

Bismuth as Bi2O3 is probably your friend as the cheapest doping material reported to be catalytic for perchlorate as a component of an MMO coating. It reportely also has benefit in coplating with PbO2.

Swede - 20-11-2008 at 06:54

jpsmith, the voltage (at 15 amps) hardly varied at all throughout the run, about 6V. I think your observation about using sodium rather than potassium might be worth exploring, but my guess would be even then, the efficiency is not going to be above 30 or 40%

The MMO coating looked fine visually. The Ti cathode face next to the anode had a very light gray smut on the surface which wiped off with my fingers. I don't know what the smut was, and I'm hoping it's NOT MMO material. I'll take a closer look today at the anode, vs a section of unused mesh.

The transition of chlorate to perchlorate (on a molar basis) happens much faster than chloride to chlorate, only 52 Ah/mole for perchlorate, vs 161 for chlorate. In this exact same cell, using a jewelery-plating Pt anode, the bottom of the cell had accumulated a thick layer of perchlorate after only 48 hours had passed.

My gut feel in these cases is to look to industry. I haven't heard of MMO being used for commercial perchlorate yet. I think if it was practical, they would be doing it. Perhaps there are formulations that do make perc, but with unacceptable wear rates.

Edit: I am shopping for titanium tubing for research/anode purposes. Frankly, the difficulty in sealing flat strap hangers to the lids of cells is becoming quite annoying, and the use of round tubing would permit the use of viton o-rings to seal, as well as a simple drilled hole in the cell lid, vs. a tiny milled slot, which is difficult to do properly.

I've worked both CP and alloy titanium... the CP variety is much softer and easier to work, and I do prefer it, but it is much harder to find. Does the use of alloyed Ti create problems in these cells? Any recommendation on suppliers of Ti tube?

There's an eBay guy called Titanium Joe, but he's in Canada. Nothing wrong with that except customs. My favorite supplier of CP Ti sheet:

http://www.aedmotorsport.com/Titanium/CPGrade2Sheet.htm#A

This guy has a huge number of assorted cuts of CP sheet. The only limiting factor is the thicknesses are all 0.039" to 0.041", slightly thinner than I'd like but still a good thickness for electrode use.

[Edited on 20-11-2008 by Swede]

Swede - 21-11-2008 at 06:57

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.

jpsmith123 - 21-11-2008 at 10:27

Swede, that is certainly an impressive mechanical setup you've got there...obviously a lot of time and effort went into it. I hope in the end it pays off for you.

Speaking of PbO2, does anyone remember what kind of efficiency Dann2 stated that he got with his PbO2-over-SnO2-over-Ti anode? I don't remember the number, but I seem to recall that it was disappointing. Also, IIRC there was some noticeable wear on the anode or sludge on the cathode or something.

Anyway, PbO2 may work better over MMO than SnO2 but that remains to be seen.

As far as "looking to industry" is concerned, keep in mind that industry is almost single-mindedly concerned with "efficiency" whereas for us that is generally of lesser importance; for example, industry no longer uses graphite to make chlorate but for amateurs more chlorate is made with graphite than anything else I think.

What I find so frustrating about anodes for perchlorate is that it seems more art than science...it's all empirical...nobody seems to know exactly what's going on.

watson.fawkes - 21-11-2008 at 14:23

Quote:

Originally posted by Swede
The MMO coating looked fine visually. The Ti cathode face next to the anode had a very light gray smut on the surface which wiped off with my fingers. I don't know what the smut was, and I'm hoping it's NOT MMO material. I'll take a closer look today at the anode, vs a section of unused mesh.

Although it's occurred to me before, it hasn't been too important to mention until now. You might consider, when you construct your cells, making the electrodes individually removable so that they can be weighed. If you're losing MMO through any mechanism, it would show up on the scale.

What else is attached isn't relevant as long as you can get a consistent tare weight. This means that you could seal a strip electrode into plastic as you've been doing, but, say, make that plastic a disc with a rebate for an o-ring.

dann2 - 21-11-2008 at 15:11

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

Rosco Bodine - 21-11-2008 at 15:36

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]

Swede - 22-11-2008 at 05:52

Quote:

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.

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.

jpsmith123 - 22-11-2008 at 07:30

Well after reading some more of Dann2's prolific perchlorate propaganda, it seems that (to the extent results from PbO2 and Pt studies can be generalized) ClO4 formation is favored by: (1) high anode current density, (2) high ClO3 concentration, and amazingly, (3) high ClO4 concentration.

(Also, the more I read about it, the more I'm convinced that the processes going on at the anode in a perchlorate cell are not fully understood).

tentacles - 22-11-2008 at 07:48

One pass could only work for perchlorate, unless you plan on forming all chlorate anodically (inefficiently)..

That guy seems to be sold out of lead nitrate already! I've been thinking about that 10kg package on chemsavers for $120, to split up amongst us (and anyone else who might want some). That's a LOT of lead nitrate, but it's only $6/lb.

I've been kicking some ass on my lid adaptor since yesterday, I hope to put the cell in action tonight. I'll charge it with some commercial chlorate I've got. Wish me luck.

US3506561 Fibrous Alumina Conductive Catalyst Carrier

Rosco Bodine - 22-11-2008 at 13:02

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 794 times

Swede - 23-11-2008 at 05:44

Very interesting... This is worthy of further study. It appears that it is relatively easy to create an especially thick, structurally sound coating which would protect any underlying substrate. I'm going to print it out and really give it a good read.

Tentacles, I look forward to your run. Can you snap a few pics while you're at it? How much commercial chlorate do you have? A 5 gallon bucket cell is going to require a lot of chlorate. Or is your adapter for a 2.5 gallon setup?

The problem with test runs is the "loss" of chlorate... I've probably got a kilogram of chlorate tied up in failed perchlorate runs. I've just been dumping it (chlorate + perchlorate liquors) into empty milk jugs, waiting for an anode capable of finishing the job.

I think before I proceed further, I need to acquire a milligram scale, probably one of the cheap jobs off eBay, so as to measure anode erosion.

Rosco Bodine - 23-11-2008 at 08:36

Yeah this is an interesting ceramic precursor, partially soluble fiber which could be a key component in making durable baked ceramic coatings.

If you do a google patent search under fibrous alumina it will bring up a lot of interesting stuff. This same sol is used as a rigidizer for refractories like kaowool, and evidently a small percentage of it added to certain dip and bake coating precursors, reenforces the coating and increases the adhesion by the presence of the microscopic whiskers of gamma alumina which remain as a bonding matrix after pyrolysis, and are believed to possibly react somewhat with the materials they are bonding. IIRC this is the stuff which is used to bond the catalyst material to the honeycomb substrate in a catalytic converter and it will also cement teflon to glass or metal , but most interesting for us is that it aggresively bonds with other
metallic oxides like the surface oxide on a metal or the catalytic coating oxides pyrolytically produced from precursors, via a reactive molecular reaction where the
gamma alumina whiskers appear to serve as something
like a "ceramic solder" which superficially "alloys" itself on baking with the materials it bonds as an intermediate filler material. It is sort of like whiskers of hot melt glue which melt only superficially, fusing with whatever they are in contact, and forming a reactive bond, which then solidifies and further fusion of the alumina whisker ceases, so it remains as a reenforcing fiber matrix on cooling.

tentacles - 23-11-2008 at 09:05

I realize it's a tad off topic, but I wonder if that alumina stuff is what the "pre treatment" is for preparing pans (and such) for powder coating with teflon?

I finished the adaptor last night, all except for a pH probe holder. Going to wait on that until I figure some stuff out.. Like a larger pipe tap. The probe is .499" and that's just a bit too big to craft a compression fitting that has 3/8" NPT threads. The other fittings came out very well. I even put in a fill/dip port (which I will probably eventually use for dosing HCl, with a clever adaptor.

I've only used about 14" of my 5' length of PVC rod, too. Used a few inches of my CPVC rod because it was handy.

Pics:
http://pyrobin.com/files/sdc10045.jpg
http://pyrobin.com/files/sdc10049.jpg
http://pyrobin.com/files/sdc10050.jpg

I used twisted up heavy (orange) PTFE tape to seal the lid adaptor. I just partially screwed on the lid, then wrapped the string around the screws (and back over itself a bit).

Now comes the hard part - digging out my GD aqarium pump, and finding my heavy copper wire. I picked up some brass bolts for the electrical connections.

dann2 - 23-11-2008 at 11:35

Take a look at the patent example one pasted here.
They are actually using a Chlorate solution to strip MMO (Ru Oxide).
The current density is high though at 600ma per square cm.

______________________________________
EXAMPLE 1

The coated metallic electrode comprising a titanium substrate having a ruthenium oxide coating thereon which was to be cleaned was used as an anode, and a current was passed between said anode and steel cathodes, in 50 percent by weight of an aqueous solution of sodium chlorate at 60 A./dm. 2 of anode current density, for 30 minutes. During this treatment, the bath temperature rose from 20° C. to 25° C. Bath voltage rose gradually from 5.5 volts, and after 25 minutes from the start of the treatment, began to rise rapidly and was 7.5 volts at the end of the treatment. (FIG. 1 is referred to.) The anode was removed from the bath, and rinsed with water and dried. The weight loss on the substrate while the current was passed was determined to be 0.1 percent. Thereafter, the thus treated metallic electrode was dipped into 5 percent by weight of an aqueous solution of hydrofluoric acid for 3 minutes to complete stripping of the coating. The weight loss of the substrate during this treatment was 1.6 percent. After the former treatment, the coating remaining on the surface of the substrate was completely stripped by dipping into the hydrofluoric acid solution and by rinsing with water, and the surface of titanium substrate was seen to be the same as that of an original substrate.
________________________________________

Dann2

Attachment: Surface preparation process for recoating of used coated metallic electrodes - Patent RE28849.mht (203kB)
This file has been downloaded 1074 times

jpsmith123 - 23-11-2008 at 12:46

Well that certainly doesn't instill confidence. (BTW the patent also claims that the process will remove "iron group metal oxides", presumably including Fe3O4).

I suppose a perchlorate cell will erode *any* anode material...and like so many other things the problem is reduced to a matter of degree.

It would be nice to find some inexpensive, efficient coating than can be easily electrodeposited over a commercial MMO anode, used to make ClO4, and then re-coated after a few runs. Maybe PbO2 is the answer but I just don't like that stuff.

Edit:

Maybe Rosco's right about Bi2O3; it might be a good candidate for a top layer over MMO. Does anyone know if it can be easily anodically electrodeposited?

[Edited on by jpsmith123]

tentacles - 23-11-2008 at 13:53

Well, it's hooked up and running at 18.1A / 6.2V - no idea why the current is so low for this voltage. Anode is about 5/8" from the cathodes. Maybe I should have put them closer together.. Not that I can't make a new one. Swede, what was your cathode to anode spacing?

Oh, and yes, I do in fact know the cathodes are a bit staggered - it just worked out that way because of the width of my CPVC sheet and the width of the straps on the cathodes.

edit: Now that I think of it, the current could be more of a factor of solution than anything else - I only had a bit over 1100g of KClO3, less than I'd thought. I only used about 18.5L of water, and added 1.5g/l NaF. Getting lots of ozone and there's a pink tint to the electrolyte. WTF?

[Edited on 23-11-2008 by tentacles]

dann2 - 23-11-2008 at 22:04

Hello,

Are hard drive platters coated with Pt or an alloy contining Pt.
There seems to be some Pt is some of them. Would they do as a substrate. Drill them like a grid and away you go.
Souns too good to be true/workable.
http://shop.ebay.com/sis/_W0QQ_kwZ110Q20HardQ20DriveQ20Platt...

The BismutH Oxide for Perchlorate has only been mentioned on one patent that I have ever seen. See the last example. It envolves plasma spraying etc.
It has been mentions for plating with ld by adding the Nitrate to the plating tank but you are still dealing with Lead compounds.

Dann2

Attachment: US 4272354 Bismuth_DTO perchlorate anode.pdf (253kB)
This file has been downloaded 749 times

tentacles - 23-11-2008 at 22:32

dann: Apparently older/some HDD platters used a cobalt-platinum-something alloy, that was up to 40% platinum as I recall. I've tried dissolving some old HDD platters in HCl (get rid of the useless metals first, I always say) and as nothing insoluble remained, am skeptical about finding the proper type. Most likely the HDDs that used such expensive materials were the drives of the 80's and early 90s. You know, the 5 1/4" monsters that were multi-thousands at release.

Got home and the power supply had kicked off the overvoltage switch so I backed it down to 6.15V - the protection seems to kick on at 6.20V and I guess 6.18 was toeing the line too closely. The current is down to 12.5A for some reason, but that could be because the solution has cooled. I used hot water to make the electrolyte. Our tap water here is about 65 PPM TDS, pretty clean stuff.

edit: I did take a peek at the anode and it appears unchanged, and there is no crud or residue on the cathode. The bubbler is still blasting out air... An airstone/diffuser of some sort would really circulate the water much better than the huge chunks of air I've got coming up.

[Edited on 24-11-2008 by tentacles]

Swede - 24-11-2008 at 05:25

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 - 24-11-2008 at 07:39

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 - 24-11-2008 at 16:32

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 - 24-11-2008 at 19:52

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]

Ceria as a perchlorate catalyst

watson.fawkes - 24-11-2008 at 22:30

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, CeO2. 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 - 25-11-2008 at 05:25

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 - 25-11-2008 at 07:36

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 - 25-11-2008 at 08:27

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 - 25-11-2008 at 08:58

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 - 25-11-2008 at 09:21

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 - 25-11-2008 at 10:40

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 - 25-11-2008 at 11:06

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 - 25-11-2008 at 11:30

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 - 25-11-2008 at 11:54

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)
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Rosco Bodine - 25-11-2008 at 12:31

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

jpsmith123 - 25-11-2008 at 13:49

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)
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Rosco Bodine - 25-11-2008 at 16:55

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 - 26-11-2008 at 08:08

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 - 26-11-2008 at 08:14

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 - 26-11-2008 at 09:02

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)
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Rosco Bodine - 26-11-2008 at 09:45

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 - 26-11-2008 at 14:03

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 - 26-11-2008 at 15:00

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 - 28-11-2008 at 07:30

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 - 28-11-2008 at 08:54

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]

watson.fawkes - 28-11-2008 at 10:11

An excerpt from the review in a 1921 journal:
<a href="http://books.google.com/books?id=-nMQAAAAIAAJ&pg=PA421&ci=56,726,856,410&source=bookclip"><img src="http://books.google.com/books?id=-nMQAAAAIAAJ&pg=PA421&img=1&zoom=3&hl=en&sig=ACfU3U2KFo6kpQUGcZSZiL4jMEFKh1u9EQ&ci=56%2C 726%2C856%2C410&edge=1" border="0" alt="Text not available"/></a> <a href="http://books.google.com/books?id=-nMQAAAAIAAJ&pg=PA421&ci=56,726,856,410&source=bookclip">Journal of the American Ceramic Society By American Ceramic Society</a>

Rosco Bodine - 28-11-2008 at 10:28

Yeah I saw that reference along the way to requesting the book. Evidently it is the highly activated "nano-tube" or whisker form of the hydrated alumina which looks like a mold growing at a visible rate from the surface of amalgamated aluminum in air. So this may well be the easy source for the filamentary form of the precursor which may be useful for our purposes as a dopable catalyst or a reactive catalyst carrier, and thixotropic dip precursor additive which serves as a bonding agent and reenforcement fiber in baked MMO coatings. Cobalt aluminate may even form by acid digestion of the raw hydrated whiskers in percobaltous acid, followed by pyrolysis.....resulting in a kind of nano-structured spinel material which sets as a sintered "fiberglass-like" mat
of a ceramic felt , that is conductive and is an active anode material. Some added Bi doping there might result in the closest thing to an indestructible anode which we have contemplated.

[Edited on 28-11-2008 by Rosco Bodine]

dann2 - 28-11-2008 at 10:38

Hello,

Quote:

Originally posted by Swede
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'll second that!
Ti substrate (with one interface coat) LD anode will hopefully solve the Garage Perchlorate Makers quest for a durable and reasonably cheap anode made by a repeatable method.

Quote:

Originally posted by Swede
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.

My own opinion (it's only one opinion, milage will vary and most folks are capable of making up their own minds) of the hugh volumous verbose amounts of articulate 'scientific reasoning' regarding the more exotic (allegedly definate solutions or routes to solution of the problem) are in the fruit cake category. Argueing long and hard (it's been quite a while now though) against (AGAINST) Ti as a substrate to possibly good solutions, is a very tangible demonstration of my opinion. Sometimes I wonder are some folks taking the piss and having a good hearty laugh.

The one and only patent showing LD on MMO (US 4444642) plated the LD at a highish current density at the start (Alpha LD) then decreased the current density after a bit (Beta starts to deposit). This method might save the bother of starting with a Tartrate bath for the Alpha.
The ability to plate Alpha then Beta from the same bath simply by changing the current density has been disputed in places.
My own opinion it that if you want a definite coat of Alpha then go with a Tartrate bath. Since the amount of Alpha plating is going to be small you do not need a very big bath.
The crystal structure of Alpha is more close in nature to Tin Oxide, that is why it sticks better. Don't know about Alpha/MMO but since they appear to use Alpha as a first layer in the patent above than it would appear that it does indeed adhere better to MMO that Beta.
Platinum or Platinized Ti, I don't know.

Magnetite I have been told has a crystal structure miles from Alpha or Beta and therefor is probably not a good substrate.
Graphite cannot be plated with Alpha I believe. You must start with a Beta.

Dann2

watson.fawkes - 28-11-2008 at 10:41

I was impressed with the large surface area indicate by water adsorbtion in that review. It contains a hint of a failure mode that might need to be dealt with—a pinhole in an outer coating that leads to mechanical failure of the substrate.

Here's another old reference, this one with pictures. Click on the link at the bottom to a bit more than shown here.
<a href="http://books.google.com/books?id=MF1AAAAAIAAJ&dq=fibrous%20alumina&num=100&client=firefox-a&pg=PA258&ci=154,307,789,951& source=bookclip"><img src="http://books.google.com/books?id=MF1AAAAAIAAJ&pg=PA258&img=1&zoom=3&hl=en&sig=ACfU3U1YidoffwZeipzdxhrgRXcMa-fqLA&ci=154%2 C307%2C789%2C951&edge=1" border="0" alt="Text not available"/></a> <a href="http://books.google.com/books?id=MF1AAAAAIAAJ&dq=fibrous%20alumina&num=100&client=firefox-a&pg=PA258&ci=154,307,789,951& source=bookclip">Colloids in Biology and Medicine By Heinrich Bechhold, Jesse Godfrey Moritz Bullowa</a>

Rosco Bodine - 28-11-2008 at 10:59

Yeah the nanostructured alumina whiskers are sort of an ultimate form of "activated" alumina, having an aerogel like matrix evidently, formed from filamentary structures.

It is intriguing stuff on several different levels, anode coatings being only one of many potential uses. This material is what they use to filter virus particles, or even molecules from their suspended state in gas or liquid,
so it truly is a nanoscale material.

watson.fawkes - 28-11-2008 at 11:03

There's a paper titled "Formation of Nanostructural Oxide Fibers" in the volume Nano-Architectured and Nanostructured Materials, ed. Champion and Fecht. Hydrated cellulose was impregnated with aluminum oxychloride (also with other metals) and then dried and fired. The scaffolding fiber burnt off. Oxide fibers formed in the same shape as the scaffolding fiber.

This seems worth investigating, as the process seems doable with a temperature-controlled furnace. I don't know about the availability or ease of synthesis of oxychlorides.

US3039849 Amalgam Derived Fibrous Alumina

Rosco Bodine - 28-11-2008 at 11:32

I don't see that one sorry. It seems like a more complex route than working with the precursor which may come off by the tablespoonful as you watch it growing like a white snake, from the surface of some scrap very pure aluminum electrical wire, which has been amalgamated.

But I do see the potential usefulness of a nanowhisker alumina used as a sort of structural reenforcement having serious bonding capability as an ingredient in a dip and bake coating scheme, as a potential solution for any adhesion problems, and also to increase the thickness of build coatings which are applied as a series. Having the added ability to function as a catalyst carrier is a bonus.

As for the porosity, well that can be plugged up with
sintered DTO, simultaneously in the precursor dip or subsequently as a followup coating by dips in precursor not containing the fibrous alumina additive. What went before would soak it up, since the electropositivity is shifted to electronegativity after sintering. Kind of beautiful as a strategy actually....if the physical chemistry goes as planned.

Something I have wondered about as an unexplored idea
is the use of magnetite nano crystals as a bi-electrode ,
embedded in the surface of a lake of DTO as tiny particulate islands. Something like the same way as palladium black or platimum might be used as distributed micro-particles fused onto the surface of a conductive ceramic , but of course magnetite would be far less expensive. The bi-electrode
effect is sort of an unknown, like the elephant in the room.
It might be one of those undiscovered simple things that
has been overlooked. And just because there may be no ready reference spelling everything out 123 in a patent or a journal, doesn't necessarily mean it isn't so, or isn't known,
so one should keep a certain reserve concerning possibilities
for further experimental work which could be worthwhile, especially for stuff which has not been examined and already ruled out by authoritative tests and testers who know what they are doing.

Attached is a patent which I haven't had time to read thoroughly, but on first glance it may be what we are looking for as a fibrous alumina source of least complexity.

US3039849 Amalgam Derived Fibrous Alumina

Hmmm this patent looks familiar to me and I think I may have looked at this patent before in connection with castable refractory cement applications, although I don't recall posting it here. But it would make sense as it would serve the same purpose as reenforcement and bonding in thicker layer refractory compositions.

[Edited on 28-11-2008 by Rosco Bodine]

Attachment: US3039849 Amalgam Derived Fibrous Alumina.pdf (437kB)
This file has been downloaded 779 times

watson.fawkes - 28-11-2008 at 17:49

Quote:

Originally posted by Rosco Bodine
It seems like a more complex route than working with the precursor which may come off by the tablespoonful as you watch it growing like a white snake, from the surface of some scrap very pure aluminum electrical wire, which has been amalgamated.

There is one significant advantage to the cellulose method: no need for mercury. I'll not deny that the method in the patent is useful. If you want bulk fibrous alumina, it looks just fine. On the other hand, it's not a simpler method. It requires baking the raw fibrous product at 750 - 950° C to remove (by vaporization) mercury-oxide compounds. And the initial reaction temperature is at 100 - 200° C, where the vapor pressure of mercury is significant. Both of these processes would require (at least for me) construction of sealed reaction vessels with mercury vapor condensers. It's not a construction effort I'd consider lightly. I'm not even going to say it's beyond the reach of a hobbyist, because I don't believe that. I do believe, however, it would have to be a pretty dedicated hobbyist.

Quote:

As for the porosity, well that can be plugged up with
sintered DTO, simultaneously in the precursor dip or subsequently as a followup coating by dips in precursor not containing the fibrous alumina additive.

With a hexagonal close-packing structure, α-alumina doesn't have the crystal structure needed to be an oxygen ion conductor. So it can be used in the metal-contact layer without problem. But tin dioxide (from what I can tell) is an ionic conductor, or at least enough of one that you'd have to worry about passivation. You'd want an oxide material that was solely an electronic conductor at this innermost layer

Quote:

Something I have wondered about as an unexplored idea is the use of magnetite nano crystals as a bi-electrode ,
embedded in the surface of a lake of DTO as tiny particulate islands.

The problem with magnetite is that it oxidizes to hematite fairly readily, and hematite isn't an ionic conductor. Magnetite was tried in SOFC's and failed by reason of short lifetimes. You might hark back to ceria as your island material, since it's stable and both an electronic and ionic conductor, so it should have all the catalytic effect you're after.

Amalgamated Aluminum at ordinary conditions

Rosco Bodine - 28-11-2008 at 18:55

Cobalt doping of the gamma alumina resulting after pyrolysis will result in cobalt aluminate spinel which is conductive, and anyway this fibrous alumina material is not expected to be more than 5%-10% or so by weight of the coating overall oxides , so it's conductivity isn't so much any issue anyway, even if it should be inert, which isn't very likely since the matrix of the fibrous alumina will be filled with conductive materials along with some expected compounding being involved for the fibrous alumina itself.

As for the patent process , it is only illustrative of the general idea implemented on an industrial scale. For a lab scale I had more in mind simply laying pieces of amalgamated 3mm solid Al wire on a fiberglass screen, and shaking the the fibrous alumina effluent through the screen occasionally for its collection in a tray below, using something like one of those plastic boxes used for storage containers for sweaters for example.

thanks to solo for the attached article

Attachment: Synthesis of alumina nanofibers by a mercury-mediated method.pdf (1.3MB)
This file has been downloaded 1286 times

watson.fawkes - 29-11-2008 at 00:44

What you need at an innermost layer is electronic conductivity with the absence of ionic (oxygen) conductivity. Since that layer, in this discussion, contains at least two substances, we have to ensure that at least one conducts electronically and has a continuous path and that none with a continuous path conduct ionically. That was why I pointed out that the alumina isn't conductive. Also, the suggestion of a cobalt+aluminum spinel seems workable.

Of the two steps in the patent process, the first is surely the lesser problematic. You could get some fibrous alumina, admittedly contaminated with a bit of mercury, pretty easily and exhaust through a fume hood. The bake-out, though, that remains a problem.

It's an interesting article, although their earlier reference is from 1991, not 1904 when the original fibrous alumina work was done by Wislicenus.

commercial availability

Rosco Bodine - 29-11-2008 at 08:54

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.

Swede - 30-11-2008 at 06:21

Don't get me wrong, I would truly love to experiment a bit with boehmite aluminum. The problem for the garage chemist is the sourcing. Yes, it can certainly be made, but I would much - MUCH - rather find some outfit that has a "2.5 kg Boehmite ----- Add To Cart " setup. I'd rather spend the time on the doping and testing of the resultant anode than in the preparation of the boehmite itself. I requested a sample from one of the companies (BASF) but they haven't even emailed back. I doubt I'll ever hear from them.

The entire micro-fiber aspect of it reminds me of anodizing... it is the hollow tubules of aluminum oxide on a freshly anodized Al surface that take the dyes so well.

I need to educate myself a bit more on this phenomenon.

Rosco Bodine - 30-11-2008 at 08:09

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]

Swede - 2-12-2008 at 09:20

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?

tentacles - 2-12-2008 at 10:30

You could sheathe a heating element (like a hot water heater element or similar) in a piece of copper pipe and use the pipe as part of your cathode arrangement. Fill the pipe with antifreeze or similar, cap the bottom (use lead solder) good to go. Most are even pipe fitting threaded.

My latest plating attempt rather spectacularly failed when I went to put the beta PbO2 over. I think this bath needs to be reconstituted, I've had problems plating from the same bath too soon before. So anyways, I filtered the hot solution, and now I'm going to evaporate it down, chill and salvage the lead nitrate crystals. I'm thinking of either buying the chemsavers 10kg lead nitrate package, or buying some calcium nitrate and a bunch of copper sulfate. Both are about the same price, but the lead nitrate is disctinctly less versatile.

watson.fawkes - 2-12-2008 at 13:47

Quote:

Originally posted by Swede
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?

Glass. For the very cheap, use an aquarium heater. You can find them easily in 300W capacities. You'll have to modify it, since their internal thermostats limit them not to kill fish. The one I've got on the bench right now also appears to have a thermal cutout fuse (I doubt it's resettable) at 70° C. So take out all those guts and just use the heating element and its ceramic support. For the initial heat-up, should you become impatient, get a second one and put it on a timer.

Swede - 2-12-2008 at 14:45

Quote:

Originally posted by tentacles
You could sheathe a heating element (like a hot water heater element or similar) in a piece of copper pipe and use the pipe as part of your cathode arrangement. Fill the pipe with antifreeze or similar, cap the bottom (use lead solder) good to go. Most are even pipe fitting threaded.

My latest plating attempt rather spectacularly failed when I went to put the beta PbO2 over. I think this bath needs to be reconstituted, I've had problems plating from the same bath too soon before. So anyways, I filtered the hot solution, and now I'm going to evaporate it down, chill and salvage the lead nitrate crystals. I'm thinking of either buying the chemsavers 10kg lead nitrate package, or buying some calcium nitrate and a bunch of copper sulfate. Both are about the same price, but the lead nitrate is disctinctly less versatile.

Sorry to hear the follow-up beta plating went bad on you.

As for your heater suggestion - that is an excellent idea. How about an oil (mineral oil) to transfer the heat? MgO powder, or some other refractory powder (like a very fine grog), carefully packed around the element, would be even better, and incapable of boiling, expanding, etc.

WF, I've thought about messing with a 300W or so fish heater, but it seems all they sell these days are the submersibles, and the ones I've examined look very well sealed. Just how do you get them open without damage?

watson.fawkes - 2-12-2008 at 14:52

Quote:

Originally posted by Swede
I've thought about messing with a 300W or so fish heater, but it seems all they sell these days are the submersibles, and the ones I've examined look very well sealed. Just how do you get them open without damage?

The one I've got (bought retail) had the molded-plastic equivalent of a rubber stopper. There are seven (yes, 7) sealing flanges, so it's in there pretty sturdily, but it's just a press-fit, not glued. A couple of minutes of twisting and wiggling got it out. If you're planning on rewiring the thing anyway, I'd imagine an old-fashioned corkscrew would make a fine handle. I took the long way the first time because I didn't know what was in it.

Swede - 5-12-2008 at 08:08

WF and others, thank you for your excellent suggestions on how to heat this plating bath.

I've done a bit more reading on industrial-type heaters in general. One of the more promising is a variety called a "cartridge heater" which are inserted into bored holes in molds... they come in a wide variety of wattages and voltages.

Cartridge heaters come in two flavors, low watt density, and high watt density. The low watt density types are sheathed in 304SS, not good for this process due to Fe ions. The high watt density types have the incoloy sheath, and come in a huge variety of sizes, voltages, and wattages, and aren't that expensive, maybe $30 for a 500 watt heater, 120V. Incoloy is a metal acknowledged as compatible with nitric acid processes.

I bought one from MSC...

http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=00000007753612...

That link should bring up what I bought... item #00364281 It says "backordered" because I got the last one, but there are dozens just like it. When it arrives, I'll inspect it and if it is readily submersible, then it's good to go as-is. If this style of heater is NOT readily submersible (obviously to a point; wire end remains dry) then I'll encase it in Cu as Tentacles suggested, and then we could go with SS-sheathed cartridge heaters. You could have several wattages on hand, but one Cu pipe; drop in whatever heater is appropriate for the process bath, and fire it up. Circulation will definitely be necessary for a truly accurate system, but for now I'm hoping my spinning anode will do the job.

My order from Omega arrived, got the temp controller, SS relay, and PT-100 RTD's encased in PTFE. I'll put it all together today and see how it works. I hate programming those process controllers... they're usually pretty cryptic and hard to use.

[Edited on 5-12-2008 by Swede]

Rosco Bodine - 5-12-2008 at 14:10

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]

Swede - 5-12-2008 at 17:15

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.

Rosco Bodine - 5-12-2008 at 17:59

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.

Swede - 6-12-2008 at 06:24

The thermocouples and RTD's that Omega sells are definitely not cheap, but from what I have seen, they are top shelf items, quality-wise. I know that Omega doesn't manufacture the stuff, they simply gather product lines from other makers and slap an "omega" label on them, but I have never failed to be pleased with what I've purchased from them. I could have assembled the components for a temperature controller bath from eBay for probably 60% of the cost, but the convenience was worth it... plus, the stuff is new. I am always leery of controllers and other electronics off eBay unless listed as NIB.

Odd, I thought I knew my Ohm's law, but you are correct, the wattage decreases by a factor of 4 when the voltage is cut in half. Here's a handy calculator page.

A lower watt density is quite desireable in a plating bath from what I've read. Think of it this way... you can have 1000 watts distributed along a heater line in a long coil at the bottom of a tank, giving you a nice, even heat. Or, you can package that same kilowatt in a unit the size of a pen, and you'll have a localized boiling spot, while the rest of the bath received little heat, unless the circulation is very aggressive.

A very simple heating rig (uncontrolled) can be set up with a Variac and one of these cartridge heaters encased in Cu. Dial the voltage needed to bring the bath to the temp desired. A little trial and error, and you can simply place a small tick on the variac dial for a given bath setup. Just be sure your variac can handle the wattage output of the heater.

[Edited on 6-12-2008 by Swede]

dann2 - 7-12-2008 at 18:24

Hello

If you decide to operate the tanks temperature control 'open loop' then lamp dimmers can sometimes substitute instead of Variacs as the load is resistive and not too high of a wattage. Available OTC and not expensive. Insulation wrapped around tank will help a small heater to heat tank hot enough and keep it insulated from external temp. fluctuations.

I attach a document I came accross on possible Perchlorate anodes from long time ago. Not much use to us I don't think.
(BTW, If anyone asks you did not get it from me)

Dannn2

[Edited on 8-12-2008 by dann2]

Attachment: Anodes for Perchlorate.pdf (2MB)
This file has been downloaded 732 times

Swede - 8-12-2008 at 17:34

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...

Swede - 10-12-2008 at 13:42

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.

tentacles - 10-12-2008 at 14:42

Swede: If it's anything like copper nitrate, it might be forming a ligand with the water.. Did you see any red/yellow gas over the hot salt, or in the furnace? I got some copper nitrate to the point of being a gooey mass, it was like a semi-liquid puck at room temp. You pretty much just stop when NO2 starts evolving - that's as dry as you're going to get it.

Do you have a buchner funnel and vacuum flask? If not, I HIGHLY recommend getting one. Absolutely invaluable, either a vacuum filtration setup or a pressure filter. You could fabricate either one out of random stuff, though. IE make a vacuum adaptor for a glass carboy and just have a hose going to nested buckets or some arrangement providing the filtration aspect.

Rosco Bodine - 10-12-2008 at 16:26

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]

Swede - 11-12-2008 at 08:46

Thanks, gentlemen. The Nickel Nitrate was more of an oddity than anything else. I knew there'd be people who would have an insight.

I ran an H2O test with the plating rig and heater commbination. I attached an old Ti mesh cathode to the rotating anode arm, and fired everything up. The heater, and the cartridge inserts, worked perfectly, and a 500 watt, 120V heater encased in copper JUST approached boiling, in the sense that the water surrounding the Cu tube was close to, but did not actually boil. Temp came right up and stabilized nicely.

Bad part. Bubbles formed, even with no electricity. Rotation kicked off the larger, but tapping on the boom arm, and forcing a bit of vibration worked better, so I would conclude that vibration is a superior method to eliminate bubble formation. Fortunately, I have a lot of room on the boom arm, and am going to attach a vibrator, so I will have the option of switched rotation, vibration, or both.

An ohmmeter connected between the bath, and the anode connector, showed good continuity through the structure and especially the carbon brush. Interestingly, turning ON the rotation REDUCED resistance. It was almost as if the brush is in a superior, preferred state when the system is rotating.

watson.fawkes - 11-12-2008 at 10:43

Quote:

Originally posted by Swede
Interestingly, turning ON the rotation REDUCED resistance. It was almost as if the brush is in a superior, preferred state when the system is rotating.

Think about the difference between static and dynamic coefficients of friction. I suspect there's a connection, although it's not immediately apparent to me what it might be at the nano-level.

chief - 11-12-2008 at 20:00

Platinum is used in sparc-plugs; maybe that could be some source for electrodes ? :

http://staging.platinum.pncl.co.uk/uploaded_files/Pt%202006/...

Rosco Bodine - 11-12-2008 at 20:10

Please indulge my off topic diva break, this is too beautiful to go unlinked and worth the listen

http://www.youtube.com/watch?v=a69KFAdUhIk&feature=relat...

http://www.youtube.com/watch?v=XizWzGkBjow&feature=relat... (with lyrics)

http://www.youtube.com/watch?v=O-19fSeKcXs&feature=relat... (with kisses)

and of course with love

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

Swede - 12-12-2008 at 13:04

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.

Swede - 12-12-2008 at 14:38

I forgot to add in the previous post... I mentioned that I have been talking with a guy who can hook me up with some very pure boehmite for experimentation, but he needs further detail. Perhaps Roscoe can help with some of the data he's looking for. He's asking for a rough crystallite size. They stock/produce 5 nm to 60nm, with a pore volume ranging between 0.4 to 1.2 ml/g. He's a really nice guy who is bending over backwards to help me out here.

I'm thinking a moderate to larger pore volume in a smaller crystallite size would be ideal, so long as they are not mutually exclusive.

Quote:

We also make calcined aluminas if you are looking for gamma or delta alumina and also we have dispersible aluminas whnich are fully dispersible in aqueous or mildly acidic media

Suggestions?

Rosco Bodine - 12-12-2008 at 17:08

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]

tentacles - 13-12-2008 at 09:58

I got that Ti mesh material today for cathodes - I'd like you fellas to put an eyeball on this and tell me what you think...

http://pyrobin.com/files/sdc10065.jpg

I took a picture of a section where some of the coating had rubbed off due to poor packing methodology. This is a dead ringer for MMO mesh, and I got a crapton of this stuff, dirt cheap. Specifically, I paid about $30 for 3 3x30" (with a 1" bent portion) strips. The guy is still selling some on ebay, off and on.

12AX7 - 13-12-2008 at 12:52

Put voltage to it and see if it works!

jpsmith123 - 17-12-2008 at 10:51

Dann2 thanks for the interesting paper (but now how do I get rid of the annoying black helicopters that have been harassing me since I downloaded it?).

Anyway, what I found very interesting, was the inconsistent results regarding the tests with cold-rolled steel. I wonder why did 123-57c experience such limited corrosion compared to 154-7a and 154-11-4, when they were all just plain untreated cold rolled steel?

Unfortunately they didn't say whether or not 123-57c made any perchlorate, but if it did, I would say that the result was promising.

Swede - 18-12-2008 at 09:08

Update - ready to plate. 11 kg lead nitrate on hand, PbO, Pb sheet, K Na Tartrate, and all the necessary gadgets.

Ever since Roscoe mentioned a boehmite or similar coating/catalyst carrier, I have been in contact with a salesman from an excellent company, who is helping me a bit in selection of a boehmite that might be suitable for this process. We've narrowed it down - sample almost inbound.

He sent me an interesting PDF file with info and data on dispersible aluminas. I have posted it to my web site for download. I have not read it, just glanced at it, but it looks excellent. Enjoy:

Boehmite dispersion and rheology brochure

garage chemist - 18-12-2008 at 10:56

What's wrong with "alumina hydrate" from pottery supply shops?
I got me 2kg of this, it was EUR 2,95 a kg. It's a very fine, soft, heavy white powder. It evolves lots of water vapor and turns into a "fluidized bed" at ca. 300°C.

Rosco Bodine - 18-12-2008 at 20:47

The type of alumina we were curious may have value is a nano structural whisker, a fiber form of material which can act as a reenforcing material and adhesive in pyrolytically formed oxide coatings for anodes. They use the stuff commercially in bonding the catalyst oxides to the honeycomb ceramic substrate in catalytic converters,
to produce an extremely tenacious and durable coating.

It just seemed natural to see if it would similarly be of benefit in making baked MMO coatings on anodes more
durable as well. But it is a very specific physical form
of alumina which is useful, as only this whisker form
has the necessary strength as a reenforcing fiber.
The stuff is also used as a filler in polymers and paints,
and for thermoset gluing teflon to glass and metal substrates. It is also used as a reenforcing fiber in
strengthening refractory ceramics.

[Edited on 18-12-2008 by Rosco Bodine]

Swede - 19-12-2008 at 08:13

What I find very interesting is the "pore size". A typical Boehmite alumina has a pore volume of 1.4ml per gram, meaning it can capture and carry significant catalytic materials. If it sticks, if the catalysts adequately conduct, it could be a player.

And it's free. Can't hurt to play with it!

Swede - 21-12-2008 at 14:08

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! :cool:

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.

watson.fawkes - 21-12-2008 at 15:43

Quote:

Originally posted by Swede
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 [...]
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.

Sounds like a good idea. Go with plain water and surfactant, then rinse with plain water. I don't see any advantage to nitric acid; it would just remove oxide coating without contributing anything particular to surface characteristics. Using your plating bath would be fine, but unnecessary and requiring more cleanup.

dann2 - 21-12-2008 at 18:46

Hello Folks,

Quote:

Originally posted by Swede
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?

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

dann2 - 21-12-2008 at 19:02

Quote:

Originally posted by jpsmith123
Dann2 thanks for the interesting paper (but now how do I get rid of the annoying black helicopters that have been harassing me since I downloaded it?).

Anyway, what I found very interesting, was the inconsistent results regarding the tests with cold-rolled steel. I wonder why did 123-57c experience such limited corrosion compared to 154-7a and 154-11-4, when they were all just plain untreated cold rolled steel?

FIRSTLY, about the helicopters. Did you try pegging you shoes at them? Or a welly (with a brick in it!!).

I did not get time to read/study the paper. I just can't see Steel making Perk.
I did notice that they got Magnetite to melt at about 1000C by adding some other Oxides. 1000C is more easily done than 1500C (pure Magnetite). It's not a great Anode material though.

Sorry about double post.
Dann2

[Edited on 22-12-2008 by dann2]

Rosco Bodine - 21-12-2008 at 20:59

I'll go out on a limb here and suggest something untried and unreported which might make an interesting "primer-activator-bonding agent" over the MMO as a possible sealant and adhesion enhancing strategy for the electrodeposited PbO2.

After you have baked your spinel interface and MMO coating , maybe dip the anode into a Bi / Sn Pytlewski polymer and then simply dry it, or only dry the final coat
if earlier coats of the polymer have been baked. Then put the anode into the plating bath and apply the PbO2.

Swede - 22-12-2008 at 08:50

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

Dann2, the patent that describes cathode current densities at 2X to 3X anode is 2,945,791, Gibson, who plated graphite. He went on in patent 3,463,707 with further refinements. To me, the most useful has been 4,038,170, Rhees. He goes into great detail on acidic bath plating with added Bi salts (improves efficiency) and Ni nitrate, for a finer grain, which I feel is very important for both adhesion and protection of the substrate.

For my initial experiments, I am going to start with an acid plate setup. I understand the problems of the electrolyte getting at the Ti and forming non-conducting oxides. But unless the guys in these patents are flat-out lying, the plating quality can be such that (hopefully) the chlorate electrolytes simply cannot reach the Ti. That means a coating of adequate thickness, fine grain, and excellent coverage and adhesion, must be executed.

I haven't plated a single molecule yet, but I'm hopeful. I'm going to start with the MMO. For the cathode, given the current density question, I am going to use the Cu-encapsulated immersion heaters as cathodes... the surface area should be close.

FWIW I took a scrap of MMO mesh and immersed it in concentrated nitric, with no effect whatsoever that I could see, although the nitric was a bit old and probably not the strongest.

The other problem is the use of surfactants. They may be an important key in getting a good plate, but the patents definitely describe the breakdown of the surfactant molecules in a highly acidic bath... as it breaks down, the bath is rendered ineffective. This would no doubt suck if 4 kg lead nitrate is ruined in this manner, so keeping the acid concentration on the low end of the acceptable range might be a good idea. The offending surfactant fragments CAN be removed with amyl alcohol and a sep funnel (or decant) once the bath is neutralized, so there is a way to rescue a polluted lead nitrate bath.

If this works, and I gain some experience, it would be an awesome thing to plate pure Ti successfully and have it perform in a chlorate cell.

Swede - 22-12-2008 at 08:57

Roscoe, I am interested in all forms of this process, and I appreciate your suggestions. My chemistry is not strong anymore, and I need to research some of what you are saying before I can even comment on it! It's a bit above me. But any sort of conductive surface prep over Ti that would help PbO2 adhere would be nothing but good, and would be an interesting field of experimentation all by itself. The experimental process wouldn't be difficult... prepare a few mini-anodes, with the variable being surface prep, then either mechanically test the adhesion, or better yet prepare small, identical (per)chlorate cells and see how they do, using identical currents and electrolyte concentrations.

I do have the boehmite guy in correspondence, and hopefully he'll come through for me. That would be fun to play with. Have to figure out what sort of catalyst could fill those pores, and the best way to create a coating with the colloidal boehmite/catalyst that will adhere to Ti or some other suitable metal.

Rosco Bodine - 22-12-2008 at 18:27

Quote:

Originally posted by Swede
Roscoe, I am interested in all forms of this process, and I appreciate your suggestions. My chemistry is not strong anymore, and I need to research some of what you are saying before I can even comment on it! It's a bit above me.

Don't sell yourself short there. It's the same effect achieved with the Pytlewski polymer as is gotten with the fibrous alumina in terms of the electrostatic effect which makes it a
"wetting agent" that sticks even to teflon as an adherent film
residue after drying alone. The firing of the material in place
reverses the electrostatic charge for the completely dehydrated oxides that result , so the new hydrated material
sticks by electrostatic attraction to the oxide or different oxides of underlying coatings, or overcoatings as the case may be. The unfired Pytlewski film should therefore act as
an indigenous "wetting agent" for the MMO and also likely attract the electrodepositied PbO2, acting like a glue between the two. If this works like I think it might, then
it might eliminate the need for a surfactant in the plating bath, and it might also act as an oxygen barrier. I'm not really sure if the conductivity is there and good enough for the unfired film of Pytlewski polymer, but I suspect it is probably okay, only an experiment would tell for sure.

Quote:

But any sort of conductive surface prep over Ti that would help PbO2 adhere would be nothing but good, and would be an interesting field of experimentation all by itself. The experimental process wouldn't be difficult... prepare a few mini-anodes, with the variable being surface prep, then either mechanically test the adhesion, or better yet prepare small, identical (per)chlorate cells and see how they do, using identical currents and electrolyte concentrations.

I do have the boehmite guy in correspondence, and hopefully he'll come through for me. That would be fun to play with. Have to figure out what sort of catalyst could fill those pores, and the best way to create a coating with the colloidal boehmite/catalyst that will adhere to Ti or some other suitable metal.

I'll have to go back and compare again the parallel for
the hydrated boehmite and Pytlewski polymer materials again, but I think I made the correct observation on the
similar properties for those materials in terms of their
usefulness as "wetting agents". These two materials
act as sort of a molecular scale "electrostatic powder coating"
which settles onto certain surfaces like a magnet and doesn't come off, having a natural adhesion. It would seem like a candidate material to use as a carrier for a dopant for an interface film also on a baked coated Ti substrate, where
you use a Pytlewski polymer having the desired dopant such as cobalt, or bismuth, or perhaps vanadium, ect. in the polymer, dry the film on the substrate, and then bake it.
Multiple layers should stick like glue to the previously applied layers below, since the electrostatic charge reverses for the pyrolyzed oxides material, with respect to the wet or merely dried on freshly applied material. I suppose there is a sort of covalent cross linkage between the "active" polymer and the heat depolymerized oxide, or similar oxide. If it works like I am thinking, the stuff would literally be like epoxy in terms of adhesion, it would be there to stay, married to the
surface on a molecular level.

[Edited on 22-12-2008 by Rosco Bodine]

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