The Lead Dioxide Anode - Microscopy
Entry posted by Swede
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With the great success of the Bucket Cell Adapter, it is finally time to put the Lead Dioxide anode to the test. At last!
From January 2009, the birthdate of this anode:
It was definitely a pretty serious effort, and I have had this anode (anode #2; #1 was crumbly and worthless due to Bismuth) hanging on a hook on the lab wall, waiting, saying "Use me! Uuuuse me!" every time I looked at it. I am so hopeful for it, that I think I have delayed its use because if it falls apart, I will probably cry. But I don't think it will. The more I handle it, the more convinced I am that it is not only going to work, it is going to work well, and show both excellent activity and durability.
The original notion (LD plating over MMO) belongs to Tentacles. I jumped into the Lead Dioxide (LD) anode game late. Experimenters had been trying to plate LD for years on various substrates, and the problem was always either mechanical, or the passivation (insulation, no more electrical flow) of the underlying metal to the LD coating. In addition, there were mechanical problems... weak or thin LD coating, crumbling, and failure under stress.
Plating over MMO appealed to me. MMO (Mixed Metal Oxide) anodes are conductive and electrochemically active salts of Ruthenium and similar coated onto titanium, and the great Trade Secret is in the prep of the titanium to accept the coating. The thought went "Why hassle with titanium prep when the MMO manufacturers have done the hard work for us?" So the above blog entry detailed the effort that went into plating LD over MMO.
The plating was not (and never will be) a trivial task. The quantity of reagents required, the size of the tank, the vibrational/rotational rig, and especially the toxicity of the brew, made for a real challenge.
The first attempt failed because the tank was loaded with Bismuth salts, based upon some earlier patents, and to put it bluntly, I spit on Bismuth. Never again. The next plating tank was larger and more conventional, and all the details are there in the previous blog. The anode that emerged was strong, heavy, and importantly fine-grained crystalline in structure, possibly due to the nickel nitrate.
Most home-plated LD anodes are shiny. They end up coated with a hard LD shell that has a poor surface area, and they generally do not work well. When my anode #2 dried, I was very excited by the apparently fine but porous grain that, under the microscope, shows a beautiful surface that I think will work well.
I plan on creating a small perchlorate tank using a transparent food container and the Bucket Cell Adapter (BCA) hardware. Normally I would advocate that a transparent tank is not necessary for most home electrolysis efforts, and I stand behind that in general, but for the first runs with this anode, I need to be able to see what is going on. I am going to make a special trip to a store that offers high-end food containers today, and set it all up with the BCA hardware. For reference purposes, I also wanted to take a few microscopy photographs that show the velvety, crystalline surface of anode #2, now called LDA2.
It's hard to take nice pictures. I have an excellent Meiji binocular microscope that is a joy to use, and every time I look through it, the image is 3D and quite breathtaking. I've tried eyepiece cameras, but the cheaper varietites do not work well, and the best pics come from a good digital camera focused through the eyepiece; plus, a bit of editing, mostly cropping the black surrounding area.
The edges of the MMO anode gathered more LD than the remainder, creating warts and bulbs that are not pretty, but in reality, they will help structurally. The fact that they grew together tells me that the possibility of electrolyte leaching under an LD edge is minimized.
Under the microscope:
And getting closer and closer:
The odd little fibers are actually cotton or paper towel fibers gathered by the anode. On a microscopic level, the anode is like velcro or sandpaper, and in fact the surface feels exactly like 400 wet/dry silicon-carbide paper. Over the months, it has collected these little fibers that are invisible to the naked eye, but show up under the microscope.
The color is not reproduced well. These pictures appear silvery, but that is due to the reflected powerful lighting used to create the photographs. The actual color is an odd gray/black that changes color based upon the angle and amount of lighting. Under higher power, you can see the individual LD crystals themselves on the surface of the anode. The anode weighs exactly 197.00 grams. After use, a further weighing should revel erosion, if any.
I feel that I have a decent grasp of the chlorate process at this point, but the next run is going to venture into unknown territory. It's too bad that chlorate, while a potent and effective oxidizer, has drawbacks that I am not totally comfortable with, and my goal (started well over a year ago) was the home-creation of potassium perchlorate of a purity that would pass muster with the most discerning pyro anywhere.
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