Horace, It occurred to me that to fabricate the thin film cathode we could use the dielectric material's parasitic conductivity, or possibly some capacitive method (using pulsed DC?), to deposit the PdD thin film directly onto the material. Incidentally, this could well be what actually happens on the clear plastic walls of the HV submitted SPAWAR cells, without anyone ever noticing because the deposit is so thin that it is transparent :-)
The cathode fabrication process, and preparation for subsequent normal operation, could go like this: 1/ Fill the cell container e.g. a test tube made of the right dielectric material (e.g. a clear plastic e.g. polycarbonate... e.g. CR-39 !) with the electrolyte we will be using for normal operation (that for PdD codeposition) 2/ Immerse the test tube into a thick walled glass container filled with salt water, aligning the levels. 3/ Immerse a grounded wire into the salt water (this connects the outside of the tube to ground) 4/ Immerse an anode wire or rod (the same we will be using for normal operation) axially into the electrolyte and connect it to a +HV wire ( the same we will be connecting later to the salt water, e.g. the +25kV wire of an old CRT). A low current will thus start leaking from +HV to ground through the electrolyte and through the dielectric tube walls, from the inside to the outside, and thus the desired PdD codeposition will occur on the inside wall of the tube. 5/ Wait for the deposit to grow to the desired thickness (monitor the total charge circulated by the HV supply to determine the deposited amount using Faraday's law of electrolysis) 6/ Then establish the connections for normal operation: connect the deposited thin film cathode to ground, the anode to a positive low voltage suitable for normal operation electrolysis, and the salt water to the +HV wire to capacitively establish the desired high electron density on the back side of the cathode as we have discussed. Hope this makes sense. Michel ----- Original Message ----- From: "Horace Heffner" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, August 02, 2007 1:17 AM Subject: Re: [Vo]:Re: Electron fugacity, deuteron fugacity, and applied fields On Aug 1, 2007, at 12:58 PM, Michel Jullian wrote: > I do not share your worries about ground potential jumping to > hundreds of kV, but it's always a good idea to run an electrical > experiment in a Faraday cage so whatever your reasons they are fine > by me. It was just an example. However, it happens here sometimes that the northern lights descend to ground or close to it. I think the ionosphere is typically .2 to .5 MeV different. Cumulus clouds sometimes induce a pretty strong ground charge too. > > Now what remains to be found is the dielectric material whose > product of dielectric constant by dielectric strength is the > highest of all dielectric materials, agreed? Yes, that maximizes charge density per power supply volt, so assuming conductivity or other things are not a problem. Optical properties, conductivity, hydrogen permeability, availability, and price might be important too. Barium titanate comes in a wide range of composites, with a dielectric constant up to 18,000, but 6000 or less is a more realistic maximum for a hot CF cell, and a dielectric strength of about 2 MV/m, less than air. I don't know about cost or availability. BaTi3 has high optical reflectivity. See: http://www.avxcorp.com/docs/techinfo/mlcmat.pdf "Class 2 high dielectric-constant materials are relatively homogeneous barium titanate formulations that have grains grown to more than 3 μm. Their high K stems from the addition of substituents with the same valences. These shift the Curie point to the room temperature region. Sr(2 +) or Zr(4 +) are often used, making peak dielectric constants as high as 18,000 available. Such materials can lose up to 50 percent of their dielectric constant at 50°C, but find general applications in computers and other commercial low-power electronic equipment requiring a limited temperature range. For “Z5U” requirements (capacitance loss of less than 56 percent at 80°C) calcium is most often added in the form of calcium zirconate. The resultant dispersion in the dielectric characteristics widens the K versus temperature curve, and controls the maximum capacitance loss at 85°C. Room temperature dielectric constants of more than 8000 are then seen. These materials also contain inhomogenuities in the form of unreacted, relatively pure, grain cores." It is interesting BaTiO3 looks a lot like co-deposited D/Pd cathode material under a SEM. It might be a very good approach to forget the laser and try to sinter a very good Pd, Ag, or Ti or some CF active metal bond with BaTiO3, and then build the cathode material from there by codeposition. Some forms of BaTiO3 are a silver composite. I wonder just how permeable BaTiO3 is to hydrogen. There are so many kinds, made from varied grain sizes, and different composites. Horace Heffner http://www.mtaonline.net/~hheffner/
