bwhite@oucsace.cs.ohiou.edu (Bill White ) (02/02/91)
I apologize in advance for cross-posting, but I have asked questions along this general theme before and gotten little or no response. Please direct all responses to me, or if you must follow up please do it in sci.electronics. Essentially I am trying to form four (4) 1 meter hemispheres (with a 10 degree "excess", making it slightly more than a hemisphere) for use in a Van de Graaff system. After investigating various technologies such as spun aluminum and explosive forming, I found them either beyond my means financially and/or beyond the abilities of our university. It was suggested I investigate electroplating. Cost for custom-production of the four hemispheres by traditional methods was quoted from $1000 up. This is more than I would like to pay. What I would like to do is take a form, 1 meter diameter, coat it with a conductive material, plate a 1/8 to 1/4 inch (sorry about mixing measurement units) thick layer of copper (yes I know that's awful thick), do some elementary forming, and then coat it with nickel and then chromium. The resulting finish *must* be smooth, though I don't really care what it looks like. The copper *must* be malleable, though if it can be annealed to make it malleable that is fine as well. One idea that popped into my head was to use an aluminized mylar spherical balloon, strike plate it in a cyanide plating solution, then finish plating the copper in an acid solution. Most of my metal plating experience, however, has been with small items using only acid solutions. If I can find a company willing to do this, at a cost I can afford, fine. If not, I would like to undertake this project using the university's facilities. Here are the questions I have: 1. Is it feasible to plate onto an aluminized mylar surface? I know that it is possible to plate onto insulating surfaces *somehow*, so I would assume that plating onto an aluminized surface would be easier from the standpoint of conductivity. 2. Does anyone know where to get spherical aluminized mylar balloons in the range of 750mm to 1m diameter? (if the answer to the above question is yes, of course) 3. Can anyone suggest any references on plating copper to a thickness of 1/8 to 1/4 inch? References on strike-plating onto aluminized surfaces? 4. I assume it would be simpler to have some company finish the nickel and chrome plating (I actually don't know if I need chrome, so long as the nickel won't corrode I could just use nickel alone). Is it practical to do this type of plating myself using University resources, or would it be easier to do this commercially? The thickness does not matter; the surface condition does. I will not be placing the hemispheres in SF6 (I can't afford it; if air breakdown is a problem I may go for dehumidifying or for some other, cheaper gas). Please respond to bwhite@oucsace.cs.ohiou.edu Thank you for your time.