Electronics > Beginners
dielectric constant for glycerin
David Hess:
--- Quote from: LaserTazerPhaser on March 21, 2019, 05:12:46 am ---Im mainly concerned for its RF power losses. Im also considering deionized water for dielectric.
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I have tested materials for low dielectric loss by measuring their temperature rise in a microwave oven.
--- Quote from: T3sl4co1l on March 21, 2019, 12:27:36 pm ---I don't even know how you dry it -- can you dry it? Concentrated sulfuric acid or P2O5 certainly isn't going to do (dehydration, condensation reactions), and anhydrous salts will simply dissolve in it (ruling out usual suspects like CaCl2).
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Apply a vacuum after assembly?
--- Quote from: Doctorandus_P on March 21, 2019, 09:18:25 pm ---I would probably make a capacitor like this from glass plates and 2 pieces of auminimum or copper foil.
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Use glass plates that are a few cm wider than the foils to crate gaps and maybe put the whole thing in some liquid to isolate the edges further.
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It might be worth putting dabs of silicone or whatever on only the corners of the glass plates, for extra isolation.
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That is how I have done it. A wide margin around the edges of the glass plates prevents flash-over between the two sides. Corona discharge was significant with the rough cut aluminum foil but gave the capacitor a nice eery blue glow at night. The aluminum foil was attached with spray adhesive.
I spaced the plates apart and used one spring connection for each pair of facing sides. The added space aids air cooling.
LaserTazerPhaser:
Glycerin is not going to work https://www.pupman.com/listarchives/1997/november/msg00362.html
--- Quote from: Marco on March 21, 2019, 10:23:20 am ---Just use EVO.
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Whats the k value?
--- Quote from: bson on March 21, 2019, 10:36:58 pm ---How about experimenting with epoxy resins?...
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Seller replied https://www.ebay.com/itm/332870578714/ has 3.11 K value and I can add up to 10% TiO2 thus 10% of Tio2 + that compound is 14.11, still quite low.
--- Quote from: T3sl4co1l on March 21, 2019, 12:27:36 pm ---...PET (a polyester) for example, has a modest k, and reasonable enough losses...
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Many polymers dielectric strength decreases with increasing thickness.
--- Quote from: gbaddeley on March 21, 2019, 10:33:21 am ---DIY HV caps often use mineral oil, aka baby oil (with no added fragrance)
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Im considering saturating mineral oil with loads of TiO2 in a blender then removing any dissolved air with a vacuum then pouring it in the capacitor. This combination seems the most ideal, BaTiO₃ would be much better but its cost far greater.
bson:
Calcium copper titanate seems to be the material of choice. It appears to have µr on the order of 10k-250k, depending on source, grade (presumably), and temperature. TiO2 seems to have µr around 100 at room temp.
With a bit of digging... https://www.alibaba.com/product-detail/Calcium-Copper-Titanate-CCTO_60682595594.html?spm=a2700.7724857.normalList.32.7ae030a12ep29O
I'd see if I could find 1-2kg affordably, and go with that.
bson:
I'd also mix it with a resin, and determine the maximum ratio empirically. It doesn't need to retain epoxy-like adhesion or strength, just keep together reliably as a solid block under normal use. A liquid such as oil always presents a potential problem with particulate matter settling...
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