Highest dielectric strength known: Pyrolytic Boron Nitride (PBN)

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MARK-HARRISS
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Re: Highest dielectric strength known: Pyrolytic Boron Nitride (PBN)

Post by MARK-HARRISS » Fri Aug 05, 2005 8:55 am

I remember some experiments dissolving powdered glass into distilled
water to show how good a solvent it is. I can't help but speculate if there's
some additives for water along with say carbon or graphite plates and as
Dave mentioned, a chiller and deioniser..........Hang on, when I used to
test deionised water for a certain type of autoclave with a conductivity
meter, one of the best performing waters turned out to be carbon
filtered tapwater from the local battery shop. Hmm I could have a
frozen cap in the freezer with graphite and activated carbon plates!.

Hmmm and with the massive surface area of activated carbon, I should get some decent plate area.....possibly.

Regards
Mark

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Re: Highest dielectric strength known: Pyrolytic Boron Nitride (PBN)

Post by DaveC » Fri Aug 05, 2005 7:26 pm

I think the activated carbon filter is a great way to remove volatiles, organics and ions from water.

Incidentally, activated carbon is also used to purify silicone dielectric fluids, and either this or activated alumina, silica gel, or the molecular sieve desiccant materials will greatly purify, dehydrate and lower conductivity of transformer oils.

You can get an order of magnitude estimate of the surface area increase by measuring the capacitance, (AC is probably better here than DC which has galvanic issues.). Then calcuate the capacitance using the surface determined from the dimensions, and permitivity of water (81). The ratio of measured to calculated is roughly the surface area enhancement factor.

The one important unknown in this is the degree to which gas films occur. A gas layer could be nearly any thickness at all. Since it is in series with the water dielectric, a Maxwell-Wagner two capacitance layer capacitor forms. The water has a high dielectric constant but large thickness, the dielectric constant of the gas film (Er ~1.00) is low, but the thickness could be very small, so results might be all over the place... unless the water is first degassed.

Ahh... the joys of experimental science.

Dave Cooper

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Re: Dieletrics and Townsend Brown's "bentonite"

Post by Paul_Schatzkin » Sat Aug 06, 2005 1:48 pm

Hey guys, remember me?

I'm just going to chime in here with one quick note re: dielectrics.

Townsend Brown was apparently preoccuppied with a substance called "bentonite" which as a very high "k" factor. Anybody ever heard of Bentonite?

Speaking of Brown... I have been off on a very long and arduous journey trying to make sense of his life, which is more or less why I have not been contributing much in this space. I have been monitoring some of the discussions and, as always, am pleased to see a rich dialog taking place.

But I have to tell you, on some level, trying to understand Townsend Brown's life/work has pretty much challenged everything I've ever believed about anything, and it's going to take some time to digest. I'm no closer now to writing an actual book than I was when I first heard about the guy, which is now more than three years ago.

Hopefully soon I'll wrap my head around enough of what I've been through -- particularly in the past year -- to make a meaningful post here somewhere.

Mostly I just wanted to let y'all know I'm still alive, and just coming up for a gulp of fresh air...

--PS
Paul Schatzkin, aka "The Perfesser" – Founder and Host of Fusor.net
Author of The Boy Who Invented Television - http://farnovision.com/book.html
"Fusion is not 20 years in the future; it is 50 years in the past and we missed it."

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Re: Dieletrics and Townsend Brown's "bentonite"

Post by JohnCuthbert » Sat Aug 06, 2005 8:09 pm

Bentonite is a clay-like mineral, used among other things for fining wines. This means that you can get it from home-brew shops if you want to experiment.
The other thing I wanted to pint out is tht even totally pure water conducts fairly well and so you can only use it for capacitors that get charged and emptied quickly. How you purify it, and with what doesn't matter.
BTW, liquid hydrogen cyanide has a higher dielectric constant than water, but it isn't nice to work with. Acetonitrile (methyl cyanide) might be interesting to try.

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Re: Dieletrics and Townsend Brown's "bentonite"

Post by Richard Hester » Sat Aug 06, 2005 10:06 pm

In addition to its endearing poisonous qualities, HCN poses the same explosion hazard as acetylene. Acetylene is prone to explosive polymerization due to its labile triple C-C bond. Acetylene tanks do not contain the pure compressed gas - instead, it is dissolved in acetone entrained in diatomaceous earth. HCN is shipped in liquid form with an inhibitor agent added to prevent explosive polymerization. The inhibitor is suppoedly good for only 90 days or so, then you have to ship the remaining HCN back to the manufacturer, where they burn it to dispose of it.

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Re: Dieletrics and Townsend Brown's "bentonite"

Post by MARK-HARRISS » Sun Aug 07, 2005 1:11 am

Hi Paul, Good to hear from you. Sounds like you may have quite a story to tell once you sift through all the information.

Regards
Mark H

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Re: Highest dielectric strength known: Pyrolytic Boron Nitride (PBN)

Post by MARK-HARRISS » Sun Aug 07, 2005 1:26 am

I found a reference to a activated carbon "supercap" in the RadioShack
Science Projects notebook cat. No. 62-5018 by Forrest M Mims on page
13. I knew I'd seen the idea before somewhere: Forrest gets 1.2V breakdown
per sheet of activated carbon aquarium filter with lemon juice
electrolyte and a stack of 6 sheets to form His cap.

I'll have to give this idea a try sometime and report back the results.
Then maybe try some bentonite as well.

That's a great idea to add some dessicant to transformer oils, Dave
I'll try a packet in some of my HV projects as well, sealed and tied
down out of the way though silica would be better than carbon for
this application.

Regards
Mark H

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Pyrolytic Boron Nitride thread and note on insulating oil maintenance

Post by Verp » Sun Aug 07, 2005 1:56 am

As far as getting better performance out of oil through routine maintenance, I recommend this web site; http://www.wapa.gov/rm/psmmCHAP-10.pdf . (If you need a source of DBPC, also known as BHT, there is http://www.generalwax.com/p___P0295086.html .)

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Re: Pyrolytic Boron Nitride thread and note on insulating oil maintenance

Post by MARK-HARRISS » Sun Aug 07, 2005 7:49 am

Thanks rod, I have a copy now in my library. I recall someone also posted
a similar document about adding preservatives to oil also. I'll have to see
if I can find a copy of that too.

Mark H

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Re: Pyrolytic Boron Nitride thread and note on insulating oil maintenance

Post by Richard Hull » Mon Aug 08, 2005 2:01 pm

Bentonite clays are the primary ingredient in many kitty litter products and is naturally, mildly radioactive depending on the source. I have measured merely statistically arrived at levels of additional radiation in our brand of cat litter. Though I hear some are double background.

Man! I hope you guys don't injure yourselves or put out a lot of money and effort looking for the super exotic capacitor dielectric in a world that has already identified them and found them wanting or worthless on a useful scale.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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