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Low cost conductive epoxy?

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cduma

Sun Aug 16 2009, 05:47PM

Registered Member #1822 Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300

Great post! This not much of a bump since its already the top post.

Bored Chemist

Sun Aug 16 2009, 06:46PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

I can't get the two references to load so I can't comment on the details but I do wonder if you have thought carefully about mixing a strong oxidant with a fuel then heating it.

Bjørn

Sun Aug 16 2009, 08:44PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

I fixed the links, except the second one that is too complicated for the forum parser. Copy and paste it into the address line of your browser if it does not work.

IntraWinding

Mon Aug 17 2009, 01:52AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

I've added a note to my original post about accessing the links manually since there does seem to be a problem with at least one of them.

Thanks for the warning about heating an oxidiser and fuel - I was forgetting, Silver Nitrate is a 'Nitrate' as well as a Silver compound!

The heating of the mixture is described in the paper "Preparation of silver powder through glycerol process" thus:

The dissolution of silver nitrate completed at a temperature of 70Â°C. The blackish colour of the solution may be attributed to the nucleation of colloidal silver particles which during heating grows to form well crystalline silver powder. The precipitation of silver from the solution started at 140Â°C and went to completion at 175Â°C. This was followed by vigorous boiling of the solution at the same temperature.

And apparently this should take about an hour, so by slowly raising the temperature to 175Â°C the Silver Nitrate decomposes with the precipitation of silver, which sounds like a step in the direction of safety, but I wonder what happens to the 'Nitrate'. Even more scary than just having a mix of oxidiser and fuel is that it's a mixture of Glycerol and Nitrate - although presumably there's no chance of if forming the trinitrate, especially at that temperature

The 'vigorous boiling' that takes place at 175Â°C, well below the boiling point of Glycerol (290Â°C), sounds like maybe the nitrate is decomposing some glycerol at a controlled rate, perhaps releasing water that boils off vigorously.
I guess I'll have to make sure the mixture is kept well clear of any ignition sources, avoid adding any third ingredient just in case it has an unexpected effect, and keep clear of it just in case it does flare up (or worse). I'll probably take some samples and try setting fire to them in another room to get an idea of how volatile the mix is.
Hopefully, if this process was extremely hazardous, the paper describing it would have mentioned it, but at least until familiarity breeds contempt, I'll play it safe

The Glycerol's on order...

MinorityCarrier

Mon Aug 17 2009, 05:17AM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

Oops, just found out I've been logged on all weekend.

A word of caution with Silver Nitrate. You may already know this, but Silver Nitrate reactes with protein, it will stain your skin dark brown. This stain can't be washed off, is not removable except by abraision of the skin. Handle with gloves, don't touch your face, etc.

Bored Chemist

Mon Aug 17 2009, 05:28PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

It's an interesting reaction. It's only "safe" because there's lots of glycerol there to act as a heat sink.
It will probably spatter the solution about the place so make sure that you do this somewhere where little black spots will go with the decor.

There's a good chance that you will get NO and NO2 which are not nice too.
You might want to start at the "lots of glycerol and not much silver nitrate" end of the spectrum.

IntraWinding

Tue Aug 18 2009, 10:55AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

I'll use an oversized flask fitted with a splash head and air condenser to hopefully remove spray from the vapour. I'll use plenty of ventilation and be prepared for overly vigorous reactions. There'll be a large bucket of water in a sensible place just in case.

The last time I used Silver Nitrate I think I found stains could be removed from work surfaces with a few applications of bleach by the way, but prevention is definitely better than the cure.

Sulaiman

Tue Aug 18 2009, 11:55AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

To more closely match the characteristics of a Sony LiPo battery
you could bubble acetylene gas through a silver nitrate solution
and use the precipitate mixed with epoxy etc.
Doesn't conduct much at all, but it will give that LiPo energy discharge effect ;)

HV Enthusiast

Tue Aug 18 2009, 04:39PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Just a comment in regards to this thread.

IMHO, i feel the approach taken here is both overly complicated and overkill for the given application. I wouldn't say otherwise, except one of the criteria in your original inquiry was that the solution be "low cost", in which case based on the labor you are spending with this approach as well as the materials, this is probably going to be one of the most expensive epoxies on the planet.

I realize you want to have some fun with this, but just need to keep in mind that in engineering, the most complex solution is typically not the best solution.

If it was me, i just put those batteries together and use some tape wrapped around them to secure them. Probably be much more reliable too then relying on an unproven exotic homemade epoxy.

Just my $0.02.

IntraWinding

Wed Aug 19 2009, 03:20PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Hi Dr. GigaVolt, I totally understand that point of view too!

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