cheapest inert electrically conductive material that can be mass produced

[AK92]

Hi,

I'm currently looking for an flexible, inert and electrically conductive material that can be mass produced. Cost would be the largest issue here.

I'm thinking of either electrically conductive plastics or graphite strips. Would like some advice on this. Thank you!

 

[IRstuff]

To do what? You want wire, sheets, what? What's wrong with just copper wire? How much current does it need to conduct? How much resistance can you tolerate? Without specifying these and other constraints, how do you expect to get a practical answer?

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[AK92]

@ IRstuff

Thanks for the reply. This is to be combined with geosynthetics to set up a current passing through soil for soil improvement, hence it needs to be inert. Most metals wouldn't fit the bill as they would undergo corrosion and contaminate the soil.

Best would be some material that can be produced in thin strips.

 

[IRstuff]

Again, hoe much current? How much resistance?

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[dgallup]

Water is compatible with soil and a "good" conductor as long as it has some free ions in it which the soil will readily provide.

You are going to get stupid answers as long as you don't provide sufficient input.

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[AK92]

Sorry about the confusion.

Let's say about 3A, and a resistivity less than 10^-6. What would be the suitable materials (again, they have to be inert as they have to behave as both anodes and cathodes)

 

[IRstuff]

You've answered your own question. That resistivity is only possible with a metal. Are these electrodes permanently installed? There are sacrificial coatings that can be applied.

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[btrueblood]

"Most metals wouldn't fit the bill as they would undergo corrosion and contaminate the soil."

Sounds like a job for stainless steel.

 

[AK92]

@IRStuff and btrueblood

What about conductive polymers or graphite? Most metals would be too expensive. This has to be installed in many millions of meters, so the unit cost is particularly important. A higher resistivity would be acceptable as well, as long as it is inert and does the job.

 

[IRstuff]

How high a resistivity? You specified a value that's only achievable with metal, and now that's not required? You need to define your problem parameters and the maximum allowable resistivity. Pure graphite, which is unusable as a wire had 500 times, let me repeat, 500 times, the resistivity of copper. When combined with other materials to make a wire-like structure, it can only get worse.

This ignores issues associated with composites, including moisture absorption.

It seems to me that you are simply slinging mud and trying to see if anything sticks. This is not what I would do as an engineer. Moreover, you don't seem to have done much research for something that "has to be installed in many millions of meters." Where is your EE in this project; why isn't he doing this?

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[AK92]

Hi IRStuff

Yes, sorry I am indeed "slinging mud" to see if anything sticks. This is more as a side interest of mine to think about solutions to implement cost-effective electro-osmosis ground improvement for clays, which normally requires millions of metres of prefabricated vertical drains (which will cost a bomb if the materials are expensive to make)

I'm interested in electro-conductive polymers and perhaps doping of polymers to increase the conductivity. I recently read a research paper that used ion beams to make polymers as conductive as metals. I think this is what is currently used by some companies. So that's an option as well.

What's the issue with a composite, why would water absorption be a problem? What about graphite-metal composite, with the graphite on the surface to protect the metal from corroding? Surely that would have better conductivity properties than pure graphite as well as being non-corrosive, more ductile and robust when handling.

 

[Pud]

"Electro-conductive" polymers are nowhere near as conductive as metals. Neither are they cheap. Conductive additives (CF/SS etc) are expensive and then there is the cost of making the compound.

Contrary to popular belief, plastics are not "cheap" - what makes plastic products cheap is their "in position" price which is usually a one operation process.

e.g. General purpose PP = £1.20 /kg
PA6 = £2.20
PPA + 30%CF = £20+ per kg
LCP + 30% CF = £65+ per kg

Stainless steel approx $3.50 /Kg (I'll let you do the maths!)

If you look on say "Matweb" or similar, you will find electrically conductive plastics, are, well, really not at all...

I recently read a research paper that used ion beams to make polymers as conductive as metals.

Yeah - that sounds cheap (It also sounds like they are looking for further funding!)

Cheers

Harry



www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[AK92]

@Pud

Thanks for the info, I guess using metal with a protective layer of graphite would, for now be the best option. What do you think of using that?

 

[1gibson]

I think you are describing regular insulated wire, with some sort of clamp on conductive sleeves at intervals. If the conductive sleeve doesn't exist, design it. Start by looking at "insulation piercing wire taps."

 

[AK92]

@1gibson,

I can't have much insulation as I want very good conductivity to setup a electrochemical current through the soil. I need the "metal" to be covered by something inert (but still quite conductive) so that the metal doesn't just corrode away and reduce the system's conductivity.

 

[IRstuff]

"so that the metal doesn't just corrode away and reduce the system's conductivity"

As mentioned before, sacrificial coatings can be used to mitigate this:

http://www.substech.com/dokuwiki/doku.php?id=corrosion_protection_coatings

http://www.corrosionpedia.com/definition/993/sacrificial-coating

http://www.international-marine.com/paintguides/whatiscorrosion.pdf

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[1gibson]

So how much better is the result with continuous conductivity, vs. conductive nodes every foot or so? On a scale of "millions of meters" I find it hard to believe that you can't sacrifice a little resolution there. But that's just me trying to be practical.

Still interested to see if anyone has the perfect solution up their sleeve, but it isn't going to be cheap.

 

[AK92]

@IRstuff

Will the stuff still work if it acts as the anode and cathode in an electrochemical cell where the water has all sorts of ions?

@1gibson
It really needs to have continuous conductivity since we want to setup an uniform electrochemical current through the soil. Also, it would be best if sheets are available compared to wires.

 

[IRstuff]

"Will the stuff still work if it acts as the anode and cathode in an electrochemical cell where the water has all sorts of ions?"

You would need to take to a specialist

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