Diamond substitute
 

I've read on this forum time and time again that diamond would be the best conductor to use... but as we all know, it's not cheap. Just a thought - graphite is the exact same thing as diamond just in a different form.

Has anybody ever thought about using graphite or am I completely insane? Would the texture of the graphite cause problems with the heat involved? Basically we're still dealing with Carbon.

I know that the structure of graphite is obviously different than that of diamond. Would that different structure cause graphite to "grab" the heat differently?

Maybe I'm just going out on the broken limb? Who knows. Like I said earlier, just one of those random thoughts. Thanks for any input. :shrug:

Probably be best to put this in the water cooling construction forum. have any info on the properties of this graphite and what forms it comes in? Is it easy to work with? Can it be milled drilled and not break under pressure? Water tight? Withstand 70 watts of heat without breaking down?

Just a few questions off the top of my head. Only graphite I ever used was the graphite powerder lube stuff and graphite fishing poles. :D

Re: Diamond substitute
 

You are right that graphite and diamond are different in structure. This affects the thermal conductivity completely. I will post actual values, but graphite is only good at conducting in certain directions, which is not much use for us.

8-ball

Units are cal/cm*sec*K.

Carbon (diamond) = 5.54
Carbon (graphite) = 0.80
Copper = 0.96

I have no information on whether the graphite data is with or against the grain structure.

Alchemy

It depends on how you set up the graphite. For a waterblock, it would not be very useful though, since graphite can only conduct heat along the axis parallel to the planes of carbon atoms. This is because graphite is made of flat hexagons of carbon atoms, with each atom bonded to 3 others to make large, flat planes. Heat (and electricity too, in fact) can be conducted very efficiently along those planes. However, in other directions, the bonds are extremely weak, and hardly conduct at all.

Diamond, on the other hand, is a large latice, and can conduct heat extremely well in all directions, though it can't conduct electricty because all of it's electrons are used in single bonds.

http://www.grc.nasa.gov/WWW/RT1999/6000/6712chao2.html

This might shed some light on the subject...It has a graph to show the difference between aluminum/graphite and copper/graphite. Copper still beating graphite, but if you combine graphite and copper you have a very good heat conductive composite.


Also if I might add...a little off topic but...When you heat up a graphite hockey stick to replace the blade...the heat seems to stay localized to where you are heating...it does not travel up the shaft..just seems to penetrate through one way.

Tuff

Thanks for the info :) I really didn't know which forum this belonged in... but now that you mentioned that specific forum... I feel like a dumbarse.

I figured that the structure would affect the heat transfer capabilities but I didn't know how exactly.

Once again, thanks for the input, much appreciated. :D

What about industrial diamond? the fake stuff they use for coating drills and saws.

As far as I know, its black in colour, and proably not massivly expensive, at least not compared to a block of real diamond the size of a waterblock :)

The only issue is whether it can be made in chunks of the kind of size we need, that and of course how to actually work with it.

Before anyone else posts, please browse this thread: http://forums.procooling.com/vbb/sho...hlight=diamond

Probably answer most questions.

Hey Tuff, you might want to reread that link becuase the only mention it makes of conductivity is to say how poor graphite is compared to copper. Alloyed metals virtually always conduct worse becuase of the effect of the solute on the lattice structure.

The rest of the artical just talks about phase change systems, not conduction.

Depends. Conduction ranges from half to one and a half times natural diamonds for synthetics and industrial diamonds, depending on how much you have to spend. Worst case you're looking at 3x the conductivity of copper.

Hoot at o/cforums checked it out a while back, he got a quote from a guy for a tiny peice(I think 20x20mm) was like $500, but cince he said he would do a writeup he would sell it for like $3XX. something like that... Its expencive stuff.
this is the industrial diamond I beleve.

Note: read "carbon" as "graphite-structured carbon."

To add to what I've said before:

I've never worked with strictly carbon materials, but I've worked with people who have done so, and I've learned a few things from them:

1) Their s***ty residue never, ever comes off the testing equipment we share

2) No matter what you do with it, carbon (fibers) can only be made strong in one direction (two if you make it into composites), which is the same direction(s) in which the fibers align and the direction in which heat is transferred.

How you can arrange these fibers, or any pure carbon, in a plane such that the planar carbon structures align perpendicular to the plane and still create a structure strong enough to withstand the clamping pressure, I can't imagine. You'd need some sort of crosslinking that is beyond the capabilities of all but a few scientists. Such an act would be highly published.

To reiterate, there's no way to make graphite into a material strong enough to serve as a baseplate.

/heavy Thursday drinking

Alchemy