Longitudinal heat transfer material?

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Discussion Overview

The discussion revolves around the search for materials that exhibit excellent longitudinal heat conduction, specifically in the z-axis direction. Participants explore various materials suitable for scientific experiments, considering their thermal conductivity properties, thickness, and practical applications in thermal transfer processes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests nickel (Ni) and molybdenum (Mo) foils as potential candidates with thermal conductivities of 90 and 138 W/mk, respectively, but is seeking better options.
  • Graphite sheets are mentioned as having high thermal conductivity (1500 W/mk) but only in the xy-plane, raising concerns about their suitability for z-axis conduction.
  • Another participant proposes that if the graphite sheet is thick enough, it might be possible to rotate it to align with the heat flow, although the thickness of the sheet (25 µm) complicates this approach.
  • Some participants note that materials like copper and silver are good conductors in all directions (~400 W/(mK)), while diamond is highlighted as having superior conductivity but is costly.
  • There is a discussion about the need for materials that conduct well in the z-direction but poorly in other planes, with mica and graphite being mentioned as examples.
  • One participant describes their application involving thermal printing patterns using a laser CNC machine, emphasizing the need for a foil that transfers heat longitudinally without lateral vibration.
  • Stacking multiple strips of materials is proposed as a potential solution, though concerns about practicality and expense are raised.
  • A question is posed regarding the target resolution for the thermal transfer process, suggesting that isotropic heat conduction might suffice if the resolution is not significantly below the thickness of the material.

Areas of Agreement / Disagreement

Participants express various viewpoints on suitable materials and methods for achieving effective longitudinal heat conduction. There is no consensus on a single best solution, and multiple competing ideas and approaches remain under discussion.

Contextual Notes

Participants highlight limitations related to material thickness, alignment for optimal conductivity, and the practicality of proposed solutions, which remain unresolved.

jjoll
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hi,
I am running some scientific experiments, and I need a sheet of materials that is extremely good conductor of heat in z axis (through its thickness), I mean it is a good longitudinal heat conductor.
I have been doing some researches and some people told me Ni and Mo foils are good at 90 and 138 W/mk but I was wondering if there is something much better. I have found these graphite Sheets (http://www.tglobalthermal.com/t68-artificial-ultra-thermal-conductive-graphite-sheet.php) with 1500 W/mk but they have such conductivity in xy plane only.
I would be grateful if you can point me to the right direction. that would be great if you can show me where i can buy it too.

thanks
 
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It would help to know the (approximate) size of your heat conductor. If it is thick enough, you can try to rotate graphite to align it with your heat flow.
Is conductivity along other directions an issue? Copper and silver are very good heat conductors in all directions (~400W/(mK)). Diamond is significantly better, but extremely expensive...
 
mfb said:
It would help to know the (approximate) size of your heat conductor. If it is thick enough, you can try to rotate graphite to align it with your heat flow.
Is conductivity along other directions an issue? Copper and silver are very good heat conductors in all directions (~400W/(mK)). Diamond is significantly better, but extremely expensive...

thanks, the thickness of this graphite sheet is like 25 um, i don't think it is feasible to just flip them on the side.
 
Do you need a material that has good longitudinal (Z) conduction, but lower conduction in other planes? Most materials that I know of that have anisotropic heat transfer tend to conduct well in plane (XY) but not well out of plane (Z). Mica and Graphite come to mind.
 
jjoll said:
thanks, the thickness of this graphite sheet is like 25 um, i don't think it is feasible to just flip them on the side.
If you stack 1000 strips of them you have a few cm (not 2.5 as the stack won't be perfect) with a height determined by the width of the strip. This is probably impractical, but I can't tell if you don't say anything about the application where you need the heat conductor.
 
christopher.s said:
Do you need a material that has good longitudinal (Z) conduction, but lower conduction in other planes? Most materials that I know of that have anisotropic heat transfer tend to conduct well in plane (XY) but not well out of plane (Z). Mica and Graphite come to mind.

mfb said:
If you stack 1000 strips of them you have a few cm (not 2.5 as the stack won't be perfect) with a height determined by the width of the strip. This is probably impractical, but I can't tell if you don't say anything about the application where you need the heat conductor.

I am trying to thermally print some patterns using a laser CNC machine on some wafer samples. I don't want to apply this vertical laser beam directly on these samples. That is why I was looking for a sheet/foil that goes on top of wafer and thermally transfer the heat to the samples underneath it.

therefore yes, I need a material preferably in the form of a foil that has a very good longitudinal conduction but doesn't vibrate laterally so when laser beam hits it in a vertical fashion it just transfers that heat in a longitudinal fashion as much as possible.
It will also be helpful if anybody can point me toward a solution in which I can use same laterally conductive material to achieve something as I explained.
I already though stacking strips of graphene sheet on their side but due to the very thin nature of these sheets it seems to be a impractical and expensive.
 
What is the target resolution for this process? If it is not significantly below the thickness of a possible sheet, an isotropic heat conduction could work. Aluminium foils are available down to ~1µm thickness, so structure sizes of a micrometer or even a bit less should be fine. Assuming you can fix your foil to the surface with the required precision.
 
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