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Rice researchers change graphene to help channel heat away from electronics.
A few nanoscale adjustments may be all that is required to make graphene-nanotube junctions excel at transferring heat, according to Rice University scientists.
The Rice lab of theoretical physicist Boris Yakobson found that putting a cone-like "chimney" between the graphene and nanotube all but eliminates a barrier that blocks heat from escaping.
Heat is transferred through phonons, quasiparticle waves that also transmit sound. The Rice theory offers a strategy to channel damaging heat away from next-generation nano-electronics.
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(Score: 4, Insightful) by jcross on Monday January 16 2017, @06:43PM
I'm not sure I would go so far as to call it a thermal diode, but convection in a chimney does have this property, tending to transfer more heat up than down. Of course once the top and bottom of the chimney are close enough in temperature, heat isn't going to flow at all, analogous to a diode with less than ~0.6 V across its terminals. This prevents the 2nd law from being violated. A chimney isn't like a diode in that if the top is a little hotter than the bottom for some reason, there will be some leakage downward no matter how low the differential, whereas a diode will require more than some specific breakdown voltage to start conducting in reverse.
(Score: 3, Insightful) by c0lo on Monday January 16 2017, @11:59PM
Mmmm... yes and no for convection. Yes, it's a macro sorta equivalent of a thermal diode. No, it's not quite an equivalent - it doesn't work in an upside down direction or in the absence of gravitation/gasses (pretty much like buoyancy doesn't work in free-fall)
On the other side, the nanochimney does not rely on a convective medium but on the difference of the speed of phonons (mechanical movements of the atoms) in the two directions. To my mind it means that if a nano-chimney is placed into a homogenous medium, the "anode" end will be, even so slightly, cooler then the "cathode" end (with phonons preferable moving from the anode to the cathode). Smells sort of a passive Maxwell demon.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford