RE: [Vo]:Remote Joule heating in Carbon nanotubes
Mark, To be a bit contrarian: this looks like bad science to me. I think it is part assumption error, and part a relic of cavity super-radiant emission (Dicke-Preparata) by nanotubes, which emission is partially focused on a good blackbody emitter. If fact most of the effect could be measurement error due to the way the nanotubes are laid down - with a preferential vector for emission (the open end of the tubes) combined with the lack of appreciation for the known nanotube anomaly with Kirchoff laws. In fact most of the error probably derives from the assumption that temperature measurement of the carbon side would be a blackbody spectra, when it is well known that Kirchoff's laws are not only violated by nanotube emission, but almost irrelevant. Plus cavity radiation - if a preferred vector is provided, can transmit photonic radiation as if it were semi-coherent (super-radiant). Since the authors never mention Dicke, or super-radiance, or cavity blackbody emission, or the known violation of Kirchoff (at least in the PR blip) this seems more like poorly done research and a premature announcement of what is already known - than good science. From: Mark Iverson FYI: http://phys.org/news/2012-04-carbon-nanotubes-weird-world-remote.html This is a new phenomenon we're observing, exclusively at the nanoscale, and it is completely contrary to our intuition and knowledge of Joule heating at larger scales-for example, in things like your toaster, says first author Kamal Baloch,
RE: [Vo]:Remote Joule heating in Carbon nanotubes
The experiments used DC current, which is why the 'remote' heating was unexpected. -m From: David Roberson [mailto:dlrober...@aol.com] Sent: Tuesday, April 10, 2012 10:39 PM To: vortex-l@eskimo.com Subject: Re: [Vo]:Remote Joule heating in Carbon nanotubes Inductive heating usually requires a time changing current in order to heat the nearby conductor. Maybe the current in this case is more like a series of quantum pulses which might have the time varying property required. A great deal of the effect would depend upon the relative magnitude of the current and thus the flow characteristics of electrons within. I assumed that the basic experiment consists of a DC current instead of AC. AC current could certainly be used to generate inductive heating. The thought occurred to me that the uncertainty principle might allow a portion of the electron current to flow within the nearby conductors effectively bypassing the nanotube. If this theory is correct then the effective size of the electrons must be such that they extend outside of the tube. Dave -Original Message- From: Jojo Jaro jth...@hotmail.com To: Vortex Vortex-l@eskimo.com Sent: Tue, Apr 10, 2012 11:22 pm Subject: [Vo]:Remote Joule heating in Carbon nanotubes Correct me if I'm wrong, but isn't this just some kind of Inductive Heating? I don't see why this would be something new.
Re: [Vo]:Remote Joule heating in Carbon nanotubes
Inductive heating is caused by magnetic coupling between the source current and the load or heated item. Resistive heating is due to the current actually flowing from the source through the load and does not require magnetic coupling. The thought process mentioned in my last sentence involves direct resistive heating and does not depend upon a changing current. In that case a DC current could generate the heating. True inductive heating requires AC current flow. Think of inductive heating as heating that occurs due to induced currents flowing through a resistive loop. The integrated time changing magnetic field that links through the loop causes a voltage to be induced. Current flows as a result of the induced voltage which generates heat as it flows through the resistive loop material. Dave -Original Message- From: MarkI-ZeroPoint zeropo...@charter.net To: vortex-l vortex-l@eskimo.com Sent: Wed, Apr 11, 2012 10:48 am Subject: RE: [Vo]:Remote Joule heating in Carbon nanotubes The experiments used DC current, which is why the ‘remote’ heating was unexpected… -m From: David Roberson [mailto:dlrober...@aol.com] Sent: Tuesday, April 10, 2012 10:39 PM To: vortex-l@eskimo.com Subject: Re: [Vo]:Remote Joule heating in Carbon nanotubes Inductive heating usually requires a time changing current in order to heat the nearby conductor. Maybe the current in this case is more like a series of quantum pulses which might have the time varying property required. A great deal of the effect would depend upon the relative magnitude of the current and thus the flow characteristics of electrons within. I assumed that the basic experiment consists of a DC current instead of AC. AC current could certainly be used to generate inductive heating. The thought occurred to me that the uncertainty principle might allow a portion of the electron current to flow within the nearby conductors effectively bypassing the nanotube. If this theory is correct then the effective size of the electrons must be such that they extend outside of the tube. Dave -Original Message- From: Jojo Jaro jth...@hotmail.com To: Vortex Vortex-l@eskimo.com Sent: Tue, Apr 10, 2012 11:22 pm Subject: [Vo]:Remote Joule heating in Carbon nanotubes Correct me if I'm wrong, but isn't this just some kind of Inductive Heating? I don't see why this would be something new.
Re: [Vo]:Remote Joule heating in Carbon nanotubes
I don't believe Inductive Heating only occurs in AC, as in Alternating. The current does not have to be alternating as in reversing directions periodically. All that is require is a time varying current, which could be Direct current, as long as it is varyinng. The important thing is the varying part and that should be enough to induce magnetic coupling on the metal substrate and induce Inductive Heating. Am I not correct? Jojo
Re: [Vo]:Remote Joule heating in Carbon nanotubes
I think we are saying the same thing. I used AC as in alternating current to specify that it must be time changing in comparison to steady flowing DC current. The requirement is that the source current must be changing in time to induce a voltage in nearby conductors. I believe that magnetic field coupling is the only method that is referred to as induction heating. It is possible to induce capacitive currents in nearby conductors as well but I do not think that process would be referred to as induction heating. Dave -Original Message- From: Jojo Jaro jth...@hotmail.com To: Vortex Vortex-l@eskimo.com Sent: Wed, Apr 11, 2012 1:29 pm Subject: Re: [Vo]:Remote Joule heating in Carbon nanotubes I don't believe Inductive Heating only occurs in AC, as in Alternating. The current does not have to be alternating as in reversing directions periodically. All that is require is a time varying current, which could be Direct current, as long as it is varyinng. The important thing is the varying part and that should be enough to induce magnetic coupling on the metal substrate and induce Inductive Heating. Am I not correct? Jojo
Re: [Vo]:Remote Joule heating in Carbon nanotubes
dare I say it? cool. harry On Tue, Apr 10, 2012 at 7:02 PM, Mark Iverson markiver...@charter.net wrote: FYI: http://phys.org/news/2012-04-carbon-nanotubes-weird-world-remote.html This is a new phenomenon we're observing, exclusively at the nanoscale, and it is completely contrary to our intuition and knowledge of Joule heating at larger scales-for example, in things like your toaster, says first author Kamal Baloch, who conducted the research while a graduate student at the University of Maryland. The nanotube's electrons are bouncing off of something, but not its atoms. Somehow, the atoms of the neighboring materials-the silicon nitride substrate-are vibrating and getting hot instead. The effect is a little bit weird, admits John Cumings, an assistant professor in the Department of Materials Science and Engineering who oversaw the research project. He and Baloch have dubbed the phenomenon remote Joule heating. An Unreal Discovery For the UMD researchers, the experience of the discovery was like what you or I might have felt, if, on a seemingly ordinary morning, we began to make breakfast, only to find certain things happening that seem to violate normal reality. The toast is burned, but the toaster is cold. The switch on the stove is set to HI and the teapot is whistling, but the burner isn't hot. Of course, Baloch, Cumings and their colleagus weren't making breakfast in a kitchen, but running experiments in an electron microscopy facility at the A. James Clark School of Engineering at the University of Maryland. They ran their experiments over and over, and the result was always the same: when they passed an electrical current through a carbon nanotube, the substrate below it grew hot enough to melt metal nanoparticles on its surface, but the nanotube itself seemed to stay cool, and so did the metal contacts attached to it.
Re: [Vo]:Remote Joule heating in Carbon nanotubes
The article makes it appear as if they stumbled on the effect, but the abstract (click link at end of article)makes it clear they were looking for the effect because some new models of joule heating predicted it. harry On Tue, Apr 10, 2012 at 11:21 PM, Jojo Jaro jth...@hotmail.com wrote: Correct me if I'm wrong, but isn't this just some kind of Inductive Heating? I don't see why this would be something new.
Re: [Vo]:Remote Joule heating in Carbon nanotubes
Inductive heating usually requires a time changing current in order to heat the nearby conductor. Maybe the current in this case is more like a series of quantum pulses which might have the time varying property required. A great deal of the effect would depend upon the relative magnitude of the current and thus the flow characteristics of electrons within. I assumed that the basic experiment consists of a DC current instead of AC. AC current could certainly be used to generate inductive heating. The thought occurred to me that the uncertainty principle might allow a portion of the electron current to flow within the nearby conductors effectively bypassing the nanotube. If this theory is correct then the effective size of the electrons must be such that they extend outside of the tube. Dave -Original Message- From: Jojo Jaro jth...@hotmail.com To: Vortex Vortex-l@eskimo.com Sent: Tue, Apr 10, 2012 11:22 pm Subject: [Vo]:Remote Joule heating in Carbon nanotubes Correct me if I'm wrong, but isn't this just some kind of Inductive Heating? I don't see why this would be something new.
