Heat Transfer Breakthrough with Diamond Copper Composite

This is an interesting development. It seems every technological advance has a heat problem piggy backing along. So a nifty cooling super performer is automatically welcome. It may not be used in all but the most pressing cases, but this establishes the capability.

We have a copper diamond wick that extracts heat two orders of magnitude faster.

We will be soon be fabricating multi layered skins that will include functional solid state refrigeration as core to the design. The major remaining question was the management of heat flow. This goes a long way to resolving just that. Apparently a working fluid is used and that also suggests that such fluid can transport the heat away from the working device efficiently.

A working magnetic exclusion bubble is becoming more and more feasible and this could also do wonders for the processor industry. Think again in terms of a robust three dimensional architecture that has been avoided not because of technical difficulty but because of heat management difficulties. Now we can imagine such architecture.

I believe that this is the first credible advance in heat transfer technology superseding our present decades old techniques.

Composite of diamond and copper Helps to Make Heat Transfer 100 Times Better

http://nextbigfuture.com/2009/07/composite-of-diamond-and-copper-helps.html

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sample of a novel material that may be used to remove heat from future radar systems. (Georgia Tech Photo: Gary Meek)

Researchers at the Georgia Tech Research Institute (GTRI) are developing a novel material for transferring heat away from ultra-high-power defense electronics.

The exotic material, a composite of diamond and copper, is one of the materials under development as part of a new concept called a “Thermal Ground Plane” that aims to remove heat up to 100 times more effectively than present thermal-conducting schemes.Georgia Tech is working with the Raytheon Co. on a project that seeks to raise thermal conductivity capabilities to 20,000 watts per meter Kelvin (a measure of thermal-conductivity efficiency). That’s a tall order, considering that the current conductivity champion, for radar applications, is a copper material with performance of approximately 200 to 300 watts per meter Kelvin. The three-phase, four-year project is sponsored by the Microsystems Technology Office of the Defense Advanced Research Projects Agency (DARPA).

This improved cooling capability could benefit future high-power transmit-receive (T/R) module packages. Because of their higher power, those transmit-receive modules will also have higher cooling needs that may require a Thermal Ground Plane—a sort of heat-dissipating sandwich about one millimeter thick that would be part of the T/R module’s packaging.

"A Thermal Ground Plane is basically a materials system,” Nadler explained. “The most thermally conductive natural material, pure diamond, has a conductivity of about 2,000 watts per meter Kelvin. We’re aiming for 20,000, and to do that we have to look at the problem from a materials systems standpoint.”

The conductivity of that material would be improved with the addition of a liquid coolant able to carry heat away from the T/R module devices in the same way that sweat cools a body. A metal heat sink would help the liquid coolant dissipate the heat by condensing the vapor back to a fluid. Using a liquid coolant takes advantage of phase changes—the conversion of matter between liquid and vapor states. The diamond-copper material would conduct heat to the liquid coolant and optimize cooling through wicking and evaporation. Then, the heat would be rejected as the vapor is re-condensed to a liquid on the side attached to the metal heat sink.

"The trick is to use evaporation, condensation and intrinsic thermal conductivity together, in series, in a continuous system,” Nadler said. “The whole device is a closed loop.”

In addition, the porous internal structure of the diamond-copper material must have exactly the right size and shape to maximize its own intrinsic heat conductivity. Yet its internal structure must also be designed in ways that can help draw the liquid coolant toward the heat source to facilitate evaporation. Nadler explained that liquid coolant flow can be maximized by fine tuning such mechanisms as the capillarity of the diamond-copper material.

Capillarity refers to a given structure’s ability to draw in a substance, especially a liquid, the way a sponge absorbs water or a medical technician pulls a drop of blood up into a narrow glass tube.

Lawrence Plasma Fusion Build Out Update

This bit is a quick update on present progress with the focus fusion device recently funded. They are presently in the fabrication stage and this suggests that they may be forthcoming in reporting actual test results. They are certainly continuing to encourage our interest in the project, and certainly the road to additional financial support is plenty of publicity.

The graphics are great and that certainly helps.

I am actually optimistic about fusion energy science this time around. There has never been a real first time around to start with. It always was big science and huge budgets with oversized toys.

Now at least three or more methodologies are in contention and even if they fail miserably, we will gain knowledge for what is small change. If you have a good idea that could plausibly work, it is no big trick to run simulations and from that attract the money.

Lawrenceville Plasma Physics : Focus Fusion/Dense Plasma Focus update

June 12, 2009

http://www.lawrencevilleplasmaphysics.com/index.php?pr=News

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Lawrenceville Plasma Physics (LPP’s) design team has now completed the six-month design phase of the project, finishing design work on the device, the shielding wall and the vacuum chamber.

We are now into the fabrication and construction phase, which will last three months. LPP has submitted a concept paper to the new Advanced Research Projects Agency-Energy. ARPA-E is a new agency, molded on DARPA, which is soliciting proposals for “transformational” energy technology. Based on the 8-page concepts papers, ARPA-E will ask selected proposers to submit a full 50-page application. We will know if we are selected for that step by late June.

Graphene IC Interconnects

As my long time readers may have noticed, I am tracking the emergence of graphene as closely as possible. It is unbelievably revolutionary and it has yet to disappoint. No wonder physicists are clearly excited as are material scientists.

Here we begin to answer the questions related to produce electronic circuits using graphene as a current conductor.

I got excited about amorphous metal twenty years ago and was disappointed that it never really got going. I think it was just too soon. How can you not love a tape that channels current along the surface for experiments in magnetism? It led directly to the modern starter motor.

The same behavior is happening with this material and it has the wonderful characteristic that it will not melt in contact with molten metals. In theory, one could make a bag out of a sheet of graphene and fill it with molten tungsten. Just do not let any oxygen nearby.

The potential of the electrical behavior been managed by geometry has not even begun to be explored.

It may be early days, but everyone has the after burners on for this one.

Graphene May Have Advantages Over Copper For Future IC Interconnects


http://www.energy-daily.com/reports/Graphene_May_Have_Advantages_Over_Copper_For_Future_IC_Interconnects_999.html



by Staff Writers
Atlanta GA (SPX) Jun 05, 2009

The unique properties of thin layers of graphite-known as graphene-make the material attractive for a wide range of potential electronic devices. Researchers have now experimentally demonstrated the potential for another graphene application: replacing copper for interconnects in future generations of integrated circuits.

In a paper published in the June 2009 issue of the IEEE journal Electron Device Letters, researchers at the Georgia Institute of Technology report detailed analysis of resistivity in graphene nanoribbon interconnects as narrow as 18 nanometers.

The results suggest that graphene could out-perform copper for use as on-chip interconnects-tiny wires that are used to connect transistors and other devices on integrated circuits. Use of graphene for these interconnects could help extend the long run of performance improvements for silicon-based integrated circuit technology.

"As you make copper interconnects narrower and narrower, the resistivity increases as the true nanoscale properties of the material become apparent," said Raghunath Murali, a research engineer in Georgia Tech's Microelectronics Research Center and the School of Electrical and Computer Engineering.

"Our experimental demonstration of graphene nanowire interconnects on the scale of 20 nanometers shows that their performance is comparable to even the most optimistic projections for copper interconnects at that scale. Under real-world conditions our graphene interconnects probably already out-perform copper at this size scale."

Beyond resistivity improvement, graphene interconnects would offer higher electron mobility, better thermal conductivity, higher mechanical strength and reduced capacitance coupling between adjacent wires.

"Resistivity is normally independent of the dimension-a property inherent to the material," Murali noted. "But as you get into the nanometer-scale domain, the grain sizes of the copper become important and conductance is affected by scattering at the grain boundaries and at the side walls. These add up to increased resistivity, which nearly doubles as the interconnect sizes shrink to 30 nanometers."

The research was supported by the Interconnect Focus Center, which is one of the Semiconductor Research Corporation/DARPA Focus Centers, and the Nanoelectronics Research Initiative through the INDEX Center.

Murali and collaborators Kevin Brenner, Yinxiao Yang, Thomas Beck and James Meindl studied the electrical properties of graphene layers that had been taken from a block of pure graphite. They believe the attractive properties will ultimately also be measured in graphene fabricated using other techniques, such as growth on silicon carbide, which now produces graphene of lower quality but has the potential for achieving higher quality.

Because graphene can be patterned using conventional microelectronics processes, the transition from copper could be made without integrating a new manufacturing technique into circuit fabrication.

"We are optimistic about being able to use graphene in manufactured systems because researchers can already grow layers of it in the lab," Murali noted. "There will be challenges in integrating graphene with silicon, but those will be overcome. Except for using a different material, everything we would need to produce graphene interconnects is already well known and established."

Experimentally, the researchers began with flakes of multi-layered graphene removed from a graphite block and placed onto an oxidized silicon substrate. They used electron beam lithography to construct four electrode contacts on the graphene, then used lithography to fabricate devices consisting of parallel nanoribbons of widths ranging between 18 and 52 nanometers.

The three-dimensional resistivity of the nanoribbons on 18 different devices was then measured using standard analytical techniques at room temperature.

The best of the graphene nanoribbons showed conductivity equal to that predicted for copper interconnects of the same size. Because the comparisons were between non-optimized graphene and optimistic estimates for copper, they suggest that performance of the new material will ultimately surpass that of the traditional interconnect material, Murali said.

"Even graphene samples of moderate quality show excellent properties," he explained. "We are not using very high levels of optimization or especially clean processes. With our straightforward processing, we are getting graphene interconnects that are essentially comparable to copper. If we do this more optimally, the performance should surpass copper."

Though one of graphene's key properties is reported to be ballistic transport-meaning electrons can flow through it without resistance-the material's actual conductance is limited by factors that include scattering from impurities, line-edge roughness and from substrate phonons-vibrations in the substrate lattice.

Use of graphene interconnects could help facilitate continuing increases in integrated circuit performance once features sizes drop to approximately 20 nanometers, which could happen in the next five years, Murali said. At that scale, the increased resistance of copper interconnects could offset performance increases, meaning that without other improvements, higher density wouldn't produce faster integrated circuits.

"This is not a roadblock to achieving scaling from one generation to the next, but it is a roadblock to achieving increased performance," he said. "Dimensional scaling could continue, but because we would be giving up so much in terms of resistivity, we wouldn't get a performance advantage from that. That's the problem we hope to solve by switching to a different materials system for interconnects."