David Kirkpatrick

June 10, 2010

Nantech making better heat sinks

Really making a whole lot better heat sinks.

The release:

NANOTECH YIELDS MAJOR ADVANCE IN HEAT TRANSFER, COOLING TECHNOLOGIES

6-9-10

The journal publication this story is based on is available online: http://bit.ly/cBAKfE

CORVALLIS, Ore. – Researchers at Oregon State University and the Pacific Northwest National Laboratory have discovered a new way to apply nanostructure coatings to make heat transfer far more efficient, with important potential applications to high tech devices as well as the conventional heating and cooling industry.

These coatings can remove heat four times faster than the same materials before they are coated, using inexpensive materials and application procedures.

The discovery has the potential to revolutionize cooling technology, experts say.

The findings have just been announced in the International Journal of Heat and Mass Transfer, and a patent application has been filed.

“For the configurations we investigated, this approach achieves heat transfer approaching theoretical maximums,” said Terry Hendricks, the project leader from the Pacific Northwest National Laboratory. “This is quite significant.”

The improvement in heat transfer achieved by modifying surfaces at the nanoscale has possible applications in both micro- and macro-scale industrial systems, researchers said. The coatings produced a “heat transfer coefficient” 10 times higher than uncoated surfaces.

Heat exchange has been a significant issue in many mechanical devices since the Industrial Revolution.

The radiator and circulating water in an automobile engine exist to address this problem. Heat exchangers are what make modern air conditioners or refrigerators function, and inadequate cooling is a limiting factor for many advanced technology applications, ranging from laptop computers to advanced radar systems.

“Many electronic devices need to remove a lot of heat quickly, and that’s always been difficult to do,” said Chih-hung Chang, an associate professor in the School of Chemical, Biological and Environmental Engineering at Oregon State University. “This combination of a nanostructure on top of a microstructure has the potential for heat transfer that’s much more efficient than anything we’ve had before.”

There’s enough inefficiency in heat transfer, for instance, that for water to reach its boiling point of 100 degrees centigrade, the temperature of adjacent plates often has to be about 140 degrees centigrade. But with this new approach, through both their temperature and a nanostructure that literally encourages bubble development, water will boil when similar plates are only about 120 degrees centigrade.

To do this, heat transfer surfaces are coated with a nanostructured application of zinc oxide, which in this usage develops a multi-textured surface that looks almost like flowers, and has extra shapes and capillary forces that encourage bubble formation and rapid, efficient replenishment of active boiling sites.

In these experiments, water was used, but other liquids with different or even better cooling characteristics could be used as well, the researchers said. The coating of zinc oxide on aluminum and copper substrates is inexpensive and could affordably be applied to large areas.

Because of that, this technology has the potential not only to address cooling problems in advanced electronics, the scientists said, but also could be used in more conventional heating, cooling and air conditioning applications. It could eventually find its way into everything from a short-pulse laser to a home air conditioner or more efficient heat pump systems. Military electronic applications that use large amounts of power are also likely, researchers said.

The research has been supported by the Army Research Laboratory. Further studies are being continued to develop broader commercial applications, researchers said.

“These results suggest the possibility of many types of selectively engineered, nanostructured patterns to enhance boiling behavior using low cost solution chemistries and processes,” the scientists wrote in their study. “As solution processes, these microreactor-assisted, nanomaterial deposition approaches are less expensive than carbon nanotube approaches, and more importantly, processing temperatures are low.”

About the OSU College of Engineering: The OSU College of Engineering is among the nation’s largest and most productive engineering programs. In the past six years, the College has more than doubled its research expenditures to $27.5 million by emphasizing highly collaborative research that solves global problems, spins out new companies, and produces opportunity for students through hands-on learning.

Nanotech coating by Oregon State University.

This nanoscale-level coating of zinc oxide on top of a copper plate holds the potential to dramatically increase heat transfer characteristics and lead to a revolution in heating and cooling technology, according to experts at Oregon State University and the Pacific Northwest National Laboratory. (Photo courtesy of Oregon State University)

May 11, 2010

Graphene as a heat sink

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 12:43 am

Nanotech news from UC Riverside.

The release:

Hot new material can keep electronics cool

Few atomic layers of graphene reveal unique thermal properties

IMAGE: Alexander Balandin is a professor of electrical engineering in the Bourns College of Engineering at the University of California, Riverside.

Click here for more information.

Professor Alexander Balandin and a team of UC Riverside researchers, including Chun Ning Lau, an associate professor of physics, have taken another step toward new technology that could keep laptops and other electronic devices from overheating.

Balandin, a professor of electrical engineering in the Bourns College of Engineering, experimentally showed in 2008 that graphene, a recently discovered single-atom-thick carbon crystal, is a strong heat conductor. The problem for practical applications was that it is difficult to produce large, high quality single atomic layers of the material.

Now, in a paper published in Nature Materials, Balandin and co-workers found that multiple layers of graphene, which are easier to make, retain the strong heat conducting properties.

That’s also a significant discovery in fundamental physics. Balandin’s group, in addition to measurements, explained theoretically how the materials’ ability to conduct heat evolves when one goes from conventional three-dimensional bulk materials to two-dimensional atomically-thin films, such as graphene.

The results published in Nature Materials may have important practical applications in removal of dissipated hear from electronic devices.

Heat is an unavoidable by-product when operating electronic devices. Electronic circuits contain many sources of heat, including millions of transistors and interconnecting wiring. In the past, bigger and bigger fans have been used to keep computer chips cool, which improved performance and extended their life span. However, as computers have become faster and gadgets have gotten smaller and more portable the big-fan solution no longer works.

New approaches to managing heat in electronics include incorporating materials with superior thermal properties, such as graphene, into silicon computer chips. In addition, proposed three-dimension electronics, which use vertical integration of computer chips, would depend on heat removal even more, Balandin said.

Silicon, the most common electronic material, has good electronic properties but not so good thermal properties, particularly when structured at the nanometer scale, Balandin said. As Balandin’s research shows, graphene has excellent thermal properties in addition to unique electronic characteristics.

“Graphene is one of the hottest materials right now,” said Balandin, who is also chair of the Material Sciences and Engineering program. “Everyone is talking about it.”

Graphene is not a replacement for silicon, but, instead could be used in conjunction with silicon, Balandin said. At this point, there is no reliable way to synthesize large quantities of graphene. However, progress is being made and it could be possible in a year or two, Balandin said.

Initially, graphene would likely be used in some niche applications such as thermal interface materials for chip packaging or transparent electrodes in photovoltaic solar cells, Balandin said. But, in five years, he said, it could be used with silicon in computer chips, for example as interconnect wiring or heat spreaders. It may also find applications in ultra-fast transistors for radio frequency communications. Low-noise graphene transistors have already been demonstrated in Balandin’s lab.

Balandin published the Nature Materials paper with two of his graduate students Suchismita Ghosh, who is now at Intel Corporation, and Samia Subrina, Lau. one of her graduate students, Wenzhong Bao, and Denis L. Nika and Evghenii P. Pokatilov, visting researchers in Balandin’s lab who are based at the State University of Moldova.

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The University of California, Riverside (www.ucr.edu) is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California’s diverse culture, UCR’s enrollment of over 19,000 is expected to grow to 21,000 students by 2020. The campus is planning a medical school and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Graduate Center. The campus has an annual statewide economic impact of more than $1 billion.

July 7, 2008

Building a better heat sink and mass producing nanotube circuits

From KurzweilAI.net — amazing advances in chip-cooling tech removes 1K watts per square centimeter and nanotube-laden integrated circuits become economical.

Chip-cooling Technology Achieves ‘Dramatic’ 1,000-watt Capacity
Science Daily, July 2, 2008

Purdue University researchers have developed a technology that uses “microjets” to deposit liquid into tiny channels and remove five times more heat (1,000 watts per square centimeter) than other experimental high-performance chip-cooling methods for computers and electronics.

 
Read Original Article>>

Engineers show nanotube circuits can be made en masse
Nanowerk News, July 4, 2008

Stanford electrical engineers have developed a method for making integrated circuit chips with the needed variety of logic gates on the scale and with the parallelism that the semiconductor industry must employ to make chips that are economical.

The Stanford-devised process involves growing nanotubes on a quartz wafer and then transferring them onto a silicon wafer patterned with metal electrodes. The nanotubes could then connect the electrodes to make transistors and logic gates.

 
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