Research in microscale heat transfer promises to benefit military systems

Mar 14, 2011 by Maria Callier
Graduate student Huarui Sun performs sensitive measurement of interfacial thermal transport using an ultrafast laser system. (Credit: Abhishek Yadav)

(PhysOrg.com) -- A two-year-old Air Force Office of Scientific Research Multidisciplinary University Research Initiative effort involving the University of Michigan, Stanford University, Brown University, and the University of California at Santa Cruz is making great strides in achieving a fundamental understanding of heat transfer at interfaces.

"We aim to accomplish this by applying state-of-the-art techniques from several disciplines to arrive at a set of design rules for engineering interfaces with desired thermal properties," said Dr. Kevin Pipe, a professor of Mechanical Engineering at the University of Michigan who is leading the project.

is important to the performance, power requirements, and reliability of many military and commercial systems including thermoelectric refrigerators, waste heat recovery systems, heat sinks, power electronics, thermal barrier coatings, and thermal interface materials.

"Recent advances in nanoscience have enabled the precise control of interface physical and chemical structure, but the fundamental physics that link this nanoscale structure with thermal transport is not yet well developed, inhibiting the engineering of interfaces with radically enhanced thermal properties," said Pipe.

Interfaces can decrease a composite material's by scattering the that are the primary carriers of heat in solids.

"This scattering process gives each interface a thermal resistance," said Pipe.

The researchers have made a number of achievements during the first two years of their research effort, including the development of a high-speed thermal imaging system and a technique to measure the propagation of phonons, the elementary packets of vibrational energy that carry heat, with high signal-to-noise ratio. Using ultrafast laser systems that emit less than 50 femtoseconds in duration, Pipe's team creates high-frequency acoustic waves at the surface of a material and in a process similar to medical ultrasound imaging measures how these waves scatter off of buried interface structures.

"In one of our measurements," said Pipe, "we use picosecond x-ray pulses to look directly at atomic motion near an interface as heat flows across it."

By applying precise nanofabrication techniques to create interfaces with known atomic structure, the researchers are able to link measured heat transfer properties with the predictions of atomistic simulations to yield further understanding of the fundamental processes involved.

"By advancing the state-of-the-art in these techniques, we aim to fully characterize an interface and achieve a complete understanding of what controls the flow of heat across it," said Pipe.

"The Michigan MURI led by Professor Kevin Pipe is making extraordinary breakthroughs to understand nano-scale thermal transport by precisely tailoring interfaces using advanced processing techniques and innovative experimental laser based methods to delineate phonon modes participating in the heat transport," said Dr. Kumar V. Jata, Thermal Sciences, AFOSR, Arlington, Va. and Materials Science, Asian Office of Aerospace Research and Development, Tokyo, Japan. "In the past we never paid attention to the interfaces and considered them as either perfect or imperfect, one or the other."

Explore further: Researchers create 3-D stereoscopic color prints with nanopixels

Provided by Air Force Office of Scientific Research

3 /5 (1 vote)
add to favorites email to friend print save as pdf

Related Stories

Computation helps predict heat transfer in diamond

Sep 22, 2009

(PhysOrg.com) -- Cornell researcher Derek Stewart and collaborators have calculated the exact mechanism by which diamond conducts heat, a breakthrough that could lend insight into many fields, including electronics.

Recommended for you

Thin film produces new chemistry in 'nanoreactor'

Nov 19, 2014

Physicists of the University of Groningen and the FOM Foundation, led by professor Beatriz Noheda, have discovered a new manganese compound that is produced by tension in the crystal structure of terbium manganese oxide. ...

Billions of 'nanoreactors' inform materials design

Nov 18, 2014

Imagine building a chemical reactor small enough to study nanoparticles a billionth of a meter across. A billion times smaller than a raindrop is the volume of an E. coli cell. And another million times smaller ...

When science and art produce nanosculpture marvels

Nov 18, 2014

(Phys.org) —Quite a claim: a sculpture as the smallest creation of the human form in history. The sculptor, Jonty Hurwitz, said he loves the Internet. That is because, since the nanosculpture exhibit launch, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.