Science Current Events | Science News | Brightsurf.com
 

Controlling heat flow with atomic-level precision

April 23, 2012
CHAMPAIGN, Ill. - Through a combination of atomic-scale materials design and ultrafast measurements, researchers at the University of Illinois have revealed new insights about how heat flows across an interface between two materials.

The researchers demonstrated that a single layer of atoms can disrupt or enhance heat flow across an interface. Their results are published this week in Nature Materials.

Improved control of heat exchange is a key element to enhancing the performance of current technologies such as integrated circuits and combustion engines as well as emerging technologies such as thermoelectric devices, which harvest renewable energy from waste heat. However, achieving control is hampered by an incomplete understanding of how heat is conducted through and between materials.

"Heat travels through electrically insulating material via 'phonons,' which are collective vibrations of atoms that travel like waves through a material," said David Cahill, a Willett Professor and the head of materials science and engineering at Illinois and co-author of the paper. "Compared to our knowledge of how electricity and light travel through materials, scientists' knowledge of heat flow is rather rudimentary."

One reason such knowledge remains elusive is the difficulty of accurately measuring temperatures, especially at small-length scales and over short time periods - the parameters that many micro and nano devices operate under.

Over the past decade, Cahill's group has refined a measurement technique using very short laser pulses, lasting only one trillionth of a second, to probe heat flow accurately with nanometer-depth resolution. Cahill teamed up with Paul Braun, the Racheff Professor of Materials Science and Engineering at the U. of I. and a leader in nanoscale materials synthesis, to apply the technique to understanding how atomic-scale features affect heat transport.

"These experiments used a 'molecular sandwich' that allowed us to manipulate and study the effect that chemistry at the interface has on heat flow, at an atomic scale," Braun said.

The researchers assembled their molecular sandwich by first depositing a single layer of molecules on a quartz surface. Next, through a technique known as transfer-printing, they placed a very thin gold film on top of these molecules. Then they applied a heat pulse to the gold layer and measured how it traveled through the sandwich to the quartz at the bottom.

By adjusting just the composition of the molecules in contact with the gold layer, the group observed a change in heat transfer depending on how strongly the molecule bonded to the gold. They demonstrated that stronger bonding produced a twofold increase in heat flow.

"This variation in heat flow could be much greater in other systems," said Mark Losego, who led this research effort as a postdoctoral scholar at Illinois and is now a research professor at North Carolina State University. "If the vibrational modes for the two solids were more similar, we could expect changes of up to a factor of 10 or more."

The researchers also used their ability to systematically adjust the interfacial chemistry to dial-in a heat flow value between the two extremes, verifying the ability to use this knowledge to design materials systems with desired thermal transport properties.

"We've basically shown that changing even a single layer of atoms at the interface between two materials significantly impacts heat flow across that interface," said Losego.

Scientifically, this work opens up new avenues of research. The Illinois group is already working toward a deeper fundamental understanding of heat transfer by refining measurement methods for quantifying interfacial bonding stiffness, as well as investigating temperature dependence, which will reveal a better fundamental picture of how the changes in interface chemistry are disrupting or enhancing the flow of heat across the interface.

"For many years, the physical models for heat flow between two materials have ignored the atomic-level features of an interface," Cahill said. "Now these theories need to be refined. The experimental methods developed here will help quantify the extent to which interfacial structural features contribute to heat flow and will be used to validate these new theories."

Braun and Cahill are affiliated with the Frederick Seitz Materials Research Laboratory at the U. of I. Braun is also affiliated with the department of chemistry and the Beckman Institute for Advanced Science and Technology. The Air Force Office of Scientific Research supported this work.

University of Illinois at Urbana-Champaign


Related Heat Flow Current Events and Heat Flow News Articles


Miranda: An Icy Moon Deformed by Tidal Heating
Miranda, a small, icy moon of Uranus, is one of the most visually striking and enigmatic bodies in the solar system. Despite its relatively small size, Miranda appears to have experienced an episode of intense resurfacing that resulted in the formation of at least three remarkable and unique surface features -- polygonal-shaped regions called coronae.

Resolving apparent inconsistencies in optimality principles for flow processes in geosystems
Optimality principles have been used, in a holistic approach, to describe flow processes in several important geosystems. Optimality principles refer to the state of a physical system that is controlled by an optimal condition subject to physical and/or resource constraints.

Nanoscale heat flow predictions
Physicists are now designing novel materials with physical properties tailored to meet specific energy consumption needs.

Thermal conductance can be controlled like waves using nanostructures
Thermal conduction is a familiar everyday phenomenon. In a hot sauna, for instance, you can sit comfortably on a wooden bench that has a temperature of 100C (212F), but if you touch a metallic nail with the same temperature, you will hurt yourself.

Nanoscale pillars could radically improve conversion of heat to electricity
University of Colorado Boulder scientists have found a creative way to radically improve thermoelectric materials, a finding that could one day lead to the development of improved solar panels, more energy-efficient cooling equipment, and even the creation of new devices that could turn the vast amounts of heat wasted at power plants into more electricity.

Research could bring new devices that control heat flow
Researchers are proposing a new technology that might control the flow of heat the way electronic devices control electrical current, an advance that could have applications in a diverse range of fields from electronics to textiles.

Cooling Microprocessors with Carbon Nanotubes
"Cool it!" That's a prime directive for microprocessor chips and a promising new solution to meeting this imperative is in the offing. Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a "process friendly" technique that would enable the cooling of microprocessor chips through carbon nanotubes.

Volcano discovered smoldering under a kilometer of ice in West Antarctica
It wasn't what they were looking for but that only made the discovery all the more exciting.

The oldest ice core - Finding a 1.5 million-year record of Earth's climate
How far into the past can ice-core records go? Scientists have now identified regions in Antarctica they say could store information about Earth's climate and greenhouse gases extending as far back as 1.5 million years, almost twice as old as the oldest ice core drilled to date.

NRL Researchers Discover Novel Material for Cooling of Electronic Devices
A team of theoretical physicists at the U.S. Naval Research Laboratory (NRL) and Boston College has identified cubic boron arsenide as a material with an extraordinarily high thermal conductivity and the potential to transfer heat more effectively from electronic devices than diamond, the best-known thermal conductor to date.
More Heat Flow Current Events and Heat Flow News Articles

Numerical Heat Transfer and Fluid Flow (Hemisphere Series on Computational Methods in Mechanics and Thermal Science)

Numerical Heat Transfer and Fluid Flow (Hemisphere Series on Computational Methods in Mechanics and Thermal Science)
by Suhas Patankar (Author)


This book focuses on heat and mass transfer, fluid flow, chemical reaction, and other related processes that occur in engineering equipment, the natural environment, and living organisms. Using simple algebra and elementary calculus, the author develops numerical methods for predicting these processes mainly based on physical considerations. Through this approach, readers will develop a deeper understanding of the underlying physical aspects of heat transfer and fluid flow as well as improve their ability to analyze and interpret computed results.

Fundamentals of the Finite Element Method for Heat and Fluid Flow

Fundamentals of the Finite Element Method for Heat and Fluid Flow
by R. W. Lewis (Author), Perumal Nithiarasu (Author), Kankanhalli Seetharamu (Author)


Heat transfer is the area of engineering science which describes the energy transport between material bodies due to a difference in temperature. The three different modes of heat transport are conduction, convection and radiation. In most problems, these three modes exist simultaneously. However, the significance of these modes depends on the problems studied and often, insignificant modes are neglected.Very often books published on Computational Fluid Dynamics using the Finite Element Method give very little or no significance to thermal or heat transfer problems. From the research point of view, it is important to explain the handling of various types of heat transfer problems with different types of complex boundary conditions. Problems with slow fluid motion and heat transfer can be...

Engineering Flow and Heat Exchange

Engineering Flow and Heat Exchange
by Octave Levenspiel (Author)


Professor Levenspiel's text remains the most practical volume available on the design of heat transfer equipment - an excellent introduction to real-world applications for advanced undergraduates and an indispensable reference for professionals. Each chapter includes illustrative examples and problems.

The Analysis Of Harmonic Maps And Their Heat Flows,

The Analysis Of Harmonic Maps And Their Heat Flows,
by Fanghua Lin (Author), Changyou Wang (Contributor)


This book provides a broad yet comprehensive introduction to the analysis of harmonic maps and their heat flows. The first part of the book contains many important theorems on the regularity of minimizing harmonic maps by Schoen–Uhlenbeck, stationary harmonic maps between Riemannian manifolds in higher dimensions by Evans and Bethuel, and weakly harmonic maps from Riemannian surfaces by Helein, as well as on the structure of a singular set of minimizing harmonic maps and stationary harmonic maps by Simon and Lin. The second part of the book contains a systematic coverage of heat flow of harmonic maps that includes Eells–Sampson's theorem on global smooth solutions, Struwe's almost regular solutions in dimension two, Sacks–Uhlenbeck's blow-up analysis in dimension two, Chen-Struwe's...

Chemical Engineering Volume 1, Sixth Edition: Fluid Flow, Heat Transfer and Mass Transfer (Coulson and Richardsons Chemical Engineering)

Chemical Engineering Volume 1, Sixth Edition: Fluid Flow, Heat Transfer and Mass Transfer (Coulson and Richardsons Chemical Engineering)
by J R Backhurst (Author), J H Harker (Author), J.F. Richardson (Author), J.M. Coulson (Author), R.P. Chhabra (Editor)


Coulson and Richardson's classic series provides the student with an account of the fundamentals of chemical engineering and constitutes the definitive work on the subject for academics and practitioners. Each book provides clear explanations of theory and thorough coverage of practical applications, supported by numerous worked examples and problems. Thus, the text is designed for students as well as being comprehensive in coverage.



This volume covers the three main transport process of interest to chemical engineers - momentum transfer (fluid flow), heat transfer and mass transfer and the relationships between them. The concluding chapter covers an application where each of these processes is occurring simultaneously - water cooling and humidification. The topics covered...

Crustal Heat Flow: A Guide to Measurement and Modelling

Crustal Heat Flow: A Guide to Measurement and Modelling
by G. R. Beardsmore (Author), J. P. Cull (Author)


Crustal Heat Flow: A Guide to Measurement and Modelling is a handbook for geologists and geophysicists who manipulate thermal data, particularly for petroleum exploration. In theory and with practical examples, the book discusses the sources of heat within the crust, describes how to maximize the accuracy of temperature data, covers the measurement of the thermal properties of rocks, and explains a number of maturity indicators. The second part covers a range of thermodynamic models of the lithosphere and shows how these can be used to reconstruct the thermal history of individual sedimentary basins.

Fluid Flow, Heat Transfer and Boiling in Micro-Channels (Heat and Mass Transfer)

Fluid Flow, Heat Transfer and Boiling in Micro-Channels (Heat and Mass Transfer)
by L. P. Yarin (Author), A. Mosyak (Author), G. Hetsroni (Author)


The subject of the book is uid dynamics and heat transfer in micro-channels. This problem is important for understanding the complex phenomena associated with single- and two-phase ows in heated micro-channels. The challenge posed by high heat uxes in electronic chips makes thermal management a key factor in the development of these systems. Cooling of mic- electronic components by new cooling technologies, as well as improvement of the existing ones, is becoming a necessity as the power dissipation levels of integrated circuits increases and their sizes decrease. Miniature heat sinks with liquid ows in silicon wafers could signi cantly improve the performance and reliability of se- conductor devices. The improvements are made by increasing the effective thermal conductivity, by reducing...

Nanoparticle Heat Transfer and Fluid Flow (Advances in Numerical Heat Transfer)

Nanoparticle Heat Transfer and Fluid Flow (Advances in Numerical Heat Transfer)
by W. J. Minkowycz (Editor), E M Sparrow (Editor), J. P. Abraham (Editor)


Featuring contributions by leading researchers in the field, Nanoparticle Heat Transfer and Fluid Flow explores heat transfer and fluid flow processes in nanomaterials and nanofluids, which are becoming increasingly important across the engineering disciplines. The book covers a wide range, from biomedical and energy conversion applications to materials properties, and addresses aspects that are essential for further progress in the field, including numerical quantification, modeling, simulation, and presentation. Topics include: A broad review of nanofluid applications, including industrial heat transfer, biomedical engineering, electronics, energy conversion, membrane filtration, and automotive An overview of thermofluids and their importance in biomedical applications and...

Two-phase Flow and Heat Transfer in the Power and Process Industries

Two-phase Flow and Heat Transfer in the Power and Process Industries
by A. E. Bergles (Author)




FEFLOW: Finite Element Modeling of Flow, Mass and Heat Transport in Porous and Fractured Media

FEFLOW: Finite Element Modeling of Flow, Mass and Heat Transport in Porous and Fractured Media
by Hans-Joerg Diersch (Author)


FEFLOW is an acronym of Finite Element subsurface FLOW simulation system and solves the governing flow, mass and heat transport equations in porous and fractured media by a multidimensional finite element method for complex geometric and parametric situations including variable fluid density, variable saturation, free surface(s), multispecies reaction kinetics, non-isothermal flow and multidiffusive effects. FEFLOW comprises theoretical work, modeling experiences and simulation practice from a period of about 40 years. In this light, the main objective of the present book is to share this achieved level of modeling with all required details of the physical and numerical background with the reader. The book is intended to put advanced theoretical and numerical methods into the hands of...

© 2014 BrightSurf.com