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


Geothermal heat contributes to Greenland ice melt
An international team that includes University of Montana researcher Jesse Johnson has learned that the Earth's internal heat enhances rapid ice flow and subglacial melting in Greenland.

CCNY researchers introduce new route to thermal measurements with nanometer resolution
Understanding nanoscale heat flow is critical in the design of integrated electronic devices and in the development of materials for thermal insulation and thermoelectric energy recovery.

Heat radiates 10,000 times faster at the nanoscale
When heat travels between two objects that aren't touching, it flows differently at the smallest scales--distances on the order of the diameter of DNA, or 1/50,000 of a human hair.

The geography of Antarctica's underside
Planetary scientists would be thrilled if they could peel the Earth like an orange and look at what lies beneath the thin crust. We live on the planet's cold surface, but the Earth is a solid body and the surface is continually deformed, split, wrinkled and ruptured by the roiling of warmer layers beneath it.

Is black phosphorous the next big thing in materials?
A new experimental revelation about black phosphorus nanoribbons should facilitate the future application of this highly promising material to electronic, optoelectronic and thermoelectric devices.

Could 'The Day After Tomorrow' happen?
A researcher from the University of Southampton has produced a scientific study of the climate scenario featured in the disaster movie 'The Day After Tomorrow'.

New Geosphere themed issue: The anatomy of rifting
Research at continental rifts, mid-ocean ridges, and transforms has shown that new plates are created by extensional tectonics, magma intrusion, and volcanism.

Study proposes common mechanism for shallow and deep earthquakes
Earthquakes are labeled "shallow" if they occur at less than 50 kilometers depth.

The fearsome foursome: Technologies enable ambitious MMS mission
It was unprecedented developing a mission that could fly four identically equipped spacecraft in a tight formation and take measurements 100 times faster than any previous space mission -- an achievement enabled in part by four NASA-developed technologies that in some cases took nearly 10 years to mature.

Tunneling across a tiny gap
Conduction and thermal radiation are two ways in which heat is transferred from one object to another: Conduction is the process by which heat flows between objects in physical contact, such as a pot of tea on a hot stove, while thermal radiation describes heat flow across large distances, such as heat emitted by the sun.
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.

Computational Fluid Mechanics and Heat Transfer, Third Edition (Series in Computational and Physical Processes in Mechanics and Thermal Sciences)

Computational Fluid Mechanics and Heat Transfer, Third Edition (Series in Computational and Physical Processes in Mechanics and Thermal Sciences)
by Richard H. Pletcher (Author), John C. Tannehill (Author), Dale Anderson (Author)


Thoroughly updated to include the latest developments in the field, this classic text on finite-difference and finite-volume computational methods maintains the fundamental concepts covered in the first edition. As an introductory text for advanced undergraduates and first-year graduate students, Computational Fluid Mechanics and Heat Transfer, Third Edition provides the background necessary for solving complex problems in fluid mechanics and heat transfer. Divided into two parts, the book first lays the groundwork for the essential concepts preceding the fluids equations in the second part. It includes expanded coverage of turbulence and large-eddy simulation (LES) and additional material included on detached-eddy simulation (DES) and direct numerical simulation (DNS). Designed as a...

Turbulent Multiphase Flows with Heat and Mass Transfer (Fluid Mechanics)

Turbulent Multiphase Flows with Heat and Mass Transfer (Fluid Mechanics)
by Roland Borghi (Author), Fabien Anselmet (Author)


Numerous industrial systems or natural environments involve multiphase flows with heat and mass transfer. The authors of this book present the physical modeling of these flows, in a unified way, which can include various physical aspects and several levels of complexity.
Thermal engineering and nuclear reactors; the extraction and transport of petroleum products; diesel and rocket engines; chemical engineering reactors and fluidized beds; smoke or aerosol dispersion; landslides and avalanches − the modeling of multiphase flows with heat and mass transfer for all these situations can be developed following a common methodology. This book is devoted to the description of the mathematical bases of how to incorporate adequate physical ingredients in agreement with known...

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...

Applied Research in Hydraulics and Heat Flow

Applied Research in Hydraulics and Heat Flow
by Kaveh Hariri Asli (Author), Soltan Ali Ogli Aliyev (Author)


Applied Research in Hydraulics and Heat Flow covers modern subjects of mechanical engineering such as fluid mechanics, heat transfer, and flow control in complex systems as well as new aspects related to mechanical engineering education. The chapters help to enhance the understanding of both the fundamentals of mechanical engineering and their application to the solution of problems in modern industry. The book includes the most popular applications-oriented approach to engineering fluid mechanics and heat transfer. It offers a clear and practical presentation of all basic principles of fluid mechanics and heat transfer, tying theory directly to real devices and systems used in mechanical and chemical engineering. It presents new procedures for problem-solving and design, including...

Proteins: Energy, Heat and Signal Flow (Computation in Chemistry)

Proteins: Energy, Heat and Signal Flow (Computation in Chemistry)
by David M. Leitner (Editor), John E. Straub (Editor)


Computational modeling can provide a wealth of insight into how energy flow in proteins mediates protein function. Computational methods can also address fundamental questions related to molecular signaling and energy flow in proteins. Proteins: Energy, Heat and Signal Flow presents state-of-the-art computational strategies for studying energy redistribution, signaling, and heat transport in proteins and other molecular machines. The first of four sections of the book address the transport of energy in molecular motors, which function through a combination of chemically driven large-scale conformational changes and charge transport. Focusing on vibrational energy flow in proteins and nanostructures, the next two sections discuss approaches based on molecular dynamics simulations and...

Boiling Heat Transfer And Two-Phase Flow (Series in Chemical and Mechanical Engineering)

Boiling Heat Transfer And Two-Phase Flow (Series in Chemical and Mechanical Engineering)
by L S Tong (Author), Y S Tang (Author)


Completely updated, this graduate text describes the current state of boiling heat transfer and two-phase flow, in terms through which students can attain a consistent understanding. Prediction of real or potential boiling heat transfer behaviour, both in steady and transient states, is covered to aid engineering design of reliable and effective systems.

Fundamentals of the Finite Element Method for Heat and Fluid Flow

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

Introduction to Compressible Fluid Flow, Second Edition (Heat Transfer)

Introduction to Compressible Fluid Flow, Second Edition (Heat Transfer)
by Patrick H. Oosthuizen (Author), William E. Carscallen (Author)


Introduction to Compressible Fluid Flow, Second Edition offers extensive coverage of the physical phenomena experienced in compressible flow. Updated and revised, the second edition provides a thorough explanation of the assumptions used in the analysis of compressible flows. It develops in students an understanding of what causes compressible flows to differ from incompressible flows and how they can be analyzed. This book also offers a strong foundation for more advanced and focused study. The book begins with discussions of the analysis of isentropic flows, of normal and oblique shock waves and of expansion waves. The final chapters deal with nozzle characteristics, friction effects, heat exchange effects, a hypersonic flow, high-temperature gas effects, and low-density flows. This...

Two-phase Flows and Heat Transfer with Application to Nuclear Reactor Design Problems (Series in thermal and fluids engineering)

Two-phase Flows and Heat Transfer with Application to Nuclear Reactor Design Problems (Series in thermal and fluids engineering)
by Jean J. Ginoux (Author)




© 2016 BrightSurf.com