 |
|
Size-specific cracking shakes out at the nanoscale
August 04, 2008Certain sizes of nanostructures may be more susceptible to failure by fracture than others.
That is the result of new research by LLNL's Michael Manley and colleagues from Los Alamos National Laboratory that appears as a Rapid Communication in the journal Physical Review B.
As the size of a structure gets to the nanoscale, atomic vibrations (also known as phonons) begin to feel its size and shape in an effect called phonon confinement.
While these effects play an important role in thermal transport, electronic processes and thermodynamic stability, not much is known about their role in fracture.
However, in the new research, the scientists found that at a certain thickness, excess entropy of the confined vibrations reduces the fracture energy and results in a size-specific fracture.
Manley and the Los Alamos team found that particles formed during the reaction of cerium with hydrogen (cerium hydride) fractured into stacked plates. The plates exhibited two thickness scales, one at 100 nanometers, and an additional scale at 30-nanometer scale.
"When the fracture results in nanoplates, it leads to a low level of fracture energy at a certain size, resulting in a size-specific fracture," Manley said. "This has important implications for the design of nanostructures."
"It also may prove useful in the deliberate creation of large quantities of stable nanostructures," he said.
Manley said the time scale for phonon excitations typically occurs in picoseconds, while crack growth is a slower process involving the simultaneous displacement of many planes of atoms over a relatively large distance compared to atomic vibrations. "Thus, the phonon confinement should occur instantaneously as the crack propagates," he said.
Unlike with thermodynamic stability, fracture is a weak-link process, meaning that even a local weakening could be important in dictating the fracture process.
"This could have important consequences, not only for small materials, but also for the way cracks propagate in nanostructured bulk materials," Manley said.
The research appears in the Aug. 1 online issue of Physical Review B.
Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.
Lawrence Livermore National Laboratory
While these effects play an important role in thermal transport, electronic processes and thermodynamic stability, not much is known about their role in fracture.
However, in the new research, the scientists found that at a certain thickness, excess entropy of the confined vibrations reduces the fracture energy and results in a size-specific fracture.
Manley and the Los Alamos team found that particles formed during the reaction of cerium with hydrogen (cerium hydride) fractured into stacked plates. The plates exhibited two thickness scales, one at 100 nanometers, and an additional scale at 30-nanometer scale.
"When the fracture results in nanoplates, it leads to a low level of fracture energy at a certain size, resulting in a size-specific fracture," Manley said. "This has important implications for the design of nanostructures."
"It also may prove useful in the deliberate creation of large quantities of stable nanostructures," he said.
Manley said the time scale for phonon excitations typically occurs in picoseconds, while crack growth is a slower process involving the simultaneous displacement of many planes of atoms over a relatively large distance compared to atomic vibrations. "Thus, the phonon confinement should occur instantaneously as the crack propagates," he said.
Unlike with thermodynamic stability, fracture is a weak-link process, meaning that even a local weakening could be important in dictating the fracture process.
"This could have important consequences, not only for small materials, but also for the way cracks propagate in nanostructured bulk materials," Manley said.
The research appears in the Aug. 1 online issue of Physical Review B.
Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.
Lawrence Livermore National Laboratory
Nanoscale Current Events and Nanoscale News RSSWhen a good nanoparticle goes bad
Researchers at Cornell University recently made a major breakthrough when they invented a method to test and demonstrate a long-held hypothesis that some very, very small metal particles work much better than others in various chemical processes such as converting chemical energy to electricity in fuel cells or reducing automobile pollution.
Nanoscale dimensioning is fast, cheap with new NIST optical technique
A novel technique under development at the National Institute of Standards and Technology (NIST) uses a relatively inexpensive optical microscope to quickly and cheaply analyze nanoscale dimensions with nanoscale measurement sensitivity.
New research shows that environmental gains derived from the use of nanomaterials may be offset in part by the processes used to manufacture them.
New research shows that environmental gains derived from the use of nanomaterials may be offset in part by the processes used to manufacture them.
New molecules with many branches will help unleash potential of nanotechnology
Materials science and the pharmaceutical industry could soon be revolutionized by emerging nanotechnologies based on designer molecules with long complex tree-and branch structures.
JHU chemists devise self-assembling 'organic wires'
From pacemakers constructed of materials that so closely mimic human tissues that a patient's body can't discern the difference to devices that bypass injured spinal cords to restore movement to paralyzed limbs, the possibilities presented by organic electronics read like something from a science fiction novel.
Secret Lives of Catalysts Revealed
The first-ever glimpse of nanoscale catalysts in action could lead to improved pollution control and fuel cell technologies. Scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory observed catalysts restructuring themselves in response to various gases swirling around them, like a chameleon changing its color to match its surroundings.
Engineering Nanoparticles for Maximum Strength
Because they are riddled with defects, bulk crystalline materials never achieve their ideal strength; nanocrystals, on the other hand, are so small there's no room for defects.
New research field promises radical advances in optical technologies
A new research field called transformation optics may usher in a host of radical advances including a cloak of invisibility and ultra-powerful microscopes and computers by harnessing nanotechnology and "metamaterials."
Paperwork: Buckypapers clarify electrical, optical behavior of nanotubes
Using highly uniform samples of carbon nanotubes-sorted by centrifuge for length-materials scientists at the National Institute of Standards and Technology (NIST) have made some of the most precise measurements yet of the concentrations at which delicate mats of nanotubes become transparent, conducting sheets.
Extreme nature helps scientists design nano materials
Scientists are using designs in nature from extreme environments to overcome the challenges of producing materials on the nanometre scale.
More Nanoscale Current Events and Nanoscale News Articles
 | Introduction to Nanoscale Science and Technology (Nanostructure Science and Technology) Nanoscale science and technology is a young, promising field that encompasses a wide range of disciplines including physics, chemistry, biology, electrical engineering, chemical engineering, and materials science. With rapid advances in areas such as molecular electronics, synthetic biomolecular motors, DNA-based self-assembly, and manipulation of individual atoms, nanotechnology has captured the... |
 | Electrical Transport in Nanoscale Systems by Massimiliano Di Ventra This graduate textbook provides an in-depth description of the transport phenomena relevant to systems of nanoscale dimensions. The different theoretical approaches are critically discussed, with emphasis on their basic assumptions and approximations. The book also covers information content in the measurement of currents, the role of initial conditions in establishing a steady state, and the... |
| Nanoscale: Visualizing an Invisible World by Kenneth S. Deffeyes, Stephen E. Deffeyes The world is made up of structures too small to see with the naked eye, too small to see even with an electron microscope. Einstein established the reality of atoms and molecules in the early 1900s. How can we see a world measured in fractions of nanometers? (Most atoms are less than one nanometer, less than one-billionth of a meter, in diameter.) This beautiful and fascinating book gives us a... | |
 | Nanoscale Energy Transport and Conversion: A Parallel Treatment of Electrons, Molecules, Phonons, and Photons (Mit-Pappalardo Series in Mechanical Engineering) by Gang Chen This is a graduate level textbook in nanoscale heat transfer and energy conversion that can also be used as a reference for researchers in the developing field of nanoengineering. It provides a comprehensive overview of microscale heat transfer, focusing on thermal energy storage and transport. Chen broadens the readership by incorporating results from related disciplines, from the point of view... |
 | Fabrication Engineering at the Micro and Nanoscale (The Oxford Series in Electrical and Computer Engineering) by Stephen A. Campbell Designed for advanced undergraduate or first-year graduate courses in semiconductor or microelectronic fabrication, the third edition of Fabrication Engineering at the Micro and Nanoscale provides a thorough and accessible introduction to all fields of micro and nano fabrication. Completely revised and updated, the text covers the entire basic unit processes used to fabricate integrated circuits... |
 | Ultra-Low Voltage Nano-Scale Memories (Series on Integrated Circuits and Systems) Ultra-low voltage large-scale integrated circuits (LSIs) in nano-scale technologies are needed to: -Meet the needs of a rapidly growing mobile cell phone market-Offset a significant increase in the power dissipation of high-end microprocessor units. Low power large capacity memories are a necessary component of low voltage LSIs. Many challenges arise in the process of achieving such memories as... |
 | Nanoscale Calibration Standards and Methods: Dimensional and Related Measurements in the Micro- and Nanometer Range by Günter Wilkening, Ludger Koenders The quantitative determination of the properties of micro- and nanostructures is essential in research and development. It is also a prerequisite in process control and quality assurance in industry. The knowledge of the geometrical dimensions of structures in most cases is the base, to which other physical and chemical properties are linked. Quantitative measurements require reliable and stable... |
 | Trends in Nanoscale Mechanics: Analysis of Nanostructured Materials and Multi-Scale Modeling (ICASE/LaRC Interdisciplinary Series in Science and Engineering) An outstanding feature of this book is a collection of state-of-the-art reviews written by leading researchers in the nanomechanics of carbon nanotubes, nanocrystalline materials, biomechanics and polymer nanocomposites. The structure and properties of carbon nanotubes, polycrystalline metals, and coatings are discussed in great details. The book is an exceptional resource on multi-scale... |
 | Design for Manufacturability and Yield for Nano-Scale CMOS (Series on Integrated Circuits and Systems) by Charles Chiang, Jamil Kawa Design for Manufacturability and Yield for Nano-Scale CMOS walks the reader through all the aspects of manufacturability and yield in a nano-CMOS process and how to address each aspect at the proper design step starting with the design and layout of standard cells and how to yield-grade libraries for critical area and lithography artifacts through place and route, CMP model based simulation and... |
 | Nanoscale Phenomena in Ferroelectric Thin Films (Multifunctional Thin Film Series) Nanoscale Phenomena in Ferroelectric Thin Films presents the recent advances in the field of nanoscale science and engineering of ferroelectric thin films. It consists of two main parts: electrical characterization in nanoscale ferroelectric capacitor, and nano domain manipulation and visualization in ferroelectric materials. Well-known leading experts both in relevant academia and industry over... |
| © 2008 BrightSurf.com |