Building better structural materials: Nickel nanocrystals under pressure

Dec 13, 2012

When materials are stressed, they eventually change shape. Initially these changes are elastic, and reverse when the stress is relieved. When the material's strength is exceeded, the changes become permanent. This could result in the material breaking or shattering, but it could also re-shape the material, such as a hammer denting a piece of metal. Understanding this last group of changes is the focus of research from a team including Carnegie's Ho-kwang "Dave" Mao.

Their breakthrough research on the behavior of nickel under intense pressure is published December 14 by Science. Their findings could help physicists and engineers create stronger, longer-lasting materials. It can also help earth scientists understand tectonic events and seismicity.

It is believed that permanent changes to metallic grains when under pressure are associated with the movement of structural irregularities in the grains, called dislocations. But the deformation of has been controversial because it was thought that below a certain grain size, the structural irregularities would not form and the deformation would be dictated by motions of the boundary between grains instead. According to , this critical limit would occur in nanocrystals at sizes between 10 and 30 nm in size.

Experimental work on nanocrystals under pressure has been limited by technical hurdles. But new capabilities using a technique called radial diamond anvil cell x-ray diffraction has opened the door to moving beyond computer modeling and into the lab.

The team, led by Bin Chen of the Lawrence Berkeley National Laboratory, was able to show that the activities of the structural irregularities that accompany deformation were occurring even in nickel nanocrystals of 3 in size when they were compressed to higher than 183,000 times normal atmospheric pressure (18.5 gigapascals). This demonstrates that so-called dislocation-associated deformation is a function of both pressure and particle size, as previously thought, but that the particle size can be smaller than computer modeling had anticipated.

"These findings help constrain the fundamental physics of deformation under pressure on a very small scale," Mao said. "They also demonstrate the importance of the radial x-ray diffraction tool for helping us understand these processes."

Explore further: Modification of structural composite materials to create tailored lenses

Related Stories

Stressed nanomaterials display unexpected movement

Feb 23, 2010

Johns Hopkins researchers have discovered that, under the right conditions, newly developed nanocrystalline materials exhibit surprising activity in the tiny spaces between the geometric clusters of atoms ...

New form of superhard carbon observed

Oct 11, 2011

An amorphous diamond – one that lacks the crystalline structure of diamond, but is every bit as hard – has been created by a Stanford-led team of researchers.

Model simulates atomic processes in nanomaterials

Mar 01, 2007

Researchers from MIT, Georgia Institute of Technology and Ohio State University have developed a new computer modeling approach to study how materials behave under stress at the atomic level, offering insights that could ...

Materials science: Perfecting the defect

May 03, 2012

Strong metals have a tendency to be less ductile — unless the metal happens to be a peculiar form of copper known as nanotwinned copper. The crystal structure of nanotwinned copper exhibits many closely-spaced ...

Recommended for you

Novel technique opens door to better solar cells

Apr 14, 2014

A team of scientists, led by Assistant Professor Andrivo Rusydi from the Department of Physics at the National University of Singapore's (NUS) Faculty of Science, has successfully developed a technique to ...

Probing metal solidification nondestructively

Apr 14, 2014

(Phys.org) —Los Alamos researchers and collaborators have used nondestructive imaging techniques to study the solidification of metal alloy samples. The team used complementary methods of proton radiography ...

Glasses strong as steel: A fast way to find the best

Apr 13, 2014

Scientists at Yale University have devised a dramatically faster way of identifying and characterizing complex alloys known as bulk metallic glasses (BMGs), a versatile type of pliable glass that's stronger than steel.

User comments : 0

More news stories

Glasses strong as steel: A fast way to find the best

Scientists at Yale University have devised a dramatically faster way of identifying and characterizing complex alloys known as bulk metallic glasses (BMGs), a versatile type of pliable glass that's stronger than steel.

Melting during cooling period

(Phys.org) —A University of Maine research team says stratification of the North Atlantic Ocean contributed to summer warming and glacial melting in Scotland during the period recognized for abrupt cooling ...