Featured Research

from universities, journals, and other organizations

Nanocrystals not small enough to avoid defects

Date:
December 14, 2012
Source:
DOE/Lawrence Berkeley National Laboratory
Summary:
A team of researchers has shown that contrary to computer simulations, the tiny size of nanocrystals is no safeguard from defects. Studies at Berkeley Lab's Advanced Light Source show that dislocations can form in the finest of nanocrystals when stress is applied.

Stress-induced deformation of nanocrystalline nickel reflects the dislocation activity observed by researchers at Berkeley Lab’s Advanced Light Source using a radial diamond-anvil-cell X-ray diffraction experimental station.
Credit: Image courtesy of NDT Education Resource Center

Nanocrystals as protective coatings for advanced gas turbine and jet engines are receiving a lot of attention for their many advantageous mechanical properties, including their resistance to stress. However, contrary to computer simulations, the tiny size of nanocrystals apparently does not safeguard them from defects.

In a study by researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab)and collaborators from multiple institutions, nanocrystals of nickel subjected to high pressure continued to suffer dislocation-mediated plastic deformation even when the crystals were only three nanometers in size. These experimental findings, which were carried out at Berkeley Lab's Advanced Light Source (ALS), a premier source of X-rays and ultraviolet light for scientific research, show that dislocations can form in the finest of nanocrystals when stress is applied.

"We cannot ignore or underestimate the role of dislocations -- defects or irregularities -- in fine nanocrystals as external stress can change the entire picture," says Bin Chen, a materials scientist with the ALS Experimental Systems Group who led this research. "Our results demonstrate that dislocation-mediated deformation persists to smaller crystal sizes than anticipated, primarily because computer models have not given enough consideration to the effects of external stress and grain boundaries."

Chen is the lead and corresponding author of a paper in Science describing this work. The paper is titled "Texture of Nanocrystalline Nickel: Probing the Lower Size Limit of Dislocation Activity." Co-authoring this paper were Katie Lutker, Selva Vennila Raju, Jinyuan Yan, Waruntorn Kanitpanyacharoen, Jialin Lei, Shizhong Yang, Hans-Rudolf Wenk, Ho-kwang Mao and Quentin Williams.

Plastic deformation is a permanent change in the shape or size of a material as the result of an applied stress. The likelihood of plastic deformation increases with the presence of dislocations -- defects or irregularities -- within the material's structure. Most materials are made up of small crystals, called "grains," and what happens at the boundaries between these grains is critical to material properties. Based on computer simulations and electron microscopy analysis, the belief has been that dislocation-mediated plastic deformation becomes inactive below a grain size of at least 10 nanometers, and possibly as large as 30 nanometers.

"The idea was that below a critical length scale, dislocation-mediated deformation activity would give way to grain-boundary sliding, diffusion, and grain rotation," Chen says. "However, there were many unresolved questions with regards to whether plasticity in ultrafine nanocrystalline grains could still be generated by dislocations and how pressure might affect the deformational regimes."

To investigate grain size and pressure effects on the plastic deformation of nanometals, Chen and his colleagues used ALS Beamline 12.2.2, a superconducting bend magnet beamline that supports radial diamond-anvil-cell X-ray diffraction experiments. Chen and his co-authors recorded in situ observations under a range of high pressures of texturing (when the crystalline grains have preferred orientations) in stressed polycrystalline nickel samples featuring grain sizes of 500-, 20- and 3-nanometers.

"Substantial texturing was observed at pressures above 3.0 gigapascals for nickel with 500-nanometer grain size and at greater than 11.0 gigapascals for nickel with 20-nanometer grain size," Chen says. "Surprisingly, texturing was also seen in nickel with 3-nanometer grain size when compressed above 18.5 gigapascals. This tells us that under high external pressures, dislocation activity can be extended down to a few-nanometers-length scale."

Chen and his co-authors started with nanocrystalline nickel because its face-center cubic structure remains stable under a wide pressure range. They are now applying their techniques to the study of other nanocrystalline materials, both metals and non-metals.

This research was funded by the National Science Foundation, NASA and the DOE Office of Science. The ALS is a DOE Office of Science national user facility.


Story Source:

The above story is based on materials provided by DOE/Lawrence Berkeley National Laboratory. Note: Materials may be edited for content and length.


Journal Reference:

  1. B. Chen, K. Lutker, S. V. Raju, J. Yan, W. Kanitpanyacharoen, J. Lei, S. Yang, H.-R. Wenk, H.-k. Mao, Q. Williams. Texture of Nanocrystalline Nickel: Probing the Lower Size Limit of Dislocation Activity. Science, 2012; 338 (6113): 1448 DOI: 10.1126/science.1228211

Cite This Page:

DOE/Lawrence Berkeley National Laboratory. "Nanocrystals not small enough to avoid defects." ScienceDaily. ScienceDaily, 14 December 2012. <www.sciencedaily.com/releases/2012/12/121214102704.htm>.
DOE/Lawrence Berkeley National Laboratory. (2012, December 14). Nanocrystals not small enough to avoid defects. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2012/12/121214102704.htm
DOE/Lawrence Berkeley National Laboratory. "Nanocrystals not small enough to avoid defects." ScienceDaily. www.sciencedaily.com/releases/2012/12/121214102704.htm (accessed August 1, 2014).

Share This




More Matter & Energy News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Tesla, Panasonic Ink Deal To Make Huge Battery 'Gigafactory'

Tesla, Panasonic Ink Deal To Make Huge Battery 'Gigafactory'

Newsy (July 31, 2014) The deal will help build a massive battery factory that Tesla says will produce 500,000 lithium batteries by 2020. Video provided by Newsy
Powered by NewsLook.com
Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Smoked: 2015 Ducati Diavel Vs 2014 Chevy Corvette Stingray Drag Race

Smoked: 2015 Ducati Diavel Vs 2014 Chevy Corvette Stingray Drag Race

Cycle World (July 30, 2014) The Bonnier Motorcycle Group presents Smoked; a three part video series. In this episode the 2015 Ducati Diavel takes on the 2014 Chevy Corvette Stingray Video provided by Cycle World
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins