Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Nanoparticles get svelter in the heat: Scientists have discovered magnetic nanoparticles that, unlike most materials, shrink when they are heated

Figure 1: The distance between the white spots in this electron diffraction pattern are inversely proportional to the distance between atoms in the CuO nanoparticles and will move closer together or further apart depending on whether the nanoparticles expand or contract, respectively, when they are heated.
Figure 1: The distance between the white spots in this electron diffraction pattern are inversely proportional to the distance between atoms in the CuO nanoparticles and will move closer together or further apart depending on whether the nanoparticles expand or contract, respectively, when they are heated.

Abstract:
Materials typically expand when they are heated, which is why the concrete slabs in sidewalks can buckle on a hot day. Now, Kenichi Kato of the RIKEN SPring-8 Center in Harima and colleagues at Saga University and Japan's National Institute of Advanced Industrial Science and Technology have identified several materials that defy this common rule of thumb. In a paper published in Nature Nanotechnology, the team reports that nanoparticles of cupric oxide (CuO) actually shrink when they are heated1.

Nanoparticles get svelter in the heat: Scientists have discovered magnetic nanoparticles that, unlike most materials, shrink when they are heated

Japan | Posted on February 19th, 2009

To make the nanoparticles, Kato and colleagues started with large crystals of CuO and milled them down to particles approximately 5 nanometers in size. Using x-ray and electron diffraction (Fig. 1), they measured the average distances between the atoms that make up CuO and how these distances vary with temperature. Starting from low temperatures (-253.15 °C), they found that CuO shrinks by about 1% from its original volume when it is heated to 200 K (-73.15 °C)—an effect that is several times larger than what is found in other materials that shrink when heated. With further heating, the nanoparticles started to expand.

The reason that materials, in general, expand when they are heated is that the atoms start to vibrate around their equilibrium positions as they gain energy and move away from one another. The opposite case—negative thermal expansion—can occur if the vibrations of some atoms actually pull other atoms together. For example, if an oxygen atom that bonds two metal atoms starts to vibrate perpendicular to this bond, it will pull the two metal atoms closer together. However, Kato and his colleagues believe that the negative thermal expansion in CuO nanoparticles may be related to this material's magnetic properties, since the crossover from normal to negative thermal expansion in the nanoparticles occurs at the same temperature that the CuO orders magnetically.

This effect is also found in nanoparticles of the magnetic material manganese (II) fluoride (MnF2). "As the temperature is cooled and CuO orders magnetically, the magnetic Cu atoms begin to be aligned like a pair of bar magnets," explains Xu-Guang Zheng from Saga University. "The two bar magnets push each other so that the distance between the two magnetic atoms expands." Conversely, as the temperature increases, the Cu atoms push against each other less, leading to negative thermal expansion. Since this is a general argument, the team expects they will be able to find other magnetic materials in nanoparticle form that will exhibit negative thermal expansion.

Reference
Zheng, X.G., Kubozono, H., Yamada, H., Kato, K., Ishiwata, Y. & Xu, C.N. Giant negative thermal expansion in magnetic nanocrystals. Nature Nanotechnology 3, 724-726 (2008).

The corresponding author for this highlight is based at the RIKEN Structural Materials Science Laboratory

####

For more information, please click here

Copyright © Riken

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

article

Related News Press

News and information

NanoTechnology for Defense (NT4D) October 22nd, 2014

Mechanism behind nature's sparkles revealed October 22nd, 2014

TARA Biosystems and Harris & Harris Group Form Company to Improve Safety and Efficacy of New Therapies October 22nd, 2014

Researchers patent a nanofluid that improves heat conductivity October 22nd, 2014

Discoveries

Mechanism behind nature's sparkles revealed October 22nd, 2014

Researchers patent a nanofluid that improves heat conductivity October 22nd, 2014

‘Designer’ nanodevice could improve treatment options for cancer sufferers October 22nd, 2014

Detecting Cancer Earlier is Goal of Rutgers-Developed Medical Imaging Technology: Rare earth nanocrystals and infrared light can reveal small cancerous tumors and cardiovascular lesions October 21st, 2014

Materials/Metamaterials

Researchers patent a nanofluid that improves heat conductivity October 22nd, 2014

Materials for the next generation of electronics and photovoltaics: MacArthur Fellow develops new uses for carbon nanotubes October 21st, 2014

Super stable garnet ceramics may be ideal for high-energy lithium batteries October 21st, 2014

Could I squeeze by you? Ames Laboratory scientists model molecular movement within narrow channels of mesoporous nanoparticles October 21st, 2014

Announcements

NanoTechnology for Defense (NT4D) October 22nd, 2014

Mechanism behind nature's sparkles revealed October 22nd, 2014

TARA Biosystems and Harris & Harris Group Form Company to Improve Safety and Efficacy of New Therapies October 22nd, 2014

Researchers patent a nanofluid that improves heat conductivity October 22nd, 2014

NanoNews-Digest
The latest news from around the world, FREE





  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE