Featured Research

from universities, journals, and other organizations

Gold Can Get Harder, Not Softer, When Heated To High Temperatures

Date:
January 26, 2009
Source:
University of Toronto
Summary:
Common sense tells us that when you heat something up it gets softer, but scientists have now demonstrated the exact opposite. The gold was heated at rates too fast for the electrons absorbing the light energy to collide with surrounding atoms and lose energy, researchers explain.

Illustration of the phenomenon.
Credit: U of T

Common sense tells us that when you heat something up it gets softer, but a team of researchers, led by University of Toronto chemistry and physics professor R.J. Dwayne Miller, has demonstrated the exact opposite. Their findings will be published online in the journal Science on January 22.

“It is counter-intuitive but the gold got harder instead of softer," says Miller. Can you imagine a blacksmith heating up gold to pound it thinner, only to find it got harder? But we heated the gold at terrific heating rates – greater than 1 billion million degrees per second – that approach the temperature of the interior of stars.”

The gold was heated at rates too fast for the electrons absorbing the light energy to collide with surrounding atoms and lose energy,” he explains. “This means the electrons are on average further away from the atomic nucleus and there is less screening of the positive nuclear charge by these heated electrons. The bonds between atoms actually got stronger.

“A gold crystal consists of gold ions and weakly bound electrons which screen the repulsive forces between the ions,” explains lead author Ralph Ernstorfer, a former postdoctoral research fellow with Prof. Miller, who is now at the Max-Planck Institute for Quantum Optics in Garching and the TU Munich, Germany. As a result, there are attractive forces between ions. In contrast to many other materials, heating the electrons in gold with an ultrashort laser pulse makes the forces between the ions stronger, resulting in a harder lattice with an increased melting point.

“The effect of bond hardening in gold has been theoretically predicted. Now we have actually observed it for the first time,” says Ernstorfer.

The researchers employed a technique called ‘femtosecond electron diffraction’ to make the observation. This technique can be described as a camera for making atomic-level movies. By sending femtosecond pulses of electrons through the thin gold crystal, the atomic motions of the ions were recorded in real time while heating the material with lasers. By measuring the speed of heating, amplitude of the atomic motions, and ultimate melting of the crystal, the laser-induced change of the lattice stability could be inferred.

“We now have an atomic-level view of this rarified state of matter, referred to as warm dense matter, and can relate the observed liquid structure to the increased lattice stability,” says Miller.

In addition to Miller and Ernstorfer, the U of T team includes Thibault Dartigalongue, Maher Harb, Christoph Hebeisen and German Sciaini.


Story Source:

The above story is based on materials provided by University of Toronto. Note: Materials may be edited for content and length.


Cite This Page:

University of Toronto. "Gold Can Get Harder, Not Softer, When Heated To High Temperatures." ScienceDaily. ScienceDaily, 26 January 2009. <www.sciencedaily.com/releases/2009/01/090122141152.htm>.
University of Toronto. (2009, January 26). Gold Can Get Harder, Not Softer, When Heated To High Temperatures. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2009/01/090122141152.htm
University of Toronto. "Gold Can Get Harder, Not Softer, When Heated To High Temperatures." ScienceDaily. www.sciencedaily.com/releases/2009/01/090122141152.htm (accessed July 30, 2014).

Share This




More Matter & Energy News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

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
China's Drone King Says the Revolution Depends on Regulators

China's Drone King Says the Revolution Depends on Regulators

Reuters - Business Video Online (July 30, 2014) Comparing his current crop of drones to early personal computers, DJI founder Frank Wang says the industry is poised for a growth surge - assuming regulators in more markets clear it for takeoff. Jon Gordon reports. Video provided by Reuters
Powered by NewsLook.com
3Doodler Bring 3-D Printing to Your Hand

3Doodler Bring 3-D Printing to Your Hand

AP (July 30, 2014) 3-D printing is a cool technology, but it's not exactly a hands-on way to make things. Enter the 3Doodler: the pen that turns you into the 3-D printer. AP technology writer Peter Svensson takes a closer look. (July 30) Video provided by AP
Powered by NewsLook.com
Climate Change Could Cost Billions, According To White House

Climate Change Could Cost Billions, According To White House

Newsy (July 29, 2014) A report from the White House warns not curbing greenhouse gas emissions could cost the U.S. billions. Video provided by Newsy
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