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 24, 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 24, 2014).

Share This




More Matter & Energy News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) Video provided by AP
Powered by NewsLook.com
Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
Powered by NewsLook.com
Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
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