by Txchnologist Staff
Using extremely powerful x-rays, German materials scientists have discovered that molten liquid metals exhibit unusual properties as they cool.
The Saarland University researchers levitated positively charged molten metal droplets in an electric field generated between two electrodes within a vacuum chamber.
Hitting the drops with x-rays as they cooled, the team observed that liquid metal transitions to another liquid state with equal density but much more order before it crystallizes and turns solid.
“By demonstrating this structural modification, we have been able to show that within the liquid phase a ‘fragile’ less-ordered liquid is transformed into a so-called ‘strong’ liquid with a higher degree of order,” said Shuai Wei, a doctoral student in the university’s metallic materials group. “The results help to provide us with a better understanding of how a material reorganizes when it undergoes cooling.”
They saw this unusual behavior as droplets cooled from around 1,700 degrees F to 980 degrees F. Earlier work indicated that liquid metals’ viscosity and entropy changed as it cooled, but the details remained in question because of experimental difficulties in slowing crystal formation during solidification.
Wei says that such insight into how industrially important metals transform as they cool could lead to advances in higher performance materials. The group’s work was published in the July 1 edition of Nature Communications.
Top Image: A metal droplet in electrostatic levitation. The hot droplet is suspended in vacuum between two electrodes. During cooling and heating its structure is continuously illuminated with synchrotron radiation and documented. Photo courtesy Institute of Materials Physics in Space at the German Aerospace Center (DLR) in Cologne.
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