Nanocrystals Are Hot

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$The melting point of germanium nanocrystals embedded in silica glass was measured inside a transmission electron microscope. Electron diffraction patterns from the crystalline lattice structure (bright rings) persist until the temperature is more tha ...$

The melting point of germanium nanocrystals embedded in silica glass was measured inside a transmission electron microscope. Electron diffraction patterns from the crystalline lattice structure (bright rings) persist until the temperature is more than 200 degrees Kelvin above the melting point of germanium in bulk, which is approximately 1211 K. When the nanocrystal melts, the diffraction patterns disappear.

Scientists at the Department of Energy's Lawrence Berkeley National Laboratory have discovered that nanocrystals of germanium embedded in silica glass don't melt until the temperature rises almost 200 degrees Kelvin above the melting temperature of germanium in bulk. What's even more surprising, these melted nanocrystals have to be cooled more than 200 K below the bulk melting point before they resolidify. Such a large and nearly symmetrical "hysteresis" — the divergence of melting and freezing temperatures above and below the bulk melting point — has never before been observed for embedded nanoparticles.

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All News summaries for October 09, 2006