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An encapsulation system developed by ORNL researchers prevents salt hydrates, which are environmentally friendly thermal energy storage materials, from leaking and advances their use in heating and cooling applications. Credit: Andy Sproles/ORNL, U.S. Dept. of Energy

ORNL researchers have developed a novel way to encapsulate salt hydrate phase-change materials within polymer fibers through a coaxial pulling process. The discovery could lead to the widespread use of the low-carbon materials as a source of insulation for a building’s envelope.

Vanadium atoms (blue) have unusually large thermal vibrations that stabilize the metallic state of a vanadium dioxide crystal. Red depicts oxygen atoms.

For more than 50 years, scientists have debated what turns particular oxide insulators, in which electrons barely move, into metals, in which electrons flow freely.