Tuesday, December 15, 2009

Nanocrystals Increase Insulator Value of a Pure Vacuum

Vacuum insulator linings are about to get an upgrade.


"Vacuum's emptiness doesn't just pose a problem for space travelers -- a vacuum lining is also one of the best known insulators on Earth, and may help keep those holiday drinks and soups warm in your thermos. Now scientists have found that layering photonic crystals within the vacuum lining can even prevent heat loss from invisible infrared radiation.

Heat typically travels via methods such as convection and conduction, which both require a material medium, which vacuum conveniently lacks. But heat can also transfer through infrared radiation, and can pass through a vacuum lining to a thermos's outer wall.
The scientists stacked 10 layers of photonic crystals into a tiny 100-micron-thick structure. For size comparisons, keep in mind that 1,000 microns make up a single millimeter.

Tests on the new insulator showed that heat transfer does not rely on layer thickness, but only on how fast light can travel through the material."

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