This is nifty

At Science Alert, report of some interesting materials science advances.  We already knew that metallic vanadium dioxide (VO2) switches from a visually transparent insulator to an electrically conductive metal at 152 degrees F. Between 86 and 140F, it also reflects infrared light while remaining visually transparent.

Now we have learned that, when VO2 reaches the temperature at which it switches over to electrical conduction, it remains an unexpectedly bad conductor of heat. Apparently this is because its free electrons move in unison instead of primarily bouncing back and forth. Also, mixing VO2 with other materials adjusts the amount of both electricity and heat that it conducts. These characteristics together suggest that VO2 mixtures can be devised to do things like coat windows, so that they conduct heat in hot weather but insulate it in cold weather; VO2 might also begin to conduct heat away from electric motors after they have been operating long enough to build up heat.

I may have gotten this summary mixed up, particularly which parts follow from the new discoveries and which are old hat.  The linked article is short but worth reading.

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