Nature:
Normally, when water comes in contact with a very hot metal
surface, a layer of water vapor is formed that keeps the water
from making direct contact with the metal. When the surface
cools below a certain pointâmdash;the
Leidenfrost temperatureâmdash;the vapor no
longer supports the water, which touches the surface and boils
explosively. Engineers from the Clean Combustion Research
Center at the King Abdullah University of Science and
Technology in Thuwal, Saudi Arabia, led by Ivan Vakarelski,
coated metal spheres with a commercial material that made the
surface of the spheres rough and superhydrophobic. When they
heated the spheres and submerged them in water, the layer of
water vapor that was created never dissipated as the spheres
cooled. A test with the same material coating metal cylinders
that were heated from within resulted in the cylinders reaching
250 °C, while untreated ones reached only 106 °C. The
vapor layer formed by the uncoated metal was unstable and
allowed liquid water to contact the metal and boil away, thus
keeping the cylinder cool.
