The National Institute of Standards and Technology (NIST) has developed an ultra-black, multiwalled carbon nanotube coating that can be sprayed on to a substrate such as copper. The rugged coating can withstand high temperatures without melting or oxidizing. One of the first applications for the coating was a NIST-designed power meter for calibrating high-power lasers used by the U.S. military to defuse unexploded mines. The new laser power meter will be used to measure the light emitted by 10-kW laser systems. Light focused from a 10 kW laser is more than a million times more intense than sunlight reaching the Earth.

Until now, NIST-built power meters were barely portable and operated slowly. NIST claims that the new power meter is much smaller—about the size of a crock pot rather than a refrigerator. It also features a new design that enables it to make continuous power measurements. According to a NIST description of the meter, light is absorbed by the power meter in a cone-shaped copper cavity, where a spinning mirror directs the light over a large area and distributes the heat uniformly. The cavity is lined with multiwalled carbon nanotubes held together by a potassium silicate (water glass) binder, and surrounded by a water jacket. The coating absorbs light and converts it to heat. The resulting rise in water temperature generates a current, which is measured to determine the power of the laser.

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