Tuesday, July 23, 2013

Super-Black is now 3-D

No, it’s not a new super-hero jumping from the comic book world. NASA has developed a super-black, a blacker than black material that is fashioned out of carbon nanotubes and absorbs 99% of various forms of light such as far-infrared light, visible and regular infrared, as well as ultraviolet light. Why is this important? Consider its use in telescopes. An incredibly sensitive instrument that is tasked with picking out a handful of photons in a universe made almost entirely of light. And there are other uses. Think stealth vehicles that are better able to evade detection. Earth Scientists can also benefit in their studies of the ocean or the atmosphere.

The tool originally used by instrument developers was a paint brush. They would apply black paint to baffles and other components to prevent light from bouncing off light sources. While the black paint would assist in absorbing 90% of the stray light, often the amount not absorbed would overwhelm the faint signal that can provide the necessary data. In addition black paints do not handle cryogenic temperatures well.

NASA was able to develop a method of applying this new super-black material through growth on flat pieces of silicon. Unfortunately this was not very helpful as most of the instruments that this was needed on consisted of many different surfaces, complex shapes with rounded edges. To solve this NASA turned to a number of things. First they needed to use the process ALD (Atomic Layer Deposition) which would allow the deposit of an ultra-thin catalyst layer of iron oxide. Next the object is baked in an oven at about 750 degrees Celsius dousing it in carbon-containing feedstock gas. This would make the oxide particles break apart the gas molecules and the edges of the oxide gather the carbon atoms creating a nanotube.

The super-black material presents itself in a super thin coating of multi-walled carbon nanotubes. How thin? 10,000 times thinner than a strand of human hair. This means that a three dimensional object can have the huge benefits with little size interference and they are not done yet. NASA continues to works on and improve this process for use in space flight. To quote one of the Goddard scientists; It's robust, lightweight, and extremely black.

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