|A NASA engineer has achieved yet another milestone in his quest to advance an emerging super-black nanotechnology that promises to make spacecraft instruments more sensitive without enlarging their size.|
A team led by John Hagopian, an optics engineer at NASA’s Goddard Space Flight Center in Greenbelt, Md., has demonstrated that it can grow a uniform layer of carbon nanotubes through the use of another emerging technology called atomic layer deposition or ALD. The marriage of the two technologies now means that NASA can grow nanotubes on three-dimensional components, such as complex baffles and tubes commonly used in optical instruments.
|John Hagopian |
Image Source: NASA Goddard/Chris Gunn
For five years, Hagopian and his team have made significant strides applying the carbon-nanotube technology to a number of spaceflight applications, including, among other things, the suppression of stray light that can overwhelm faint signals that sensitive detectors are supposed to retrieve.
In the research, Hagopian tuned the nano-based super-black material, making it ideal for this application, absorbing on average more than 99 percent of the ultraviolet, visible, infrared and far-infrared light that strikes it — a never-before-achieved milestone that now promises to open new frontiers in scientific discovery. The material consists of a thin coating of multi-walled carbon nanotubes about 10,000 times thinner than a strand of human hair.
The NASA team now grows these forests of vertical carbon tubes on commonly used spacecraft materials, such as titanium, copper and stainless steel. Tiny gaps between the tubes collect and trap light, while the carbon absorbs the photons, preventing them from reflecting off surfaces. Because only a small fraction of light reflects off the coating, the human eye and sensitive detectors see the material as black.
|Image credit: Wikipedia)|
For ALD, technicians do this by placing a component or some other substrate material inside a reactor chamber and sequentially pulsing different types of gases to create an ultra-thin film whose layers are literally no thicker than a single atom. Once applied, scientists then are ready to actually grow the carbon nanotubes.
“The samples we’ve grown to date are flat in shape,” Hagopian explained. “But given the complex shapes of some instrument components, we wanted to find a way to grow carbon nanotubes on three-dimensional parts, like tubes and baffles. The tough part is laying down a uniform catalyst layer. That’s why we looked to atomic layer deposition instead of other techniques, which only can apply coverage in the same way you would spray something with paint from a fixed angle.”
"Our goal of ultimately applying a carbon-nanotube coating to complex instrument parts is nearly realized,” said Hagopian.
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