TAGS: Aerospace Coatings Industrial Coatings Sustainability / Natural Coatings
Sandia National Laboratories has developed a coating that protects satellites, instruments and drivers in danger of fast-moving debris. The coatings offer many other possibilities as well.
Layered Nanocomposite to Withstand Harsh Conditions
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A material that can survive a variety of insults — mechanical, shock and X-ray — can be used to withstand harsh environmental conditions,” said Sandia researcher Guangping Xu, who led development of the new coating.
“That material has not been readily available. We believe our layered nanocomposite, mimicking the structure of a seashell, is that answer.”
Most significantly, Xu said, “
The self-assembled coating is not only lightweight and mechanically strong, but also thermally stable enough to protect instruments in experimental fusion machines against their own generated debris where temperatures may be about 1,500 C. This was the initial focus of the work.”
The inexpensive, environmentally friendly shield is light enough to ride into space as a protective layer on satellites because comparatively little material is needed to achieve the same resilience as heavier but less effective shielding currently in use to protect against collisions with space junk.
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Satellites in space get hit constantly by debris moving at a few kilometers per second, the same velocity as debris from Z,” McCoy said. “With this coating, we can make the debris shield thinner, decreasing weight.”
Dramatic Cost Reduction Anticipated
According to Guangping, the material cost to fabricate a 2-inch diameter coating of the new protective material, 45 millionths of a meter and microns thick, is only 25 cents.
In contrast, a beryllium wafer — the closest match to the thermal and mechanical properties of the new coating, and in use at Sandia’s Z machine and other fusion locations as protective shields — costs $700 at recent market prices for a 1-inch square, 23-micron-thick wafer, which is 3,800 times more expensive than the new film of same area and thickness.
Both coatings can survive temperatures well above 1,000 C, but a further consideration is that the new coating is environmentally friendly. Only ethanol is added to facilitate the coating process. Beryllium creates toxic conditions, and its environs must be cleansed of the hazard after its use.
Strengthening the Sandia Coating
Seashell-like coatings initially tested at Sandia varied between a few to 13 layers.
These alternating materials were pressed against each other after being heated in pairs, so their surfaces crosslinked. Tests showed that such interwoven nanocomposite layers of silica with the burnt sugar, known as carbon black after pyrolysis, are 80% stronger than silica itself and thermally stable to an estimated 1,650 C.
Later sintering efforts showed that layers, self-assembled through a spin-coating process, could be batch-baked and their individual surfaces still crosslinked satisfactorily, removing the tediousness of baking each layer. The more efficient process achieved very nearly the same mechanical strength.
Research into the coating was funded by ASAP to develop methods to protect diagnostics and test samples on Z and on next-generation pulsed power machines from flying debris.
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This coating qualifies,” Frye-Mason said.
Source: Sandia National Laboratories