According to the MIT researchers, the new material has tremendous potential in the optical field, where it can be deployed as a lightweight optical blinder, trapping unwanted light from entering optical systems.
“Optical instruments like cameras and telescopes have to get rid of unwanted glare, so you can see what you want to see,” said astrophysicist and Nobel laureate John Mather. “Would you like to see an Earth orbiting another star? We need something very black.… And this black has to be tough [enough] to withstand a rocket launch. Old versions were fragile forests of fur, but these are more like pot scrubbers —built to take abuse.”
To develop this robust blackest black, engineers began by exposing aluminum foil to salt water in order to etch away the metal’s oxide later. Once stripped, the foil was paced in an oxygen-free environment to prevent reoxidization and then brought to temperature in an oven.
Within the oven, the foil was cajoled into sprouting carbon nanotubes via chemical vapor deposition, a process usually reserved for the superconductor industry, where finely tuned gas combinations infiltrate a vacuum and deposit their chemical structure onto a target solid.
While engineers expected that their process would promote the growth of CNTs, they were surprised by the richness of the color they achieved, and at the relatively low temperature (100°C) at which the reaction took place.
“I remember noticing how black it [the aluminum foil] was before growing carbon nanotubes on it, and then after growth, it looked even darker,” said Kehang Cui an MIT postdoctoral student. “So, I thought I should measure the optical reflectance of the sample.”
After inspecting the sample by exposing it to light from every angle, Cui discovered that they had developed a material that transformed what would otherwise be a very reflective material into one that resembled a deep void.
Since the publication of its results, the MIT team has received numerous requests for the material from aerospace firms looking to employ the material in their projects, making it seem likely that the material will be traveling from the lab to the stars remarkably fast.