A New “Blackest Black” is Discovered

Josie K., Staff Writer

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Engineers at the Massachusetts Institute of Technology unveiled the “blackest black” — which is “10 times blacker than anything that has previously been reported.”

“The material is made from vertically aligned carbon nanotubes, or CNTs — microscopic filaments of carbon, like a fuzzy forest of tiny trees, that the team grew on a surface of chlorine-etched aluminum foil. The foil captures at least 99.995 percent of any incoming light, making it the blackest material on record,” a statement from MIT said.

A yellow diamond coated in the material appeared to completely disappear — making it look like a dark “void.”

When engineers created the material, however, it was completely by accident.

Brian Wardle, professor of aeronautics and astronautics at MIT, and MIT postdoc Kehang Cui, now a professor at Shanghai Jiao Tong University, were “experimenting with ways to grow carbon nanotubes on electrically conducting materials such as aluminum, to boost their electrical and thermal properties” when they were confronted with a problem.

A layer of oxide coats aluminum when it is exposed to air, acting as an insulator and blocking electricity and heat. This inhibited the material’s ability to act as a conductor.

The team soaked the aluminum in saltwater, removing the oxide layer. After going through a detailed process that involved placing aluminum in the oven to remove the layer, engineers found the material’s ability to conduct heat and electricity were improved — with the surprising color.

“I remember noticing how black it was before growing carbon nanotubes on it, and then after growth, it looked even darker,” Cui said in a statement. “So I thought I should measure the optical reflectance of the sample.”

The material was found to absorb 99.995 percent of all light — at every angle and with imperfections like bumps or ridges — which is 10 times more than any other known material.

Researchers detailed the full results in a study published September 12 in the journal ACS-Applied Materials.

The material could be used in cameras or telescopes to eliminate unwanted glares, astrophysicist and Nobel laureate John Mather, who was not involved in the experiment, said in a statement.

Mather is exploring uses for the material.

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