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September 13 (UPI) – MIT's material engineers produced the blackest black material to date, 10 times darker than previous black materials.
The material is composed of microscopic carbon filaments. In the lab, scientists created a carbon nanotube forest vertically aligned on a chlorine-etched aluminum foil substrate. Leaf-based carbon trees capture 99.96% of incoming light, a new record.
The researchers described the new material published this week in ACS Applied Materials and Interfaces.
The authors of the new document do not expect to keep the record for a very long time. According to the creators of the material, scientists will design a material capable of absorbing 100% of the light.
"Our material is 10 times darker than anything that has ever been reported, but I think the darkest black is a constantly moving target," said Brian Wardle, professor of aeronautics and aeronautics. astronautics at MIT, in a press release. "Someone will find a darker material and eventually we will understand all the underlying mechanisms and will be able to properly design the ultimate black."
To demonstrate the capacity of the material, the scientists covered a nanotube mat with a natural yellow diamond of 16.78 carats, which caused the disappearance of the diamond.
"There are optical and space science applications for very black materials, and of course, artists are interested in black, which goes back well before the Renaissance," Wardle said.
Originally, Wardle and his research team sought to improve the electrical and thermal properties of conductive materials such as aluminum by growing nanotubes.
When aluminum is exposed to the air, an oxide layer is formed. The layer acts as an insulator, blocking the flow of electricity and thermal energy. During the experiments, the researchers realized that the same ingredients he used for growing carbon nanotubes, salt, baking soda and detergent could be used to remove the oxide layer.
When exposed to salt, chloride ions eat away at the aluminum surface.
"This engraving process is common for many metals," said Kehang Cui, a postdoc at MIT, now a professor at Shanghai Jiao Tong University in Japan. "For example, ships suffer from chlorine-based seawater corrosion, now we use this process to our advantage."
Wardle and Cui were able to remove the oxide layer by soaking the aluminum in saline solution. After removing the layer, scientists have grown nanotubes on etched aluminum inside an oven. Surface etching of aluminum has facilitated the growth of nanotubes at much lower temperatures.
When they finished cooking aluminum, they were surprised to find an extremely dark material. The final product had improved electrical and thermal properties, but it also had unexpected optical properties.
"I remember noticing how black it was before growing carbon nanotubes, and then after growing, it seemed even darker," Cui said. "Then I thought I should measure the optical reflectance of the sample."
The material absorbed 99.96% of incoming light from all angles.
The researchers suggest that additional research is needed to determine exactly how the material absorbs so much light.
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