Scientists create the darkest-ever material

The material is made from multiple carbon nanotubes on an aluminium foil base.

The new absolute black material is a joint US-Chinese development. With this invention, scientists from the Massachusetts Institute of Technology (MIT) and Shanghai University have managed to achieve a record low measure of optical reflectance of approximately 10-5. An article from the authors of the study has been published in ACS Applied Materials & Interfaces.

Materials that absorb almost all the light directed at them are used in science (for example, in the creation of gravitational-wave interferometers) and art. 

The method of creating this new material is based on the surface activation of aluminium substrates.  Scientists start by removing the oxide film on the surface. This is done by processing the substrate with a 10% solution of NaCl, followed by treating it with ultrasound. As a result, they obtain a substance with a porous structure which can be supplemented with special catalysts - iron and cobalt salts - that are required to start growing a layer of carbon nanotubes on the surface. 

The key part of this process, the formation of the nanotubes, occurs when the substrate is heated up to a temperature of 400–600 °C in a chamber that contains argon, acetylene and carbon dioxide. As a result, the carbon atoms settle on the substrate in a nanotube structure. 

Optical tests of the material have proved that it is many times darker than its counterparts, meaning that it reflects much less light. It’s worth noting that the optical reflectance of this material is practically independent from the angle at which the light hits it.