RUDN physicists discover that black carbon, activated carbon and shungite can replace graphene

RUDN physicists have discovered graphene structures in the samples of graphite-like amorphous carbon—black carbon, activated carbon and shungite. This means that cheap and accessible amorphous carbon can be used in certain cases instead of pure graphene, which is expensive and hard to produce. Their article is published in the Journal of Non-Crystalline Solids.

Graphene is a carbon sheet one atom thick. It is 100 times stronger than steel, highly flexible, and has high thermal and electric conductivity. Because of its characteristics, it could someday replace silicon in electronics. However, graphene preparation from graphite is technologically difficult and is not ready for mass production.

Nadezhda Popova, associate professor at the Institute of Physical Research and Technologies of RUDN, explored the properties of amorphous compounds of carbon such as activated carbon, black carbon and others in order to find out whether these materials can be used in nanotechnologies alongside graphene, fullerenes and carbon nanotubes.

Shungite and anthraxolite (natural amorphous carbons), and artificial black carbon CB624 и CB632 were chosen as a proof of concept.

Amorphous carbons do not have rigid crystalline texture as diamond or graphite. However, graphene cells occur in their texture. The authors state that graphene content in environmental samples is enough to use these materials as a substitute of artificial graphene in nanotechnology.

However, atomic impurities such as oxygen and hydrogen affect the growth and size of graphene cells. The size of graphene cells in examined samples of amorphous carbon is more than twice smaller (2-8 nm) than in artificial (6,4 и 13,7 nm) due to hydrogen atoms existence. This graphene is less prone to deformation and defects. Carbon fraction in environmental samples was 2-5% less (88,5%-95,6%) than in artificial (90,7%-99,6%). The physics came to the conclusion that researched environmental samples of amorphous carbon can become an alternative of artificial graphene despite of the small size of their cells.

Having researched amorphous carbons, physicists made a conclusion that the used methods of carbon content assaying are imperfect. For example, gravimetric method (TGA) introduced not only carbon, but also impurities. Analysis showed that carbon fraction in the sample was smaller than the real fraction. The level of carbon of 99,95% declared by producers was unachievable. Widely used methods of oxygen assessment in carbon-containing materials, for example, electronic spectroscopy (XPS), overestimated its content. These drawbacks of assaying methods have a negative influence on amorphous carbon production.

Now because of the discovery of graphene textures in well-known materials: black carbon, activated carbon, shungite, and anthraxolite, nanotechnology has the substitute to artificial graphene.

More information:
Yevgeny A. Golubev et al. sp amorphous carbons in view of multianalytical consideration: Normal, expeсted and new, Journal of Non-Crystalline Solids (2019). DOI: 10.1016/j.jnoncrysol.2019.119608

Provided by RUDN University