Carbon is known for its extraordinary ability to form a wide variety of structures with vastly different electrical, optical, and morphological properties. In a study published in ACS Nano, scientists report a new pyramidal arrangement of soot nanoparticles on the surface of a carbon filament that could prove very useful for creating electron guns or making surfaces superhydrophobic. Soot micropyramids were observed on the surface of samples of amorphous coal heated in an oxygen-poor atmosphere.
(a) SEM image of the network of micropyramids seen at 45° and (b) hexagonal order of the network seen from above.
(c) High-resolution TEM image of soot nanoparticles self-assembling into a micropyramid.
© Valery Luchnikov.
In addition to the famous nanotubes, fullerenes and graphene, many three-dimensional structures made of carbon have been discovered, such as B. Carbon nanohorns and nanocones, conical microcrystals, carbon whiskers, graphene flowers or vertical graphene. The electrical, optical, and morphological properties of these carbon objects open many possibilities for applications such as electron guns, supercapacitors, ultra-black materials, and superhydrophobic and/or bactericidal coatings.
Scientists from the Institute of Materials Science of Mulhouse (CNRS/University of Haute-Alsace) and the University of Tokyo have recently observed an entirely new type of carbon microstructure: networks of soot micropyramids appearing on the surface of amorphous carbon filaments that are heated in a Atmosphere of argon mixed with a small amount of air. The surface of the samples is covered by a hexagonal network of sharp-tipped micropyramids.
High-resolution transmission electron microscopy imaging reveals that the micropyramids are composed of multilayered carbon nanoparticles, similar to carbon nano-onions. While these soot micropyramids are soft and easily destroyed by touch, the team showed that high-temperature heat treatment can harden them to lock in this new structure.
Upon application of a local electric field, each stabilized carbon micropyramid emits a tunneling current, which opens up the possibility of creating new arrays of electron emitters. The scientists also plan to study the formation of these structures on flat substrates to make them superhydrophobic. These results appeared in the journal ACS Nano.
Reference:
Luchnikov VA, Saito Y, Delmotte L, Dentzer J, Denys E, Malesys V, Josien L, Simon L, Gree S.
Self-assembly of soot nanoparticles on the surface of resistance-heated carbon microtubes in nearly hexagonal arrays of micropyramids
ACS Nano 2023
https://doi.org/10.1021/acsnano.2c04395