Secondary Micro- and Nanostructures on the Surface of Microwave Carbonized Cotton Fibers

The morphology and surface composition of microwave carbonized cotton lint fibers and secondary micro- and nanostructures formed on their surfaces during the carbonization process were studied by the methods of scanning electron microscopy and X-ray microanalysis. During microwave carbonization, the impurity elements existing in the original cotton fibers were shown to move from the central area of the sample to the edge zones and deposit there as continuous phosphorus-containing coatings and micro- and nanostructures of various morphologies and compositions. Phosphorus and calcium were found to be the most difficult impurities to remove. The detected black areas characterize activated carbon comprising no impurity elements. The identified fiber surface structures were characterized by four types: monolithic carbon deposits with a bumpy and lamellar structure, thin transparent films (presumably graphene-like structures), carbon nanofibers and nanotubes (straight and curved, with a diameter of 70 to 150 nm and a length of several microns). These results may be applicable to optimize the production of carbon materials by simultaneous carbonization of cotton fibers with the secondary nanostructures formed on their surface, which may be useful for new applications of carbon materials in such fields as energy storage, electronics, and biomedical engineering.