Morphology and Structure of Carbon Nanoparticles Generated from Graphite Nitrate Co-intercalation Compound. Effect of Sonication Regime

Few-layer graphenes and nanoscrolls have been prepared by exfoliation of the triple graphite nitrate co-intercalation compound (GNCC) as well as pre-thermally expanded GNCC in liquid media. Graphite nitrate sequentially co-intercalated with ethyl formate and acetic acid and thermally expanded graphite (TEG) obtained from it were used as precursors of carbon nanoparticles. Ethanol, acetonitrile and a mixture of DMFA:H2O (9:1 by volume) were used as solvents for liquid phase exfoliation of GNCC and TEG assisted with sonication. The microstructure and morphology of obtained few-layer graphenes and nanoscrolls were investigated by transmission electron microscopy (TEM). Planar sizes of the as-prepared few-layer graphenes reached several tens of μm and their thickness was within 1–10 atomic layers according to TEM data. Sonication regime effect on the resulting carbon nanoparticles morphology was studied. It was shown that sonication with a power of 70 W (42 kHz) provided obtaining of the few-layer graphene suspensions containing also single-layered graphene particles. The sonication with 315–630 W (22 kHz) leads to the formation of carbon nanoscrolls. It was found that ethanol is more preferable medium for carbon nanoparticles generation as compared to acetonitrile. Liquid phase exfoliation of GNCC and pre-thermally expanded GNCC allows obtaining dispersions of carbon nanoparticles with various morphology—single- and few-layer graphenes, nanoscrolls as well as small graphene particles.