Study of the bromination of pitch-based carbon fibres

Br treated graphite nanoplatelets for improved electrical conductivity of polymer composites

“…The fraction of covalent Br showed the lowest value after the 3 h treatment, which coincides with the highest WHM value obtained from the XRD analysis. It has been reported for carbon fibers that bromination treatment generates mainly charge transfer (ionic) bonding between C and Br and only prolonged treatment durations can generate covalent bonds [5]. Covalent C-Br bonds can form more readily with C atoms at the edges of the graphitic basal plans, hence the GNP -with more edge C atoms -are more susceptible than carbon fibers to formation of covalent C-Br bonds.…”

“…Therefore, significant efforts have been directed towards improving the electrical conductivity of conducting composites. It has been reported [4,5] that intercalation of guest atoms between the graphene planes forming ionic bonds (charge transfer) can enhance the electrical conductivity of graphitic material by adding electrons to its conduction band or holes to the valence band. Meanwhile, the formation of covalent bonds between the guest atoms and graphite can depress the carrier concentration and displace some of the C atoms slightly away from the highly planar structure of pristine graphite, which in turn decreases the electrical conductivity.…”

“…The reasons that we chose bromine as the model compound has three folders: 1) bromine is less toxic and easier to intercalate; 2) brominated carbon fibres showed long term stability under ambient condition [4] and a high thermal stability below 150 o C [4,5]; 3) bromine has intermediate chemical activities in host-guest interactions, compared to Iodine which allows a weak host-guest reactivity, thus introducing only weak charge transfer, and fluorine, which is so strong that covalent bonding can be easily formed with host materials.…”

“…The charge transfer was the main bonding type between Br and C, and covalent bonding was introduced only after prolonged reactions [5]. A higher level of graphitization of the host fiber induced better intercalation and higher electrical conductivity of doped carbon fibres [4,6].…”

Micro-Raman spectroscopy of the solid state: applications to semiconductors and thin films

“…Since many microstructural information can be obtained from the Raman spectra of carbons, Raman microscopy was found to be a very valuable method in characterizing new synthesized carbons-based materials [32][33][34][35][36] such as fullerene, fullerite, nanotubes, carbon fibers, layered intercalate carbon-based structures, etc.…”