Synthesis and thermionic emission properties of graphitic carbon nanofibres supported on Si wafers or carbon felt
نویسندگان
چکیده
Preparation procedures and thermionic emission properties of graphitic carbon nanofibres (GCNFs) supported on Si wafer or commercial carbon felt supports are reported. GCNF/native-oxide Si wafer, GCNF/oxidized Si wafer, GCNF/Ni-coated Si wafer and GCNF/carbon felt nanocomposites are obtained by growing GCNFs from growth catalyst nanoparticles supported on these supports. Narrow herringbone GCNF/SiO2/carbon felt mats are prepared from growth catalyst nanoparticles supported on fumed silica flakes. Due to weak GCNF-to-support binding in GCNF/Si wafer mats, GCNF/carbon felt mats and GCNF/SiO2/carbon felt mats, mechanical loss of the GCNF component is facile. However, carbothermal reduction of GCNF/SiO2/carbon felt nanocomposites affords mechanically robust GCNF/SiC/carbon felt mats. Thermionic electron energy distribution profiles recorded for these new nanofibre compositions indicate classic free-electron emission with estimated work functions (4.25–4.91 eV) slightly lower than those observed for un-doped graphite or carbon nanotubes. Electron energy distributions along the low energy leading region of the profiles display a cascade of emission peaks equally spaced by ca 0.014 eV, tentatively attributed to electron emission from localized GCNF edge sites.
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