TAILIEUCHUNG - Carbon Nanotubes Episode 2

Tham khảo tài liệu 'carbon nanotubes episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 8 M. Endo el al. Fig. 13. HRTEM image of ail as-grown thick PCNT. 002 lattice image demonstrates the innermost hollow core core diam. nm presumably corresponding to the as-formed nanotube. The straight and continuous innermost two fringes similar to Fig. 5 are seen arrow . involved might be separated by pulverizing the VGCF material. In Fig. 14a a ca. 10 gm diameter VGCF that has been broken in liquid nitrogen is depicted revealing the cylindrical graphitic nanotube core with diameter Fig. 14. PCNTs white arrow appeared after breakage of VGCF a FE-SEM image of broken VGCF cut in liquid nitrogen and b HRTEM image showing the broken part observed in very thin VGCF. The nanotube is clearly observed and this indicates that thin VGCF grow from nanometer core by thickening. of ca. 10 nm white arrow observed by field emission scanning electron microscopy FE-SEM 25j. It is thus suggested that at least some of the VGCFs start as nanotube cores which act as a substrate for subsequent thickening by deposition of secondary pyrolytic carbon material as in the catalytically primarily grown hollow fiber. In Fig. 14b is also shown the TEM image corresponding to the extruded nanotube from a very thin fiber. It is clearly observed that the exposed nanotube is continuing into the fiber as a central hollow core as indicated by the white arrow in the figure. It is interesting that as indicated before in Fig. 14a the core is more flexible than the pyrolytic part which is more fragile. 8. CONCLUSION Pyrolytic carbon nanotubes PCNTs which grow during hydrocarbon pyrolysis appear to have structures similar to those obtained by arc discharge techniques using graphite electrodes ACNTs . The PCNTs tend to exhibit a characteristic thickening feature due to secondary pyrolytic carbon deposition. Various tip morphologies are observed but the one most frequently seen has a 20 opening angle suggesting that in general the graphene conical tips possess a cluster of five pentagons that may be .

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