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Lecture 4 Non-carbon nanotubes

Lecture 4 Non-carbon nanotubes. N. 1. BN nanotubes. B. C. Several features associated with BN-nanotubes. 1. Interlayer-spacing = ?. 0.33 nm. cannot. 2. Can BN form pentagons or heptagons ( 五七連環 )?. B. N. N-N bond. B-B bond. hexagon. pentagon. pentagon. o.k. not o.k. not o.k.

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Lecture 4 Non-carbon nanotubes

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  1. Lecture 4 Non-carbon nanotubes

  2. N 1. BN nanotubes B C

  3. Several features associated with BN-nanotubes 1. Interlayer-spacing = ? 0.33 nm

  4. cannot 2. Can BN form pentagons or heptagons (五七連環)? B N N-N bond B-B bond hexagon pentagon pentagon o.k not o.k not o.k same as heptagon + + 同電荷不會鍵結在一起

  5. If BN cannot form pentagons how do they close BN-nanotubes, in other words, how BN nanotubes stop to grow? 4-member ring

  6. BN-nanotubes made by arc discharge

  7. How to make BN nanotubes? 1. Arc discharge. 2. Substitution of carbon nanotubes by BN using annealing process.

  8. - + arc discharge using graphite rods - + arc discharge using Ta-tube filled with BN powder as anode and Cu rod as cathode Modified arc discharge BN is insulator, cannot electrically conduct, so Ta-tube is used for conduction purpose

  9. Carbon nanotubes, CNTs BN nanotubes CNTs + B2O5 heated in N2 (or NH3) flow at 1700 C for 40 mins Substitution method

  10. 3B2O5 + 9H2O + 6CO 6NH3 B N

  11. Because C atoms are substituted by BN (not growth process) , so BN nanotube tips are opened, i.e. substitution is difficult to proceed at tube tips.

  12. Inorganic nanotubes MS2: M= Nb, W, Mo Concertina-like structure, no M-M and S-S bonds only M-S bonds

  13. M atoms situate at the central line

  14. 6.2 Å inter-layer spacing WS2-nanotube

  15. W-wire How to make MS2-nanotubes Template growth of MS2-nanotubes Heating in Air at 600-800 C WO3 rod Heating in H2S/H2 at900 C WS2-nanotubes

  16. 反應式 3WO3 + 6H2S + 3H2  3WS2+ 9H2O 3MoO3 + 6H2S + 3H2 3MoS2 + 9H2O

  17. Mixed phase of nanotubes

  18. WxMoyCzS2-nanotubes, x + y + z = 1

  19. WS2-nanotubes Carbon nanotubes

  20. 在TEM下, WS2比carbon nanotubes 具更深之對比 Carbon nanotubes WS2-nanotube

  21. 0.62 nm 0.34 nm

  22. S Nb 0.58 nm NbS2-structure

  23. C-tubes@WS2-nanotubes

  24. NbS2-nanorodes

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