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Thermal transport in partially unzipped CNTs

Thermal transport in partially unzipped CNTs. Xiaobin Chen Tsinghua University. 2010.7.8 TIENCS workshop NUS , Singapore. OUTLINE. Background Model Results Discussion Conclusion. Background. Tour, Nature (2009). Vega-Cantu, Nano Lett (2009). Narrow ribbons.

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Thermal transport in partially unzipped CNTs

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  1. Thermal transport inpartially unzipped CNTs Xiaobin Chen Tsinghua University 2010.7.8 TIENCS workshop NUS , Singapore

  2. OUTLINE • Background • Model • Results • Discussion • Conclusion

  3. Background Tour, Nature (2009) Vega-Cantu, Nano Lett (2009) • Narrow ribbons. • High yields • High quality • Controllable width, edge structures, placement and alignment. HJ Dai, Nature (2009)

  4. Potential application Brey, PRL (2009) B Huang, JACS (2009) B Wang, PRB (2010)

  5. CNTs—High thermal conductivity S. Berber, 2000 B. Li, 2005 Kim, 2001, MWCNT 6600 M. A. Osman, 2001 H. Dai, 2006 J. Che, 2000 M. Alaghemandi, 2009 Can a partially unzipped CNT preserve high thermal conductivity?

  6. Simplifications • Phonons’ contribution • Harmonic system • No edge-saturation

  7. Model and Method PUCNT Npu L R 1 2 3 4 • • • N Green’s function (harmonic system): Project the influences of contacts into center: Transmissionfunction

  8. Model and Method Landauer Formula:

  9. Results pu15-(6,6) CNT • s < sideal. • s ↓ as Npu ↑. • X(w) decreases a lot except for 0 ~ 300 cm-1.

  10. Transmission function • X(w) < XACNT_ideal (w) • Npu↑, X(w) ↓ and finally X(w) < XZGNR (w)

  11. Length puN-(6,6) CNT s0= sAGNR(T) • s changes little at low T. • s is reduced much more at high T. • At 300K, unzipped 50 cells, s  (2/3)s0. Lpu50  12.3 nm. • s changes exponentially with Lpu.

  12. Radius pu12-(N,N) CNT • Linear dependence at 300 K • Dsdecrease: independent of circumference.

  13. DISCUSSION

  14. 1. Half unzipped CNTs (n,n) CNT-2nZGNR junction (10,10) CNT/20ZGNR single junction Comparing to those of PUCNTs. • s n  C , but a little superlinear • s0-s increases as C gets larger. (10,10) CNT/25-UZGNR /(10,10) CNT double junction

  15. 2. Partially open superlattice • (6,6) CNT • 16 cells per supercell 8 cells with 4 dimmer lines removed. • Note: (6,6)CNT-8ZGNR in a supercell • s decreases by 76.5%. • Reasons: • Cutting makes the narrow parts narrower. • More interfaces.

  16. Conclusion • Thermal conductance of partially unzipped carbon nanotubes is reduced due to the unzipped part, but is nearly independent of the nanotube’s size. • What's more, the decrease shows an exponential dependence on the length of the unzipped part. • At room temperature, the decrease caused by an unzipped part is about 1 nW/K.

  17. Thanks for your attention! Acknowledgements • Many thanks to • Prof. Duan • Dr. Yong Xu

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