Boron-assisted transformation to rod-like graphitic carbons from multi-walled carbon nanotubes in boron-mixed multi-walled carbon nanotube solids

Yoshinori Sato, Hikaru Nishizaka, Kenichi Motomiya, Go Yamamoto, Akira Okubo, Hisamichi Kimura, Mikio Ishikuro, Kazuaki Wagatsuma, Toshiyuki Hashida, Kazuyuki Tohji

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4 Citations (Scopus)


We produced boron-mixed multi-walled carbon nanotube solids (B-mixed MWCNT solids) by heating and pressing the powder of purified MWCNTs mixed with 1, 5, and 10 wt % boron in the temperature range 1400-1800 °C every 200 °C under a constant pressure of 20 MPa in vacuo, and investigated the influence of boron addition on nanotube structure and the mechanical and electrical properties of the resulting B-mixed MWCNT solids. The structure of the prepared material was characterized by scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy-electron energy loss spectroscopy, Raman scattering spectroscopy, and X-ray diffraction, and their mechanical properties and conductivity were measured using a mechanical and Vickers indentation tester and an electric resistor, respectively. It is notable that part of the nanotubes in the B-mixed MWCNT solids solidified at 1800 °C had dramatically changed into rod-like graphitic carbons (RLGCs). The occupancy distribution of RLGCs increased with increasing boron contents. However, boron was not detected in the energy-loss near-edge structure spectrum of RLGCs. Furthermore, RLGCs were not observed in the boron-unmixed sample treated with the same solidified condition, indicating that adding boron causes a remarkable ability to transform the phase of MWCNT. Transformation from MWCNTs to RLGCs resulted in increased specific bending strength and modulus, Vickers hardness, and electrical conductivity of B-mixed MWCNT solids with increasing boron content and solidified temperature.

Original languageEnglish
Pages (from-to)2431-2439
Number of pages9
JournalACS Applied Materials and Interfaces
Issue number7
Publication statusPublished - 2011 Jul 27


  • boron
  • boron carbide
  • carbon nanotubes
  • mechanical properties conductivity
  • phase transition
  • rod-like graphitic carbons
  • solids

ASJC Scopus subject areas

  • Materials Science(all)


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