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2,079 results on '"Bando, Y."'

322. Disordered state in first-order phase transitions: Hexagonal-to-cubic and cubic-to-hexagonal transitions in boron nitride

Author

Eremets, M., Takemura, K., Yusa, H., Golberg, D., Bando, Y., Blank, V., Sato, Yohei, Watanabe, K., Eremets, M., Takemura, K., Yusa, H., Golberg, D., Bando, Y., Blank, V., Sato, Yohei, and Watanabe, K.

Abstract

The microscopic mechanism of diffusion-type solid-solid first-order transitions was studied in boron nitride. This substance exhibits an extreme case of transitions between very different lattices, hexagonal (graphite-like) and cubic (diamond-like) phases, accompanied by a large change in the volume. A boundary between the hexagonal and cubic phases was produced by local heating of either a cBN or hBN sample in a diamond-anvil cell under hydrostatic pressure with the aid of a laser so that the sample was partially transformed to another phase. The boundary was studied with the aid of micro-Raman and high-resolution electron microscopy. In the transient region between the two phases a mixture of highly fragmented disordered nanocrystallites and the amorphous state of BN was found. BN nanotubes growing from the amorphous state were also discovered in this region.

Published
1998

323. Boron-doped carbon fullerenes and nanotubules formed through electron irradiation-induced solid-state phase transformation

Author

Golberg, D., Bando, Y., Kurashima, K., Sasaki, T., Golberg, D., Bando, Y., Kurashima, K., and Sasaki, T.

Abstract

Here we report on the in situ creation of single/multi-shelled fullerenes and multi-walled nanotubules by electron irradiation of chemical vapor deposit graphitic BxC1-x (x≤0.2) in a high-resolution 300 kV electron microscope. Nanostructure formation occurred through irradiation-induced solid-state phase transformation, in contrast to conventional fullerene/nanotube synthesis from the gas phase. The fullerene/nanotubule chemical composition and bonding character were analyzed by electron energy loss spectroscopy applying a 0.5 nm electron probe. The B/C ratio of the observed curled, closed nanostructures has never exceeded ∼0.1. Unlike pure carbon "onions," most of the B-doped fullerenes exhibited a polyhedral faceted circumference suggestive of B-induced buckling.

Published
1998

324. Synthesis of BN nanotubes in a laser heated DAC

Author

Yusa, H., Eremets, M. I., Golberg, D., Takemura, K., Kurashima, K., Bando, Y., Yusa, H., Eremets, M. I., Golberg, D., Takemura, K., Kurashima, K., and Bando, Y.

Abstract

BN nanotubes were found in laser heated cBN and hBN at nitrogen pressures up to 10.1 GPa in a diamond anvil cell. The BN nanotubes were recrystallized from the BN-melts in a super critical nitrogen fluid. Their shape, bonding nature and stoichiometry were examined by high resolution electron microscopy and electron energy loss spectroscopy. The BN nanotubes did not contain any additional inclusion. The nanotubes typically exhibit 3–8 shells and stoichiometry of B/N∼1.

Published
1998

325. Octahedral boron nitride fullerenes formed by electron beam irradiation

Author

Golberg, D., Bando, Y., Stéphan, O., Kurashima, K., Golberg, D., Bando, Y., Stéphan, O., and Kurashima, K.

Abstract

Here we report on the formation of fullerenes with a reduced number of layers (typically ≤3) in boron nitride (BN) which was subjected to in situ electron irradiation at 20 and 490°C in a high resolution 300 kV transmission electron microscope (HRTEM). The BN fullerenes exhibited B/N stoichiometry of ∼1 as confirmed by electron energy loss spectroscopy using a 1 nm electron probe. The fullerene HRTEM images revealed rectangle-like shapes when viewed in specific projections, unlike the quasispherical carbon fullerene morphology. The octahedral BN fullerene model [O. Stéphan, Y. Bando, A. Loiseau, F. Willaime, N. Shramchenko, T. Tamiya, and T. Sato, Appl. Phys. A 67, 107 (1998)] is verified by the BN fullerene observations at different viewing angles.

Published
1998

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