| 1. |
- Aksenova, N.A., et al.
(författare)
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Structural studies of C60 polymerized at high pressure
- 1997
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Ingår i: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials. - Pennington, NJ : Electrochemical Society, Incorporated. - 1566771927
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Konferensbidrag (refereegranskat)
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| 2. |
- Aksenova, N.A., et al.
(författare)
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Structure studies of C60 polymerized at low pressures
- 1997
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Ingår i: Fullerenes. - Pennington, NJ : The Electrochemical Society. - 1566771927 ; , s. 687-694
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Konferensbidrag (refereegranskat)abstract
- The structure and lattice properties of a polymerized C60 sample were investigated by X-ray powder diffraction over the range from liquid-nitrogen to room temperature. The aim of these studies was to establish the effect of low-pressure compression (up to 1.1 GPa) on the phase composition of the sample, to determine the structure of the phases involved, to obtain the variation of the lattice parameters with temperature, to observe eventual phase transformation in polymerized C60, and to elucidate the evolution of the orientational order with varying temperature. Analysis of the room-temperature diffraction patterns indicates that the sample contained at least two major phases, namely rhombohedral and and tetragonal with the polymerization array close to two-dimensional. Our data obtained on samples annealed at 300 C in the air allow us to conclude that polymerized C60 converts to a mixture of the fcc structure plus a new phase, presumably C60O.
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| 3. |
- Sundqvist, Bertil, et al.
(författare)
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Polymerization of C60 under hydrostatic and non-hydrostatic conditions
- 1997
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Ingår i: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 5. - Pennington, NJ : The Electrochemical Society. - 1566771927 ; , s. 439-449
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Konferensbidrag (refereegranskat)abstract
- We have submitted both powder and single crystal C60 to pressures in the range 1 - 2 GPa at temperatures between 300 and 900 K in order to study pressure polymerization. Reaction conditions varied, from non-hydrostatic conditions with powder samples in steel capsules treated in solid pressure media, to hydrostatic experiments using silicone oils, N2 or He gas. The reacted samples were characterized by Raman spectroscopy and x-ray diffraction. Depending on experimental conditions, their structures varied from orthorhombic (single crystals) to more or less disordered face centered cubic lattices, and the observed Raman spectra could usually be correlated with the observed structures. The results are used to refine and update the pressure-temperature phase diagram of C60.
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| 4. |
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| 5. |
- Wågberg, Thomas, et al.
(författare)
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Polymeric phases of C60
- 1997
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Ingår i: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 5. - Pennington, NJ : The Electrochemical Society. - 1566771927 ; , s. 674-679
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Konferensbidrag (refereegranskat)abstract
- We have investigated the "low" pressure region where C60 can be transformed into polymeric chains or clusters. To learn more about the polymerization process we have treated pristine C60 at several different temperatures under hydrostatic pressures in silicone oil. We found that the reaction rate varied with temperature. Above 520 K at 1.0 GPa similar and high polymer fractions were obtained in all samples, but at 497 K the polymer fraction was only 10% after three hours, as indicated by the shift of the intensity of the pentagonal pinch mode in the Raman spectrum. Also, samples treated at the same pressure and temperature but with different thermal pre-history showed different degrees of polymerization. We have also found a correlation between the shift of the pentagonal pinch mode in the Raman spectrum to 1463 /cm and the intermolecular vibrational mode at 97 /cm. We therefore make the conclusion that the shift of the pentagonal pinch mode to 1463 /cm corresponds to the presence of dimers in the sample.
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