| 1. |
- Aksenova, N.A., et al.
(författare)
-
Structural studies of C60 polymerized at high pressure
- 1997
-
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
-
Konferensbidrag (refereegranskat)
|
|
| 2. |
- Aksenova, N.A., et al.
(författare)
-
Structure studies of C60 polymerized at low pressures
- 1997
-
Ingår i: Fullerenes. - Pennington, NJ : The Electrochemical Society. - 1566771927 ; , s. 687-694
-
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.
|
|
| 3. |
- Isakina, A.P., et al.
(författare)
-
Structure and microhardness of low pressure polymerized fullerite C60
- 1998
-
Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 24:12, s. 896-903
-
Tidskriftsartikel (refereegranskat)abstract
- We have carried out low-temperature x-ray diffraction studies on C60 fullerite polymerized by low quasi-hydrostatic pressure of 1.1 GPa at T = 563 K. It is established that at room temperature in freshly prepared samples three phases mainly coexist, viz. a compressed cubic phase with the lattice parameter a = 13.94 Å, an orthorhombic O' phase with the lattice parameters a = 9.12 Å, b = 9.82 Å, c = 14.60 Å, and a rhombohedral phase of symmetry R3m with the parameters a = 9.20 Å and c = 24.27 Å. Mechanical grinding or annealing at 573 K entails depolymerization of sintered samples and restoration of the fcc structure of pristine C60. During annealing in air, intercalation of fullerite lattice by oxygen molecules occurs as well as a substantial amount of some new phase is formed, most probably with tetragonal symmetry, the chemical composition and structure of which have not been determined. The microhardness of polymerized C60 is higher than that of single crystal samples roughly four-fold at room temperature and by a factor of 2.6 at liquid nitrogen temperature. Analysis shows that polymerization and grain boundaries give contributions to the microhardness of sintered samples but we did not succeed in separating these two contributions. The temperature dependence of the microhardness of polymerized samples exhibits a jump in the vicinity of 260 K, where pristine C60 fullerite undergoes the fcc-sc phase transition. We think that this jump is due to a partial destruction of the polymerized state under indentor as a result of shear straining in inhomogeneous stress fields. Annealing of polymerized C60 at a temperature of 573 K, which restores the fcc phase, leads to a considerable decrease in microhardness, the hardness "jump" near the fcc-sc transition extends in temperature and shifts to lower temperatures
|
|
| 4. |
|
|
| 5. |
- Persson, P-A, et al.
(författare)
-
Physical properties of pressure polymerized C60
- 1995
-
Ingår i: High Pressure Science and Technology. - Singapore : World Scientific and Engineering Academy and Society. - 9810225474 ; , s. 716-718
-
Konferensbidrag (refereegranskat)
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Sundqvist, B., et al.
(författare)
-
Orientational disorder and the p-T phase diagrams of fullerenes
- 1995
-
Ingår i: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials. - Pennington, NJ : Electrochemical Society, Incorporated. - 1566771048 ; , s. 891-905
-
Konferensbidrag (refereegranskat)
|
|
| 9. |
- Sundqvist, Bertil, et al.
(författare)
-
Physical properties of pressure polymerized C60
- 1996
-
Ingår i: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials. - Pennington, NJ : Electrochemical Society, Incorporated. - 1566771625 ; , s. 1014-1028
-
Konferensbidrag (refereegranskat)
|
|
| 10. |
|
|
| 11. |
- Aleksandrovskii, A. N., et al.
(författare)
-
Negative thermal expansion of fullerite C60 at helium temperatures
- 1997
-
Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 23:11, s. 943-946
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of fullerite C60 has been measured in the temperature range 2–9 K. A compacted fullerite sample with a diameter of about 6 mm and height of 2.4 mm was used. It was found that at temperatures below ~ 3.4 K the linear thermal expansion coefficient becomes negative. At temperatures above 5 K our results are in good agreement with the available literature data. A qualitative explanation of the results is proposed
|
|
| 12. |
|
|
| 13. |
- Arvanitidis, J., et al.
(författare)
-
Comparative Raman Study of the 1D and 2D Polymeric Phases of C60 under Pressure
- 1999
-
Ingår i: Physica status solidi. B, Basic research. - : John Wiley & Sons. - 0370-1972 .- 1521-3951. ; 215:1, s. 443-448
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of symmetry lowering on the phonon spectra as well as the pressure effects on the vibrational spectrum of polymerized C60 were studied by Raman spectroscopy. Drastic changes related to the splitting of degenerate modes of the C60 molecule were observed together with selected softening of some of them. In spite of many similarities in the Raman spectra of the one (1D) and two-dimensional (2D) polymeric forms of C60, some salient differences in the peak intensities and the appearance of complementary modes are evident. In the Raman spectrum of the 2D polymer under high pressure, new modes, which may be related to the deformations of molecular cages, appear. The observed pressure effects are reversible and the material remains stable for pressures up to 8.8 GPa.
|
|
| 14. |
- Lundin, Anders, et al.
(författare)
-
Compressibility of C61D2 up to 1 GPa in the temperature range 175 - 345 K
- 1996
-
Ingår i: Carbon. - : Elsevier Science Ltd.. - 0008-6223 .- 1873-3891. ; 34:9, s. 1119-1121
-
Tidskriftsartikel (refereegranskat)abstract
- We have measured the bulk modulus K for C61D2 up to 1 GPa in the temperature range 175–343 K. For face-centered cubic C61D2 above 290 K, we find an anomalously low value for K below about 0.15 GPa, possibly indicating pressure-induced changes in the structure. The (extrapolated) zero-p bulk modulus K(0) decreases with increasing T from 6.7 GPa at 175 K to 5.2 GPa at 343 K. A comparison with hypothetical expanded f.c.c. C60 with the same lattice constant shows that K(0) values are similar, indicating that the main intermolecular interactions are still between molecular bellies, not the sidegroups.
|
|
| 15. |
- Lundin, A., et al.
(författare)
-
Compression properties and p-T phase diagrams of C60, C70, and C61D2
- 1996
-
Ingår i: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials. - Pennington, NJ : Electrochemical Society, Incorporated. - 1566771625 ; , s. 1138-1142
-
Konferensbidrag (refereegranskat)
|
|
| 16. |
- Lundin, A., et al.
(författare)
-
Thermophysical properties of C70 up to 1.2 GPa
- 1995
-
Ingår i: Science and technology of fullerene materials. - Pittsburgh, Pa : Materials Research Society. - 155899260X ; , s. 555-560
-
Konferensbidrag (refereegranskat)
|
|
| 17. |
- Soldatov, Alexander, et al.
(författare)
-
Fullerenes and fullerene nanostructures
- 1996
-
Ingår i: Fullerenes and fullerene nanostructures. - Singapore : World Scientific and Engineering Academy and Society. - 9810228538 ; , s. 344-348
-
Konferensbidrag (refereegranskat)
|
|
| 18. |
- Sundqvist, B., et al.
(författare)
-
Measurements of thermophysical properties as tools to study the phase diagrams of fullerenes under pressure
- 1997
-
Ingår i: High Temperatures-High Pressures. - 0018-1544 .- 1472-3441. ; 29:1, s. 119-124
-
Tidskriftsartikel (refereegranskat)abstract
- The 14th ECTP is part of a conference series initiated in 1968 in Baden-Baden, Germany, as a European effort to collect expertise and to present the latest research in the area of measurement and theoretical predictions of thermophysical properties of materials -solids and fluids- which are of technical and industrial interest
|
|
