| 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. |
- Isakina, A.P., et al.
(författare)
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Structure and microhardness of low pressure polymerized fullerite C60
- 1998
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 24:12, s. 896-903
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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
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| 3. |
- Aleksandrovski, A. N., et al.
(författare)
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Anomalies of the plastic deformation of solid parahydrogen
- 1987
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Ingår i: Soviet Journal of Low Temperature Physics. - 0360-0335. ; 13:10, s. 623-624
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Tidskriftsartikel (refereegranskat)abstract
- The work hardening curves σ(ε) of special-purity parahydrogen single crystals are obtained in the temperature range 2-6 °K at very low stresses (σ=5 10 - 2 g/mm2). Our study reveals a number of anomalies, in particular an effect whereby a sample recovers its dimensions after plastic deformation reaching 7%. The work hardening curves of solid neon are also obtained for comparison. The gravity-induced downward flow of parahydrogen single crystals at helium temperatures mentioned in the literature has not been observed.
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| 4. |
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| 5. |
- Lukina, I N, et al.
(författare)
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Effect of synthesis parameters on the structure and properties of carbon particles formed from amorphous fullerites
- 2020
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Konferensbidrag (refereegranskat)abstract
- The effect of high-pressure synthesis temperature on the structure and indentation characteristics of the superelastic hard carbon formed from amorphous fullerites and on the tribological properties of the Co-based composite materials (CM) reinforced by the particles of such carbon has been studied by Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), indentation measurements, and tribological tests. It is shown that ball milling (for 48 h) of C60 fullerite crystals results in the amorphization of the product of fullerite transformation upon their high-pressure treatment at temperatures above the stability limit of fullerene molecule (~800°C). An increase in synthesis temperature at 8 GPa from 800°C to 1200°C leads to a gradual graphitization of the structure of amorphous fullerite derived carbon. This decreases its hardness and indentation modulus from 32 to 18 GPa and from 256 to 95 GPa, respectively, and increases the elastic recovery (from 80% to 86%). The best tribological characteristics of the CM are attained at the maximum particle hardness, which is realized in the CM synthesized at 800°C. When the synthesis temperature is elevated to 1200°C, the friction coefficient and wear rate of the CM increase, but they remain substantially lower than those of the matrix cobalt.
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| 6. |
- Pasupathy, A. N., et al.
(författare)
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Vibration-assisted electron tunneling in C140 transistors
- 2005
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 5:2, s. 203-207
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Tidskriftsartikel (refereegranskat)abstract
- We measure electron tunneling in transistors made from C140, a molecule with a mass-spring-mass geometry chosen as a model system to study electron-vibration coupling. We observe vibration-assisted tunneling at an energy corresponding to the stretching mode of C140. Molecular modeling provides explanations for why this mode couples more strongly to electron tunneling than to the other internal modes of the molecule. We make comparisons between the observed tunneling rates and those expected from the Franck-Condon model.
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| 7. |
- Persson, P-A, et al.
(författare)
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Physical properties of pressure polymerized C60
- 1995
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Ingår i: High Pressure Science and Technology. - Singapore : World Scientific and Engineering Academy and Society. - 9810225474 ; , s. 716-718
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Konferensbidrag (refereegranskat)
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| 8. |
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| 9. |
- Soldatov, Alexander, et al.
(författare)
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Thermal expansion of solid H2 , HD, D2 at helium temperatures
- 1993
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Ingår i: Proceedings of the 13th General Conference of the Condensed Matter Division of the European Physical Society. - : Physica scripta. - 9187308096 ; , s. 1053-
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Konferensbidrag (refereegranskat)
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| 10. |
- Soldatov, Alexander, et al.
(författare)
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Thermal expansion of solid hydrogens
- 1992
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Ingår i: Soviet Journal of Low Temperature Physics. - 0360-0335. ; 18:2, s. 116-122
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Tidskriftsartikel (refereegranskat)abstract
- The linear thermal expansion coefficient α of solid deuterium with paramodification content of 2.25% was determined in the temperature interval 1.5-5.6 K. The contributions of the translational vibrations of the lattice αlat and the rotational motion of the molecules αrot to α are separated. The temperature dependence of αlat was determined by the expression αlat =1.475 · 10 - 7 T3+(4.5-7) · 10 - 10 T5. The possibilities of a universal description of the thermal expansion of cryocrystals with a central interaction, including quantum crystals of hydrogen isotopes, are discussed. A theoretical description is proposed and the temperature dependence of αrot is analyzed.
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