| 1. |
- Dzwilewski, Andrzej, et al.
(författare)
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Characterization of phases synthesized close to the boundary of C60 collapse at high temperature high pressure conditions
- 2007
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Ingår i: Diamond and related materials. - : Elsevier BV. - 0925-9635 .- 1879-0062. ; 16:8, s. 1550-1556
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Two sets of samples were synthesized at high pressure high temperature conditions in the P-T region where C-60 molecules collapse into a nearly amorphous graphite-like hard carbon phase. For the first set, heating temperature was varied at fixed pressure and preparation time. For the second set, synthesis time was varied at fixed pressure and fixed temperature. Detailed structural characterization of samples was performed using Raman spectroscopy and powder XRD. Mechanical properties of the samples have been studied by nanoindentation method. It has been found that duration of heat treatment under high pressure is an important parameter which influences the temperature of fullerene cage collapse. Both tetragonal and rhombohedral polymeric phases transform into hard carbon phase over a rather narrow temperature interval, but the tetragonal phase shows somewhat increased stability against C-60 collapse. Viscoelastic mechanical behavior during nanoindentation was observed for fullerene polymers but not for graphite-like hard carbon phase. Possible mechanism for nucleation of the hard carbon phase in polymeric C-60 networks is discussed.
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| 2. |
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| 3. |
- Talyzin, Alexandr, et al.
(författare)
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High pressure phase transition in LiBH4
- 2007
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 180:2, s. 510-7
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Tidskriftsartikel (refereegranskat)abstract
- The high-pressure phase transition from ambient pressure alpha-LiBH4 to high-pressure beta-LiBH4 was observed by Raman spectroscopy and X-ray diffraction between 0.8 and 1.1 GPa. The phase boundary between these two phases was mapped over a large range of temperatures using thermal conductivity studies and differential thermal analysis. The structure of the high-pressure phase could not be identified due to small number of experimentally observed reflections, but it was shown that it is different from previously reported theoretical predictions.
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| 4. |
- Talyzin, Alexandr, et al.
(författare)
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Hydrogenation of C60 at 2 GPa Pressure and High Temperature.
- 2006
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 325:2-3, s. 445-451
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogenation of C60 at 2 GPa and 723–823 K was performed with thermal decomposition of LiAlH4 as a hydrogen source. Analysisof hydrogenation products showed that the method can produce not only C60H36, but also hydrofullerides C60Hx with 44 < x < 52.Unlike other hydrogenation methods in which pristine C60 reacts with hydrogen, the high pressure/high temperature conditions resultfirst in C60 polymerization into a tetragonal phase which later reacts with hydrogen. It is suggested that hydrogen first attacks intermolecularcarbon–carbon bonds, resulting in complete depolymerization of C60 at a later stage of the hydrogenation process. This modelsuggests the possibility to select starting points for hydrogenation by choosing specific polymeric structures of C60. Hydrogenated polymericC60 was identified as an intermediate reaction product. Characterization of highly reduced material was performed by Raman andIR spectroscopy, X-ray diffraction, and atmospheric pressure photoionization Fourier transform ion cyclotron resonance massspectrometry.
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| 5. |
- Talyzin, Alexandr, et al.
(författare)
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Structural and magnetic properties of polymerized C60 with Fe
- 2007
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Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 55:1, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- We provide evidence that high-pressure high-temperature (2.5 GPa and 1040 K) treatment of mixtures of iron with fullerene powders leads to the complete transformation of iron into iron carbide Fe3C. The comparison of the magnetic properties (Curie temperature and magnetic moment) of the here studied samples and those for the ferromagnetic polymer Rh-C-60 indicates that the main ferromagnetic signal reported in those samples is due to Fe3C and not related to the ferromagnetism of carbon as originally interpreted. Taking into account the results obtained in this study the original paper on "Magnetic carbon" [Nature 413, 716 (2001)] was recently retracted.
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| 6. |
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