| 1. |
- Cui, Wen, et al.
(author)
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Reversible pressure-induced polymerization of Fe(C5H5)(2) doped C-70
- 2013
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In: Carbon. - : Pergamon-Elsevier Science. - 0008-6223 .- 1873-3891. ; 62, s. 447-454
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Journal article (peer-reviewed)abstract
- High pressure Raman, IR and X-ray diffraction (XRD) studies have been carried out on C-70(Fe(C5H5)(2))(2) (hereafter, "C-70(Fc)(2)") sheets. Theoretical calculation is further used to analyze the Electron Localization Function (ELF) and charge transfer in the crystal and thus to understand the transformation of C-70(Fc)(2) under pressure. Our results show that even at room temperature dimeric phase and one dimensional (1D) polymer phase of C-70 molecules can be formed at about 3 and 8 GPa, respectively. The polymerization is found to be reversible Upon decompression and the reversibility is related to the pressure-tuned charge transfer, as well as the overridden steric repulsion of counter ions. According to the layered structure of the intercalated ferrocene molecules formed in the crystal, we suggest that ferrocene acts as not only a spacer to restrict the polymerization of C-70 molecules within a layer, but also as charge reservoir to tune the polymerization process. This supplies a possible way for us to design the polymerization of fullerenes at suitable conditions.
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| 2. |
- Liu, Dedi, et al.
(author)
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Effects of alcohols on shape-tuning and luminescence-enhancing of C70 nanocrystals
- 2013
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In: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 36:2, s. 449-454
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Journal article (peer-reviewed)abstract
- C70 nanotubes, nanorods and nanoparticles were produced by introducing a series of alcohols as precipitant into a C70/m-xylene solution. The effects of alcohols with different carbon chain lengths on the shape control of C70 nanocrystals were investigated. Alcohols with more than two carbon atoms in the longest chain linked to the hydroxyl groups induced the formation of C70 nanotube/rods. In contrast, alcohols containing two or fewer carbon atoms resulted in C70 nanoparticles. Structural analysis indicated that alcohol molecules exist in the C70 nanocrystals, forming solvated structures. The freshly formed C70 nanotubes and nanoparticles have orthorhombic and hexagonal solvated structures, respectively. Room temperature photoluminescence was further carried out on the solvated C70 nanocrystals to investigate their optical properties. We found that the luminescence intensities of C70 nanocrystals were significantly enhanced by the introduction of alcohols.
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| 3. |
- Sundqvist, Bertil, et al.
(author)
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Ionic conductivity in three crystalline phases of LiBH4 under pressure
- 2013
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In: High Pressure Research. - : Taylor & Francis. - 0895-7959 .- 1477-2299. ; 33:1, s. 141-151
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Journal article (peer-reviewed)abstract
- The AC electrical conductivity of LiBH4 was investigated below 2GPa between 1Hz and 1.6MHz. The high-temperature phase has an ionic conductivity of up to 0.01Scm(1), while the low-temperature phases have conductivities two orders of magnitude lower. All phases show an Arrhenius behaviour with activation energies E-a between 0.5 and 0.7eV, in good agreement with earlier data except for phase III, which is found to have the highest activation energy of the phases studied. The high-temperature phase has a minimum in E-a near 1GPa, close to the triple point, correlated with a sudden change in activation volume. These features may indicate an isostructural phase transition. The conductivities of the ambient temperature phases increase temporarily by an order of magnitude after transitions between these phases, probably due to new diffusion channels via structural defects. The phase diagram agrees well with earlier results.
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| 4. |
- Yao, Mingguang, et al.
(author)
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Pressure-induced transformation and superhard phase in fullerenes : the effect of solvent intercalation
- 2013
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:7, s. 071913-
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Journal article (peer-reviewed)abstract
- We studied the behavior of solvated and desolvated C-60 crystals under pressure by in situ Raman spectroscopy. The pressure-induced bonding change and structural transformation of C60s are similar in the two samples, both undergoing deformation and amorphization. Nevertheless, the high pressure phases of solvated C-60 can indent diamond anvils while that of desolvated C(60)s cannot. Further experiments suggest that the solvents in the solvated C-60 act as both spacers and bridges by forming covalent bonds with neighbors in 3D network at high pressure, and thus, a fraction of fullerenes may preserve the periodic arrangement in spite of their amorphization.
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| 5. |
- Yu, Junchun, 1983-, et al.
(author)
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Buckminsterfullerene : A Strong, Covalently Bonded, Reinforcing Filler and Reversible Cross-Linker in the Form of Clusters in a Polymer
- 2013
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In: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 2:6, s. 511-517
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Journal article (peer-reviewed)abstract
- A Buckminsterfullerene/polyisoprene (C60/PI) composite was synthesized at high-temperature, high-pressure (HP&HT) conditions. The composite has significantly improved tensile strength and Young’s modulus, by up to 49% and 88% per wt % C60, respectively, which is much higher than for corresponding composites with carbon nanotube (CNT) fillers. The reinforcing action of C60 fillers is different from that of CNTs as C60 becomes covalently bonded to PI chains, and C60 clusters in PI form C60–C60 covalent bonds. The latter are reversible and break by heating at 1 bar, which suggests improved recyclability of the material and indicates that carbon nanostructures can be used as strong reversible cross-linkers (“vulcanizers”) in elastomers.
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