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Träfflista för sökning "WFRF:(Zou Guangtian) "

Sökning: WFRF:(Zou Guangtian)

  • Resultat 1-10 av 12
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1.
  • Hou, Yuanyuan, et al. (författare)
  • Comparative study of pressure-induced polymerization of C60 nanorods and single crystals
  • 2007
  • Ingår i: Journal of Physics Condensed Matter. - Bristol : Institute of Physics. - 0953-8984. ; 19:42, s. 425207
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we report a comparative study of pressure-induced polymerization in C60 nanorods and bulk single crystals, treated simultaneously under various pressures and temperatures in the same experiment. For both materials, orthorhombic, tetragonal and rhombohedral phases have been produced under high pressure and high temperature. The structures have been identified and compared between the two sample types by Raman and photoluminescence spectroscopy. There are differences between the Raman and photoluminescence spectra from the two types of materials for all polymeric phases, but especially for the tetragonal phase. From the comparison between nanorods and bulk samples, we tentatively assign photoluminescence peaks for various polymeric phases.
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2.
  • Zou, Yonggang, et al. (författare)
  • Rotational dynamics of confined C60 from near-infrared Raman studies under high pressure
  • 2009
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 106:52, s. 22135-22138
  • Tidskriftsartikel (refereegranskat)abstract
    • Peapods present a model system for studying the properties of dimensionally constrained crystal structures, whose dynamical properties are very important. We have recently studied the rotational dynamics of C60 molecules confined inside single walled carbon nanotube (SWNT) by analyzing the intermediate frequency mode lattice vibrations using near-infrared Raman spectroscopy. The rotation of C60 was tuned to a known state by applying high pressure, at which condition C60 first forms dimers at low pressure and then forms a single-chain, nonrotating, polymer structure at high pressure. In the latter state the molecules form chains with a 2-fold symmetry. We propose that the C60 molecules in SWNT exhibit an unusual type of ratcheted rotation due to the interaction between C60 and SWNT in the “hexagon orientation,” and the characteristic vibrations of ratcheted rotation becomes more obvious with decreasing temperature.
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3.
  • Ma, Honglei, et al. (författare)
  • Synchrotron X-ray diffraction and infrared spectroscopy studies of C60H18 under high pressure
  • 2010
  • Ingår i: Journal of Physical Chemistry Letters. - American Chemical Society. - 1948-7185. ; 1:4, s. 714-719
  • Tidskriftsartikel (refereegranskat)abstract
    • In situ high-pressure angle-dispersive synchrotron X-ray diffraction and high-pressure mid-infrared (IR) spectrum measurements of C60H18 were carried out up to 32 and 10.2 GPa, respectively. Our diffraction data indicated that the fcc structure of C60H18 was stable up to 32 GPa. The bulk modulus B0 was determined to be 21 ± 1.16 GPa, about 40% higher than that of C60. The C−H vibrations still existed up to 10.2 GPa, and the vibrational frequencies decreased with increasing pressure. IR-active vibrational frequencies and their corresponding eigenvectors of C60H18 were simulated by DMOL3. The effects of the hydrogen atoms attached to the fullerene molecular cage on the stability of the structure under high pressure are discussed.
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4.
  • Hou, Yuanyuan, et al. (författare)
  • Photoluminescence properties of high-pressure-polymerized C60 nanorods in the orthorhombic and tetragonal phases.
  • 2006
  • Ingår i: Applied Physics Letters. - 0003-6951. ; 89:18, s. 181925
  • Tidskriftsartikel (refereegranskat)abstract
    • C60 nanorods in two polymeric phases have been synthesized under different high pressure and high temperature conditions. Orthorhombic and tetragonal phases have been identified from Raman spectra. The rod shape can be kept under quasihydrostatic pressure. The photoluminescence intensity of the polymeric C60 nanorods has been greatly enhanced compared with that of pristine C60 nanorods. The main fluorescence band shifted from 730  nm in the unpolymeric phase to 748  nm and near infrared 780  nm in the orthorhombic and tetragonal phases, respectively. The enhanced photoluminescence with tunable frequency for different polymeric C60 nanorods suggests potential applications in luminescent nanomaterials.
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5.
  • Li, Bing, et al. (författare)
  • Rhodium dihydride (RhH(2)) with high volumetric hydrogen density
  • 2011
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 108:46, s. 18618-18621
  • Tidskriftsartikel (refereegranskat)abstract
    • Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH(2)) with high volumetric hydrogen density (163.7 g/L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4 GPa and fluorite-typed fcc RhH(2) at 8 GPa. RhH(2) is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH(2) is recoverable after releasing pressure cryogenically to 1 bar and is capable of retaining hydrogen up to 150 K for minutes and 77 K for an indefinite length of time.
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6.
  • Liu, Bingbing, et al. (författare)
  • Electric resistance of single-walled carbon nanotubes under hydrostatic pressure
  • 2001
  • Ingår i: Solid State Communications. - Elsevier B.V.. - 0038-1098. ; 118:1, s. 31-36
  • Tidskriftsartikel (refereegranskat)abstract
    • The electric resistance of single-walled nanotube mats has been studied systematically under both ambient and high hydrostatic pressures up to 1.5 GPa. Both the temperature dependence of the resistance and the magnetoresistance indicate that electrical transport occurs by variable range hopping, apparently in 2D. We suggest that this unexpected dimensionality arises from a fractal network of tubes and bundles. Under hydrostatic pressure (HP) the resistance still shows 2D variable range hopping and decreases with increasing HP. An irreversible increase in localization length and DOS is induced below 0.5 GPa. The behavior is reversible and due to strong interaction of tubes from 0.5 GPa up to 1.05 GPa. These results indicate that 2D variable range hopping occurs within bundles.
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7.
  • Liu, Bingbing, et al. (författare)
  • Resistivity and fractal structure in carbon nanotube networks
  • 2002
  • Ingår i: Journal of Physics Condensed Matter vol. 14 issue 44 : Proceedings of the Joint 18th International Conference on High Pressure Science and Technology (AIRAPT 18) and the 11th High Pressure Conference of China (HPCC-11), Beijing 2001. - Bristol : Institute of Physics. ; s. 11125-11129
  • Konferensbidrag (refereegranskat)abstract
    • We have measured the temperature and magnetic field dependence of the resistance for bulk samples of single-walled nanotubes treated in different ways. Hydrostatic pressure-treated samples and as-grown samples show a two-dimensional variable-range hopping behaviour while samples treated in non-hydrostatic pressure or in acid for a long time show a three-dimensional transport behaviour. We suggest that the observed two-dimensional behaviour arises from a network structure with a fractal dimension lower than three.
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8.
  • Liu, Bingbing, et al. (författare)
  • Synthesis and characterization of single-walled nanotubes produced with Ce as catalyst
  • 2000
  • Ingår i: Molecular Materials: Molecular Crystals and Liquid Crystals Section C, vol. 13 : Proceedings of the 4th International Workshop on Fullerenes and Atomic Clusters (IWFAC'99), St. Petersburg 1999. - Overseas Publishers Association N.V.. ; s. 75-80
  • Konferensbidrag (refereegranskat)abstract
    • We have studied the effect of using rare-earth elements C (typically +4 oxide state) and Eu (typically +2 oxide state) together with nanometer Ni as catalysts to synthesize SWNT in high yield by arc evaporation. A black collar deposit containing mainly SWNT was formed in the presence of Ce/Ni while only nanometer carbon particles were formed using Eu/Ni, as identified by SEM, TEM and Raman spectra. The Raman spectra of our SWNT mats show difference from spectra shown in the literature in a low frequency range, indicating that our mats contain chiral tubes. The temperature dependent resistance of SWNT mats was also measured. A semiconducting behaviour was observed with a negative dR/dT and no resistance minimum from 2 to 350 K. The resistance follows a 2D variable range hopping behaviour.
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9.
  • Liu, Bingbing, et al. (författare)
  • Synthesis and characterization of single-walled nanotubes produced with Ce/Ni as catalysts.
  • 2000
  • Ingår i: Chemical Physics Letters. - Elsevier B.V.. - 0009-2614. ; 320:3-4, s. 365-372
  • Tidskriftsartikel (refereegranskat)abstract
    • SWNTs were synthesized in high yield in the presence of Ce/Ni as catalyst. Raman and SEM results show that a fraction of the tubes are chiral and have small diameters (the smallest one is 0.79 nm), indicating that Ce plays an important role in the formation. Acid treatment is effective in eliminating impurities but changes the morphology and the electric resistance of mats with increasing treatment time. The resistance of as-grown and short time acid-treated mats follow a 2D VRH behaviour while mats treated for a long time follow a 3D model. The results indicate that hopping conduction occurs on bundles or on tubes and that there are intrinsic links between tubes in as-grown mats.
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10.
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