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Sökning: WFRF:(Liu Bingbing)

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1.
  • Cheng, Benyuan, et al. (författare)
  • Pressure-induced metallization and amorphization in VO2(A) nanorods
  • 2016
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 93:18
  • Tidskriftsartikel (refereegranskat)abstract
    • A metallic state enabled by the metal-insulator transition (MIT) in single crystal VO2(A) nanorods is demonstrated, which provides important physical foundation in experimental understanding of MIT in VO2. The observed tetragonal metallic state at ∼28 GPa should be interpreted as a distinct metastable state, while increasing pressure to ∼32 GPa, it transforms into a metallic amorphous state completely. The metallization is due to V 3d orbital electrons delocalization, and the amorphization is attributed to the unique variation of V-O-V bond angle. A metallic amorphous VO2 state is found under pressure, which is beneficial to explore the phase diagram of VO2. Furthermore, this work proves the occurrence of both the metallization and amorphization in octahedrally coordinated materials.
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2.
  • Cui, Jinxing, et al. (författare)
  • Structural Deformation of Sm@C88under High Pressure
  • 2015
  • Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 5
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the structural transformation of Sm@C88 under pressure up to 18 GPa by infraredspectroscopy combined with theoretical simulations. The infrared-active vibrational modes of Sm@C88 at ambient conditions have been assigned for the first time. Pressure-induced blue and red shiftsof the corresponding vibrational modes indicate an anisotropic deformation of the carbon cage uponcompression. We propose that the carbon cage changes from ellipsoidal to approximately sphericalaround 7 GPa. A smaller deformation of the carbon bonds in the area close to the Sm atom in thecage suggests that the trapped Sm atom plays a role in minimizing the compression of the adjacentbonds. Pressure induced a significant reduction of the band gap of the crystal. The HOMO-LUMOgap of the Sm@C88 molecule decreases remarkably at 7 GPa as the carbon cage is deformed. Also,compression enhances intermolecular interactions and causes a widening of the energy bands. Botheffects decrease the band gap of the sample. The carbon cage deforms significantly above 7 GPa,from spherical to a peanut-like shape and collapses at 18 GPa.
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3.
  • Cui, Wen, et al. (författare)
  • Synthesis of alkali-metal-doped C60 nanotubes
  • 2011
  • Ingår i: Diamond and Related Materials. - : Elsevier BV. ; , s. 93-96
  • Konferensbidrag (refereegranskat)abstract
    • C60 nanotubes have been synthesized by a solution–solution method. After degassing in a dynamic vacuum, the C60 nanotubes were doped with alkali metals by means of vapor evaporation method. Different temperatures have been studied to evaporate the alkali metals for the doping experiments. Raman spectrum was further employed to analyze the doping concentration of the obtained samples. It was found that all three alkali metals (Li, Na and K) used can be efficiently doped into the C60 nanotubes, forming AxC60 nanotubes. The doping concentration of Li, Na changed from low to high level, depending on the experiment temperatures, while K doping always gave saturated doping. The melt points, the ionic sizes and vapor pressures of alkali metals were thought to affect the final doping results.
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4.
  • Liu, Dedi, et al. (författare)
  • Pressure-induced phase transitions of C70 nanotubes
  • 2011
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:18, s. 8918-8922
  • Tidskriftsartikel (refereegranskat)abstract
    • Single crystalline C70 nanotubes having a face-centered-cubic (fcc) structure with diameters on a nanometer scale were synthesized by a facile solution method. In situ high pressure Raman spectroscopy and X-ray diffraction have been employed to study the structural stability and phase transitions of the pristine sample. We show that the molecular orientation-related phase transition from the fcc structure to a rhombohedral structure occurs at about 1.5 GPa, which is 1 GPa higher than in bulk C70. Also, the C70 molecules themselves are more stable in the nanotubes than in bulk crystals, manifested by a partial amorphization at 20 GPa. The crystal structure of C70 nanotubes could partially return to the initial structure after a pressure cycle above 30.8 GPa, and the C70 molecules were intact up to 43 GPa. The bulk modulus of C70 nanotubes is measured to be 50 GPa, which is twice larger than that of bulk C70.
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5.
  • Wang, Lin, et al. (författare)
  • Synthesis and high pressure induced amorphization of C60 nanosheets
  • 2007
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:10, s. 103112-
  • Tidskriftsartikel (refereegranskat)abstract
    • C-60 nanosheets with thicknesses in the nanometer range were synthesized by a simple method. Compared to bulk C-60, the lattice of the nanosheets is expanded by about 0.4%. In situ Raman spectroscopy and energy-dispersive x-ray diffraction under high pressures have been employed to study the structure of the nanosheets. The studies indicate that the bulk modulus of the C-60 nanosheets is significantly larger than that of bulk C-60. The C-60 cages in nanosheets can persist at pressures over 30 GPa, 3 GPa higher than for bulk C-60. These results suggest that C-60 crystals in even small size will be a potential candidate of superhard materials.
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6.
  • Zhang, Lixiu, et al. (författare)
  • Advances in the Application of Perovskite Materials
  • 2023
  • Ingår i: NANO-MICRO LETTERS. - : SHANGHAI JIAO TONG UNIV PRESS. - 2311-6706. ; 15:1
  • Forskningsöversikt (refereegranskat)abstract
    • Nowadays, the soar of photovoltaic performance of perovskite solar cells has set off a fever in the study of metal halide perovskite materials. The excellent optoelectronic properties and defect tolerance feature allow metal halide perovskite to be employed in a wide variety of applications. This article provides a holistic review over the current progress and future prospects of metal halide perovskite materials in representative promising applications, including traditional optoelectronic devices (solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices (artificial synapses and memristors) and pressure-induced emission. This review highlights the fundamentals, the current progress and the remaining challenges for each application, aiming to provide a comprehensive overview of the development status and a navigation of future research for metal halide perovskite materials and devices.
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7.
  • Zhang, Ying, et al. (författare)
  • Capture of novel sp3 hybridized Z-BN by compressing boron nitride nanotubes with small diameter
  • 2022
  • Ingår i: Diamond and related materials. - : Elsevier. - 0925-9635 .- 1879-0062. ; 130
  • Tidskriftsartikel (refereegranskat)abstract
    • Experimental synthesis of new sp3 hybridized carbon/boron nitride structures remains challenging despite that numerous sp3 structures have been proposed in theory. Here, we showed that compressed multi-walled boron nitride nanotubes (MWBNNTs) and boron nitride peapods (C60@BNNTs) with small diameters could transform into a new sp3 hybridized boron nitride allotrope (Z-BN). This strategy is considered from the topological transition point of view in boron nitride nanotubes upon compression. Due to the increased curvature in compressed small-diameter MWBNNTs, the uncommon 4- and 8-membered rings in Z-BN could be more favorably formed. And the irreversible tube collapse is proved to be a critical factor for the capture of the formed Z-BN, because of the competition between the resilience of tube before collapse and the stress limitation for the lattice stabilization of Z-BN upon decompression. In this case, Z-BN starts to form above 19.0 GPa, which is fully reversible below 45 GPa and finally becomes quenchable at 93.5 GPa. This collapse-induced capture of the high-pressure phase could also be extended to other tubular materials for quenching novel sp3 structures.
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8.
  • Cui, Wen, et al. (författare)
  • Reversible pressure-induced polymerization of Fe(C5H5)(2) doped C-70
  • 2013
  • Ingår i: Carbon. - : Pergamon-Elsevier Science. - 0008-6223 .- 1873-3891. ; 62, s. 447-454
  • Tidskriftsartikel (refereegranskat)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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9.
  • Du, Mingrun, et al. (författare)
  • High pressure infrared spectroscopy study on C60*CS2 solvates
  • 2017
  • Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 669, s. 49-53
  • Tidskriftsartikel (refereegranskat)abstract
    • High pressure IR study has been carried out on C-60*CS2 solvates up to 34.8 GPa. It is found that the intercalated CS2 molecules significantly affect the transformations of C-60 molecules under pressure. As a probe, the intercalated CS2 molecules can well detect the orientational ordering transition and deformation of C-60 molecules under pressure. The chemical stability of CS2 molecules under pressure is also dramatically enhanced due to the spacial shielding effet from C-60 molecules around in the solvated crystal. These results provide new insight into the effect of interactions between intercalants and fullerenes on the transformations in fullerene solvates under pressure.
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10.
  • Du, Mingrun, et al. (författare)
  • New ordered structure of amorphous carbon clusters induced by fullerene-cubane reactions
  • 2018
  • Ingår i: Advanced Materials. - : Wiley-VCH Verlagsgesellschaft. - 0935-9648 .- 1521-4095. ; 30
  • Tidskriftsartikel (refereegranskat)abstract
    • As a new category of solids, crystalline materials constructed with amorphous building blocks expand the structure categorization of solids, for which designing such new structures and understanding the corresponding formation mechanisms are fundamentally important. Unlike previous reports, new amorphous carbon clusters constructed ordered carbon phases are found here by compressing C8H8/C60 cocrystals, in which the highly energetic cubane (C8H8) exhibits unusual roles as to the structure formation and transformations under pressure. The significant role of C8H8 is to stabilize the boundary interactions of the highly compressed or collapsed C60 clusters which preserves their long‐range ordered arrangement up to 45 GPa. With increasing time at high pressure, the gradual random bonding between C8H8 and carbon clusters, due to “energy release” of highly compressed cubane, leads to the loss of the ability of C8H8 to stabilize the carbon cluster arrangement. Thus a transition from short‐range disorder to long‐range disorder (amorphization) occurs in the formed material. The spontaneous bonding reconstruction most likely results in a 3D network in the material, which can create ring cracks on diamond anvils.
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11.
  • Jiang, Linhai, et al. (författare)
  • Controlled Synthesis of CeO2/Graphene Nanocomposites with Highly Enhanced Optical and Catalytic Properties
  • 2012
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:21, s. 11741-11745
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, CeO2 nanocubes with the (200)-terminated surface/graphene sheet composites have been prepared successfully by a simple hydrothermal method. It is found that the CeO2 nanocubes with high crystallinity and specific exposed surface are well dispersed on well-exfoliated graphene surface. The (200)-terminated surface/graphene sheet composites modified electrode showed much higher sensitivity and excellent selectivity in its catalytic performance compared to a CeO2 nanoparticle-modified electrode. The photoluminescence intensity of the CeO2 anchored on graphene is about 30 times higher than that of pristine CeO2 crystals in air. The higher oxygen vacancy concentration in CeO2 is supposed to be an important cause for the higher photoluminescence and better electrochemical catalytic performance observed in the (200)-terminated surface/graphene sheet composites. Such ingenious design of supported well-dispersed catalysts in nanostructured ceria catalysts, synthesized in one step with an exposed high-activity surface, is important for technical applications and theoretical investigations.
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12.
  • Liu, Dedi, et al. (författare)
  • Effects of alcohols on shape-tuning and luminescence-enhancing of C70 nanocrystals
  • 2013
  • Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 36:2, s. 449-454
  • Tidskriftsartikel (refereegranskat)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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13.
  • Liu, Dedi, et al. (författare)
  • In situ Raman and photoluminescence study on pressure-induced phase transition in C60 nanotubes
  • 2012
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 43:6, s. 737-740
  • Tidskriftsartikel (refereegranskat)abstract
    • Single crystalline C60 nanotubes having face-centered-cubic structure with diameters in the nanometer range were synthesized by a solution method. In situ Raman and photoluminescence spectroscopy under high pressure were employed to study the structural stabilities and transitions of the pristine C60 nanotubes. A phase transition, probably because of the orientational ordering of C60 molecules, from face-centered-cubic structure to simple cubic structure occurred at the pressure between 1.46 and 2.26 GPa. At above 20.41 GPa, the Raman spectrum became very diffuse and lost its fine structure in all wavenumber regions, and only two broad and asymmetry peaks initially centered at 1469 and 1570cm-1 were observed, indicating an occurrence of amorphization. This amorphous phase remained to be reversible until 31.1 GPa, and it became irreversible to the ambient pressure after the pressure cycle of 34.3 GPa was applied.
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14.
  • Liu, Dedi, et al. (författare)
  • Photoluminescence changes of C70 nano/submicro-crystals induced by high pressure and high temperature
  • 2016
  • Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Hollow C70 nano/submicrocrystals with a fcc lattice structure were treated under various high pressure and high temperature conditions. The energy band structure was visibly changed by the high pressure and high temperature treatment, and the luminescence of the polymerized C70 nano/submicrocrystals was tuned from the visible to the near infrared range. In-situ high pressure experiments at room temperature indicate that pressure plays a key role in the tuning of band gap and PL properties in C70 nanotubes, and temperature plays an important role in the formation of stable intermolecular bonds and thus to define the final red-shift of the PL peaks. The polymeric phases of C70 nanocrystals treated at high pressure and high temperature were identified from Raman spectra, which changed from monomers to a dimer-rich phase and finally to a phase containing larger, disordered C70 oligomers.
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15.
  • Ma, Tao, et al. (författare)
  • Genomic insights into salt adaptation in a desert poplar
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 2797-
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite the high economic and ecological importance of forests, our knowledge of the genomic evolution of trees under salt stress remains very limited. Here we report the genome sequence of the desert poplar, Populus euphratica, which exhibits high tolerance to salt stress. Its genome is very similar and collinear to that of the closely related mesophytic congener, P. trichocarpa. However, we find that several gene families likely to be involved in tolerance to salt stress contain significantly more gene copies within the P. euphratica lineage. Furthermore, genes showing evidence of positive selection are significantly enriched in functional categories related to salt stress. Some of these genes, and others within the same categories, are significantly upregulated under salt stress relative to their expression in another salt-sensitive poplar. Our results provide an important background for understanding tree adaptation to salt stress and facilitating the genetic improvement of cultivated poplars for saline soils.
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16.
  • Wang, Lin, et al. (författare)
  • High-pressure studies of Nano/sub-micrometer C70 rods
  • 2005
  • Ingår i: High Energy Physics and Nuclear Physics B. - 0254-3052. ; 29:Supplement, s. 112-115
  • Tidskriftsartikel (refereegranskat)abstract
    • We have successfully synthesized C-70 rods in nano/sub-micrometers scale by evaporating solvent method. The diameter of the as grown C-70 rods is similar to 500 nm, and the length is similar to 10 mu m. The EDXD pattern and Raman spectroscopy for as -grown sample indicate that the as grown C-70 rod is in hcp structure. The pressure-induced structural phase transition has been studied by using DAC combined with EDXD and Raman spectroscopy methods under quasi-hydrostatic pressure up to 26.1GPa. It is found that hcp structure transforms into amorphous phase for C-70 rods in the pressure range from 23.3 to 26.1GPa, which is higher than the transformation pressure for bulk C-70 crystals. The phase transition is irreversible and it is induced by the collapse of C-70 cage.
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17.
  • Yang, Xigui, et al. (författare)
  • Novel Superhard sp3 Carbon Allotrope from Cold-Compressed C70 Peapods
  • 2017
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 118:24
  • Tidskriftsartikel (refereegranskat)abstract
    • Design and synthesis of new carbon allotropes have always been important topics in condensed matter physics and materials science. Here we report a new carbon allotrope, formed from cold-compressed C70 peapods, which most likely can be identified with a fully sp3-bonded monoclinic structure, here named V carbon, predicted from our simulation. The simulated x-ray diffraction pattern, near K-edge spectroscopy, and phonon spectrum agree well with our experimental data. Theoretical calculations reveal that V carbon has a Vickers hardness of 90 GPa and a bulk modulus ∼400  GPa, which well explains the "ring crack" left on the diamond anvils by the transformed phase in our experiments. The V carbon is thermodynamically stable over a wide pressure range up to 100 GPa, suggesting that once V carbon forms, it is stable and can be recovered to ambient conditions. A transition pathway from peapod to V carbon has also been suggested. These findings suggest a new strategy for creating new sp3-hybridized carbon structures by using fullerene@nanotubes carbon precursor containing odd-numbered rings in the structures.
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18.
  • Yao, Mingguang, et al. (författare)
  • Tailoring Building Blocks and Their Boundary Interactionfor the Creation of New, Potentially Superhard, Carbon Materials
  • 2015
  • Ingår i: Advanced Materials. - : John Wiley & Sons. - 0935-9648 .- 1521-4095. ; 27:26, s. 3962-3968
  • Tidskriftsartikel (refereegranskat)abstract
    • A strategy for preparing hybrid carbon structures with amorphous carbon clusters as hard building blocks by compressing a series of predesigned two-component fullerides is presented. In such constructed structures the building blocks and their boundaries can be tuned by changing the starting components, providing a way for the creation of new hard/superhard materials with desirable properties.
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19.
  • 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 .- 1361-648X. ; 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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20.
  • 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. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:18, s. 181925-
  • Tidskriftsartikel (refereegranskat)abstract
    • C60nanorods in two polymeric phases have been synthesized under differenthigh pressure and high temperature conditions. Orthorhombic and tetragonal phaseshave been identified from Raman spectra. The rod shape canbe kept under quasihydrostatic pressure. The photoluminescence intensity of thepolymeric C60 nanorods has been greatly enhanced compared with thatof pristine C60 nanorods. The main fluorescence band shifted from730  nm in the unpolymeric phase to 748  nm and near infrared780  nm in the orthorhombic and tetragonal phases, respectively. The enhancedphotoluminescence with tunable frequency for different polymeric C60 nanorods suggestspotential applications in luminescent nanomaterials.
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21.
  • Hou, Yuanyuan, et al. (författare)
  • Pressure-induced polymerization of nano- and submicrometer C60 rods into a rhombohedral phase
  • 2006
  • Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 423:1-3, s. 215-219
  • Tidskriftsartikel (refereegranskat)abstract
    • C-60 rods with nano- and submicrometer dimensions were polymerized at 4.5 GPa and 973 K. Raman spectroscopy showed that the material transformed into a rhombohedral polymeric structure under high pressure and high temperature (HPHT) conditions. The HPHT polymerized samples keep the original rod shape. The position dependence of photoluminescence (PL) spectra have been studied on the rhombohedral polymer C60 rods at room temperature. The intensity of the 1.74 eV peak from the rhombohedral phase varies systematically between the edge of and the middle of the rod. Our results indicate that the 1.74 eV peak originates from surface defects.
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22.
  • Liu, Bingbing, et al. (författare)
  • High pressure and high temperature induced polymeric C60 nanocrystal
  • 2008
  • Ingår i: Diamond and related materials, vol. 17, issue 4-5. - Amsterdam : Elsevier B.V.. ; , s. 620-623
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, C60 nanosheets with polymeric phases have been obtained under various high pressures and high temperatures, including orthorhombic and tetragonal polymeric phases. The structures have been identified and compared with those of nanorods by photoluminescence and Raman spectroscopies. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The difference of photoluminescence and Raman spectra between nanosheets and nanorods samples treated under the same conditions is probably caused by different polymerization degree in these samples because of different shapes.
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23.
  • Liu, Dedi, et al. (författare)
  • Synthesis and solid-state studies of self-assembled C60 microtubes
  • 2011
  • Ingår i: Diamond and Related Materials, vol. 20 issue 2. - : Elsevier BV. ; , s. 178-182
  • Konferensbidrag (refereegranskat)abstract
    • C60 microtubes were fabricated by a modified solution evaporation method, evaporating a solution of C60 in toluene in an atmosphere of m-xylene at room temperature. The C60 microtubes have outer diameters ranging from 2 to 8 μm. IR spectra, TG analysis and X-ray diffraction showed a solvated structure for the as-grown C60 microtubes. Through a gentle heat-treatment in vacuum, pure C60 microtubes with single crystalline fcc structure were obtained after the elimination of solvents. It is suggested that the C60 microtubes form through self-assembly from several individual C60 nanorods.
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24.
  • Ma, Honglei, et al. (författare)
  • Synchrotron X-ray diffraction and infrared spectroscopy studies of C60H18 under high pressure
  • 2010
  • Ingår i: The 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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25.
  • Shang, Yuchen, et al. (författare)
  • Enhancement of short/medium-range order and thermal conductivity in ultrahard sp3 amorphous carbon by C70 precursor
  • 2023
  • Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
  • Tidskriftsartikel (refereegranskat)abstract
    • As an advanced amorphous material, sp3 amorphous carbon exhibits exceptional mechanical, thermal and optical properties, but it cannot be synthesized by using traditional processes such as fast cooling liquid carbon and an efficient strategy to tune its structure and properties is thus lacking. Here we show that the structures and physical properties of sp3 amorphous carbon can be modified by changing the concentration of carbon pentagons and hexagons in the fullerene precursor from the topological transition point of view. A highly transparent, nearly pure sp3−hybridized bulk amorphous carbon, which inherits more hexagonal-diamond structural feature, was synthesized from C70 at high pressure and high temperature. This amorphous carbon shows more hexagonal-diamond-like clusters, stronger short/medium-range structural order, and significantly enhanced thermal conductivity (36.3 ± 2.2 W m−1 K−1) and higher hardness (109.8 ± 5.6 GPa) compared to that synthesized from C60. Our work thus provides a valid strategy to modify the microstructure of amorphous solids for desirable properties.
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26.
  • Shang, Yuchen, et al. (författare)
  • Ultrahard bulk amorphous carbon from collapsed fullerene
  • 2021
  • Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 599:7886, s. 599-604
  • Tidskriftsartikel (refereegranskat)abstract
    • Amorphous materials inherit short- and medium-range order from the corresponding crystal and thus preserve some of its properties while still exhibiting novel properties1,2. Due to its important applications in technology, amorphous carbon with sp2 or mixed sp2–sp3 hybridization has been explored and prepared3,4, but synthesis of bulk amorphous carbon with sp3 concentration close to 100% remains a challenge. Such materials inherit the short-/medium-range order of diamond and should also inherit its superior properties5. Here, we successfully synthesized millimetre-sized samples—with volumes 103–104 times as large as produced in earlier studies—of transparent, nearly pure sp3 amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary. The material synthesized consists of many randomly oriented clusters with diamond-like short-/medium-range order and possesses the highest hardness (101.9 ± 2.3 GPa), elastic modulus (1,182 ± 40 GPa) and thermal conductivity (26.0 ± 1.3 W m−1 K−1) observed in any known amorphous material. It also exhibits optical bandgaps tunable from 1.85 eV to 2.79 eV. These discoveries contribute to our knowledge about advanced amorphous materials and the synthesis of bulk amorphous materials by high-pressure and high-temperature techniques and may enable new applications for amorphous solids.
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27.
  • Wang, Lin, et al. (författare)
  • Highly Enhanced Luminescence from Single-Crystalline C60·1m-xylene Nanorods
  • 2006
  • Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 18:17, s. 4190-4194
  • Tidskriftsartikel (refereegranskat)abstract
    • Single-crystalline C60â1m-xylene nanorods with a hexagonal structure were successfully synthesizedby evaporating a C60 solution in m-xylene at room temperature. The ratio of the length to the diameterof the nanorods can be controlled in the range of 10 to over 1000 for different applications. Thephotoluminescence (PL) intensity of the nanorods is about 2 orders of magnitude higher than that forpristine C60 crystals in air. Both UV and Raman results indicate that there is no charge transfer betweenC60 and m-xylene. It was found that the interaction between C60 and m-xylene molecules is of the vander Waals type. This interaction reduces the icosahedral symmetry of C60 molecule and induces strongPL from the solvate nanorods.
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28.
  • Wang, Lin, et al. (författare)
  • Synthesis of thin, rectangular C60 nanorods using m-xylene as shape controller
  • 2006
  • Ingår i: Advanced Materials. - : Wiley Interscience. - 0935-9648 .- 1521-4095. ; 18:14, s. 1883-1888
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin, rectangular C60 nanorods in face-centered cubic structure are synthesized by using m-xylene as a shape controller. These unusual nanorods can easily grow on various substrates. The smallest nanorods have widths smaller than 30 nm. The nanorods are highly crystalline in single phase. A significant expansion of the lattice constant is also found in the C60 nanorods when their widths decrease below about 80 nm. 
  •  
29.
  • Yang, Xigui, et al. (författare)
  • Polarized Raman study of aligned multiwalled carbon nanotubes arrays under high pressure
  • 2015
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:49, s. 27759-27767
  • Tidskriftsartikel (refereegranskat)abstract
    • Tuning the intertube interaction and the topological structure of carbon nanotubes by the application of pressure may obviously affect their properties such as optical and electronic properties. However, characterizing such changes is still challenging. Here, we performed polarized Raman scattering studies on aligned multiwalled carbon nanotube arrays (MWNTAs). Unlike researchers from the previous literature, we found that the MWNTAs exhibit a polarization dependence similar to that of isolated single walled carbon nanotubes at ambient conditions. Upon compression, the polarization dependence weakens gradually with increasing pressure up to ∼20 GPa, which has been discussed in terms of pressure-induced enhancement of intertube interactions. At around 20 GPa, the depolarization effect vanishes, which can be explained by the formation of interlinked sp3 bonding in the MWNTAs. Our results show that polarized Raman spectroscopy is an efficient method to explore not only intertube interaction but also structural transition changes in MWNTs, which overcome the difficulty that MWNTs have no obvious fingerprints like those of single-walled carbon nanotubes in the study of structural transformations.
  •  
30.
  • Yang, Zhenxing, et al. (författare)
  • Anomalous phonon softening of G-band in compressed graphitic carbon nitride due to strong electrostatic repulsion
  • 2021
  • Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 118:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Graphitic carbon nitride (C2N and C3N) with various p electron distributions on layers have been studied under pressure through acombined theoretical and experimental approach and a comparison with graphite. It is found that as these materials transform into lowcompressibility phases in the pressure range from 15 to 45 GPa, strong electrostatic repulsion between p electrons and in-plane sp2 electronsmay distort and soften the sp2 bonds, leading to anomalous pressure evolutions of the intralayer phonon vibrations, such as a plateau-likebehavior of E2g mode (G-band) in C2N and C3N. This also causes a slow increase in the resistivity/resistance of C2N and C3N as pressureincreases, and the gradual interlayer bonding leads to an abrupt increase in resistance of the materials but with different pressure responsesdue to their different p electron distributions. Moreover, the intensity enhancement of the G band in both CN materials may be related totheir electronic structure changes. The results deepen our understanding of the effects of p electron distribution on the structural transitionof graphitic materials and may explain some unexplained in previous studies.
  •  
31.
  • Yao, Mingguang, et al. (författare)
  • Pressure-induced transformation and superhard phase in fullerenes : the effect of solvent intercalation
  • 2013
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:7, s. 071913-
  • Tidskriftsartikel (refereegranskat)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.
  •  
32.
  • Yao, Mingguang, et al. (författare)
  • Synthesis of differently shaped C(70) nano/microcrystals by using various aromatic solvents and their crystallinity-dependent photoluminescence
  • 2012
  • Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 50:1, s. 209-215
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a simple synthesis of Cm microcrystals by a fast solvent-assisted evaporation method by selectively using aromatic solvents with halogen radicals as a controller. In a detailed analysis we show that depending on solvent, C(70) concentration in the solution, and synthesis temperature both C(70) microrods and microcubes can be produced. The samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. From meta-type solvents microrods or microcrystal cubes grow with a single orthorhombic or a monoclinic structure or a mixture of both. These crystals show traces of solvents in the structure. From para-type solvents cubic (or rectangular) crystals grow with a hexagonal structure and with no trace of solvents. Room temperature photoluminescence (PL) of the C(70) crystal samples reveals that the PL efficiency of the crystals increases with crystalline order and that the best crystalline Cm cube crystals show 10 times higher PL efficiency than that of pristine C(70) polycrystalline samples. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
33.
  • Yao, Mingguang, et al. (författare)
  • Uniaxial-stress-driven transformation in cold compressed glassy carbon
  • 2017
  • Ingår i: Applied Physics Letters. - Melville : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 111:10
  • Tidskriftsartikel (refereegranskat)abstract
    • We show that transformation of glassy carbon (GC) into a translucent superhard carbon phase by cold-compression is obtained in the presence of a uniaxial stress field. This transition accompanies with sp(2) to sp(3) bonding change in GC, and it is found that the uniaxial stress strongly favors this bonding transition. The transformation of GC causes photoluminescence and significantly increases light transmissivity. Upon decompression, the high pressure phase can be maintained under large uniaxial stress at a chamber pressure even down to similar to 10GPa. We discuss possible mechanisms of these transitions by a distinct bonding process that occurs in noncrystalline carbon.
  •  
34.
  • Yin, Xiu, et al. (författare)
  • Doping of charge-transfer molecules in cocrystals for the design of materials with novel piezo-activated luminescence
  • 2023
  • Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:6, s. 1479-1484
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel piezo-activated luminescent material with wide range modulation of the luminescence wavelength and a giant intensity enhancement upon compression was prepared using a strategy of molecular doping. The doping of THT molecules into TCNB-perylene cocrystals results in the formation of a weak but pressure-enhanced emission center in the material at ambient pressure. Upon compression, the emissive band from the undoped component TCNB-perylene undergoes a normal red shift and emission quenching, while the weak emission center shows an anomalous blue shift from 615 nm to 574 nm and a giant luminescence enhancement up to 16 GPa. Further theoretical calculations show that doping by THT could modify intermolecular interactions, promote molecular deformation, and importantly, inject electrons into the host TCNB-perylene upon compression, which contributes to the novel piezochromic luminescence behavior. Based on this finding, we further propose a universal approach to design and regulate the piezo-activated luminescence of materials by using other similar dopants.
  •  
35.
  • 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. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 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.
  •  
36.
  • Cui, Wen, et al. (författare)
  • High pressure and high temperature induced polymerization of doped C60 materials
  • 2016
  • Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 109, s. 269-275
  • Tidskriftsartikel (refereegranskat)abstract
    • Several metastable doped C60 polymers are synthesized under high pressure and high temperature (1.5GPa, 573K and 2GPa, 700K, respectively), using C60/ferrocene (Fc, Fe(C5H5)2), C60/Ni(OEP) and C60/AgNO3 as starting materials. Raman and IR spectroscopy are used to study the polymerization of these samples after HPHT treatment. It is found that the polymerization degree is always lower than that of pure C60 treated at same conditions, which is attributed to the space limitation by the dopants. We also find that even at same conditions, the three doped materials form different polymeric phases of the doped materials. This is attributed to the unique initial lattice structures and the different degrees of spatial confinement provided by the dopants.
  •  
37.
  • Cui, Wen, et al. (författare)
  • Pressure induced metastable polymerization in doped C60 materials
  • 2017
  • Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 115, s. 740-745
  • Tidskriftsartikel (refereegranskat)abstract
    • High pressure Raman studies have been carried out on C60/AgNO3 and C60/Ni(OEP) up to 30 GPa. In both these doped C60 materials, pressure-induced metastable ordered polymers can be observed after pressure release. The results show that both the quenched materials contain chainlike polymers and dimers. We also find that the degree of polymerization is higher in these doped C60 materials than in bulk C60 materials after similar high pressure treatment and that C60/AgNO3 contains a higher fraction of chainlike polymers than C60/Ni(OEP) after decompression from same pressure. The results can be understood by considering the different initial lattice structures of these materials and the confinement effects of the dopants.
  •  
38.
  • Dong, Jiajun, et al. (författare)
  • Decompression-Induced Diamond Formation from Graphite Sheared under Pressure
  • 2020
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 124:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Graphite is known to transform into diamond under dynamic compression or under combined high pressure and high temperature, either by a concerted mechanism or by a nucleation mechanism. However, these mechanisms fail to explain the recently reported discovery of diamond formation during ambient temperature compression combined with shear stress. Here we report a new transition pathway for graphite to diamond under compression combined with shear, based on results from both theoretical simulations and advanced experiments. In contrast to the known model for thermally activated diamond formation under pressure, the shear-induced diamond formation takes place during the decompression process via structural transitions. At a high pressure with large shear, graphite transforms into ultrastrong sp3 phases whose structures depend on the degree of shear stress. These metastable sp3 phases transform into either diamond or graphite upon decompression. Our results explain several recent experimental observations of low-temperature diamond formation. They also emphasize the importance of shear stress for diamond formation, providing new insight into the graphite-diamond transformation mechanism.
  •  
39.
  • Du, Mingrun, et al. (författare)
  • High pressure and high temperature induced polymerization of C60 solvates : The effect of intercalated aromatic solvents
  • 2021
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:31, s. 17155-17163
  • Tidskriftsartikel (refereegranskat)abstract
    • The polymerization of three typical aromatic solvent-doped fullerene materials with similar hexagonal closest packed (hcp) structures (mesitylene/C60, m-dichlorobenzene/C60 and m-xylene/C60 solvates) is studied under high pressure and high temperature (HPHT, 1.5 GPa, 573 K and 2 GPa, 700 K, respectively). Raman and photoluminescence spectroscopies reveal that the intercalated aromatic solvents play a crucial role in tailoring the extent of polymerization of C60 molecules. In the solvates, the solvents confine formation of covalent bonds between C60 molecules to the 001 direction and the (001) plane of the hcp lattices, leading to the formation of mixed polymeric phases of monomers, dimers, one-dimensional (1D) chainlike oligomers, and two-dimensional (2D) tetragonal phase polymers under suitable HPHT conditions. The type and number of substituent groups of the aromatic solvents are found to have significant influence, determining the amounts and types of polymeric phases formed. Our studies enrich the understanding of the formation mechanisms for controllably fabricating polymeric fullerenes and facilitate targeted design and synthesis of unique fullerene-based carbon materials.
  •  
40.
  • Huang, Xiaoli, et al. (författare)
  • High-temperature superconductivity in sulfur hydride evidenced by alternating-current magnetic susceptibility
  • 2019
  • Ingår i: National Science Review. - : Oxford University Press. - 2095-5138 .- 2053-714X. ; 6:4, s. 713-718
  • Tidskriftsartikel (refereegranskat)abstract
    • The search for high-temperature superconductivity is one of the research frontiers in physics. In the sulfur hydride system, an extremely high Tc (∼200 K) has been recently developed at pressure. However, the Meissner effect measurement above megabar pressures is still a great challenge. Here, we report the superconductivity identification of sulfur hydride at pressure, employing an in situ alternating-current magnetic susceptibility technique. We determine the superconducting phase diagram, finding that superconductivity suddenly appears at 117 GPa and Tc reaches 183 K at 149 GPa before decreasing monotonically with increasing pressure. By means of theoretical calculations, we elucidate the variation of Tc in the low-pressure region in terms of the changing stoichiometry of sulfur hydride and the further decrease in Tc owing to a drop in the electron–phonon interaction parameter λ. This work provides a new insight into clarifying superconducting phenomena and anchoring the superconducting phase diagram in the hydrides.
  •  
41.
  • Li, Lianhui, et al. (författare)
  • Decision-making of product-service system solution selection based on integrated weight and technique for order preference by similarity to an ideal solution
  • 2020
  • Ingår i: IET Collaborative Intelligent Manufacturing. - : The Institution of Engineering and Technology. - 2516-8398. ; 2:3, s. 102-108
  • Tidskriftsartikel (refereegranskat)abstract
    • Product-service system (PSS) solution selection is of great significance to better meet the personalised needs of customers and ensure the subsequent implementation. The problems of incomplete index system, difficulty to obtain the value of the qualitative index and unreasonable single index weighting have a significant impact on the decision-making of PSS solution selection. In response to these problems, a decision-making framework of PSS solution selection is constructed. A comprehensive index system is established from the perspectives of multiple stakeholders. Expert evaluating with the fuzzy number and multi-expert evaluation opinion combination is adopted for index value solving. Integration of objective and subjective weights is achieved based on the multi-weight information consistency model and the candidate PSS solutions are ranked by technique for order preference by similarity to an ideal solution finally. An application case of automobile PSS solution selection is given to verify the effectiveness and rationality of the constructed decision-making framework.
  •  
42.
  • Li, Lianhui, et al. (författare)
  • Sustainability Assessment of Intelligent Manufacturing Supported by Digital Twin
  • 2020
  • Ingår i: IEEE Access. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536. ; 8, s. 174988-175008
  • Tidskriftsartikel (refereegranskat)abstract
    • As a major challenge and opportunity for traditional manufacturing, intelligent manufacturing is facing the needs of sustainable development in future. Sustainability assessment undoubtedly plays a pivotal role for future development of intelligent manufacturing. Aiming at this, the paper presents the digital twin driven information architecture of sustainability assessment oriented for dynamic evolution under the whole life cycle based on the classic digital twin mapping system. The sustainability assessment method segment of the architecture includes indicator system building, indicator value determination, indicator importance degree determination and intelligent manufacturing project assessing. A novel approach for treating the ambiguity of expert judgment in indicator value determination by introducing trapezoidal fuzzy number into analytic hierarchy process is proposed, while the complexity of the influence relationship among the indicators is processed by the integration of complex networks modeling and PROMETHEE II for the indicator importance degree determination. A two-stage evidence combination model based on evidence theory is built for intelligent manufacturing project assessing lastly. The presented digital-twin-driven information architecture and the sustainability assessment method is tested and validated on a study of sustainability assessment of 8 intelligent manufacturing projects of an air conditioning enterprise. The results of the presented method were validated by comparing them with the results of the fuzzy and rough extension of the PROMETHEE II, TOPSIS and VIKOR methods, indicator importance degree determining method by entropy and indicator value determining method by accurate expert scoring.
  •  
43.
  • Liu, Bingbing, et al. (författare)
  • A facile solution method to synthesis of C60 nanorods
  • 2006
  • Ingår i: Materials Research Society Symposium Proceedings vol. 963. - Warrendale : Materials Research Society. ; , s. 49-54
  • Konferensbidrag (refereegranskat)abstract
    • We report here a facile solution method to synthesis of C60 nanorods. A very simple and effective solvent, neat m-xylene, from which C60 can rapidly grow into individual novel nanorods with widths and thicknesses of the order of nanometers was found as a shape controller. These unusual nanorods can easily grow on various substrates such as glass and silicon, and nanorods with different diameters and length-to-diameter ratios can be synthesized under different growth conditions. The smallest nanorods we obtained have widths smaller than 30 nm. The nanorods obtained are highly crystalline and single phase.
  •  
44.
  • Liu, Bingbing, et al. (författare)
  • Bromine doped single-walled carbon nanotubes
  • 2001
  • Ingår i: Nanotubes and Related Materials. - Warrendale : Materials Research Society. - 1558995439 ; , s. A13.36-
  • Konferensbidrag (refereegranskat)abstract
    • Raman spectra for three SWNT samples doped with Br2 were studied using different excitation energies, 2.41 eV and 1.58 eV. One sample was also studied under high pressure up to 2GPa. The vibrations in the low frequency range behave similarly for all samples. With an excitation energy of 1.58eV, additional peaks at ca 240 cm-1 and 209 cm-1 are observed. With increasing pressure, the peak at 209 cm-1 gradually softens by 2~3 cm-1 and becomes very weak at 1.7 GPa, while a new broader peak at ca 250 cm-1 remains constant up to 2 GPa. A number of high intensity overtone modes are observed under high pressure. These results indicate that the vibrations are attributed to bromine, not to the breathing modes of SWNTs, and that bromine resides in the bundles, possibly also inside tubes as a form of polymer.
  •  
45.
  • Liu, Bingbing, et al. (författare)
  • Effects of silver films with different nano-particle sizes on SERS of single-walled carbon nanotubes
  • 2005
  • Ingår i: Chemical Journal of the Chinese Universities. - 0251-0790. ; 26:10, s. 1930-1933
  • Tidskriftsartikel (refereegranskat)abstract
    • Surface-enhanced Raman scattering (SERS) spectra of single-walled carbon nanotubes (SWCNTs) on silver films with different nano-particle sizes from 20 to 100 nm deposited on quartz and glass substrates were studied systematically. The characteristic Raman spectral features of SWCNT G-band and D-band were analyzed. The two bands show a similar tendency with the change of nano-particle size of silver on quartz and glass substrates. The position and the intensity of the G-band are less sensitive to the films' silver particle sizes in the studied range, indicating that hexagonal carbon rings are stable and have a weak interaction with silver films. The shape of the D-band depends on the silver size. The smaller the silver particle size, the more the contribution of high frequency vibrations to the D-band, indicating that disorder carbon has a strong interaction with the active silver films.
  •  
46.
  • 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 .- 1879-2766. ; 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.
  •  
47.
  • Liu, Bingbing, et al. (författare)
  • High pressure and high temperature induced polymeric C60 nanorods and their photoluminiscence properties.
  • 2007
  • Ingår i: Materials Research at High Pressure. - Warrendale : Maerials Research Society. - 9781558999442 ; , s. 99-103
  • Konferensbidrag (refereegranskat)abstract
    • We report that C60 nanorods of three polymeric phases have been synthesized under high pressure and high temperature and that the photoluminescence properties of these polymeric nanorods also have been studied. C60 nanorods were fabricated by a facile solution evaporation method. Raman spectra indicate that this material transformed into orthorhombic, tetragonal and rhombohedral polymeric phases under various high pressure and high temperature conditions. SEM measurements show that the shape of the nanorods can be kept under quasi-hydrostatic pressure condition. The photoluminescence intensity of the polymeric C60 nanorods has been enhanced compared with that of the pristine C60 nanorods. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The enhanced fluorescence with adjustable frequency for different polymeric C60 nanorods makes possible potential application in luminescent nanomaterials.
  •  
48.
  • Liu, Bingbing, et al. (författare)
  • High-pressure induced polymerization of C60 nanorods
  • 2005
  • Ingår i: Proceedings of the Joint 20th AIRAPT and 43rd EHPRG Conf. on High Pressure Science and Technology, Karlsruhe 2005. - 3923704496 ; , s. Nanomat-O133
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • C60 nanorods, about 200 nm in diameter and several micrometers in length and with a rectangular cross section, have been synthesized by a simple solution-growth method. Raman spectroscopy and TEM indicate that the C60 nanorods have a fcc crystalline structure similar to that of pristine C60. Nanorods were polymerized at high temperature and high pressure below 2 GPa. Two different polymeric structures, orthorhombic and tetragonal as determined by Raman spectroscopy, have been obtained under different high temperature and high pressure conditions. The high-pressure induced polymeric samples keep the original nanometer scale rod shape.
  •  
49.
  • Liu, Bingbing, et al. (författare)
  • Raman study of bromine-doped single-walled carbon nanotubes under high pressure
  • 2002
  • Ingår i: Journal of Physics: Condensed Matter vol. 14 issue no. 44. - Bristol : Institute of Physics. ; , s. 11255-11259
  • Konferensbidrag (refereegranskat)abstract
    • Raman results for different single-walled carbon nanotube bundles doped withBr2 were studied both at ambient pressure and under high pressure up to 6 GPa.Our study indicates that bromine resides in the interstitial channel of nanotubebundles as a form of polymer.
  •  
50.
  • 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. - 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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