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排序方式: 共有103条查询结果,搜索用时 390 毫秒
1.
Gao J Yu A Itkis ME Bekyarova E Zhao B Niyogi S Haddon RC 《Journal of the American Chemical Society》2004,126(51):16698-16699
Aligned single-walled carbon nanotubes (SWNTs) and hierarchical SWNT assembly were fabricated by electrospinning. The high fiber elongation and high DC electric field applied during the electrospinning process result in the orientation of the SWNTs along the axial direction of the fiber. The alignment of the electropsun composite fiber transfers this local SWNT orientation to macroscopically aligned SWNTs. After removing the polymer component from the aligned composite fiber, we produced large area aligned SWNTs. The results show that the directional control of SWNT alignment and debundling of SWNTs into individual tubes can be simultaneously realized. 相似文献
2.
Sidewall functionalization of single-walled carbon nanotubes by addition of dichlorocarbene 总被引:1,自引:0,他引:1
Hu H Zhao B Hamon MA Kamaras K Itkis ME Haddon RC 《Journal of the American Chemical Society》2003,125(48):14893-14900
We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of dichlorocarbene. The dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl(2)] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the dichlorocarbene precursor. Because the addition of dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the pi-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on dichlorocarbene functionalization. The FIR region of the spectrum allows a clear differentiation between the covalent and the ionic chemistry of SWNTs. In contrast with covalent functionalization, we show that reaction of the SWNTs with bromine vapor leads to a strong increase in absorptions at the Fermi level that is observable in the FIR due to hole doping of the semiconducting SWNTs. Thermal treatment of the (s-SWNT)CCl(2) above 300 degrees C resulted in the breakage of C-Cl bonds, but did not restore the original electronic structure of the SWNTs. 相似文献
3.
G. N. Knyazheva M. G. Itkis S. V. Khlebnikov E. M. Kozulin V. G. Lyapin V. A. Rubchenya W. Trzaska 《Physics of Particles and Nuclei Letters》2008,5(1):21-28
The mass-energy and angular distributions of binary fissionlike fragments produced in the reactions 44Ca + 206Pb and 64Ni + 186W, leading to the same compound nucleus 250No, have been measured at excitation energies of 30 and 40 MeV. The presence of the quasifission component was observed for both systems. But in the case of the 64Ni ion, the quasifission process dominates, while in the case of the 44Ca ion, the main process is the fusion-fission of compound nucleus 250No. From the angular distributions of reaction fragments, the time scales were found for quasifission and fusion-fission for both reactions. 相似文献
4.
Yu Ts Oganessian A. V. Yeremin A. G. Popeko O. N. Malyshev A. V. Belozerov G. V. Buklanov M. L. Chelnokov V. I. Chepigin V. A. Gorshkov S. Hofmann M. G. Itkis A. P. Kabachenko B. Kindler G. Münzenberg R. N. Sagaidak Š Šáro H.-J. Schött B. Štreicher A. V. Shutov A. I. Svirikhin G. K. Vostokin 《The European Physical Journal A - Hadrons and Nuclei》2004,19(1):3-6
The upgraded separator VASSILISSA was used to confirm results of previous experiments on the synthesis of the heavy isotopes of the element 112 obtained in complete-fusion reactions of 48Ca and 238U. An additional reason was the non-observation of any events in the same reaction studied with the BGS separator at Berkeley. Limits of
for the atomic mass number of the observed spontaneously fissioning isotope were measured. The obtained results on the decay mode, half-life and production cross-section are in agreement with those obtained in our first experiment.Received: 10 June 2003, Revised: 29 July 2003, Published online: 2 December 2003PACS:
23.60. + e
decay - 25.70.-z Low and intermediate energy heavy-ion reactions - 25.85.Ca Spontaneous fission - 27.90. + b
相似文献
5.
6.
7.
Bulk superconducting samples of type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ, (Tl, Pb)/Sr-1212, with 0.0 ≤ x ≤ 0.525 were prepared by the conventional one-step solid-state reaction technique. The prepared samples were investigated
using X-ray powder diffraction, electrical resistivity and electron paramagnetic resonance (EPR) measurements. Enhancement
of the phase formation, superconducting transition temperature T
c and hole carriers concentration P was observed up to x = 0.075. For x > 0.075, a reverse trend was observed. EPR spectra were measured at different temperatures (120–290 K) for all prepared samples.
The number of spins N participating in the resonance and the paramagnetic susceptibility χ were calculated as a function of both Ru-content and
temperature. N and χ increased as the Ru-content increased. A linear relationship between logN and 1/T was established, from which the activation energy E
a was calculated as a function of the Ru-content. The temperature dependence of χ was fitted according to Curie–Weiss type
of magnetic behavior. Curie constant C, Curie temperature θ, the effective magnetic moment μ and the electronic specific heat γ were estimated as a function of the Ru-content. 相似文献
8.
9.
R. P. Schmitt T. Botting G. G. Chubarian K. L. Wolf B. J. Hurst H. Jabs M. Hamelin A. Bacak Yu. Ts. Oganessian M. G. Itkis E. M. Kozulin N. A. Kondratiev V. S. Salamatin I. V. Pokrovsky F. Hanappe E. de Goès Brennand A. Huck L. Stuttgé E. Liatard J. Beene R. Varner M. Halbert N. Gan 《Physics of Atomic Nuclei》2003,66(6):1163-1167
The time scales for nuclear fission have been explored using both pre-and postfission neutrons and GDR gamma rays. Four systems were investigated: 133-MeV 16O + 176Yb and 208Pb and 104-MeV 4He + 188Os and 209Bi. Fission fragments were measured in coincidence with PPACs. The neutrons were detected using eight detectors from the DEMON array, while gamma rays were measured using the US BaF2 array. The pre-and postfission gamma rays were determined using moving source fits parallel and perpendicular to the fission fragment emission directions. The time scales for fission for the neutrons were determined using the neutron clock technique. The gamma-ray data were fitted using a statistical model calculation based on the code CASCADE. The results of the fits from both data types were used to extract nuclear friction coefficients, γ, and fission time scales. The γ values ranged from 7 to 20, while the fission times were (31–105)×10?21 s. 相似文献
10.
M. G. Itkis V. N. Okolovich A. Ya. Rusanov G. N. Smirenkin 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(3):433-441
Study of α particles, protons and neutrons emission in reactions induced by16O on Sn targets. The threshold for direct a emission is found to be v/c?0.04 (v velocity of the projectile at the top of the Coulomb barrier) whereas direct protons and neutrons, if any, would be emitted for beam energies higher than 7.8MeV/n. (v/c>0.092). Atv/c 0.092, 90% of the direct a cross section is shown to be incomplete fusion. On116Sn target, besides the main exit channels α4n and αp4n, we observed 2α4n and α2p4n channels where the direct α is followed by evaporation particles. This implies a lower initial angular momentum than for the main channels. 相似文献