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  • 1
    Electronic Resource
    Electronic Resource
    Structural studies of nanoporous carbon produced from silicon carbide (1999)
    Springer
    Physics of the solid state 41 (1999), S. 808-810 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract X-ray diffraction and small-angle scattering study of nanoporous carbon samples prepared from polycrystalline α SiC and single-crystal 6H SiC is reported. The distribution function of carbon nanoclusters in size was found. In α SiC samples, the small size (10–12 Å) of nanoclusters is combined with their high size uniformity. Graphite-like nanoclusters 30–60 Å in size were found in samples of both types. In 6H SiC samples, such clusters make up a notable fraction of the volume. The experimentally observed structural anisotropy of the samples is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130879
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  • 2
    Electronic Resource
    Electronic Resource
    On fractal nature of the structure of nanoporous carbon obtained from carbides (2000)
    Springer
    Physics of the solid state 42 (2000), S. 1176-1181 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The curves describing small-angle x-ray scattering at npor-C nanoporous carbon samples obtained from polycrystalline α-SiC, TiC, and Mo2C and a 6H-SiC single crystal have been analyzed. An algorithm is developed for taking into account the corrections to experimental curves for the intensity of the primary beam transmitted through the sample and the height of the inlet slit in these measurements. Two systems of nanoclusters observed in the npor-C structure differ in the type of stacking of structural elements: small-scale mass fractals of a dimension 1〈D 2〈3 and a size L 2=50–90 Å, which depend on the type of the initial carbide, and large-scale nanoclusters having a size L 1〉550 Å. In most samples, large-scale nanoclusters can be regarded as objects with a fractal surface and a dimension 2〈D 1〈13, which also depends on the type of the initial carbide. Large-scale nanoclusters in npor-C obtained from Mo2C prove to be mass fractals with a dimension D 1〉2. Peculiarities of the structure formation of nanoporous carbon obtained from various carbides are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1131336
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  • 3
    Electronic Resource
    Electronic Resource
    Structural study of nanoporous carbon produced from polycrystalline carbide materials: Small-angle x-ray scattering (1999)
    Springer
    Physics of the solid state 41 (1999), S. 1359-1363 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An x-ray small-angle scattering study is reported of the structure of nanoporous carbon prepared by chlorinating carbide compounds having different crystal structures (SiC, TiC, Mo2C). The measurements were carried out both in reflection and transmission. The angular dependences of the scattering intensity obtained are treated as a result of scattering from nanoparticles of different size. By unfolding the experimental curves into components corresponding to particles with different gyration radii R g, scatterer distribution functions in gyration radius m(R g) were found. It is shown that, irrespective of the type of the starting carbide, particles with R g∼5 Å make up the largest fraction in porous carbon. Samples prepared from different carbides differ in the degree of nanoparticle uniformity in size. The most uniform in size are nanoparticles in the samples prepared from SiC, in which the average value R g av 〈6 Å. Nanoparticles in the porous carbon produced from Mo2C are about twice larger.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130998
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  • 4
    Electronic Resource
    Electronic Resource
    Modification of the electron spectrum and vibrational properties of amorphous carbon by copper doping (1998)
    Springer
    Semiconductors 32 (1998), S. 831-837 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The near-gap electron spectrum and the effective charge distribution in graphite-like carbon nanoclusters of simple geometry in a-C: H containing a single Cu atom are calculated in the tight-binding approximation. Only the coupling between π electrons of the constituent C atoms and one valence s electron of the Cu atom is taken into account. The binding energy of the Cu atom in the clusters and the static dipole moment of the clusters are calculated. The results are invoked to interpret the experimentally observed activation of the Raman G band in the IR spectrum of a-C: H: Cu as a consequence of a lowering of the symmetry of the graphite-like clusters due to copper intercalation. Experimental data on the time dependence of the G band intensity during isothermal annealing of a-C: H: Cu are presented. The data suggest the possibility of reversible transfer of Cu atoms between the impurity states in the copper-carbon clusters and the impurity states in the purely copper clusters. The average activation energies of direct and reverse transfer are estimated from the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1187468
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  • 5
    Electronic Resource
    Electronic Resource
    Charge displacement induced by intercalation of graphite-like nanoclusters in amorphous carbon with copper (1999)
    Springer
    Physics of the solid state 41 (1999), S. 786-788 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Interaction of an impurity Cu atom with carbon in copper-intercalated graphite-like nanoclusters in a-C:H has been considered in a simple tight-binding approximation. Clusters with simple configurations were used to show that partial ionization of Cu gives rise to metallization of a semiconductor cluster and to a substantial charge redistribution in the latter. The presence of copper initiates in the cluster internal polarization with components directed both normal to the graphene-fragment plane and parallel to it. The lowering of the cluster symmetry induced by copper intercalation activates the Raman band G in the IR spectrum of a-C:H.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130873
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Appearance of molecular hydrogen in the ultraviolet spectra of diamond-like carbon (1997)
    Springer
    Technical physics letters 23 (1997), S. 461-463 
    Details
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ultraviolet Raman scattering is used to study the state of hydrogen in diamond-like α-C:H. Scattering lines are observed corresponding to transitions between the rotational states of the hydrogen molecule. The interaction with the α-C:H matrix increases the internuclear distance and perturbs the electronic-vibrational terms of the H2 molecule, so that resonance Raman scattering can be observed, excited by 10.04 eV photons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1261818
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    Paper (German National Licenses)
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