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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of the graphitization of dispersed diamonds at "low" temperatures (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4380-4388 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bulk density of graphitized ultradisperse diamond (UDD) was measured by a gamma-ray attenuation method at 1370–1870 K. These data combined with small angle x-ray scattering and true density measurements of the samples heated at various fixed temperatures were used to study the graphitization kinetics of the UDD. The reaction rate was modeled as a migration rate of the interface between the developing graphite-like carbon and the remaining diamond phase. A "reducing sphere" model was used to obtain the rates from the changes in densities. The estimated kinetic parameters in an Arrhenius expression, namely the activation energy, E=45±4 kcal/mol, and the pre-exponential factor, A=74±5 nm/s, allow quantitative calculations of the diamond graphitization rates in and around the indicated temperature range. The calculated graphitization rates agree well with the graphitization rates of diamonds with different dispersity estimated from high-resolution transmission electron microscopy data. The large difference between the rates and the kinetic parameters obtained in this study and those estimated by G. Davies and T. Evans [Proc. R. Soc. London 328, 413 (1972)] for the temperature range 2150–2300 K indicates that there are different graphitization mechanisms operating in the "low" and "high" temperatures regions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289791
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical study of the formation of closed curved graphite-like structures during annealing of diamond surface (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 863-870 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In recent high resolution transmission electron microscopic studies we have found that high temperature vacuum annealing (1200–1800 K) of ultradispersed (2–5 nm) and micron size diamond produces fullerene-like graphitic species, namely, onion-like carbon and closed curved graphite structures (multilayer nanotubes and nanofolds), respectively. Here we undertake theoretical studies to help in the understanding of the experimental data for these systems. (1) Calculations of cluster models by a standard semiempirical method (MNDO a software package) are used to explain the preferential exfoliation of {111} planes over other low index diamond planes. (2) The same approach suggests the likelihood that the graphitization is initiated by a significant thermal displacement of a single carbon atom at temperatures close to the Debye temperature. (3) At the diamond–graphite interface we have observed the formation of two curved graphitic sheets from three diamond {111} planes. We suggest that the evolution of this interface proceeds by a "zipper"-like migration mechanism with the carbon atoms of the middle diamond layer being distributed equally between the two growing graphitic sheets. (4) The observed mosaic packaging of closed curved graphite structures during the diamond surface graphitization is suggested to be a self-assembling process. This process is explained in terms of the "stretching" of a bowed graphite hexagonal network. The stretch is due to the fact that, if relaxed, the network would be smaller than the initially transformed hexagonal diamond (111), and to the increased separation between the separated sheet and the surface. The initial phase of the process is studied quantitatively using a molecular mechanics simulation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370816
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  • 3
    Electronic Resource
    Electronic Resource
    Vacancy Ordering in γ-Fe2O3: Synchrotron X-ray Powder Diffraction and High-Resolution Electron Microscopy Studies (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 141-145 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: This paper reports synchrotron X-ray powder diffraction and high-resolution electron microscopy studies of the structural arrangement in γ-Fe2O3. Powder diffraction data as well as high-resolution electron microscopy show that the basic structure of γ-ferric oxide possesses cubic symmetry (space group P4332), whereas the ordered distribution of the cation vacancies on the octahedral positions results in the formation of the tetragonal superlattice (space group P41212). The character of the superstructure orientation with respect to the developed planes of the γ-Fe2O3 microcrystals obtained by different preparative techniques is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889894010113
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical and morphological characterization of a direct methanol fuel cell based on a quaternary Pt-Ru-Sn-W/C anode (1996)
    Springer
    Journal of applied electrochemistry 26 (1996), S. 959-967 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Conventional and ‘paste process’ methods were investigated to fabricate the membrane/electrode assembly (M&E) for application in a vapour-feed direct methanol fuel cell. A quaternary Pt-RuSn-W/C and a Pt/C catalysts were employed for methanol oxidation and oxygen reduction, respectively. The structure and chemical composition of the catalysts were investigated by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). A crystalline Pt f.c.c. phase was found to prevail in both catalysts. Agglomeration and twinned particles were frequently observed in the Pt-Ru-Sn-W/C catalyst. Electrochemical investigations were performed by a.c.-impedance spectroscopy and galvanostatic polarization. The ‘paste process’ based assembly showed a significantly lower uncompensated resistance and an approximately two-fold power density increase with respect to the conventional assembly. According to the scanning electron microscopy analysis the observed results were attributed to improved bonding between catalysts and perfluorosulfonic membrane and to a larger extension of the three-phase reaction zone in the ‘paste process’ based assembly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242049
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  • 5
    Electronic Resource
    Electronic Resource
    Illusion of New Polytypes (2000)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 338-342 (May 2000), p. 533-536 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/04/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.338-342.533.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Analysis of Strain and Defect Formation of Low-Dimensional Structures in SiC (2001)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 353-356 (Jan. 2001), p. 259-262 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/05/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.353-356.259.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of 3-Fold Periodicity in 3C-SiC Layers Grown by MBE (1998)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 264-268 (Feb. 1998), p. 259-264 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/03/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.264-268.259.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Role of the curvature of atomic layers in electron field emission from graphitic nanostructured carbon (1999)
    Springer
    JETP letters 69 (1999), S. 411-417 
    Details
    ISSN: 1090-6487
    Keywords: 79.70.+q ; 73.61.Tm ; 81.15.Gh ; 36.40.−c
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Layers of oriented carbon nanotubes and nanometer-size plate-shaped graphite crystallites are obtained by chemical vapor deposition in a glow-discharge plasma. A structural-morphological investigation of a carbon material consisting of nanotubes and nanocrystallites is performed, and the field-emission properties of the material are also investigated. It is shown that electron field emission is observed in an electric field with average intensity equal to or greater than 1.5 V/μm. The low fields giving rise to electron emission can be explained by a decrease in the electronic work function as a result of the curvature of the atomic layers of graphitic carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.568043
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  • 9
    Electronic Resource
    Electronic Resource
    Structure of polynuclear palladium(ii) hydroxocomplexes formed upon alkaline hydrolysis of palladium(ii) chloride complexes (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 1822-1826 
    Details
    ISSN: 1573-9171
    Keywords: palladium(ii) ; hydrolysis ; polynuclear complexes ; EXAFS ; SAXS ; TEM ; size distribution of particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of polynuclear PdII hydroxocomplexes (PHC) formed as a result of alkaline hydrolysis of PdII chloride complexes was studied by EXAFS, SAXS, and TEM methods. It is established that in aqueous solutions a hydroxocomplex particle is a filament curled into a ball containing about 100 Pd atoms. The filament consists of planar coordination squares of PdO4 units linkedvia one or two oxygen bridges of different geometry. Aging of samples results in an increase in the number of single bridging ligands and a decrease in the diameter of particles. Interatomic distances around palladium atoms were determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707203
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  • 10
    Electronic Resource
    Electronic Resource
    Structure of polynuclear palladium(II) hydroxocomplexes and the mechanism of their adsorption by carbon materials (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1296-1302 
    Details
    ISSN: 1573-9171
    Keywords: palladium hydrolysis ; polynuclear hydroxocomplexes (PHC) ; carbon material ; adsorption ; radial atomic distribution method ; X-ray phase analysis ; electron microscopy ; molecule structure modeling ; synthesis of microscopic images
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption of polynuclear palladium(ii) hydroxocomplexes (PHC) by carbon materials (CM) was studied. It was found that PHC are adsorbed from aqueous solutions without a change in their chemical composition and are composed of clusters (〈10 A) with metalmetal distances typical of the PdO chain structure. Three-dimensional ordered particles with the PdO structure were formed upon adsorption of PlIC on carbon materials at room temperature or after the PHC suspension was dried in air at 400 °C (the size of the particles was 15 and 25 A, respectively). Calculation of the electron-microscopic images of the adsorbed PHC with atomic resolution based on crystal structure modeling showed that PdO particles containing -100 palladium atoms is the final product after drying of the adsorbed PHC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01434200
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