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991.
Metal-containing amorphous hydrogenated carbon films are of high interest for industrial applications because of their excellent frictional properties, their high abrasive wear resistance and their electrical conductivity, which can be adjusted in a range of 10–12 orders of magnitude. In order to get insight into the mechanical and electrical properties it is necessary to study the nanostructure of the films. The structure consists of small nanometer sized metallic or carbidic particles, which are embedded in a three dimensional amorphous hydrogen-carbon matrix. Anomalous small angle X-ray scattering (ASAXS) and scanning tunneling microscopy (STM) have been used to determine size- and distance-distributions of the particles as a function of metal content. Problems and restrictions of both methods will be discussed. Furthermore the capabilities of scanning probe techniques to distinguish different materials on a nanometer scale (material contrast) have been studied employing barrier height imaging (dI/dz) and friction force microscopy.Dedicated to Professor Dr. rer. nat. Dr. h. c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
992.
993.
根据中子与天然Zr及其同位素反应的总截面,去弹截面和弹性散射角分布的实验数据,得到一组普适的光学模型势参数;应用得到的光学模型势参数,光学模型,Hauser-Feshbach理论,预平衡反应的激子模型和扭曲波玻恩近似理论,系统计算和分析了中子与90,91,92,94Zr反应的非弹散射角分布和双微分截面,理论结果与实验很好的一致. 相似文献
994.
M.A. Muñoz-Márquez 《Surface science》2004,565(1):1-13
The oxidation of Ni(1 0 0) and Ni(1 1 1) at elevated temperatures and large oxygen exposures, typical of the methods used in the preparation of NiO(1 0 0) films for surface studies, has been investigated by medium energy ion scattering (MEIS) using 100 keV H+ incident ions. Oxide film growth proceeds significantly faster on Ni(1 1 1) than on Ni(1 0 0), but on both surfaces oxide penetration occurs to depths significantly greater than 100 Å with total exposures of 1200 and 6000 L respectively. The metal/oxide interface is extremely rough, with metallic Ni extending to the surface, even for much thicker oxide films on Ni(1 1 1). On Ni(1 1 1), NiO growth occurs with the (1 0 0) face parallel to the Ni(1 1 1) surface and the close-packed 〈1 1 0〉 directions parallel. On Ni(1 0 0) the MEIS blocking curves cannot be reconciled with a single orientation of NiO(1 0 0) (with the 〈1 1 0〉 directions parallel) on the surface, but is consistent with the substantial orientational disorder (including tilt) previously identified by spot-profile analysis LEED. 相似文献
995.
Using a right-angled magnetic air prism, we have achieved a separation of ~10 arcsec between ~2 arcsec wide up and down-spin peaks of 5.4 Å neutrons. The polarised neutron option has thus been introduced into the SUSANS instrument. Strongly spindependent SUSANS spectra have been observed over ±1.3 × 10?4 Å?1 range for several magnetic alloy samples. Spatial pair-distribution functions for the up and down-spins as well as the nuclear and magnetic scattering length density distributions in the micrometer domain, have been deduced from these spectra. 相似文献
996.
C. K. Nisha Sunkara V. Manorama Souvik Maiti K. N. Jayachandran V. K. Aswald P. S. Goyal 《Pramana》2004,63(2):315-320
The interaction of cationic random copolymers of methoxy poly(ethylene glycol) monomethacrylate and (3-(methacryloylamino)propyl) trimethylammonium chloride with oppositely charged surfactant, sodium dodecyl sulphate, and the influence of surfactant association on the polymer conformation have been investigated by small-angle neutron scattering. SANS data showed a positive indication of the formation of RCPSDS complexes. Even though the complete structure of the polyion complexes could not be ascertained, the results obtained give us the information on the local structure in these polymer-surfactant systems. The data were analysed using the log-normal distribution of the polydispersed spherical aggregate model for the local structure in these complexes. For all the systems the median radius and the polydispersity were found to be in the range of 20 ± 2 Å and 0.6 ± 0.05, respectively. 相似文献
997.
It is proved that a sound-soft scatterer in R^N (N = 2, 3) is uniquely determined by a finite number of acoustic far-field measurements. The admissible scatterer possibly consists of finitely many solid obstacles and subsets of (N - 1)- dimensional hyperplanes. 相似文献
998.
Michael J. Fevola Roger D. Hester Charles L. McCormick 《Journal of polymer science. Part A, Polymer chemistry》2003,41(4):560-568
We discuss the synthesis and characterization of polyacrylamide (PAM) homopolymers with carefully controlled molecular weights (MWs). PAM was synthesized via free‐radical solution polymerization under conditions that yield highly linear polymer with minimal levels of hydrolysis. The MW of the PAM homopolymers was controlled by the addition of sodium formate (NaOOCH) to the polymerization medium as a conventional chain‐transfer agent. MWs and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering analysis; for polymerizations carried out to high conversion, PAM MWs ranged from 0.23 to 6.19 × 106 g/mol, with most samples having PDI ≈2.0. Zero‐shear intrinsic viscosities of the polymers were determined via low‐shear viscometry in 0.514 M NaCl at 25 °C. Data derived from the polymer characterization were used to determine the chain‐transfer constant to NaOOCH under the given polymerization conditions and to calculate Mark–Houwink–Sakurada K and a values for PAM in 0.514 M NaCl at 25 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 560–568, 2003 相似文献
999.
Ruckert T. Keune W. Sahoo B. Sturhahn W. Toellner T. S. Alp E. E. Röhlsberger R. 《Hyperfine Interactions》2002,144(1-4):65-76
Hyperfine Interactions - Nuclear resonant inelastic X-ray scattering (NRIXS) of 14.4125 keV synchrotron radiation was used to measure directly the partial vibrational density of states (VDOS),... 相似文献
1000.
J.-F. Colomer L. Henrard Ph. Lambin G. Van Tendeloo 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(1):111-118
The atomic structure of single-wall carbon nanotube bundles produced by three different techniques (laser ablation, electric
arc discharge and catalytic chemical vapor deposition (CCVD)) has been characterized by electron diffraction and microscopy.
Information on the helicity and the lattice packing has been obtained. Concerning the helicity, small bundles produced by
CCVD exhibit only one or two tube helicities within a single bundle. The diffraction patterns of laser-ablation produced bundles
also present well-defined but more diversified chiralities within a single bundle. By contrast the data acquired on bundles
formed by arc discharge show a more diffuse pattern, characteristic of a random chirality dispersion within a single bundle.
Concerning the lattice packing, informations are obtained via a detailed study of the equatorial line of the diffraction pattern for bundles produced by the three techniques. This electron
diffraction study is completed by high-resolution electron microscopy.
Received 8 August 2001 and Received in final form 14 March 2002 相似文献