共查询到20条相似文献,搜索用时 46 毫秒
1.
J. Penuelas P. Andreazza C. Andreazza-Vignolle C. Mottet M. De Santis H. C.N. Tolentino 《The European physical journal. Special topics》2009,167(1):19-25
Nucleation and growth of supported CoPt nanoparticles were studied in situ and in real time by combined grazing incidence small-angle x-ray scattering (GISAXS) and grazing incidence x-ray diffraction
(GIXD). GISAXS provides morphological features of nanoparticles as a function of size, shape and correlation distance between
particles, while GIXD allows the determination of the atomic structure. We focus on the formation of ultrasmall CoPt nanoparticles,
in the 1–4 nm size range at 500○C. The structural analysis method based on the Debye equation is coupled with cluster model calculations performed by Monte
Carlo simulations using a semi-empirical tight-binding potential to interpret diffraction spectra and structural transitions.
Our results show that the cluster structure evolution during the growth is size-dependent and composition-dependent, yielding
an icosahedral to fcc structure transition. 相似文献
2.
The morphology of metal nanoparticles supported on oxide substrates plays an important role in heterogeneous catalysis and in the nucleation of thin films. For platinum evaporated onto SrTiO3 (0 0 1) and vacuum annealed we find an unexpected growth formation of Pt nanoparticles that aggregate into clusters without coalescence. This hierarchical nanoparticle morphology with an enhanced surface-to-volume ratio for Pt is analyzed by grazing incidence small-angle X-ray scattering (GISAXS), X-ray fluorescence (XRF), atomic force microscopy (AFM) and high-resolution scanning electron microscopy (SEM). The nanoparticle constituents of the clusters measure 2-4 nm in size and are nearly contiguously spaced where the average edge-to-edge spacing is less than 1 nm. These particles make up the clusters, which are 10-50 nm in diameter and are spaced on the order of 100 nm apart. 相似文献
3.
This paper is focused on nanoporous methylsilsesquioxane deposited using a polymer approach and shows the complementarities of three experimental techniques: ellipsometric porosimetry (EP), X-ray reflectivity (XRR), and grazing incidence small-angle X-ray scattering (GISAXS). XRR and EP confirm that the pore volume fraction is larger for smaller dielectric constants. EP and GISAXS find mean pore sizes independent of the porosity, in the range 3-4 nm as diameter. GISAXS is the only technique that can estimate the porosity isotropy. Finally, the impact of integration processes such as surface plasma treatment, etching or stripping on the porosity is evaluated: the porosity remains unchanged except in the superficial layer where an increase of the pore size (or of the roughness) is observed. 相似文献
4.
文章主要介绍了几种X射线散射技术,包括X射线小角反射技术、X射线漫散射技术、掠入射X射线衍射和多晶薄膜的小角衍射技术。通过具体的事例说明这些X射线散射方法在薄膜研究中的应用。 相似文献
5.
文章主要介绍了几种X射线散射技术,包括X射线小角反射技术、X射线漫散射技术、掠入射X射线衍射和多晶薄膜的小角衍射技术。通过具体的事例说明这些X射线散射方法在薄膜研究中的应用。 相似文献
6.
The transmission of very slow neutrons through a colloidal dispersion of silica particles was investigated at the FRM reactor, Munich. The experimental transmission shows a characteristic wavelength dependence which permits one to deduce several characteristic parameters of the scattering zones, in particular their size and number. The experimental results obtained are consistent with the known data for the substance chosen. This indicates that the simple method of very slow neutron transmission may be applied in certain cases as an alternative to the well-established techniques of X-ray or neutron small-angle scattering.Work supported by the Bundesministerium für Forschung und Technologie 相似文献
7.
The unique structure of a set of self-assembled porous silica materials was
characterized through a combined small-angle scattering (CSAS) method using
small- and ultra-small angle neutron scattering as well as small-angle X-ray
scattering. The porous silica specimens investigated were prepared by a
sol-gel method under the presence of alkylketene dimer (AKD) template
particles and through calcination, which leads to the development of porous
silica having a mass-fractal structure over length scales from ~ 100 nm
to ~ 10 μm. Furthermore, the specimens posses a hierarchical
structure, which consist of a fractal porous structure, and also contain
primary silica particles less than 10 nm in size, which form a continuous
silica matrix. To characterize these complex structures, observation over a
broad range of length scales is indispensable. We propose a CSAS technique
that serves this purpose well. 相似文献
8.
Anionic polyacrylate chains (NaPA) form precipitates if alkaline earth cations are added in stoichiometric amounts. Accordingly,
precipitation thresholds were established for three different alkaline earth cations Ca2+, Sr2+ and Ba2+. Close to the precipitation threshold, the NaPA chains significantly decrease in size. This shrinking process was followed
by means of combined static and dynamic light scattering. Intermediates were generated by varying the ratio [MCl2]/[NaPA] with M denoting the respective alkaline earth cation. All experiments were performed at an inert salt level of 0.01M
NaCl. Similar coil-to-sphere transitions could be observed with all three alkaline earth cations Ca2+, Sr2+ and Ba2+. Based on these findings, supplementary conventional and anomalous small-angle X-ray scattering experiments using selected
intermediates close to the precipitation threshold of SrPA were performed. The distribution of Sr counterions around the polyacrylate
chains in aqueous solution provided the desired scattering contrast. Energy-dependent scattering experiments enabled successful
separation of the pure-resonant terms, which solely stem from the counterions. The Sr2+ scattering roughly reflects the monomer distribution of the polyacrylate chains. Different ratios of the concentrations of
[ SrCl2]/[NaPA] revealed dramatic changes in the scattering curves. The scattering curve at the lowest ratio indicated an almost
coil-like behaviour, while at the higher ratios the scattering curves supported the model of highly contracted polymer chains.
Most of X-ray scattering experiments on intermediate states revealed compact structural elements which were significantly
smaller than the respective overall size of the NaPA particles. 相似文献
9.
Pt-porous glass catalysts have been studied by small-angle X-ray scattering. The catalysts have been prepared by impregnating two micro- or mesoporous glasses with 0.1 wt% of Pt. Two different pore systems of the catalyst supports have been generated and investigated: on the one hand, the mesoporous structure is formed by finely dispersed colloidal silica inside a macroporous glass. On the other hand, micropores are given by the porous glass itself. The pure supports and the supported catalysts have been investigated via chord length analysis for a selected range order, based on the analysis of the scattering intensity for relatively large scattering vectors (up to the upper limit of SAS). The obtained specific structure parameters of both supported catalysts like dispersion, specific metal surface areas, basic arrangement, size distribution and volume fraction of the metal particles basically differ with both pore systems. 相似文献
10.
Dubitskiy I. S. Grigoryeva N. A. Mistonov A. A. Valkovskiy G. A. Sapoletova N. A. Grigoriev S. V. 《Physics of the Solid State》2017,59(12):2464-2475
The structure of surface layers of thin metal inverse opals has been studied first by the grazing-incidence small-angle X-ray scattering technique. Contributions of the form factor and structure factor to the small-angle diffraction pattern have been separated using a numerical model of the scattering process. The complementary use of the small-angle X-ray scattering and grazing-incidence small-angle X-ray scattering techniques has provided independent information about the bulk and surface properties of the samples and allowed a type of defect in the investigated structures to be determined. The measurement results have been verified by atomic force microscopy.
相似文献11.
U. Vainio K. Pirkkalainen K. Kisko G. Goerigk N. E. Kotelnikova R. Serimaa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):93-101
Microcrystalline cellulose is a porous natural material which
can be used both as a support for nanoparticles and as a reducer of metal ions.
Cellulose supported nanoparticles can act as catalysts in many reactions.
Cu, CuO, and Cu2O particles were prepared in microcrystalline cellulose
by adding a solution of copper salt
to the insoluble cellulose matrix and by reducing the copper ions
with several reducers.
The porous nanocomposites were studied using anomalous small angle X-ray
scattering (ASAXS), X-ray absorption spectroscopy, and X-ray diffraction.
Reduction of Cu2+ with cellulose in ammonium hydrate medium
yielded crystalline CuO nanoparticles and
the crystallite size was about 6–20 nm irrespective of
the copper concentration. The size distribution of the CuO particles
was determined with ASAXS measurements and
coincided with the crystallite sizes.
Using sodium borohydrate or hydrazine sulfate as a reducer
both metallic Cu and Cu2O nanoparticles
were obtained and the crystallite size and the oxidation state
depended on the amount of reducer. 相似文献
12.
A. V. Chumakova A. A. Mistonov A. A. Vorobiev A. P. Chumakov N. A. Grigoryeva N. A. Sapoletova K. S. Napolskii A. A. Eliseev S. V. Grigoriev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(6):1234-1239
Formation of artificial opal films by a vertical deposition method was in situ studied using the grazing incidence X-ray diffraction technique. Monodisperse spherical polymethyl methacrylate particles (200 nm in diameter) were deposited on the polished Si substrate from an aqueous suspension. The ordering of particles on a fixed area of the substrate located in turn in the bulk suspension under the meniscus and in the air was continuously monitored by the X-ray scattering upon moving the meniscus down owing to evaporation of the solvent. The triple air-liquid-solid phase boundary, i.e. the top line of the meniscus, is identified as the most probable location of the crystallization process. The analysis of observed Bragg reflections and the particle form-factor indicates that the obtained artificial opal-like structures are composed of the spheres arranged in a close-packed hexagonal layers parallel to the substrate. The characteristic correlation length along the normal to the substrate of 550 ± 100 nm is obtained from the half full width of Bragg peaks. 相似文献
13.
V. V. Egorov A. A. Shaldzhyan A. N. Gorshkov Ya. A. Zabrodskaya D. V. Lebedev A. I. Kuklin O. I. Ksenofontova A. V. Shvetsov A. V. Vasin L. M. Tsybalova V. V. Isaev-Ivanov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2016,10(2):322-325
The structure of ribonucleic particles of influenza A virus of the A/California/07/09pdm strain is investigated by transmission electron microscopy and small-angle X-ray scattering. The small-angle X-ray scattering data obtained at room temperature correspond to previously reported data of ribonucleic particles of this virus. At higher temperatures, noticeable changes in the morphology of ribonucleic complexes are observed. 相似文献
14.
J.R. CasanovaE.A. Heredia C.D. BojorgeH.R. Cánepa G. KellermannA.F. Craievich 《Applied Surface Science》2011,257(23):10045-10051
Nanocrystalline ZnO thin films prepared by the sol-gel dip-coating technique were characterized by grazing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), X-ray reflectivity (XR) and grazing incidence small-angle X-ray scattering (GISAXS). The structures of several thin films subjected to (i) isochronous annealing at 350, 450 and 550 °C, and (ii) isothermal annealing at 450 °C during different time periods, were characterized. The studied thin films are composed of ZnO nanocrystals as revealed by analysing several GIXD patterns, from which their average sizes were determined. Thin film thickness and roughness were determined from quantitative analyses of AFM images and XR patterns. The analysis of XR patterns also yielded the average density of the studied films. Our GISAXS study indicates that the studied ZnO thin films contain nanopores with an ellipsoidal shape, and flattened along the direction normal to the substrate surface. The thin film annealed at the highest temperature, T = 550 °C, exhibits higher density and lower thickness and nanoporosity volume fraction, than those annealed at 350 and 450 °C. These results indicate that thermal annealing at the highest temperature (550 °C) induces a noticeable compaction effect on the structure of the studied thin films. 相似文献
15.
V.D. Sitdikov R.K. Islamgaliev M.A. Nikitina G.F. Sitdikova K. X. Wei I.V. Alexandrov 《哲学杂志》2019,99(1):73-91
In the present work, new possibilities of the X-ray diffraction for investigations of the phase composition, size, shape and volume fraction of particles in ultrafine-grained ferritic/martensitic steel and the Cu-Cr-Zr alloy have been demonstrated. For the first time, the method of X-ray diffraction in the transmission mode was used to identify particles with a volume fraction of less than one percent in the ultrafine-grained materials studied. The small-angle X-ray scattering method was used to estimate the size and shape of dispersed particles. Specific features of the ultrafine-grained structure determined by the X-ray diffraction and transmission electron microscopy studies were used for estimation of dispersion hardening in the samples obtained by equal-channel angular pressing in comparison with the samples subjected to standard treatment. 相似文献
16.
In-situ study of precipitates in Al–Zn–Mg–Cu alloys using anomalous small-angle x-ray scattering
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In the present work,the precipitate compositions and precipitate amounts of these elements(including the size distribution,volume fraction,and inter-precipitate distance) on the Cu-containing 7000 series aluminum alloys(7150 and 7085 Al alloys),are investigated by anomalous small-angle x-ray scattering(ASAXS) at various energies.The scattering intensity of 7150 alloy with T6 aging treatment decreases as the incident x-ray energy approaches the Zn absorption edge from the lower energy side,while scattering intensity does not show a noticeable energy dependence near the Cu absorption edge.Similar results are observed in the 7085 alloy in an aging process(120℃) by employing in-situ ASAXS measurements,indicating that the precipitate compositions should include Zn element and should not be strongly related to Cu element at the early stage after 10 min.In the aging process,the precipitate particles with an initial average size of ~ 8 ?A increase with aging time at an energy of 9.60 ke V,while the increase with a slower rate is observed at an energy of 9.65 ke V as near the Zn absorption edge. 相似文献
17.
N. N. Novikova M. V. Kovalchuk S. N. Yakunin N. D. Stepina A. V. Rogachev E. A. Yurieva I. V. Marchenko T. V. Bukreeva N. N. Kolobylina A. L. Vasiliev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2017,11(4):685-693
X-ray studies of dipalmitoylphosphatidylcholine (DPPC) single layers on the surface of a liquid provide detailed information on the interaction of metal particles with a single layer upon an increase in the surface pressure up to the collapse. Two complementary X-ray methods are used: grazing incidence diffraction and the X-ray standing waves method. The experimental results obtained for a single layer formed on a colloidal solution of magnetite nanoparticles reveal that the increase in the surface pressure is accompanied by an increase in the concentration of nanoparticles near the surface. In a series of experiments where metal particles of submicron size are sputtered onto a DPPC single layer, a sharp decrease in the intensity of the fluorescence yield from metal atoms is observed while the single layer is compressed. These data suggest that metal particles deposited onto the surface of a single layer were extruded into the aqueous subphase. 相似文献
18.
Guilleaume B Blaul J Ballauff M Wittemann M Rehahn M Goerigk G 《The European physical journal. E, Soft matter》2002,8(3):299-309
An investigation of the radial distribution of the counterions of a synthetic rodlike polyelectrolyte in aqueous solution
is presented. The cationic polyelectrolyte used here has a poly(p-phenylene) backbone. For typical molecular weights the macroion
comprises approximately one persistence length (ca. 20 nm) and effects of finite stiffness may be disregarded. Each repeating unit bears four charges which leads to a charge
parameter of ξ = 6.65. The distribution of the iodide counterions around this highly charged macroion is studied by small-angle
X-ray scattering (SAXS) in dilute aqueous solution. These investigations are supplemented by measurements using anomalous
small-angle X-ray scattering (ASAXS) that furnishes additional information about the contrast of the macroion. Data taken
at high scattering angles give indication for contributions caused by the longitudinal fluctuations of the counterions. After
correction for this effect the experimental results are compared to intensities calculated by use of the Poisson-Boltzmann
(PB)-cell model. It is found that the PB-cell model describes the corrected data at intermediate and high scattering angles.
Deviations at low scattering angle are attributed to the mutual interaction of the rod-like polyelectrolyte that can be described
in terms of an effective structure factor. Data taken at lowest scattering angles point to a weak attraction between the rod-like
macroions.
Received: 27 July 2001 and Received in final form 27 March 2002 相似文献
19.
Thin films of silicon oxynitride have largely replaced pure silicon oxide films as gate and tunnel oxide films in modern technology due to their superior properties in terms of efficiency as boron barrier, resistance to electrical stress and high dielectric strength. A single chamber system for plasma enhanced chemical vapor deposition was employed to deposit different films of SiOxNyHz with 0.85 < x < 1.91. All films were previously characterized by Rutherford back-scattering and infrared spectroscopy to determine the stoichiometry and the presence of various bonding configurations of constituent atoms. We used X-ray reflectivity to determine the electron density profile across the depth, and we showed that the top layer is densified. Moreover, grazing incidence small-angle X-ray scattering was used to study inhomogeneities (clustering) in the films, and it is shown that plate-like inhomogeneities exist in the top and sphere-like particles at the bottom part of the film. Their shape and size depend on the stoichiometry of the films. 相似文献
20.
《Journal of magnetism and magnetic materials》2005,294(2):152-158
The most important methods for determining the grain size, the grain size distribution and also the actual microstructure of nanocrystalline materials are: X-ray diffraction line profile analysis, transmission electron microscopy, and small-angle neutron scattering. For each of these three methods their specific advantages and disadvantages are discussed and an experimental example is given. 相似文献