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P. Strunz D. Mukherji G. Pigozzi R. Gilles T. Geue K. Pranzas 《Applied Physics A: Materials Science & Processing》2007,88(2):277-284
The Ni3Si-type nanoparticles dispersed in a mixture of H2O/D2O were characterised by SANS using the contrast variation method. The existence of a core-shell structure in the nanoparticles
with a Ni3Si(Al) core and amorphous SiOx shell is confirmed by the SANS measurements. The nanoparticles were produced by extracting precipitates from a bulk Ni-13.3Si-2Al
( at. %) alloy using electrochemical phase separation technique and were pre-characterised by X-ray diffraction and transmission
electron microscopy. By comparing the precipitate morphology in the Ni-Si-Al alloy with the extracted nanoparticles in the
SANS measurements, it is clearly established that the precipitates shape and size are unaffected by the extraction process
and that the amorphous shell forms on top of the particle core. However, the present measurement could not confirm or exclude
the presence of H atoms in the shell structure.
PACS 61.12.Ex; 61.12.-q; 61.46.Df; 61.82.Rx 相似文献
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Bygott AM Geue RJ Ralph SF Sargeson AM Willis AC 《Dalton transactions (Cambridge, England : 2003)》2007,(42):4778-4787
The synthesis and characterisation of complexes of the hexaamine cage ligand facial-1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane (fac-(Me)(5)-D(3 h)tricosaneN(6)) with Zn(II), Cd(II) and Hg(II) is reported. Single crystal X-ray structural analyses of the Cd(II) and Hg(II) complexes reveal that the coordination spheres of both cations have an unusual trigonal prismatic stereochemistry organised by the ligand substituents and cavity size. This is unprecedented for hexaamine complexes of these metal ions, and in stark contrast to the distorted octahedral stereochemistry found previously for the analogous Zn(II) complex. An X-ray structural analysis of single crystals of the diprotonated ligand [fac-(Me)(5)-D(3h)tricosaneN(6) - 2H](CF(3)SO(3))(2) shows that it also prefers to adopt a trigonal prismatic structure. The (13)C NMR spectra of the metal complexes indicate that their structures are preserved at 20 degrees C in solution. However, heating the Zn(II) complex to approximately 130 degrees C appears to convert it to the trigonal prismatic form. In contrast cooling the trigonal prismatic Hg(II) complex to -80 degrees C does not convert it to the octahedral structure. The results are also compared to the structures of various other transition metal ion complexes of the same or similar ligands. This comparison yields overall an appreciation of the factors that determine the final structures of complexes formed with such tricosaneN(6) ligands. 相似文献
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The sinusoidal shape of light‐induced surface relief gratings of polymers can be probed by x‐ray scattering techniques. A particular approach of kinematic x‐ray scattering theory is developed to interpret experimental scattering curves. The simulations demonstrate the particular sensitivity of x‐ray reflectivity for very small grating amplitudes. At angles of incidence close to the critical angle of total external reflection a grating amplitude h < 2 nm already provides measurable grating peaks. In general the grating amplitude h can be measured from the envelope function over the grating peak maxima. The capability of the approach is demonstrated by simulation of the reflection curve recorded from a polymer sample with non uniform grating height. 相似文献
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Feuz L Strunz P Geue T Textor M Borisov O 《The European physical journal. E, Soft matter》2007,23(3):237-245
Small-angle neutron scattering (SANS) has been employed for the analysis of conformations of poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g -PEG) molecular bottle brushes in aqueous solutions. The degree of polymerisation of the PEG chains was systematically varied
in order to unravel dependence of the conformational properties of the bottle brushes on the molecular weight of the grafted
chains. The grafting density was kept constant and high enough to ensure strong overlap of the PEG chains. The scattering
spectra were fitted on the basis of the model of an effective worm-like chain with the account of average radial distribution
and local fluctuations of the PEG density in the bottle brush. The results of the fits indicate that molecular brushes retain
weakly bent configuration on the length scale of the order of (or larger than) the brush thickness. This finding is in agreement
with earlier simulation and recent theoretical results. 相似文献
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Bernhardt PV Bramley R Geue RJ Ralph SF Sargeson AM 《Dalton transactions (Cambridge, England : 2003)》2007,(12):1244-1249
The crystal structure of the bicyclic hexaamine complex [Cu(fac-Me5-tricosane-N6)](ClO4)2.H2O (fac-Me5-tricosane-N6 = facial-1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane) at 100 K defines an apparently tetragonally compressed octahedral geometry, which is attributed to a combination of dynamic interconversion and static disorder between two tetragonally elongated structures sharing a common short axis. This structure is fluxional at 60 K and above as shown by EPR spectroscopy. Aqueous cyclic voltammetry reveals that a remarkably stable Cu(I) form of the complex is stabilised by the encapsulating nature of the expanded cage ligand. 相似文献
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Laver M Forgan EM Abrahamsen AB Bowell C Geue T Cubitt R 《Physical review letters》2008,100(10):107001
We describe the use of reverse Monte Carlo refinement to extract structural information from angle-resolved data of a Bragg peak. Starting with small-angle neutron scattering data, the positional order of an ensemble of flux lines in superconducting Nb is revealed. We discuss the uncovered correlation functions in the light of topical theories, in particular, the "Bragg glass" paradigm. 相似文献
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