Search results for "Diffraction"
showing 10 items of 1584 documents
Interface charge density matching as driving force for new mesostructured oxovanadium phosphates with hexagonal structure, [CTA]xVOPO4·zH2O
1999
Hexagonal mesostructured mixed-valence oxovanadium phosphates [CTA]xVOPO4·zH2O, in short ICMUV-2, have been synthesized through a S+I- cooperative mechanism using cationic surfactant (cetyltrimethylammonium, CTAB) rodlike micelles as a template. On the lines of the hypothesis that the driving force leading to the formation of mesostructured solids is the charge density matching at the interface between the supramolecular−organic and supramolecular−inorganic moieties, the self-assembling process between CTA+ micelles and VOPO4q- planar anions can be thought of as consequence of the adequate adjustment of the metal mean oxidation state. X-ray powder diffraction and TEM techniques show that th…
Four-, five- and six-coordinated Zn-II complexes of OH-containing ligands: Syntheses, structure and reactivity
2002
Four-, five- and six-coordinated complexes of Zn-II with OH-rich molecules possessing an ONO binding core were synthesized, characterized and their structures were established by single-crystal X-ray diffraction, The corresponding metal ion geometries were found to be distorted tetrahedral, square pyramidal and octahedral, respectively. The complexes exhibit interesting lattice structures such as layered and corrugated sheets owing to the presence of a number of weak intermolecular interactions. The five-coordinated, water-bound Zn-II complex was studied because of its putative hydrolysis property towards p-nitrophenyl acetate. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Impact of the use of sterically congested Ir(III) complexes on the performance of light-emitting electrochemical cells
2018
International audience; The synthesis, structural and optoelectronic characterization of a family of sterically congested cyclometalated cationic Ir(iii) complexes of the form [Ir(C^N)2(dtBubpy)]PF6 (with dtBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine and C^N = a cyclometalating ligand decorated at the 4-position of the pyridine ring and/or the 3-position of the phenyl ring with a range of sterically bulky substituents) are reported. This family of complexes is compared to the unsubstituted analogue complex R1 bearing 2-phenylpyridinato as cyclometalating ligand. The impact of sterically bulky substituents on the C^N ligands on both the solid state photophysics and light-emitting electrochemi…
Large Fibres in Urinary Calculi—-Promoters of Stone Formation
1988
Large fibres (phi 10-20 microns, length up to 5,000 microns) are sometimes imbedded in urinary calculi. It may be that these fibres can catch sediment particles and promote stone growth. By scanning electron microscopy the morphology of the fibres was studied as well as the relationship of the fibres with crystalline stone components. The reported findings suggest that the fibres are possibly formed in the tubuli as the result of an hitherto unknown defect.
X-ray diffraction of a protein crystal anchored at the air/water interface
1995
We report the first successful in situ x-ray diffraction experiment with a 2D protein array at the lipid/water interface and demonstrate that the order can be controlled via lateral pressure or density. A protein (streptavidin) was bound to a monolayer of biotinylated lipid at the air/water interface, and diffraction of the protein layer could be measured to many orders. Compression of the monolayer changed the diffraction pattern drastically, indicating that the protein structure can be strongly influenced by external parameters like lateral pressure or density. From the width of the peaks, we find that aggregates consisting of as few as 100 monomers contribute to the diffraction. This ind…
Microstructural, chemical and textural records during growth of snowball garnet
2009
The growth history of two populations of snowball garnet from the Lukmanier Pass area (central Swiss Alps) was examined through a detailed analysis of three-dimensional geometry, chemical zoning and crystallographic orientation. The first population, collected in the hinge of a chevron-type fold, shows an apparent rotation of 360 degrees. The first 270 degrees are characterized by spiral-shaped inclusion trails, gradual and concentric Mn zoning and a single crystallographic orientation, whereas in the last 90 degrees, crenulated inclusion trails and secondary Mn maxima centred on distinct crystallographic garnet domains are observed. Microstructural, geochemical and textural data indicate a…
An X-ray powder diffraction study of lanthanum–strontium ferromanganites
2001
Abstract Various lanthanum–strontium ferromanganites (La 1− x Sr x )(Mn 1− y Fe y )O 3± δ (LSMF) with x =0.2, 0.5 and 0.7 and y =0.2, 0.5 and 0.8 were prepared by a glycine–nitrate combustion route and conditioned into two different oxygenation states which are likely to be encountered in cathode materials for solid oxide fuel cells (SOFC). Crystal symmetries for both the low and the fully oxygenated states were determined by X-ray diffractometry. Most perovskite compositions crystallized in either cubic or rhombohedral symmetry with the exception of La 0.5 Sr 0.5 Mn 0.2 Fe 0.8 O 3± δ , where a transition from rhombohedral to cubic occurred in going from the full to the low oxygenation stat…
Automated electron diffraction tomography – development and applications
2019
Electron diffraction tomography, a potential method for structure analysis of nanocrystals, and, in more detail, the strategies to use automated diffraction tomography (ADT) technique are described. Examples of ADT application are discussed according to the material class.
Stylolite interfaces and surrounding matrix material: Nature and role of heterogeneities in roughness and microstructural development
2010
Rough pressure solution interfaces, like stylolites, are one of the most evident features of localized slow deformation in rocks of the upper crust. There is a general consensus that the development of these rough structures is a result of localized, stress enhanced, dissolution of material along a fluid filled interface, but little is known on the initiation of this roughness. The aim of this article is to reveal the role of heterogeneities initially present in the host-rock on roughness initiation. This should give insights on whether stylolite roughness is generated by a stress-induced instability or by the presence of disorder in the material (i.e. quenched noise). We use a microstructu…
Melting behaviour of d-sucrose, d-glucose and d-fructose
2004
The melting behaviour of d-sucrose, d-glucose and d-fructose was studied. The melting peaks were determined with DSC and the start of decomposition was studied with TG at different rates of heating. In addition, melting points were determined with a melting point apparatus. The samples were identified as d-sucrose, alpha-d-glucopyranose and beta-d-fructopyranose by powder diffraction measurements. There were differences in melting between the different samples of the same sugar and the rate of heating had a remarkable effect on the melting behaviour. For example, T(o), DeltaH(f) and T(i) (initial temperature of decomposition) at a 1 degrees Cmin(-1) rate of heating were 184.5 degrees C, 126…