Search results for "small-angle"
showing 10 items of 258 documents
Investigation of heavy ion produced defect structures in insulators by small angle scattering
1985
Fast heavy ions produce stable defects in most dielectrica. As examples mica, Polyethylenterephtalat and Polystyrol were irradiated with Ar, Ni, Kr, Xe and U ions in an energy range from 0.5 up to 20 MeV/u. The resulting defects were investigated by neutron and x-ray small-angle scattering. The ion beam supplied by the UNILAC accelerator at GSI Darmstadt is characterized by its small emittance, the well defined mass, charge and energy of the ions and their stochastical distribution in the phase space. In scattering experiments the system of scattering centers created by these ions causes a scattered intensity distribution which strongly depends on the orientation of the sample with respect …
Analysis of small-angle scattering patterns from a commercial Al-Li alloy by means of a model incorporating a repulsive step potential
1992
Abstract Small-angle X-ray scattering measurements are reported for a commercial Al-8·49%Li-51% Cu (atomic composition) alloy solution treated at 520°C and thermally aged for several times at several temperatures. Data have been analysed by means of a model of ellipsoidal precipitate particles previously proposed by some of us and by a modification of this model where, in the interparticle interference term, allowance is made for interactions between the precipitate particles at longer range than previously. This was achieved by the introduction, in addition to the hard-sphere interaction potential, of a potential step. Our fits indicate that the precipitate particles interact through a rep…
Inelastic neutron scattering measurements on Nd2Fe14B and Y2Fe14B single crystals
1992
Abstract Inelastic neutron scattering measurements have been carried out on Nd 2 Fe 14 B and Y 2 Fe 14 B single crystals. Temperature dependent acoustic magnon dispersion curves have been found along the high-symmetry directions [0,0,1] and [1,0,0] with a gap at (0,0,2). Soft mode behaviour at spin wave vector q = 0 was observed for Nd 2 Fe 14 B near the spin reorientation temperature. The inelastic scattering intensity decreases steeply for larger q . Therefore, the dispersion curves could be measured until the middle of the Brillouin zone only. The experimental results are discussed in the frame of a classical spin wave model.
Competition between heterogeneous and homogeneous nucleation near a flat wall
2009
We studied the competition between heterogeneous and homogeneous nucleation of an aqueous suspension of charged colloidal spheres close to the container walls. Samples of equilibrium crystalline structure were shear-melted and the metastable melt left to solidify after the cessation of shear. The crystallization kinetics was monitored using time-resolved scattering techniques: at low particle number densities n we applied an improved static light scattering method while at large particle concentrations ultra-small-angle x-ray scattering was applied for the first time. Our results show some unexpected behavior: the heterogeneous nucleation at the container walls is delayed in comparison to t…
Particle Characterization Using Multiple Scattering Decorrelation Methods. Part 1: Standard Latex Particles
1999
Kinetics of particle growth and particle composition of a commercial Al-Li alloy by means of small-angle scattering
1991
Abstract Extending previous work done on a similar alloy, small-angle X-ray scattering measurements are reported for a commercial Al-Cu-Li alloy (2–68% Cu and 1–88% Li by weight). Data have been analysed by means of an ellipsoidal model of precipitate particles using a method previously proposed by some of us which, incorporating interparticle interference effects, reproduces the fuli scattering intensities of the samples studied. Particie dimensions obtained from the fit indicate that the Lifshitz-Slyozov coarsening mechanism holds for ageing at higher temperatures and longer times. The activation energy for volume diffusivity obtained is similar to that of pure binary alloys. The scatteri…
Interaction of Gold with Co-Condensed and Grafted HMS-SH Silica: A 29Si {1H} CP-MAS NMR Spectroscopy, XRD, XPS and Au LIII EXAFS Study
2010
Hexagonal mesoporous silica (HMS) is functionalised with mercaptopropyl groups by adopting two different procedures ; co-condensation and grafting. In both cases tetraethylorthosilicate (TEOS) and 3-mercaptopropyltriethoxysilane (3-MPTES) are used as the silicon and sulfur precursors, respectively. The obtained materials are analysed by several techniques such as N 2 sorption, TG-DTA, XRD, SAXS and-solid state 29 Si { 1 H} CP-MAS NMR spectroscopy. By taking advantage of the chemical interaction between gold and the -SH groups, the effect of the thiol addition procedure on the supporting capability of the functionalised silica is evaluated by depositing gold through the incipient wet impregn…
Supramolecular polymerization of electronically complementary linear motifs: anti-cooperativity by attenuated growth†
2021
Anti-cooperative supramolecular polymerization by attenuated growth exhibited by self-assembling units of two electron-donor benzo[1,2-b:4,5-b′]dithiophene (BDT) derivatives (compounds 1a and 1b) and the electron-acceptor 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) (compound 2) is reported. Despite the apparent cooperative mechanism of 1 and 2, AFM imaging and SAXS measurements reveal the formation of small aggregates that suggest the operation of an anti-cooperative mechanism strongly conditioned by an attenuated growth. In this mechanism, the formation of the nuclei is favoured over the subsequent addition of monomeric units to the aggregate, which finally results in short aggrega…
Synthesis of Fluorinated Bent-Core Mesogens (BCMs) Containing the 1,2,4-Oxadiazole Ring
2015
New fluorinated bent-core mesogens containing the 1,2,4-oxadiazole or 1,2,4-triazole nucleus have been synthesized taking advantage of the ANRORC (Addition of Nucleophile, Ring-Opening, Ring-Closure) reactivity of 5-perfluoroalkyl-1,2,4-oxadiazoles. Physical state changes of the obtained compounds were characterized through DSC, POM, and SAXS. Besides the formation of a smectic mesophase, a novel behavior as organic molecular glass was evidenced for some 1,2,4-oxadiazole derivatives.
SAXS Study on Myoglobin Embedded in Amorphous Saccharide Matrices
2011
We report on Small Angle X-ray Scattering (SAXS) measurements performed on samples of carboxy-myoglobin and met-myoglobin embedded in low hydrated matrices of four different saccharides (trehalose, sucrose, maltose and lactose). Results confirm the already reported occurrence of inhomogeneities, which are not peculiar of trehalose samples, but appear also in maltose and lactose, and in some cases also sucrose, being dependent on the sample hydration and on the presence of sodium dithionite. This behaviour confirms our previous interpretation about the nature of the inhomogeneities, and prompt it as a possible general behaviour for highly concentrated sugar matrices.