Search results for "Small-angle scattering"

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…

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…

Dilute and semi dilute solutions of block copolymers in water, near-critical and super-critical CO2: a small angle scattering study of the monomer–ag…

2002

Abstract Small angle neutron (SANS) and X-ray (SAXS) Scattering measurements on aggregate formation of block copolymers in water and in near-critical and supercritical CO2 are reported here. Time Resolved SAXS (TR-SAXS) has also been performed in the supercritical region. Experiments have been carried out for a series of different thermodynamic conditions, changing the solvent density by profiling the pressure at constant temperature. A sharp transition between monomers dissolved as random coils and micelles characterized by a solvo-philic shell and a solvo-phobic core occurs when the solvent density reaches the critical micellization value. This is easily shown in the case of scCO2.

Application of small angle neutron scattering to micellar fluids

1990

Abstract In this paper we present a short overview of the application of small angle neutron scattering (SANS) to micellar fluids. In the first part of the paper a general expression of the scattering equation is derived, with particular emphasis on the approximations involved and on their practical consequences. In the second part of the paper we present six selected test cases (such as mono- and polydisperse fluids, critical fluids, shapes other than spherical, etc.) taken from our own work, to demonstrate the kind of analysis performed in each case to extract the information from SANS data.

Study on the initial stages of water corrosion of fluorozirconate glasses

2004

Abstract The surface corrosion process associated with the hydrolysis of fluorozirconate glass, ZBLAN (53ZrF 4 , 20BaF 2 , 20NaF, 4LaF 2 , 3AlF 3 ) was investigated using X-ray photoelectron spectroscopy (XPS), grazing-incidence small angle X-ray scattering (GISAXS), X-ray reflectivity (XRR) and scanning electron microscopy (SEM). After a short exposure period (25 min) of the glass surface to deionized water the XPS data indicate an increase of the oxygen content accompanied by a decrease of fluorine concentration. The analysis of the chemical bonding structure identified the predominant surface reaction products as zirconium hydroxyfluoride and oxyfluoride species. The second most abundant…

Thermodiffusion anisotropy under a magnetic field in ionic liquid-based ferrofluids

2021

International audience; Ferrofluids based on maghemite nanoparticles (NPs), typically 10 nm in diameter, are dispersed in an ionic liquid (1-ethyl 3-methylimidazolium bistriflimide - EMIM-TFSI). The average interparticle interaction is found to be repulsive by small angle scattering of X-rays and of neutrons, with a second virial coefficient A2 = 7.3. A moderately concentrated sample at Φ = 5.95 vol% is probed by forced Rayleigh scattering under an applied magnetic field (up to H = 100 kA m-1) from room temperature up to T = 460 K. Irrespective of the values of H and T, the NPs in this study are always found to migrate towards the cold region. The in-field anisotropy of the mass diffusion c…

Small-Angle Scattering Techniques for Analyzing Conformational Transitions in Hemocyanins

2004

Publisher Summary The precise delivery of oxygen from respiratory surfaces to the tissues is mediated by cooperative and allosterically regulated carrier proteins, such as hemoglobin or hemocyanin. To establish cooperativity, these proteins must be able to adopt different conformations. These conformations are characterized by different ligand affinities, which have their basis in different structures as is the case for the deoxy and oxy states of human hemoglobin. To understand the cooperative interaction of these molecules at the molecular level, the structures of these conformations must be resolved and the transitions between them must be monitored. Because of the nature of sample prepa…