Search results for "Neutron diffraction"

Determination of Molecular Crystal Structures from X-Ray Powder Diffraction Data

1993

Diffraction anomale et composition cationique d'une titanomagnétite nanométrique

2000

Les ferrites substitues au titane constituent des materiaux interessants pour aller vers la comprehension des reactions d'oxydo-reduction qui ont lieu dans ces composes de structure spinelle. Ces composes synthetises par chimie douce on ete etudies in-situ par diffraction anomale dans diverses conditions. Dans le cas particulier du compose Fe 2.5 Ti 0.5 O 4 , les premiers resultats montrent que cette methode de synthese ne permet pas d'elaborer directement le ferrite avec la composition esperee. En effet l'analyse structurale met en evidence un taux de titane bien inferieur a 0.5 alors que d'autres techniques,(analyse ICP, methode de Poix), confirment ce taux de substitution.

Preparation and characterization of Pd2Sn nanoparticles

2007

We report a non-aqueous solution preparation of Pd{sub 2}Sn nanoparticles with sizes near 20 nm. The intermetallic compound with the Co{sub 2}Si structure has been characterized using transmission electron microscopy, Rietveld refinement of synchrotron X-ray and neutron powder diffraction, and real-space pair distribution function analysis of high-energy synchrotron X-ray scattering. We also present a description of the electronic structure of this covalent intermetallic using density functional calculations of the electronic structure.

Lattice-Site-Specific Spin Dynamics in Double PerovskiteSr2CoOsO6

2014

Magnetic properties and spin dynamics have been studied for the structurally ordered double perovskite Sr2CoOsO6. Neutron diffraction, muon-spin relaxation, and ac-susceptibility measurements reveal two antiferromagnetic (AFM) phases on cooling from room temperature down to 2 K. In the first AFM phase, with transition temperature TN1=108  K, cobalt (3d7, S=3/2) and osmium (5d2, S=1) moments fluctuate dynamically, while their average effective moments undergo long-range order. In the second AFM phase below TN2=67  K, cobalt moments first become frozen and induce a noncollinear spin-canted AFM state, while dynamically fluctuating osmium moments are later frozen into a randomly canted state at…

Small angle neutron scattering on periodically deformed polymers

1984

Small angle neutron scattering from periodically deformed samples is a useful extension of the methods presently available for the study of molecular dynamics of polymers. In this paper we describe apparatus that has been used to produce large cyclic deformations at frequencies upto 10 Hz and the principles by which data is collected to give spectra corresponding to different states of strain of the sample. Some data on model polydimethylsiloxane networks is given as an illustration of the value of this technique.

Anomalous water dynamics in brain: a combined diffusion magnetic resonance imaging and neutron scattering investigation

2019

International audience; Water diffusion is an optimal tool for investigating the architecture of brain tissue on which modern medical diagnostic imaging techniques rely. However, intrinsic tissue heterogeneity causes systematic deviations from pure free-water diffusion behaviour. To date, numerous theoretical and empirical approaches have been proposed to explain the non-Gaussian profile of this process. The aim of this work is to shed light on the physics piloting water diffusion in brain tissue at the micrometre-to-atomic scale. Combined diffusion magnetic resonance imaging and first pioneering neutron scattering experiments on bovine brain tissue have been performed in order to probe dif…

Microstructure and phase composition of bronze Montefortino helmets discovered Mediterranean seabed to explain an unusual corrosion

2021

AbstractTwo Monterfortino helmets, recovered in the Mediterranean seabed, show unusual features with respect to the more common helmets of the same period and found in underwater environments. Hence, they were investigated by a multi-analytical approach, which allowed us to identify the compounds constituting the helmets and to make some considerations about their metallurgy, although all the metal was converted to degradation products. The helmets, originally made in bronze, have maintained their original shape because of copper sulphides formation. The observed differences in composition between the two helmets were attributed to the position modification, of one of them, into the seabed …

Channel Formation and Intermediate Range Order in Sodium Silicate Melts and Glasses

2004

We use inelastic neutron scattering and molecular dynamics simulation to investigate the interplay between the structure and the fast sodium ion diffusion in various sodium silicates. With increasing temperature and decreasing density the structure factors exhibit an emerging prepeak around 0.9 A^-1. We show, that this prepeak has its origin in the formation of sodium rich channels in the static structure. The channels serve as preferential ion conducting pathways in the relative immobile Si-O matrix. On cooling below the glass transition this intermediate range order is frozen in.

The Low Barrier Hydrogen Bond in the Photoactive Yellow Protein: A Vacuum Artifact Absent in the Crystal and Solution

2016

Journal of the American Chemical Society 138(51), 16620 - 16631 (2016). doi:10.1021/jacs.6b05609

Investigation of composition of archeological Helmets, type Montefortino

2019

In this work, a preliminary non invasive and non destructive investigation, performed on two helmets, is presented.