Diffusion de neutrons aux petits angles appliquée aux études d'interfaces et de systèmes confinés

Auvray, L.; Brûlet, Annie

doi:10.1051/sfn:20070014

Cited by 3 publications

(3 citation statements)

References 31 publications

(44 reference statements)

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“…The demonstration of the Porod law can be found in ref. (18). The Porod law is valid whatever the geometry for any kind of a two-phase system.…”

Section: Porod Regime/scattering Invariantmentioning

confidence: 98%

“…This situation appears when one aims at characterizing a mixture of two species in a continuous phase, or at characterizing a complex object made of two distinct parts with different SLD in a continuous phase, as for example a colloidal suspension made of inorganic nanoparticles grafted by polymeric chains for which is it interesting to probe separately the inorganic core and the polymeric corona (29) (30) † † . In such ternary system, the general equation of scattering (18) writes:…”

Section: Contrast Variation In Ternary Systemmentioning

confidence: 99%

“…Let us write the whole scattered intensity (Eqs. (18) and (25)) by separating the form factor and the structure factor:…”

Section: Separating Form Factor and Structure Factor For A System Objmentioning

confidence: 99%

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Small-Angle Neutron Scattering

Dasannacharya¹,

Goyal

2016

Encyclopedia of Nanotechnology

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Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ∼ 1 nm up to ∼ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ∼ 1 cm 3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area.. .) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2 nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer configurations, optimization of sample characteristics prior to measurements (thickness, volume, hydrogen content.. .), standards measurements to be made and principle of data reduction. Résumé. (La Diffusion de Neutrons aux petits angles (DNPA) est une technique permettant de sonder la structure 3-D de matériaux sur une gamme typique de taille comprise entre ∼1 nm) et ∼ quelques 100 nm, les informations obtenues étant statistiquement moyennées sur la taille de l'échantillon dont le volume est d'environ 1 cm 3. C'est une technique très puissante car elle permet de faire une caractérisation complète de la structure d'un objet donné de dimensions nanométriques (rayon de giration, forme, volume, masse, dimension fractale, surface spécifique.. .) grâce à la détermination du facteur de forme, ainsi que la détermination de la manière dont les objets sont organisés au sein d'un milieu continu, et donc de décrire les interactions entre les objets, par la détermination du facteur de structure. Les propriétés spécifiques de neutrons (possibilité de moduler le contraste pa...

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“…The demonstration of the Porod law can be found in ref. (18). The Porod law is valid whatever the geometry for any kind of a two-phase system.…”

Section: Porod Regime/scattering Invariantmentioning

confidence: 98%

Section: Contrast Variation In Ternary Systemmentioning

confidence: 99%

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Small-Angle Neutron Scattering

Dasannacharya¹,

Goyal

2016

Encyclopedia of Nanotechnology

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Small angle neutron scattering

Cousin

2015

EPJ Web of Conferences

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Abstract. Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ∼ 1 nm up to ∼ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ∼ 1 cm 3 . This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area. . . ) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2 nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer configurations, optimization of sample characteristics prior to measurements (thickness, volume, hydrogen content. . . ), standards measurements to be made and principle of data reduction.Résumé. (La Diffusion de Neutrons aux petits angles (DNPA) est une technique permettant de sonder la structure 3-D de matériaux sur une gamme typique de taille comprise entre ∼1 nm) et ∼ quelques 100 nm, les informations obtenues étant statistiquement moyennées sur la taille de l'échantillon dont le volume est d'environ 1 cm 3 . C'est une technique très puissante car elle permet de faire une caractérisation complète de la structure d'un objet donné de dimensions nanométriques (rayon de giration, forme, volume, masse, dimension fractale, surface spécifique. . . ) grâce à la détermination du facteur de forme, ainsi que la détermination de la manière dont les objets sont organisés au sein d'un milieu continu, et donc de décrire les interactions entre les objets, par la détermination du facteur de structure. Les propriétés spécifiques de neutrons (possibilité de modul...

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New Insights on the Characterization of Polymer Adsorbed Layers in Porous Media

Boujlel

Barré

Rousseau

2018

Day 3 Wed, March 28, 2018

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The objective of this work was to bring new insights on Polymer Adsorbed Layers (PAL) in porous media. Irreversible permeability reductions and irreversible polymer retention were firstly determined versus polymer molecular weight, flow velocity and brine salinity and hardness. The presence of PAL was then evidenced by small angle neutrons scattering (SANS). This allowed proposing interpretations of permeability reduction in terms of PAL thickness and density. This study focused on the adsorption of partially hydrolyzed polyacrylamide (HPAM) polymers on granular packs of silicon carbide (SiC). Polymer solutions were injected at fixed flow rate and concentration. Irreversible permeability reductions (Rk) were determined from changes in pressure drops and irreversible polymer retention (Г) from the difference of volume at breakthrough for two successive slugs. In-situ SANS experiments were performed under flow using the contrast matching technique: the pore space was filled with an H2O/D2O mixture with a scattering length density equal to that of the SiC. This resulted in a two-phase system whose scattering intensity was directly connected to the PAL (meso)structure. Results showed an increase of Rk and of Г with salinity (0.2 to 80 g/L, with a stabilization trend towards high salinities) and molecular weight. When hardness was increased, Rk was not much affected but Г increased. The SANS experiments revealed a scattered intensity vs. wave vector q typical of PAL with self-similar concentration profile. From these results, it was possible to determine PAL hydrodynamic thicknesses of adsorbed layers (εH) using the Rk values and according to a simple capillary bundle model. εH and Г values were then combined to estimate the PAL density. The impact of salinity could hence be interpreted in view of classical charge screening effect observed for solutions of polyelectrolytes. The impact of molecular weight was found qualitatively consistent with the increase in radius of gyration. Regarding the impact of hardness, stable εH and increased Г translated in an increase of the PAL density: this could be due to the creation of bridges between polymer charged monomers and divalent cations. As for the impact of flow velocity, increases of Rk and hence of εH was generally observed. Such behavior is consistent with a change of conformation of PAL, from coiled to stretched. This work stand as the first direct experimental evidence of "irreversible" PAL in three-dimensional porous media under flow. It also represents a consistent set of results summarizing the impact on PAL of parameters that are particularly relevant for field operations. The results and corresponding interpretations are meant to be used in reservoir simulation softwares to improve the predictability and economics of polymer flooding EOR.

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Diffusion de neutrons aux petits angles appliquée aux études d'interfaces et de systèmes confinés

Cited by 3 publications

References 31 publications

Small-Angle Neutron Scattering

Small-Angle Neutron Scattering

Small angle neutron scattering

New Insights on the Characterization of Polymer Adsorbed Layers in Porous Media

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