Étude théorique et expérimentale de la diffusion des rayons X par les ensembles denses de particules

Fournet, G.

doi:10.3406/bulmi.1951.4736

Cited by 22 publications

(28 citation statements)

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“…Conventional SAXS analysis was performed using an analytical form factor. The SAXS data were modeled as polydisperse flat cylindrical discs [ 60 ] using a Schulz distribution for the number size distribution [ 61 ]. The same polydispersity distribution was assumed in both radius and thickness; however, with a 10 times smaller polydispersity ( σT / T ) of the thickness ( T ).…”

Section: Methodsmentioning

confidence: 99%

An Atomistic Model Describing the Structure and Morphology of Cu-Doped C-S-H Hardening Accelerator Nanoparticles

Sasso

Dalconi

Ferrari³

et al. 2022

Nanomaterials

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Calcium silicate hydrate (C-S-H) is the main binding phase in Portland cement. The addition of C-S-H nanoparticles as nucleation seeds has successfully been used to accelerate the hydration process and the precipitation of binding phases either in conventional Portland cement or in alternative binders. Indeed, the modulation of the hydration kinetics during the early-stage dissolution-precipitation reactions, by acting on the nucleation and growth of binding phases, improves the early strength development. The fine-tuning of concrete properties in terms of compressive strength and durability by designed structural modifications can be achieved through the detailed description of the reaction products at the atomic scale. The nano-sized, chemically complex and structurally disordered nature of these phases hamper their thorough structural characterization. To this aim, we implement a novel multi-scale approach by combining forefront small-angle X-ray scattering (SAXS) and synchrotron wide-angle X-ray total scattering (WAXTS) analyses for the characterization of Cu-doped C-S-H nanoparticles dispersed in a colloidal suspension, used as hardening accelerator. SAXS and WAXTS data were analyzed under a unified modeling approach by developing suitable atomistic models for C-S-H nanoparticles to be used to simulate the experimental X-ray scattering pattern through the Debye scattering equation. The optimization of atomistic models against the experimental pattern, together with complementary information on the structural local order from 29Si solid-state nuclear magnetic resonance and X-ray absorption spectroscopy, provided a comprehensive description of the structure, size and morphology of C-S-H nanoparticles from the atomic to the nanometer scale. C-S-H nanoparticles were modeled as an assembly of layers composed of 7-fold coordinated Ca atoms and decorated by silicate dimers and chains. The structural layers are a few tens of nanometers in length and width, with a crystal structure resembling that of a defective tobermorite, but lacking any ordering between stacking layers.

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Section: Methodsmentioning

confidence: 99%

An Atomistic Model Describing the Structure and Morphology of Cu-Doped C-S-H Hardening Accelerator Nanoparticles

Sasso

Dalconi

Ferrari³

et al. 2022

Nanomaterials

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“…The form factor of an oriented cylinder is given by Fournet (1951), Guinier, Fournet, and Walker (1955):…”

Section: Approximating the Sector Intensity Of Oriented Cylindersmentioning

confidence: 99%

“…Similarly, the vertical intensity can be obtained in case when the direction of 𝑄 is parallel to the 𝑦-axis, and 𝛼 𝑦 is the angle between 𝑄 (or the 𝑦-axis) and the axis of the cylinder. 𝛼 𝑥 and 𝛼 𝑦 can be calculated knowing the reference orientation of the object with respect to the detector (Fournet, 1951).…”

Section: Approximating the Sector Intensity Of Oriented Cylindersmentioning

confidence: 99%

Scattering from oriented objects analysed by the anisotropic Guinier–Porod model

2021

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Small angle scattering is frequently applied to study the anisotropy in complex soft matter systems. One emerging application is to probe the multi-scale structure in food matrices; while few models are available to describe the anisotropic scattering pattern in a quantitative, yet simple manner. For this purpose, anisotropy is introduced to the Guinier-Porod model to study the scattering from non-spherical objects with a preferred orientation. This generalised anisotropic Guinier-Porod model can be adapted to approximate the sector scattering from both cylinders and ellipsoids (both prolate and oblate). In practice, it is applied to describe the anisotropic scattering from fibres in a meat analogue made of calcium caseinate. A good agreement is found between fitted dimensions of the fibres and those observed from the microscopy image. The effect of orientation distribution on the shape and intensity of the scattering pattern is further discussed and three means to obtain the orientation distribution of the symmetry axis are proposed. Given the model is straightforward and the fitting remains phenomenological, it provides a novel approach to extract information from complex food systems.

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“…I 0 is a scaling factor. As the form factor P mb (q), we chose the cylinder form factor, P cyl (q), which features the cross-sectional radius R as well as the length L of the cylindrical brushes [35][36][37]. R and L are distributed according to Gaussian distributions, and their polydispersities are treated as free parameters.…”

Section: Model Fitting Of Sans Datamentioning

confidence: 99%

A molecular brush with thermoresponsive poly(2-ethyl-2-oxazoline) side chains: a structural investigation

et al. 2020

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The thermoresponsive behavior of a poly(2-oxazoline)-based molecular brush is investigated in aqueous solution. The molecular brush under study, PiPOx 100-g-PEtOx 17 , has a poly(2-isopropenyl-2-oxazoline) (PiPOx) backbone grafted with thermoresponsive poly(2-ethyl-2-oxazoline) (PEtOx) side chains. Since the backbone degree of polymerization is only a factor of~6 higher than the ones of the side chains, it features an architecture between a star-like polymer and a comb-like polymer. Its aqueous solution exhibits lower critical solution temperature (LCST) behavior with a cloud point temperature T cp = 40.5°C at 30 g L −1. The temperature-dependent structural evolution is disclosed using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). An increase of the molecular brush size is found upon heating from room temperature to T cp , which is attributed to the extension of the backbone resulting from the dehydration and collapse of the side chains. Above T cp , the size decreases again, which indicates the collapse of the whole molecular brush. Large aggregates are found to be present in the solution in the temperature range 25-50°C. These become more compact, as the temperature is increased across T cp .

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Étude théorique et expérimentale de la diffusion des rayons X par les ensembles denses de particules

Cited by 22 publications

References 0 publications

An Atomistic Model Describing the Structure and Morphology of Cu-Doped C-S-H Hardening Accelerator Nanoparticles

An Atomistic Model Describing the Structure and Morphology of Cu-Doped C-S-H Hardening Accelerator Nanoparticles

Scattering from oriented objects analysed by the anisotropic Guinier–Porod model

A molecular brush with thermoresponsive poly(2-ethyl-2-oxazoline) side chains: a structural investigation

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