Thermoelectric effect on charged colloids in the Hückel limit

We study the thermophoretic coefficient DT of a charged colloid. The non-uniform electrolyte is characterized in terms of densities and diffusion currents of mobile ions. The hydrodynamic treatment in the vicinity of a solute particle relies on the Hückel approximation, which is valid for particles smaller than the Debye length, a ≪ $\lambda$ . To leading order in the parameter a/$\lambda$ , we find that the coefficient DT consists of two contributions, a dielectrophoretic term proportional to the permittivity derivative d$\varepsilon$/dT , and a Seebeck term, i.e., the macroscopic electric field induced by the thermal gradient in the electrolyte solution. Depending on the particle valency, these terms may take opposite signs, and their temperature dependence may result in a change of sign of thermophoresis, as observed in several recent experiments

Mechanistic Understanding of Sticker Aggregation in Supramolecular Polymers: Quantitative Insights from the Plateau Modulus of Triblock Copolymers

Quantifying the impact of associative group aggregation on the mechanical properties of dense supramolecular networks remains a challenging problem. To address this question, we carry out coarse-grained molecular dynamics simulations of triblock copolymers consisting of a linear succession of hard (crystallizable) and soft (amorphous) segments. This molecular architecture offers the opportunity to increase the volume fraction of crystallites, serving as supramolecular aggregates, in a progressive and controlled fashion, allowing us to study its impact on the plateau modulus of the corresponding thermoplastic elastomers. By unifying these simulations with a recent mechanistic model and experimental data, we provide new quantitative insights into the microscopic origin of the mechanical reinforcement. Enhancement of the plateau modulus originates from the network’s topology at low crystallite content

Mechanistic Understanding of Sticker Aggregation in Supramolecular Polymers: Quantitative Insights from the Plateau Modulus of Triblock Copolymers

Quantifying the impact of associative group aggregation on the mechanical properties of dense supramolecular networks remains a challenging problem. To address this question, we carry out coarse-grained molecular dynamics simulations of triblock copolymers consisting of a linear succession of hard (crystallizable) and soft (amorphous) segments. This molecular architecture offers the opportunity to increase the volume fraction of crystallites, serving as supramolecular aggregates, in a progressive and controlled fashion, allowing us to study its impact on the plateau modulus of the corresponding thermoplastic elastomers. By unifying these simulations with a recent mechanistic model and experimental data, we provide new quantitative insights into the microscopic origin of the mechanical reinforcement. Enhancement of the plateau modulus originates from the network’s topology at low crystallite content

Cs diffusion mechanisms in UO2_2 investigated by SIMS, TEM, and atomistic simulations

International audienceExperimental investigations and atomistic simulations are combined to study the cesium diffusion processes at high temperature in UO2. After 133Cs implantation in UO2 samples, diffusion coefficients are determined using the depth profile evolution after annealing as measured by secondary ion mass spectrometry. An activation energy of 1.8 ± 0.2 eV is subsequently deduced in the 1300-1600 °C temperature range. Experimental results are compared to nudged elastic band simulations performed for different atomic paths including several types of uranium vacancy defects. Activation energies ranging from 0.49 up to 2.34 eV are derived, showing the influence of the defect (both in terms of type and concentration) on the Cs diffusion process. Finally, molecular dynamics simulations are performed, allowing the identification of preferential Cs trajectories that corroborate experimental observations