Décomposition spinodale

Résumé

La décomposition spinodale est un processus par lequel un mélange de deux constituants ou plus peut se séparer en régions distinctes avec des concentrations des matériaux différentes. Ce processus diffère de la nucléation en ce sens que la séparation de phase due à la décomposition spinodale se produit à travers tout le matériau, et non uniquement au niveau de sites de nucléation. Notes et références Catégorie:Métallurgie

Source officielle

https://fr.wikipedia.org/wiki/D%C3%A9composition_spinodale

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Numerical approximation of phase field models for tumor growth

Léo Aurélio Diserens

In this project, we deal with the numerical approximation of problems described by a phase field model, which is nowadays popular to describe substances sharing sharp interfaces. We present the basis of the theory of mixtures required to introduce the spinodal decomposition and state the Cahn-Hilliard equations. Then, we use a four species model for tumor growth phenomenon, based on the theory of mixtures. Using the finite element method, we characterize the time evolution of a tumor, as well as the concentration of nutrients, in a wide range of scenarios described by a set of parameters.

2015

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Multi-phase phenomena remain at the heart of many challenging fluid dynamics problems. Molecular fluxes at the interface determine the fate of neighboring phases, yet their closure far from the continuum needs to be modeled. Along the hierarchy of kinetic approaches, a multi-phase particle method is devised in this study. Molecular interactions are expressed via stochastic forces driven by the white noise, coupled to the long-range attractions. The former is local and pursues diffusive approximation of molecular collisions, whereas the latter takes a global feature owing to mean-field forces. The obtained Fokker-Planck-Poisson combination provides an efficient work-flow for physics-driven simulations suitable for multi-phase phenomena far from the equilibrium. Besides highlighting the computational efficiency of the method, various archetypical and complex problems ranging from inverted-temperature-gradient between droplets to spinodal decomposition are explored. Detailed discussions are provided on different characteristics of the droplets dispersed in low/high density background gases; including the departure of heat-fluxes from Fourier's law as well as droplets growth in spinodal phases.

2020

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Aggregation dynamics, structure, and mechanical properties of bigels

Davide Fiocco, Giuseppe Foffi, Francesco Varrato

Recently we have introduced bigels, inter-penetrating gels made of two different colloidal species. Even if particles with simple short-range isotropic potential are employed, the selective interactions enable the tunability of the self-assembly, leading to the formation of complex structures. In the present paper, we explore the non-equilibrium dynamics and the phenomenology underlying the kinetic arrest under quench and the formation of bigels. We demonstrate that the peculiar bigel kinetics can be described through an arrested spinodal decomposition driven by demixing of the colloidal species. The role played by the presence of a second colloidal species on the phase diagram, as expanded to account for the increased number of parameters, is clarified both via extensive numerical simulations and experiments. We provide details on the realisation of bigels, by means of DNA-coated colloids (DNACCs), and the consequent imaging techniques. Moreover we evidence, by comparison with the usual one-component gel formation, the emergence of controllable timescales in the aggregation of the bigels, whose final stages are also experimentally studied to provide morphological details. Finally, we use numerical models to simulate the bigel response to mechanical strain, highlighting how such a new material can bear significantly higher stress compared to the usual one-component gel. We conclude by discussing possible technological uses and by providing insights on the viable research steps to undertake for more complex and yet tuneable multi-component colloidal systems.

Royal Soc Chemistry2014

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