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M Hütter

Publications and source records attributed to M Hütter.

4 recordsLinked to original sources
PubMed2001

Thermodynamically consistent incorporation of the Schneider rate equations into two-phase models.

We formulate a solid-liquid two-phase model including viscous stresses, heat conduction in the two phases, as well as heat exchange through the interface, and a phase change in the structure of nonequilibrium thermodynamics described by a general equation for the nonequilibrium reversible-irreversible coupling (GENERIC). The evolution of the microstructure is studied in terms of the Schneider rate equations introducing the nucleation rate and the radial growth rate of the solid phase. The application of the GENERIC structure shows that this radial growth factor is not an additional, independent material function but is to be expressed in terms of the difference in the chemical potentials, in the temperatures, and in the pressures between the two phases. The contribution due to the pressure difference appears in conjunction with the surface tension in such a way, that a driving force results only if deviations from a generalized version of the Laplace equation occur. Furthermore, it is found that for conditions under which the radial growth rate is zero, the nucleation rate must vanish.

Journal Article↗
PubMed2000

Local Structure Evolution in Particle Network Formation Studied by Brownian Dynamics Simulation.

The effect of solid content and colloidal interactions on the structure of forming networks of colloidal particles is studied by Brownian dynamics simulation. The different situations are compared in terms of the pair distribution function and the distribution of nearest neighbors around each particle. The results indicate that, in fast coagulation, the higher solid contents lead to a freezing-in of the liquid structure. Nevertheless, this effect can be reduced substantially by the introduction of a shallow secondary minimum and an energy barrier in the interaction potential. However, the structures resulting from such slow coagulation show a substantial degree of porosity, larger than those produced at the same solid content but by fast coagulation. It is also shown how the porosity (defined on a few particle diameters) is reflected in the distribution of nearest neighbors around the center particle, i.e., the very local conformation in the particle network. Fractal analysis shows that, at the relatively high volume fractions considered in this study, no intermediate fractal regime exists. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Lack of Syneresis during Gelation of Dense Colloidal Suspensions.

This study reports experimental results about the shrinkage of particle networks produced by pH-induced destabilization of dense colloidal suspensions. The resulting solid networks exhibit no syneresis effects, at least prior to aging of the gel. From this lack of syneresis it is concluded that the solidification in wet particle systems either is not purely determined by energy (but is also influenced by entropic effects) or cannot be explained within the framework of (static) equilibrium thermodynamics at all. Copyright 2000 Academic Press.

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