Anwar Hasmy

Sol-gel process simulation by cluster-cluster aggregation

The pair-correlation function, g(r, t), and its Fourier transform, the structure factor, S(q, t), were computed during the gelation process of identical spherical particles using the diffusion-limited cluster-cluster aggregation model in a box. This numerical analysis shows that the time evolution of the characteristic cluster size, ξ, exhibits a crossover close to the gel time, t g , which depends on the volumic fraction, c. In this model, t g tends to infinity when the box size, L, tends to infinity. For systems of finite sizes it is shown numerically that, when t < t g , the wave vector, q m , at which S(q,t) has a maximum, decreases as S(q m , t) -1/D , where D is an apparent fractal dimension of clusters, as measured from the slope of S(q, t). The time evolution of the mean number of particles per cluster, n, was also investigated. Numerical results are in qualitative agreement with small-angle scattering experiments in several systems.

SMALL-ANGLE SCATTERING BY FRACTAL AGGREGATES : A NUMERICAL INVESTIGATION OF THE CROSSOVER BETWEEN THE FRACTAL REGIME AND THE POROD REGIME

Fractal aggregates are built on a computer using off-lattice cluster-cluster aggregation models. The aggregates are made of spherical particles of different sizes distributed according to a Gaussian-like distribution characterised by a mean

FLUCTUATING BOND AGGREGATION : A MODEL FOR CHEMICAL GEL FORMATION

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Small-angle neutron scattering of aerogels: simulations and experiments

and a standard deviation

Percolation in cluster-cluster aggregation processes.

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Numerical study of pore sizes distribution in gels

. The wave vector dependent scattered intensity

Investigation of Dynamical Scaling in a Mutually Self-Similar Series of Base-Catalyzed Aerogels

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Effect of Cluster Deformations in the DLCA Modeling of the Sol-Gel Process

is computed in order to study the influence of the particle polydispersity on the crossover between the fractal regime and the Porod regime. It is shown that, given

Scaling theory and numerical simulations of aerogel sintering

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Gas transport in porous media: simulations and experiments on partially densified aerogels

, the location