Light scattering study of fractal cluster aggregation near the free molecular regime

Oh, Chang-Hwan; Sorensen, C. M.

doi:10.1016/s0021-8502(96)00488-0

Cited by 79 publications

(63 citation statements)

References 47 publications

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“…For particles aggregating in solution, one would expect mass fractals, because such structures usually form at relatively low local particle concentrations and considerably large diffusion lengths. [15][16][17][18][19][20][21] This fact is exemplified by the common observation of such aggregates in nature. Important to note is that the mathematical formalism used for describing these structures is well established.…”

Section: Introductionmentioning

confidence: 88%

“…The fractal nature of colloids can be experimentally quantified using scattering techniques, and based on a combination of theoretical and experimental evidence [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] two distinct scaling laws have been used to describe experimental observations: mass fractals and surface fractals. Mass fractal scaling can be associated with the packing efficiency of an aggregate, which in turn depends on the type of aggregation, e.g., diffusion or reaction limited mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…Mass fractal scaling can be associated with the packing efficiency of an aggregate, which in turn depends on the type of aggregation, e.g., diffusion or reaction limited mechanism. [13][14][15][16][17][18][19][20][21] On the other hand, surface fractal scaling only relates to the perimeter of a particle or aggregate of particles and correlates with its specific surface area. [1][2][3][4][5] The core idea behind mass fractals stems from our need to statistically describe aggregation processes involving primary particles.…”

Section: Introductionmentioning

confidence: 99%

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Not just fractal surfaces, but surface fractal aggregates: Derivation of the expression for the structure factor and its applications

Besselink

Stawski

Driessche

et al. 2016

The Journal of Chemical Physics

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Densely packed surface fractal aggregates form in systems with high local volume fractions of particles with very short diffusion lengths, which effectively means that particles have little space to move. However, there are no prior mathematical models, which would describe scattering from such surface fractal aggregates and which would allow the subdivision between inter-and intraparticle interferences of such aggregates. Here, we show that by including a form factor function of the primary particles building the aggregate, a finite size of the surface fractal interfacial sub-surfaces can be derived from a structure factor term. This formalism allows us to define both a finite specific surface area for fractal aggregates and the fraction of particle interfacial sub-surfaces at the perimeter of an aggregate. The derived surface fractal model is validated by comparing it with an ab initio approach that involves the generation of a "brick-in-a-wall" von Koch type contour fractals. Moreover, we show that this approach explains observed scattering intensities from in situ experiments that followed gypsum (CaSO 4 ·2H 2 O) precipitation from highly supersaturated solutions. Our model of densely packed "brick-in-a-wall" surface fractal aggregates may well be the key precursor step in the formation of several types of mosaic-and meso-crystals. C

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Not just fractal surfaces, but surface fractal aggregates: Derivation of the expression for the structure factor and its applications

Besselink

Stawski

Driessche

et al. 2016

The Journal of Chemical Physics

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“…Two forms, developed by Fuchs (1964) and Dahneke (1983) respectively, are available for estimating f c . We use Dahneke's form following Rogak and Flagan (1992b), and Oh and Sorensen (1997). It should be noted that the Epstein equation is for spherical particles.…”

Section: Discrete General Dynamic Equationmentioning

confidence: 99%

“…A number of numerical studies have addressed the agglomerate formation, particularly during Brownian coagulation (e.g., Wu and Friedlander 1993a;Vemury and Pratsinis 1995;Oh and Sorensen 1997;Kostoglou and Konstandopoulos 2001;Dekkers and Friedlander 2002;Naumann 2003). The aggregates are commonly assumed to be fractal-like.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Acoustic Agglomeration Processes of Poly-Disperse Solid Particles

Sheng

Shen

2007

Aerosol Science and Technology

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This article presents the simulation of acoustic agglomeration of poly-disperse solid particles with the direct simulation Monte Carlo method. The modelled processes include the agglomeration due to the orthokinetic and hydrodynamic mechanisms, Brownian coagulation and wall deposition. The aggregates formed during the agglomeration process were characterised as mass fractal aggregates with an equivalent radius to estimate the average radius of the primary particles in individual aggregates. Acoustic agglomeration of fly ash with a lognormal size distribution and TiO 2 particles with a bimodal size distribution was simulated and validated against the experimental data in the literature. It was found that the acoustic agglomeration process of solid particles could be represented with a modified version of Song's orthokinetic model and König's hydrodynamic equation that account for the fractal-like morphology of the aggregates. The fractal dimensions of around 1.8 and 2.2 were obtained for the fly ash and TiO 2 particles, respectively, consistent with the values reported for the aggregates in the literature. The poly-disperse nature of the primary particles is essential to the simulation; assuming mono-disperse primary particles leads to a significant underestimation of the agglomeration rate and the particle size growth particularly during the early stages of the acoustic agglomeration process. Particle deposition on the chamber walls also has some effect on acoustic agglomeration.

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Mesoscale Modelling of Nanoparticle Formation

Goudeli

2021

Metal Oxide Nanoparticles

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Light scattering study of fractal cluster aggregation near the free molecular regime

Cited by 79 publications

References 47 publications

Not just fractal surfaces, but surface fractal aggregates: Derivation of the expression for the structure factor and its applications

Not just fractal surfaces, but surface fractal aggregates: Derivation of the expression for the structure factor and its applications

Simulation of Acoustic Agglomeration Processes of Poly-Disperse Solid Particles

Mesoscale Modelling of Nanoparticle Formation

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