scholarly journals Cellular Automata Modeling of Silica Aerogel Condensation Kinetics

Gels ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 50
Author(s):  
Nina H. Borzęcka ◽  
Bartosz Nowak ◽  
Rafał Pakuła ◽  
Robert Przewodzki ◽  
Jakub M. Gac
Keyword(s):  
Condensation Reaction ◽  
Gelation Time ◽  
Aggregate Size ◽  
Collision Probability ◽  
Model Parameters ◽  
Gel Properties ◽  
Diffusion Limited Aggregation ◽  
Diffusion Limited ◽  
Kinetics Of ◽  
Simulation Time

The formation of silica aerogels and the kinetics of condensation were investigated numerically. The influence of the reaction-limited to the diffusion-limited aggregation (RLA to DLA) transition on the reaction kinetics curves and the evolution of the aggregate size distribution during condensation were examined. The 2D cellular automaton was developed and applied to reflect the process of secondary particle aggregation. Several tendencies were observed due to the adjustment of the model parameters: the probability of condensation reaction and the particles’ concentration. The final wet-gel structures’ visualizations proves that the structure becomes more dense and compact due to entering the RLA regime. The simulation time (associated with the gelation time) decreased along with the increase in both model parameters. The lower the collision probability, the slower reaction becomes, and particles are more likely to penetrate the structure deeper until they finally join the aggregate. The developed model reflects the condensation process’s nature and its mechanisms properly and indicates a significant potential for further aerogel synthesis investigations and for the prediction of wet-gel properties according to condensation parameters.

Влияние температуры отжига на кинетику процесса алюминий-индуцированной кристаллизации тонких пленок аморфного субоксида кремния

2021 ◽  
Vol 47 (21) ◽  
pp. 39
Author(s):  
И.Е. Меркулова ◽  
А.О. Замчий ◽  
Н.А. Лунев ◽  
В.О. Константинов ◽  
Е.А. Баранов -=SUP=-1-=/SUP=-
Keyword(s):  
Annealing Temperature ◽  
Silicon Oxide ◽  
Arrhenius Plot ◽  
Nucleation Density ◽  
Diffusion Limited Aggregation ◽  
Annealing Temperatures ◽  
Diffusion Limited ◽  
First Time ◽  
Kinetics Of ◽  
Induced Crystallization

In this work, the kinetics of aluminum-induced crystallization (AIC) of non-stoichiometric silicon oxide a-SiO0.25 was investigated for annealing temperatures of 370, 385 and 400 °C, as a result of which thin films of polycrystalline silicon were obtained. It is shown that for low annealing temperatures, the surface morphology of the crystalline material is represented by dendric structures corresponding to the growth model with diffusion-limited aggregation. In addition, with an increase in the annealing temperature, the nucleation density increases from 3 to 53 mm–2. From the Arrhenius plot, the activation energy of the AIC process of a-SiO0.25 was obtained for the first time, which was 3.7±0.4 eV.

Fractal Concepts And Aggregation Of Iron Oxides

1990 ◽  
Vol 180 ◽  
Author(s):  
R. Amal ◽  
J.A. Raper ◽  
T.D. Waite
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Iron Oxides ◽  
Aggregate Size ◽  
Fractal Dimensions ◽  
Aggregation Kinetics ◽  
Diffusion Limited ◽  
Scattering Measurements ◽  
The Relationship ◽  
Kinetics Of

ABSTRACTThe modelling of the aggregation kinetics of iron oxides has been succesful in predicting the increase in aggregate size as determined by dynamic light scattering measurements. The aggregates were found to exhibit fractal behaviour with fractal dimensions obtained from the scattering exponent in static light scattering studies dependent on the aggregation mechanism and ranging from 2.3 for rapid (diffusion limited) to 2.8 for slow (reaction limited) aggregation. Polydispersity and restructuring of aggregates were found not to affect the relationship between scattering exponent and aggregate fractal dimension. Excellent correspondence over a range of temperatures and ionic strengths has been obtained between results of sizing experiments using dynamic light scattering and sizes predicted using a modified Smoluchowski model incorporating fractal dimensions.

scholarly journals Investigation into mechanisms and kinetics of asphaltene aggregation in toluene/n-hexane mixtures

2019 ◽  
Vol 17 (2) ◽  
pp. 457-466
Author(s):  
Bahram Soltani Soulgani ◽  
Fatemeh Reisi ◽  
Fatemeh Norouzi
Keyword(s):  
Image Processing ◽  
Fractal Theory ◽  
Particle Growth ◽  
Force Balance ◽  
Asphaltene Precipitation ◽  
Diffusion Limited Aggregation ◽  
Model Calculations ◽  
Diffusion Limited ◽  
Kinetics Of ◽  
And Diffusion

Abstract Determining the rate of asphaltene particle growth is one of the main problems in modeling of asphaltene precipitation and deposition. In this paper, the kinetics of asphaltene aggregation under different precipitant concentrations have been studied. The image processing method was performed on the digital photographs that were taken by a microscope as a function of time to determine the asphaltene aggregation growth mechanisms. The results of image processing by MATLAB software revealed that the growth of asphaltene aggregates is strongly a function of time. Different regions could be recognized during asphaltene particle growth including reaction- and diffusion-limited aggregation followed by reaching the maximum asphaltene aggregate size and start of asphaltene settling and the final equilibrium. Modeling has been carried out to predict the growth of asphaltene particle size based on the fractal theory. General equations have been developed for kinetics of asphaltene aggregation for reaction-limited aggregation and diffusion-limited aggregation. The maximum size of asphaltene aggregates and settling time were modeled by using force balance, acting on asphaltene particles. Results of modeling show a good agreement between laboratory measurements and model calculations.

Anisotropy and Cluster Growth by Diffusion-Limited Aggregation

1985 ◽  
Vol 55 (13) ◽  
pp. 1406-1409 ◽  
Author(s):  
Robin C. Ball ◽  
Robert M. Brady ◽  
Giuseppe Rossi ◽  
Bernard R. Thompson
Keyword(s):  
Cluster Growth ◽  
Diffusion Limited Aggregation ◽  
Diffusion Limited

The Formation of Cu3Si from Cu/a-Si Multilayers

1997 ◽  
Vol 481 ◽  
Author(s):  
R. R. Chromik ◽  
W. K. Neils ◽  
E. J. Cotts
Keyword(s):  
Diffusion Couples ◽  
X Ray Diffraction ◽  
Limited Growth ◽  
Scanning Calorimetry ◽  
Individual Layer ◽  
Diffusion Limited ◽  
Reaction Constant ◽  
Multilayered Composites ◽  
Reaction Constants ◽  
Kinetics Of

ABSTRACTThe kinetics of the formation of Cu3Si in Cu/a-Si diffusion couples have been investigated by means of differential scanning calorimetry and x-ray diffraction. Multilayered composites of average stoichiometry Cu3Si were prepared by sputter deposition with individual layer thicknesses varying in different samples between 2 and 100 nm. We observed diffusion limited growth of Cu3 Si upon annealing these diffusion couples below 500 K. Reaction constants were measured for a temperature range of 455 to 495 K for thicknesses of growing Cu3Si between 2.6 and 80 nm. The temperature dependence of the reaction constant, k2, was characterized as k2 = k0 exp(− Ea/kbT) with activation energy, Ea = 1.0 eV/atom and pre-factor, k0 = 1.9×10−3 cm2/s.

Deterministic Growth of Diffusion-Limited Aggregation with Quenched Disorder

1990 ◽  
Vol 13 (4) ◽  
pp. 341-347 ◽  
Author(s):  
A Hansen ◽  
E. L Hinrichsen ◽  
S Roux ◽  
H. J Herrmann ◽  
L. de Arcangelis
Keyword(s):  
Quenched Disorder ◽  
Diffusion Limited Aggregation ◽  
Diffusion Limited

Multifractal spectrum of off-lattice three-dimensional diffusion-limited aggregation

1992 ◽  
Vol 46 (6) ◽  
pp. R3016-R3019 ◽  
Author(s):  
Stefan Schwarzer ◽  
Marek Wolf ◽  
Shlomo Havlin ◽  
Paul Meakin ◽  
H. Eugene Stanley
Keyword(s):  
Three Dimensional ◽  
Multifractal Spectrum ◽  
Diffusion Limited Aggregation ◽  
Diffusion Limited ◽  
Dimensional Diffusion
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