Effect of shear rate on aggregate size and structure in the process of aggregation and at steady state

Bubáková, Petra; Pivokonský, Martin; Filip, Petr

doi:10.1016/j.powtec.2012.11.014

Cited by 85 publications

(68 citation statements)

References 50 publications

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“…where D2 is the 2-D fractal dimension defined for relating the characteristic length to the projected surface area in a projected plane [7,9,25,26]. For a perfectly spherical particle, D2 equals to 2.…”

Section: Fractal Dimension Analysesmentioning

confidence: 99%

“…where Dpf relates the perimeter to the projected surface area in a projected plane [7][8][9]27,28]. The value for Dpf is between 1 and 2, with the value of 1corresponding to a spherical floc and the value of 2 corresponding to a linear one.…”

Section: Fractal Dimension Analysesmentioning

confidence: 99%

“…For the fractal flocs formed in a water-sediment mixture, properties such as volume, mass and density should be scaled as a power of their characteristic size (the exponent has been termed a three-dimensional (3-D) fractal dimension).Thus, this fractal dimension is a measure of how primary particles fill the entire space of the floc. Similar to the 3-D fractal dimension, 2-D, 1-D and perimeter-based fractal dimensions have been defined and used to characterize the extent of the morphological irregularity of the floc boundary and/or its shape in the projected plane [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…In the first trend, the median size distribution of the flocs rapidly increases with time at the beginning of flocculation development and then continually slows down until a steady state is approached [7][8][9][10][11][12][13][14][15][16][17][18][19]. This type of size-time profile is henceforth referred to as type I.…”

Section: Introductionmentioning

confidence: 99%

“…This type of size-time profile is henceforth referred to as type I. However, the profile is referred to as type II when the median size initially increases to a maximum value with time and then decreases again before reaching a steady state [9,11,[19][20][21][22][23][24]. This peak in the size-time curve during the aggregation process potentially occurs as a result of breakups and/or restructurings (breakages and re-aggregations) of the flocs according to recent studies conducted by Bubakova et al and Selomulya et al [9,22].…”

Section: Introductionmentioning

confidence: 99%

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Fractal Dimension of Cohesive Sediment Flocs at Steady State under Seven Shear Flow Conditions

Zhu

Wang

et al. 2015

Water

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Abstract:The morphological properties of kaolin flocs were investigated in a Couette-flow experiment at the steady state under seven shear flow conditions (shear rates of 5.36, 9.17, 14, 24, 31, 41 and 53 s −1 ). These properties include a one-dimensional (1-D) fractal dimension (D1), a two-dimensional (2-D) fractal dimension (D2), a perimeter-based fractal dimension (Dpf) and an aspect ratio (AR). They were calculated based on the projected area (A), equivalent size, perimeter (P) and length (L) of the major axis of the floc determined through sample observation and an image analysis system. The parameter D2, which characterizes the relationship between the projected area and the length of the major axis using a power function, , decreased as the shear rate increased almost linearly. The parameter AR, which is the ratio of the length of the major axis and equivalent diameter, decreased from 1.56, 1.59, 1.53 and 1.51 in the low shear rate group to 1.43, 1.47 and 1.48 in the high shear rate group. These changes in Dpf and AR show that the flocs become less convoluted and more symmetrical and that their boundaries become smoother and more regular in the high shear rate group than in the low shear rate group due to breakage and possible restructuring processes. To assess the effects of electrolyte and sediment concentration, 0.1 mol/L calcium chloride (CaCl2) and initial sediment concentration from 7.87 × 10 were used in this preliminary study. The addition of electrolyte and increasing sediment concentration could produce more symmetrical flocs with less convoluted and simpler boundaries. In addition, some new information on the temporal variation of the median size of the flocs during the flocculation process is presented.

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Section: Fractal Dimension Analysesmentioning

confidence: 99%

Section: Fractal Dimension Analysesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fractal Dimension of Cohesive Sediment Flocs at Steady State under Seven Shear Flow Conditions

Zhu

Wang

et al. 2015

Water

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Conveying Advanced Li‐ion Battery Materials into Practice The Impact of Electrode Slurry Preparation Skills

Kraytsberg

Ein‐Eli

2016

Advanced Energy Materials

213

165

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Li‐ion batteries (LIB's) are of the greatest practical utility for portable electronics and electric vehicles (EV's). LIB energy, power and cycle life performances depend on cathode and anode compositions and morphology, electrolyte composition and the overall cell design. Electrode morphology is influenced by the shape and size of the active material (AM), conductive additive (CA) particles, the polymeric binder properties, and also on the AM/CA/binder mass ratio. At the same time, it also substantially depends on the electrode preparation process. This process is usually comprised of mixing a solvent, a binder, AM and CA powders, and casting the resulting slurry onto a current collector foil followed by a drying process. Whereas the problems of electrode morphology and their influence on the LIB‐electrode performance always receive a proper attention, the influence of slurry properties and slurry preparation techniques on the electrode morphology is often overlooked or at least underrated. The present work summarizes the current state‐of‐the‐art in the field of LIB‐electrode precursor slurries preparation, characterized by multicomponent compounds and large variations in sizes and shapes of the solid components. Approaches to LIB‐electrode slurry preparation are outlined and discussed in the context of the ultimate LIB‐electrode morphology and performance.

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In situ characterization of floc morphology by image analysis in a turbulent Taylor–Couette reactor

et al. 2014

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in Wiley Online Library (wileyonlinelibrary.com)Flocculation of bentonite was performed in a turbulent Taylor-Couette reactor under various shear rates. Image processing enabled to determine various morphological characteristics of individual flocs. Not only their mean values but also their distributions were studied under various hydrodynamic conditions. Relevant properties were selected. The temporal evolution of radius of gyration and circularity distributions was monitored during the flocculation process. Although size and shape are obviously correlated, this article points out that their dependency to hydrodynamics is different, showing that flocs of similar sizes produced under different hydrodynamic conditions exhibit different shapes. The sizes are calibrated by the turbulence as the double radius of gyration is close to Kolmogorov microscale, whereas the circularity seems correlated to the rotation speed.

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Effect of shear rate on aggregate size and structure in the process of aggregation and at steady state

Cited by 85 publications

References 50 publications

Fractal Dimension of Cohesive Sediment Flocs at Steady State under Seven Shear Flow Conditions

Fractal Dimension of Cohesive Sediment Flocs at Steady State under Seven Shear Flow Conditions

Conveying Advanced Li‐ion Battery Materials into Practice The Impact of Electrode Slurry Preparation Skills

In situ characterization of floc morphology by image analysis in a turbulent Taylor–Couette reactor

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