flow and drying simulation of nanoparticle suspension on...
TRANSCRIPT
ISCST2010, St. Paul, USA /14
Flow and Drying Simulation of Nanoparticle Suspension on Substrate
M. Fujita, O. Koike, Y. Yamaguchi
Department of Chemical System Engineering,The University of Tokyo, Japan
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ISCST2010, St. Paul, USA /14
Outline
• Continuous coating of nanoparticles suspension on substrate
• Direct simulation model for nanoparticles suspension in flow and drying
• Demonstration of present simulation model
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ISCST2010, St. Paul, USA /14
Continuous coating on substrate
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film
suspension
structure formation
flow
drying
ISCST2010, St. Paul, USA /14
Peclét numbers for flow and drying
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flow Peclét number drying Peclét number
ratio of Peclét numbers
Both flow and drying influence structure formation
ISCST2010, St. Paul, USA /14
Objectives of this study
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• Develop direct simulation model for nanoparticles suspension in flow and drying
• Perform flow and drying simulations of nanoparticles suspension on substrate
• Quantify structure formation of nanoparticles and evaluate effect of ratio of Peclét numbers
ISCST2010, St. Paul, USA /14
Direct simulation model
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• Solves gas-liquid two phase flow on lattice using VOF method
• Solves translational motion and rotational motion of each particle
• Couples motion of particle with flow of solvent using fictitious domain method
Interparticle hydrodynamic interaction is included without analytical model
ISCST2010, St. Paul, USA /14
Equations of fluid motion
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fluctuating stress
acceleration
VOF function
evaporation rate
ISCST2010, St. Paul, USA /14
Equations of particle motion
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acceleration
acceleration
ISCST2010, St. Paul, USA /14
Simulation domain
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drying
sliding substrate
0.4 μm
periodic boundary
lattice points = 80 x 80 x 40
1 μm 1 μm
ISCST2010, St. Paul, USA /14
Simulation conditions
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• nanoparticles
• solvent
• sliding substrate
d = 0.1 μm, φ0 = 15 vol%, ζ-potential = -50 mV
water in normal temperature, Ped = 930
ζ-potential = -50 mV, Pef = 93, 930
Pef / Ped = 0.1, 1
concentrated repulsive system
ISCST2010, St. Paul, USA /14
Pef / Ped = 0.1 Pef / Ped = 1
Simulation results
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low speed coating high speed coating
ISCST2010, St. Paul, USA /14
Quantification of structure formation
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Non-dimensional Boundary Area (NBA)
k : coordinate numbern(k) : number of particles with coordinate number of kN : total number of particles
NBA = 0 : close-packedNBA = 1 : dispersed
NBAarea of aggregates
total area of particles=
ISCST2010, St. Paul, USA /14
Effect of ratio of Peclét numbers
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variation of NBA with thickness of wet film
Pef / Ped = 1
compaction due to capillary interaction
Pef / Ped = 0.1
flow induced aggregation
collapse of aggregates
ISCST2010, St. Paul, USA /14
Conclusion
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• Developed direct simulation model for nanoparticles suspension in flow and drying
• Quantified structure formation of nanoparticles in flow and drying by use of NBA
• As ratio of Peclét numbers increases, compactness of final structure of nanoparticles decreases.