Dip-coating of suspensions

Withdrawing a plate from a suspension leads to the entrainment of a coating layer of fluid and particles on the solid surface. In this article, we study the Landau-Levich problem in the case of a suspension of non-Brownian particles at moderate volume fraction 10% < < 41%. We observe different...

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Bibliographic Details
Published in:Soft matter 2019-01, Vol.15 (2), p.252-261
Main Authors: Gans, Adrien, Dressaire, Emilie, Colnet, Bénédicte, Saingier, Guillaume, Bazant, Martin Z, Sauret, Alban
Format: Article
Language:English
Subjects:
Brownian motion
Coatings
Dip coatings
Entrainment
Fluid Dynamics
Immersion coating
Immersion plating
Particulates
Physics
Solid surfaces
Substrates
Thickness
Viscosity
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Summary:Withdrawing a plate from a suspension leads to the entrainment of a coating layer of fluid and particles on the solid surface. In this article, we study the Landau-Levich problem in the case of a suspension of non-Brownian particles at moderate volume fraction 10% < < 41%. We observe different regimes depending on the withdrawal velocity U , the volume fraction of the suspension , and the diameter of the particles 2 a . Our results exhibit three coating regimes. (i) At small enough capillary number Ca, no particles are entrained, and only a liquid film coats the plate. (ii) At large capillary number, we observe that the thickness of the entrained film of suspension is captured by the Landau-Levich law using the effective viscosity of the suspension η ( ). (iii) At intermediate capillary numbers, the situation becomes more complicated with a heterogeneous coating on the substrate. We rationalize our experimental findings by providing the domain of existence of these three regimes as a function of the fluid and particles properties. Three regimes of dip coating in non-Brownian suspensions are identified: pure liquid, heterogeneous coating and homogeneous suspension films.
ISSN:1744-683X
1744-6848
DOI:10.1039/c8sm01785a