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Micro-particle entrainment from density mismatched liquid carrier system
S M Naser Shovon1, Adeeb Alam1, William Gramlich2
1Department of Mechanical Engineering, The University of Maine, Orono, ME, USA.
Scientific Reports
|June 13, 2022
Summary
This study investigates particle transfer in dip-coating mixtures, overcoming density mismatches using a polymer binder and stirring. Optimized methods enable controlled particle entrainment for novel manufacturing processes.
Area of Science:
- Materials Science
- Chemical Engineering
- Surface Science
Background:
- Micro-scale inorganic particles (>1 µm) pose challenges in dip-coating due to negative buoyancy and density mismatch with liquid carrier systems (LCS).
- Controlled particle delivery in dip-coating is crucial for manufacturing but hindered by density differences between particles and the liquid matrix.
Purpose of the Study:
- To investigate the particle transfer mechanism in complex density-mismatching mixtures for dip-coating applications.
- To optimize the liquid carrier system (LCS) and understand the influence of solid loading and binder concentration on particle entrainment.
- To identify coating regimes and critical parameters for effective particle transfer and substrate coverage.
Main Methods:
- Optimized an LCS using a polymer binder and evaporating solvent.
- Dispersed inorganic particles in the LCS via stirring at the 'just suspending' speed.
- Investigated the effects of solid loading and binder volume fraction on particle transfer at room temperature.
- Analyzed two distinct coating regimes: heterogeneous coating and effective viscous regime.
Main Results:
- Observed two coating regimes: heterogeneous (particle clusters) at low capillary numbers and effective viscous (full coverage) at higher capillary numbers.
- Found that 'zero' particle entrainment was not observed, attributed to binder presence and hydrodynamic particle flow from stirring.
- Determined critical film thicknesses for particle entrainment, which were smaller than previously reported values for similar binder concentrations.
- Demonstrated that stirring energy neutralizes density mismatch effects, with transferred particle matrices aligning with modified LLD expressions.
Conclusions:
- The study elucidates particle transfer mechanisms in density-mismatching dip-coating mixtures.
- Stirring energy effectively neutralizes density mismatch, enabling controlled high-volume solid transfer.
- Findings support the development of novel manufacturing processes for controlled particle deposition.
