A solid particle at a liquid-liquid interface has a wetting position that is different from its bulk powder handling behavior.
Define the Interface or Transport Basis
Jansen and Harting's primary particle-interface study, section V defines contact angle using particle position relative to the interface. For its stated spherical geometry, cos(theta) equals signed interface position minus particle-center position, divided by particle radius. Phase convention and displacement direction belong beside the result.
Review a Hypothetical Comparison
Take an idealized hypothetical sphere of radius 2 micrometres with a locally flat interface. Using the stated coordinate convention, interface position minus center position of +1 micrometre gives cos(theta)=0.5 and theta=60 degrees. A center on the interface gives 90 degrees. These are geometric examples, not measured adsorption energies. They show why an image showing particles somewhere in the liquid does not establish how they occupy the boundary.
Keep the Evidence with the Decision
Sketch both liquids, the particle center and the direction used for signed displacement. Check whether a sphere and a locally flat interface approximate the observation. Record whether particles actually remain at the interface and the distribution of observed positions. Compare wetting evidence before changing concentration to explain a particle-stabilized structure.
The source is a defined simulation study, not a universal phase diagram for all solid shapes. Rough or irregular particles, deformed boundaries and real detachment require additional evidence; this geometry does not predict a stable emulsion by itself.
Can the solid occupy the intended liquid-liquid boundary under the stated contact conditions?
This blank worksheet is for your own project. It contains no H M machine trial result.
| Review field | Reference or result | Responsible person |
|---|---|---|
| Liquid identities and angle convention | To complete | To complete |
| Particle shape, radius and interface approximation | To complete | To complete |
| Signed center displacement and angle | To complete | To complete |
| Observed interface occupancy and persistence | To complete | To complete |
Customer Questions
Does powder wettability alone establish interface occupancy?
No. Check the particle position and behavior in the actual pair of liquids.
Can the sphere equation be used for an irregular grain?
Only with a justified geometric model; the simple radius relation no longer follows automatically.
Does a 90-degree position guarantee stability?
No. It describes a geometric wetting position, not the complete stability of the dispersion.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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