Contact diameter, displacement

Fig. 11 Effect of nanoparticle diameter on contact line displacement...

The contact deformation of these thermoplastic polymers was studied experimentally by pressing polymeric balls (of 4 mm diameter) with continuously increasing load (0.6 N/s) against an optically smooth glass surface and measuring both contact deformation displacement and contact size under load as described above (see Figure 1). The polymer balls had a mean peak-to-valley roughness of 0.6 - 1.0 im and a c.l.a. 

Typical plots of the variation of contact diameter and displacement in compression for increasing and decreasing loads for one of the polymers investigated are shown in Figure 6 together with theoretical curves calculated with the well known Hertzian formulas ... 

Figure 6. Contact diameter and contact deformation displacement curves.

The effect of the nanoparticle volume fraction on the displacement of the contact line becomes pronounced only at higher volume fractions. For example, the displacement of the contact line is 10 times the nanoparticle diameter or approximately 0.2 im for a nanoparticle volume fraction of 0.25, while there is no appreciable change in the contact line position when the volume fraction is 0.2. This non-linear dependence of contact line position on nanoparticle volume fraction is consistent with the form of Eq. 10, where the film energy contribution due to structural disjoining pressure is subtracted from the surface energy contribution. The extent of displacement of the con-... 

We have considered the case of a fluid wedge that can deform under the action of the disjoining pressure. Our simulations show that the extent of deformation of the meniscus (or fluid interface) increases with increase in the volume fraction of nanoparticles/micelles, when a decrease in the diameter of micelles and with a decrease in the capillary pressure resisting the deformation is smaller. The resulting deformation of the meniscus causes the contact line to move so that it displaces the fluid that does not contain the micelles (oil) in favor of the fluid that contains it (aqueous surfactant solution). 

Liquid-liquid contact in an RPB involves introduction of the heavy liquid at the inside diameter of the rotor and the light phase at the outside diameter. The two liquid phases move countercurrent to one another within the rotor packing. Centrifugal force causes the heavy liquid to move radially outward. This displaces the light liquid, which moves radially inward. The design of the rotor packing influences the contact between the two liquid phases (23,24). 

Example 2.1 Figure E2.1 (a) shows a packed bed of height 1 m with monodispersed glass beads (silica glass) in a large container. Estimate the elastic displacement and contact area of a particle at the bottom of the bed. The density of the glass beads is 2,500 kg/m3. The particle diameter is 1 cm. 

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