Liquid bridge forces

The magnitude of agglomeration forces between powders depends on their surface forces and may involve electrostatic, van der Waals, or liquid-bridge forces which may occur when moisture is present [84]. 

Results from studies using calcium carbonate showed that, relative to dry powder, the effect of conditioning at 55% relative humidity (at 20 °C) increased agglomerate strength threefold, which was attributed to the development of liquid-bridge forces [86]. 

Lian G. Thornton C. Adams MJ. A theoretical study of the liquid bridge forces between two rigid spherical bodies. J Coll Interface Sci 1993 161 138-47. 

When a liquid bridge is extended by increasing the distance between the soMs, the bridge becomes unstable and breaks at a particular separation. On the other hand, these studies show how the liquid bridge force changes with drying. 

Incorporation of Liquid Bridge Force Model Tliis force model for simulating the forces due to the formation of liquid bridge within particles in a wet granular bed was taken from previous publication of the authors as shown in Figure 14.1 [ 12]. 

In this chapter the different types of interparticle forces and their relative importance as a function of particle size are summarized. Liquid bridge forces, which are specifically important to granulation processes, are covered in more detail. The rate processes important to granulation (wetting, growth, consolidation... 

Figure 13.2, after Rumpf (1962), illustrates the relative magnitude of the different bonds discussed above as a function of particle size. We see that van der Waals forces become important only for particles below 1 fim in size, adsorbed vapour forces are relevant below 80 fim and liquid bridge forces are active below about 500 m. 

The yield stress of powder compacts has previously been reported in Figure 32 for the case of slow yielding. However, the dependence of interparticle forces on shear rate clearly impacts wet mass rheology and therefore deformability. Figure 36 illustrates the stress-strain response of compacts, demonstrating that the peak flow or yield stress increases proportionally with compression velocity (41). In fact, in a similar fashion to dynamic liquid bridge forces, the peak flow stress of wet unsaturated compacts (initially pendular state) can be seen to also increase with Ca as follows (Fig. 37) ... 

In the limit of high viscosity, immobile liquid bridges formed from materials such as asphalt or pitch fail by tearing apart the weakest bond. Then adhesion and/or cohesion forces are Lilly exploited, and binding ability is much larger. 

From the experimental observation it is quite clear that the occurrence of the slug flow is rather an entrance phenomenon than one induced from the tube. Slug flow occurs if the speed of long gas bubbles is not high enough to overcome the strong surface tension force of the liquid bridge between them (Fig. 5.6b). 

When the sphere and plane are separated by a small distance D, as shown in Figure 4, then the force due to the Laplace pressure in the liquid bridge may be calculated by considering how the total surface free energy of the system changes with separation [1] ... 

Capillary forces increase in relationship to the relative humidity (RH) of the ambient air. At greater than 65% RH, fluid condenses in the space between adjacent particles. This leads to liquid bridges causing attractive forces due to the surface tension of the water. 

Consider two equal spheres held together by a liquid bridge, as shown in Fig. 4. Two forces contribute to the tensile strength of the bond in an additive fashion the pull due to surface tension at solid-liquid-gas contact line directed along the liquid surface and the negative capillary pressure or the... 

The actual ISE system consists of internal reference electrode 2, internal solution of the ion-selective electrode 2 and the membrane. This system is immersed in andysed solution (analyte) 1, in which reference electrode 1 is also immersed, usually connected through a liquid bridge. The electromotive force of cell (3.1.1) is... 

If the particles are wetted only partially by the fluid (melt), liquid bridges form and capillary forces develop between them. These can be divided into two parts that related to surface tension ... 

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