Size reduction surface energy

Many attempts have been made to develop models which predict the behavior of materials undergoing size reduction. One proposal is that the energy expended in size reduction is proportional to the new surface formed (5). Another theory is that the energy required to produce a given reduction ratio (feed size product size) is constant, regardless of initial feed particle size (6). Practical results show, however, that both these theories are limited in their usehilness. 

Fig. 3. Stressing mechanisms (a) single particles or (b) a bed of particles cmshed between two solid surfaces impact of a particle against (c) a solid surface or (d) another particle (e) cutting (f) shearing forces or pressure waves and (g) plasma reaction, an example of size reduction by nonmechanical energy.

Modeling ofBubble-Induced Attrition. Merrick and Highley (1974) have modeled bubble-induced attrition as a comminution process. According to Rittinger s law of size reduction by abrasion (cfi, Perry, 1973), the rate of creation of new surface area AS Al is proportional to the rate of energy input Ah. At... 

Since the surface of unit mass of material is proportional to 1/L, the interpretation of this law is that the energy required for size reduction is directly proportional to the increase in surface. 

In practical operations, only about 1% of the input energy to the mill appears as new surface energy of the product. Nevertheless, empirical relations for power consumption based on the extent of size reduction have been developed. One such relation is... 

Because the surface energy per volume is larger for small particles and because the fundamental driving force for sintering is surface-energy reduction, compacts composed of smaller powders will typically sinter more rapidly. Smaller powders are more difficult to produce and handle therefore, predictions of sintering rate dependence on size are used to make choices of initial particle size. Herring s... 

Particle size reduction involves input of energy that gets disseminated during micronization process, along with formation of smaller particles having new surfaces. With an enormous increase in surface area, the newly formed particles need to be stabilized-fo prevent subsequent agglomeration induced by interparticulate interactions and maintain their existence as individual nanoentities. 

Most of these quantities can be measured by using either BET (Bmnauer, Emett, Teller surface area measurement) or X-ray diffraction methods. The fact that the necessary amount of energy to comminute solids depends on the particle size, the size reduction ratio and the solid can be expressed by empirical formulas. According to Beddow [18] three of the most common types are the equations by ... 

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