Objectives of size enlargement

Size enlargement processes are used in many industries today with the desired results depending on the particular application. In each case, however, the substitution of granular material for fine powders yields a number of beneficial effects. The benefits and objectives of size enlargement, together with some examples of their application, may be summarized as follows  

Production of useful structural forms and shapes, as in the pressing of intricate shapes in powder metallurgy or the manufacture of spheres by planetary rolling. 

Early usage Glassmaking, pottery Ancient technique of Solid molded forms con- 

1800 Development of mechanized forming methods essentially the same as modern techniques. heating and hot forging to shape. Development of medici- 

1850 nal tablets by die compaction of powders. Early single punch and rotary tablet machines 

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Objectives of size enlargement, 1 Onion skin growth, 54, 152... 

Table 1 Objectives of Size Enlargement Production of a useful structural form...

Classification of size enlargement methods reveals two distinct categories (8,39). The first is forming-type processes in which the shape, dimensions, composition, and density of the individual larger pieces formed from finely divided materials are of importance. The second is those processes in which creation of a coarse granular material from fines is the objective, and the characteristics of the individual agglomerates are important only in their effect on the properties of the bulk granular product. 

A simple approach to specifying a suitable size enlargement method for a given application is by analogy to techniques currently used for similar materials. If a similar material can be identified in the applications summary of Table 1.4 (or in the more detailed information given in later chapters), and if process objectives are similar in terms of agglomerate size, strength, etc., then the methods used for the established product may well be applicable to the new material. 

A more fundamental approach to process selection first requires a clear definition of the problem and size enlargement objectives. This is followed by comparison with the capabilities of the available processes as catalogued in Table 1.3 and in greater detail in later chapters. Promising methods can then be selected and the clearly unsuitable methods ruled out. Factors to be considered in this comparison include ... 

A primary objective in preparing this book was to present a generalized account of the many size enlargement techniques scattered throughout these diverse industries, with emphasis on similarities and unifying characteristics whenever possible. A related objective was to allow the reader to understand the underlying principles so that successful techniques from other industries can be adapted to the application of his particular concern. 

The traditional methods for the agglomeration of fine particles in liquids, such as flocculation (see Section 10.2.2), rely on relatively small interparticle bonding forces to form rather weak agglomerates. The objective of these size enlargement procedures is simply to remove the fine particles from the liquid, thereby cleaning a contaminated effluent. 

Microscopy is an unusual scientific discipline, involving as it does a wide variety of microscopes and techniques. All have in common the abiUty to image and enlarge tiny objects to macroscopic size for study, comparison, evaluation, and identification. Few industries or research laboratories can afford to ignore microscopy, although each may use only a small fraction of the various types. Microscopy review articles appear every two years m. Jinalytical Chemistty (1,2). Whereas the style of the Enclyclopedia employs lower case abbreviations for analytical techniques and instmments, eg, sem for scanning electron microscope, in this article capital letters will be used, eg, SEM. 

Now you keep the tank in your room to help visualize intersections of 3-D objects with 2-D worlds. You reach into the water and withdraw a ball. Here s what a sphere looks like to an inhabitant of Flatland. The surface of the water is a metaphor for Flatland. You push the ball down so that it just touches the water at a point. You push further and the point turns into a circle. The circle enlarges until it reaches a maximum size and then shrinks back down to a point as you push the sphere under the water. The point disappears. 

Microscopy. A broad definition of microscopy is the observation and measurement of optical parameters with any instrument that uses energy sources such as photons, electrons or X-rays to provide an enlarged image of an object. Energetic material parameters that have been observed and measured include quantity, size, shape and color (Expls Refs 12-15, 19, 20, 25, 25a, 27, 28,... 

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