Powders, Grains, and Spheres

Powders, Grains, and Spheres addresses uses for powders as ceramic precursors or abrasive grains and applications of dense or hollow ceramic or glass spheres. 

If one is concerned with the characterization of dense smooth spheres, the concept of size is elementary and straight forward. If however one must deal with some of the powder grains found in industry, exacdy what is meant by size has to be defined very carefully. Consider for example the carbonblack profile shown in Figure 1.1(a) [6]. 

Similar materials are available based on potato starch, eg, PaseUi SA2 which claims DE below 3 and has unique properties based on its amylose—amylopectin ratio pecuhar to potato starch. The product contains only 0.1% proteia and 0.06% fat which helps stabilize dried food mixes compounded with it. Another carbohydrate raw material is waxy-maize starch. Maltodextrias of differeat DE values of 6, 10, and 15, usiag waxy-maize starch, are available (Staley Co.). This product, called Stellar, is offered ia several physical forms such as agglomerates and hoUow spheres, and is prepared by acid modification (49). Maltodextrias based oa com starch are offered with DEs of 5, 10, 15, and 18 as powders or agglomerates (Grain Processing Corp.). 

Solids appear in one of two forms, either as crystals or powders. The difference is one of size, since many of the powders we use are in reality very fine crystals. This, of course, depends upon the manner in which the solid is prepared. Nevertheless, most solids that we encounter in the real world are in the form of powders. That is, they are in the form of discrete small particles of varying size. Each particle has its own unique diameter and size. Additionally, their physical proportions can vary in shape from spheres to needles. For a given powder, aU grains will be the same shape, but the particle shape and size can be eiltered by the method used to create them in the first place. Methods of particle formation include ... 

Spectroscopic characterizations. Reflectance spectra are recorded on a Beckman 5240 spectrometer equipped with a reflectance sphere. Data processing by a microcomputer provides a plot of the Kubelka function FRoo versus wavenumber v. The zeolite powder, with an average grain size 1 urn, can be treated and evacuated before being transferred into the spectrometer cell made of Suprasil. 

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