Stepped drops, textures

SmA phase, the stepped drops as well as polygonal and fan-shape textures are also observed. 

In any catalyst selection procedure the first step will be the search for an active phase, be it a. solid or complexes in a. solution. For heterogeneous catalysis the. second step is also deeisive for the success of process development the choice of the optimal particle morphology. The choice of catalyst morphology (size, shape, porous texture, activity distribution, etc.) depends on intrinsic reaction kinetics as well as on diffusion rates of reactants and products. The catalyst cannot be cho.sen independently of the reactor type, because different reactor types place different demands on the catalyst. For instance, fixed-bed reactors require relatively large particles to minimize the pressure drop, while in fluidized-bed reactors relatively small particles must be used. However, an optimal choice is possible within the limits set by the reactor type. 

Design of a tailored texture requires a good knowledge of the effect of each unit operation, and especially of the peptization, on the properties and characteristics of the support. For example, if one wants to obtain specific texture on the final alumina support, the particle size and the powder dispersion must be controlled during the peptization step. Moreover, use and performance of specific manufacturing process (such as oil-drop or extrusion) depends on the dispersion of boehmite and may even require the use of stable suspensions. If stability of boehmite has been studied as a function of pH, salinity and... 

The first step in the identification of polymers is a critical visual examination. While the appearance of the sample may indicate whether it is essentially a raw polymer or a compounded and processed item, learning about its form, feel, odor, color, transparency or opacity, softness, stiffiiess, brittleness, bounce, and surface texture may be important in the process of the identification of the polymer. For example, polystyrene, the general purpose polymer, is transparent and brittle, and produces a characteristic metallic tinkle when objects molded from it are dropped or struck. 

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