Lateral Morphology Characterizations

As will be demonstrated later, morphology and physicochemical properties of reinforcing fillers are of crucial importance because they directly define their reinforcement ability. Their characterization formerly was based essentially on morphological properties (surface area and structure), but because of the use of silicas as reinforcing filler, there is now a strong need for dispersibility and surface chemistry characterization. 

Imaging of Surfaces—Analysis of Surface Morphology. Several important techniques can help answer the question what does the surface look like This question is often the first one to be posed ia the characterization of a new surface or iaterface. Physical imaging of the surface is necessary to distinguish the relevant features important for understanding the whole surface and is essential for accurate iaterpretation of data from other surface analysis techniques which might later be appHed to a more limited region of the surface or iaterface. 

Another magnitude that characterizes the surface morphology is the lateral correlation length, (L, t), which represents the typical width of these structures. DST applies to systems in which, depending on the temporal range, f (L, t) follows the expressions ... 

In a later study by the Schmidt group (27), electron microscopy was used to characterize morphological changes in microspheres (<0.6 cm in diameter) of Pt, Rh, Pd, and Pt-Rh alloy in a number of reaction environments the reactions were ammonia oxidation, ammonia decomposition, and propane oxidation. No other experimental techniques, such as weight-loss measurements, were employed. After prolonged exposure to reaction mixtures of ammonia and air at temperatures less than 727°C, the surfaces of the spheres were reconstructed to favor specific crystal planes. The structure of the facets was found to be a function of the reaction mixture, temperature, and metal (Fig. 13). In the same reaction mixtures, as well as in pure ammonia at higher temperatures... 

Fourth, the vibrational frequency of the adsorbed species undergoes coverage-dependent shifts Av as a consequence of dynamic and static effects (see Section IV.A.4). The shift depends on the type of bonding and the density of cationic centers on the face. Several examples of coverage effects of this type are reported in the following. It will be shown later that this information also has morphological implications because different faces can be characterized by different bonds and cation densities (and hence by different static and dynamic shifts of the vibrational frequency). 

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