Surface area, variations

Experimental Observations. Whereas many experiments have been performed on single-droplet vaporization (21,22), most of them are conducted under the influence of either natural and/or forced convection, which not only distorts spherical symmetry, but also produces unwanted temporally varying convective effects on the vaporization process as the droplet size diminishes. The observations on the droplet surface area variations, however, do agree qualitatively with the predicted behavior of the transient models shown in Figure 4. 

Hodson M. E. (1999) Micropore surface area variation with grain size in unweathered alkali feldspars implications for surface roughness and dissolution studies. Geochim. Cosmochim. Acta 62(21-22), 3429-3435. 

It can also be observed that despite the same copper surface areas of 12 m2/g the Cu-LaZr ([ex carbonate] 550) system has a noticiable different catalytic behavior that Cu-LaZr ([ex oxalate] 710). This proves that, appart the copper surface areas, variation of morphology, presence of impurities as well as other factors related with the preparation can be responsible for difference of catalytic properties related to the preparation technique. 

For MoOa-PjOs catalysts, a maximum in isopropyl alcohol activity and presumably for surface acidity) was found when P/Mo = 0.1. Some of the behaviour could be accounted for by surface area variation with composition, but P2O5 alone is of low acidity and some enhencement must be caused by interaction of P2O5 and M0O3 to give a new kind of acid site. 

The deposits show nanostructures that, apart from sUghtly increased dimensions of the material, are very similar to the structure of the LLC phases they are derived from. These new electrode surfaces are adherent, macroscopically smooth (see Fig. 15) and shiny and expectedly show high specific surface areas. Variations in the deposition conditions, such as temperature and deposition potential, cause dramatic changes in the specific surface area, nanostructure and macroscopic morphology of the films, providing an additional tool to tailor the surface properties of such electrodes [62]. 

Surface area variations among the copolymers, preferential adsorption of proteins, and the... 

Figure 7(a) SPC charts shov/ing yttria and surface area variations in the milled powders... 

Many technologies and natural phenomena involve processes of fast expansion or compression of fluid interfaces covered with surfactant adsorption layers. The dynamic system properties depend on the mechanisms and rate of equilibrium restoration after a deformation. At small magnitudes of deformation the mechanical relaxation of an interface can be described by the complex dilational viscoelastic modulus [1,2]. For sinusoidal deformations it is deflned as the ratio of complex amplitudes of interfacial tension variation and the relative surface area variation f (I ty) = dy /din A being a function of frequency. This modulus may include... 

There are complexities. The wetting of carbon blacks is very dependent on the degree of surface oxidation Healey et al. [19] found that q mm in water varied with the fraction of hydrophilic sites as determined by water adsorption isotherms. In the case of oxides such as Ti02 and Si02, can vary considerably with pretreatment and with the specific surface area [17, 20, 21]. Morimoto and co-workers report a considerable variation in q mm of ZnO with the degree of heat treatment (see Ref. 22). 

The currently useful model for dealing with rough surfaces is that of the selfsimilar or fractal surface (see Sections VII-4C and XVI-2B). This approach has been very useful in dealing with the variation of apparent surface area with the size of adsorbate molecules used and with adsorbent particle size. All adsorbate molecules have access to a plane surface, that is, one of fractal dimension 2. For surfaces of Z> > 2, however, there will be regions accessible to small molecules... 

Surface Area. Surface area is the available area of fillers, be it on the surface or in cracks, crevices, and pores. The values obtained from different methods for measuring the surface area of a filler may vary significandy. These variations are because of the nature of the methods and in many instances yield information related to the heterogeneity of the surface. Understanding the surface area is important because many processing factors are dependent on the surface area, eg, ease of filler dispersion, rheology, and optimum filler loading. 

The micropore volume varied from -0.15 to -0.35 cmVg. No clear trend was observed with respect to the spatial variation. Data for the BET surface area are shown in Fig. 14. The surface area varied from -300 to -900 mVg, again with no clear dependence upon spatial location withm the monolith. The surface area and pore volume varied by a factor -3 withm the monolith, which had a volume of -1900 cm. In contrast, the steam activated monolith exhibited similar imcropore structure variability, but in a sample with less than one fiftieth of the volume. Pore size, pore volume and surface area data are given in Table 2 for four large monoliths activated via Oj chemisorption. The data in Table 2 are mean values from samples cored from each end of the monolith. A comparison of the data m Table 1 and 2 indicates that at bum-offs -10% comparable pore volumes and surface areas are developed for both steam activation and Oj chemisorption activation, although the process time is substantially longer in the latter case. 

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