Spherical aggregates

Whereas the surface area of a crystalline silica is in fact the external surface area, the surface area and the pore size distribution of an amorphous silica are actually determined by the dimensions of the silica spheres (primary particles) that build up the network. For non-aggregated spherical particles, this relationship is very straightforward. In this silica type, the primary particles are not clustered and Sheinfain s3 globular theory can be applied. The globular theory predicts an inverse relationship between surface area and the primary particle size by the following equation ... 

B Aggregate, spherical gravel test age, 4 days. b Aggregate, acidic crushed stone test age, 4 days. 0 Aggregate, basic crushed stone test age, 4 days. 

Aggregate sphericity is an index of how closely a particle represents a sphere and can vary between 0 for a highly nonspherical particle to 1 for a highly spherical particle. 

Figure 3.1 (Top ) Schematic view of processes controlled by curvature in endocytosis. Adapted from [2]. (Bottom ) Representative of the simplest surfactant aggregates spherical micelles v/al between 1/3 (spheres) and 1/2 (cylinders) planar bilayers (v/al = 1) inverted micelles...

In the presence of organics, aggregated spherical colloids of about 100 nm can be seen. The organics influence the precipitation of the calcite and change the shape of the crj stals, which explains the observed difference in flux. At pH 8 (see Figure 7.52B) the calcite ctystals are smaller than at pH 10 and more organics appear to be associated with the deposit. 

Figure 14.5 Structure produced by ordering of micelles I. Molecular solution. 2. Spherical micelles. 3. Aggregated spherical micelles. 4. Cylindrical micelles. 5. Hexagonal phase. 6. Disc micelles. 7. Vesicles. 8. Lamellar sheets. 9. Crystalline...

Figure 18a demonstrates the diagram of states in Nb, Oio coordinates for block copolymer with the length of pH-sensitive block Na = 50, and pH = pATa (i.e., for ah = 0.5). Solid lines indicate the binodals calculated according to (148) and (142). A smaller value of oct = 0.1 is used in Fig. 18b The diagrams localize the stability regions of three main morphologies of block copolymer aggregates spherical, S (i = 3), and cylindrical C (/ = 2) micelles, and lamellae L (i = 1). The latter can further associate due to Van der Waals forces, and precipitate from the solution.

Nodular aggregates—spherical clumps of nodules, from 400 to 1000 A in diameter... 

A similar breaking of the symmetry of the high temperature (good solvent) phase upon side-chain collapse also occurs for an even simpler kind of brush stmcture, a spherical polymer bmsh, and there it also leads to a specific form of intermolecular aggregation. Spherical polymer bmshes formed from (spherical) nanoparticles to... 

A microscopic view of the sol-gel derived alumina granules is shown in Fig. 8. The multiple granules prepared under the same experimental conditions are non-aggregated spherical particles without lumps. The particle sizes of these granules are uniform. This smooth spherical shape and narrow particle size distribution provide the necessary homogeneity of y-alumina support for catalysts or adsorbents for use in either fixed-bed, moving-bed or fluidized-bed reactors. 

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