Aggregation crystal

Fig. 2.3 Schematic diagram illustrating possible steps in the complex-decomposition mechanism. The complex (Cd—S—L, where L is a ligand or part of the S-forming species) decomposes to CdS on the substrate (possibly catalyzed by the substrate) and, to a greater or lesser extent, also homogeneously in the solution (A, B). The CdS nuclei formed grow by adsorption and decomposition of more complex species (C) until a film of aggregated crystals is formed (D) in the same manner as for the previous two mechanisms.

The flocculated fat globules of whipped cream contain fewer contact points, and the foam is therefore not as stiff as in toppings in which the aggregated crystal platelets have a large surface area, many contact points and thus increased stiffness. This means that an acceptable topping foam may be formed at a much lower fat content than is the case with liquid whipping creams. 

This single covalent bond holds the atoms together into diatomic mole cules, which are present in the elementary halogens in all states of aggregation—crystal, liquid, and gas. 

Crystal fibers are longitudinal rows of superimposed parenchyma cells each of which contains a single monoclinic prism or rosette aggregate. Crystal fibers are found adjacent to sclerenchyma fibers such as bast or woody fibers. 

When a methylene group spacer is inserted between the ortho heteroatom and the carbanionic center, the coordination geometry of the anionic center is no longer restricted to be planar for intramolecular chelation to occur. Hence, o-(dimethylaminomethyl)phenyllithium (126) crystallizes from an ether/hex-ane solution as the internal-chelated tetramer (127). This structure is analogous to tetrameric phenylli-thium (119). When an additional dimethylaminomethyl group is substituted at the ortho position as in 2,3,5,6-tetrakis(dimethylaminomethyl)phenyllithium, the aggregate crystallizes as the dimer (128). Hie lithium atoms in both (127) and (128) are coordinated to four other nonlithium atoms this coordination can only be achieved by dimerization and tetramerization respectively. 

Rgure 8.6 Representation of the variety of polymer morphologies in solution and in the gel (or microgel) or solid states. In solution the conformation of the polymer depends on the nature of polymer-solvent interactions and whether or not the polymer chains associate to form micellar aggregates. Crystals of polymer and microcrystals can be prepared, and gels can be formed from covalently crosslinked or polymer chains associated by hydrogen bonding or hydrophobic interactions. Listed are the forms in which most polymers can be fabricated membranes, fibres, composites, matrices microspheres and microcapsules can also feature, as discussed later in this chapter. 

Figure 22. Transmission electron microscope image of an single anatase crystal formed by oriented aggregation. Crystal margins are marked with arrows tips a subset of the particles that formed the aggregate are numbered. Dislocation positions are indicated by arrows (view at low angle). The diagram on the right illustrates formation of an edge dislocation at an interface where one particle (black) has a surface step (Perm and Banfield, impublished see Perm and Banfield 1998).

Peptide-poly(ethylene glycol) (PEG) block copolymers are ofparticiflar interest, both from a structural and a functional point of view. Poly(ethylene glycol) is also often referred to as poly(ethylene oxide) (PEG). Throughout this article, however, this polyether will be referred to as PEG. In contrast to the hybrid block copolymers discussed in the previous paragraphs, which were based on amorphous synthetic polymers, PEG is a semi-crystalline polymer. In addition to microphase separation and the tendency of the peptide blocks towards aggregation, crystallization of PEG introduces an additional factor that can influence the structure formation of these hybrid block copolymers, furthermore, PEG is an FDA approved biocompatible polymer, which makes peptide-PEG hybrid block copolymers potentially interesting materials for biomedical applications. 

Shape Bead, flat sheet or hollow fiber membrane, amorphous aggregate Crystal Ease of filtration, Control of diffusion path length and flow properties Simple preparation... 

Higher amounts of zirconium (1.2 Zr/unit cell) could be incorporated in the MEL structure using Zr(IV) acetylacetonate as zirconium source without any precipitation during the gel preparation while ZrCU source could not be used beyond x > 0.01 as it yields material with low crystallinity (XRD), aggregated crystals (SEM) and non- homogenous gel during the synthesis. A higher catechol formation in Zr-Sil-2 (B) samples may be due to the surface acid sites. 

Homogeneous coatings of zeolite ZSM-5 were prepared by the seed film method on porous ceramic foams and on alumina spheres. The zeolite was predominately present in the form of a film on the support surface rather than as aggregated crystals on the surface. The results from gas adsorption and SEM analysis indicated that the entire surface of the foams was successfully covered with a 450 nm film. A 500 nm film was formed on the external surface and also in pores close to the external surface of the spheres. Zeolite was not formed on the internal surface of the alumina spheres. Aluminum leaching from the foams was observed but did not seem to have any detrimental effects on the substrates. 

Ultramicroscopic and x-ray studies show that oxides obtained from carbonates and oxalates at low decomposition temperatures are pseudomorphous with the crystals of the starting material [10, 12]. Since the molar volume of the new substance is as a rule considerably smaller than that of the starting material, the particles of the product are usually very porous, that is, provided the reduced decomposition temperature T/T , < 1/3 (compare p. 1611). If the decomposition temperature is higher, aggregate crystallization can be expected to an increasing degree [19], except when the starting substance (which must in this case be a uniform fine powder) is heated for such a short time that only the desired... 

Ethyl ester nitrate 95 Aggregated crystals (EtOH) 53... 

In addition to molecularly distributed compounds, the material can also be encapsulated as aggregate, crystal, etc., as is the case for the encapsulation of pigments and, for thermally labile azo-components, photoinitiators, and highly fluorescent quantum dots in polymeric nanoparticles by using the miniemulsion process. 

Figure 5.7 Sheaf-like lamellar aggregates crystallized from the melt in a blend of linear and low-density polyethylene at 125...

Growth and Formation of Diffusion-Limited-Aggregation Crystal Pattern... 

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