Factors influencing particle morphology

The above examples can be supplemented by several others. However, the point that emerges out of the above is that there are indeed some indications of factors influencing particle shape, but so far they are not enough to lead to an assured product batch of monomorphological nanoparticles (except the spherical morphology), at least not in a general way. The different particle shapes recorded to have been obtained in oxide and non-oxide systems through microemulsions and described below, are assembled in Fig. 5.1. 

Three factors, listed below, which might influence the morphology of composite latex particles will now be discussed. 

The morphology of zeolites can also be strongly influenced by the variation in different synthesis parameters. Aluminium content, template/silica ratio, water content, nature of cations present, alkalinity and degree of polymerization of the silica are all major factors which can influence the crystallization and hence the morphology of zeolites [5 - 7]. These particle morphological types can generally be characterized as either spherulitic (polycrystalline spherical) or lath-shaped (polyhedral) in nature. In both cases... 

When a solid has been solubilized in the liquid prior to the introduction of the compressed gas, the volumetric expansion is accompanied by a decrease of the liquid solvent strength, which causes the solid to precipitate as ultra fine particles. The physicochemical properties of the solute of interest strongly influence the choice of a solvent/antisolvent pair. The antisolvent should have appreciable mutual solubility with the solvent and should have little or no affinity for the solute. As will be seen, the solute-solvent affinity is also an effective factor that can strongly influence the morphology of the end product. 

The solvent system selected may be an important factor influencing the supersaturation profile, product yield, size, and morphology of the particles produced. Thus in the experiments with SX, methanol, acetone, and tetra-hydrofuran solvents were tested. Although all these solvents are suitable for antisolvent precipitation, methanol was selected for further studies because of its high yield ( > 95%) and suitable particle size distribution for respiratory delivery ( v < 5 pm) achieved. 

The evolution of composite latex particle morphology during onulsion polymerization, and the various parameters which influence ffiis morphology have been described in this chapter. Bodi diermodynamic and kinetic factors strongly... 

Taking into account all these factors, it has been found that the most appropriate supports for PFMFCs catalysts are carbon blacks of ca. 250 m g BFT surface area, and the most widely used is Vulcan XC-72R commercialized by Cabot. ° ° Due to the importance of the surface chemistry of these supports, and its influence in the supported active metal phase, ° ° different chemical modifications of the support have been also investigated. The chemical nature of the carbon surface produces different electronic interactions between the noble metals and the carbon support, and affects the metal particle morphology, and influences the catalytic activity. Additionally, during the last few years, new alternative materials to carbon blacks have also been used, especially on the basis of their porous structure (nanotubes, mosoporous carbons) or their microstructure (nano- and microfibers, and microspheres). 

The other factors that may influence hybrid dispersion particle morphology will be discussed in detail in Section 6.3.2 of this Chapter. 

As the form factor analysis provides detailed insight into the particle structure, one can use this information in order to adapt the polymerization conditions, as, for example, batch, semibatch synthesis, or controlled monomer feed, in order to tailor particle morphology and thus microgel properties.In addition, one can employ SANS data to investigate the influence of chemical reactivity on the microstructure by comparing, for example, different cross-linkers, initiators, or monomers. 

Rod-like morphology has also been reported for gold nanoparticles [232]. It has been shown that in partial agreement with Pileni s work discussed above, increase in water/surfactant ratio could increase the percentage of rod-like particles, though in a limited way. In addition, other factors like reactant ratio have been considered to influence the morphology. 

Within the topic catalysis, the properties associated with different morphologies, activities, and selectivities which are strongly affected by the shape and particle size, and in the case of crystalline metallic phases, and the orientation of crystal faces exhibiting differentiation, should be highlighted. The reactions that are influenced by the factors mentioned above (morphological) are known as sensitive reactions to the catalyst structure. 

Monomer compositional drifts may also occur due to preferential solution of the styrene in the mbber phase or solution of the acrylonitrile in the aqueous phase (72). In emulsion systems, mbber particle size may also influence graft stmcture so that the number of graft chains per unit of mbber particle surface area tends to remain constant (73). Factors affecting the distribution (eg, core-sheU vs "wart-like" morphologies) of the grafted copolymer on the mbber particle surface have been studied in emulsion systems (74). Effects due to preferential solvation of the initiator by the polybutadiene have been described (75,76). 

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