Crystalline particle size distribution, characteristic

Evaluation of the morphology of a pharmaceutical solid is of extreme importance, since this property exerts a significant influence over the bulk powder properties of the material. In addition to providing insights into the micromeritic properties of the solid, microscopy can also be used to develop preliminary estimations of the particle-size distribution. A determination can be easily made regarding the relative crystallinity of the material, and it is often possible to deduce crystallographic information as well. Unknown particulates can often be identified solely on the basis of their microscopic characteristics, although it is useful to obtain confirmatory support for these conclusions with the aid of microscopically assisted techniques. 

An example of a gas-soHd reactor in which both phases are mixed is crystallization, where a supersaturated Hquid crystallizes onto growing solid nuclei. The crystal area and the mass transfer characteristics now depend on crystal size (discussed in Chapter 9), and the objective is usually to control conditions in such a way as to obtain soHd particles of a particular size, size distribution, crystallinity, solvent incorporation, etc. 

Depending on conditions during processing and storage, a crystalline microstructure develops in many foods that can significantly impact food propaties. Some important characteristics of the crystalline dispersion include the crystalline phase volume, mean size and size distribution of crystals, shape and surface characteristics of the particles, polymorphic characteristics, and any network structure that forms between... 

Pore characteristics, particle-density, -shape, -size and -size distribution, purity, crystalline phase, modification and attrition resistance of the alumina support (Eli et al., 2000 Rytter et al., 2002a). 

Equation (3.106) allows to calculate /(co) for paramagnetic centers with axial symmetry crystalline field constant D being proportional to P or P. This includes the materials with phase transitions of the first or the second order (see Eq. 3.103) and for any type of nanoparticles size distribution function /(/ ). The EPR spectra for all above cases have been calculated in Ref. [101], All the spectfa have the same characteristic feature at particles size decrease. Namely, it is the broadening of the axial symmetry spectral lines and the increase of intensity of cubic spectral lines. Figure 3.31 illustrates this EPR spectra transformation under the influence of size distribution function parameters Rq,o) and critical radius Rc. 

SevCTal types of reactions may be employed in hydrothermal synthesis (69). A common feature is that precipitation of the product generally involves forced hydrolysis undCT elevated temperature and pressure. TTie powders have several desirable characteristics, but they also suffer from a few disadvantages so that their benefits are normally not fully realized. In hydrothermal synthesis, the crystalline phase is commonly produced directly so that a calcination step is not required, as in the case of several other synthesis routes. The powders also have the characteristics of very fine size (10-100 nm), narrow size distribution, singlecrystal particles, high purity, and good chemical homogeneity. 

Structural characteristics include particle size, aspect ratio, crystallinity, bulk chemistry, defect structures, surface chemistry, surface structure and, in the case of its electrical behaviour, the density of electronic states in the interior and at the surface. Second, as introduced above, interactions between the nanoparticles and their environment may lead to a perturbation of the local structure or composition of the surrounding matrix material (Fig. 9.1c). Finally, the range of aggregation states of the primary nanoparticles needs to be considered, together with their distribution throughout the bulk (Fig. 9.1a). 

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