Crystal particle

Impurity-produced plasmas in semiconductors do not have to be compensated by charges of the opposite sign. These plasmas can be produced by introduction of either electron donors or electron scavengers, ie, hole producers, into semiconductor lattices. Thek densities range from a lower limit set by the abihty to produce pure crystals particles/cm ) to values in excess of 10 particles/cm. Plasmas in semiconductors generally are dilute, so that... 

Clouds cover roughly two-thirds of our earth s surface and play an important role in influencing global climate by affecting the radiation budget. Cirrus clouds are one example of a cloud type whose optical properties are not accurately known. Cirrus clouds form in the upper troposphere and are composed almost exclusively of non-spherical ice crystal particles. The impact of cloud coverage on dispersion of pollution in the atmosphere is an area of great concern and intensive study. 

To fully grasp the main feature of the gas-liquid precipitation phenomena, however, it is not enough just to account for the formation of crystal particles, evaluation of the Hatta number is also essential. 

The formation mechanism is illustrated in Fig. 5. CNT film has also been found to grow epitaxially on the surface of a (3-SiC crystal particle [29], The present method should prove to be applicable to flat panel displays or to electronic devices utilising MWCNTs,... 

As illustrated by Eig. 4.13, an electron microscope offers additional possibilities for analyzing the sample. Diffraction patterns (spots from a single-crystal particle and rings from a collection of randomly oriented particles) enable one to identify crystallographic phases as in XRD. Emitted X-rays are characteristic for an element and allow for a determination of the chemical composition of a selected part of the sample. This technique is referred to as energy-dispersive X-ray analysis (EDX). 

Depolymerization, e.g., polyethylene terephthalate and cellulose hydrolysis Hydrothermal oxidation of organic wastes in water Crystallization, particle formation, and coatings Antisolvent crystallization, rapid expansion from supercritical fluid solution (RESS)... 

In summary, the movement of a high-energy electron in a solid may be described by a set of three Equations (1), (4) and (6). From these equations we may conclude that for high-energy electron diffraction the problem of multiple elastic and inelastic scattering by a solid is entirely determined by two functions, i.e. (1) the Coulomb interaction potential averaged over the motion of the crystal particles (V(r)> and (2) the mixed dynamic form factor S(r, r, E) of inelastic excitations of the solid. 

Salt glands of plants from Atriplex genus contain inclusions in the form of crystals of siliceous or sulphate salts of calcium and magnesium (Fahn, 1979). Usually the crystal particles also include phenols (see Chapter 7). The crystals are seen as dark dense spots within the structures on OCM images of the optical slices from the gland (Fig. 4). Profiles of signal intensity along... 

Plastic deformation, unlike elastic deformation, is not accurately predicted from atomic or molecular properties. Rather, plastic deformation is determined by the presence of crystal defects such as dislocations and grain boundaries. While it is not the purpose of this chapter to discuss this in detail, it is important to realize that dislocations and grain boundaries are influenced by things such as the rate of crystallization, particle size, the presence of impurities, and the type of recrystallization solvent used. Processes that influence these can be expected to influence the plastic deformation properties of materials, and hence the processing properties. 

Adsorptive separation is a powerful technology in industrial separations. In many cases, adsorption is the only technology available to separate products from industrial process streams when other conventional separation tools fail, such as distillation, absorption, membrane, crystallization and extraction. Itis also demonstrated that zeolites are unique as an adsorbent in adsorptive separation processes. This is because zeolites are crystalline soUds that are composed of many framework structures. Zeolites also have uniform pore openings, ion exchange abiUty and a variety of chemical compositions and crystal particle sizes. With the features mentioned, the degree of zeoUte adsorption is almost infinite. It is also noted that because of the unique characteristics of zeoHtes, such as various pore openings, chemical compositions and structures, many adsorption mechanisms are in existence and are practiced commercially. 

Ammonium nitrate contains a relatively high concentration of oxidizer fragments, as shown in Table 2.6. In order to maximize the binder mixed with AN is GAP. The maximum of 238 s and the maximum Tjof 2400 K are obtained at (AN) = 0.85, as shown in Fig. 4.16. However, since AN crystal particles are not wholly compatible with GAP, the practical (AN) is less than 0.8, at which Isp drops to 225 s and drops to 2220 K. 

It Is Important to use highly accurate surface area values of a crystal particle In growth rate equations, when the equations Include a term of the surface area. In practice, however. It Is difficult to measure the surface area unless the crystal possesses a simple geometry (e.g., sphere, cube, octahedron, etc.), or unless the B.E.T. method of measuring surface area Is applied. Therefore, a characteristic diameter Is usually defined, and the area calculated from the diameter Is used. 

Single crystal particles and multiply twinned particles (MTP)... 

Metal phosphates can be prepared by wet and dry methods. The homogeneous precipitation in aqueous systems is often employed to obtain uniformly sized and well-crystallized particles. The solid reactions can be used for preparation of some metal phosphates however, the particles with controlled morphology are difficult to synthesize. Moreover, the solid reaction consumes more energy than the reaction in aqueous system, except the hydrothermal reaction at elevated temperature. Recently the preparation from aqueous solution at low temperature received attention in view of saving energy and as an application for a wide variety of substances. Therefore the preparation of metal phosphate particles by the precipitation method is described next. Although phosphates include ortho-, pyro-, and polyphosphates, only orthophosphates are dealt with here. 

Crystallizing particles arriving at the surface will diffuse onto the surface (surface diffusion). As this occurs, some may return to the ambient phase, while some will be caught at kinks or steps (see Section 3.6) on the surface and will be incorporated into the crystal. When these particles are incorporated into the crystal, the solvent component will be dissociated. This process is called desolvation. In solution growth, this process will determine the growth rate. At certain points in these processes, it is necessary to overcome the energy barriers required to climb the respective steps (Fig. 3.5). 

Figure 5.16. Difference in step patterns for the case in which (a) foreign particles or the same crystal particles with different orientation precipitate on a growing surface, and (b) in which the same crystal particles precipitate in the same orientation. The shaded side indicates the higher side of the steps, (c) Actual example of cases shown in (a) and (b), observed on a (0001) face of hematite.

On the supposition that the total number of unit cells keeps invariable and no aluminum atoms are lost during the boronation, the composition of unit cell and the population of vacancies can be estimated as listed in composition of unit cell (I) in Table 2. It can be seen that the vacancies occupy about 30-50% of total T sites after the boronation. However, it should be noted that the population of vacancies thus obtained by chemical analysis is only a bulk average result. The composition on the surface of crystallites is actually different from that in the bulk because the dissolution of silicon starts first from the outer surface, so that the vacancies on the surface are much more than those in the interior of crystallites. Such a large number of vacancies on the surface will result in corrosion and dissolution of the surface parts of crystal particles. Therefore, the number of unit cells in the sample after the boronation is actually less than that before the boronation, whereas boron atoms in each unit cell should be more than those shown in composition of unit cell (1) in Table 2. On the other hand, if all the 64 T sites are occupied by silicon and trivalent atoms, we can give another set of compositions as shown in composition of unit cell (II) in Table 2. The real composition of a unit cell should be between these two sets of compositions, that is, the 64 T sites are neither occupied completely nor vacated so severely that the collapse of the framework occurs. It can also be seen that the introduction of boron atoms is so limited that there are no more than 1.5 atoms per unit cell even though the repeated boronation is performed. 

The porous volumes measured by N2 adsorption are listed in Table 3. After the boronation, the total porous volumes (Vt) of the samples increase, corresponding to the increase of benzene adsorption capacity mentioned above. This should be resulted from the following aspects (1) The average mass of zeolite crystallite decrease and the number of crystal particles in unit weight of sample increases after the boronation owing to a limited introduction of trivalent atoms and Na+cations as counterions, as well as a severe dissolution of silicon. Thus, the total porous volume (mL/g) and the adsorption capacity increase. (2) The transformation of pore size occurs during the boronation. As shown in Table 3, the mesoporous volumes increase and the microporous volumes decrease after the boronation, meaning that some micropores are developed into mesopores due to the removal of silicon from the framework. This is also one of the important reasons why the total porous volumes as well as the adsorption capacities increase after the boronation. 

The SEM pictures of samples are shown in Fig.5. They provide a direct evidence for the corrosion on the outer surface of crystallites. For the parent sample, the average size of the crystal particles is 200 nm (Fig.5a). After the boronation, the average particle size decreases since the corrosion and dissolution of the outer layer of particles occurs. In the case of [B]-Naft-2 with a more severe dissolution, the average particle size is only about half as large as that of the parent sample (see Fig.5b). 

From all the above information, we can describe the important modification during the boronation of zeolites (3 as follows very limited boron atoms are inserted into the (3 framework by treating the sample with an alkaline solution containing boron species. Accompanied by this insertion, a considerable amount of silicon atoms are extracted from the lattice, resulting in the micropores in crystallites are enlarged into the mesopores and the smaller mesopores are developed into larger intracrystalline mesopores. Meanwhile, the corrosion of outer layer of crystallite makes the size of crystal particle reduce. 

X-Ray diffraction showed that the molybdenum disulfide powder used in this experiment has a hexagonal layer structure. A remarkable feature of such layer compounds is that the powder is composed of small single crystal particles. In view of these facts, an interesting question arises as to whether... 

An observed spectrum is typically found to be derived from the presence of several different adsorbed species. These arise from a plurality of different adsorption sites that can occur on particles of a given metal. Even a well crystallized particle could, for example, present sites associated with different types of facets, e.g., (Ill), (100), or (110), and their various arrays of metal atoms (see Fig. 1 in Section IV.A.l). 

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