Phase inhomogeneities

The above classification of chemical processes was based on the system s physical chemistry. A similar classification can be applied to electronic processes if we consider the effectively charged structure elements and assume that we can determine extremely small component concentrations or deviations from the stoichiometric composition. The well-known p-n junction process can serve as an example since it is a transport process (including local relaxation) in a single phase, inhomogeneous system. 

The appearance of a sharp central peak in the deuteron NMR spectrum for unaligned lyotropic liquid crystalline samples has been observed by several authors (30, 33, 34). This has been interpreted in terms of phase inhomogenities (35) or isotropic motion (36). However, recently Wennerstrom et al. showed for a lamellar amphiphile-water mesophase that this could be referred to double quantum transitions (37). It is expected that double quantum transition peaks appear in NMR spectra... 

Equilibrium measurements of the solid hydrate phase have been previously avoided due to experimental difficulties such as water occlusion, solid phase inhomogeneity, and measurements of solid phase concentrations. Instead, researchers have traditionally measured fluid phase properties (i.e., pressure, temperature, gas phase composition, and aqueous inhibitor concentrations) and predicted hydrate formation conditions of the solid phase using a modified van der Waals and Platteeuw (1959) theory, specified in Chapter 5. 

The conductivities of some ceria-containing compounds obtained from the literature have been compiled and shown as solid lines in Fig. 2.12. The main dopants for ceria belong to the alkaline earth or rare-earth metal series and the majority of doped samples exhibit conductivity values which fall into a rather limited band (gray band in Fig. 2.12), which points to a similar behaviour for all doped ceria samples. Exceptions are pure ceria and ceria doped with redox elements like Pr and Tb which give rise to electronic contribution to conductivity. An important requirement is that a homogeneous solid solution forms between the two oxides, which maintains the fluorite structure since the presence of a second phase or phase inhomogeneity due to insufficient solubility can affect ionic conductivity. The very low values of conductivity found for BaO and MgO-doped ceria were in fact attributed to the low solubility of these oxides into the lattice of When the... 

Numerous reports [53-62] regarding the synthesis of YAG have appeared in the literature, and in most cases the final product was either a mixture of various yttrium aluminate phases or stoichiometric YAG of undesirably large particle size. The phase inhomogeneity in the final product, through alkoxide processing, was caused by the formation of a Y-Al double alkoxide, which is a very stable compound and, hence, extremely resistant to hydrolysis [63]. For the Y and A1 isopropoxides, the two react to form a stable Y-Al double iso-propoxide according to the reaction... 

Figure 11. FT-IR transmission spectra demonstrating the phase inhomogeneity of BN films deposited at 17bs = 60 V. The IR beam with a diameter of about 1 mm was moved in 1 mm steps radially from the outer region towards the center of the substrate (spectra a-g). Within the lateral resolution limit of the method a sharp transition from noncubic (outer part) to cubic BN (inner part) is found.

Thus, the unstable (self-oscillating) combustion of ferrosilicon in nitrogen is accompanied by a low nitriding degree of combustion products and leads to their chemical and phase inhomogeneity. SHS process control is required to achieve the phase and chemical homogeneity of SHS products and the maximum (m = 1)... 

For a reaction in a ternary single-phase inhomogeneous metallic system with given initial and boundary conditions, it may easily be appreciated that finding a mathematical solution of... 

Another possible explanation of the same observations is based on the consideration of a two-phase inhomogeneous structure (microphase separation, no incommensurability). 

Nikolaev, A.L., Gopin, A.V., Chicherin, D.S., Bozhevol nov, V.E., Melikhov, I.V. Localization of Acoustic Energy in Gel Systems on Solid-Phase Inhomogeneities, Moscow University Chemistry Bulletin, 2008, 63(3), 167-171. 

The DOSs from these papers and that from the results of later self-consistent APW calculations by Bekenev et al (1985) differ greatly. Self-consistency appears to be very important for the correct estimation of the relative energies of p- and d-bands and results in closing the energy gap between the bands. The self-consistent partial DOSs were used by Bekenev et al in order to calculate the shape of the CrL CrX, and NK, emission spectra. As follows from Fig. 3.10, the calculations satisfactorily describe the main features of CrN spectra, except that the theoretical CrK, spectrum does not have the shoulder at — 3 eV, which is observed in the experiments and which is attributed to the phase inhomogeneity of the sample studied. 

The contribution of phase heterogeneity (in the regions of I + LC and LC + CS of the phase diagram) to the viscoplastic behavior of LC polymers thus becomes clearer. The phase inhomogeneity of the system intensities the effects... 

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