Multicomponent films

Numerous investigators have attempted to control the precursor structure and related solution chemistry effects with varying degrees of success, to influence subsequent processing behavior, such as crystallization tempera-ture.40-42,78,109 110 Particular attention has been given to precursor characteristics such as structural similarity to the desired product and the chemical homogeneity of the precursor species. For multicomponent films, this latter factor is believed to influence the interdiffusional distances associated with the formation of complex crystal structures, such as perovskite compounds. Synthetic approaches have been geared toward the preparation of multimetal species with cation stoichiometry identical to that of the desired crystalline phase.40 42 83 84... 

Chemical Equilibrium. Although CVD is a nonequilibrium process controlled by chemical kinetics and transport phenomena, equilibrium analysis is usefiil in understanding the CVD process. The chemical reactions and phase equilibria determine the feasibility of a particular process and the final state attainable. Equilibrium computations with intentionally limited reactants can provide insights into reaction mechanisms, and equilibrium analysis can be used also to estimate the defect concentrations in the solid phase and the composition of multicomponent films. 

Solid-Phase Chemical Equilibrium. For the growth of multicomponent films, the solid film composition must be predicted from the gas-phase composition. In general, this prediction requires detailed information about transport rates and surface incorporation rates of individual species, but the necessary kinetics data are rarely available. On the other hand, the equilibrium analysis only requires thermodynamic data (e.g., phase equilibrium data), which often are available from liquid-phase-epitaxy studies, as discussed by Anderson in Chapter 3. 

DeLancey GB. Multicomponent film-penetration theory with linearized kinetics— I. Linearization theory and flux expression. Chem Eng Sci 1974 29 2315-2323. 

Complete monolayers adsorbed on surfaces can also be observed by STM.139 The separation of monolayer components in self-assembled monolayers on gold was unknown and unexpected before multicomponent films were examined using STM.140 Having the ability to resolve components with molecular resolution,107 this field has since advanced rapidly to exploit intermolecular interactions to produce desired patterns.141 Such advances in other important materials could easily be driven by this ability to observe their structures and functions with atomic resolution. Other environments—liquid, gas, elevated and reduced temperature—... 

Before and after the works described above, contributions to the design and fabrication of similar multicomponent films or gels of cholesteric character, mainly based on HPC, EC, or their derivatives were also made [202, 219-224], Some of these [219,220,224] dealt with shear-deformed network systems preserving a unique banded structure, so that the disappearance and recovery of the optical anisotropy could be controlled thermo-reversibly. Special mention should be made of the successful preparation of two novel classes of solid materials maintaining cholesteric liquid-crystalline order. One consists of essentially pure cellulose only, and the other is a ceramic silica with an imprint of cellulosic chiral mesomorphy. 

Synthesis of Catalysts in Multicomponent Films Containing Magnesium... 

Pure lipids can be combined with hydrocolloids such as proteins, starches or celluloses and their derivatives, either by incorporating the lipids in the hydrocolloid film-forming solution (emulsion technique) or by depositing the lipid layer onto the surface of the preformed hydrocolloid film to obtain a bilayer (Fennema and Kamper 1986 Krochta and De Mulder Johnston 1997). Multicomponent films have been extensively reviewed by Wu et al. (2002). The addition of nonlipid compounds (hydrocolloids, sugar solids, etc.) as dispersed components in fat materials permits forming fat dispersions (e.g., chocolate. Figure 23.2). 

The present paper is aimed to construct and characterize the lipid multicomponent films onto a solid surface by a Langmuir-Blodgett (LB) technology. The goal of the work was to compare the interaction of cholesterol or quercetin-3-O-palmitate (Q3P) with membrane lipids at different alcohol concentrations to prove lateral domains formation as a result of molecular association and to understand preferable cholesterol affinity. 

The starting point for the ideal gas multicomponent film model are the Maxwell-Stefan diffusion equations, written for the y phase, here taken to be gaseous... 

MULTICOMPONENT FILM MODEL FOR MASS TRANSFER IN NONIDEAL FLUID SYSTEMS... 

In considering very many condenser simulations (not just those reviewed here) we have yet to find an application where the differences between any of the multicomponent film models that account for interaction effects (Krishna-Standart, 1976 Toor-Stewart-Prober, 1964 Krishna, 1979a-d Taylor-Smith, 1982) are significant. There is also very little difference between the turbulent eddy diffusivity model and the film models that use the Chilton-Colburn analogy (Taylor et al., 1986). This result is important because it indicates that the Chilton-Colburn analogy, widely used in design calculations, is unlikely to lead to large... 

A number of investigators used the wetted-wall column data of Modine to test multicomponent mass transfer models (Krishna, 1979, 1981 Furno et al., 1986 Bandrowski and Kubaczka, 1991). Krishna (1979b, 1981a) tested the Krishna-Standart (1976) multicomponent film model and also the linearized theory of Toor (1964) and Stewart and Prober (1964). Furno et al. (1986) used the same data to evaluate the turbulent eddy diffusion model of Chapter 10 (see Example 11.5.3) as well as the explicit methods of Section 8.5. Bandrowski and Kubaczka (1991) evaluated a more complicated method based on the development in Section 8.3.5. The results shown here are from Furno et al. (1986). 

Figure 15.22 provides a comparison between the mass transfer rates measured by Modine (1963) and the rates predicted using the different classes of model for the vapor-phase mass transfer process methods based on the multicomponent film model (all of... 

Burghardt, A., On the Solutions of Maxwell-Stefan Equations for Multicomponent Film Model, Chem. Eng. Sci., 39, 447-453 (1984). 

Krishna, R. and Standart, G. L., A Multicomponent Film Model Incorporating an Exact Matrix Method of Solution to the Maxwell-Stefan Equations, AIChE J, 22, 383-389 (1976a). 

In the five chapters that make up Part II (Chapters 7-11) we consider the estimation of rates of mass and energy transport in multicomponent systems. Multicomponent mass transfer coefficients are defined in Chapter 1, Chapter 8 develops the multicomponent film model, Chapter 9 describes unsteady-state diffusion models, and Chapter 10 considers models based on turbulent eddy diffusion. Chapter 11 shows how the additional complication of simultaneous mass and energy transfer may be handled. 

Multicomponent films were studied in [2963], and multilayer membranes in [279,2964-2967]. The polymeric membranes studied in [2968] were modified by post-treatment. Also, a-alumina identical to the material in Membralox membrane from SCT, studied in [1851], probably underwent surface treatment. 

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