Structure of interfaces

A new parepisteme was under way its early stages were mapped in a classic text by McLean (1957), who worked in Rosenhain s old laboratory. Today, the atomic structure of interfaces, grain boundaries in particular, has become a virtual scientific industry a recent multiauthor book of 715 pages (Wolf and Yip 1992) surveys the present state, while an even more recent equally substantial book by two well-known authors provides a thorough account of all kinds of interfaces (Sutton and Balluffi 1995). In a paper published at about the same time, Balluffi... 

When speculating about the hypothetical structure of interfaces with minimal free energy, the diffuse interfaces formed by the properly grafted water-soluble... 

Conjugated Polymer Surfaces and Interfaces Electronic and Chemical Structure of Interfaces for Polymer Light Emitting Devices W.R. Salaneck, S. Stafstrom, J.L. Bredas Cambridge University Press, 169 pp. ISBN 0521544106... 

COM interfaces are defined in an interface description language called IDL.6 These interfaces can be compiled to produce type libraries—the runtime representation of the structure of interfaces and methods—and to produce appropriate proxy, stub, and marshaling code for the case of remote object references. 

Salaneck WR, Staftstrom S, Bredas J-L (1996) Conjugated polymer surfaces and interfaces. Electronic and chemical structure of interfaces for polymer light emitting devices. Cambridge University Press, Cambridge... 

In Chapter 3 we described the structure of interfaces and in the previous section we described their thermodynamic properties. In the following, we will discuss the kinetics of interfaces. However, kinetic effects due to interface energies (eg., Ostwald ripening) are treated in Chapter 12 on phase transformations, whereas Chapter 14 is devoted to the influence of elasticity on the kinetics. As such, we will concentrate here on the basic kinetics of interface reactions. Stationary, immobile phase boundaries in solids (e.g., A/B, A/AX, AX/AY, etc.) may be compared to two-phase heterogeneous systems of which one phase is a liquid. Their kinetics have been extensively studied in electrochemistry and we shall make use of the concepts developed in that subject. For electrodes in dynamic equilibrium, we know that charged atomic particles are continuously crossing the boundary in both directions. This transfer is thermally activated. At the stationary equilibrium boundary, the opposite fluxes of both electrons and ions are necessarily equal. Figure 10-7 shows this situation schematically for two different crystals bounded by the (b) interface. This was already presented in Section 4.5 and we continue that preliminary discussion now in more detail. 

Fig. 5.3 Structure of interface at equilibrium. IHP is the inner Helmholz plane through the contact adsorbed, nonsolvated anions and OHP is the outer Helmholz plane...

Finnis, M.W. and Ruhle, M., (1993), Structures of interfaces in crystalline solids , in Cahn, R.W., Haasen, P. and Kramer, E.J., (eds), Materials Science and Technology A Comprehensive Treatment, Volume 1 Structure of Solids, New York, VCH Publishers, 533-605. 

Spectroscopic investigations were directed for the first time measurements of CfioFWS in order to elucidate a structure of hydrated particles in the colloid and a structure of interface layer of water molecules surrounded them. The results obtained in these experiments proved to be enough unexpected and unusual, and served as a spur to present investigations and present paper. 

Electronic and chemical structure of interfaces for polymer light emitting devices... 

In order make an effort to bring the polyimide-metal adhesion problem to an even more fundamental level, we have previously proposed that model molecules, chosen as representative of selected parts of the polyimide repeat unit, may be used to predict the chemical and electronic structure of interfaces between polyimides and metals (12). Relatively small model molecules can be vapor deposited in situ under UHV conditions to form monolayer films upon atomically clean metal substrates, and detailed information about chemical bonding, charge transfer and molecular orientation can be determined, and even site-specific interactions may be recognized. The result of such studies can also be expected to be relevant in comparison with the results of studies of metal-polymer interfaces. Another very important advantage with this model molecule approach is the possibility to apply a more reliable theoretical analysis to the data, which is very difficult when studying complex polymers such as polyimide. 

The depth of introduction can be varied by technical tools as well. Transmission techniques can be applied for bulk analysis, while reflection techniques are appropriate to the study of the interfaces. Transmission and reflection techniques can be applied using a wide range of electromagnetic radiation, from infrared to x-ray ranges. Moreover, particle radiation (e.g., the neutron scattering technique) can also be used for the study of the structure of interfaces. 

The work under SMP (SMP Report) comprises six interrelated chapters (tasks) aimed at attaining an ultimate goal - identifying top-priority measures (projects). General structure of interfaces between the tasks solved at the initial SMP development phase and their representation in the SMP final report is demonstrated in Fig. 3. 

Structure of interfaces from uniformity of the chemical potential. J. Stat. Phys. 19, 563-574 (1978). 

Fundamental adhesion is connected with the nature of the bonds producing cohesion between two media. These bonds may be classified into two categories, namely strong bonds (polar, covalent and metallic bonds) and secondary bonds (hydrogenous and Van der Waals bonds). Different atomic or molecular models have been proposed to describe the electronic structure of interfaces. None however, is sufficient for calculating the intensity of adhesion forces for systems of practical interest. 

In addition to the simulation results on the structure of interfaces, reported so far in FICS, we shall now give some outcomes on surface and interfacial tensions. In so doing, we msike the conscious decision to omit most of the technical details (numbers of molecules and time steps, interaction functions, accounting for internal degrees of freedom etc.) although the results depend, sometimes critically, on these. Therefore, our examples merely serve as illustrations of the achievements. 

There are similar issues when considering lipolysis of emulsions. Armand et ah (1992) found that pancreatic lipase activity was increased with decreasing emulsion size. However, modification of the interface of emulsions by heat treatment of the encapsulant (a mixture of caseinate and modified starch) prior to emulsion formation altered the rate of lipolysis of emulsions in model systems (Chung et al., 2008). The structuring of interfaces for the target delivery of oils and oil-soluble bioactives is currently an active field of research (Singh et ah, 2009). 

I. SURFACE PHENOMENA AND THE STRUCTURE OF INTERFACES IN ONE-COMPONENT SYSTEMS... 

The foregoing discussion deals with interfaces between neat liquids, whereas the structure of interfaces between electrolyte solutions has been a topic of much debate over the past three decades [3, 5, 13]. The presence of electrolytes allows a variable potential to be imposed on the interface, via either the common-ion or external potentiostatic approach (see Section I). An important parameter arises for the electrolyte case, namely, what is the potential distribution at the interface between the two electrolyte phases The excess charge present on either side of the interface can be probed directly via macroscopic measurements of interfacial tension or capacitance and can thereby be used to infer structural information, albeit lacking in molecular detail. The developments along these lines up to the late 1980s/early 1990s have been reviewed [3, 5, 13, 49] hence only a brief outline of the bulk approaches to this problem will be presented here. 

Bozano, L.D., Kean, B. W., Deline V.R. et al. 2004. Appl. Phys. Lett. 84 607. Schottky, W., Stormer, R., and Waibel, F. 1931. Z. Hoch Frequentztechnik 37 162. Salaneck, W.R., Stafstrdm, S., and Br6das J.L. 1996. Conjugated Polymer Surfaces and Interfaces Electronic and Chemical Structure of Interfaces for Polymer Light Emitting Devices. Cambridge, U.K. Cambridge University Press. 

The formation and structure of interfaces prepared by deposition of metals onto fully cured polymers is strongly affected by the extent to which tnetal diffusion takes place during metallization. Very reactive metals, which appear to be practically immobile, form relatively sharp boundaries, and thin films in the monolayer range act as very effective diffosion barriers. In contrast, interfaces with noble metals can be much more spread-out, particularly when the metal is deposited at elevated temperatures and low rates. As mentioned earlier, pronounced diffusion and, at sufficiently high metal concentrations, formation of metal clusters inside the polymer may take place under these conditions. 

A. B. EUis, Luminescent Properties of Semiconductor Electrodes, in Chemistry and Structure of Interfaces, New Laser and Optical Techniques, Chapter 6 (Eds. R. B. Hall, A. B. Ellis), VCH, Deerfield Beach (FL), 1986. 

In principle matrix methods analogous to the ones discussed in the section about neutron reflectivity can be applied to calculate ellipsometric angles for an arbitrary refractive index profile (Lekner 1987) and analytical approximations have also been developed (Charmet and de Gennes 1983). In practice the use of ellipsometry to obtain fine details of the structure of interfaces at the level of tens of angstrom units is likely to be difficult and to require extreme care. 

Up to now we have only discussed the structure of interfaces that have reached equilibrium. However, in many processes only a finite amount of time is available for an interface to be formed. For example, when a pair of polymers is coextruded, the time available for the interface to develop is limited to the time at the process temperature. Alternatively, if one polymer is applied as a solution to coat a second pol)mier, then molecular motion of the polymers near the interface will often only be possible before all the solvent has evaporated. This question of kinetics becomes particularly important when we come to consider interfaces between miscible polymers here there is no equilibrium interface width at aU and the width of the interface that is achieved in practice... 

Topics covered include the nature and properties of the surface of a polymer melt, the structure of interfaces between different polymers and between pol5miers and non-polymers, adsorption from polymer solutions, the molecular basis of adhesion and the properties of polymers at liquid surfaces. Emphasis is placed on the common physical principles underlying this wide range of situations. Statistical mechanics based models of the behaviour of polymers near interfaces are introduced, with the emphasis on theory that is tractable and applicable to experimental situations. Experimental techniques for studying polymer surfaces and interfaces are reviewed and compared. 

The interfaces may be regarded as compositionally modulated disordered R-T alloys because X-ray diffraction shows an amorphous structure in the interface region. In the next subsection a brief overview of the interactions and structures of R and R-T alloys is given, on the basis of which the magnetic structure of interfaces and the origin of PMA may be well understood. 

The development of models for electron transfer, nucleation and growth of new phases and the structure of interfaces. 

Examples of controlled structuring of interfaces on the sub-micrometer scale... 

Mesoporous materials as the catalyst have good application prospects in the important multiphase reaction. The transport of media in the mesoporous materials is different from that in macro the complex structure of interface affects the reaction and transport, which makes the transport of the same importance as the reaction. The activity of catalyst could be improved by mesoporous Ti02- But various crystal facets make the recognizing of surface property difficult. The experimental phenomena are due to both complex structures and interactions in varied scales. It is necessary to care about not only catalysis mechanism but also transport for the design of catalyst with nano-/micro-/mesopore structures. 

Bass L (1964) Electrical structures of interfaces in steady electrolysis. Trans Faraday Soc 60 1656-1663... 

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