Interfaces in solids

Franco T, HoshiarDin Z, Szabo P, Lang M, and Schiller G. Plasma sprayed diffusion barrier layers based on doped perovskite-type LaCr03 at substrate-anode interface in solid oxide fuel cells. J. Fuel Cell Sci. Technol. 2007 4 406-412. 

In industrial PET synthesis, two or three phases are involved in every reaction step and mass transport within and between the phases plays a dominant role. The solubility of TPA in the complex mixture within the esterification reactor is critical. Esterification and melt-phase polycondensation take place in the liquid phase and volatile by-products have to be transferred to the gas phase. The effective removal of the volatile by-products from the reaction zone is essential to ensure high reaction rates and low concentrations of undesirable side products. This process includes diffusion of molecules through the bulk phase, as well as mass transfer through the liquid/gas interface. In solid-state polycondensation (SSP), the volatile by-products diffuse through the solid and traverse the solid/gas interface. The situation is further complicated by the co-existence of amorphous and crystalline phases within the solid particles. 

This section is devoted to the basic kinetics of interfaces in solids. In Chapter 10 we shall work out some ideas in more detail and introduce atomic models for the determination of kinetic parameters. 

Yasuda, I. and Hishinuma, M., Electrical conductivity and chemical stability of calcium chromate hydroxyl apatite, Cas(Cr04)30H, and problems caused by the apatite formation at the electrode/separator interface in solid oxide fuel cells, Solid State Ionics 80, 1995, 141. 

The electrical potentials cause the levels (fJ°) to bend in the space charge zone and to shift in the core in order to satisfy that fi = const. For the sake of simplicity the electrical bulk potential ( ) is set to zero. The index c designates die core region.145 (Reprinted from J. Jamnik, J. Maier, S. Pejovnik, Interfaces in solid ionic conductors Equilibrium and small signal picture. Solid State Ionics, IS, 51-58. Copyright 1995 with permission from Elsevier.)... 

The oxygen reduction reaction (ORR) at the cathode of an electrochemical cell involves the transfer of four electrons from the cathode to an O2 molecule followed by removal of the reduced product from the interface. Reduction of an O2 molecule to water or to hydroxyl anions at an electrode/aqueous electrolyte interface is to be distinguished from reduction of O2 to 202- at the surface of an oxide or at an electrode/solid electrolyte interface in solid-state electrochemistry. In the latter case, the ORR is generally different at the surface of a noble metal like Pt from that at the surface of a metallic oxide. 

The factors governing the slow thermal decompositions of inorganic azides have been discussed by Fox and Hutchinson [18]. They draw attention to the interest shown in early studies for fitting of kinetic results to rate equations based on nucleation and growth models. Support of kinetic interpretations by microscopic observations (e g., [21]), contributed significantly towards establishment of the role of the active, advancing interface in solid state reactions. The kinetic characteristics of some of the metal azides are summarized in Table 11.1. 

Materials Interfaces edited by D. Wolf and S. Yip, Chapman Hall, London England, 1992. This book is a compilation consisting of articles by leading practitioners on all aspects of interfaces in solids. 

Liu, M. and Z. Wu, Significance of interfaces in solid-state cells with porous electrodes of mixed ionic-electronic conductors. Sohd State Ionics, 1998. 107 pp. 105-110... 

Jaimuk J, Maier J, Pejovnik S (1995) Interfaces in solid ionic cmiducfaus Equilibrium and small signal picture. Solid State Itm 75 51—58... 

Zeider, JA., Shen, Y., Baker, C., Taday, P.F, Pepper, M., and Rades, T. (2007) Analysis of coating structures and interfaces in solid oral dosage forms by three dimensional terahertz pulsed imaging. /. Pharm. Sci., 96 (2), 330-340. 

H. Nishiyama, M. Aizawa, H. Yokokawa, T. Horita, N. Sakai, M. Dokiya, T. Kawada, Stability of lanthanum chromite-lanthanum strontium manganite interface in solid oxide fuel cells. J. Electrochem. Soc. 143(7), 2332-2341 (1996)... 

Grain boundaries Internal interfaces in solids where two single crystal grains meet one another. In most solids, the atomic matching between the interfaces is poor. 

This study was in real time measured that the reflective echo height of the bonding interface in the solid phase diffused bonding process of carbon steel and titanium using ultrasonic testing method. As a result, the following were made discernment. 

The importance of the solid-liquid interface in a host of applications has led to extensive study over the past 50 years. Certainly, the study of the solid-liquid interface is no easier than that of the solid-gas interface, and all the complexities noted in Section VIM are present. The surface structural and spectroscopic techniques presented in Chapter VIII are not generally applicable to liquids (note, however. Ref. 1). There is, perforce, some retreat to phenomenology, empirical rules, and semiempirical models. The central importance of the Young equation is evident even in its modification to treat surface heterogeneity or roughness. ... 

The adsorption of detergent-type molecules on fabrics and at the solid-solution interface in general shows a complexity that might be mentioned briefly. Some fairly characteristic data are shown in Fig. XlIl-15 [242]. There is a break at point A, marking a sudden increase in slope, followed by a maximum in the amount adsorbed. The problem is that if such data represent true equilibrium in a two-component system, it is possible to argue a second law violation (note Problem Xni-14) (although see Ref. 243). 

It was pointed out in Section XIII-4A that if the contact angle between a solid particle and two liquid phases is finite, a stable position for the particle is at the liquid-liquid interface. Coalescence is inhibited because it takes work to displace the particle from the interface. In addition, one can account for the type of emulsion that is formed, 0/W or W/O, simply in terms of the contact angle value. As illustrated in Fig. XIV-7, the bulk of the particle will lie in that liquid that most nearly wets it, and by what seems to be a correct application of the early oriented wedge" principle (see Ref. 48), this liquid should then constitute the outer phase. Furthermore, the action of surfactants should be predictable in terms of their effect on the contact angle. This was, indeed, found to be the case in a study by Schulman and Leja [49] on the stabilization of emulsions by barium sulfate. 

Perhaps the most intensely studied interface is that between a solid and vacuum, i.e. a surface. There are a number of reasons for this. For one, it is more experunentally accessible than other interfaces. In addition, it is... 

Studies of the liquid-solid interface can be divided into those that are perfonned ex situ and those perfomied in situ. In an ex situ experiment, a surface is first reacted in solution, and then removed from the solution and transferred into a UFIV spectrometer for measurement. There has recently been, however, much work aimed at interrogating the liquid-solid interface in situ, i.e. while chemistry is occurring rather than after the fact. 

Seah M P and Dench W A 1979 Quantitative electron spectroscopy of surfaces a standard data base for electron inelastic mean free paths in solids Surf, interface Anai. 1 2... 

Cavitation damage is a fonn of deterioration associated with materials in rapidly moving liquid environments, due to collapse of cavities (or vapour bubbles) in the liquid at a solid-liquid interface, in the high-pressure regions of high flow. If the liquid in movement is corrosive towards the metal, the damage of the metal may be greatly increased (cavitation corrosion). 

In many important cases of reactions involving gas, hquid, and solid phases, the solid phase is a porous catalyst. It may be in a fixed bed or it may be suspended in the fluid mixture. In general, the reaction occurs either in the liquid phase or at the liquid/solid interface. In fixed-bed reactors the particles have diameters of about 3 mm (0.12 in) and occupy about 50 percent of the vessel volume. Diameters of suspended particles are hmited to O.I to 0.2 mm (0.004 to 0.008 in) minimum by requirements of filterability and occupy I to 10 percent of the volume in stirred vessels. 

The distance moved by the solid-liquid interface in 1 second is given by... 

Fig. 7.5. Nucleation in solids. Heterogeneous nucleotion con take place at defects like dislocations, grain boundaries, interphase interfaces and free surfaces. Homogeneous nucleation, in defect-free regions, is rare.

Phillpot, S.R., Yip, S., Okamoto, P.R. and Wolf, D. (1992) Role of interfaces in melting and solid-state amorphization, in Materials Interfaces Atomic-Level Structure and Properties, ed. Wolf, D. and Yip, S. (Chapman and Hall, London) p. 228. 

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