Triple layer systems

ILD.The van der Waals Energy. The van der Waals energy per unit area for a triple layer system (hydrocarbon/ water/hydrocarbon) in air was calculated on the basis of the Lifshitz theory by Donners et al.4 and is well represented by the expression... 

The parameters include the critical cracking energy G and the mode-I tensile toughness of the coating. For the dual layer and triple layer systems presented here, the parameters deduced from three experiments for each type of sample are presented in Tables 6 and 7. The strain values are measured to an accuracy of 0.02% following a prior calibration. The applied stress is known to be within 0.1%, from a force sensor and the distance between two cracks is the average of twenty or so values determined to an accuracy of one micron in the central part of the specimen. 

The analytical approach developed by Schadler and Noyan, allows calculation of the stress redistribution in cracked triple layer systems. This approach assumes mechanical equilibrium of the cracked coating and the interlayer through perfectly adhering interfaces which transfer the applied stress to the substrate. It is thus possible to deduce expressions for stress distribution normal to the cracked film and shear stress distribution at the interlayer ... 

Trilayered systems can then be analyzed according to two different approaches the first focused on the reactional aspects at the interfaces and the second concentrated on the mechanical stability of the triple layer system. 

Table 7. Bending Tests on Triple Layer Systems...

Fig. 20 Critical scratching load L, macro-indentation failure load F and residual stresses SiC in the triple layer system, e. corresponds to the thickness of the Ta interlayer.

Fig. 13.27. A general view of the experimental YBa2Cu307/PrBa2Cu307/ YBa2Cu307 triple-layer system. The upper interfaee is based on the ion-etehed surfaee and the lower on the Br-ethanol-etehed surfaee.

The substitution of the two-sided tape with a film of an ionic conductor gives (Fig. 24) a triple-layered muscle working in air.114 The tape now acts as a solid electrolyte. Nevertheless, the system only works if the relative humidity in air surpasses 60%. Under these conditions, movements and rates similar to those shown by a triple layer working in aqueous solution were obtained. This device was developed in cooperation with Dr. M. A. De Paoli from the Campinnas University (Campinnas, Brazil). At the moment several groups are developing actuators, muscles, and electrochemomechanical devices based on bilayer or multilayer structures.115-125... 

Microscopic Subreactions and Macroscopic Proton Coefficients. The macroscopic proton coefficient may be used as a semi-empirical modeling variable when calibrated against major system parameters. However, x has also been used to evaluate the fundamental nature of metal/adsorbent interactions (e.g., 5). In this section, macroscopic proton coefficients (Xj and v) calculated from adsorption data are compared with the microscopic subreactions of the Triple-Layer Model ( 1 ) and their inter-relationships are discussed. 

A specific example of the relationship between the microscopic subreactions required to model experimental observations of metal removal and the macroscopic proton coefficient is shown for the case of Cd(II) adsorption onto a-A f (Figure 3). One variation of the surface coordination concept is used to describe the system subreactions the Triple Layer Model of Davis et al., (1,20). The specific subreactions which are considered, the formation constants and compact layer capacitances, are shown in Table IV. Protons are assigned to the o-plane (the oxide surface) and Cd(II) surface species and electrolyte ions to the 8-plane located a distance, 8, from the o-plane. 

MLR systems can be classified by the number of layers and the function of the PCM, e.g., two-layer RIE PCM. Some authors prefer to use "bi-level," "tri-level," "double-layer," "triple-layer," or any other permutation of these words to denote the number of layers. The word "layer" and simple numerical adjectives are used here, because "level" may cause confusion because of its association with masking levels and because simple numerical adjectives pronounce better when the number of layers exceeds three. 

Carbon nanotubes could be also used in a format of disc. A comparison smdy showed that the double-disk system (comprising two stacked disks with 60 mg of CNTs) exhibited extraction capabilities that were comparable to those of a commercial Cig disk with 500 mg sorbent for nonpolar or moderately polar compounds. Moreover, the former system was more powerful than the latter for extracting polar analytes. The triple-layered CNTs disk system showed good extraction efficiency when the sample volume was up to 3,000 mL. Katsumata et al. [136] obtained very high enrichment factor for preconcentration of atrazine and simazine (3,900 and 4,000, respectively, for 200 mL of sample solution when only 30 mg of MWCNTs was used in the format of disk. 

TCLP TDB TDF THC TBP TEM TLM TM-AFM TOC TRLFS TRU TSP TST TVS Toxicity characteristics leaching procedure Thermodynamic database Tyre-derived fuel Total hydrocarbon Tri-n-butyl phosphate Transmission electron microscopy Triple layer model Tapping mode atomic force microscopy Total organic carbon Time-resolved laser fluorescence spectroscopy Transuranic Total suspended particles Transition state theory Transportable vitrification system... 

Ringsdorf and coworkers used monolayer techniques for the creation of lipid functionalized streptavidin layers.252,253 In their pioneering work, a monolayer of biotinylated phospholipids initially created a two-dimensional docking matrix for the immobilization of streptavidin. In an effort to further expand this system while maintaining control over its structure, bis-biotinylated bifunctional linkers were employed. Addition of these linkers to concanavalin A created a new protein-based bidentate linker. Upon addition to the monolayer of the lipid-functionalized streptavidin a second biotilynated protein layer was created. Upon the further addition of streptavidin, they achieved in a step-by-step construction process well-defined alternating protein triple layers of streptavidin and concanavalin A (Figure 7.37b). A similar approach has more recently been used to crosslink... 

The n = 3 member of the Ruddiesden-Popper phases have triple-layer vertexsharing octahedrai siabs separated by rock-sait-iike iayers. It is a iow-dimensionai transport system with nine 2g bands. These can be denoted xz, xz", xz ", and so on, where " denotes the d band of the centrai iayer of an M-O-M-O-M iinkage. 

Fig. 18 Schematic representations and micrographs of damage case of the SiC / steel reference system and SiC/Ta/steel triple layers (x corresponds to the Ta interlayer thickness in microns).

In fig. 3.20b specific adsorption Is also accounted for. The notion of specific adsorption has been defined In sec. 3.3. In disperse systems, its occurrence is de facto Inferred from the dependence of certain double layer properties on the natures of counter- and co-lons Generally, ions interacting specifically (non-electrostatlcally) with the surface approach it to shorter distance p < d). The plane where these specifically adsorbed ions reside is called the inner Helmholtz plane (iHp) In colloid science, the model of fig. 3.20b Is also known as the triple layer model. In this model three charges and three capacitances can be distinguished. For the two inner layer differential capacitances... 

In the triple-layer model, at high c . C vanishes but in (3.6.31) the two capacitances and da /6a° remain. In addition, it has to be verified to what extent these capacitances are Independent of a°. At least three adjustable parameters remain, which seem more than adequate to explain the most recalcitrant surface charge curve. For the mercury system, where very refined capacitance measurements can be made, this is appropriate, but for unmly systems like oxides we easily mn the risk of overinterpretation. 

A potentially important development for the future of biomimetic research was published recently. Using a procedure developed by Whitesides, nucleophiles micropattemed on a gold surface were used as initiators to prepare poly(Y-benzyl-L-glutamate). Thus, an array of poly(amino acid) layers covalently attached to the surface was obtained. These would potentially act as mediators of biomimetic reactions. German workers have described the production of protein-DNA double and triple layers adsorbed on smfaces. Adhesion between layers was provided by biotin-streptavadin interactions and binding was detected by a quartz crystal microbalance. These studies may have some relevance to the understanding of protein DNA interactions at interfaces in biological systems. 

Triple-layered cyclophanes 262 can be synthesized according to Scheme 70 [77CL977 93JCS(P2)1373] or Scheme 73 [93JCS(P2)703], where one (4n 2)n system in starting material 258 or 265 is already a cyclophane,... 

If a strongly adsorbing bivalent metal ion is added to the system described by Eqs. (39) and (40), in which competitive adsorption of protons and ions of basic electrolyte occurs, then according to the triple layer model [103-105] its addition can cause the formation of two kinds of surface complexes inner-sphere complexes SOM formed at the 0-plain of the triple layer and outer-sphere complexes SO M + formed at the, 3-plain. Some recent studies by Hayes and Leckie [142-145] suggest that the formation of the inner-sphere complexes is more probable for divalent cations like Cu, Pb, Cd" ", etc. than the formation of outer-sphere surface complexes. So, in general [142,143] ... 

VIBRATIONAL SPECTROSCOPY Infrared and Raman spectroscopies have proven to be useful techniques for studying the interactions of ions with surfaces. Direct evidence for inner-sphere surface complex formation of metal and metalloid anions has come from vibrational spectroscopic characterization. Both Raman and Fourier transform infrared (FTIR) spectroscopies are capable of examining ion adsorption in wet systems. Chromate (Hsia et al., 1993) and arsenate (Hsia et al., 1994) were found to adsorb specifically on hydrous iron oxide using FTIR spectroscopy. Raman and FTIR spectroscopic studies of arsenic adsorption indicated inner-sphere surface complexes for arsenate and arsenite on amorphous iron oxide, inner-sphere and outer-sphere surface complexes for arsenite on amorphous iron oxide, and outer-sphere surface complexes for arsenite on amorphous aluminum oxide (Goldberg and Johnston, 2001). These surface configurations were used to constrain the surface complexes in application of the constant capacitance and triple layer models (Goldberg and Johnston, 2001). 

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