Multilayer composites

A more dramatic type of restmctiiring occurs with the adsorption of alkali metals onto certain fee metal surfaces [39]. In this case, multilayer composite surfaces are fomied in which the alkali and metal atoms are intemiixed in an ordered stmcture. These stmctiires involve the substitution of alkali atoms into substrate sites, and the details of the stmctiires are found to be coverage-dependent. The stmctiires are influenced by the repulsion between the dipoles fomied by neighbouring alkali adsorbates and by the interactions of the alkalis with the substrate itself [40]. 

Multilayered composite sheets and plates can be bonded in a single explosion, and cladding of both sides of a backing metal can be achieved simultaneously. When two sides are clad, the two prime or clad metals need not be of the same thickness nor of the same metal or alloy. 

Song HS, Hyun SH, Moon J, and Song RH. Electrochemical and microstructural characterization of polymeric resin-derived multilayered composite cathode for SOFC. J. Power Sources 2005 145 272-277. 

Porous Si02 nanoparticles deposited by a common wet-coating sol-gel technique, for instance, form a single-layer, low-refractive-index and cost-efficient antireflective coating on glass as an alternative to common multilayer compositions (Figure 4.3).4 The coating thereby obtained exhibits porosity of up to 50% and a refractive index between 1.25 and 1.3, which corresponds to a transmission maximum up to 99% and an... 

In work like that described in Scheme 6, Bruening reported the synthesis of multilayer composites by alternating deposition of Gantrez and the linear polyvalent nucleophile poly(allylamine) [58]. The impermeable films that were produced by this multistep hyperbranched graft chemistry were shown to passivate aluminum surfaces. 

The actual deposition of the multilayered composite can be carried out by either current or potential control. Clearly, a pulsed polarization curve has to be constructed for the former case. The actual composition modulation cycle would be controlled coulometrically by fixing the amount of electric charge delivered while at point A in Figure 17.2 Qp and the amount of charge delivered while at point B in Figure 17.2 (2b) via suitable input to the unit regulating the pulsing. 

Work in groups of three. Your plant is replacing asbestos used to insulate low-pressure steam pipes with a new multilayer composite material composed of a 2.5-cm-thick, polystyrene foam (k = 0.029 W/m K) and a 2-mm-thick, outer, protective layer of polyethylene (k = 0.33 W/m K). Assume that the pipe carries saturated steam at 130°C and that the outer surface of the insulation is 30°C. The piping is stainless steel k = 14 W/m K), with ID = 0.0254 m and OD = 0.0508 m. Use the equations developed in Example Problem 4.1 to solve the following problems, assuming a pipe length of 1 m. 

Other authors have produced multi-ion chemfets. Matsuo and Esashi have demonstrated that multi-ion ehemfet structures can be planar processed in a two-ion needle shaped form (48). Their ingenious needle shaped design permits them to incorporate two or possibly three sensitive elements at the tip. However, the demands of electrical and chemical isolation become increasingly difficult as the number of ion sensitive elements increases in these devices. Pace has demonstrated that a pH sensitive element, combined with a multilayer composite structure, can be used to detect a wide range of chemical species (56). This concept is quite versatile and has been proposed as the means to extend the capability of the pH sensitive... 

Figure 3.24 Method developed by Ward, Browall and others at General Electric to make multilayer composite membranes by the water casting technique [55]...

Figure 3.26 Schematic and scanning electron micrograph of a multilayer composite membrane on a microporous support. (Courtesy of Membrane Technology and Research, Inc.)...

Another type of gas separation membrane is the multilayer composite structure shown in Figure 8.9. In this membrane, a finely microporous support membrane is overcoated with a thin layer of the selective polymer, which is a different material from the support. Additional layers of very permeable materials such as silicone rubber may also be applied to protect the selective layer and to seal any defects. In general it has been difficult to make composite membranes with... 

During the last few years, ceramic- and zeolite-based membranes have begun to be used for a few commercial separations. These membranes are all multilayer composite structures formed by coating a thin selective ceramic or zeolite layer onto a microporous ceramic support. Ceramic membranes are prepared by the sol-gel technique described in Chapter 3 zeolite membranes are prepared by direct crystallization, in which the thin zeolite layer is crystallized at high pressure and temperature directly onto the microporous support [24,25],... 

A third type of membrane reactor combines the functions of contactor and separator. An example of this combination membrane reactor is shown in Figure 13.16(c), in which the membrane is a multilayer composite. The layer facing the organic feed stream is an immobilized organic liquid membrane the layer facing the aqueous product solution contains an enzyme catalyst for the deesterification reaction... 

Willner and coworkers demonstrated three-dimensional networks of Au, Ag, and mixed composites of Au and Ag nanoparticles assembled on a conductive (indium-doped tin oxide) glass support by stepwise LbL assembly with A,A -bis(2-aminoethyl)-4,4 -bipyridinium as a redox-active cross-linker.8 37 The electrostatic attraction between the amino-bifunctional cross-linker and the citrate-protected metal particles led to the assembly of a multilayered composite nanoparticle network. The surface coverage of the metal nanoparticles and bipyridinium units associated with the Au nanoparticle assembly increased almost linearly upon the formation of the three-dimensional (3D) network. A coulometric analysis indicated an electroactive 3D nanoparticle array, implying that electron transport through the nanoparticles is feasible. A similar multilayered nanoparticle network was later used in a study on a sensor application by using bis-bipyridinium cyclophane as a cross-linker for Au nanoparticles and as a molecular receptor for rr-donor substrates.8... 

To replace glass, a plastic substrate must offer the properties of glass, i.e. clarity, dimensional stability, thermal stability, barrier, solvent resistance, low coefficient of thermal expansion, and a smooth surface. No plastic film has all these properties so any plastic based substrate will almost certainly be a multilayer composite structure. In addition to choosing the right materials for the different layers, one now has a new set of issues associated with the properties of multilayer structures. These issues include the adhesion of the different layers, the effect of thermal and environmental cycling, and the effect of flexing the structure, not only on specific... 

As concerns the piezoelectric layer, the first choice often goes to lead zirconate titanate (PZT) because of its outstanding piezoelectric, pyroelectric and ferroelectric properties. Nickel ferrite (NF) is not widely employed for the synthesis of the multilayered composites owing to a strong reduction of its magnetization in the lower grain size limit. However, a very thin NF layer can help to attain entirely different properties and, hence, this material has been chosen as a sandwiched layer in the present work. 

Both, Yu and Wang and coworkers [94, 95] have developed multilayer composite... 

Blest et al. (1999) examine the modelling and simulation of resin flow, heat transfer and curing of multilayer composite laminates during autoclave processing. An empirical cure equation is used ... 

Mechanical and electrical properties of multilayer composites of silicon carbide... 

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