Microstructure composite

A quite different approach was introduced in the early 1980s [44-46], in which a dense solid electrode is fabricated which has a composite microstructure in which particles of the reactant phase are finely dispersed within a solid, electronically conducting matrix in which the electroactive species is also mobile. There is thus a large internal reactant/mixed-conductor matrix interfacial area. The electroactive species is transported through the solid matrix to this interfacial region, where it undergoes the chemical part of the electrode reaction. Since the matrix material is also an electronic conductor, it can also act as the electrode s current collector. The electrochemical part of the reaction takes place on the outer surface of the composite electrode. 

Delplancke-Ogletree, M. R, Monteiro, O. R., and Brown, I. G., Preparation of TiC and TiC/DLC Multilayers by Metal Plasma Immersion Ion Implantation and Deposition Relationship Between Composition, Microstructure and Wear Properties," Materials Research Society Symposia Proceedings, Voi.438,1997,p.639. 

Li, L. and Yan, B. (2009) BiV04/Bi203 submicrometer sphere composite microstructure and photocatalytic activityunder visihle-light irradiation. Journal of Alloys and Compounds, 476 (1—2), 624—628. 

In addition to bilayered electrodes with a functional layer and a support layer, electrodes have also been produced with multilayered or graded structures in which the composition, microstructure, or both are varied either continuously or in a series of steps across the electrode thickness to improve the cell performance compared to that of a single- or bilayered electrode. For example, triple-layer electrodes commonly utilize a functional layer with high surface area and small particle size, a second functional layer (e.g., reference [26]) or diffusion layer with high porosity and coarse structure, and a current collector layer with coarse porosity and only the electronically conductive phase (e.g., reference [27]) to improve the contact with the interconnect. 

Figure 48. Kenjo s ID macrohomogeneous model for polarization and ohmic losses in a composite electrode, (a) Sketch of the composite microstructure, (b) Description of ionic conduction in the ionic subphase and reaction at the TPB s in terms of interpenetrating thin films following the approach of ref 302. (c) Predicted overpotential profile in the electrode near the electrode/electrolyte interface, (d) Predicted admittance as a function of the electrode thickness as used to fit the data in Figure 47. (Reprinted with permission from refs 300 and 301. Copyright 1991 and 1992 Electrochemical Society, Inc. and Elsevier, reepectively.)...

The composite microstructure (and, therefore, its composite properties and polishing performance) is largely determined by the mode of manufacture. A summary of the major process variables associated with pad manufacturing and the anticipated effects on physical properties is given in Table II. 

The ultrasonic C-scan technique is the most widely used nondestructive method of locating defects in the composite microstructure. The through transmission C-scan is easy to implement and a large composite panel can be scanned in a matter of minutes. The problem with this technique is that a C-scan cannot reveal the type of defect present. Hence, there is no way to determine if a flaw detected by the C-scan is due to incomplete contact of an interply interface or some other type of defect in the composite microstructure. 

The phenomenal growth in commercial production of polymers by anionic polymerization can be attributed to the unprecedented control the process provides over the polymer properties. This control is most extensive in organolithium initiated polymerizations and includes polymer composition, microstructure, molecular weight, molecular weight distribution, choice of functional end groups and even monomer sequence distribution in copolymers. Furthermore, a judicious choice of process conditions affords termination and transfer free polymerization which leads to very efficient methods of block polymer synthesis. 

Anionic polymerizations initiated with alkyllithium compounds enable us to prepare homopolymers as well as copolymers from diene and vinylaromatic monomers. These polymerization systems are unique in that they have precise control over such polymer properties as composition, microstructure, molecular weight, molecular weight distribution, choice of functional end groups and even copolymer monomer sequence distribution. Attempts have been made in this paper to survey these salient features with respect to their chemistry and commercial applications. 

An ultrasonic experiment consists of two stages measurement of the ultrasonic properties of the material, e.g., velocity, attenuation or impedance interpretation of these measurements to provide information about the relevant properties of the material. These may either be fundamental physico-chemical properties (such as composition, microstructure or molecular interactions) or functional properties (such as stability, rheology or appearance). 

In the development of functionally graded materials, there are two approaches. One is to eliminate the boundary of laminated-type composites, thereby eliminating discontinuities in the properties at the boundary. The other option is to make non-uniform distributions of dispersoids in a homogeneous composite, thus creating multiple functions within the material.2 Therefore, continuous variation in composition, microstructure and so on, results in change in properties as a function of position in the component.6... 

In the literature, there has been no report about production of functionally graded SiAION ceramics by tape casting. The main advantage of this method with respect to others is that continuous change in composition, microstructure and mechanical properties can be obtained by stacking controlled layer thicknesses of different tape compositions. 

The polymerization of norbornene, Eq. (19), is stopped by cooling the reaction mixture to room temperature. The active polymer 11 can be stored for long periods of time. Heating 11 to temperatures above 65 °C in the presence of monomer causes renewed chain propagation. The subsequent addition of different cyclic olefins, such as endo- and exo-dicyclopentadiene, benzonorbomadiene and 6-methylbenzonorbornadiene resulted in the formation of well-defined AB- and ABA-type block copolymers, Eq. (21) [38]. Triblock copolymers 13 with narrow molecular weight distributions (polydispersity = 1.14) were prepared. Thus, the living character enables the preparation of new uniform block copolymers of predictable composition, microstructure and molecular weight. 

Powder pressing is a very flexible process in that materials that are difficult to melt or deform may be produced in a variety of shapes and sizes. Adding to the flexibility of the process may be the fact that the starting powder does not need to be uniform. Different size powders, or more commonly, different types of powders may be used to produce composite microstructures. These different powders may be distributed uniformly throughout the fabricated component, or isolated to form a functionally graded material. Powder pressing is commonly used to... 

Sandrock, G. D., "The Interrelations Among Composition Microstructure, and Hydriding Behavior for Alloys Based on the Intermetallic Compound FeTi", International Nickel Co., Suffern, NY, 10901, Final Report for Contract BNL 352410S, June 30, 1976. 

Processing conditions required to attain desirable composite properties can be defined more easily if the factors controlling composite microstructure are understood. Such factors include type of precursors employed and the composite s processing history. The microstructure of the matrix may contribute to the performance of the fibers and influence the properties of the composite. Reviewed are experiments to determine matrix micro-structural features, how microstructural variations are achieved, and ways in which thermal expansion and fracture behavior relate to microstructure. 

Metallurgical alloy composition, microstructure, and yield strength. (Phull)5... 

As was detailed in this section, TEM can bring numerous pieces of information regarding the polymer/nanotube composite microstructure. However, it has to be recalled that nanofillers such as nanotubes easily agglomerates and their dispersion state has to be characterised from the micron to the nanometre scale. This is one reason, among others, why Scanning Electron Microscopy is another widely used to characterise polymer/nanotube composites. 

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