Layered microstructures

Fernandez, R., Ferreira-Aparicio, P, and Daza, L. PEMFC electrode preparation Influence of the solvent composition and evaporation rate on the catalytic layer microstructure. Journal of Power Sources 2005 151 18-24. 

PPD effects on surface layers microstructure. The porosity is observed in the core of deformed specimens unlike non-deformed ones as a result of -and... 

Figure 3. High resolution TEM image of a PEFC catalyst layer microstructure. Reproduced from Gostick et al.21 with permission from Karren L. More, Oak Ridge National Laboratory, USA.

Figure 4. Reconstructed catalyst layer microstructure along with pore and electrolyte phase volume fractions distribution.

The anode (fuel electrode) consists of an approximately 120/rm thick Ni/YSZ cermet layer. This is achieved simply by applying a slurry of nickel and YSZ powders to the electrolyte and sintering. A cross-section of the 3-layer microstructure is shown in Fig. 4.33. 

The above features of a sheared colloidal crystal appear to be similar in both BCC and FCC structures. However, there are differences in details, and perhaps even within a given symmetry the flow behavior might vary with particle concentration or charge density. For example, Chen et al. (1994) have shown that between the strained crystal and sliding-layer microstructures there can be a polycrystalline structure, the formation of which produces a discontinuous drop in shear stress (see Fig. 6-33). Ackerson and coworkers gave a detailed description of the fascinating shear-induced microstructures of these systems (Ackerson and Clark 1984 Ackerson et al. 1986 Chen et al. 1992, 1994). 

Fig. 5. Cross-sectional SEM micrographs of non-planner laminates. Sequentionally deposited from BT-ST/ethanol suspensions of composition 100, 75, 50 and 25 v/o of BT. (a) is a low magnification micrograph showing the fibre-electrodes position and (b) is a high magnification micrograph showing the details of layers microstructure.

Characterize nitride layer microstructure and composition by x-ray diffraction, electron probe microanalysis, scanning electron microscopy, and transmission electron microscopy. Use this information in a feedback loop to modify alloy chemistry and nitridation processing conditions to optimize the protectiveness of the nitride surface layer. 

GLASS-CONTAINING COMPOSITES WITH GRADED AND LAYERED MICROSTRUCTURES... 

TABLE 1. Selected mechanical properties and area of application of some glass-containing composite systems with interpenetrating, graded or layered microstructure and hybrid composites. (The fracture strength values quoted are flexural strength data unless otherwise stated). 

Somasundaran, P. and Runkana, V. 2005. Investigation of the flocculation of colloidal suspensions by controlling adsorbed layer microstructure and population balance modeling. Chem. Eng. Res. Des. 83 905-914. 

It is now well established that a fiber coating must be deposited on the fiber prior to infiltration of the matrix, in order to control the fiber-matrix bonding and the mechanical behavior of the composite. Pyrocarbon (PyC), boron nitride or (PyC-SiC)- and (BN-PyC)-multilayers, with an overall thickness ranging from about 0.1 pm to about 1 pm, and displaying a layered crystal structure (PyC, BN) or a layered microstructure (multilayers), are the most common interphase materials in nonoxide CMCs. The main role of the interphase is to deflect the microcracks which form in the matrix under loading, and hence to protect the fiber from notch effect. 

Vetters H., et al.. TEM analysis of microcrystalline boride layers, Microstructural Science (ASM internat. Publ. Metals Park Ohio 1988), 16,499-507... 

All the above-mentioned results indicate that, for attainment of the essential parameters of chemical sensors, it is necessary to use porous layers with optimal thickness and porosity, which in most cases are being established experimentally. For example, Connolly et al. (2002) found that if the maximum sensitivity of porous silicon and polysilicon to humidity was achieved using 30 % HF, the best result for humidity sensitivity of porous SiC was obtained using 73 % HF (see Fig. 26.5). The layer microstructure in terms of pore shape, pore size, and pore distribution is very important for the capillary condensation mechanisms. This means that all technological parameters of PSi forming should have very strong control. As a result, we cannot expect that PSi-based gas sensors will have good reproducibility of their parameters. 

Experimental phase diagrams for amorphous block copolymers were explored by Khandpur and co-workers (29). First, low-frequency isochronal shear modulus-temperature curves were developed on a series of polyiso-prene-h/ocA -polystyrene polymers to guide the selection of temperatures for the transmission electron microscopy and SAXS experiments to follow see Figure 13.14 (29). Both order-order (OOT) and ODT transitions were iden-tihed. The OOT are marked by open arrows, while the ODT are shown by hlled arrows. Since the ODT occurs as the temperature is raised, an upper critical solution temperature is indicated, much more frequent with block copolymers than with polymer blends. The regions marked A, B, C, and D denote lamellar, bi-continuous, cylindrical, and perforated layered microstructures, respectively. The changes in morphology are driven by the temperature dependence of Xn,... 

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