Microstructure properties

The microstructure/property relationships observed in shock-recovered samples have been often tacitly assumed to result solely from the shock compression, duration, and rarefaction due to the imposed uniaxial-strain shock. Recent shock-recovery studies have, however, shown that the degree of residual strain in the sample significantly influences the measured struc-... 

There is, in any case, an important advantage in using the Rietveld analysis, which is the possibility of quanti-f5ing the phase to which we are ascribing the microstructure properties. 

Improved characterization of the morphological/microstructural properties of porous solids, and the associated transport properties of fluids imbibed into these materials, is crucial to the development of new porous materials, such as ceramics. Of particular interest is the fabrication of so-called functionalized ceramics, which contain a pore structure tailored to a specific biomedical or industrial application (e.g., molecular filters, catalysts, gas storage cells, drug delivery devices, tissue scaffolds) [1-3]. Functionalization of ceramics can involve the use of graded or layered pore microstructure, morphology or chemical composition. 

The adsorption/desorption isotherms measured by NMR (equivalent to conventionally measured isotherms), extracted from two different regions of the imaging field of view corresponding to the two ceramics, are shown in Figure 3.5.9. Once these local isotherms are extracted, they are simply the local adsorption for that point in space contained within the material, measured non-invasively and non-destructively. Conventional analysis techniques for adsorption isotherms (such as BET theory) can therefore be applied to the data, to determine the microstructural properties corresponding to that isotherm curve. 

NMR signals are highly sensitive, via a number of different mechanisms, to the physical and chemical properties of porous materials. Using the set of NMR-based measurement methods that we have developed, it is possible to non-invasively and non-destructively characterize both the microstructural properties of the materials and relaxation properties of fluids imbibed into these materials. 

Figure 1 Polymers in materials science Interrelationships between synthesis, processing, microstructure, properties and characterisation.

Molecular calculations provide approaches to supramolecular structure and to the dynamics of self-assembly by extending atomic-molecular physics. Alternatively, the tools of finite element analysis can be used to approach the simulation of self-assembled film properties. The voxel4 size in finite element analysis needs be small compared to significant variation in structure-property relationships for self-assembled structures, this implies use of voxels of nanometer dimensions. However, the continuum constitutive relationships utilized for macroscopic-system calculations will be difficult to extend at this scale because nanostructure properties are expected to differ from microstructural properties. In addition, in structures with a high density of boundaries (such as thin multilayer films), poorly understood boundary conditions may contribute to inaccuracies. 

Lacour, C., Laher-Lacour, F Dubon, A., Lagues, M., Mocaer, P. Freeze-drying preparation of yttrium barium copper oxide. Correlations between electrical and microstructural properties. PhysicaC (Amsterdam), 167 (3-4), p. 287-290, 1990... 

The microstructure, properties, and performance of Ni-YSZ anodes depend sensitively on the microscopic characteristics of the raw materials (e.g., particles size and morphology of NiO and YSZ powders). The particle sizes of the starting YSZ powders vary usually from 0.2 to 0.3 pm, whereas those for the NiO powders are 1 pm. The Ni to YSZ volume ratio usually varies from 35 65 to 55 45. For example, the reported Ni to YSZ volume ratios include 34 66 [20, 21], 40 60 [24], 43 57 [22], and 55 45 [23], For a bilayer anode, the functional anode layer in contact with the electrolyte contains 45 to 50 vol% Ni, whereas the anode support layer has 35 to 40 vol% Ni [25, 26], A pore former is usually added to tailor the shrinkage (for the cofiring) and to achieve sufficient porosity (>30 vol%) in the anode or the anode support layer. 

Huebner W, Anderson HU, Reed DM, Sehlin S, and Deng X. Microstructure-property relationships of Ni Zr02 anodes. In Dokiya M, Yamamoto O, Tagawa H, Singhal SC, editors. Proceedings of the Fourth International Symposium on Solid Oxide Fuel Cells (SOFC-IV), Pennington, NJ The Electrochemical Society, 1995 95(1) 696-705. 

As a result of these processing-microstructure-property-performance inter-relationships, it is essential to optimize not only the material compositions to be utilized in the fuel cell components, but also the processing methods used to produce those components. Such optimization must be performed considering both short- and... 

Microstructural, Property, and Performance Requirements of SOFC Components... 

Each of the components of an SOFC stack anodes, cathodes, electrolytes, and interconnects must be thermally, chemically, mechanically, and dimensionally stable at the operating conditions and compatible with the other layers with which they come into contact in terms of thermal expansion and chemical inter-reaction. They must also have compatible processing characteristics. In addition to those requirements, the individual layers have additional microstructural, property, and processing target requirements, as summarized in Table 6.1. 

Microstructural, Property, and Processing Requirements of SOFC Component Layers... 

A rheological measurement is a useful tool for probing the microstructural properties of a sample. If we are able to perform experiments at low stresses or strains the spatial arrangement of the particles and molecules that make up the system are only slightly perturbed by the measurement. We can assume that the response is characteristic of the microstructure in quiescent conditions. Here our convective motion due to the applied deformation is less than that of Brownian diffusion. The ratio of these terms is the Peclet number and is much less than unity. In Equation (5.1) we have written the Peclet number in terms of stresses ... 

The major difficulty in predicting the viscosity of these systems is due to the interplay between hydrodynamics, the colloid pair interaction energy and the particle microstructure. Whilst predictions for atomic fluids exist for the contribution of the microstructural properties of the system to the rheology, they obviously will not take account of the role of the solvent medium in colloidal systems. Many of these models depend upon the notion that the applied shear field distorts the local microstructure. The mathematical consequence of this is that they rely on the rate of change of the pair distribution function with distance over longer length scales than is the case for the shear modulus. Thus... 

Recent developments and prospects of these methods have been discussed in a chapter by Schneider et al. (2001). It was underlined that these methods are widely applied for the characterization of crystalline materials (phase identification, quantitative analysis, determination of structure imperfections, crystal structure determination and analysis of 3D microstructural properties). Phase identification was traditionally based on a comparison of observed data with interplanar spacings and relative intensities (d and T) listed for crystalline materials. More recent search-match procedures, based on digitized patterns, and Powder Diffraction File (International Centre for Diffraction Data, USA.) containing powder data for hundreds of thousands substances may result in a fast efficient qualitative analysis. The determination of the amounts of different phases present in a multi-component sample (quantitative analysis) is based on the so-called Rietveld method. Procedures for pattern indexing, structure solution and refinement of structure model are based on the same method. 

Coarse-grained molecular d5mamics simulations in the presence of solvent provide insights into the effect of dispersion medium on microstructural properties of the catalyst layer. To explore the interaction of Nation and solvent in the catalyst ink mixture, simulations were performed in the presence of carbon/Pt particles, water, implicit polar solvent (with different dielectric constant e), and ionomer. Malek et al. developed the computational approach based on CGMD simulations in two steps. In the first step, groups of atoms of the distinct components were replaced by spherical beads with predefined subnanoscopic length scale. In the second step, parameters of renormalized interaction energies between the distinct beads were specified. 

Characteristic microstructural properties of TiOj membranes produced in this way are given in Table 2.5. Mean pore diameters of 4-5 nm were obtained after heat treatment at T < 500°C. The pore size distribution was narrow in this case and the particle size in the membrane layer was about 5 nm. Anderson et al. (1988) discuss sol/gel chemistry and the formation of nonsupported titania membranes using the colloidal suspension synthesis of the type mentioned above. The particle size in the colloidal dispersion increased with the H/Ti ratio from 80 nm (H /Ti = 0.4, minimum gelling volume) to 140 nm (H /Ti " — 1.0). The membranes, thus prepared, had microstructural characteristics similar to those reported in Table 2.5 and are composed mainly of 20 nm anatase particles. Considerable problems were encountered in membrane synthesis with the polymeric gel route. Anderson et al. (1988) report that clear polymeric sols without precipitates could be produced using initial water concentrations up to 16 mole per mole Ti. Transparent gels could be obtained only when the molar ratio of H2O to Ti is < 4. Gels with up to 12 wt.% T1O2 could be produced provided a low pH is used (H /Ti + < 0.025). 

Pavlovic, T. and A. Ignatiev. 1986. Optical and microstructural properties of anodically oxidized aluminum. Thin Solid Films 138 97-109. 

Lee, W. E., and W. M. Rainforth, Ceramic Microstructures Property Control by Processing, Chapman Hall, London, 1994. 

Microstructure-property correlations in dynamically vulcanized thermoplastic elastomers based on polypropylene (PP)/EPDM have shown that clay was nearly exfoliated and randomly distributed into the continuous polypropylene phase [23]. SEM photomicrographs revealed that the size of rubber particles increased with clay incorporation. Also, the clay layers act as nucleating agents, resulting in higher crystallization temperature and reduced degree of crystallinity. 

Konstandopoulos, A. G., Skaperdas, E., and Masoudi, M. Microstructural properties of soot deposits in diesel particulate traps. SAE Technical Paper No. 2002-01-1015 (SP-1673) (2002). 

Hence, from the previously described light-scattering study of caseinate self-assembly in solution, we can postulate that heating/cooling not only alters the nature and strength of the physical (hydrophobic) interactions between emulsion droplets covered by caseinate. It most likely also transforms the nanoscale structural characteristics of the protein network in the bulk and at the interface, thereby affecting the viscoelastic and microstructural properties of the emulsions. 

Aochi, Y. O., and W. J. Farmer, Role of microstructural properties in the time-dependent sorption/desorption behavior of 1,2-dichloroethane on humic substances , Environ. Sci. Technol., 31,2520-2526 (1997). 

The objective of this work was to study the reaction conditions and microstructural properties of the products obtained in the Ti-N and Ti-C-N systems when combustion is carried out under a nitrogen pressure range 0.1-1.4 MPa. 

Coercivity of Thin-Film Media. The coercivity in a magnetic material is an important parameter for applications but it is difficult to understand its physical background. It can be varied from nearly zero to more than 2000 kA/m in a variety of materials. For thin-film recording media, values of more than 250 kA/m have been reported. First of all the coercivity is an extrinsic parameter and is strongly influenced by the microstructural properties of the layer such as crystal size and shape, composition, and texture. These properties are diiecdy related to the preparation conditions. Material choice and chemical inhomogeneties are responsible for the M of a material and this is also an influencing parameter of the final FF, In crystalline material, the crystalline anisotropy field plays an important role. It is difficult to discriminate between all these parameters and to understand the coercivity origin in the different thin-film materials in detail. 

Chemical and phase purity are not always desirable. For example, H- and N-doped silicon carbide films behave as high temperature semiconductors, while silicon carbonitride glasses offer properties akin to glassy carbon with room temperature conductivities of 103 2 cm-118. Additional reasons for targeting materials that are not chemically or phase pure stem from the desire to control microstructural properties. 

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