Microstructure distortion

We have also used the back-light scattering technique to investigate the effect of shear rate on emulsion structure. The microstructure distortions occurred at high shear rates (25). 

Laminographical approaches can be used for layer-by-layer visualization of the internal microstructure for the flat objects (multilayers, PCBs etc.), that caimot be reconstructed by computerized tomography because of the limited possibilities in rotation. Depth and lateral spatial resolutions are limited by the tube, camera and rotation accuracy. Microfocus X-ray tubes and digital registration techniques with static cameras allow improving resolution. Precision object manipulations and more effective distortion corrections can do further improvement. 

Visually, the sites resemble mechanically induced gouges or indentions in the tube wall. However, examinations of the microstructure at these sites revealed no distortion of the metal, which would certainly occur had the indentions been mechanically induced. The erosive character of the highly localized turbulent flow was the predominant aspect responsible for the metal loss, there being little or perhaps no contribution from corrosion of the metal. 

Hemispherical shape of pit is often distorted by microstructural effects... 

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... 

Workers have shown theoretically that this effect can be caused both at the microstructural level (due to tunneling of the current near the TPB) as well as on a macroscopic level when the electrode is not perfectly electronically conductive and the current collector makes only intermittent contact. ° Fleig and Maier further showed that current constriction can have a distortional effect on the frequency response (impedance), which is sensitive to the relative importance of the surface vs bulk path. In particular, they showed that unlike the bulk electrolyte resistance, the constriction resistance can appear at frequencies overlapping the interfacial impedance. Thus, the effect can be hard to separate experimentally from interfacial electrochemical-kinetic resistances, particularly when one considers that many of the same microstructural parameters influencing the electrochemical kinetics (TPB area, contact area) also influence the current constriction. 

In practice, clean (very clean ) cleaved or otherwise smoothed metal surfaces should be made to effect a firm mechanical contact using a strong force but one that is still insufficient to cause macroscopic deformation even at an elevated temperature. This will have to be been done, usually, in vacuum or at least in an inert atmosphere. The problems of hard to get to (inaccessible) joints and possibly objectionable thermal conditions and the resultant undesired microstructures such as Kirkendall voids, for instance, are minimized, if not eliminated all together. Thus, good-quality, distortion-free joints requiring no additional machining or other posttreatment can be achieved. 

The microstructure of a semidilute suspension of hard spheres will become distorted with the application of flow. This is manifested by anisotropy in the spatial position of the centers of mass of the spheres, which is described the pair distribution function, P2 (r). This... 

It is also important to have an understanding of the microstructure of the substrate, and of its surface texture. Thus preferential wetting of thermal grainboundary grooves (Figure 3.2) can distort the triple line (see Appendix H) and the... 

At very low shear rates (i.e., flow velocities), particles in a chemically stable suspension approximately follow the layers of constant velocities, as indicated in Fig. 2. But at higher shear rates hydro-dynamic forces drive particles out of layers of constant velocity. The competition between hydrodynamic forces that distort the microstructure of the suspension and drive particles together, and the Brownian motion and repulsive interparticle forces keeping particles apart, leads to a shear dependency of the viscosity of suspensions. These effects depend on the effective volume fraction of... 

Phase I work revealed that a sufficient condition for obtaining spectra without the Christiansen eflFect distortion was that the deposited film has no areas bare of polymer. When such a continuous film was obtained, other microstructural features and even polymer type were of secondary importance and were possibly even unimportant in obtaining good quality spectra. It was possible to obtain undistorted spectra from discontinuous films. However, particle size range of the deposit appeared critical to the results. The diversities of polymer morphologies possible and their sensitivity to operating conditions meant that tailoring particle size would be very difficult. Deposition control to ensure continuous films appeared as a much more attainable objective and was pursued in Phase II. 

H. Sugiyama and O. Nittono, Microstructure and lattice distortion of anodized porous silicon layers, J. Cryst. Growth 103, 156, 1990. 

---