Internal microstructures

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. 

A caterpillar steel mini mixer can be connected to conventional tubing, either stainless steel or polymeric, to prolong the residence time. The caterpillar mixer as all types of split-recombine mixers, profits from high volume flows (e.g. 100 1 h and more at moderate pressure drops) at favorable pressure drop (not exceeding 5 bar) as its internal microstructures can be held large [25-28]. 

Successful development of such systems will lead to foamed materials having useful stress-absorbing characteristics in addition to controlled physics properties. Although our work in this area is currently in a very early stage, prototype materials have been successfully synthesized and assessed structurally using three-dimensional (3D) X-ray microtomography. The technique offers a unique insight into the internal microstructure of cellular materials (see Fig. 3). The diameter of the mainly open cell pores varies from approximately 100 to 250 pm (the resolution of the instrument is 5 pm), with cell walls of variable thickness. 

Most water-atomized metal particles (powders) have been observed to follow the log-normal size distribution pattern. Relatively narrow size distributions of both fine and coarse particles may be generated by water atomization. A review of published data for droplet size distributions generated by gas and water atomization of a variety of liquid metals and alloys has been made by Lawley,[4] along with presentations of micrographs of surface morphology and internal microstructure of solidified particles. 

TEM utilizes an image formed by an electron beam that passes through the sample. This allows internal microstructures to be determined. Structural details of materials can be observed on an atomic level by looking at contrasts in the image caused by various concentrations of different elements. Very thin films are employed. Under good conditions, magnifications up to 1 million are possible employing TEM. 

A material can change its morphology—its external macroscopic shape and its internal microstructure—when suitable driving forces exist. As always, these driving forces result from differential decreases in total free energy. 

A.N. Bens and S.J. Edwards, Thermodynamics of Flowing Fluids with Internal Microstructure, Oxford University Press, New York (1994). 

A study of the effects of several different plasticisers on the density, elasticity and degree of expansion of foams, produced from different PVC plastisols, has been reported (120). A three-dimensional and high resolution quantitative image technique has been proposed for the investigation of the internal microstructure of foams. This provides a tool to study the relationships between foam structure and physical properties (18). 

Summing up the above mentioned, the mechanism of formation of the interned microstructure of the "rubber phase particles after the inversion of phases can be represented in the following weiy ... 

Kobayashi, I., 1969. Internal microstructure of the shell of bivalve molluscs. Am. Zool., 9 663-672. 

Rheology is increasingly being coupled to other analytical test methods for more comprehensive material characterizations. Many of these developments are driven by research needs for broadened characterization capability. For fundamental studies of detergent systems this offers a broad suite of methods to probe surfactant mesophases and internal microstructure. 

Electron microscopy has been employed to identify the locations, sizes, and number of granules in cyanobacteria. This technique revealed interesting observation whereby the number and sizes of PHA granules were comparable to that of some PHA-producing bacteria (Sudesh et al. 2001). In addition, freeze-fracture electron microscopy observation on Synechocystis sp PCC 6803 showed that the internal microstructure of P(3HB) was essentially similar to the P(3HB) granules... 

Type 111 belite, the nonlamellar form, is uncommon in normal plant clinkers and is merely a single crystal with a uniform internal microstructure. 

Belite crystals with an internal microstructure of lamellae arranged in a concentric hexagonal pattern are rare. 

A classification of belite, based on internal microstructure, is proposed by the present writer. 

Photograph 7-39 Gamma belite fragment in thin section. Note semisplintery fracture and internal microstructure. (S A6659)... 

It is known that a viscoelastic fluid, e.g., a solution with a trace amount of highly deformable polymers, can lead to elastic flow instability at Reynolds number well below the transition number (Re 2,000) for turbulence flow. Such chaotic flow behavior has been referred to as elastic turbulence by Tordella [2]. Indeed, the proper characterization of viscoelastic flows requires an additional nondimensional parameter, namely, the Deborah number, De, which is the ratio of elastic to viscous forces. Viscoelastic fluids, which are non-Newtonian fluids, have a complex internal microstructure which can lead to counterintuitive flow and stress responses. The properties of these complex fluids can be varied through the length scales and timescales of the associated flows [3]. Typically the elastic stress, by shear and/or elongational strains, experienced by these fluids will not immediately become zero with the cessation of fluid motion and driving forces, but will decay with a characteristic time due to its elasticity. 

This discussion of chemical stability refers to bare (uncoated) glass fibers, i.e., fibers having neither a specific acid or alkali resistant finish nor a secondary coating. Accordingly, the relationship between fiber composition and chemical stability in water, acids, and bases is complex. It depends on the interaction between (1) the chemical agent [27] to which the glass fiber surface is exposed, (2) foe pH of the glass composition [33] in the fiber surface, and (3) the internal microstructure of foe fiber [27]. 

In summary, the effect on the pH of the bare fiber surface and the effect of the interaction between a chemical agent and a bare fiber surface are predictable. ZrC>2 seems to increase both acid and base resistance. The effect of the internal microstructure [27] of a fiber is highly process dependent and not predictable without a thorough prior investigation of its microstructure. Importantly however, all fibers, except experimental single fibers, have a primary finish some have an additional secondary coating. These modifications further reduce the predictability of their chemical resistance from their compositional make-up alone. 

Upon reflection, one concludes that it is rather unlikely that individual laboratory microreactors will be coimected in this way in industrial designs. More likely is that large-scale macro-devices will be created with internal microstructuring and it is not evident that such devices will truly operate under identical conditions at all points in the intercoimected structure. Numbering-up is therefore not the complete answer to the scale-up problem, but it does provide a stimulating model for a totally new way to design and construct reactor devices. 

Another effect of the power law behavior of these dense systems is that they deviate positively from Porod s law (/ cx which may be considered as a general rule for this kind of solid. This is induced by density fluctuations within the phases due to their internal microstructure of them. 

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