Optical texture domains

Figure 2.9. Optical micrograph of polished surfaces of an anisotropic carbon of large optical texture, domains, sizes of >20 (jim. The size of the image of the micrograph is 30 X 60 p,m.

Figure 6. Optical micrograph of a coke surface showing an optical texture of domains, >60 ym, OTI 30.

As the pyrolysis of model, polynuclear hydrocarbon compounds represents, possibly, the ultimate in ability to form the largest and most stable of mesophase molecules leading to the domains (Table 1) of optical texture in cokes, then smaller sizes of optical texture can be explained by processes which restrict or inhibit polymerization to larger molecule sizes. Conversely, it may be possible to increase the size of the optical texture of coke by suitable ameliorative treatments to a pitch. 

System B pyrolysis of coal-pitch blend with good modification of coal by pitch to give coke with coarse-grained mosaics, <10 pm diameter System C pyrolysis of pitch to give coke with optical texture of domains >60 pm diameter, (See Ref, 44). 

Authigenic albite occurs as discrete euhedral crystals (10 pm), overgrowths on detrital feldspars, and most commonly as replacement of detrital K-feldspar and plagioclase in the proximal and middle domain. K-feldspar grains in these areas commonly show partial albitization, whereas the detrital plagioclase is totally replaced by albite. Albitized feldspar grains display the typical optical, textural and chemical characteristics outlined by... 

Breeze Additives. Optical microscopy of the Six Bells (CR 301a), Cortonwood (CR 401) and Maltby (CR 502) cokes with the A170 pitch coke breeze additives shows that the breeze additives with predominantly flow domain anisotropy optical texture are easily distinguishable from the surrounding coal coke of predominantly fine-grained mosaics. The effect of carbonization to 1200 K upon the petroleum coke breeze is to increase progressively the number and size of fissures within the breeze particles. 

Fig. 7.4 Crossed polarized optical textures of 14 (a 5 pm, c 9 pm, e 20 pm thick) and its corresponding non-fluorinated counterpart 13 (b 5 pm, d 9 pm, f 20 pm thick) at room temperature. The dark areas represent homeotropic alignment, and the bright domains appear where the porphyrin planes are oblique to the substrate. Reproduced with permission from [107]. Copyright 2009 Taylm- Francis...

Hwang, D. K., and A. D. Rey. 2006. Computational studies of optical textures of twist disclination loops in liquid-crystal films by using the finite-difference time-domain method. J. Opt Soc. Am. A. 23(2) 483. 

The appearance of focal conic structures depends on the direction of viewing. When the epitaxial interactions between the mesophase and the substrate surface, cause the axes of the focal conic units to lie vertical, the polygonal texture appears (Figs. 1.23 and 1.24). On the other hand, samples with focal conic units lying obliquely to the viewing direction, give the characteristic fan texture (Fig. 1.25). [A note of caution for decades, when faced with an undecipherable optical texture with a jumbled mass of domains, workers in the liquid crystal field have often taken the easy option and simply called it a focal conic fan texture to disguise the fact that they had no idea what it was. They have usually been correct, but not always, and mesophases of very different structures have been seriously misidentified on more than one occasion.]... 

Under an optical microscope with crossed polarizers, the LC-forming OPV5s show isolated droplets and extended domains having the typical Schlicren texture... 

Both tilt domains in the green stripe texture switch to the same ferroelectric state in this process, thus causing the stripes to disappear. The anticlinic structure is SmA-like in the sense that the average optic axis is along the layer... 

However, if an LC substance is heated, it will show more than one melting point. Thus, liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid and a solid crystal. For instance, an LC may flow like a liquid but have the molecules in the liquid arranged and/or oriented in a crystal-like way. There are many different types of LC phases that can be distinguished based on their different optical properties (such as birefringence). When viewed under a microscope using a polarized light source, different liquid crystal phases will appear to have a distinct texture. Each patch in the texture corresponds to a domain where the LC molecules are oriented in a different direction. Within a domain, however, the molecules are well ordered. Liquid crystal materials may not always be in an LC phase (just as water is not always in the liquid phase it may also be found in the solid or gas phase). 

Fig. 2 Polarizing optical micrographs in the B4 phase of bent-core LC. Under crossed polarizers, texture with bluish color is observable (middle). By decrossing polarizers, two brighter and darker domains are observable (right and left). The brightness is interchanged by decrossing polarizers to counter senses [11]...

A conglomerate in real liquid crystalline phases was first observed in the smectic phase of a rod-shaped mesogen with two stereogenic centers in its tail [42], We used a racemic mixture which was supposed not to electrically switch. Evidence for conglomerate formation was provided by clear electro-optic switching and texture observation under a polarizing microscope domains with stripes, which themselves display fine stripes. These stripes are tilted in two different directions with respect to the primary stripes. This is a still very rare example now that fluid soft matter is known to resolve spontaneously into a three-dimensional conglomerate. 

The optically anisotropic textures of mesophase from the samples heat-treated at the early stages of carbonization are classified into five types corresponding to isotropic, fine mosaic, coarse mosaic, fibrous, and domain. 

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