Optical microscopy packing

Mechanistic investigations of gas-solid and solid-solid reactions as well as their proper engineering require identifiable crystal surfaces for atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) [1,3, 13-15] in combination with X-ray diffraction data, which are the basis of crystal packing analyses [1,3,16-18]. 

Just as polarized light enhances the utility of optical microscopy in the study of polymorphic systems, so polarization can be used in conjunction with IR spectroscopy. As we shall show later in greater detail (see Section 6.3.2) polarized spectroscopic methods provide detailed information on the directional properties which distinguish the spectral features of polymorphs. Thus, for instance, the directional properties of a polymorphic transformation of fatty acids (Kaneko et al. 1994a-c) and inferences about the differences in packing modes (Yano 1993) have been investigated with polarized IR methods. 

Jaffe melted and isothermally recrystallized fibers spun under different stress levels. The bulk crystallization kinetics was measured with both DSC and optical microscopy techniques. Table 3.30 lists the samples studied. The film samples were included to ensure the absence of spurious DSC effects due to fiber packing. The samples were heated from 50°C to the melt temperature at 80°C/min. The melt temperatures ranged from 170 to 230°C. The samples were held in the melt for a specified time and then cooled to the 130°C crystallization temperature at 40°C/min. 

The structure and morphology of fibers and films can be described at various levels of structural dimensions, depending on the resolution of the diffraction equipment and of the microscopes used in the investigation. First of all the chain conformation in the solid state is discussed, then the packing modes of the chains in the crystallites determined by X-ray diffraction are reviewed, next the structural characteristics of the fibrils observed by X-ray and electron diffraction are examined, and finally the morphological features as seen by electron and optical microscopy are dealt with. After this survey of the structure and morphology, the formation of the fiber and film by coagulation from a lyotropic solution is discussed. 

The cross-section of the above specimens was further investigated to determine the changes in the fiber morphology as well as the fabric properties. In the cross-sectional study, both warp and weft yams of the specimens were carefully removed from the fabric, and then investigated by a traditional optical microscopy and a SEM. In the optical microscope, the sample was prepared by procedures described in standard AATCC20 a bundle of yams were used to pack the hole of a stainless steel plate, then a sharp razor blade was used to produce a smooth cut on both sides of the plate (AATCC, 2004). The steel plate was then examined by a transmitted light microscope with magnification of 500 x. 

Liquid crystal materials may exhibit birefringence (discussed in Section 2.5), so polarized optical microscopy is an ideal technique for visualization of liquid crystal textures. Samples are prepared as a thin film ( 2-20 pm thick) between glass plates. By observing the interesting defect textures that may form in each phase, it is often possible to make accurate phase identifications by microscopy alone, even though the microscope is unable to resolve the actual molecular packing structure. 

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