Texture scattering

X-ray diffraction consists of the measurement of the coherent scattering of x-rays (phenomenon 4 above). X-ray diffraction is used to determine the identity of crystalline phases in a multiphase powder sample and the atomic and molecular stmctures of single crystals. It can also be used to determine stmctural details of polymers, fibers, thin films, and amorphous soflds and to study stress, texture, and particle size. 

Complete scattering patterns of samples with a complex single-crystal anisotropy can only be recorded in a texture setup (Chap. 9, Fig. 9.3). The samples must be rotated in order to scan the required fraction of reciprocal space. 

Complex Anisotropy is studied in texture goniometers (p. 193) as a function of sample orientation. If the study is aiming at quantitative analysis of scattering data, the absorption correction may become an issue. Conversely, by choosing a special kind of scanning modus (e.g., symmetrical reflection SAXS SRSAXS), the absorption correction problem can be simplified. 

In general, it is not recommended to study WAXS crystallinity of anisotropic materials. The recording of the corresponding data is laborious, because the WAXS must be recorded as a function of both scattering angle and sample orientation in a texture goniometer (cf. p. 193, Fig. 9.3) before the data can be isotropized. 

Whenever we are considering orientation, we are dealing with anisotropic scattering data. Orientation is most frequently analyzed in 2D scattering data with fiber symmetry or in pole-figure data recorded by means of a texture goniometer. 

Figure 9.3. Scattering geometry for the measurement of pole figures in a texture goniometer. The scattering angle 20/,/./ is fixed, (p and (// are scanned...

Nevertheless, there has been a renewed interest in Raman techniques in the past two decades due to the discovery of the surface-enhanced Raman scattering (SERS) effect, which results from the adsorption of molecules on specially textured metallic surfaces. This large enhancement was first... 

Another technique widely used to measure the cholesteric pitch is based on the Bragg scattering of monochromatic light (obtained by a helium-neon laser) from fingerprint or planar textures of the cholesteric32 Its angular dependence is strictly related to the cholesteric pitch. 

Figure 9. Formation of circular scattering regions (rings) in the reciprocal lattice of a texture, and relationship between their shape and the structure of the specimen. Transition from a point to a ring (a) for an ideal texture without disorder (c), having a distribution function (e) (d), (f) - corresponding diagrams for a real texture with some disorder.

Figure 10. Distribution of reciprocal lattice points of a plate texture along straight lines parallel to the texture axis and perpendicular to the face lying on the support (a) and distribution of circular scattering regions of the reciprocal lattice of a texture on coaxial cylinders.

Figure 11. (a) formation of layer lines in the reciprocal lattice of a texture for a orthogonal unit cell, (b) the doubling of number of circular scattering regions in the reciprocal lattice of a texture and therefore the number of reflections on an ellipse of a pattern for a non-orthogonal unit cell, (c) measurement of a values of 2r and 2 D on a texture pattern. 

Unfortunately, these rock textures are relatively coarse compared to the size of the slabs used in classification (Duncan 1999). Thus, representativity is low, likely explaining why these image analysis results exhibit high scatter in Fig. 2. 

MSA. Static and dynamic scattering are reported on a nematic phase with a smooth texture, and the... 

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