Ray Diffraction and Absorption

The distribution of orientation N(y) of a given reflection may be reconstructed by insertion of the (Pf)hki coefficients in the relation  

Although the (P2) coefficient is a convenient index to characterize the orientation and is commonly measured by WAXD for semicrystalline polymers, it is only an average value and different distributions of orientation could give the same (P2) coefficient (Section 2). It has been shown that higher (P ) coefficients are required to fully characterize the distribution of orientation [83]. This is 

As seen in this chapter, the theory and procedures for orientation measurements are well established, including for quantitative characterization. These methods can provide very accurate and useful information in the fields of synthetic, natural, and bio-inspired macromolecules. To this aim, researchers can make use of a wide range of techniques, each having its advantages and limitations. As judged from the recent literature, the studies devoted to the quantification and characterization of molecular orientation still represent a very dynamic research field and advances still continue to emerge. Further progresses in the development of new methods and new techniques to characterize orientational order are thus expected in the future. 

Lagugne-Labarthet, T. Buffeteau and C. Sourisseau, Appl. Spectrosc., 54 (2000) 699-705. H. Pottel, W. Herreman, B.W. Ven der Meer and M. Ameloot, Chem. Phys., 102 (1986) 37-44. 

Structure and Properties of Oriented Polymers, 2nd ed., Chapman Hall, London, 1997. 

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However, time-resolved X-ray diffraction remains a young science. It is still impossible, or is at least very difficult, to attain time scales below to a picosecond. General characteristics of subpicosecond X-ray diffraction and absorption are hardly understood. To progress in this direction, free electron laser X-ray sources are actually under construction subject to heavy financial constraints. Nevertheless, this field is exceptionally promising. Working therein is a challenge for everybody ... 

M. M. Gunter, T. Ressler, R. E. lentoft, and B. Bems, Redox behavior of copper oxide catalysts in the steam reforming of methanol studied by in situ X-ray diffraction and absorption spectroscopy, J. Catal. 203, 133-149 (2001). 

Application of Combined X-Ray Diffraction and Absorption Techniques for in Situ Catalyst Characterization... 

X-ray diffraction and absorption techniques have rarely been used to investigate time-dependent changes. However, it will be shown that the techniques may also be used to characterize the dynamics of catalytic processes (Sections IV-VII), and in recent years the time resolution has improved by several orders of magnitude. This improvement has opened the door to new types of quantitative studies of the dynamical behavior of catalysts, and such information is often necessary for a detailed description and understanding of catalytic phenomena. Some possible future applications and advances in the techniques are summarized in Section VII. 

Clausen BS, Topsoe H, Frahm R. Application of combined X-ray diffraction and absorption techniques for in situ catalyst characterization. Adv Catal. 1998 42 315. 

A variety of experimental techniques have been used to investigate IL structures. Neutron diffraction, X-ray scattering, extended X-ray absorption fine structure (EXAFS) [97-105], and theoretical methods [64, 106-111] are probably the most powerful approaches to quantify IL structure and interactions. For example, X-ray diffraction and absorption studies along with computer simulations have shown that ILs are by no means molecular liquids [64, 89,94,112,113], Unlike a conventional solvent like hexane or chloroform, ILs contain a large number of internal interfaces and exhibit different degrees of order [89, 114], ILs can form liquid crystals, extended hydrogen-bonded networks, inclusion compounds, or microphase separated structures, where polar and non-polar regions are separated by a complex interface [86, 89, 114],... 

Using different characterization techniques, such as x-ray diffraction and absorption spectroscopies, Chouillet et al. [51] concluded that in Zn/SiOj supported catalysts, the formation of ZnO (the active form of the catalyst) strongly depends on the drying temperature. The active form of the catalyst was obtained only when the catalyst was dried at intermediate temperatures (between 90 and 150°C). Slow and fast drying did not allow the formation of the active form. 

Nam K-W et al (2013) Combining in sim S5mchrotron X-ray diffraction and absorption techniques with transmission electron microscopy to smdy the origin of thermal instability in overcharged cathode materials for lithium-ion batteries. Adv Eunct Mater 23 1047-1063... 

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