Extended X-ray absorption line structure

EXAFS Extended X-ray absorption line structure Estimation of intemuclear distances around a central atom... 

Cp Ti(OMe)3, reacted mixtures of Cp Ti(OMe)3 and TIBA, and reacted mixtures of Cp Ti(OMe)3, TIBA, and MAO are examined by X-ray absorption near-edge structure (XANES) and extended X-ray absorption line structure (EXAFS) analysis. Rgure 4.11 shows the results of these measurements [23]. 

Another contribution to variations of intrinsic activity is the different number of defects and amount of disorder in the metallic Cu phase. This disorder can manifest itself in the form of lattice strain detectable, for example, by line profile analysis of X-ray diffraction (XRD) peaks [73], 63Cu nuclear magnetic resonance lines [74], or as an increased disorder parameter (Debye-Waller factor) derived from extended X-ray absorption fine structure spectroscopy [75], Strained copper has been shown theoretically [76] and experimentally [77] to have different adsorptive properties compared to unstrained surfaces. Strain (i.e. local variation in the lattice parameter) is known to shift the center of the d-band and alter the interactions of metal surface and absorbate [78]. The origin of strain and defects in Cu/ZnO is probably related to the crystallization of kinetically trapped nonideal Cu in close interfacial contact to the oxide during catalyst activation at mild conditions. A correlation of the concentration of planar defects in the Cu particles with the catalytic activity in methanol synthesis was observed in a series of industrial Cu/Zn0/Al203 catalysts by Kasatkin et al. [57]. Planar defects like stacking faults and twin boundaries can also be observed by HRTEM and are marked with arrows in Figure 5.3.8C [58],... 

There are two very general X-ray techniques for study of the metal particle size distribution the line-broadening analysis (LBA) and the small angle X-ray scattering (SAXS) (lb, 170). Other methods include the radial electron distribution (RED) and the extended X-ray absorption fine structure (EXAFS), which are aimed primarily at studying the structure of catalysts (Section IV,G). 

Measurements using extended x-ray absorption fine-structure (EXAFS) spectroscopy were made on the insertion-device beam line of the Materials Research Collaborative Access Team (MRCAT) at the Advanced Photon Source, Argonne National Laboratory. Measurements were made in transmission mode with ionization chambers optimized for the maximum current with linear response ( 10 photons detected/sec). A cryogenically cooled double-crystal Si (111) monochromator with resolution (AE) better than 2.5 eV at 11.564 keV (Pt L3 edge) was used in conjunction with a Rh-coated mirror to minimize the presence of harmonics [9]. The integration time per data point was 1-3 sec, and three scans were obtained for each processing condition. 

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