Powder XRD

Treacy M M J, Fliggins J B and von Ballmoos R 1996 Collection of Simulated XRD Powder Patterns for Zeolites 3rd revised edn (London Elsevier)... 

Fig. 1. Quantification of framework Ti sites and unit cell expansion versus Ti contents using XPS 2p transition lines ( O ). XANES profiles at Ti K-edge (A) and Rietveld refinement of the XRD powder patterns ( ). Solid data points for TS-1 prepared as in ref [9].

Role of the organic feed XRD powder patterns and FT-IR spectra confirmed that pure MFI-type Ti-silicalite (TS-1) was obtained [18-23], with a surface area of 530 m g". FT-IR spectra of adsorbed pyridine (Fig. 39.2) showed the presence only of weak Bronsted and Lewis sites [24,25], as confirmed by the complete evacuation from the surface at 373 K. 

The analytical power of XRF and XRD has lately been combined in an integrated XRF/XRD system, in which XRD powder measurements are examined for phase identification and Rietveld analysis on the basis of element concentrations. Process analysis, a former stronghold of XRF, can now be performed by highspeed XRD, which is supported by XRF element-analytical data. 

The XRD powder patterns of the two catalysts were not significantly different, both showing mainly the pattern of the support (y-Al203) together with the presence of metallic Rh (29 41°). Also the main chemical-physical... 

XRD powder patterns of fresh and used catalysts, measured at room temperature on a Bruker D8 Advance diffractometer equipped with Sol-X detector, were subjected to Rietveld structure refinement in Immm space group using the GSAS package (Larson and Von Dreele, 1994). 

The XRD powder patterns of the anhydrate and trihydrate phases of ampicil-lin are shown in Fig. 5. The nonequivalence in the crystal structures is immediately evident from a comparison of the powder patterns. It is also known that amoxicillin trihydrate is isomorphous with ampicillin trihydrate [39], and a comparison of the corresponding powder patterns demonstrates the equivalence of the structures. 

Differential scanning calorimetry can also supply valuable information regarding solvate species, and it is particularly useful with respect to temperature and energetics of the desolvation process Two samples of the developmental compound L-706000-001T were shown to be chemically identical, and each contained two moles of water. The XRD powder patterns for the two samples were found to be quite different, demonstrating the existence of polymorphism... 

These nitridooxophosphates are stable in water and 1 N HC1, which is useful to extract eventual by-products. Their composition has been undoubtedly established by a complete chemical analysis. The XRD powder patterns can be indexed with hexagonal parameters (Z = 6) as illustrated for the potassium compounds ... 

FIGURE 2.8 XRD powder pattern of highly crystalline thick-film PFO 196 specimen after extended heat treatments at elevated temperatures and stepwise cooled to room temperature. (From Chen, S.H., Chou, H.L., Su, A.C., and Chen, S.A., Macromolecules, 37, 6833, 2004. With permission.)... 

D) We have found fhaf fhe mefhod of Wakelin et al. (1959), as used by Nara et al. (1978) fo calculafe fhe % relative crystallinity, is a reliable and reproducible procedure to determine the degree of gelatinization of sfarch by XRD powder diffracfomefry. This procedure, however, is nof sfraighfforward and needs suifable reference samples for 100% crysfalline and 100% amorphous material, and appropriate computer software to analyze data. 

Fig. 32 [92,206,258] one is based on a hexagonal supercell with a = Iuq and the other is based on an orthorhombic supercell with a = aoV and b = luo-Hofmeister and von Platen [92] simulated the XRD powder patterns for a variety of LDHs with different metal ions, stoichiometries and stacking... 

The XRD powder patterns of V-containing silicalite samples indicate in all cases the presence of only a pentasyl-type framework structure with monoclinic lattice symmetry, characteristic of silicalite-1 no evidence was found for the presence of vanadium oxide crystallites. The analysis of cell parameters of VSU545 does not indicate significant modifications with respect to those found for pure silicalite-1. This is in agreement with that expected on the basis of the small amount of V atoms present in V-containing silicalite. 

Figure 1 exhibits the XRD powder patterns of fresh HT s they present the characteristic reflections corresponding to a hydrotalcite-like structure. 

Figure lb exhibits the XRD powder patterns of NbMCM-41(52) and TaMCM-41(52) in comparison to all-silica MCM-41. The quality of the XRD patterns decreases with increasing metal content of the samples (not shown). 

Characterization.— The LSFTO powder was calcined at a series of temperatures (1250, 1300, and 1400°C) in air to investigate phase purity and densification behavior. X-ray diffraction (XRD) powder patterns are shown in Fig. 1. The sample is single phase after heating at 1250°C. At the higher sintering temperatures, the lines become sharper and the density increases. The density measured by the Archimedes method was 90.3% relative to theoretical value after annealing at 1400°C for 10 h. The XRD pattern sintered at 1400°C was completely indexed with a cubic unit cell with lattice parameter a = 3.898(8) A and V= 59.2(6) A3. The weak XRD peaks at 31, 43, 55, and 65° 20 are also from the perovskite phase and arise from a small amount of WL radiation in the incident beam. 

In Figure 3.13, the XRD powder patterns of the transformation products, Na-FCSW(6h) (Figure 3.13a), Na-FCSW(12h) (Figure 3.13b), and the pattern of the Na-Y commercial sample CBV100 (Figure 3.13c), with Si02/Al203 = 5.2, provided by the PQ Corporation Malvern, PA, USA, which was used as a standard for comparison, are shown [126], The XRD powder patterns show that the transformation products are Na-faujasite zeolites, with 80% crystallinity compared with the standard (CBV-100). The analysis by x-ray diffraction of all the samples lets us confirm that the maximum yield of the hydrothermal transformation procedure was achieved at approximately 9h. 

FIGURE 4.4 XRD powder diffraction pattern of a BaCe095Yb005O3 5 perovskite. 

This sample was acid leached in 0.5,1.0, and 5.0M HC1 solutions (liquid/solid = 20) for 2h, and the XRD powder profile was registered. In Table 4.5, the cell parameters showing the changes in the orthorhombic lattice of the MOR framework of the zeolite MP are reported [44],... 

Elemental analyses were carried out by using X-ray fluorescence (XRF Si, Al) and combustion (C, H, N) methods. X-Ray diffraction (XRD) powder spectra were recorded on a Philips PW 1130 instrument. 

A brief review of the diffraction phenomenon and the effect of crystallite size is presented. Applications of XRD to catalyst characterization are illustrated, including correlation of XRD powder patterns to molecular structural features, determination of Pt crystallite size and others. Factors that affect the appearance of XRD powder patterns, such as framework structure perturbations, extra-framework material, crystal morphology, impurities, sample preparation, instrument configurations, and x-ray sources, are discussed. 

In fact, peak broadening is just one of several effects observed in XRD powder patterns that can be used to gain characterization information about various catalyst systems. Particularly in zeolite systems, factors such as framework structure perturbations and modifications, extra-framework material, crystal morphology, impurities, and instrument configurations can produce observable differences in the XRD patterns, which require close scrutiny, in some cases, to understand and utilize. 

In addition, structural similarities can often be determined from careful interpretation of XRD powder patterns. The powder patterns of offretite and erionite look quite different, but are easily understood in terms of the crystallographic consequences of a change in the ordered layer stacking sequence (11), cf. Figure 4. In offretite, the layers are stacked in an AAB sequence, while in erionite, they are ordered in an AABAAC arrangement that doubles one of the crystallographic unit cell parameters. The doubled c-parameter is readily deduced from an analysis of the XRD powder pattern of erionite. Another framework structure effect, isomorphous substitution, can result in changing unit cell sizes, observed as shifts in XRD line positions for such systems as X and... 

Figure 3. Structural symmetry changes can affect XRD powder patterns. Additional peaks observed in a ZSM-5 XRD pattern indicate a symmetry reduction from orthorhombic (as-made) to monoclinic (calcined/ammonium-exchanged). Reproduced from ref. 10. Copyright 1979 American Chemical Society.)...

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