Powder X-ray diffraction diagram

The reactants should be powdered and intimately and stoichiometrically mixed and heated. Then they should be thoroughly pulverized and heated a second or even a third time the advance of the reaction can be checked from the powder X-ray diffraction diagram, although the method is of low accuracy for... 

Little is known about the crystal structure of disazo condensation pigments. Some powder X-ray diffraction diagrams have, however, been published, in particular for Pigment Yellow 94, Orange Red 166 and 242 and Brown 23 . No single crystal struc-... 

Fig. 7.12 Phase separation in Li MoeSej. (a) Powder X-ray diffraction as a sample with X = 0.5 is cooled, (b) Phase diagram inferred from results of (a) and other Bragg peaks. The dashed line in (b) shows the path followed in the measurement of (a). Data from Dahn and McKinnon (1985).

After the required reaction time, the gel mixtures were cooled, centrifuged, and washed three times with more than a tenfold quantity of distilled water. After drying at 105°C, the products were powdered if necessary. X-ray diffraction diagrams were recorded (Cu Ka radiation), and the phases present were identified by comparing their diffraction peaks with published d values or with those of standard zeolite diffraction diagrams. The quantity of each species was estimated within 5% from relative peak heights compared with the best of their kind, which were also selected for a more detailed crystallographic examination. 

The variation in activity for acrylonitrile formation as a function of composition for the 2-x x % 12 shown in Figure 4. Maxima in activity, as measured by first order rate constant for propylene disappearance, occur at three compositions. A partial phase diagram for the system, constructed with powder x-ray diffraction is displayed in Figure 5. 

More recently, the phase diagram of a PEO system containing a divalent cation, PE0-Ca[CF3S03)2 has been elucidated by Bruce and coworkers by using variable temperature powder X-ray diffraction (VTXRD) and differential scanning calorimetry (DSC). A 6 1 complex has been shown to form with two polymorphic phases [63]. Figures 2,3 and 4 show representative examples of the phase dia-... 

Fig. 52. X -ray diffraction diagram of the powdered magnetite from Grangesberg, Sweden. Besides magnetite (Fe304) the sample contains some hematite (Fe203R siderite (FeC03),...

Saha et. al. [4] and Holbrey et. al.[31] that bmimCl crystal shows two crystal polymorphism. Schematic diagram of bmim cation has been presented in Figure 1. In crystal 1 (Figure 2a), the /i-butyl group takes trans-trans (TT) conformation with respect to Cy-Cg and C8-C9 bonds, while in crystal 2 (Figure 2b), n-butyl group takes gauche-trans (GT) conformation with respect to Cz-Cg and Cg-C9 bonds similar to that of bmimBr conformation. [4, 25] Powdered x-ray diffraction patterns of the two polymorphs of bmimCl and bmimBr was recorded and found that the pattern for crystal 2 and bmimBr somewhat resembles each other, while that of bmimCl crystal 1 is distinct from the other two. [4,21]... 

Phase diagrams have been determined for sections of the i -Bi-Se R = Ce, Sm, Tm) systems as a function of composition and temperature, through powder X-ray diffraction, differential thermal analysis, microstructural analysis, and microhardness measurements. 

Fig. 93 shows the reflection angles of the a-, (3-, and y-crystal modifications. The measurements were carried out on powder diagrams derived from X-ray diffraction spectra. 

Phthalocyanines exhibit high polymorphism, as well [7]. They are insoluble nano crystalline materials, which produce poor x-ray powder diagrams with high preferred orientation and have been intensely investigated by electron microscopy and diffraction [8]. From copper phthalocyanine (CuPc) (Fig.2) nine polymorphs (a, P, y, 5, s, n, p, (, a and R) are known, but only the most stable P phase could be solved by single crystal x-ray diffraction [9] (P2i/c a=14.628 A, b= 4.790 A, c= 19.07 A, b=120.93°). 

These considerations lead us to propose the tentative phase diagram of fig. 28. The orthorhombic-rhombohedral transition has been tracked by Wold and Arnott (1959). The two-phase region 0.05 < 5 < 0.10 observed by room-temperature X-ray diffraction has been shown from the spin-glass behavior below 7 to extend over a wider compositional range below 200 K, which indicates that a spinodal phase segregation separates the O -orthorhombic (c/a < x/2) from an O -orthorhombic (c/a J2) or R-rhombohedral phase. With neutron powder diffraction, Huang et al. (1997) have shown the two-phase region at 300 Kin the inter-... 

X-ray diffraction (in crystalline polymers) Unoriented crystalline polymers show X-ray diffraction patterns, which resemble powder diagrams of low-molecular crystals, characterised by diffraction rings rather than by spots. As a result of orientation the rings contract into arcs and spots. From the azimuthal distribution of the intensity in the arcs the degree of orientation of the crystalline regions can be calculated (Kratky, 1941). 

The deformation of the lattice as a result of the mechanical working is seen from the broadening of the lines in the X-ray diffraction picture, which are narrow under normal circumstances (Debye-Scherrer or powder diagram). 

B. O. Cullity and S. R. Stock, Elements of X-Ray Diffraction , 3rd Edition, Prentice Hall, Upper Saddle River, 2001, Excellent treatment of powder methods in general. Includes phase-diagram determination, polycrystalline aggregates, polymers, quantitative analysis and stress analysis. 

X-ray diffraction. The X-ray dif action diagrams were obtained on powder with the particles oriented so as to inerease the intensity of the (001) reflection. The apparatus used was a Philips PW-1710 diffractometer with CuKa radiation. 

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