Wide Angle Diffraction

Electron diffraction Wide-angle x-ray scattering Electron microscopy Density... 

X-ray diffraction. Wide-angle x-ray diffraction (WAXD) patlmis were obtained on aScintagPAD5instrumaitinreflectitmmodewidifiltmedCuKaradiation. Thedata... 

Temperature programmed desorption Transmission electron microscopy X-ray absorption fine structure X-ray diffraction (wide-angle X-ray diffraction)... 

X-ray scattering techniques are the most commonly applied complementary discipline to microscopy for structural studies. The type of information that is obtained by x-ray scattering experiments includes phase identification and quantification, crystallinity, crystallite size, lattice constants, molecular orientation and structure, molecular packing and order, and amorphous structure [26-30]. Diffraction techniques that will be described include powder diffraction, wide angle x-ray scattering (WAXS), and fiber diffraction. Small angle x-ray scattering (SAXS) will be described in Section 7.4.4. 

The most widespread technique of structural investigations of cellulose certainly is the X-ray diffraction. Wide-angle X-ray scattering (WAXS) is one of the few methods allowing determination the absolute degree of crystallinity. However, the determination of the actual crystallinity degree is laborious and complicated procedure, and therefore most researchers are limited by a more simple way-estimation of index of ciystallinity, Crl (Park et al., 2010 Terenlte et al., 2011). 

FIG. 33 X-Ray Diffraction Patterns of Ammonium Dodecane 1-Sulfonate. 2-D (a) and 3-D plots (b) of oriented samples. Both pictures show the presence of a nonordered smectic phase, since the diffuse, weak, wide-angle diffraction indicates only an average distance between the molecules and the sharp, intense small angle reflections a very well defined layer distance. The reflections are perpendicular to each other, so the structure should correspond to an orthogonal smectic A type. The pictures were obtained using an x-1000 area detector from Siemens. 

X-ray diffraction has been employed for a very long time to attempt to characterize supported catalysts. For the most part, and until recently, only the width of a wide-angle peak has been employed. From the Scherrer equation, this width yields a "size". However, it has not been recognized that such a procedure faces many problems ... 

Other information that can be obtained from a wide-angle diffraction pattern includes the detection of stacking faults and microstrains, the lattice parameters, and the mean-square amplitude of vibratioiu... 

Figure 1. Wide angle X-ray diffraction pattern from PET films exposed to DMF at various temperatures for 15 min.

Figure 5. Room-temperature, wide-angle X-ray diffraction (WAXD) pictures of stretch-oriented samples of PDHS (left) and PDPS (right).

A Siemens Kratky camera system was utilized for small angle x-ray scattering (SAXS) measurements in conjunction with an M. Braun position sensitive detector from Innovative Technology Inc.. Wide angle x-ray diffraction was obtained utilizing a Philips table-top x-ray generator. 

Figure 7.12 Wide-angle X-ray diffraction spectrum from high density polyethylene...

Figure 7 Plot of the degree of crystallinity (XNMR) by obtained by BC NMR against crystallinity (Xx.ray) obtained by wide angle X-ray diffraction for an unfractionated linear polyethylene sample crystallized in different conditions (data from Ref. [129]).

Classical X-ray diffraction and scattering is carried out in the subarea of wide-angle X-ray scattering (WAXS). The corresponding scattering patterns yield information on the arrangement of polymer-chain segments (e.g., orientation of the amorphous phase, crystalline structure, size of crystals, crystal distortions, WAXS crystallinity). 

Application. Anomalous X-ray diffraction (AXRD), anomalous wide-angle X-ray scattering (AWAXS), and anomalous small-angle X-ray scattering (ASAXS) are scattering methods which are selective to chemical elements. The contrast of the selected element with respect to the other atoms in the material is enhanced. The phase problem of normal X-ray scattering can be resolved, and electron density maps can be computed. 

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