Ray Diffraction XRD

X-Ray diffraction (XRD) is the principal means of determining the structures of crystals. It is a technique in which a collimated X-ray beam is directed at a single crystal of the material under investigation or, as is more usual in the study of fat crystals, a sample comprising a large number of randomly orientated crystals. The latter variant, which is the most commonly used generally, is called powder diffraction (Cullity, 1956). Both variants yield essentially the same basic information about structure after data analysis. The following descriptions relate to powder diffraction specifically. 

By far the greater proportion of incident X-radiation is transmitted by a crystalline sample. However, a small fraction is scattered (effectively reflected) in all directions by every motif in the material, without change in wavelength. The motif is the repeating unit of pattern in a crystal it is the TAG molecule in the case of a fat crystal. Motifs can be considered to be located at or near the intersections of an imaginary 3-dimensional grid called the crystal lattice and the intersections are called lattice points (Hammond, 1997). 

The scattered X-rays mutually interfere, either destructively or constructively. Almost total destructive interference occurs in all but certain very specific directions in which constructive interference is possible (Sears et al., 1982). Constructive interference in a given direction results in a diffraction beam that is intense relative to the sum of all other rays scattered in the same direction. 

The planes of motifs in a crystal thus act essentially as diffraction gratings (Bueche, 1986). Diffraction of electromagnetic radiation by crystals can occur only when the wavelength of the radiation is of the same order of magnitude as the regular repeat distance between motifs. This is the basis of the usefulness of using X-rays to determine crystal structure. 

A diffraction beam is produced by constructive interference when the path-length difference between reflections from the motifs in any two parallel planes of motifs in a crystal lattice is equal to a whole number of wavelengths. The angle between the diffraction beam and the lattice planes (the angle of reflection) is equal to the angle between the incident X-ray beam and the lattice planes (the angle of incidence). These phenomena are quantified by the Bragg law (Cullity, 1956)  

X-Ray Diffraction (XRD).—This technique has many features in common with neutron diffraction, such as low surface-bulk contrast but minimum disruption of the target. Few XRD studies of surface layers have appeared so far and for reasons outlined below in connection with neutron diffraction, attention has concentrated on inert-gas adsorption on graphite. Both XRD and neutron diffraction produce 

Application of XRD to chemisorption systems should be possible and surface sensitivity for adsorbates more complex than the inert gases could be improved by heavy-atom substitution. 

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For bulk structural detemiination (see chapter B 1.9). the main teclmique used has been x-ray diffraction (XRD). Several other teclmiques are also available for more specialized applications, including electron diffraction (ED) for thin film structures and gas-phase molecules neutron diffraction (ND) and nuclear magnetic resonance (NMR) for magnetic studies (see chapter B1.12 and chapter B1.13) x-ray absorption fine structure (XAFS) for local structures in small or unstable samples and other spectroscopies to examine local structures in molecules. Electron microscopy also plays an important role, primarily tlirough unaging (see chapter B1.17). 

Because x-rays are particularly penetrating, they are very usefiil in probing solids, but are not as well suited for the analysis of surfaces. X-ray diffraction (XRD) methods are nevertheless used routinely in the characterization of powders and of supported catalysts to extract infomration about the degree of crystallinity and the nature and crystallographic phases of oxides, nitrides and carbides [, ]. Particle size and dispersion data are often acquired with XRD as well. 

Both ultrasonic and radiographic techniques have shown appHcations which ate useful in determining residual stresses (27,28,33,34). Ultrasonic techniques use the acoustoelastic effect where the ultrasonic wave velocity changes with stress. The x-ray diffraction (xrd) method uses Bragg s law of diffraction of crystallographic planes to experimentally determine the strain in a material. The result is used to calculate the stress. As of this writing, whereas xrd equipment has been developed to where the technique may be conveniently appHed in the field, convenient ultrasonic stress measurement equipment has not. This latter technique has shown an abiHty to differentiate between stress reHeved and nonstress reHeved welds in laboratory experiments. 

Characterization. Ceramic bodies are characterized by density, mass, and physical dimensions. Other common techniques employed in characterizing include x-ray diffraction (XRD) and electron or petrographic microscopy to determine crystal species, stmcture, and size (100). Microscopy (qv) can be used to determine chemical constitution, crystal morphology, and pore size and morphology as well. Mercury porosknetry and gas adsorption are used to characterize pore size, pore size distribution, and surface area (100). A variety of techniques can be employed to characterize bulk chemical composition and the physical characteristics of a powder (100,101). 

This chapter contains articles on six techniques that provide structural information on surfaces, interfeces, and thin films. They use X rays (X-ray diffraction, XRD, and Extended X-ray Absorption Fine-Structure, EXAFS), electrons (Low-Energy Electron Diffraction, LEED, and Reflection High-Energy Electron Diffraction, RHEED), or X rays in and electrons out (Surfece Extended X-ray Absorption Fine Structure, SEXAFS, and X-ray Photoelectron Diffraction, XPD). In their usual form, XRD and EXAFS are bulk methods, since X rays probe many microns deep, whereas the other techniques are surfece sensitive. There are, however, ways to make XRD and EXAFS much more surfece sensitive. For EXAFS this converts the technique into SEXAFS, which can have submonolayer sensitivity. 

X-ray Diffraction (XRD) is a powerful technique used to uniquely identify the crystalline phases present in materials and to measure the structural properties (strain state, grain size, epitaxy, phase composition, preferred orientation, and defect structure) of these phases. XRD is also used to determine the thickness of thin films and multilayers, and atomic arrangements in amorphous materials (including polymers) and at inter ces. 

Air Samples Respirable dust samples are analyzed for quartz and cristobalite by x-ray diffraction (XRD). XRD is the preferred analytical method due to its sensitivity. 

The spacings between the layers (rfooz) measured by selected area electron diffraction were in a range of 0.34 to 0.35 nm[3]. X-ray diffraction (XRD) of the cathode deposit, including nanoparticles and nano-... 

In this section, the thin-film formation of OPVs is investigated with optical microscopy and X-ray diffraction (XRD). In the case of Oocl-OPV5, this has been supplemented with surface imaging by means of atomic force microscopy. It is demonstrated how an annealing treatment of the films alter deposition influences... 

Film-forming chemical reactions and the chemical composition of the film formed on lithium in nonaqueous aprotic liquid electrolytes are reviewed by Dominey [7], SEI formation on carbon and graphite anodes in liquid electrolytes has been reviewed by Dahn et al. [8], In addition to the evolution of new systems, new techniques have recently been adapted to the study of the electrode surface and the chemical and physical properties of the SEI. The most important of these are X-ray photoelectron spectroscopy (XPS), SEM, X-ray diffraction (XRD), Raman spectroscopy, scanning tunneling microscopy (STM), energy-dispersive X-ray spectroscopy (EDS), FTIR, NMR, EPR, calorimetry, DSC, TGA, use of quartz-crystal microbalance (QCMB) and atomic force microscopy (AFM). 

Finally, to evaluate the membranes, analysis such as X-ray diffraction (XRD), SEM, TEM and light scattering were performed at the School of Mineral and Material Engineering, Universiti Sains Malaysia. The last part of the work, testing the produced membrane to remove emulsifier oil from domestic wastewater, was accomplished on a limited budget. An experimental rig and membrane module were required. Also the need for experimental data for the application of the supported membrane may show the real success of this project. 

In this section we will discuss in some detail the application of X-ray diffraction and IR dichroism for the structure determination and identification of diverse LC phases. The general feature, revealed by X-ray diffraction (XRD), of all smectic phases is the set of sharp (OOn) Bragg peaks due to the periodicity of the layers [43]. The in-plane order is determined from the half-width of the inplane (hkO) peaks and varies from 2 to 3 intermolecular distances in smectics A and C to 6-30 intermolecular distances in the hexatic phase, which is characterized by six-fold symmetry in location of the in-plane diffuse maxima. The lamellar crystalline phases (smectics B, E, G, I) possess sharp in-plane diffraction peaks, indicating long-range periodicity within the layers. 

The nano-scale structures in polymer layered-silicate nano-composites can be thoroughly characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD is used to identify intercalated structures. XRD allows quantification of changes in layer spacing and the most commonly used to probe the nano-composite structure and... 

A similar procedure was adopted for synthesis of nanoparticles of cellulose (CelNPs). The polysaccharide nanoparticles were derivatised under ambient conditions to obtain nanosized hydrophobic derivatives. The challenge here is to maintain the nanosize even after derivatisation due to which less vigorous conditions are preferred. A schematic synthesis of acetyl and isocyanate modified derivatives of starch nanoparticles (SNPs) is shown in scheme 3. The organic modification was confirmed from X-ray diffraction (XRD) pattern which revealed that A- style crystallinity of starch nanoparticles (SNPs) was destroyed and new peaks emerged on derivatisation. FT-IR spectra of acetylated derivatives however showed the presence of peak at 3400 cm- due to -OH stretching indicating that the substitution is not complete. 

X-ray diffraction XRD was performed to determine the bulk crystalline phases of catalyst. It was conducted using a SIEMENS D-5000 X-ray diffractometer with CuX (k = 1.54439 A). The spectra were scanned at a rate of 2.4 degree/min in the range 20 = 20-80 degrees. 

The prepared catalysts were characterized by x-ray diffraction (XRD), N2 adsorption and CO chemisorption. Also, X-ray absorption spectroscopy (XAS) at the Ni K edge (8.333 keV) of reference and catalyst samples was carried out in the energy range 8.233 to 9.283 keV at beamline X18B of the... 

The Fe-B nanocomposite was synthesized by the so-called pillaring technique using layered bentonite clay as the starting material. The detailed procedures were described in our previous study [4]. X-ray diffraction (XRD) analysis revealed that the Fe-B nanocomposite mainly consists of Fc203 (hematite) and Si02 (quartz). The bulk Fe concentration of the Fe-B nanocomposite measured by a JOEL X-ray Reflective Fluorescence spectrometer (Model JSX 3201Z) is 31.8%. The Fe surface atomic concentration of Fe-B nanocomposite determined by an X-ray photoelectron spectrometer (Model PHI5600) is 12.25 (at%). The BET specific surface area is 280 m /g. The particle size determined by a transmission electron microscope (JOEL 2010) is from 20 to 200 nm. 

In this work, the catalytic reforming of CH4 by CO2 over Ni based catalysts was investigated to develop a high performance anode catalyst for application in an internal reforming SOFC system. The prepared catalysts were characterized by N2 physisorption, X-ray diffraction (XRD) and temperature programmed reduction (TPR). 

In this study, we report on the GaN nanorod growth by HOMVPE technique with or without using a new precursor, tris(N,N-dimethyldithiocarbamato)gallium(III) (Ga(mDTC)3). The structural and optical properties of GaN nanorods were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). 

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