X-Ray Diffraction XRD

XRD is a fast and nondestructive test which is frequently used to characterise thermoset materials and their composites. Crystalline materials are characterised by sharp peaks, whereas amorphous materials show broad humps. Thus, the degree of crystallinity can be estimated. When a crystalline material such as clay is dispersed in a thermoset matrix, one can study the intercalation and exfoliation behaviour (see subsequent chapters). If the crystallites of the power are very small, the peaks of the pattern will be broadened. From this broadening one can determine an average crystallite size using the Debye-Scherrer equation  

Where B is the broadening of the diffraction line measured at half of its maximum intensity (radians), 0 is the Bragg angle, and X is the wavelength of the X-ray. 

Modern X-ray diffractrometer. (Courtesy of Panalytics, XPert Powder [accessed March 28, 2012]. With permission.) 

For example, the relationship between pseudocapacitance and heat treatment temperature of nickel oxide was investigated using XRD, x-ray absorption spectroscopy, and CV. These techniques can provide important information about structure arrangements and the electrochemical properties of nickel oxide at various heat treatment temperatures. Similar studies were performed on composites (graphene-polyaniline, Mn02-mesoporous carbon) [30,31]. XRD can reveal material structures revealing the relationship of electrochemical properties and the effects of certain chemical or physical alterations. 

In X-Ray Diffraction (XRD), a collimated beam of mono-chromatic X rays between 0.5 A and 2 A wavelength strike a sample and are diffracted by crystal planes present. Bragg s law, 

The major uses of XRD are identification of crystalline phases, determination of strain, crystalline orientation and size, epitaxial relationship, and the accurate determination of atomic positions (better then in electron diffraction). Because of the strong Z dependence of X-ray scattering, light elements are difficult to deal with, particularly in the presence of heavy elements. 

The X-ray diffraction (XRD) is a technique used generally in crystalline materials to identify the atomic and molecular structure. But also, it has a wide range of applications, like the determination of the arrangement of atoms in minerals and metals, the structure of organic compoxmds, the crystal structure of proteins, etc. 

In the particular case of montmorillonite, XRD is used mainly to determine the basal distance, which is calculated applying Braggs equation  

MtNanofil 116 and the OMt with different content of surfactant (ethyl hexadecyl dimethyl ammonium, C16). It can be observed that as the content of C16 increases (from 20 to 100% of the CEC) in the OMt the position of the dgg peak displaces towards lower angles (0). Therefore, the basal distance increases. 

Several studies have been conducted regarding the type of surfactant exchanged in montmorillonite [24, 26, 27]. For example, Jankovic et al. 

In all these cases, XRD results were used to characterise the OMts. 

According to Fig. 10.1, XRD is one of the most frequently applied techniques in catalyst characterization. X-rays have wavelengths in the A range, are sufficiently energetic to penetrate solids and are well suited to probe their internal structure. XRD is used to identify bulk phases and to estimate particle sizes [9]. 

An X-ray source consists of a target which is bombarded with high energy electrons. The emitted X-rays arise from two processes. Electrons slowed down by the target emit a continuous background spectrum of Bremsstrahlung. Superimposed on this are characteristic, narrow lines. The Cu Ka line, for example, arises because a primary electron creates a core hole in the K shell, which is filled by an electron from the L shell (K(3 the K-hole is filled from the M-shell, etc.) under emission of an X-ray quantum. The process is called X-ray fluorescence. It 

The XRD pattern of a powdered sample is measured with a stationary X-ray source (usually Cu Ka) and a movable detector, which scans the intensity of the diffracted radiation as a function of the angle 20 between the incoming and the diffracted beams. When working with powdered samples, an image of diffraction lines occurs because a small fraction of the powder particles will be oriented such that by chance a certain crystal plane (hkl) is at the right angle with the incident beam for constructive interference. 

Diffraction patterns can be used to identify the various phases in a catalyst. An example is given in Fig. 10.3b, where XRD is used to follow the reduction of alumina-supported iron oxide at 675 K as a function of time. The initially present oc-Fe2C 3 (haematite) is partially reduced to metallic iron, with Fe3C 4 (magnetite) as the intermediate. The diffraction lines from platinum are due to the sample holder [10]. 

The width of diffraction peaks carries information on the dimensions of the reflecting planes. Diffraction lines from perfect crystals are very narrow. For crystallite sizes below 100 nm, however, line broadening occurs due to incomplete destructive interference in scattering directions where the X-rays are out of phase. The Scherrer formula relates crystal size to line width  

Coke structure can be characterized by X-Ray diffraction analysis. This technique makes it possible to determine if there is coke with crystalline structure on the catalyst. However, the sensitivity of this type of determination is rather low, being it difficult to determine the fraction and/or amount of coke in the crystalline form. Support dissolution procedure was also used to analyse the coke free from support by XRD. Support dissolution procedure for coke XRD analysis, is more appropriate when the coke content on the catalyst is high, and as long as the strong acidic media used in the dissolution does not alter the coke structure. 

Similar results concerning the coke structure were reported recently by J. Ruixia et aF on Pd-La/spinel catalyst, coked during the production of 2,6 diisopropylaniline at 220°C. 

In the case of the ZSM-5 zeolite catalysts, it has been described that it undergoes a displacive transformation from monoclinic to orthorhombic when it occludes bulky ions, altering the relative peak positions and intensities in the XRD pattterns . The deposition of coke inside the channels was thus verified by means of changes in the XRD spectra of coked vs fresh catalysts The XRD pattern of the coked catalyst is similar to that of the catalyst with the occluded template ions. 

Number of times characterization techniques were used at the ICC Baltimore 1996 

Baltimore, 1996 [Reproduced from J.W. Niemantsverdriet, Spectroscopy in Catalysis, An Introduction (2000), Wiley-VCH, Weinheim]. 

X-ray diffraction is one of the oldest and most frequently applied techniques in catalyst characterization. It is used to identify crystalline phases inside catalysts by means of lattice structural parameters, and to obtain an indication of particle size. 

Bragg equation (1) to verify that the Pd and (200) reflections are expected at ang  

If one measures the angles, 26, under which constructively interfering X-rays leave the crystal, the Bragg relation (1) gives the corresponding lattice spacings, which are characteristic for a particular compound. 

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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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