X-Ray Powder Diffraction XRD

This is a non-destructive method to analyze crystalline phases of the samples. Comparing with standard data file the phases present in a sample can be exactly identified. Now a days, analytical softwares and needed datafiles are available with the Diffractometer Unit. 

The technique can be understood following the sequence. (1) Basies of x-ray crystallography (2) Bragg s Law (3) Geometry of diffraction (4) Sample preparation techniques (4) General uses e.g. identification of unknown phases, their qualitative and quantitative estimation, grain-size analysis, crystallinity study, effect of temperature and pressure variation on crystalline phases etc. and (5) Basic errors for x-ray diffraction data. 

Knowledge of basic crystallography starts from the conception of symmetry, symmetry planes and symmetry operations necessary to identify the parameters, like lattice, lattice planes, crystal lattices (i.e. Bravis lattice) describing different crystal symmetries. Miller indices h, k, 1) to identify crystal planes etc. are explained here. 

Rotation around an imaginary Rotation axis or symmetry 1,2,3,4,6 

Reflection across a plane Plane of symmetry or mirror m 

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Analysis. Excellent reviews of phosphate analysis are available (28). SoHds characterization methods such as x-ray powder diffraction (xrd) and thermal gravimetric analysis (tga) are used for the identification of individual crystalline phosphates, either alone or in mixtures. These techniques, along with elemental analysis and phosphate species deterrnination, are used to identify unknown phosphates and their mixtures. Particle size analysis, surface area, microscopy, and other standard soHds characterizations are useful in relating soHds properties to performance. SoHd-state nmr is used with increasing frequency. 

Doping of alkali-metals into CNTs has been examined [11]. The X-ray powder diffraction (XRD) patterns of the K- or Rb-doped CNTs show that alkali-metals are intercalated between the CNT layers. The hexagonal unit cell is essentially the same as that of the stage-1 alkali-metal intercalated graphite ACg (A=K, Rb). For a sample doped with Rb, the observed lattice parameter of the perpendicular... 

The films were characterized using x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The photoelectron spectroscopy utilized a Vacuum Generators ESCA Lab II system with Mg(Ka) radiation. Binding energies (BE) were measured with respect to the surface C(ls) peak (284.5 eV) which was always present In these films. Scanning electron microscopy was done with a JEOL JSM-35C system. 

The structure and phase purity of the synthesized materials were determined by X-ray powder diffraction (XRD). The morphology was investigated by scanning electron microscopy (SEM). 

Chemical composition was determined by elemental analysis, by means of a Varian Liberty 200 ICP spectrometer. X-ray powder diffraction (XRD) patterns were collected on a Philips PW 1820 powder diffractometer, using the Ni-filtered C Ka radiation (A, = 1.5406 A). BET surface area and pore size distribution were determined from N2 adsorption isotherms at 77 K (Thermofinnigan Sorptomatic 1990 apparatus, sample out gassing at 573 K for 24 h). Surface acidity was analysed by microcalorimetry at 353 K, using NH3 as probe molecule. Calorimetric runs were performed in a Tian-Calvet heat flow calorimeter (Setaram). Main physico-chemical properties and the total acidity of the catalysts are reported in Table 1. 

The pH, EC and Fe3+ were used as control parameters. The first two were measured with an Orion probe combined pH/ATC electrode Triode and a conductivity cell DuraProbe ref. 0133030. Fe3+ was determined by molecular absorption (thiocyanate method). Mineralogical composition of the precipitates was determined by X-ray powder diffraction (XRD). Scanning electron microscopy, combined with an energy dispersive system (SEM-EDS), allowed the observation of morphological and compositional aspects of the precipitates. 

X-ray powder diffraction (XRD) patterns of the sample were recorded on a Rigaku D/Max 2400 X-ray diffractometer with Cu-Ka radiation (X=0.15418nm). The surface areas and pore diameters were measured by BET and BJH methods on a Micromeritics ASAP 2010 Sorptometer. Before analysis, the sample was degassed at 423K and 1.07xl0 3 KPa for 12h. The TEM image was obtained on a JEM-100C transmission microscope. The TG analysis was carried out on a DuPont 1090 Thermal Analyzer. 

Several methods have been used to characterize complexes in solid-state. Among the most commonly used methods are differential scanning calorimetry (DSC), x-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and x-ray crystallography. In recent years, the NMR method has showed many utilities (Ficarra et al., 2002 Rajendrakumaret al. 2005 Lantz et al., 2006). 

Thermogravimetric analysis (TGA) demonstrated that these polymers showed limited thermal stability for these materials, with decomposition occurring at temperatures >130°C. This stability is thought to be related to the M-CNR bond. The Tg data ranged from 37° to 96°C. The X-ray powder diffraction (XRD) pattern data provided complementary information concerning morphology of the polymers, as summarized in Table 1. 

Figure 4 exhibits a typical x-ray powder diffraction (XRD) pattern for the isolated, dry Au-Sn powder from an experiment where the Au Sn ratio was 1.3 1. The spectrum is compared with known diffraction patterns of Sn, AuSn, and Au5Sn and it can be seen that AuSn is the major component with the remaining smaller peaks assignable to Sn and Au5Sn. So some selectivity is exhibited, considering all of the possibilities for other compositions, and statistical/random clustering does not appear to dominate. 

Exposure to inorganic chemicals in the workplace has been traditionally evaluated using elemental analysis. However, in recent years some attention has been given to the toxic effects of specific compounds rather than elements, e.g., chromic acid ( ), nickel subsulfide Q), zinc oxide (4.), and sodium hydroxide (5.). It is therefore important that the occupational health chemist develop the capability to identify and quantitate chemical compounds. To this end, X-ray powder diffraction (XRD) is a unique tool for... 

X-ray powder diffraction (XRD) profile was measured by an X-ray diffractometer (Rigaku Denki, Ltd., D-9 C, equipped with a scintillation counter), using Cu-Ka radiation with the slit system of RS = 0.15 mm and DS = SS = 1/2° the 20 scan rate was 1/4 or 1/8 "/min. The 20 values were adjusted by the Si (111) reflection, using silicon powder (300 mesh) as the internal standard. Crystal morphology of zeolites was observed by means of scanning electron microscopy (Akashi, Ltd., Alpha-10). 

Methods. x-ray powder diffraction (XRD) patterns were recorded using a modified Siemens type F diffractometer, automated and equipped with a McBraun position sensitive detector (22). 

The identification of the solid phases and the determination of their crystallinities were carried out by X-ray powder diffraction (XRD), using a Philips PW 1349/30 X-ray diffractometer (Cu-KOt radiation). The crystallinity of each sample was evaluated by using as standard the most crystalline as-synthesized ZSM-48 from which the residual amorphous phase was further removed by ultrasonic treatment (15.). Alkali and A1 contents... 

Preservation of the zeolite structure was verified by X-ray powder diffraction (XRD) patterns recorded on a CGR Theta 60 instrument using Cu Kcq filtered radiation. The chemical composition of solids was determined at the Service Central d Analyse CNRS (Solaize, France). Copper in the zeolite was characterised by DR-UV-visible spectroscopy using a Perkin-Elmer Lambda 14 apparatus, equipped with a reflectance sphere, and by temperature programmed reduction (TPR), using a Micromeritics Autochem 2910, equipped with a katharometer (3% H2/Ar gas mixture at 30 mL.min1 and 10 K.min 1). 

The next stage of characterization focuses upon the different phases present within the catalyst particle and their nature. Bulk, component structural information is determined principally by x-ray powder diffraction (XRD). In FCC catalysts, for example, XRD is used to determine the unit cell size of the zeolite component within the catalyst particle. The zeolite unit cell size is a function of the number of aluminum atoms in the framework and has been related to the coke selectivity and octane performance of the catalyst in commercial operations. Scanning electron microscopy (SEM) can provide information about the distribution of crystalline and chemical phases greater than lOOnm within the catalyst particle. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) can be used to obtain information on crystal transformations, decomposition, or chemical reactions within the particles. Cotterman, et al describe how the generation of this information can be used to understand an FCC catalyst system. 

DTA = differential thermal analysis FCC = face centered cubic FWHM = full width at half maximum ICDD = international center for diffraction data JCPDS = joint committee on powder diffraction standards EP = Lorentz and polarization PO = Preferred orientation. PT = parallel tempering PXRD = powder X-ray diffraction SA = simulated annealing SWE = short-wavelength-limit TGA = thermogravametric analysis XRPD = X-ray powder diffraction XRD = X-ray diffraction ... 

Analysis by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) of 4.0%H2[PtCl6]/TH revealed the presence of about 200 nm large aggregates composed of 2-4 nm sized anatase crystallites (22). Specific surface areas of rmmodified P25 (50 m /g) and Aid (3 m /g) were not changed upon modification whereas a significant decrease from 334 to 260 m /g was found for TH. 

A wide range of techniques has been used on both fresh and used catalysts to characterize the nature of the oxide surface, for example X-ray powder diffraction (XRD) [10-12], UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS) [11, 12], Raman spectroscopy [10, 11, 14—17], X-ray photoelectron spectroscopy (XPS) [11, 12, 18], electron paramagnetic resonance (EPR) [12, 19], infrared spectroscopy [10, 20] and temperature programmed reduction (TPR) [16, 21]. Given the number of... 

X-ray powder diffraction (XRD) patterns were obtained by using a Siemens D-5000 diffractometer employing nickel filtered Cu Ka radiation and operating at 40 kV and 30 mA. 

Nitrogen adsorption-desorption isotherms were measured at 77 3 K using a commercial volumetric adsorption system Autosorb-1 or NOVA-1200 (both from Quantachrome Corp ). The samples were outgassed at 10" Torr and 573 K for 3 h prior to the analysis X-ray powder diffraction (XRD) patterns were obtained on PW 1840 diffractometer (Phillips), with Co Ka radiation, 40 KV, 25 mA. 

X-ray powder diffraction (XRD) patterns were taken on a Spectrolab CPS Series 3000 120 diffractometer, using Ni filtered Cu Ka radiation. The nitrogen adsorption isotherms were determined at 77 K by means of a Micromeritics Gemini 2370 surface area analyser. Surface areas were derived from the BET equation in the relative pressure range 0.05-0.25, assuming a cross-sectional area of 0.162 nm" for the nitrogen molecule [ 18]. 

A mineral is defined by its structure, i.e. by the regular arrangement of its atoms in space. Only tliose methods, therefore, which reflect the structure are capable of providing unambiguous identification of a particular oxide. In general, diffraction methods fulfill this purpose and X-ray powder diffraction (XRD), the most common of these, is essential for identification and control of the purity of the product. The minimum size required for a crystal to diffract X-rays is of the order of a few unit cells (ca. 2-3 nm). Electron diffraction is another method often used for... 

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