Powder x-ray diffraction techniques

H20 (40) and CsPr(C03)2 (41). The powder X-ray diffraction technique was used to study most solid carbonates of lanthanides. Lanthanide/actinide complexes, M(C03)2 2re (n = 1 -3) have been... 

Bugay DE, Newman AW, Findlay WP. 1996. Quantitation of cefepime 2HC1 dihydrate in cefepime 2HC1 monohydrate by diffuse reflectance IR and powder X-ray diffraction techniques. J. Pharm. Biomed. Anal. 15 49-61. 

A series of perovskite compositions were synthesized using oxides and carbonates of the cations by conventional ceramic process. The synthesized powders were characterized using powder x-ray diffraction technique to ensure phase purity. Conductivity measurements were made in H2-H2O atmosphere to determine proton conductity. As the perovskite compositions are inherently mixed conducting, the transference numbers for proton and electron conduction were also determined by varying the partial pressures of hydrogen and steam across the membrane. 

Characterization of jS-hematin by powder X-ray diffraction techniques with both conventional and synchrotron illation indicates that the phase which results from equations 3 and 4 are sufficiently crystalline to give strong diffraction peaks out to 45 in 20 with Cu (X = 1.540598 A) radiation. The pattern obtained with synchrotron radiation (X = 1.7492 A) on beam line X7A at the National Synchrotron Light Source at the Brookhaven National Laboratory is shown in Figure 9. 

Bleaching Powder. This material, known siace 1798, is made by chlorination of slightly moist hydrated lime, calcium hydroxide [1305-62-0] Ca(OH)2- It has the empirical formula Ca(OCl)2 CaCl2 Ca(OH)2 2H20. Its compositioa, loag a subject of coatroversy, was estabHshed by phase studies, microscopy, and x-ray diffraction techniques (241). The initial chlorination products are monobasic calcium chloride [14031-38-4] and dibasic calcium hypochlorite [12394-14-8] ... 

In the powder diffraction technique, a monochromatic (single-frequency) beam of x-rays is directed at a powdered sample spread on a support, and the diffraction intensity is measured as the detector is moved to different angles (Fig. 1). The pattern obtained is characteristic of the material in the sample, and it can be identified by comparison with a database of patterns. In effect, powder x-ray diffraction takes a fingerprint of the sample. It can also be used to identify the size and shape of the unit cell by measuring the spacing of the lines in the diffraction pattern. The central equation for analyzing the results of a powder diffraction experiment is the Bragg equation... 

Techniques for differentiating between amorphous and crystalline are (i) sharp melting point, (ii) sharp peaks in the solid state infrared fingerprint region, (iii) optical birefringence observed when solid is viewed in a phase contrast microscope and (iv) sharp peaks in the powder X-ray diffraction pattern. 

Structural characterization of the prepared Co/alumina catalysts was studied by using the following techniques Brunauer-Emmett-Teller (BET), temperature-programmed reduction (TPR), H2 chemisorption by temperature-programmed desorption (TPD) with 02 pulse reoxidation, and powder x-ray diffraction (XRD). 

The /3-polymorphic form of anhydrous carbamazepine is official in the USP [3], The USP stipulates that, The X-ray diffraction pattern conforms to that of USP Carbamazepine Reference Standard, similarly determined. No limits have been set in the USP for the other polymorphs of anhydrous carbamazepine. Although several polymorphic forms of anhydrous carbamazepine have been reported, only the a- and /3-forms have been extensively studied and characterized [49]. A comparison of the powder x-ray diffraction patterns of these two forms revealed that the 10.1 A line (peak at 8.80° 26) was unique to a-carbamazepine, and so this line was used for the analysis (Fig. 5). It was possible to detect a-carbamazepine in a mixture where the weight fraction of a-carbamazepine was 0.02 at a signal-to-noise ratio of 2. Much greater sensitivity of this technique has been achieved in other systems. While studying the polymorphism of l,2-dihydro-6-neopentyl-2-oxonicotinic acid, Chao and Vail [50] used x-ray diffractometry to quantify form I in mixtures of forms I and II. They estimated that form I levels as low as 0.5% w/w can be determined by this technique. Similarly the a-inosine content in a mixture consisting of a- and /3-inosine was achieved with a detection limit of 0.4% w/w for a-inosine [51]. 

Probably the most widely employed technique now used in phase studies is powder X-ray diffraction. The X-ray powder pattern of a compound can be used as a fingerprint, and data for many compounds are available. This can be illustrated with reference to the sodium fluoride (NaF)-zinc fluoride (ZnF2) system. Suppose that pure NaF is mixed with a few percent of pure ZnF2 and the mixture heated at about 600°C until reaction is complete. An X-ray powder photograph will show the presence of two compounds (or phases), NaF, which will be the major component, and a small amount of a new compound (point A, Fig. 4.1a). A repetition of the experiment, with gradually increasing amounts of ZnF2 will yield a similar result, but the amount of the new phase will increase relative to the amount of NaF until... 

Ffirai and Toshima have published several reports on the synthesis of transition-metal nanoparticles by alcoholic reduction of metal salts in the presence of a polymer such as polyvinylalcohol (PVA) or polyvinylpyrrolidone (PVP). This simple and reproducible process can be applied for the preparation of monometallic [32, 33] or bimetallic [34—39] nanoparticles. In this series of articles, the nanoparticles are characterized by different techniques such as transmission electronic microscopy (TEM), UV-visible spectroscopy, electron diffraction (EDX), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) or extended X-ray absorption fine structure (EXAFS, bimetallic systems). The great majority of the particles have a uniform size between 1 and 3 nm. These nanomaterials are efficient catalysts for olefin or diene hydrogenation under mild conditions (30°C, Ph2 = 1 bar)- In the case of bimetallic catalysts, the catalytic activity was seen to depend on their metal composition, and this may also have an influence on the selectivity of the partial hydrogenation of dienes. 

The solid phase in equilibrium with the saturated solution must be analyzed by techniques such as hot stage microscopy, differential scanning calorimetry, or powder x-ray diffraction, to verify if the starting material has undergone a phase transformation. 

Kokotailo, G.T. and Fyfe, C.A. (1995) Zeolite structure analysis with powder X-ray diffraction and solid-state NMR techniques. Rigaku J., 12, 3-10. 

The compound is treated with concentrated HCl H2S is hberated and is identified from its odor which also turns lead acetate paper black. The hberated H2S is transported onto a GC port by helium carrier gas and determined by an FID, TCD or FPD. Antimony in the solution may be analyzed by flame or furnace AA or by ICP spectrophotometry. The solid powder may be characterized by X—ray diffraction technique. 

The five years since last considering specifically recent developments in X-ray and neutron diffraction methods for zeolites [1] have witnessed substantial progress. Some techniques, such as high resolution powder X-ray diffraction using synchrotron X-rays, have blossomed from earliest demonstrations of feasibility to widespread and productive application. Others, such as neutron powder diffraction, have shown steady progress. For still others, notably microcrystal diffraction, a variety of circumstances have contributed to extended gestation periods. Additionally, opportunities scarcely considered earlier (such as single crystal Laue diffraction, and certain developments in computer simulations that complement diffraction work) now command broad attention and warrant the commitment of substantial further investment. 

Three common techniques used are transmission electron microscopy together with electron diffraction, powder X-ray diffraction, and optical absorption (or transmission) spectroscopy. 

In order to obtain detailed structure, a knowledge of diffraction intensities is essential, the intensities being related to the structure factor. Computer-controlled single-crystal X-ray diffractometers with structure (software) packages have made structure elucidation a routine matter. The availability of synchrotron X-radiation of continuously variable wavelength has made X-ray diffraction a still more powerful structural tool for the study of solids. A technique of great utility to solid state chemists is the Rietveld treatment of powder X-ray diffraction profiles (Rietveld, 1969 Manohar, 1983). Automated structure packages for the determination of unknown structures by this method are now commercially available (see section 2.2.3). In Fig. 2.1, we show a typical set of profile data. 

Information on the morphology of polymers is revealed by techniques such as powder X-ray diffraction (PXRD), which is often called wide-angle X-ray scattering (WAXS) by polymer scientists, and small-angle X-ray scattering (SAXS). The crystallites exist in a polymer sample below the melting temperature T, an order-disorder transition, above which a viscous melt is formed. 

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