Brentano

Bragg-Brentano Powder Diffractometer. A powder diffraction experiment differs in several ways from a single-crystal diffraction experiment. The sample, instead of being a single crystal, usually consists of many small single crystals that have many different orientations. It may consist of one or more crystalline phases (components). The size of the crystaUites is usually about 1—50 p.m in diameter. The sample is usually prepared to have a fiat surface. If possible, the experimenter tries to produce a sample that has a random distribution of crystaUite orientations. 

Fig. 14. Focusing schemes in powder diffraction (a) conventional para-focusing Bragg-Brentano diffractometer (b) parallel-beam diffractometer using a...

The Bra -Brentano geometry is used widely for preferentially and randomly oriented polycrystalline films. In this geometry (Figure 3a), slits collimate the inci-... 

Figure 3 Bragg-Brentano dHfractometar (a) and Saemann-Bohlin diffractometer (b).

For ultrathin epitaxial films (less than "100 A), Grazingincidence X-ray Diffraction (GrXD) is the preferred method and has been used to characterize monolayer films. Here the incidence angle is small ("0.5°) and the X rays penetrate only "100-200 A into the specimen (see below). The exit angle of the diffracted X rays is also small and structural information is obtained about (hkl) planes perpendicular to the specimen sur e. Thus, GIXD complements those methods where structural information is obtained about planes parallel to the surface (e.g., Bra -Brentano and DCD). 

Figure 4 Diffraction patterns (Bragg-Brentano geometry) of three superconducting thin Aims ( 2- im thick) anneaied for different times. The temperatures for 0 resistance and for the onset of superconductivity are noted.

Figure 5 Bragg>Brentano diffraction pattern for magnetic media used in a demonstration of 1-Gb/in magnetic recording. The iines show a deconvoiution of the data into individual diffraction peaks, which are identified.

The use of Equation (22) is very general, but it is also possible, with accurate measurements and data treatment, to perform the quantitative phase analysis in semi-crystalline materials without using any internal standard. This procedure is possible only if the chemical compositions of all the phases, including the amorphous one, are known. If the composition of the amorphous phase is unknown, the quantitative analysis without using any internal standard can still be used provided that the chemical composition of the whole sample is available [51]. This approach, until now, has been developed only for the XRD with Bragg-Brentano geometry that is one of the most diffused techniques in powder diffraction laboratories. 

An expression including the diffuse background of a crystalline phase was calculated for a Bragg-Brentano geometry [55] ... 

Brentano F, Kyburz D, Schorr O, Gay R, Gay S. The role of Toll-like receptor signalling in the pathogenesis of arthritis. Cell Immunol 2005 233(2) 90-96. 

Hillyer, Robert. Alchemy a symphonic poem, by Robert Hillyer. With decorations by Beatrice Stevens. New York Brentano s, 1920. 4 p.l., 11-61, [1] p., 11. Possibly. 

Funck-Brentano, C. and Jaillon, P. (1993) Rate-corrected QT interval techniques and limitations. The American Journal of Cardiology, 72, 17B—22B. 

Charbit B, Becquemont L, Lepere B, Peytavin G, Funck-Brentano C. Pharmacokinetic and pharmacodynamic interaction between grapefruit juice and halofantrine. Clin Pharmacol Ther 2002 72(5) 514-523. 

Figure 1. X-ray patterns of calcined MSU-1 and -4 Silica obtained with Tergitol 15S12 and Tween 20 as templating agents. The patterns were recorded with a Bruker D5000 diffractometer in Bragg-Brentano reflection geometry. Cu-L radiation was employed that was monochromatized by a graphite single crystal in the diffracted beam.

FTIR spectra were recorded with an Impact 410 (Nicolet) spectrometer. Powder X-ray diffraction data were obtained on a Siemens D 5005 diffractometer in the Bragg-Brentano geometry arrangement using CuKa radiation. Adsorption isotherms of nitrogen at -196 °C... 

Phase identification was performed by X-ray diffraction in Bragg-Brentano geometry with Cu-Ka radiation and a secondary monochromator. A rotating sample holder was used in order to minimize texture effects in the x-y plane and to offset the effects of the rather large grain size. Diffractograms were taken as a function of depth after stepwise removal of layers with an abrasive diamond disk. 

L. Cloarec-Blanchard, C. Funck-Brentano, A. Carayon, and P. Jaillon. Rapid development of nitrate tolerance in healthy volunteers assessment using spectral analysis of short-term blood pressure and heart rate variability. J. Cardiovasc. Pharmacol. 24 266-273, 1994. 

Two common geometries are used for collecting powder diffraction data, either the reflection or Bragg-Brentano method (Figure 8.29a) which uses a flat plate sample holder made either of glass or, ideally, of an... 

Figure 8.29 Typical geometries in laboratory PXRD instruments (a) Bragg-Brentano, (b) capillary (not to scale).

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