Crystallite size determination

Fig. 7.3. Crystallite size determined from x-ray diffraction line broadening studies show substantial shock-induced reductions. The chemical reactivity of such powders would be expected to be greatly enhanced [86M02].

The catalysts were characterized by inductively coupled plasma emission spectroscopy (ICP-ES Perkin Elmer Optima 3300RL) to determine cobalt content, x-ray diffraction (XRD Bruker A-500) with crystallite size determination using the Rietveld method, and temperature-programmed reduction (Zeton Altamira AMI-200) using 30 ml/min 10% H2/Ar and a ramp rate of 10°C/min. Surface area... 

Scherrer-Williamsoim-Hall Methodology for Crystallite Size Determination... 

Crystallite size determined from the diffraction pattern measurements are given in Table XI and show the higher degree of three-dimensional ordering of Acheson graphite compared with Desulco,... 

For fuel-cell technology development, it has been important to understand the characteristics and operation of highly dispersed platinum and platinum alloy electrocatalysts. A series of papers on platinum crystallite size determinations in acid environments for oxygen reduction and hydrogen oxidation was published together by Bert, Stonehart, Kinoshita and co-workers.5 The conclusion from these studies was that the specific activity for oxygen reduction on the platinum surface was independent of the size of the platinum crystallite and that there were no crystallite size effects. 

Alkylation of Butylamine with Methanol. The authors of this review investigated the alkylation of butylamine with methanol over a reduced commercial CuO-ZnO-AbOs catalyst (CZA-l). Various techniques (XRD, XPS) and titration of surface metallic copper with N2O were used to estimate the amount of different type of copper species in the catalyst. The dispersion of metallic copper species was calculated from the average crystallite size determined by XRD using the following ion D(%) = 120/d(nm). The surface area of metallic copper in the catalysts reduced at different temperatures was determined by titration with N20. ... 

Problems stUl remain, though, in this area of endeavour. Any destruction of the perfection in the crystal structure degrades the sharpness of the diffracted beams. This in itself can be used for crystallite size determination. Poorly crystalline material gives poor information, and truly amorphous samples give virtually no crystallographic information this way. 

The importance of anatase crystallinity was emphasized in relation to the preparation and annealing procedures for achieving high photocatalytic performance [19,24,25,119,120]. The highest photoactivity always appeared at the onset of phase transformation of anatase to rutile. A linear relationship between photoactivity (normalized by the BET surface area) and crystallite size determined from FWHM of 101 diffraction line was reported for powders prepared from TTIP by either spray or gas pyrolysis, although the variations in BET surface area and crystallite size were limited to a narrow range, from 2.5 to 50 mVg and 10 to 33 nm [121],... 

Nagle DC, Thrower PA. The importance of strain in crystallite size determinations. Carbon 1973 ll(6) 663-664. 

Powder X-ray diffraction is an excellent analytical tool for identification and physical characterization of crystalline samples. It can be used for chemical identification (by matching unknowns with X-ray patterns of known reference samples), for crystal structure information, and for crystallite size determination. Such information is extremely valuable for pigment characterization. Many pigments exhibit polymorphism and each morph can have dramatically different physical properties (shade, opacity, heat stability, surface area, particle size and shape, melting point). These properties define to a large extent the performance characteristics of the pigment and therefore its applications. 

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