Employing X-ray scattering to characterize materials with grain sizes in the nano-regime

2008 ◽  
Vol 23 (2) ◽  
pp. 96-100 ◽  
Author(s):  
E. A. Laitila ◽  
D. E. Mikkola
Keyword(s):  
Crystallite Size ◽  
Large Fraction ◽  
Matrix Material ◽  
Background Intensity ◽  
X Ray ◽  
Volume Fractions ◽  
X Ray Scattering ◽  
The Matrix ◽  
Diffraction Peaks ◽  
Ray Scattering

This study focuses on characterization of an (Al,Cr)3Ti alloy processed together with titanium powder by reactive mechanical milling (RMM) to produce an ultrafine grained intermetallic alloy matrix with in situ carbide and hydride phases formed during processing. Observations of X-ray scattering as RMM processing time increases show severe broadening of matrix diffraction peaks, accompanied by the appearance of diffraction peaks resulting from the formation of very small crystallites of TiC and TiH1.92 phases with increasing volume fractions, and finally, increasing background intensity as the crystallite size of the matrix phase decreases to ∼2 nm. Estimates of phase volume fractions were made by the direct comparison method, along with crystallite sizes by Warren–Averbach peak profile analysis. The general increase in background intensities has been attributed to random static displacements of the large fraction of atoms located within the grain boundary regions. Further, it has been concluded that the matrix material with a crystallite size of a few nanometers has about half the atoms in statically displaced positions defining the boundary regions. The results argue that background intensity changes should not be ignored and are useful in interpreting scattering from these nano-scale materials.

Pore growth kinetics in heat-treated glass-like carbons

1986 ◽  
Vol 1 (6) ◽  
pp. 832-835 ◽  
Author(s):  
Jalil Lachter ◽  
Leo G. Henry ◽  
Robert H. Bragg ◽  
Stephen Spooner
Keyword(s):  
Growth Kinetics ◽  
Matrix Material ◽  
Radius Of Gyration ◽  
Void Size ◽  
Kcal Mole ◽  
X Ray ◽  
X Ray Scattering ◽  
Heat Treated ◽  
The Matrix ◽  
Kinetics Of

The kinetics of changes in void size during annealing of glass-like carbons in the temperature range 1000°−2800 °C for times up to 150 h were studied using small-angle x-ray scattering determinations of the radius of gyration Rg. The results show that Rg ranged from 9 Å at 1000°C to about 24 Å at 2800 °C. A pore coarsening analysis and a superimposition kinetic analysis applied to Rg gave activation energies of 76 ± 4 kcal/mole and 74 ± 9 kcal/mole, respectively, which are associated with migration of vacancies within graphitic layers in the matrix material.

A low-background-intensity focusing small-angle X-ray scattering undulator beamline

2013 ◽  
Vol 46 (6) ◽  
pp. 1670-1680 ◽  
Author(s):  
Nigel M. Kirby ◽  
Stephen T. Mudie ◽  
Adrian M. Hawley ◽  
David J. Cookson ◽  
Haydyn D. T. Mertens ◽  
...  
Keyword(s):  
Single Crystal ◽  
Background Intensity ◽  
Wide Angle ◽  
Accurate Analysis ◽  
Diverse Range ◽  
X Ray ◽  
X Ray Scattering ◽  
Collimation System ◽  
Scattering Geometry ◽  
Ray Scattering

The SAXS/WAXS beamline at the Australian Synchrotron is an advanced and flexible undulator X-ray scattering beamline used for small- and wide-angle X-ray scattering analysis on a wide variety of solids, fluids and surfaces across a diverse range of research and development fields. The beamline has numerous features that minimize the intensity of the instrument background, provide automated stable optics, and allow accurate analysis of very weakly scattering samples. The geometric and intensity requirements of a three-slit collimation system are described in detail for conventional metal and single-crystal germanium slits. Straightforward ray tracing and simple linear projections describe the observed direct beam as well as parasitic background scattering geometry of the beamline at its longest camera length, providing a methodology for the design and operation of similar beamlines. As an aid to instrument design, the limit of background intensity determined by the intensity incident on single-crystal germanium guard slit edges and itsqdependence was quantified at 11 keV. Details of the beamline's implementation, underlying optical concept and measured performance are given.

scholarly journals HUG and SQUEEZE: using CRYSTALS to incorporate resonant scattering in the SQUEEZE structure-factor contributions to determine absolute structure

2017 ◽  
Vol 73 (11) ◽  
pp. 845-853 ◽  
Author(s):  
Richard I. Cooper ◽  
Howard D. Flack ◽  
David J. Watkin
Keyword(s):  
Large Fraction ◽  
Resonant Scattering ◽  
Crystalline Materials ◽  
X Ray ◽  
X Ray Scattering ◽  
Residual Electron Density ◽  
The Absolute ◽  
Absolute Structure ◽  
Disordered Regions ◽  
Ray Scattering

The resonant-scattering contributions to single-crystal X-ray diffraction data enable the absolute structure of crystalline materials to be determined. Crystal structures can be determined even if they contain considerably disordered regions because a correction is available via a discrete Fourier transform of the residual electron density to approximate the X-ray scattering from the disordered region. However, the corrected model cannot normally account for resonant scattering from atoms in the disordered region. Straightforward determination of absolute structure from crystals where the strongly resonantly scattering atoms are not resolved has therefore not been possible. Using an approximate resonant-scattering correction to the X-ray scattering from the disordered regions, we have developed and tested a procedure (HUG) to recover the absolute structure using conventional Flack x refinement or other post-refinement determination methods. Results show that in favourable cases the HUG method works well and the absolute structure can be correctly determined. It offers no useful improvement in cases where the original correction for the disordered region scattering density is problematic, for example, when a large fraction of the scattering density in the crystal is disordered, or when voids are not occupied equally by the disordered species. Crucially, however, if the approach does not work for a given structure, the statistics for the absolute structure measures are not improved, meaning it is unlikely to lead to misassignment of absolute structure.

scholarly journals Electron density map using multiple scattering in grazing-incidence small-angle X-ray scattering

2007 ◽  
Vol 40 (3) ◽  
pp. 496-504 ◽  
Author(s):  
Byeongdu Lee ◽  
Insun Park ◽  
Haewoong Park ◽  
Chieh-Tsung Lo ◽  
Taihyun Chang, ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Electron Density ◽  
Small Angle ◽  
Grazing Incidence ◽  
X Ray ◽  
X Ray Scattering ◽  
Diffraction Peaks ◽  
Density Map ◽  
Electron Density Map ◽  
Ray Scattering

The electron density map of a block copolymer thin film having the hexagonally perforated layer (HPL) structure was directly obtained from the measured grazing-incidence small-angle X-ray scattering (GISAXS) pattern, exploiting the multiple-scattering phenomena present in GISAXS. It is shown that GISAXS is in principle equivalent to three-beam diffraction, which has been used to extract phases of diffraction peaks. In addition, X-ray reflectivity analysis has been performed which, when combined with the GISAXS results, provides full details of the HPL structure.

Combinedin situsmall- and wide-angle X-ray scattering studies of TiO2nanoparticle annealing to 1023 K

2010 ◽  
Vol 43 (6) ◽  
pp. 1400-1408 ◽  
Author(s):  
Jan Kehres ◽  
Jens Wenzel Andreasen ◽  
Frederik Christian Krebs ◽  
Alfons M. Molenbroek ◽  
Ib Chorkendorff ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Titanium Dioxide ◽  
Crystallite Size ◽  
Temperature Interval ◽  
Wide Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ray Scattering

Combinedin situsmall- and wide-angle X-ray scattering (SAXS/WAXS) studies were performed in a recently developed laboratory setup to investigate the dynamical properties of dry oleic acid-capped titanium dioxide nanorods during annealing in an inert gas stream in a temperature interval of 298–1023 K. Aggregates formed by the titanium dioxide particles exhibit a continuous growth as a function of temperature. The particle size determined with SAXS and the crystallite size refined from WAXS show a correlated growth at temperatures above 673 K, where the decomposition of the surfactant is expected. At temperatures above 823 K, the particle and crystallite sizes increase rapidly. An increasing discrepancy between particle and crystallite size indicates growth of a shell structure on the single-crystalline core of the particles. This was confirmed by high-resolution transmission electron microscopy studies of the sample. Transmission electron microscopy shows a transformation from a rod to a spherical particle shape; the WAXS data indicate that the shape change occurs in a temperature interval of 773–923 K. The highly crystalline titanium dioxide particles remain in the metastable anatase phase during the entire annealing process. The transition to the thermodynamically stable rutile phase was not observed at any temperature, in agreement with existing experimental observations.

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