Site Occupation of Excess Al Atoms in Off-Stoichiometric γ-Tial: Measurement of Debye-Waller Factors

1994 ◽  
Vol 364 ◽  
Author(s):  
S. Swaminathan ◽  
I. P. Jones ◽  
D. M. Maher ◽  
H. L. Fraser
Keyword(s):  
Site Occupancy ◽  
Diffraction Method ◽  
Electron Charge ◽  
X Ray Diffraction ◽  
Charge Density Distribution ◽  
Electron Charge Density ◽  
X Ray ◽  
Charge Densities ◽  
Structure Factors

AbstractIn recent years, the determination of x-ray structure factors and hence the electron charge density distribution in TiAl has received considerable attention. Experimental assessment of electron charge densities requires accurate values of the Debye-Waller (D-W) factors. This work attempts to determine the Debye-Waller factors from measurements of an Al rich off-stoichiometric single crystal of TiAl using the four circle x-ray diffraction method. The results suggest an ordered substitution of the excess Al atoms on the Ti-sublattice. This result is consistent with previous site occupancy studies.

scholarly journals Magnetically Oriented Powder Crystal to Indexing and Structure Determination

2014 ◽  
Vol 70 (a1) ◽  
pp. C1560-C1560
Author(s):  
Fumiko Kimura ◽  
Wataru Oshima ◽  
Hiroko Matsumoto ◽  
Hidehiro Uekusa ◽  
Kazuaki Aburaya ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Lattice ◽  
Powder Diffraction ◽  
Diffraction Method ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Lattice Parameters

In pharmaceutical sciences, the crystal structure is of primary importance because it influences drug efficacy. Due to difficulties of growing a large single crystal suitable for the single crystal X-ray diffraction analysis, powder diffraction method is widely used. In powder method, two-dimensional diffraction information is projected onto one dimension, which impairs the accuracy of the resulting crystal structure. To overcome this problem, we recently proposed a novel method of fabricating a magnetically oriented microcrystal array (MOMA), a composite in which microcrystals are aligned three-dimensionally in a polymer matrix. The X-ray diffraction of the MOMA is equivalent to that of the corresponding large single crystal, enabling the determination of the crystal lattice parameters and crystal structure of the embedded microcrytals.[1-3] Because we make use of the diamagnetic anisotropy of crystal, those crystals that exhibit small magnetic anisotropy do not take sufficient three-dimensional alignment. However, even for these crystals that only align uniaxially, the determination of the crystal lattice parameters can be easily made compared with the determination by powder diffraction pattern. Once these parameters are determined, crystal structure can be determined by X-ray powder diffraction method. In this paper, we demonstrate possibility of the MOMA method to assist the structure analysis through X-ray powder and single crystal diffraction methods. We applied the MOMA method to various microcrystalline powders including L-alanine, 1,3,5-triphenyl benzene, and cellobiose. The obtained MOMAs exhibited well-resolved diffraction spots, and we succeeded in determination of the crystal lattice parameters and crystal structure analysis.

An X-ray Diffraction Method for the Determination of Temperatures in Coke Reactions

1984 ◽  
Vol 28 ◽  
pp. 383-388 ◽  
Author(s):  
Jack L. Johnson ◽  
Seymour Katz
Keyword(s):  
Diffraction Method ◽  
Temperature History ◽  
Maximum Temperature ◽  
Slag Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Potential Source ◽  
History Of ◽  
Extract Information

Information about the conditions and reactions in a foundry cupola is essential to understand the thermochemistry of a cupola and thus improve its efficiency. A potential source of such information is coke taken from inside an operating cupola. In the region of the cupola that extends from the melt zone to the taphole, coke is directly involved in important chemical processes such as combustion, gasification, slag formation, iron sulfurization, carbon pickup, and oxide reduction. Coke is also suspected of being involved in the transport of silicon to the liquid iron. Each of these processes produces characteristic physical and/or chemical changes in the coke, making it possible to extract information about the processes from an examination of coke pieces taken from within an operating cupola. A program to study such coke samples is in progress. To effectively interpret these data it is necessary to know the temperature history of the coke being examined, especially the maximum temperature attained by the coke piece in the cupola.

scholarly journals Thickness Determination of Surface Film for Textured Specimens by X-ray Diffraction

1997 ◽  
Vol 30 (1-2) ◽  
pp. 71-79 ◽  
Author(s):  
Liu Yu-Shu ◽  
Zhao Yu
Keyword(s):  
Surface Film ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thickness Determination

A simple and convenient X-ray diffraction method is proposed to determine the thickness of surface film for textured specimens. The analysis result for a synthetic specimen with surface film has proved that the method is applicable and reliable.

Obtaining the structure factors for an epitaxial film using Cu X-ray radiation

2013 ◽  
Vol 46 (6) ◽  
pp. 1749-1754 ◽  
Author(s):  
P. Wadley ◽  
A. Crespi ◽  
J. Gázquez ◽  
M.A. Roldán ◽  
P. García ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Structure Factor ◽  
Tetragonal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Structure Factors ◽  
Scanning Transmission

Determining atomic positions in thin films by X-ray diffraction is, at present, a task reserved for synchrotron facilities. Here an experimental method is presented which enables the determination of the structure factor amplitudes of thin films using laboratory-based equipment (Cu Kα radiation). This method was tested using an epitaxial 130 nm film of CuMnAs grown on top of a GaAs substrate, which unlike the orthorhombic bulk phase forms a crystal structure with tetragonal symmetry. From the set of structure factor moduli obtained by applying this method, the solution and refinement of the crystal structure of the film has been possible. The results are supported by consistent high-resolution scanning transmission electron microscopy and stoichiometry analyses.

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