Energy-Tunable X-Ray Diffraction in Polycrystalline Materials: a Look at Microstructure in Seashells

2001 ◽  
Vol 678 ◽  
Author(s):  
Emil Zolotoyabko ◽  
John P. Quintana
Keyword(s):  
Structural Characteristics ◽  
Depth Resolution ◽  
Three Dimensions ◽  
Polycrystalline Materials ◽  
X Ray Diffraction ◽  
Penetration Length ◽  
X Ray ◽  
Strain Components ◽  
Laminated Structures ◽  
Non Destructive

AbstractWe developed a depth-sensitive x-ray diffraction technique in which diffraction profiles are measured at x-ray energies that are varied by small steps. The method is intended for synchrotron beam lines and provides non-destructive mapping of structural characteristics in inhomogeneous polycrystalline materials. Depth resolution is achieved due to an energy dependence of the x-ray penetration length. Application of this technique to seashells allowed us to extract spatial distributions of preferred orientation and strain components, which revealed pronounced variations of the shell microstructure in three dimensions. The results shed light on “engineering solutions” by mollusk. The developed technique can be used to characterize various laminated structures and composite materials.

Non-Destructive Analysis of Surface Stresses Using Grazing Incident X-Ray Diffraction

2005 ◽  
Vol 490-491 ◽  
pp. 143-148
Author(s):  
Chedly Braham ◽  
Andrzej Baczmanski ◽  
Wilfrid Seiler ◽  
N. Shiraki
Keyword(s):  
Sample Surface ◽  
Polycrystalline Materials ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Surface Layers ◽  
X Ray ◽  
Lattice Strains ◽  
Crystallographic Planes ◽  
Destructive Measurement ◽  
Non Destructive

The X-ray diffraction measurements based on the grazing incident geometry were applied to determine lattice strains in polycrystalline materials. This method enables a non-destructive measurement at chosen depth below the sample surface. The volume, for which the stress is measured, is well defined and it does not vary during experiment. The multireflection method was used for analysis of the experimental results since the interplanar spacings were measured for various orientation of the scattering vector as well as for various crystallographic planes {hkl}. Applying two different wavelengths of X- ray radiation and various incident angles non-destructive measurements of the residual stresses in function of penetration depth were performed. The variation of stresses in plastically deformed surface layers of steel samples was successfully determined and the values of the stresses were confirmed by standard diffraction measurement.

Three Dimensional Characterization of Grain Structures by EBSP and 3DXRD

2007 ◽  
Vol 558-559 ◽  
pp. 751-756 ◽  
Author(s):  
Kristofer Hannesson ◽  
Dorte Juul Jensen
Keyword(s):  
Three Dimensional ◽  
Polycrystalline Materials ◽  
Serial Sectioning ◽  
X Ray Diffraction ◽  
X Ray ◽  
3D Structures ◽  
3 Dimensional ◽  
Grain Structures ◽  
Non Destructive

Grain structures in polycrystalline materials are typically three dimensional (3D) structures, but by far the most characterizations of grain structures are done by microscopy and are thus limited to 2D. In the present work 3D grain structures in a well-annealed cylindrical aluminium (AA1050) sample is characterized and analyzed. The characterization is done by 2 methods i) by non-destructive 3-dimensional x-ray diffraction (3DXRD) ii) by serial sectioning and subsequent EBSP mapping of entire circular 2D sample sections; 50 sections are mapped In total 333 grains are reconstructed. It is found that the 3D grain morphologies can be quite complex in particular for the larger grains, the number of neighbours varies significantly and values above 20 are not unusual. When the results from the 2 methods are compared, it is found that the crystallographic agreement is very good and within experimental uncertainties. Slightly more significant differences are found when the reconstructed grain morphologies are compared. Reasons for this are discussed.

Strain and Compositional Analysis of InGaN/GaN Layers

2000 ◽  
Vol 639 ◽  
Author(s):  
Sérgio Pereira ◽  
Maria. R. Correia ◽  
Estela Pereira ◽  
C. Trager-Cowan ◽  
F. Sweeney ◽  
...  
Keyword(s):  
Driving Force ◽  
Rutherford Backscattering Spectrometry ◽  
Compositional Analysis ◽  
Depth Resolution ◽  
Indium Content ◽  
Rutherford Backscattering ◽  
X Ray Diffraction ◽  
Strained Layers ◽  
X Ray ◽  
Strain Components

ABSTRACTWe investigate strain and composition of epitaxial single layers of wurtzite InxGa1−xN (0<x<0.25) grown by MOCVD on top of GaN/Al203 substrates. It is shown that significant inaccuracies may arise in composition assessments if strain in InxGa1−xN/GaN heterostructures is not properly taken into account. Rutherford backscattering spectrometry (RBS) measures composition, free from the effects of strain and with depth resolution. Using X-ray diffraction (XRD) we measure both a- and c- parameters of the strained wurtzite films. By measuring both lattice parameters and solving Hooke's equation, a good estimation for composition can be obtained from XRD data. The agreement between RBS and XRD data for composition allows reliable values for perpendicular (εzz) and parallel strain components ( (εxx) to be determined. RBS and depth resolved cathodoluminescence (CL) measurements further indicate that the indium content is not uniform over depth in some samples. This effect occurs for the most strained layers, suggesting that strain is the driving force for compositional pulling.

Use of Image-Processing Tools for Texture Analysis of High-Energy X-ray Synchrotron Data

1998 ◽  
Vol 31 (5) ◽  
pp. 647-653 ◽  
Author(s):  
R. Fisker ◽  
H. F. Poulsen ◽  
J. Schou ◽  
J. M. Carstensen ◽  
S. Garbe
Keyword(s):  
Image Processing ◽  
Nonlinear Least Squares ◽  
High Energy ◽  
Three Dimensions ◽  
Polycrystalline Materials ◽  
Data Sets ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray

The introduction of synchrotron beamlines for high-energy X-ray diffraction raises new possibilities for texture determination of polycrystalline materials. The local texture can be mapped out in three dimensions and texture developments can be studiedin situin complicated environments. However, it is found that a full alignment of the two-dimensional detector used in many cases is impractical and that data-sets are often partially subject to geometric restrictions. Estimating the parameters of the traces of the Debye–Scherrer cones on the detector therefore becomes a concern. Moreover, the background may vary substantially on a local scale as a result of inhomogeneities in the sample environmentetc. A set of image-processing tools has been employed to overcome these complications. An automatic procedure for estimating the parameters of the traces (taken as ellipses) is described, based on a combination of a circular Hough transform and nonlinear least-squares fitting. Using the estimated ellipses the background is subtracted and the intensity along the Debye–Scherrer cones is integrated by a combined fit of the local diffraction pattern. The corresponding algorithms are presented together with the necessary coordinate transform for pole-figure determination. The image-processing tools may be useful for the analysis of noisy or partial powder diffraction data-sets in general, provided flat two-dimensional detectors are used.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Highlights in the history of X-ray topography1

1995 ◽  
Vol 210 (6) ◽  
Author(s):  
A. R. Lang
Keyword(s):  
Magnetic Domain ◽  
Diffraction Theory ◽  
Dislocation Loops ◽  
X Ray Diffraction ◽  
X Ray ◽  
Domain Structures ◽  
Structure Factors ◽  
History Of ◽  
Dislocation Sources ◽  
Non Destructive

AbstractX-ray topography provides a non-destructive method of mapping point-by-point variations in orientation and reflecting power within crystals. The discovery, made by several workers independently, that in nearly perfect crystals it was possible to detect individual dislocations by X-ray diffraction contrast started an epoch of rapid exploitation of X-ray topography as a new, general method for assessing crystal perfection. Another discovery, that of X-ray Pendellösung, led to important theoretical developments in X-ray diffraction theory and to a new and precise method for measuring structure factors on an absolute scale. Other highlights picked out for mention are studies of Frank-Read dislocation sources, the discovery of long dislocation helices and lines of coaxial dislocation loops in aluminium, of internal magnetic domain structures in Fe-3 wt.% Si, and of stacking faults in silicon and natural diamonds.

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