Surface Xrd

This is an X-ray diffraction pattern formed when X-rays are focused on a crystalline material, in this case a protein. Each dot, called a reflection, forms from the coherent interference of scattered X-rays passing through the crystal.

Surface X-ray diffraction (SXRD) is a method to observe the atomic configuration or molecular orientation at surfaces or interfaces (Robinson in Handbook on synchrotron radiation, pp 221–266, 1991; Fuoss et al. In Synchrotron radiation research: advances in surface and interface science. Adiabatic potential energy surface of the Jahn-Teller complexes in CaF2:Ni2þ crystal determined from experiment on ultrasonic attenuation // Journal. The surface stress–strain relation and yield strength of the SAF2507 DSS were determined by in situ XRD stress analysis combined with tensile test. In this method, uniaxial tensile loading was applied gradually along the longitudinal direction, and the longitudinal strain εa at each loading step was measured by a strain gage. Sample preparation. Proper sample preparation is one of the most important requirements in the analysis of powder samples by X-ray diffraction.This statement is especially true for soils and clays that contain finely divided colloids, which are poor reflectors of x-rays, as well as other types of materials such as iron oxide coatings and organic materials that make characterization by XRD more.

X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystal structure, chemical composition, and physical properties of materials and thin films. These techniques are based on observing the scatteredintensity of an X-ray beam hitting a sample as a function of incident and scattered angle, polarization, and wavelength or energy.

Note that X-ray diffraction is now often considered a sub-set of X-ray scattering, where the scattering is elastic and the scattering object is crystalline, so that the resulting pattern contains sharp spots analyzed by X-ray crystallography (as in the Figure). However, both scattering and diffraction are related general phenomena and the distinction has not always existed. Thus Guinier's classic text[1] from 1963 is titled 'X-ray diffraction in Crystals, Imperfect Crystals and Amorphous Bodies' so 'diffraction' was clearly not restricted to crystals at that time.

Scattering techniques

Elastic scattering

• X-ray diffraction or more specifically Wide-angle X-ray diffraction (WAXD)
• Small-angle X-ray scattering (SAXS) probes structure in the nanometer to micrometer range by measuring scattering intensity at scattering angles 2θ close to 0°.
• X-ray reflectivity is an analytical technique for determining thickness, roughness, and density of single layer and multilayer thin films.
• Wide-angle X-ray scattering (WAXS), a technique concentrating on scattering angles 2θ larger than 5°.
Spectrum of various inelastic scattering processes that can be probed with inelastic X-ray scattering (IXS).

Inelastic X-ray scattering (IXS)

In IXS the energy and angle of inelastically scattered X-rays are monitored, giving the dynamic structure factor${displaystyle S(mathbf {q} ,omega )}$. From this many properties of materials can be obtained, the specific property depending on the scale of the energy transfer. The table below, listing techniques, is adapted from.[2] Inelastically scattered X-rays have intermediate phases and so in principle are not useful for X-ray crystallography. In practice X-rays with small energy transfers are included with the diffraction spots due to elastic scattering, and X-rays with large energy transfers contribute to the background noise in the diffraction pattern.

TechniqueTypical Incident Energy, keVEnergy transfer range, eVInformation on:
Compton scattering1001,000Fermi Surface Shape
Resonant IXS (RIXS)4-200.1 - 50Electronic Structure & Excitations
Non-Resonant IXS (NRIXS)100.1 - 10Electronic Structure & Excitations
X-ray Raman scattering1050 - 1000Absorption Edge Structure, Bonding, Valence
High resolution IXS100.001 - 0.1Atomic Dynamics,Phonon Dispersion

References

1. ^Guinier, A. (1963). X-ray diffraction in Crystals, Imperfect Crystals and Amorphous Bodies. San Francisco: W.H. Freeman & Co.
2. ^Baron, Alfred Q. R (2015). 'Introduction to High-Resolution Inelastic X-Ray Scattering'. arXiv:1504.01098 [cond-mat.mtrl-sci].

 Wikimedia Commons has media related to X-ray diffraction.
• Introduction to X-ray Diffraction at University of California, Santa Barbara

The X-ray Diffraction (XRD) residual stress measurement method determines if critical components can withstand the load and stress of operating conditions.

XRD is the method of choice for high-resolution measurement of surface and near-surface residual stress, where most stress-related cracking occurs.

How Does It Work?

XRD can be used to determine residual stresses in any direction within the sample surface. Measurements are made with respect to position over a sample’s surface and incrementally with depth.

Surface Xrd Vs

The XRD method is based on linear elastic stress-strain theory and involves measuring the angle of maximum diffracted intensity when a polycrystalline sample is irradiated. From the angle of the diffraction peak, the lattice spacing of a specific set of lattice planes can be calculated using Bragg’s law.

For a stressed sample, the lattice spacing varies with angular orientation of the lattice planes. This change in lattice spacing is used to calculate the strain from which the stress can be determined.

X-Ray Diffraction Features:

• XRD can be used on any polycrystalline material, including metals and ceramics, and tests can be performed on a large array of sizes and geometries.
• XRD provides the highest spatial and depth resolution of any measurement method.
• XRD is the preferred method to measure residual stresses from manufacturing processes such as turning, grinding, milling, welding, shot peening, carburizing and induction hardening, or for high spatial resolution adjacent to fractures, welds, and similar features.
• XRD can be used to determine residual stresses in any direction within the plane of a sample surface. Measurements can be made with respect to position over a sample’s surface and incrementally with depth.
• XRD can be used to measure the surface residual stresses non-destructively. In order to measure residual stress incrementally with depth, the material is removed by an electropolish process to ensure residual stresses are not introduced during material removal.

How are Lambda’s X-ray diffraction services superior?

• Lambda uses diffractometers that are custom developed and built in-house specifically for residual stress measurement.
• XRD systems are a Bragg-Brentano geometry with a large goniometer radius allowing for higher accuracy measurement compared to standard portable systems.
• Our diffractometers are capable of accepting a large range of sample sizes.
• With more than half a million completed measurements, over 100 technical papers published, and authorship of the American Society for Metals “X-ray Diffraction Residual Stress Techniques,” Lambda is the world’s premier provider of XRD residual stress analysis.
Diffractometers
Lambda uses diffractometers that are custom developed and built in-house specifically for residual stress measurement. XRD systems are a Bragg-Brentano geometry with a large goniometer radius allowing for higher accuracy measurement compared to standard portable instruments. Our diffractometers are capable of accepting a large range of sample sizes.
X-Ray Detectors
Lambda uses state of the art, high-performance solid-state x-ray detectors for residual stress measurements. Our detectors have the highest energy resolution available, providing a high-intensity diffraction peak with very low background radiation, for more accurate assessment of the diffraction peak position.
X-Ray Elastic Constant Determination

Lambda measures the x-ray elastic constants required to calculate strain by residual stress measurement. It is necessary to determine the x-ray elastic constant for the specific set of crystallographic planes being measured. Lambda has a database containing several hundred x-ray elastic constants.

Electropolishing Layer Removal

Subsurface residual stress measurements are recommended in order to fully understand the residual stress distribution. Electropolishing is the only viable means of removing material without inducing residual stresses. Lambda has several specially formulated electropolishing solutions to provide a finish and flatness necessary for accurate residual stress measurement. Electropolishing depths can be measured to a precision of 0.0001 in. (0.003 mm).

Material Property Prediction from Line Broadening

Lambda has developed methods of predicting material property information using x-ray diffraction testing with line broadening. Line broadening data collected during a standard residual stress measurement can provide material information such as cold working and hardness.

Automated Mapping

Lambda has developed automated sample translation tables to map the residual stresses via x-ray diffraction analysis. The translation system allows our technicians to easily measure a precise set of points automatically. Results can be plotted to provide a high-resolution residual stress contour describing areas of high gradients and peak residual stresses.

Automated Depth Profiling

Lambda has designed and patented a device that performs automated residual stress depth profiling. The device accepts two samples. Residual stress measurements by x-ray diffraction are made on one sample while the other sample is electropolished — the device alternately electropolishes and measures both samples to rapidly obtain residual stress vs. depth on both samples.

Questions about XRD testing or other residual stress measurement needs?