Refraction computed tomography

Abstract

For the first time metal matrix composites have been investigated by 3D computed tomography combined with enhanced interface contrast due to X-ray refraction. The related techniques of refraction topography and refraction computed tomography have been developed and applied during the last decade to meet the actual demand for improved non-destructive characterization of high performance composites, ceramics and other low-density materials and components. X-ray refraction is an optical effect that can be observed at small scattering angles of a few minutes of arc as the refractive index n of X-rays is nearly unity (n = 1 − 10−6). Due to the short X-ray wavelength, the technique determines the amount of inner surfaces and interfaces of nanometer dimensions. The technique can solve many problems in understanding micro and sub microstructures in materials science. Applying 3D refraction computed tomography, some questions could be clarified for a better understanding of fatigue failure mechanisms under cyclic loading conditions.

Real-Time X-ray Study of Nylon-6 Fibers during Dehydration: Equatorial Small-Angle Scattering is Due to Surface Refraction

“…However, SAXS due to refraction from fibers was observed in 1987, 27 and the refracted signal is now the basis for medical imaging and the NDE of composites. [28][29][30] Water has a very significant effect on the processing and properties of polyamides including nylon-6. Changes in microstructure that may underlie these changes in properties are therefore of interest in themselves.…”

“…It has been generally assumed that this scattering will be too weak to see in the regular SAXS range, as fibers 20 μm in diameter will have a tiny surface area compared to that of the fibrils, which are ∼10 nm in diameter. However, SAXS due to refraction from fibers was observed in 1987, and the refracted signal is now the basis for medical imaging and the NDE of composites. − …”

Nondestructive Testing of Polymers and Polymer–Matrix Composites

“…NDT with a synchrotron source for X-ray refraction in PMC is described in Ref. 164. Nearedge X-ray absorption fine structure (NEXAFS) and related X-ray techniques provide information on composition and morphology of polymers on a microscopic scale (see X-RAY MICROSCOPY).…”

A Review of X‐Ray Imaging at the BAMline(BESSY II)

“…A double-multilayer monochromator (DMM) of the BAMline delivers monochromatic X-rays for the SXCTs. [4] With the monochromatic beam the attenuation follows the Lambert-Beer law (exponential) and a suited reconstruction software computes the 3D distribution of attenuation coefficients within the sample. One of the most important advantages of SXCT with respect to laboratory XCT is the absence of the so-called "beam hardening" artefacts, which occur if one uses a polychromatic X-ray beam.…”