No abstract

Analyser-based imaging expands the performance of X-ray imaging by utilizing not only the absorption properties of X-rays but also the refraction and scatter rejection (extinction) properties. In this study, analyser-based computed tomography has been implemented on imaging an articular cartilage sample, depicting substructural variations, without overlay, at a pixel resolution of 3.6 microm.

X-Ray Refraction Topography techniques are based on Ultra Small Angle Scattering by micro structural elements causing phase related effects like refraction and total reflection at a few minutes of arc as the refractive index of X-rays is nearly unity (1⋅10 -5 ). The extraordinary contrast of inner surfaces is far beyond absorption effects. Scanning of specimens results in 2D-imaging of closed and open pore surfaces and crack surface density of ceramics and foams. Crack orientation and fiber/matrix debonding in plastics, polymers and ceramic composites after cyclic loading and hydro thermal aging can be visualized. In most cases the investigated inner surface and interface structures correlate to mechanical properties. For the exploration of Metal Matrix Composites (MMC) and other micro structured materials the refraction technique has been improved to a 3D Synchrotron Refraction Computed Tomography (SR-CT) test station. The specimen is situated in an X-ray beam between two single crystals. Therefore all sample scattering is strongly suppressed and interpreted as additional attenuation. Asymmetric cut second crystals magnify the image up to 50 times revealing nanometer resolution. The refraction contrast is several times higher than "true absorption" and results in images of cracks, pores and fiber debonding separations below the spatial resolution of the detector. The technique is an alternative to other attempts on raising the spatial resolution of CT machines. The given results yield a much better understanding of fatigue failure mechanisms under cyclic loading conditions.

Abstract. For the purpose of micro structural characterization X-ray topography reveals the spatially resolved scattering of materials and small components. It combines the advantages of radiographic imaging and the analytical information of wide and small angle X-ray scattering like phase distribution, texture, micro cracks, interfaces and pores. Scanning techniques at selected scattering conditions permit the topographic characterization of any crystalline or amorphous solid or liquid. Topographic methods and applications for the purposes of research, quality control and damage evaluation are presented.