X-ray diffraction topography image materials by molecular probe

Abstract

Crystallinity, composition, homogeneity and anisotropy determine the mechanical properties of materials significantly, but the performance of most non-destructive techniques is too poor for measuring these micro structures as they are optimized for finding individual flaws/defects. X-ray (wide angle) Diffraction Topography by single beam scanning images molecular information at a spatial resolution of several ten micrometers even in three dimensions. Especially for the non-destructive characterization of composite materials, they provide additional capabilities by crystallographic contrast by the molecular/atomic probe. The different material phases of compounds and their molecular orientation can be imaged e.g. fibers or polymer chain orientation in composites: A sample is scanned or rotated, while only part of the scattering pattern is pointing at an X-ray detector area. Three different methods have been developed: i) planar X-ray Scanning Topography at one or more pre-selected scattering angles provides high contrast of different phases of components. ii) X-Ray Rotation Topography reveals the texture angle of composite fibers and chain polymers. iii) X-ray Diffraction Microscopy images the texture and phase distribution of transversal sections of the material. The principles of Wide Angle X-Ray Diffraction Topography are explained and examples of investigations will be presented. They combine the advantages of radiographic imaging and crystal structure information. The applied X-ray energies are much lower than in NDT radiography, which recommends preferably the application to light weight materials.