Position sensitive x-ray scattering (XRS) of complex artifical and biological materials: towards XRS-microscopy

The mechanical properties of many artificial and biological materials are determined by their structure at many levels of hierarchical organization. X-ray scattering (XRS) is a powerful tool for the investigation of the structure of materials in the nanometer range. However, due to the inhomogeneous character of composite materials, it is essential to perform position resolved measurements of the structure over large areas of the specimen, in order to get a reasonable description of the material. In this application, we propose to develop a XRS-microscopy system to be used at a synchrotron source for position and time-resolved investigation of complex materials. The system consists of an x-ray sensitive CCD-camera which collects spectra with video frequency. Hence, time-resolved measurements may be performed in cases where anistropicstructures develop at a reasonably slow rate (for example, diffusion controlled phase transformations in materials). By moving the specimen while data are collected, the time resolution is transformed into a position resolution on the sample. The system shall be developed at the synchrotrone Trieste, but should be usable also at other synchrotron sources, if required. The first problems to be investigated result from ongoing research activities on the relation between the structure of materials (particularly at the nanometer level) and their mechanical properties. They include 1. The influence of (inhomogeneous) external stresses on the precipitate microstructure in nickel-based superalloys, 2. The kinetics of oxide precipitate formation in the vicinity of the oxidation front during internal oxidation of a metal alloy, 3. The distribution of the wood cell wall structure in large section of native wood (like branches from a tree) in relation to typical stress distributions in the material. 4. The characterization of the mineral structure in human bone after different osteoporosis treatments or during fracture healing.