Fast In Situ Nanotomography at ESRF
Résumé
X-ray computed tomography (CT) is a very powerful technique that provides nondestructively direct access to the three-dimensional morphology of a specimen. It is extensively used in different domains like medicine, paleontology and biology. Today it is even possible to perform real time acquisition to observe in situ damaging and processes occurring in materials. Thanks to continuous improvements in spatial resolution, CT has been recently extended to the nanoscale [1]. It is a very efficient technique to study the performance of many advanced materials, which is mostly determined by the arrangement of their nanostructure [2]. Nevertheless, the combination of fast real time, in situ and CT in the nanometer regime remains a key challenge. We present here, in situ hard X-ray nanotomography experiments with an unprecedented combination of nanometer pixel size and fast acquisition time at high temperature. ID16B is a nano-analysis beamline built during phase I of the European Synchrotron Radiation Facility (ESRF) and opened to users since early 2014. The beamline configuration offers an improved lateral resolution (50x50 nm 2), a monochromatic nanobeam tunable in a large energy range (6-30 kV) with high flux (10 9 to 10 12 ph/s), and large flexibility capable of in situ experiments [3]. Combination of various techniques such as X-ray fluorescence (XRF), X-ray absorption (XANES), X-ray excited optical luminescence (XEOL) and X-ray diffraction (XRD) as well as magnified phase contrast nanotomography allows multi-approach studies to be performed. Taking advantage of the high stability offered on ID16B and magnified phase contrast imaging, we developed a fast in situ nanoimaging setup [4] that allows high temperature experiments to be performed with an unparalleled combination of nanometer pixel size (35nm) and fast acquisition (<10s). An intense X-ray beam (10 12 ph/s) is focused down to a spot size of 50×50 nm 2 using two multilayer-coated Si mirrors in Kirkpatrick-Baez (KB) configuration under pink beam mode (∆E/E=10-2). As illustrated in Figure 1 the sample located in the microheater (200 to 900°C) is positioned out of the focal plane in projection geometry. While rotating the sample, high-resolution images are continuously collected by a PCO edge 5.5 detector (equipped with a CMOS sensor) through an Optique Peter high resolution X-Ray imaging microscope (equipped with an X10 Olympus objective). To date, fastest full tomographic scans are acquired in 7s. Pixel size and field of view depend on the sample position between the focal plane and the detector. Any pixel size between 27 and 650 nm is available and multi-scale measurements are easily achievable. Several real time studies that investigates nanostructure evolution in materials, have been already performed: (i) ceramics sintering (ii) light alloys damage (iii) fuel cells degradation... For example, spherical soda-limes glass particles have been isothermally treated at 670°C, and continuously scanned (timescan:33s) during approximately 2 hours with a pixel size of 100nm. The microstructural evolution during ceramic powders sintering leads to controlled porosity but also formation of defects. 3D observations of the process at the micro-scale already gave important information on the densification process from rearrangement phenomena point of view. While the 3D movie resulting from in situ