To perform 3D crystallographic phases imaging inside polycrystalline single phase but also multi phases samples, a new method combining X-ray powder diffraction with scanning tomography has recently been proposed [1-3]. One major advantage of this technique (written here Xray Diffraction-Computed Tomography (XRD-CT)) is that contrary to others methods no a priori knowledge on the phases present in the sample (crystallographic structure ...) is required. The spatial resolution of this technique is directly linked to the beam size incoming on the sample and micron-scale resolution has already been demonstrated [1]. The capability of the method to reach higher spatial resolution and therefore to access nanomaterials characterization is linked to the focusing capabilities of the beamline. Since the XRD-CT technique is based on powder diffraction methods, Rietveld refinement can be partly included in the data processing just like for 2D-XRD. A previous study based on a quite similar approach for XRD-CT data treatment has been recently proposed [2]. We report in this paper the first attempt to perform XRD-CT measurements on the ID22NI hard X-ray nanoprobe of the European Synchrotron Radiation Facility (ESRF) with a beam size of 150×220 nm [4]. The studied sample is a small spherical (about 50 µm in diameter) annealed UMo particle and a multiphases interface buried about 5 µm under the surface has been especially characterized. Moreover the interest of Rietveld method for analyzing the XRD-CT data will be evaluated and the possibility to derive from such an approach the weight fraction of the various phases inside each voxel will be discussed. Finally, the advances provided by this experiment on our understanding of the UMo/Al metallurgy will be presented. [1] Bleuet, P.; Welcomme, E.; Dooryhee, E.; Susini, J.; Hodeau, J.L. and Walter, P.; Nature Materials, 2008, 7, 468. [2] De Nolf, W.; Janssens, K.; Surface and Interface Analysis published online 10Nov. 2009. [3] Artioli, G.; Cerulli, T.; Cruciani, G.; Dalconi, M.C.; Ferrari, G.; Parisatto, M.; Tucoulou R; Anal. Bioanal. Chem., 2010, DOI: 10.1007/s00216-010-3649-0. [4] Mokso, R.; Cloetens, P.; Maire, E.; Ludwig, W.; Buffiere, J. Y.; Appl. Phys. Lett., 2007, 90, 144104. Combining the principles of X-ray diffraction imaging (topography) and image reconstruction from projections (tomography), it has recently become possible to map the 3D grain microstructure in a range of polycrystalline materials [1,2]. Associating this 3D orientation mapping with conventional attenuation and/or phase contrast tomography yields a non-destructive characterization technique, enabling time-lapse observation of crystal growth, deformation and damage mechanisms in the bulk of structural materials. The capabilities and limitations., as well as future perspectives of this new characterization approach will be discussed and illustrated on selected application examples. ludwig@esrf.fr [1] Poulsen, H.F. Three-dimensional X-ray diffraction microscopy. Polychromatic microdiffraction has been devel...

Quantitative characterization of the microstructure of cement-based materials is of fundamental importance for assessing the performance and durability of the final products. However, accessing the three-dimensional microstructural information of hydrating cement pastes without introducing any perturbation is not trivial. Recently, a novel non-invasive method based on X-ray diffraction computed microtomography (XRD-CT) has been applied to cement-based materials, with the aim of describing the three-dimensional spatial distribution of selected phases during the hydration of the cement paste. This paper illustrates a method based on XRD-CT, combined with Rietveld-based quantitative phase analysis and image processing, which provides quantitative information relative to the distribution of the various phases present in the studied samples. In particular, it is shown how this method allows the estimation of the local volume fraction of the phase ettringite within a hydrating cement paste, and construction of a three-dimensional distribution map. Application of this method to the various constituents of a cementitious material, or, more generally, of a composite polycrystalline material, may provide a non-invasive tool for three-dimensional microstructural quantitative characterization

The present work describes some new improvements concerning the analysis of cement hydration processes using ‘pencil-beam’ synchrotron X-ray diffraction tomography. (i) A new filtering procedure, applied to the diffraction images, has been developed to separate the powder-like contribution from that of the grains in the diffraction images. (ii) In addition to improving the quality of the diffraction images for the subsequent analysis and tomographic reconstruction, the filtering procedure can also be used to perform a qualitative analysis of the crystallite size distribution, whenever the more standard approaches cannot be applied. (iii) Given the importance of the calcium silicate hydrate phase (C–S– H) in cements, a procedure to obtain its spatial distribution using the diffraction signal has been successfully applied, even though C–S–H is a highly disordered phase, almost amorphous to X-ray diffraction. (iv) The main result of this study has been to show that, in spite of the long measurement times required, it is possible to use in situ experiments at different aging times of cement pastes to monitor the cement evolution. This allowed the evolution of the microstructure during the acceleration and deceleration periods of the hydration process to be checked with unprecedented detail, since the quantitative spatial distribution of each phase (including C–S–H) dissolved or precipitated in the sample has been obtained. The reported approach opens up a range of opportunities for the investigation of complex multiphase systems and processes, including hydration and microstructural development in cements

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The application of synchrotron radiation X-ray computed micro-tomography (SR X-μCT) as a non-invasive approach to the microstructural investigation of Portland cement binders during hydration is presented. The two- and three-dimensional µm-scale imaging of undisturbed samples at hydration ages from ~1.5 h to 3 days is used to obtain a direct visualization of the spatial and temporal relationships between different cement paste components. The microstructural evolution of two cementitious systems during the early stages of hydration is successfully monitored from the comparison of tomographic slices and volumes, clearly showing the progressive growth of hydration phases; the changes in the amount of porosity and unreacted clinker are also quantified. Some critical issues related to the experimental setup and data processing are addressed and discussed as well. Furthermore, a simple procedure to estimate the mean X-ray absorption coefficient of cement pastes from X-ray radiographs is illustrated. The results confirm the potentialities of synchrotron-based X-ray computed micro-tomography for the three-dimensional investigation of µm-scale modifications in hydrating cement pastes with an adequate time resolution, thus providing a real in-situ monitoring of the microstructural evolution of such complex materials