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In the energy production and transportation industries, numerous metallic structures may be subjected to at least several billions of cycles, i.e. loaded in the very high cycle fatigue domain (VHCF). Therefore, to design structures in the VHCF domain, a reliable methodology is necessary. One useful quantity to characterize plastic activity at the microscopic scale and fatigue damage evolution is the mechanical work supplied to a material. However, the estimation of this mechanical work in a metal during ultrasonic fatigue tests remains challenging. This paper aims to present an innovative methodology to quantify this. An experimental procedure was developed to estimate the mechanical work from stress and total strain evolution measurements during one loading cycle with a time accuracy of about 50 ns. This was achieved by conducting time-resolved X-ray diffraction coupled to strain gauge measurements at a synchrotron facility working in pulsed mode (single-bunch mode). [ABSTRACT FROM AUTHOR]

Among many phase change materials, Ge‐rich GeSbTe (GST) alloys are of considerable interest due to their high thermal stability, a specification required for the next generation of embedded digital memories. This stability results from the fact that these alloys do not crystallize congruently but experience phase separation forming Ge and GST‐225 nanocrystals upon crystallization. However, the details of the crystallization process remain unclear. Combining in situ X‐ray diffraction studies during isothermal annealing and ex situ (scanning) transmission electron microscopy ((S)TEM) observations, the successive phases through which these alloys crystallize are identified. At low temperature (310 °C), the homogeneous amorphous material undergoes phase separation during wherein small regions of different Ge contents are formed. After a long incubation time, Pnma GeTe embryos first crystallize and trigger the heterogeneous crystallization of the Ge cubic phase. While the Ge phase progressively builds up through the addition of new small Ge crystals, cubic GeTe forms. At this point, the microstructure ceases to evolve, and Sb is still dispersed and contained within some remaining amorphous matrix surrounding Ge and GeTe crystals. Higher annealing temperatures (typically 400 °C) are needed to force Sb to diffuse and get incorporated into the GeTe grains to form cubic Ge2Sb2Te5. [ABSTRACT FROM AUTHOR]

To passivate Si−SiO2 dangling bonds, metal–oxide–semiconductor field‐effect transistor devices are usually treated with hydrogen. Herein, the effects of such a treatment on the crystallization behavior on N‐doped, Ge‐rich Ge2Sb2Te5 phase‐change materials for memory applications are investigated using synchrotron X‐ray diffraction (XRD) in situ during heat treatment. Uniform thin films, and laterally confined, metallized ones (simulating devices of different complexity) of initially amorphous N‐doped GGST are investigated. The specimens are heated up to 450–500 °C at a rate of 2 °C/min. Some of the specimens are treated with H/D; the equivalent untreated specimen is investigated for each of them. Crystallization onsets are estimated by quantification of the crystallized quantity during material transformation from the XRD patterns. In thin films, the hydrogen treatment results in lowered crystallization temperatures of the emerging cubic, metastable Ge2Sb2Te5 phase. Its trigonal, thermodynamically stable polymorph always forms, but its crystallization temperature is unchanged. Patterned and metallized samples show less differences, are strongly textured, and no trigonal phase is observed. It is shown that certain questions might only be answered at large‐scale facilities where high energy photons are available at high flux, allowing data acquisition during the annealing process with a temperature resolution sufficient for a fine description of the sample transformation. [ABSTRACT FROM AUTHOR]

An optimized synchrotron‐based X‐ray diffraction method is described for the direct and efficient measurement of crystallite phase and orientation at micrometre resolution across textured polycrystalline samples of millimetre size (high scale dynamics) within a reasonable time frame. The method is demonstrated by application to biomineral fish otoliths. Otoliths are calcium carbonate accretions formed in the inner ears of vertebrates. Fish otoliths are essential biological archives, providing information for individual age estimation, the study of population dynamics and fish stock management, as well as past environmental and climatic conditions from archaeological specimens. Here, X‐ray diffraction mapping is discussed as a means of describing the mineralogical structure and microtexture of otoliths. Texture maps could be generated with a few a priori hypotheses on the aragonitic system. Full‐section imaging allows quantitative intercomparison of crystal orientation coupled to microstructural description, across the zones of the otoliths that represent distinctive mineral organization. It reveals the extents of these regions and their internal textural structure. Characterization of structural and textural correlations across whole images is therefore proposed as a complementary approach to investigate and validate the local in‐depth nanometre‐scale study of biominerals. The estimation of crystallite size and orientational distribution points to diffracting domains intermediate in size between the otolith nanogranules and the crystalline units, in agreement with recently reported results. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) are two complementary structural techniques. Their combination improves the understanding of the effect of pressure on materials as illustrated by examples taken from studies on different types of materials (semiconductors, molecular solid, ferroelectric perovskite and gas mixture). The introduction of nanopolycrystalline diamonds anvils has extended XAS to high-energy edges with the possibility to use energy-scanning XAS beamlines where XRD can be performed in addition to XAS experiments. [ABSTRACT FROM PUBLISHER]

Scanning hard X-ray spectro-microscopic imaging opens unprecedented possibilities in the study of inhomogeneous samples at different length-scales. It gives insight into the spatial variation of the major and minor components, impurities and dopants of the sample, and their chemical and electronic states at micro- and nano-meter scales. Measuring, modelling and understanding novel properties of laterally confined structures are now attainable. The large penetration depth of hard X-rays (several keV to several 10 keV beam energy) makes the study of layered and buried structures possible also in in situ and in operando conditions. The combination of different X-ray analytical techniques complementary to scanning spectro-microscopy, such as X-ray diffraction, X-ray excited optical luminescence, secondary ion mass spectrometry (SIMS) and nano-SIMS, provides access to optical characteristics and strain and stress distributions. Complex sample environments (temperature, pressure, controlled atmosphere/vacuum, chemical environment) are also possible and were demonstrated, and allow as well the combination with other analysis techniques (Raman spectroscopy, infrared imaging, mechanical tensile devices, etc.) on precisely the very same area of the sample. The use of the coherence properties of X-rays from synchrotron sources is triggering emerging experimental imaging approaches with nanometer lateral resolution. New fast analytical possibilities pave the way towards statistically significant studies at multilength- scales and three dimensional tomographic investigations. This paper gives an overview of these techniques and their recent achievements in the field of material sciences. [ABSTRACT FROM AUTHOR]

Structural anisotropy, for example texture, may govern important physical properties of thin film, such as electrical, magnetic and/or mechanical ones. Texture (orientation information) is typically observed and quantified by the measurement of so-called pole figures. An optimized experimental approach implemented at the DiffAbs beamline (Synchrotron SOLEIL) is presented here. Using an X-ray pixel area detector and synchrotron radiation sources, a complete pole figure (with resolutions adapted for metallic textured thin films, typically of the order of a few degrees) can be measured in time intervals as short as one minute. The necessary corrections enabling complete pole figure retrieval from the experimental data using this optimized approach are provided and discussed. A gain in measuring time by up to two orders of magnitude is found with respect to the use of a point detector (classical approach) under the same experimental conditions. Data measured using these two approaches are shown, compared and discussed. [ABSTRACT FROM AUTHOR]

X-ray diffraction techniques are used in imaging mode in order to characterize micrometre-sized objects. The samples used as models are metal-oxide tunnel junctions made by optical lithography, with lateral sizes ranging from 150 µm down to 10 µm and various shapes: discs, squares and rectangles. Two approaches are described and compared, both using diffraction contrast: full-field imaging (topography) and raster imaging (scanning probe) using a micrometre-sized focused X-ray beam. It is shown that the full-field image gives access to macroscopic distortions ( e.g. sample bending), while the local distortions, at the micrometre scale ( e.g. tilts of the crystalline planes in the vicinity of the junction edges), can be accurately characterized only using focused X-ray beams. These local defects are dependent on the junction shape and larger by one order of magnitude than the macroscopic curvature of the sample. [ABSTRACT FROM AUTHOR]

Natural rubber exhibits remarkable mechanical fatigue properties usually attributed to strain-induced crystallization. To investigate this phenomenon, an original experimental set-up that couples synchrotron radiation with a homemade fatigue machine has been developed. Diffraction-pattern recording is synchronized with cyclic loading in order to obtain spatial distributions of crystallinity in the sample at prescribed times of the mechanical cycles. Then, real-time measurement of crystallinity is permitted during uninterrupted fatigue experiments. First results demonstrate the relevance of the method: the set-up is successfully used to measure the crystallinity distribution around a fatigue crack tip in a carbon black filled natural rubber for different loading conditions. [ABSTRACT FROM AUTHOR]

An in situ tensile-shear loading device has been designed to study elastomer crystallization using synchrotron X-ray scattering at the Synchrotron Soleil on the DiffAbs beamline. Elastomer tape specimens of thickness 2 mm can be elongated by up to 500% in the longitudinal direction and sheared by up to 200% in the transverse direction. The device is fully automated and plugged into the TANGO control system of the beamline allowing synchronization between acquisition and loading sequences. Experimental results revealing the evolution of crystallization peaks under load are presented for several tension/shear loading sequences. [ABSTRACT FROM AUTHOR]

Ni and Ni(W) solid solution of bulk Ni and Ni-W alloys (Ni-10W, Ni-30W, and Ni-50W) (wt%) were mechanically compared through the evolution of their {111} X-ray diffraction peaks during in situ tensile tests on the DiffAbs beamline at the Synchrotron SOLEIL. A significant difference in terms of strain heterogeneities and lattice strain evolution occurred as the plastic activity increased. Such differences are attributed to the number of brittle W clusters and the hardening due to the solid solution compared to the single-phase bulk Ni sample. [ABSTRACT FROM AUTHOR]

Catalytic chemical vapor deposition is the most promising process to obtain vertically aligned carbon nanotube (VACNT) carpets. Live analysis of growing VACNT is crucial to reveal their nucleation and growth mechanisms. We present novel time resolved in situ X-ray diffraction (XRD) analysis on growing macroscopic VACNT carpets enabling us to get statistical information on catalytic phase together with nanotube progressive alignment. A specific synthesis set-up has been developed to perform such in situ synchrotron XRD experiments. Nucleation kinetics of the different phases are evidenced: first, orthorhombic Fe 3 C crystalline phase is formed, followed by the formation of CNTs and finally of γ-Fe, demonstrating that Fe 3 C particles are the nucleation seeds for CNT growth. The additional formation of Fe 3 C or γ-Fe nanowires inside CNTs is associated with capillary forces and mobility of them at 850 °C. Experiments also reveal the progressive formation and alignment of VACNT carpets during the continuous precursor injection. Quantification of the alignment degree allows one to get a better understanding of the effect of precursor injection rate and CNT length on VACNT alignment. The overall results are key issues for the scaling-up of VACNT synthesis and their applications towards commercialization. [ABSTRACT FROM AUTHOR]

The thermal expansion of α-Fe (ferrite) and γ-Fe (austenite) nanocrystals confined inside multiwalled carbon nanotubes (MWCNTs) is studied in situ, using synchrotron x-ray diffraction, as a function of temperature. While the thermal expansion of ferrite is similar to that of bulk material, a peculiar behavior is evidenced for austenite: The thermal expansion becomes abnormally high above 500 °C. A scenario involving progressive carbon uptake in γ-Fe nanocrystals gives a satisfactory understanding of the phenomenon, and allows one to propose a value of the carbon solubilization rate in γ-Fe particles confined inside MWCNTs. [ABSTRACT FROM AUTHOR]

Abstract: Monotonic and cyclic loading of polycrystals causes a complex evolution of the dislocation structure and internal stresses. These phenomena were studied in sheet samples of commercially pure (CP) Ni in heat-treated (large-grained) states. Various microscopy tools were used, namely, scanning electron microscopy (SEM) with electron back-scattered diffraction (EBSD) to image the surface grain structure; Focused Ion Beam (FIB) with channelling contrast to visualise the through-thickness grain arrangement; and synchrotron scanning transmission X-ray microscopy (STXM) to obtain absorption-contrast images. In order to investigate the internal defects and lattice distortion caused by them, synchrotron X-ray diffraction was used in a variety of modes. Reciprocal space mapping (RSM) was used to quantify the amount of lattice re-orientation (rotation) due to plastic deformation. Micro-beam Laue diffraction was used to obtain 2D images containing multiple reflections that undergo “streaking” due to plastic deformation. The combination of reciprocal space mapping and Laue micro-diffraction provided improved insight into the deformation processes within individual grains during plastic deformation. The results are interpreted and discussed in conjunction with dislocation dynamics and finite element modelling of plastic deformation by crystal slip. [Copyright &y& Elsevier]

C60 fullerenes confined inside single-walled carbon nanotubes form an archetypal one-dimensional system. X-ray diffraction experiments, from room temperature to 1073 K, reveal an increasing melting phenomenon. Detailed analysis of the sawtooth peak characteristic of the fullerene organization allows the quantitative determination of fluctuations in intermolecular distances. The present results validate the predictions of one-dimensional statistical models. [ABSTRACT FROM AUTHOR]