The paper presents detailed analyses of solidification experiments performed on a refined Al-20wt.%Cu alloy using the SFINX (Solidification Furnace with IN situ X-radiography) laboratory facility. Directional solidifications of a sheet-like sample were carried out in a horizontal configuration, with the main surface of the sample parallel to the ground. The sample was solidified for a wide range of cooling rates to obtain various grain structures, from columnar to elongated and equiaxed. The formation of the grain structure was observed in-situ and in real-time by X-radiography, which allows the dynamic of solidification phenomena to be thoroughly analyzed. Based on the radiographs, quantitative measurements were performed to

Gravity effects such as natural convection in the liquid phase and buoyancy forces acting on the solid phase have a strong influence on the grain structure and microstructure formation dynamics during the solidification of metal alloys. It is thus very useful to undertake experimental studies that will provide benchmark data for a deeper understanding of the role of such gravity effects. In this paper, we study the formation of the equiaxed grain structure during refined Al-20wt.%Cu solidification in a temperature gradient for three different configurations: horizontal, vertical upward and vertical downward solidification. The key grain characteristics, namely grain size, grain elongation and grain growth orientation, were determined for all experiments and a comparative study was performed to identify the dominant effects of gravity 2 for each case. The present study provides quantitative information on the impact of grain flotation and solute flows on the equiaxed microstructure characteristics by means of in situ laboratory X-radiography.

The semi-conductor Ge 1x Sn x exhibits interesting properties for optoelectronic applications. In particular, Ge 1x Sn x alloys with x  0.1 exhibit a direct band-gap, and integrated in complementary-metal-oxide-semiconductor (CMOS) technology, should allow the development of Si photonics. CMOS-compatible magnetron sputtering deposition was shown to produce monocrystalline Ge 1x Sn x films with good electrical properties at low cost. However, these layers were grown at low temperature (< 430 K) and contained less than 6% of Sn. In this work, Ge 1x Sn x thin films were elaborated at higher temperature (> 600 K) on Si(001) by magnetron sputtering in order to produce low-cost and CMOS-compatible relaxed pseudocoherent layers with x ≥ 0.1 exhibiting a better crystallinity. Ge 1x Sn x crystallization and Ge 1x Sn x crystal growth were investigated. Crystallization of an amorphous Ge 1x Sn x layer deposited on Si(001) or Ge(001) grown on Si(001) leads to the growth of polycrystalline films. Furthermore, the competition between Ge/Sn phase separation and Ge 1x Sn x growth prevents the formation of large-grain Sn-rich Ge 1x Sn x layers without the formation of -Sn islands on the layer surface, due to significant atomic redistribution kinetics at the crystallization temperature (T = 733 K for x = 0.17). However, the growth at T = 633 K of a highly-relaxed pseudo-coherent Ge 0.9 Sn 0.1 film with low impurity concentrations (< 2 × 10 19 at cm 3 ) and an electrical resistivity four orders of 2 magnitude smaller than undoped Ge is demonstrated. Consequently, magnetron sputtering appears as an interesting technique for the integration of optoelectronic and photonic devices based on Ge 1x Sn x layers in the CMOS technology.

In this work, in-situ studies of organic thin films under stretching are developed. A high efficiency PffBT4T-2OD π-conjugated polymer (PCE11) was coated directly on a stretchable substrate in order to examine the impact of tensile strains on the structural properties. For that purpose, in-situ grazing incidence X-ray diffraction (GIXD) coupled with optical microscopic observations have been carried out to measure the structural parameters of PCE11 and to probe the mechanical behavior of polymer chains under uniaxial tensile load. It is observed that in the range between 0 and 15%-20% of stretching, the polymer chains become more oriented. Meanwhile an increase of negative values of deformation i.e. compression of the polymer chains along the film normal was measured. Beyond this range of stretching, the polymer order declined and the stress was relaxed. This relaxation is explained by the increased number of cracks spreading over the entire film as observed by optical microscopy.

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On earth, gravity-related phenomena are unavoidable, such as thermo-solutal convection caused by density gradients in the melt and buoyancy when the liquid phase is denser than the solid phase. Such phenomena can drastically affect both the grain density and their morphology during equiaxed solidification processes. For these reasons, fundamental studies comparing the influence of solidification parameters with and without gravity effects are important to obtain benchmark data, which are useful to understand and then control the final structure of materials in industrial processes. In the present work, the impact of the solidification parameters on the dendritic grain structure formation and on the final grain size and shape was investigated in situ by using X-radiography for different growth orientations with respect to gravity. In a first step, experiments were carried out with various solidification parameters and with the furnace in horizontal position, with the main surface of the sample being perpendicular to gravity to limit gravity-related phenomena. In a second step, experiments were carried out with identical solidification parameters but with the furnace in a vertical position, and for two solidification directions (upward and downward). A comparative study between horizontal and vertical experiments was carried out. Phenomena related to gravity have been highlighted and their respective impact on the solidification front propagation was analysed.

In order to investigate interdiffusion in Mo/V multilayers, we present a method that combines both kinetic mean-field simulations and calculations of x-ray scattered intensity with disorder effects. Considering preliminary experimental data obtained on Mo(4nm)/V(2nm) multilayers, we show that the angular shift of spectra observed after annealing, should take place for both Fickian and asymmetric interdiffusion modes. In contrast, clear signatures of the interdiffusion modes are found from the simulation of the peak intensities. These results offer interesting perspectives for a full analysis of the interdiffusion in these systems.

X-ray scattering experiments on coherent CuNi multilayers are performed at various annealing temperatures. First, we show that the classical thermoelasticity theory can be applied in such nanosamples to link composition and strain fields at intermediate temperature. Second, when interdiffusion takes place at higher temperature, the satellite peaks measured at different annealing times indicate the presence of a layer-by-layer interdiffusion mode controlled by the asymmetry of the atomic mobilities in this system.