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A combination of time-resolved synchrotron μ-X-ray diffraction computed tomography (μ-XRD-CT) and μ-pair distribution function computed tomography (μ-PDF-CT) has been applied for the study of an individual Co/γ-Al2O3 catalyst pellet during reduction and the early stages of the Fischer-Tropsch synthesis (FTS) reaction, revealing insight into the solid-state changes occurring from within such crystalline materials. Both sets of data were of sufficient quality so as to be able to follow the spatial dependency of Co speciation evolution from Co3O4 to CoO to face-centered cubic (fcc) Co metal nanoparticles. These data revealed the samples to be highly heterogeneous and contain two types of Co species: small (≤6.5 nm) nanoparticles that interact strongly with the γ-Al2O3 support which are difficult to reduce (remaining as CoO) and nanoparticles that agglomerate and have little interaction or else are weakly interacting with the support but readily reduce in H2. The Co phase evolution under FTS conditions shows a strong dependence on the Co nanoparticle location; the complementarity between the observations made using μ-XRD-CT vs μ-PDF-CT allowed us to conclude that at the sample periphery a significant amount of agglomerated, weakly interacting with the support, small fcc Co metal nanoparticles (≤7.5 nm) oxidize to CoO/Co3O4 during FTS, most likely due to the presence of water vapor produced during the reaction. Catalytic tests demonstrated that this oxidation coincided with a decrease in CH4 selectivity and increased water-gas shift (WGS) activity. This oxidation of fcc Co nanoparticles (i.e., the removal of the contribution to the XRD signal) also explains the observation of sintering previously reported for such catalysts in the early stages of the FTS reaction. (Chemical Equation Presented).

International audience; As the energy density of lithium-ion cells and batteries increases, controlling the outcomes of thermal runaway becomes more challenging. If the high rate of gas generation during thermal runaway is not adequately vented, commercial cell designs can rupture and explode, presenting serious safety concerns. Here, ultra-high-speed synchrotron X-ray imaging is used at >20 000 frames per second to characterize the venting processes of six different 18650 cell designs undergoing thermal runaway. For the first time, the mechanisms that lead to the most catastrophic type of cell failure, rupture, and explosion are identified and elucidated in detail. The practical application of the technique is highlighted by evaluating a novel 18650 cell design with a second vent at the base, which is shown to avoid the critical stages that lead to rupture. The insights yielded in this study shed new light on battery failure and are expected to guide the development of safer commercial cell designs

The use of mechanochemistry continues to grow due to its efficiency, selectivity and greener way in obtaining desired products. Inability to directly and in real- time monitor reaction progress of milling reactions, without the need to obstruct the milling process, was historically considered as a main drawback of mechanochemistry. This has been recently addressed by advanced synchrotron powder X-ray diffraction1 and laboratory Raman spectroscopy2 in situ monitoring methods which provided a direct insight into physical and chemical changes in reaction mixtures. Utilization of mechanochemistry in pharmaceutical industry is driven primarily by increasing need to create more sustainable drug manufacturing processes. Here we present mechanistic study of mechanochemical cocrystal synthesis of nicotinamide (vitamin B3) and L-ascorbic acid (vitamin C). Using ethanol and methanol as additives in milling 1:1 reaction mixture we have obtained two vitamin B3:C cocrystal polymorphs. Kinetically favored polymorph I is known from the literature3 and is in fact intermediate in the formation of previously unknown polymorph II which is thermodynamically more stable. We have successfully solved crystal structure of B3:C cocrystal polymorph II from synchrotron powder X- ray diffraction data. Both polymorphs remained in their respective solid forms even after 6 months of shelf life. Thermodynamic relationship of cocrystal polymorphs was determined by competitive slurry experiment which resulted in pure cocrystal polymorph II. Scaling up manufacturing process for both cocrystal polymorphs up to 10 grams and 100 grams has been achieved using planetary mill and twin screw extruder, respectively. Mechanochemically obtained cocrystal polymorphs exhibit excellent tableting properties compared to their reactants. This is important since L- ascorbic acid is famous for having poor compactible properties. Solution cocrystalization experiments resulted always in kinetically favored polymorph I, whereas the thermodynamically more stable polymorph II is available exclusively by mechanochemical milling. Acknowdlegements: Financial support from the Croatian Science Foundation (Grant No. UIP-2014-09-4744) is greatly appreciated.

Traditional organic synthesis methods have been developed to be very successful, but as natural resources are becoming more and more limited there is constant pursuit for developing more efficient and more eco-friendly synthetic procedures. Mechanochemical milling reactions emerged as a new “green” alternative to traditional solution synthesis, [1] and have been already reported for various organic reactions with clear benefits in the reaction rate and yields.[2] The Knoevenagel condensation is an important C–C bond forming reaction for synthesizing α, β-unsaturated structures from different aldehydes/ketones and carbon acid compounds. The general procedure for Knoevenagel reaction in solution include the presence of a weak base and higher temperatures of reaction mixture.[3] While the milling reactions provided higher yields and shorter reaction periods, [4] their mechanisms remain largely unknown, which limits their use and industrial applicability. Here we present simultaneous in situ synchrotron powder X-ray and Raman monitoring of mechanochemical synthesis of 5-aryliden barbiturates 5-8 by a condensation reaction between aromatic aldehyde 1-4 and barbituric acid carried out in a ball mill. In situ monitoring by these two complementary techniques enabled a direct insight both into the reactivity at molecular level and the evolution of crystalline phases during the milling reactions. Also, it revealed a cause of the inhibiting action of water in the reaction. These results highlight again the importance of in situ techniques for elucidating the mechanisms of organic milling reactions and provide a new entry for their understanding.

Use of mechanical energy in a solvent free environment is promising approach to an alternative preparation of pharmaceutically active compounds and medicinal mechanochemistry [1]. However, to have full control over chemical reaction outcome, it is necessary to understand the mechanistic nature that lies behind it. Recently developed in situ techniques for synchrotron X-ray diffraction and Raman spectroscopy [2] enabled unprecedented insight into the chemical reaction pathways and revealed highly dynamical systems. Different polymorphs occur as reaction intermediates and follow Ostwald’s rule of stages, wherein thermodynamically stable phase is formed from the sequence of metastable phases. Using very small amount of liquid additives as primary alcohols or water a sustainable control and selectivity can be achieved. We present here the co-crystallization of either benzoic acid (ba) or ascorbic acid (ac), also known as vitamin C, with the pharmaceutically active nicotinamide (na). ba and na form four polymorphs [3] while ac and na form two new solid phases. A reaction pathway depends on the reaction conditions, primarily on the amount, polarity and functionality of the added liquid. Using different amounts of liquids changes the reaction mechanism but also enables control of product formation leading to selectivity in this new solid-state synthesis approach. Future research will focus on elucidation of reaction mechanism of this important reactions and further understanding of selectivity based on liquid additives.

International audience; An X-ray diffraction computed tomography data-collection strategy that allows, post experiment, a choice between temporal and spatial resolution is reported. This strategy enables time-resolved studies on comparatively short timescales, or alternatively allows for improved spatial resolution if the system under study, or components within it, appear to be unchanging. The application of the method for studying an Mn-Na-W/SiO2 fixed-bed reactor in situ is demonstrated. Additionally, the opportunities to improve the data-collection strategy further, enabling post-collection tuning between statistical, temporal and spatial resolutions, are discussed. In principle, the interlaced scanning approach can also be applied to other pencil-beam tomographic techniques, like X-ray fluorescence computed tomography, X-ray absorption fine structure computed tomography, pair distribution function computed tomography and tomographic scanning transmission X-ray microscopy

International audience; Semiconducting indium sulfide (In2S3) has recently attracted considerable attention as a buffer material in the field of thin film photovoltaics. Compared with this growing interest, however, detailed characterizations of the crystal structure of this material are rather scarce and controversial. In order to close this gap, we have carried out a reinvestigation of the crystal structure of this material with an in situ X-ray diffraction study as a function of temperature using monochromatic synchrotron radiation. For the purpose of this study, high quality polycrystalline In2S3 material with nominally stoichiometric composition was synthesized at high temperatures. We found three modifications of In2S3 in the temperature range between 300 and 1300 K, with structural phase transitions at temperatures of 717 K and above 1049 K. By Rietveld refinement we extracted the crystal structure data and the temperature coefficients of the lattice constants for all three phases, including a high-temperature trigonal gamma-In2S3 modification