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Zinn ist der Top-Favorit für den Ersatz von giftigem Blei in Perowskit-Solarzellen. Allerdings kommt es dabei verstärkt zu der unerwünschten Oxidation von SnII zu SnIV. Die herkömmlichen Verfahren verwenden SnF2 in der Perowskit-Vorläuferlösung, um die Bildung von SnIV zu verhindern. Dennoch bleibt der Wirkmechanismus des Additivs unklar. Um diesen eingehender zu erläutern, untersuchen wir die Fluoridchemie in Zinn-Halogenid-Perowskiten mit einander ergänzenden Analyseverfahren. NMR-Spektroskopie der Vorläuferlösung offenbart eine stark bevorzugte Affinität der Fluoridanionen für SnIV gegenüber SnII, wodurch dieses selektiv als SnF4 komplexiert wird. Harte Röntgenphotoelektronenspektroskopie an Dünnschichten zeigt die geringere Bereitschaft von SnF4 gegenüber SnI4, in die Perowskit-Struktur eingebaut zu werden und verhindert somit den Einschluss von SnIV in der Dünnschicht. Abschließend offenbart Röntgen-Kleinwinkelstreuung den starken Einfluss vom Fluorid auf die kolloidale Chemie der Vorläuferlösungen, der sich direkt auf die darauffolgende Kristallisation auswirkt. European Research Council (ERC)

Halide perovskites are crystalline semiconductors gaining increasing attention as low-cost, high-performance materials for optoelectronics. Their processing from solution at low temperatures is compatible with rapid manufacturing of thin-film devices, including solar cells and light-emitting diodes. Therefore, understanding the coordination chemistry in metal halide perovskite precursor solutions would allow controlling the crystallization of thin films, their material properties and device performance. Here, we present a direct nanostructural technique to characterize the colloidal structure of perovskites in precursor solutions. Small-angle scattering is particularly adept for measuring nanoparticles in solution. Applying this technique to perovskite precursor solutions, we can study their colloidal properties. We show that not only do the colloids themselves matter, but also we can reveal their strong interactions in the early stages of crystallization. In particular, we focus on the prearrangement of particles into cluster-like formations. As an example, we present the concentration dependence, which is additionally supported using 207Pb NMR.

Crystallization of BaF2 from droplets of phase separated glass evidence of a core shell structure by ASAXS Armin Hoell, Vikram Singh Raghuwanshi, Christian Bocker, Andreas Herrmann, Christian Rüssel and Thomas Höche Glasses with the mol compositions 1.88 Na2O 15.04 K2O 7.52 Al2O3 69.56 SiO2 6.00 BaF2 and 1.88 Na2O 15.03 K2O 7.52 Al2O3 69.52 SiO2 6.00 BaF2 0.05 SmF3 were studied using X ray diffraction, transmission electron microscopy, and anomalous small angle X ray scattering ASAXS . While the glass doped with samarium showed liquid liquid phase separation of droplets with sizes of around 100 nm, the glass without samarium did not. The samples were annealed at 580 C or at 600 C which led to the crystallization of cubic BaF2. The X ray diffraction patterns showed strongly broadened lines. Hence, the BaF2 crystals possess sizes in the nm range. ASAXS gave evidence of a core shell structure. In agreement with earlier studies, it is assumed that the shell acts as a diffusion barrier that hinders crystal growth. Surprisingly, the cores and shells from the crystallization of the homogeneous glass and from the second glass, which is Sm doped and shows liquid liquid phase separation, both possess similar dimensions, even though the origin of the barrier is very different. The doped samples show long luminescence lifetimes of nearly 5 ms at a wavelength of 600 nm, which is nearly as long as those in fluoride phosphate glasses

Heterogeneous Cu catalysts are widely used in photocatalytic hydrogen generation. The typical working mode includes the transfer of photo-induced charges from a semiconductor to CuO which itself is reduced to Cu2O to initiate the catalytic cycle. In this contribution a photosensitizer (dye), excited by visible light absorption, was used to transfer an electron to the CuO which after reduction catalyzes the water reduction to hydrogen. Several copper(II)-catalysts on high surface silica were prepared by impregnation or precipitation and applied in photocatalytic water reduction. The best catalyst CuO(Cl0.1)/SiO2, synthesized via incipient wetness impregnation of CuCl2 in MCM-41 and a following precipitation with NaOH, achieved a 6 times higher activity (1702 mmol h−1 g−1) compared to a previously investigated copper system (280 mmol h−1 g−1 for CuI) under the same reaction conditions. All materials were fully characterized by XRD, TEM and N2 sorption and further by magnetic resonance and X-ray methods EPR, ASAXS and XAS. In situ measurements evidenced a reduction of the initial Cu(II)-species, which confirms the (proposed) photocatalytic mechanism.

Reversible solid-state hydrogen storage in metal hydrides is a key technology for pollution-free energy conversion systems. Herein, the LiBH2–MgH2 composite system with and without ScCl3 additive is investigated using synchrotron- and neutron-radiation-based probing methods that can be applied to characterize such lightweight metal–hydrogen systems from nanoscopic levels up to macroscopic scale. Combining the results of neutron- and photon-based methods allows a complementary insight into reaction paths and mechanisms, complex interactions between the hydride matrix and additive, hydrogen distribution, material transport, structural changes, and phase separation in the hydride matrix. The gained knowledge is of great importance for development and optimization of such novel metal-hydride-based hydrogen storage systems with respect to future applications.

The morphology and structural changes of confined matter are still far from being understood. This report deals with the development of a novel in situ method based on the combination of anomalous small-angle X-ray scattering (ASAXS) and X-ray absorption near edge structure (XANES) spectroscopy to directly probe the evolution of the xenon adsorbate phase in mesoporous silicon during gas adsorption at 165 K. The interface area and size evolution of the confined xenon phase were determined via ASAXS demonstrating that filling and emptying the pores follow two distinct mechanisms. The mass density of the confined xenon was found to decrease prior to pore emptying. XANES analyses showed that Xe exists in two different states when confined in mesopores. This combination of methods provides a smart new tool for the study of nanoconfined matter for catalysis, gas, and energy storage applications.

The nanostructure of hydrogenated amorphous silicon (a Si:H) is studied by a combination of small-angle X-ray (SAXS) and neutron scattering (SANS) with a spatial resolution of 0.8 nm. The a-Si:H materials were deposited using a range of widely varied conditions and are representative for this class of materials. We identify two different phases which are embedded in the a-Si:H matrix and quantified both according to their scattering cross-sections. First, 1.2 nm sized voids (multivacancies with more than 10 missing atoms) which form a superlattice with 1.6 nm void-to-void distance are detected. The voids are found in concentrations as high as 6*10^19 ccm in a-Si:H material that is deposited at a high rate. Second, dense ordered domains (DOD) that are depleted of hydrogen with 1 nm average diameter are found. The DOD tend to form 10-15 nm sized aggregates and are largely found in all a-Si:H materials considered here. These quantitative findings make it possible to understand the complex correlation between structure and electronic properties of a-Si:H and directly link them to the light-induced formation of defects. Finally, a structural model is derived, which verifies theoretical predictions about the nanostructure of a-Si:H., Comment: Letter presenting a model for a-Si:H derived by SAXS and SANS

Combining X ray Absorption Fine Spectroscopy XAFS with Anomalous Small Angle X ray Scattering ASAXS determines the location of Cu2 ions in silicoaluminophosphate SAPO 5 frameworks prepared by hydrothermal crystallization or impregnation. As expected, for the hydrothermally prepared sample, incorporation in the SAPO 5 framework was observed. For the first time preferential location of Cu2 ions at the inner and outer surfaces of the framework is determined. Temperature Programmed Reduction TPR and X ray Photoelectron Spectroscopy XPS investigations demonstrated that such Cu2 is stable in an argon Ar atmosphere up to 550 C and can only be reduced under a hydrogen atmosphere. In contrast, Cu2 deposited by impregnation on the pure SAPO 5 framework can be easily reduced to Cu in an Ar atmosphere. At lower Cu amounts, mononuclear tetrahedrally coordinated Cu species were formed which are relatively stable in the monovalent form. In contrast, at higher Cu amounts, CuO particles were found which change easily between the mono and bivalent species

Polyacrylamides of different molecular weight, charges and dosages allow to control the retention and distribution of nanoparticles (NPs) in composites, and optimise composite properties and functionality. Our aim is to evaluate the effect of high molecular weight (13 MDa) cationic polyacrylamide (CPAM) charge and dosage on SiO2 (74 nm) NP’s assembly in cellulose nanofibers composites. Engineered cellulose/SiO2 composites were investigated by SEM, SAXS and DLS. SEM images show the local area retention of NPs into the cellulose matrix. SAXS provides an average NPs distribution and inter-NPs distance over complete volume of composite. DLS gives the hydrodynamic radius of CPAM adsorbed onto SiO2 NPs in a suspension. SAXS analysis reveals a structure conformation made of spherical SiO2 NPs core of diameter 74 nm surrounded by a CPAM polyelectrolyte shell 2.5 nm thick. Surprisingly, CPAM induced assembly of SiO2 NPs with constant inter-nanoparticle distance, which is irrelevant of polymer charge density. However, NPs retention in the cellulose fibre network increases with CPAM dosage. The assembly mechanism is governed by the balance of electrostatic and steric forces following CPAM coverage onto NPs and the inter-nanoparticle CPAM bridging conformation. This maintains the constant inter-nanoparticle distance and the assembly of NPs in the cellulose network.

Understanding the influence of the support on the electrocatalytic behaviour of platinum is key to the development of novel Pt/oxide catalysts for the oxygen reduction reaction (ORR). For studies to isolate these effects, highly dispersed supported Pt nanoparticles with well-controlled particle sizes are required. In this study, we demonstrate a novel preparation process for Pt/oxide catalysts, with small Pt nanoparticles (2.5–3.5 nm), supported on a commercial Sb–SnO2 (ATO) nanopowder, with a very high utilization of the Pt-precursor. The organometallic chemical deposition method produces catalyst nanoparticles with a homogeneous distribution over the surface of the support even at high Pt metal loadings. Additionally, by using a mild hydrogen reduction treatment of the oxide support prior to Pt deposition, significantly smaller Pt nanoparticles were obtained with an outstanding mass-specific electrochemically active surface area exceeding 100 m2 g−1. Furthermore, by varying the Pt metal loading, several fundamental electrocatalytic effects that strongly influence the Pt/ATO system were distinguished. Good electrochemical stability during high-potential cycling was observed and was attributed to potential-dependent in situ conductivity switching of the ATO support. In turn, ORR activities of the Pt/ATO catalysts were found to be influenced by a combination of Pt particle size effects, ATO support in situ conductivity limitations at PEFC operation potentials, and electrocatalytic metal–support interactions. Therefore, in addition to demonstrating a powerful method for the preparation of exceptionally high surface area Pt/oxide catalysts, the present study contributes to the detailed understanding of the interplay between various phenomena that influence the electrocatalytic activity and stability of Pt/oxide systems for the ORR. Furthermore, the novel preparation approach for Pt/metal oxide catalysts could be of major interest for catalyst preparation in other fields of electrocatalysis and heterogeneous catalysis.

Polymer electrolyte fuel cells (PEFCs) offer an efficient way of chemical-to-electrical energy conversion that could drastically reduce the environmental footprint of the mobility and stationary energy supply sectors, respectively. However, PEFCs can suffer from severe degradation during start/stop events, when the cathode catalyst is transiently exposed to very high potentials. In an attempt to mitigate corrosion of conventional carbon support materials for Pt catalyst nanoparticles under these conditions, conductive metal oxides like antimony-doped tin oxide (ATO) are considered alternative support materials with improved corrosion resistance. A combined in situ anomalous small-angle X-ray scattering and post mortem transmission electron microscopy study reveals PEFC-relevant degradation properties of ATO-supported Pt in comparison to carbon-supported Pt catalysts. Against expectation, the superior stability of ATO-supported Pt nanoparticles cannot be merely explained by improved support corrosion resis...

Herein we report a novel study on the reaction mechanism of non aqueous aluminum graphite cell chemistry employing 1 ethyl 3 methylimidazolium chloride aluminum trichloride EMIMCl AlCl3 as the electrolyte. This work highlights new insights into the reversibility of the anion intercalation chemistry besides confirming its outstanding cycle life exceeding 2000 cycles, corresponding to more than 5 months of cycling test. The reaction mechanism, involving the intercalation of AlCl4 in graphite, has been fully characterized by means of ex situ X ray diffraction XRD , X ray photoelectron spectroscopy XPS , X ray absorption near edge structure spectroscopy XANES and small angle X ray scattering SAXS , evidencing the accumulation of anionic species into the cathode as the main factor responsible for the slight initial irreversibility of the electrochemical process

Aiming to improve the hydrogen storage properties of 2LiH + MgB2 (Li-RHC), the effect of TiO2 addition to Li-RHC is investigated. The presence of TiO2 leads to the in situ formation of core-shell LixTiO2 nanoparticles during milling and upon heating. These nanoparticles markedly enhance the hydrogen storage properties of Li-RHC. Throughout hydrogenation-dehydrogenation cycling at 400 °C a 1 mol% TiO2 doped Li-RHC material shows sustainable hydrogen capacity of ∼10 wt% and short hydrogenation and dehydrogenation times of just 25 and 50 minutes, respectively. The in situ formed core-shell LixTiO2 nanoparticles confer proper microstructural refinement to the Li-RHC, thus preventing the material's agglomeration upon cycling. An analysis of the kinetic mechanisms shows that the presence of the core-shell LixTiO2 nanoparticles accelerates the one-dimensional interface-controlled mechanism during hydrogenation owing to the high Li+ mobility through the LixTiO2 lattice. Upon dehydrogenation, the in situ formed core-shell LixTiO2 nanoparticles do not modify the dehydrogenation thermodynamic properties of the Li-RHC itself. A new approach by the combination of two kinetic models evidences that the activation energy of both MgH2 decomposition and MgB2 formation is reduced. These improvements are due to a novel catalytic mechanism via Li+ source/sink reversible reactions. Fil: Puszkiel, Julián Atilio. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Helmholtz–Zentrum Geesthacht; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Castro Riglos, Maria Victoria. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Mizrahi, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Karimi, F.. Helmholtz–Zentrum Geesthacht; Alemania Fil: Santoru, Antonio. Helmholtz–Zentrum Geesthacht; Alemania Fil: Hoell, Armin. Helmholtz-zentrum Berlin; Alemania Fil: Gennari, Fabiana Cristina. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Arneodo Larochette, Pierre Paul. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Pistidda, Claudio. Helmholtz–Zentrum Geesthacht; Alemania Fil: Klassen, Thomas. Helmut Schmidt University; Alemania Fil: Bellosta Von Colbe, J.M.. Helmholtz–Zentrum Geesthacht; Alemania Fil: Dornheim, M.. Helmholtz–Zentrum Geesthacht; Alemania

A polyether based thermoplastic polyurethane (TPU) containing 43 wt.% hard domains is aged in air at 150 °C for 15 and 36 days, respectively. Straining of the samples (0 d, 15 d, 36 d) is monitored by small-angle X-ray scattering (SAXS). Visual inspection of the chord distribution functions (CDFs) guides to a model for the fitting of the longitudinal projection of the fiber scattering. This model comprises two components: isolated hard domains (solos) and hard domains which are arranged with respect to a next neighbor (duos). Aging increases the average size of the hard domains (HD) (0 d:5, 15 d:8, 36 d:7 nm) and the average distance between them (0 d:3, 15 d:6, 36 d:9 nm). It decreases the volume fraction of HD considerably. The probable mechanism is selective degradation of the smaller hard domains. With increasing strain the relative loss of HD is the same for all samples. Aging softens the HDs. Softened HDs lengthen when the sample is stretched. They are destroyed before the rigid ones. HD-lengthening is identical for sample 15 d and 36 d. Only with the aged materials small strain causes HDs to migrate from the random to the arranged component – and back at higher strain. Sample 36 d breaks at strain 1.5, whereas sample 15 d resists. Here the soft-domain height doubles suddenly at strain 1.2. The indicated mechanism is disruption of each second HD.

The interaction between nano- or micro-sized particles and cell membranes is of crucial importance in many biological and biomedical applications such as drug and gene delivery to cells and tissues. During their cellular uptake, the particles can pass through cell membranes via passive endocytosis or by active penetration to reach a target cellular compartment or organelle. In this manuscript, we develop a simple model to describe the interaction of a self-driven spherical particle (moving through an effective constant active force) with a minimal membrane system, allowing for both penetration and trapping. We numerically calculate the state diagram of this system, the membrane shape, and its dynamics. In this context, we show that the active particle may either get trapped near the membrane or penetrates through it, where the membrane can either be permanently destroyed or recover its initial shape by self-healing. Additionally, we systematically derive a continuum description allowing to accurately predict most of our results analytically. This analytical theory helps identifying the generic aspects of our model, suggesting that most of its ingredients should apply to a broad range of membranes, from simple model systems composed of magnetic microparticles to lipid bilayers. Our results might be useful to predict mechanical properties of synthetic minimal membranes., Comment: 16 pages, 6 figures. Revised manuscript resubmitted to J. Chem. Phys

Herein we report on a detailed investigation of the irreversible capacity in the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl3) as electrolyte. The reaction mechanism, involving the intercalation of AlCl4 in graphite, has been fully characterized by correlating the micro/nanostructural modification to the electrochemical performance. To achieve this aim a combination of X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and computed tomography (CT) has been used. The reported results evidence that the irreversibility is caused by a very large decrease in the porosity, which consequently leads to microstructural changes resulting in the trapping of ions in the graphite. A powerful characterization methodology is established, which can also be applied more generally to carbon-based energy-related materials. Introduction

Solid-state hydride compounds are a promising option for efficient and safe hydrogen-storage systems. Lithium reactive hydride composite system 2LiBH4 + MgH2/2LiH + MgB2 (Li-RHC) has been widely investigated owing to its high theoretical hydrogen-storage capacity and low calculated reaction enthalpy (11.5 wt % H2 and 45.9 kJ/mol H2). In this paper, a thorough investigation into the effect of the formation of nano-TiAl alloys on the hydrogen-storage properties of Li-RHC is presented. The additive 3TiCl3·AlCl3 is used as the nanoparticle precursor. For the investigated temperatures and hydrogen pressures, the addition of ∼5 wt % 3TiCl3·AlCl3 leads to hydrogenation/dehydrogenation times of only 30 min and a reversible hydrogen-storage capacity of 9.5 wt %. The material containing 3TiCl3·AlCl3 possesses superior hydrogen-storage properties in terms of rates and a stable hydrogen capacity during several hydrogenation/dehydrogenation cycles. These enhancements are attributed to an in situ nanostructure and a hexagonal AlTi3 phase observed by high-resolution transmission electron microscopy. This phase acts in a 2-fold manner, first promoting the nucleation of MgB2 upon dehydrogenation and second suppressing the formation of Li2B12H12 upon hydrogenation/dehydrogenation cycling. Fil: Le, Thi-Thu. Helmholtz Zentrum Geesthacht; Alemania Fil: Pistidda, Claudio. Helmholtz Zentrum Geesthacht; Alemania Fil: Puszkiel, Julián Atilio. Helmholtz Zentrum Geesthacht; Alemania. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Castro Riglos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Helmholtz Zentrum Geesthacht; Alemania. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Karimi, Fahim. Helmholtz Zentrum Geesthacht; Alemania Fil: Skibsted, Jørgen. University Aarhus; Dinamarca Fil: Gharibdoust, Seyedhosein Payandeh. University Aarhus; Dinamarca Fil: Richter, Bo. University Aarhus; Dinamarca Fil: Emmler, Thomas. Helmholtz Zentrum Geesthacht; Alemania Fil: Milanese, Chiara. Università di Pavia; Italia Fil: Santoru, Antonio. Helmholtz Zentrum Geesthacht; Alemania Fil: Hoell, Armin. Helmholtz Zentrum Berlin für Materialien und Energie; Alemania Fil: Krumrey, Michael. Physikalisch Technische Bundesanstalt; Alemania Fil: Gericke, Eike. Universität zu Berlin; Alemania Fil: Akiba, Etsuo. Kyushu University; Japón Fil: Jensen, Torben R.. University Aarhus; Dinamarca Fil: Klassen, Thomas. Helmholtz Zentrum Geesthacht; Alemania. Helmut Schmidt University; Alemania Fil: Dornheim, Martin. Helmholtz Zentrum Geesthacht; Alemania

NaAlH 4 was melt infiltrated within a CO 2 activated carbon aerogel, which had been preloaded with TiCl 3 . Nanoconfinement was verified by Small Angle X-Ray Scattering (SAXS) and the nature of the Ti was investigated with Anomalous SAXS (ASAXS) and X-Ray Absorption Near Edge Structure (XANES) to determine its size and chemical state. The Ti is found to be in a similar state to that found in the bulk Ti-doped NaAlH 4 system where it exists as Al 1− x Ti x nanoalloys. Crystalline phases exist within the carbon aerogel pores, which are analysed by in-situ Powder X-Ray Diffraction (PXD) during hydrogen cycling. The in-situ data reveals that the hydrogen release from NaAlH 4 and its hydrogen uptake occurs through the Na 3 AlH 6 intermediate when confined at this size scale. The hydrogen capacity from the nanoconfined NaAlH 4 is found to initially be much higher in this CO 2 activated aerogel compared with previous studies into unactivated aerogels.

Machine-cast thermoplastic polyurethanes are strained and monitored by small-angle X-ray scattering (SAXS). They are prepared from 4,4′-methylene diphenyl diisocyanate, 1,4-butane diol, and polytetrahydrofuran. Upon stretching hard domains are destroyed. Most stable are the domains of materials with a hard-domain content (HSC) of 30%. Domain stability decreases with increasing HSC and crosslinking. Most materials show stability up to a strain 0.6. At higher strain, the apparent long period decreases for the materials with HSC = 30%. Correlated hard domains, the “strain probes” relax as others are destroyed. The fraction of relaxing probes and their ultimate relaxation decrease with increasing HSC. Chord distribution functions computed from the SAXS exhibit the same sequence of static long-period bands. The band positions form a Fibonacci series, related to the underlying polyaddition process. This indicates a nearly quasicrystalline arrangement of stringed hard domains, identified as the strain probes of the discrete SAXS. At strains

Macroscopic failure of polyurethane materials of 30 wt.-% hard-segment content is related to microstructure evolution mechanisms. Topology and functionality (f = 2 … 4) of the polyols are varied. Samples are strained and small-angle X-ray scattering (SAXS) patterns are recorded. Only material PU-I (f = 2) passes the tensile test. Material PU-Hs – a H-shaped (f = 4) polyol with short arms – is not nanostructured. PU-Hl has long arms. It contains few hard domains placed at random. PU-Hl survives longer (strain: 1.8) than the other short-lived materials. Its isolated hard domains are not destroyed during straining. PU-X (f = 4, star-shaped) develops microfibrils: one-dimensional (1D) correlations among hard domains, as deduced from a chord distribution function (CDF) analysis. PU-I and PU-Y are based on 2- and 3-functional polyols. They contain many well-separated hard domains with one-dimensional (3D) connectivity. Their arrangement of hard domains evolves identically, but not the population density. In PU-I (and PU-X) hard domains fail during straining, in PU-Y the interdomain soft phase density decreases.

The journal of physical chemistry / C 122(22), 11671 - 11681 (2018). doi:10.1021/acs.jpcc.8b02258, To enhance the dehydrogenation/rehydrogenation kinetic behavior of the LiBH$_4$–MgH$_2$ composite system, TiF$_4$ is used as an additive. The effect of this additive on the hydride composite system has been studied by means of laboratory and advanced synchrotron techniques. Investigations on the synthesis and mechanism upon hydrogen interaction show that the addition of TiF$_4$ to the LiBH$_4$–MgH$_2$ composite system during the milling procedure leads to the in situ formation of well-distributed nanosized TiB$_2$ particles. These TiB$_2$ nanoparticles act as nucleation agents for the formation of MgB$_2$ upon dehydrogenation process of the hydride composite system. The effect of TiB$_2$ nanoparticles is maintained upon cycling., Published by Soc., Washington, DC

Precipitation hardening involves solutionising, quenching and annealing steps, the latter often at various temperatures. The phenomena observed in Al-Mg-Si alloys are very complicated and partially not well understood. During and after quenching, solute atoms diffuse through the lattice assisted by vacancies and form atom clusters that gradually grow. These act back onto vacancies, which complicates the situation. We apply positron annihilation techniques in addition to traditional hardness, resistivity and thermal measurements to clarify what happens in various stages of thermal treatment: The quenching process can be divided into a stage of vacancy loss and of precipitation. Very short artificial ageing treatments after heating at different rates show that there is a competition between vacancy losses and cluster formation as the temperature increases. The difference between natural ageing and artificial ageing can be defined based on the importance of excess vacancies. Based on such results the behaviour of “invisible” objects such as vacancies and small clusters can be better understood but some open question remain such as the kinetics of secondary ageing or the details of the negative effect of natural ageing on artificial ageing.

The feature sizes of only a few nanometres in modern nanotechnology and next-generation microelectronics continually increase the demand for suitable nanometrology tools. Grazing-incidence small-angle X-ray scattering (GISAXS) is a versatile technique to measure lateral and vertical sizes in the nanometre range, but the traceability of the obtained parameters, which is a prerequisite for any metrological measurement, has not been demonstrated so far. In this work, the first traceable GISAXS measurements, demonstrated with a self-assembled block copolymer grating structure with a nominal pitch of 25 nm, are reported. The different uncertainty contributions to the obtained pitch value of 24.83 (9) nm are discussed individually. The main uncertainty contribution results from the sample–detector distance and the pixel size measurement, whereas the intrinsic asymmetry of the scattering features is of minor relevance for the investigated grating structure. The uncertainty analysis provides a basis for the evaluation of the uncertainty of GISAXS data in a more general context, for example in numerical data modeling.

In this work, we report the formation and growth mechanisms of gold nanoparticles (AuNPs) in eco-friendly deep eutectic solvents (DES; choline chloride and urea). AuNPs are synthesized on the DES surface via a low-energy sputter deposition method. Detailed small angle X-ray scattering (SAXS), UV-Vis, and cryogenic transmission electron microscopy (cryo-TEM) investigations show the formation of AuNPs of 5 nm diameter. Data analysis reveals that for a prolonged gold-sputtering time there is no change in the size of the particles. Only the concentration of AuNPs increases linearly in time. More surprisingly, the self-assembly of AuNPs into a first and second shell ordered system is observed directly by in situ SAXS for prolonged gold-sputtering times. The self-assembly mechanism is explained by the templating nature of DES combined with the equilibrium between specific physical interaction forces between the AuNPs. A disulfide-based stabilizer, bis((2-mercaptoethyl)trimethylammonium) disulfide dichloride, was applied to suppress the self-assembly. Moreover, the stabilizer even reverses the self-assembled or agglomerated AuNPs back to stable 5 nm individual particles as directly evidenced by UV-Vis. The template behavior of DES is compared to that of nontemplating solvent castor oil. Our results will also pave the way to understand and control the self-assembly of metallic and bimetallic nanoparticles.

We report on anomalous small-angle X-ray scattering (ASAXS) investigations of the formation and structure of nanosized ZrTiO4 crystals in lithium-alumino-silicate (LAS) glass during heat treatment at 750 °C for different periods of time. For a sample annealed for 30 min, ASAXS measurements near the X-ray absorption edge of Ti and Zr reveal the formation of particles (ZrTiO4) surrounded by a shell-like region. The sample annealed for 240 min shows the formation of two different types of particles (spherical core–shell: ZrTiO4 and large spherical particles: LiAlSi2O6). Additionally, ASAXS results allow quantitative determination of the average composition and volume fraction of the nanocrystals, the surrounding region (shell), and the remaining glass matrix. Data analysis reveals the formation of an alumina enriched region around ZrTiO4. This alumina enriched layer makes the glass network rigid and hinders further growth of ZrTiO4 nanoparticles. For a prolonged annealing time (240 min), a new phase (LiAlSi2...

Fe-Mn-O magnetic nanocrystals precipitate in a glass system SiO2/Na2O/Fe2O3/MnO during thermal annealing for different periods of time. We report here small angle neutron scattering investigations using polarized neutrons (pSANS) on these glass samples. Analysis of scattering data reveals the formation of spherical core-shell particles. The core of the particle is found to be magnetic and it is surrounded by a non-magnetic shell-like region. The size parameters of the nanocrystals calculated by pSANS data analyses are comparable with the small angle X-ray scattering (SAXS) investigations, previously reported. Contrary to other glasses in the studied system the diffusion of Fe and Mn ions is not impaired by a rigid shell. This is explained by decreasing of the glass transition temperature of the shell region while its composition departs from that of the matrix. (C) 2013 Elsevier B.V. All rights reserved. (Less)

The formation and growth of nanosized CaF2crystallites by heat treatment of an oxyfluoride glass of composition 7.65Na2O–7.69K2O–10.58CaO–12.5CaF2–5.77Al2O3–55.8SiO2(wt%) was investigated using anomalous small-angle X-ray scattering (ASAXS). A recently developed vacuum version of the hybrid pixel detector Pilatus 1M was used for the ASAXS measurements below the CaK-edge of 4038 eV down to 3800 eV. ASAXS investigation allows the determination of structural parameters such as size and size distribution of nanoparticles and characterizes the spatial distribution of the resonant element, Ca. The method reveals quantitatively that the growing CaF2crystallites are surrounded by a shell of lower electron density. This depletion shell of growing thickness hinders and finally limits the growth of CaF2crystallites. Moreover, in samples that were annealed for 10 h and more, additional very small heterogeneities (1.6 nm diameter) were found.

Self-assembly of gold nanoparticles was obtained by sputter deposition on DES. SAXS and TEM investigations reveal the formation of spherical nanoparticles with a mean diameter of 5 ± 0.5 nm. For extended sputtering times, the number density of AuNPs increases linearly and a very pronounced 1st and 2nd shell ordering is observed.

When exposed to corrosive anodic electrochemical environments, Pt alloy nanoparticles (NPs) undergo selective dissolution of the less noble component, resulting in catalytically active bimetallic Pt-rich core-shell structures. Structural evolution of PtNi6 and PtNi3 NP catalysts during their electrochemical activation and catalysis was studied by in situ anomalous small-angle X-ray scattering to obtain insight in element-specific particle size evolution and time-resolved insight in the intraparticle structure evolution. Ex situ high-energy X-ray diffraction coupled with pair distribution function analysis was employed to obtain detailed information on the atomic-scale ordering, particle phases, structural coherence lengths, and particle segregation. Our studies reveal a spontaneous electrochemically induced formation of PtNi particles of ordered Au3Cu-type alloy structures from disordered alloy phases (solid solutions) concomitant with surface Ni dissolution, which is coupled to spontaneous residual Ni metal segregation during the activation of PtNi6. Pt-enriched core-shell structures were not formed using the studied Ni-rich nanoparticle precursors. In contrast, disordered PtNi3 alloy nanoparticles lose Ni more rapidly, forming Pt-enriched core-shell structures with superior catalytic activity. Our X-ray scattering results are confirmed by STEM/EELS results on similar nanoparticles.

In this study, plasmonic Au and Au/Ag nanostructures in soda-lime-silicate glasses have been generated by means of ArF-excimer laser irradiation (193 nm) below the ablation threshold of the glass. For this purpose pure and silver/sodium ion-exchanged float glasses have been coated by gold and then irradiated by the laser. The formation of Au and Au/Ag nanoparticles could be verified by the surface plasmon resonances between 420 and 620 nm, which were obtained by optical spectroscopy. Both, pure Au and Ag particles as well as bimetallic Au/Ag nanoparticles, could be observed by means of small angle X-ray scattering experiments. These results demonstrate that such procedures enable the spaceselected generation of plasmonic nanostructures in glass surfaces by excimer laser irradiation.

Carbon-based latent heat storage systems represent a powerful class of thermal management materials that allow for the dissipation of heat produced during peak electronic output operation. The composite materials unite the good thermal conductivity of carbon, usually in the form of graphite, with the thermal characteristics of phase change materials (PCM). Applications are found in automotive systems, such as passive cooling of components in vehicles with internal combustion engines. It is also used in electric vehicles that require a suitable temperature management system, especially for the battery cells to prevent thermal runaway and maintain the required operation temperature of the cell packs [1]. Electronic components, such as those found in mobile devices or power electronics, can successfully be thermally regulated and protected against overheating by phase change composite materials. Other well-known applications are temperature control in buildings and the heating of water [1,2]. In many cases, the geometry of the desired temperature regulation components hamper their success in commercial applications. Here, a novel preparation method is presented that allows for the straightforward manufacturing of complex geometries followed by the infiltration with a phase change material working at the required temperature. The porosity as well as the operating temperature of the composite can be adjusted by tuning the process parameters and by a careful choice of employed raw materials.

The present work reports the structural analysis of magnetic nanocrystals of Fe- and Mn-containing phases formed during annealing of the glass 13.6Na2O–62.9SiO2–8.5MnO–15.0Fe2O3−x(mol%) at 823 K for different periods of time. X-ray diffraction investigation shows the formation of a mixture of MnFe2O4and Fe3O4phases. Furthermore, small-angle X-ray scattering and anomalous small-angle X-ray scattering (ASAXS) experiments were used to extract quantitative information about the structure of the formed nano-sized crystals, as well as their phase compositions, volume fractions and size distributions. ASAXS analysis reveals the formation of spherical core–shell particles with the size of the particles between 10 and 50 nm. The concentrations of iron atoms in the core are higher than those in the shell and in the remaining matrix. With increasing annealing time, the ratio of Mn to Fe increases in the nanoparticles and the crystalline phase moves toward the pure jacobsite phase. Evaluated compositions reveal the presence of SiO2in the shell. This shell acts as a diffusion barrier for the nanocrystal-forming ions, and the growth of the particles is kinetically constrained.

In this investigation, glasses from the system Na2O/MnO/SiO2/Fe2O3 are prepared using a conventional glass-melting technique. During annealing the glass, a nanocrystalline (Fe, Mn)-based spinel phase is precipitated. The phase composition and microstructure of the formed glass–ceramics are studied using X-ray diffraction and electron microscopy. Anomalous small-angle X-ray scattering experiment is used to gather information on the size, composition and element distribution for the precipitated (Fe, Mn)-based nanocrystals. The sizes of the formed spinel crystals, as determined by scanning electron microscopy and anomalous X-ray scattering, are in the range from 12 to 50 nm for annealing temperatures in the range from 550 to 700 °C. Annealing for a longer period of time at temperatures ≥600 °C results in the formation of a second crystalline phase, NaFe(SiO3)2 (aegirine). The ASAXS data show the formation of core–shell structure for the (Fe, Mn)-based crystals with core consisting mostly of iron oxide and a shell, depleted of Fe and Mn. The growth of the spinel crystals is assumed to be kinetically self-constrained.

Many materials used for energy conversion have a complex structure and chemical composition, knowledge of which is important for both understanding the function of materials and energy conversion systems and for their further development. Synchrotron radiation and neutrons can make an important contribution to understanding the function of such systems. Taking examples from the fields of fuel cells, gas separation membranes, batteries, solar cells, and catalysts, the use of radiography, tomography, diffraction, scattering, and absorption edge spectroscopy is demonstrated. The strength of such methods is the in situ characterization of processes and compositions, and so the focus is on these aspects.

A structural model of selenium-modified ruthenium nanoparticles was derived from anomalous small-angle X-ray scattering (ASAXS) and small-angle neutron scattering (SANS) experiments and further approved and supported by TEM, XRD, and extended X-ray adsorption fine-structure (EXAFS) analysis. Carbon-supported ruthenium nanoparticles modified with selenium (RuSex/C) have been suggested as highly active and Pt-free cathode catalysts for the oxygen reduction reaction in PEM fuel cells. However, so far no definite conclusion regarding the nature of the catalytically active surface could be drawn. ASAXS and SANS experiments now revealed that the surface of Se modified Ru nanoparticles after reductive catalyst activation at elevated temperatures is not completely covered by Se. The Se rather forms patches on the Ru surface while the rest of the surface is covered by oxygen. It could be demonstrated that the different scattering contributions of the carbon black carrier and various metallic constituents of the su...

Primary crystallization of Ni(P) particles in hypoeutectic Ni–P amorphous alloy is investigated. Small-angle scattering with polarized neutrons is used to find simultaneously the particle size distribution and the size dependence of the particle composition. The size distribution consists of a peak at particle radius of ∼1 nm and a tail spanning from ∼2 to 15 nm.The composition of the particles forming the peak decreases from ∼9 to ∼2 at% P while their radii increase from 0.8 to 2 nm. The particles in the tail of the size distribution (2–15 nm) have nearly constant P content in the range of 0–2 at%.

Alloyed ( Mn 1 - x Fe x ) Au 2 ribbons ( x = 0 –0.075) show a complex dependence of magnetization and magnetoresistivity on composition, magnetic field, and temperature. This is associated with the helimagnetism of MnAu 2 and the field-driven transition from helix to fan spin-structure. The threshold field H thr for this metamagnetic transition strongly depends on x. Neutron diffraction shows that the periodicity length of the helix increases with increasing iron contents x 0.075 . For x = 0.05 a transition from the helical ground-state to a collinear ferromagnetic structure takes place at 150 K; for x = 0.075 only a ferromagnetic order is found.

Microemulsions (MEs) are of special interest because a variety of reactants can be introduced into the nanometer-sized aqueous domains, leading to materials with controlled size and shape [1,2]. In the past few years, significant research has been conducted in the reverse ME-mediated synthesis of organic nanoparticles [3,4]. In this study, a w/o ME medium was employed for the synthesis of lidocaine by direct precipitation in w/o microemulsion systems: water/isopropylpalmitat/Tween80/Span80. The particle size as well as the location of nanoparticles in the ME droplet were characterized by means of dynamic light scattering (DLS) and small angle neutron scattering (SANS). It is observed that lidocaine precipitated in the aqueous cores because of its insolubility in water. Hydrodynamic radius and gyration radius of microemulsion droplets were estimated as ∼15 nm and ∼4.50 nm from DLS and SANS respectively. Furthermore, different size parameters obtained by DLS and SANS experiments were compared

Small angle scattering of polarised neutron (SANSPOL) is a powerful technique for the determination of magnetisation, density and compositional profiles of nanostructured particles. We present here some examples of the magnetic profile determination using the SANSPOL technique and we discuss in detail its advantage with respect to the conventional small angle neutron scattering approach.

We have performed small angle neutron scattering measurements with polarised and non-polarised neutrons on FeAg magnetic systems prepared by plasma sputtering deposition with the co-sputtering method. We have prepared various samples with an iron content ranging from 10% to 30% and for iron concentration up to 20% they display a superparamagnetic behaviour. Particular attention has been dedicated to these systems, in order to investigate the evolution of granular phase morphology with iron content. The data collected with polarised neutrons can be interpreted in terms of the presence of nanosized particles surrounded by non-magnetic regions. Our data also indicate that samples “magnetic” morphology is greatly affected by iron percentage while the compositional shows negligible modifications.

Iron nanoparticles obtained by the inert-gas condensation technique have been analysed by small-angle polarised neutron scattering. The use of polarised neutrons allows a more precise determination of the magnetic scattering length profile inside each particle giving information about the magnetic order. In iron nanoparticles surrounded by an oxide layer (core-shell structure), the magnetic scattering length profile indicates that the oxide layer is weakly magnetised. In the case of intermixing with copper nanoparticles, the nuclear contributions are well described by a bimodal size distribution.

Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na 2 O–62.9SiO 2 –8.5MnO–15.0Fe 2 O 3− x (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core–shell type of nanoparticles with mean sizes between 10 nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enriched in SiO 2 . SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a non-magnetic shell-like region.

According to the typical composition of cement powder, the cement clinker phase tricalcium silicate (C3S) is of high importance for the formation of the hydration products in cement paste. This presentation exemplarily discusses results of small angle neutron scattering (SANS) investigations to study the effect of different parameters on the microstructure of hydrating C3S. Here the samples were stored for a given time under various climatic conditions (CO2 content of the ambient air). On simulating a very high degree of carbonation (3.00 vol % in air), microstructural changes are most evident.

Metal oxides are gaining increasing interest in electrocatalysis research as alternative to commonly used high surface area carbon supports for electrocatalyst nanoparticles. On the one hand, metal oxide supports can offer improved corrosion resistance in electrocatalytic processes occurring at high electrode potentials where carbon supports suffer from severe oxidation. On the other hand, intrinsic catalytic properties of the supported catalyst nanoparticles can be influenced by interactions between catalyst and metal oxide support. Thus, metal oxides open a wide field for optimization of supported electrocatalysts similar to the situation in heterogeneous catalysis. However, in electrocatalysis applications, electronic conductivity of the support material is necessary, a requirement which is difficult to be met by metal oxides. Whereas few metal oxides possess intrinsic metallic conductivity, a wider selection of semiconducting materials is achieved by generating defects, such as dopant atoms or oxygen vacancies, inside the lattice of an intrinsically isolating metal oxide. Our research on semiconducting Sb-doped SnO2 (ATO) support for Pt nanoparticles in the context of oxygen reduction reaction (ORR) electrocatalysis revealed a fundamental descriptor for the choice of suitable metal oxide support materials [1]: Well-known from the theory of the semiconductor–electrolyte interface, the metal oxide flat-band potential separates the potential range where the oxide surface is enriched with mobile charge carriers from the potential range of charge carrier depletion leading to a drastically reduced support conductivity at certain electrode potentials. This potential-dependent in situ conductivity switching can be seen as direct electrochemical analog of a field-effect transistor. On the one hand, this electrochemical transistor effect can limit metal oxide support conductivity and, therefore, electrocatalyst performance if the conductivity switching potential, i.e. the metal oxide flat-band potential, overlaps with the potential range of application. On the other hand, as shown for Pt/ATO ORR catalyst, the electrochemical transistor switching of ATO conductivity has a highly beneficial effect on the stability of supported Pt nanoparticles by limiting electrochemical dissolution and Ostwald ripening at high electrode potentials. Therefore, the electrochemical transistor effect of metal oxide supports offers a way for the development of ORR catalysts combining high performance with strongly improved stability. Acknowledgement This work was supported by CCEM Switzerland and Umicore AG & Co KG within the project DuraCat. The authors thank the BESSY II synchrotron at Helmholtz-Zentrum Berlin, Germany, for providing beamtime at the 7T MPW SAXS beamline. References [1] T. Binninger, R. Mohamed, A. Patru, K. Waltar, E. Gericke, X. Tuaev, E. Fabbri, P. Levecque, A. Hoell, T.J. Schmidt, Chem. Mater. 29 (2017), 2831–2843.

We report the chemistry and photophysics of atomic gold and silver particles in inorganic glasses. By synchrotron irradiation of gold-doped soda-lime silicate glasses we could create and identify unambiguously the gold dimer as a stable and bright luminescing particle embedded in the glassy matrix. The gold dimer spectra coincide perfectly with rare gas matrix spectra of Au(2). The glass matrix is, however, stable for years, and is hence perfectly suited for various applications. If the irradiated gold-doped sample is annealed at 550 degrees C a bright green luminescence can be recognized. Intense 337 nm excitation induces a decrease of the green luminescence and the reappearance of the 753 nm Au(2) emission, indicating a strong interrelationship between both luminescence centers. Time-dependent density functional theory (TD-DFT) calculations indicate that the green luminescence can be assigned to noble metal dimers bound to silanolate centers. These complexes are recognized as the first stages in the further cluster growth process, which has been investigated with small-angle x-ray scattering (SAXS). In silver-doped glasses, Ag(0) atoms can be identified with electron paramagnetic resonance (EPR) spectroscopy after synchrotron activation. Annealing at 300 degrees C decreases the concentration of Ag(1), but induces an intense white light emission with 337 nm excitation. The white luminescence can be decomposed into bands that are attributed to small silver clusters such as Ag(2), Ag(3) and Ag(4), and an additional band matching the green emission of gold-doped glasses.

This paper reports on measurements made during the INTACC (INTeraction of Aerosol and Cold Clouds) experiment. Observations are shown from six wave cloud flights in the temperature range -12 °C to -40 °C. In nearly all cases ice nucleation does not occur until after droplets have formed. Parcel trajectories that experience temperatures below -35 °C are dominated by homogeneous nucleation, while parcel trajectories that stay above -35 °C are affected by heterogeneous nucleation. Ice particles appear to be nucleated after the parent droplets reach their largest size and coldest temperature at the wave peak. The most likely heterogeneous nucleation mechanisms are immersion and/or contact nucleation.