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Amilenus aurantiacus overwinter in diapause, a natural starvation period, in hypogean habitats. The structure of spherites in the midgut diverticula (MD) and Malpighian tubules (MT) has been studied comparatively by light microscopy and TEM to detect eventual differences in mineral consumption in the beginning and at the end of the starvation period in these organs (MD and MT) associated with digestive processes. The chemical composition of spherites was examined by combining energy-dispersive X-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS) and energy-filtered TEM (EFTEM). The structure of the spherites changed during overwintering in both organs. At the beginning of overwintering, the spherites were composed of densely packed concentric layers of electron-dense and electron-lucent material. In the middle and at the end of overwintering, the electron-lucent layers between the layers of material indicated the loss of some material. The chemical composition of the spherites changed only in the MD; at the beginning of overwintering, these contained Si, O, C and Fe, while later there was no more Fe. In contrast, spherites in the MT were composed of Si, O, C and Ca throughout overwintering. A less intensive exploitation of the MD spherites was probably due to complete cessation of digestive and other cell activity in this organ during the winter diapause; activity of the MT slowed, but continued removing the cell metabolites.

Nanoparticles with diameters in the range of a few nanometers, consisting of gold and vanadium oxide, are synthesized by sequential doping of cold helium droplets in a molecular beam apparatus and deposited on solid carbon substrates. After surface deposition, the samples are removed and various measurement techniques are applied to characterize the created particles: scanning transmission electron microscopy (STEM) at atomic resolution, temperature dependent STEM and TEM up to 650 °C, energy-dispersive X-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS). In previous experiments we have shown that pure V

A solar energy conversion system, an organic tandem solar cell, and an electrochemical energy storage system, an alkali metal-ion battery, were designed and implemented in an integrated hybrid phot...

Plasmonic Ag@ZnO core@shell nanoparticles are formed by synthesis inside helium droplets with subsequent deposition and controlled oxidation. The particle size and shape can be controlled from spherical sub-10 nm particles to larger elongated structures. An advantage of the method is the complete absence of solvents, precursors, and other chemical agents. The obtained particle morphology and elemental composition have been analyzed by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). The results reveal that the produced particles form a closed and homogeneous ZnO layer around a 2–3 nm Ag core with a uniform thickness of (1.33 ± 0.15) nm and (1.63 ± 0.31) nm for spherical and wire-like particles, respectively. The results are supported by ultraviolet photoelectron spectroscopy (UPS), which indicates a fully oxidized shell layer for the particles studied by STEM. The plasmonic properties of the produced spherical Ag@ZnO core@shell particles are investigated by two-photon photoelectron (2PPE) spectroscopy. Upon excitation of the localized surface plasmon resonance in Ag at around 3 eV, plasmonic enhancement leads to the liberation of electrons with high kinetic energy. This is observed for both Ag and Ag@ZnO particles, showing that even if a Ag cluster is covered by the ZnO layer, a plasmonic enhancement can be observed by photoelectron spectroscopy.

Whole sample microscopy mappings are of interest in many cases as they provide analytical information of phases varying in size by orders of magnitude and in composition across the sample. These benefits are amplified if more than one microscopic technique is used for the mappings. However, to take full advantage of correlative whole sample mappings, the data of each technique has to be carefully prepared, treated, correlated and evaluated. With this work, we want to present the key steps of our data treatment approach as well as the results on an exemplary sample, the Chelyabinsk meteorite. The most important step in our data treatment approach is to start by evaluating the spectral maps separately as far as possible (at-% quantification for EDS for example) and then generate pseudo spectral maps from this evaluation in the form of image stacks. This allows us to preserve the advantages of specialized software packages and standard work flows for every spectral mapping, whilst also unifying the data format and compressing the data sufficiently for correlation and the application of machine learning tools. We have performed whole sample mappings using SEM, EDS and Raman on a cross-section of a Chelyabinsk meteorite fragment, roughly 1.0 cm x 0.8 cm large. Combining these mappings into a single “super” spectral map, we were able to produce a uniquely detailed mapping of the composition of the meteorite fragment, as well as perform a quantitative analysis of the elemental composition of several crystallographic phases. The results of our compositional analysis; olivine (Fo72Fa28), pyroxene (≈ 97 % En80Fs20Wo0 and 3 % En56Fs6Wo38), feldspar (albite), troilite, FeNi (taenite and kamacite), merrillite, chromite and hydroxyapatite; agree qualitatively with other reports from literature.

Materials 14(14), 3849 (1-15) (2021). doi:10.3390/ma14143849, Precipitation hardened and tempered martensitic-ferritic steels (TMFSs) are used in many areas of our daily lives as tools, components in power generation industries, or in the oil and gas (O&G) industry for creep and corrosion resistance. In addition to the metallurgical and forging processes, the unique properties of the materials in service are determined by the quality heat treatment (HT). By performing a quenching and partitioning HT during an in situ high energy synchrotron radiation experiment in a dilatometer, the evolution of retained austenite, martensite laths, dislocations, and carbides was characterized in detail. Atomic-scale studies on a specimen with the same HT subjected to a laser scanning confocal microscope show how dislocations facilitate cloud formation around carbides. These clouds have a discrete build-up, and thermodynamic calculations and density functional theory explain their stability., Published by MDPI, Basel

In bulk-heterojunction solar cells, the device performance strongly depends on the donor and acceptor properties, the phase separation in the absorber layer, and the formation of a bicontinuous net...

The oxidation of Fe@Au core@shell clusters with sizes below 5 nm is studied via high resolution scanning transmission electron microscopy. The bimetallic nanoparticles are grown in superfluid helium droplets under fully inert conditions, avoiding any effect of solvents or template structures, and deposited on amorphous carbon. Oxidation resistivity is tested by exposure to oxygen at ambient conditions. The passivating effect of Au-shells is studied in detail and a critical Au shell thickness is determined which keeps the Fe core completely unharmed. Additionally, we present the first synthesis of Fe@Au@Fe-oxide onion-type structures.

High-resolution STEM-EELS provides information about the composition of crystalline materials at the atomic scale, though a reliable quantitative chemical analysis is often hampered by zone axis conditions, where neighbouring atomic column intensities contribute to the signal at the probe position. In this work, we present a procedure to determine the concentration of two elements within equivalent atomic columns from EELS elemental maps – in our case barium and lanthanum within the A-sites of Ba1.1La1.9Fe2O7, a second order Ruddlesden-Popper phase. We took advantage of the large changes in the elemental distribution from column to column and introduced a technique, which substitutes inelastic scattering cross sections during the quantification step by using parameters obtained from the actual experiment. We considered channelling / de-channelling effects via inelastic multislice simulations and were thereby able to count occupancies in each atomic column. The EELS quantification results were then used as prior information during the Rietveld refinement in XRD measurements in order to differentiate between barium and lanthanum.

9 pags., 5 figs., 3 tabs., The temperature-induced structural changes of Fe−, Co−, and Ni−Au core−shell nanoparticles with diameters around 5 nm are studied via atomically resolved transmission electron microscopy. We observe structural transitions from local toward global energy minima induced by elevated temperatures. The experimental observations are accompanied by a computational modeling of all core−shell particles with either centralized or decentralized core positions. The embedded atom model is employed and further supported by density functional theory calculations. We provide a detailed comparison of vacancy formation energies obtained for all materials involved in order to explain the variations in the restructuring processes which we observe in temperature-programmed TEM studies of the particles., This research has been supported by the Austrian Science Fund (FWF) under Grant No. P 29893-N36, the FWF and the Christian Doppler Research Association (CDG) under Grant No. PIR8-N34, the Horizon 2020 research program of the European Union under Grant No. 823717-ESTEEM3, and the Spanish Agencia Estatal de Investigacion (AEI) and the Fondo ́ Europeo de Desarrollo Regional (FEDER, UE) under Grant No. MAT2016-75354-P. The authors acknowledge the use of HPC resources provided by the ZID of Graz University of Technology and by the Vienna Scientific Cluster (VSC). Further support by NAWI Graz is gratefully acknowledged. The CESGA supercomputer center (Spain) is also acknowledged for having provided computational resources.

The electronic response of surface deposited nanoparticles to a few-cycle near infrared pump pulse is traced by attosecond XUV transient absorption spectroscopy.

In the present study, DIN 31CrMoV9 (1.8519) steel samples were initially treated by salt bath- (SNC), gas- (GNC) and plasma-nitrocarburising (PNC) and afterwards oxidised for increased corrosion protection. The thickness and hardness of the oxide and compound layer as well as the diffusion zone were measured. Surface topographies and microstructures were analysed with optical microscopy, laser scanning microscopy and scanning electron microscopy (SEM), while the detailed chemical compositions of the sample surfaces were determined with energy-dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Tribological tests for characterisation of wear and frictional behaviours of the treated samples were performed under unlubricated sliding conditions. Results show that, although different nitrocarburising processes yield very similar hardness profiles and compound layer thicknesses, their surface morphology and oxide layer properties can be significantly different. On SNC samples, the thickest oxide layers were formed, which had a different chemical composition than those formed on GNC and PNC samples. Furthermore, SNC samples provided the highest wear resistance and only on these samples, the oxide layers were not removed during tribological testing. It is thus possible that a correlation between the oxide properties and the favourable tribological behaviour of the SNC samples exists.

The influence of simultaneous Cr- and Si-poisoning on the oxygen exchange kinetics of La2NiO4+δ was studied at 800 °C in dry and humid O2/Ar atmospheres over a period of 4000 h by means of dc-conductivity relaxation measurements. Chemical and morphological changes of the La2NiO4+δ surface exposed to increasingly harsh ambient conditions were investigated using X-ray photoelectron spectroscopy (XPS) depth profiling, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDXS) and high-resolution scanning transmission electron microscopy with energy dispersive X-ray and electron energy loss spectroscopy (HR-STEM EDXS/EELS). In the presence of Cr/Si-sources and under dry conditions, La2NiO4+δ shows good stability for more than 1000 h. However, as soon as humidity is introduced into the system a strong decline of the oxygen exchange activity is observed. Post-test analyses reveal newly formed partially blocking Cr- and Si-rich secondary phases on the surface of La2NiO4+δ which impede the surface exchange of oxygen.

We present in situ transmission electron microscopy (TEM) studies of nanoscale Ni–Au core–shell particles on heatable TEM grids. The bimetallic clusters, grown fully inert within superfluid helium nanodroplets to avoid any template or solvent effects, are deposited on amorphous carbon and monitored through a heating cycle from room temperature to 400 °C and subsequent cooling. Diffusion processes, known to impair the catalytic activities of core–shell structures, are studied as a function of the temperature and quantified through fits of a temperature-dependent diffusion constant directly derived from the experiment. After cooling, spatially resolved energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy measurements prove the inversion of the core–shell structure from Ni–Au to Au–Ni. Furthermore, a strong oxidation of the now exposed Ni shell is observed in the latter case. In combination with theoretical studies employing density functional theory, we analyze the influence of oxygen ...

The results of a study aimed at investigating the presence of silver in the strengthening phases of age-hardenable AlCuMgSi alloys are presented. HR STEM observations were performed on Al-4Cu-0.55Mg-0.5Si--0.15Zr-0.1Ti-0.5Ag (wt%) alloy samples aged or crept at 200 °C to monitor the evolution of secondary phases over long times. Results showed that in the peak aged condition silver mostly segregated at the surface of some strengthening precipitates types. This occurred specifically at the particle/matrix interface of θ' phase while particles, matching the wide compositional range of the quaternary Q' phase were free from Ag. A third population of strengthening particles having the shape of a core-shell rod was also observed. They were characterized by a Mg- and Si-rich core and a Cu- and Ag-rich shell. The exposure at 200 °C for up to 570 h, caused an evident coarsening of Q' and θ' plate-like particles, and the Ag surface enrichment of the latter went progressively lost. On the contrary, silver concentrated inhomogeneously on the surface of the core-shell particles for which a relatively low coarsening rate was observed.

We present time-resolved transmission electron microscopy studies of the degradation of Au, Ag, Cu and Ni nanowires deposited on a heated support. The wires are grown under fully inert conditions in superfluid helium droplets and deposited onto amorphous carbon. The inherent stability of these pristine metal nanowires with diameters below 10 nm is investigated in the absence of any stabilizers, templates or solvents. The phenomenon of Rayleigh-breakup, a consequence of diffusion processes along the wire surfaces, is analysed in situ via scans over time and support temperature. Our experimental efforts are combined with simulations based on a novel model featuring a cellular automaton to emulate surface diffusion. Based on this model, correlations between the material parameters and actual breakup behaviour are studied.

The long-term stability of the mixed-conducting perovskite oxide La 0.6 Sr 0.4 CoO 3-δ (LSC) was investigated for 3400 h at 800 °C. The oxygen exchange kinetics of LSC was studied in-situ in dry and humidified atmospheres in the absence as well as the presence of Cr and Si sources. The chemical surface exchange coefficient (k chem ) and the chemical diffusion coefficient (D chem ) of oxygen were measured by the dc-conductivity relaxation method. Degraded samples were analyzed by scanning electron microscopy (SEM) with energy and wavelength dispersive X-ray spectroscopy (EDXS/WDXS), X-ray photoelectron spectroscopy (XPS), and analytical scanning transmission electron microscopy (STEM). In dry atmosphere with 10% O 2 high values of k chem = 1 × 10 − 3 cm s − 1 and D chem = 2 × 10 − 5 cm 2 s − 1 were found. A stable performance was observed during 1300 h without or with the presence of Cr- and Si-impurities. However, a significant decrease in k chem and D chem occurred when the atmosphere was humidified (30–60% relative humidity). XPS depth profiles showed Sr-enrichment and Co-depletion of the surface already during 1300 h in dry atmosphere. After the treatment in humidified atmospheres for additional 2100 h significant amounts of Cr and Si contaminations were found. SEM and STEM showed crystallites of SrCrO 4 and La-silicate on the surface. SrCrO 4 and Co 3 O 4 were also found at the grain boundaries in the near-surface region. It can be concluded that the observed decrease in the oxygen exchange kinetics is closely related to significant changes of the surface composition as a result of Cr and Si poisoning which leads to the decomposition of the oxygen exchange-active LSC phase into inactive secondary phases.

Vanadium oxide clusters with a mean diameter below 10 nm are investigated by high resolution Scanning Transmission Electron Microscopy (STEM), Electron Energy Loss Spectroscopy (EELS) and UV-vis absorption spectroscopy. The clusters are synthesised by sublimation from bulk vanadium(v) oxide, in combination with a pick-up by superfluid helium droplets. The latter act as reaction chambers which enable cluster growth under fully inert and solvent-free conditions. High-resolution STEM images of deposited vanadium oxide particles allowing for the determination of lattice constants, clearly indicate a dominating presence of V

7 pags., 6 figs.-- ACS Liveslides presentation: https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.9b05765, Structural changes of Ni-Au core shell nanoparticles with increasing temperature are studied at atomic resolution. The bimetallic clusters, synthesized in superfluid helium droplets, show a centralized Ni core, which is an intrinsic feature of the growth process inside helium. After deposition on SiNx, the nanoparticles undergo a programmed temperature treatment in vacuum combined with an in situ transmission electron microscopy study of structural changes. We observe not only full alloying far below the actual melting temperature, but also a significantly higher stability of core-shell structures with decentralized Ni cores. Explanations are provided by large-scale molecular dynamics simulations on model structures consisting of up to 3000 metal atoms. Two entirely different diffusion processes can be identified for both types of core-shell structures, strikingly illustrating how localized, atomic features can still dictate the overall behavior of a nanometer-sized particle., This research has been supported by the Austrian Science Fund (FWF) under grant P 29893-N36 and FWF PIR8-N34, the Spanish Agencia Estatal de Investigacion (AEI) and the Fondo Europeo de Desarrollo ́ Regional (FEDER, UE) under grant no. MAT2016-75354-P, and by the COST Action CM1405 “Molecules in Motion” (MOLIM). The authors would like to acknowledge the use of HPC resources provided by the ZID of Graz University of Technology and by the Vienna Scientific Cluster (VSC). The CESGA super-computer center (Spain) is also acknowledged for having provided computational resources. Further support by NAWI Graz is gratefully acknowledged.

The growth of the poly-Si films was studied by Transmission Electron Microscopy (TEM) after Ni Metal Induced Lateral Crystallization (Ni-MILC) of amorphous Si films at 413 °C. Significant differences in the morphology and the mode of growth of the films were observed, in comparison to films grown at temperatures above 500 °C. It was shown that at 413 °C the Solid Phase Crystallization (SPC), which acts in parallel with the Ni-MILC process at temperatures above 500 °C is suppressed. The suppression of SPC results in substantial change in the mode of growth. The poly-Si film grown at 413 °C consists of whiskers, which can be classified into two categories. Those growing fast along the direction, which were already observed in conventional Ni-MILC above 500 °C and whiskers grown along random crystallographic orientations having significantly slower growth rates. Because of the large difference in growth rates of the whiskers, significant orientation filtering due to growth-velocity competition is observed. The uniform poly-Si films consist of a mixture of fast type whiskers and slow ones, grown in other orientations, resulting in a tweed-like structure.

Long-term stability tests are performed at 800 °C on Pr2NiO4+δ air electrodes by use of a symmetrical button cell with Ce0.9Gd0.1O1.95 as solid electrolyte. The experiments are carried out by means of electrochemical impedance spectroscopy and current-voltage measurements with and without current load under dry and humid conditions in the presence of a chromium source. Chromium poisoning of Pr2NiO4+δ air electrodes is investigated for periods of several hundred hours at 30% relative humidity. In order to separate the influence of anodic and cathodic electrode polarization on Cr-deposition, measurements are conducted using a Pt-reference electrode. The electrode performance is found to remain fairly stable under dry conditions, even when a current is drawn. However, after volatile Cr-species in a humid atmosphere are introduced, the cell performance starts to deteriorate and the polarization resistance contribution of the SOFC cathode increases significantly. After several thousand hours, the electrodes are analyzed by means of analytical electron microscopy. Detailed post-test analyses provide evidence for a correlation between the extent of Cr-deposition and electrode degradation in SOFC as well as SOEC mode. Based on these findings, enhanced resilience of Pr2NiO4+δ against Cr-poisoning in SOEC mode can be established.

Effects of trace elements (0.2Y and 0.2Ca (wt%) on the eutectic Ge in high purity Al–20Ge (wt%) alloys were investigated by multi-scale microstructure characterization techniques. Particularly, the distribution of trace elements (Y and Ca) within the eutectic Ge and/or at the interface between eutectic Ge and eutectic Al was investigated by atomic resolution high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imaging and atom probe tomography (APT). The combined investigations indicate Al–Y and Al–Ca co-segregations. Such co-segregations change significant morphology and growth of the eutectic Ge. In addition, large Al2Ge2Y and Al2Ge2Ca phases were also measured. The modification of eutectic Ge is discussed in terms of previously postulated modification mechanisms: twin plane re-entrant edge growth mechanism, impurity-induced twinning, and growth restriction of eutectic Ge.

Chromium- and silicon-poisoned samples of the intermediate temperature solid oxide fuel cell (IT-SOFC) cathode materials La 0.6 Sr 0.4 CoO 3-δ (LSC) and La 2 NiO 4 + δ (LNO) were investigated by transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), convergent beam electron diffraction (CBED), as well as by atomic force microscopy (AFM). Analytical TEM revealed phase decomposition of the original, oxygen exchange-active materials LSC and LNO, and the formation of secondary phases after 3500 h of testing at 700 °C. In the case of LSC, the phases SrCrO 4 , Co 3 O 4 , and CoCr 2-x Co x O 4 as well as a La‐chromate phase with unknown stoichiometry were found in the near-surface region and at the grain boundaries. Transport of cations, especially Sr and Cr, along the grain boundaries seems to play a key role in the degradation of LSC. AFM was used to determine the three-dimensional shape including interplanar facet angles of SrCrO 4 crystallites. In the case of the Sr-free material LNO, the formation of La‐silicate and La-Ni‐chromate phases was observed, which seems to proceed from the surface toward the bulk. Based on the experimental results, tentative mechanisms for the degradation processes are suggested.

The impact of silicon on the long-term stability of the intermediate temperature solid oxide fuel cell cathode material La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) was investigated during 2400 h at 700 °C. The area-specific resistance (ASR) of symmetric cells of LSCF on Gd 0.1 Ce 0.9 O 1.95-δ (GDC) was determined by electrochemical impedance spectroscopy (EIS) in ambient air without and with Si contamination of the electrodes. The ASR of the fresh LSCF electrode was 0.3 Ω cm 2 . During 1060 h without Si contamination, an increase in the cathode ASR by a factor of 4.5 was observed, which may be attributed to a decrease in the surface oxygen exchange coefficient of LSCF due to changes in the surface elemental composition. Subsequently, 10 nm thick silicon layers were sputtered onto the LSCF electrodes. This contamination resulted in a strong increase in the ASR by a factor of 5.9 during additional 1340 h at 700 °C. Post-test analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the degradation of the cathode is caused by the phase decomposition of LSCF within an approximately 50 nm thick surface region. A continuous La-Sr-silicate layer is formed in addition to isolated (Co,Fe) x O y nanoparticles. In agreement with the changes in the shape of the impedance spectra, it is assumed that this impurity layer leads to limitations in the gas diffusion towards the electrode and/or oxygen adsorption on the surface of the electrode.

High-order harmonic generation (HHG) based transient extreme ultraviolet (XUV) absorption spectroscopy is an emerging technique to trace photoinduced charge carrier dynamics in condensed phase materials with femtosecond and even attosecond temporal resolution and elemental specificity. However, its application to nanoparticulate samples that are relevant, for example, for novel photocatalytic light harvesting concepts, has been limited. This is in part due to the challenge to produce residual-free samples on ultrathin, XUV-transparent substrates as well as a widespread understanding that sparsely distributed nanoparticles do not provide sufficient contrast for XUV absorption measurements. Here, we present static XUV absorption spectra of partially oxidized Co nanowire-structures with diameters of approximately 4.5 nm and lengths between 10 and 40 nm, recorded with an ultrashort pulse HHG light source. Nanoparticles are synthesized by the agglomeration of Co atoms inside superfluid helium droplets, followed by surface deposition and oxidation in ambient air. The method is uniquely suited for residual-free synthesis of transition metal nanowires and their deposition on ultrathin substrates. Analysis by high-resolution transmission electron microscopy reveals the formation of CoO nanowires with regions of unoxidized Co in their interior. The nanoparticle samples are investigated in an HHG-driven ultrafast XUV absorption setup. Despite the low surface coverage of only 23%, the recorded spectrum exhibits a distinct absorption feature at the Co M2,3(2p) edge near 60 eV with a peak height of about 40 mOD. The results support the feasibility of table-top ultrafast transient XUV absorption studies of photoinduced dynamics in transition metal oxide nanoparticles with sub-monolayer surface coverage.

This work is aimed at characterizing the changes induced in the microstructure of an Al-7Si-0.4Mg (A356) alloy when 0.3 wt% Er (alloy E3) and 0.3 wt% Er plus approximately 0.5 wt% Zr (alloy EZ35) are added. The addition of Er and Zr caused the precipitation of Al3Er and Al3(Er, Zr) precipitates during solution heat treatment, as it was shown by isothermal DSC tests performed at the solution treatment temperature, microhardness measurements on samples subjected to different solution treatment time and STEM micrographs. The age hardening response of Er- and Zr-containing A356 is improved, thanks to the formation of further Al3Er and Al3(Er, Zr) precipitates during aging. Er- and Zr-containing precipitates were also identified inside eutectic Si and were identified as Al2Si2Er and Al2Si2(Er, Zr) for E3 and EZ35, respectively. Finally, an Er-rich layer was identified at the interface between eutectic Si and Al after thermal treatment, possibly formed by Er atoms diffusing along the Si twins and accumulating at the eutectic Si interface with the Al matrix.

Alloying processes in nanometre-size Ag@Au and Au@Ag core@shell particles are studied via high resolution Transmission Electron Microscopy (TEM) imaging., Alloying processes in nanometre-sized Ag@Au and Au@Ag core@shell particles with average radii of 2 nm are studied via high resolution Transmission Electron Microscopy (TEM) imaging on in situ heatable carbon substrates. The bimetallic clusters are synthesized in small droplets of superfluid helium under fully inert conditions. After deposition, they are monitored during a heating cycle to 600 K and subsequent cooling. The core–shell structure, a sharply defined feature of the TEM High-Angle Annular Dark-Field images taken at room temperature, begins to blur with increasing temperature and transforms into a fully mixed alloy around 573 K. This transition is studied at atomic resolution, giving insights into the alloying process with unprecedented precision. A new image-processing method is presented, which allows a measurement of the temperature-dependent diffusion constant at the nanoscale. The first quantification of this property for a bimetallic structure

International audience; In Accumulated Low Schottky Barrier metal oxide semiconductor field effect transistors (MOSFET) on SOl structures, very thin silicide layers are used for ohmic contacts. Silicide contacts form due to metallurgical reaction of metal with semiconductor. In order to get a broad vision of the most interesting metal/silicide solution several material stacks were evaluated including platinum and iridium. In this work cross-sectional transmission electron microscopy was used to study the process of silicide formation in metal/Si and metal/SiGe/Si structures. Novel structure architectures have been developed. They are mainly based on the use of a very thin film SOl substrate with typical active silicon layer thicknesses ranging between 2 and 20 nm for 10-40 nm gate length MOSFETs. In Accumulation LowSchottky Barrier -SOI MOSFET structures very thin silicides are used for ohmic contacts. Silicide contacts form due to metallurgical reaction of metal with semiconductor.

We present a computational scheme to simulate beam induced dynamics of atoms in surface dominated, metallic systems. Our approach is based on molecular dynamics and Monte Carlo techniques. The model is tested with clusters comprised of either Ni, Ag or Au. We vary their sizes and apply different electron energies and cluster temperatures to elucidate fundamental relations between these experimental parameters and beam induced displacement probabilities. Furthermore, we demonstrate the capability of our code to simulate beam driven dynamics by using Ag and Au clusters as demonstration systems. Simulations of beam induced displacement and sputtering effects are compared with experimental results obtained via scanning transmission electron microscopy. The clusters in question are synthesised with exceptional purity inside inert superfluid He droplets and deposited on amorphous carbon supports. The presented results may help to understand electron beam driven processes in metallic systems.

Surface dynamics lie at the heart of many areas of materials and chemical science, including heterogeneous catalysis, epitaxial growth, and device fabrication. Characterizing the dynamics of surface adsorption, reactions, and diffusion at the atomic scale is crucial to understanding and controlling such processes. Here, we use aberration-corrected scanning transmission electron microscopy to analyze the diffusive behavior of Pt atoms adsorbed on the Si(110) surface and characterize the effects of the electron beam on adatom motion, including a bias introduced by the raster scan of the probe. We further observe the evolution of the Si(110) surface, revealing evidence of developing surface steps attributed to the 16 × 2 surface reconstruction. These results demonstrate a framework for studying complex atomic-scale surface dynamics using aberration-corrected electron microscopy.

Objective Cryopyrin-associated periodic syndrome (CAPS) is a heterogeneous group of diseases characterized by excessive IL-1β release resulting in severe systemic and organ inflammation. Canakinumab targets IL-1β and is approved at standard dose for children and adults with all CAPS phenotypes. Limited data are available for the real-life effectiveness of canakinumab in patients living with CAPS. Therefore the aim of the study was to evaluate the real-life dosing and effectiveness of canakinumab in CAPS. Methods A multi-centre study of consecutive children and adults with CAPS treated with canakinumab was performed. Demographics, CAPS phenotype and disease activity, inflammatory markers and canakinumab treatment strategy were recorded. Treatment response was assessed using CAPS disease activity scores, CRP and/or serum amyloid A levels. Comparisons between age groups, CAPS phenotypes and centres were conducted. Results A total of 68 CAPS patients at nine centres were included. All CAPS phenotypes were represented. Thirty-seven (54%) patients were females, the median age was 25 years and 27 (40%) were children, and the median follow-up was 28 months. Overall, complete response (CR) was seen in 72% of CAPS patients, significantly less often in severe (14%) than in mild CAPS phenotypes (79%). Only 53% attained CR on standard dose canakinumab. Dose increase was more commonly required in children (56%) than in adults (22%). Centres with a treat-to-target approach had significantly higher CR rates (94 vs 50%). Conclusion Real-life effectiveness of canakinumab in CAPS was significantly lower than in controlled trials. Treat-to-target strategies may improve the outcome of children and adults living with CAPS.

In environmental scanning electron microscopy applications in the kPa regime are of increasing interest for the investigation of wet and biological samples, because neither sample preparation nor extensive cooling are necessary. Unfortunately, the applications are limited by poor image quality. In this work the image quality at high pressures of a FEI Quanta 600 (field emission gun) and a FEI Quanta 200 (thermionic gun) is greatly improved by optimizing the pressure limiting system and the secondary electron (SE) detection system. The scattering of the primary electron beam strongly increases with pressure and thus the image quality vanishes. The key to high-image quality at high pressures is to reduce scattering as far as possible while maintaining ideal operation conditions for the SE-detector. The amount of scattering is reduced by reducing both the additional stagnation gas thickness (aSGT) and the environmental distance (ED). A new aperture holder is presented that significantly reduces the aSGT while maintaining the same field-of-view (FOV) as the original design. With this aperture holder it is also possible to make the aSGT even smaller at the expense of a smaller FOV. A new blade-shaped SE-detector is presented yielding better image quality than usual flat SE-detectors. The electrode of the new SE detector is positioned on the sample table, which allows the SE-detector to operate at ideal conditions regardless of pressure and ED.

Summary In environmental scanning electron microscopy (ESEM) high pressure applications have become increasingly important. Wet or biological samples can be investigated without time-consuming sample preparation and potential artefacts from this preparation can be neglected. Unfortunately, the signal-to-noise ratio strongly decreases with increasing chamber pressure. To evaluate the high pressure performance of ESEM and to compare different electron microscopes, information about spatial resolution and detector type is not enough. On the one hand, the scattering of the primary electron beam increases, which vanishes the contrast in images; and on the other hand, the secondary electrons (SE) signal amplification decreases. The stagnation gas thickness (effective distance the beam has to travel through the imaging gas) as well as the SE detection system depend on the microscope and for a complete and serious evaluation of an ESEM or low vacuum SEM it is necessary to specify these two parameters. A method is presented to determine the fraction of scattered and unscattered electrons and to calculate the stagnation gas thickness (θ). To evaluate the high pressure performance of the SE detection system, a method is presented that allows for an analysis of a single image and the calculation of the signal-to-noise ratio of this image. All investigations are performed on an FEI ESEM Quanta 600 (field emission gun) and an FEI ESEM Quanta 200 (thermionic gun). These methods and measurements should represent opportunities for evaluating the high pressure performance of an ESEM. Lay description An Environmental Scanning Electron Microscope (ESEM), in comparison to a conventional SEM, enables the opportunity to investigate insulating, biological and even wet samples without additional sample preparation. The imaging gas inside the specimen chamber is responsible for the signal amplification by impact ionization and the degassing of biological or wet samples is prevented by the higher chamber pressure. Unfortunately, the signal to noise ratio strongly decreases with increasing chamber pressure, a fact which leads to noisy not interpretable images at very high pressures. The high pressure capabilities of modern ESEMs strongly depend on the design of the electron detection system and the electron beam transfer through the imaging gas. To evaluate the high pressure performance of ESEMs and to compare different electron microscopes, information about spatial resolution and detector types are not enough. In this paper methods are presented to quantify the high pressure performance which helps manufactures as well as scientists who want to improve their microscopes to evaluate the different designs.

Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al{sub 3}(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al{sub 3}(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al{sub 3}(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al{sub 3}(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al{sub 3}(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al{sub 3}(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al{sub 3}(Sc,Zr) particle enhances the heterogeneous nucleation of Al{sub 3}(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al{sub 3}(Sc,Zr) phases were observed within the α-Al matrix.more » • A layer by layer growth within primary Al{sub 3}(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al{sub 3}(Sc,Zr)« less

Ag nanowires with diameters below 6 nm are grown within vortex containing superfluid helium nanodroplets and deposited onto a heatable substrate at cryogenic temperatures. The experimental setup allows an unbiased investigation of the inherent stability of pristine silver nanowires, which is virtually impossible with other methods due to chemical processes or templates involved in standard production routes. We demonstrate by experiment and by adaption of a theoretical model that initially continuous wires disintegrate into chains of spheres. This phenomenon is well described by a Rayleigh-like breakup mechanism when the substrate is heated to room temperature. Our findings clarify the recent discussions on the cause of the observed segmented patterns, where a breakup during deposition [Gomez et al., Phys. Rev. Lett., 2012, 108, 155302] or mechanisms intrinsic to the helium droplet mediated growth process [Spence et al., Phys. Chem. Chem. Phys., 2014, 16, 6903] have been proposed. The experimental setup confirms the validity of previous suggestions derived from bulk superfluid helium experiments [Gordon et al., Phys. Chem. Chem. Phys., 2014, 16, 25229] for the helium droplet system, and further allows a much more accurate determination of the breakup temperature.

The solute adsorption and/or segregation as well as the solute entrapment of Sr, Na and Yb atoms during eutectic Si growth in a series of high-purity Al–5 wt.% Si alloys was investigated by multi-scale microstructure characterization techniques, including high-resolution transmission electron microscopy and atomic-resolution scanning transmission electron microscopy. The adsorption of Sr atoms was directly observed along the 〈1 1 2〉Si growth direction of Si and/or at the intersection of multiple Si twins, which can be used to interpret the poisoning of the twin plane re-entrant edge and impurity induced twinning modification mechanisms, respectively. In contrast, Yb shows a different mechanism compared to the adsorption of Sr atoms. No significant Yb-rich cluster was observed at the intersection of Si twins. However, considerable Yb-rich segregation lines were observed along the 〈1 1 2〉Si direction, which can be attributed to the solute entrapment caused by a few Si twins through the natural twin plane re-entrant edge and growth mechanism. Active poisoning of the twin plane re-entrant edge and impurity induced twinning growth mechanisms cannot be observed due to the absence of Yb atoms within eutectic Si. Furthermore, the solute entrapment of modifying elements (X, Sr or Yb) together with Al and Si was proposed to interpret the formation of Al2Si2X phases or X-rich clusters within eutectic Si. Such types of Al2Si2X phases or X-rich clusters were further proposed to be an “artefact” caused by the solute entrapment during eutectic Si growth, rather than an active factor affecting the modification. The observed solute adsorption and entrapment can be used to interpret the different observations in the cases of different modifying elements, including impurity effects and so-called “quenching modification”, thereby elucidating the modification of eutectic Si in Al–Si alloys.

We present a study on the formation mechanism of copper zinc tin sulphide (CZTS) nanoparticles prepared from metal salts and 1-dodecanethiol in oleylamine. The nanoparticle sample exhibits two kinds of crystals, large ones with a size of about 70 nm and smaller ones with a diameter of about 25 nm. Analysis of the chemical composition of single nanoparticles revealed that the small nanoparticles consist of copper sulphide, while the larger ones are CZTS nanoparticles. A thorough investigation of the formation process of the nanoparticles revealed that the presence of the copper sulphide nanoparticles originates from the formation of copper sulphide nanoparticles in the initial nucleation step. These initial copper sulphide nanoparticles are converted to copper tin sulphide before the final CZTS nanoparticles are obtained.

The mechanical properties of Al alloys are strongly affected by their microstructure: the size and shape of precipitates, their homogeneous distribution and their coherency with the matrix are of primary importance for an effective strengthening of the alloys at room and elevated temperatures. Physically-based models are powerful tools to predict the influence of the mentioned parameters on the mechanical properties of the alloy after age hardening, and also to predict the effect of high temperature service conditions on microstructure evolution. Scope of this work is to model the dimensional kinetic evolution of plate shaped precipitates of an Al-based alloy during aging and after different overaging times at elevated temperature, and use these results to estimate the alloy yield strength. The alloy strengthening response is due to three terms, linearly summed: the intrinsic strength of Aluminum, the contribution from solute in solid solution and the contribution arising from precipitates. The consistency of the model is verified with experimental data obtained from a 2014 Al alloy.

The paper provides a new insight into the modification of eutectic Si in Al-Si based alloys. To date, impurity-induced twinning mechanism and twin plane re-entrant edge mechanism are the well-accepted theories. However, neither IIT nor TPRE can be used to interpret all modification observations. Therefore, a re-consideration of modification mechanisms is still required. In this contribution, recent advances on the understanding the modification of eutectic Si are reviewed. Two different cases are highlighted. In the case of Sr, Na and Eu addition, eutectic Si was modified from a faceted to a fibrous morphology, which involves the formation of multiple Si twinning. In the case of Yb and Ca addition, eutectic Si was refined to a smaller size, but still maintained a plate-like morphology. The possible modification mechanism was thus discussed in terms of (i) adsorption of atoms at twin re-entrant edge, and (ii) segregation across {111}Sigrowth planes. Furthermore, solute entrainment of modifying elements (M) was introduced to interpret the formation of Al2Si2M phase or M-rich clusters within Si crystals.

A series of high-purity Al–5 wt.% Si alloys with trace additions of Sr, Fe and P were prepared by using arc-melting and subsequent melt-spinning. The nucleation phenomenon incorporating the free growth criterion of eutectic Si was investigated by using the entrained droplet technique, atomic resolution scanning transmission electron microscopy and differential scanning calorimetry. It was found that Sr addition exerts no positive effect on the nucleation process; instead, an increased undercooling was observed. A combined addition of Sr and Fe further increased the undercooling, as compared with the addition of Sr only. Only trace P addition has a profound effect on the nucleation of Si by a proposed formation of AlP patches on primary Al. The estimated AlP patch size was found to be sufficient for the free growth of Si to occur inside the eutectic droplet. Nucleation kinetics was discussed on the basis of classical nucleation theory and the free growth model. For the first time, realistic and physically meaningful nucleation site values were obtained. The interactions between Sr and P were also highlighted. This investigation demonstrates strong experimental supports for the free growth nucleation kinetics and the well-accepted impurity-induced twinning growth mechanism, as well as the poisoning of the twin plane re-entrant edge growth mechanism.

Organic/inorganic hybrid solar cells are an interesting type of polymer based solar cells, which combine beneficial properties of inorganic semiconductors with them of polymer based materials, in particular, the easy processability on flexible plastic substrates. Herein, we present a method to prepare polymer/copper indium sulfide hybrid solar cells on flexible PET substrates via the metal xanthate route for the in situ preparation of ligand-free inorganic nanocrystals directly in the conjugated polymer matrix. The issue that the temperatures needed for the formation of the inorganic nanoparticles were too high to apply this preparation route on flexible substrates, was solved in this study by adding n-hexylamine to the precursor solution which facilitates the formation of higher crystalline nanoparticles at lower temperatures. n-Hexylamine thereby reacts with the xanthate forming the corresponding O-2,2-dimethylpentan-3-yl-N-hexylthiocarbamate. Following this modified route, flexible hybrid solar cells with power conversion efficiencies of 1.6% could be realized using temperatures not higher than 140 °C in the whole fabrication process. Furthermore, we demonstrate that the metal xanthate route is also well suited for the fabrication of larger area solar cells and present hybrid solar cell modules on glass as well as on flexible PET substrates. In addition, the lifetime of the prepared solar cells was investigated. The devices prepared at low temperature exhibited significantly improved stability compared to devices fabricated at 195 °C.

We investigate the growth of ZnS nanoparticles by a real-time simultaneous small and wide angle X-ray scattering (SAXS, WAXS) study using synchrotron radiation. Zinc chloride and elemental sulfur were dissolved in oleylamine. The formation of nanoparticles was induced by heating to 170 °C and 215 °C. The influence of temperature, reaction time, and sulfur concentration was investigated. After a short phase of rapid growth, saturation in size and a slower growth is observed depending on the temperature. The final size of the nanoparticles ranges between 2 and 6 nm for the investigated growth conditions and increases with the reaction temperature and sulfur concentration. SAXS analysis allows for determination of the size of the nanoparticles and proves also the existence of an organized layer of oleylamine molecules covering the nanoparticles' surfaces, which, however, appears only for diameters of the nanoparticles larger than approximately 2.8 nm. The investigation of the measured structure factor of the nanoparticle assemblies showed that the distance of an attractive interaction is 2.5 nm, which was interpreted as a consequence of the ordered oleylamine surface layer.

Coarse grained, well crystalline γ-LiAlO2 (P43212) is known as an electronic insulator and a very poor ion conductor with the lithium ions occupying tetrahedral voids in the oxide structure. The introduction of structural disorder such as point defects or higher-dimensional defects, however, may greatly affect ionic conduction on both short-range as well as long-range length scales. In the present study, we used high-energy ball milling to prepare defect-rich, nanocrystalline LiAlO2 that was characterized from a structural point of view by powder X-ray diffraction, TEM as well as small angle X-ray scattering (SAXS). Temperature-dependent conductivity spectroscopy revealed an increase of the room-temperature ionic conduction by several orders of magnitude when going from microcrystalline γ-LiAlO2 to its nanocrystalline form. The enhanced ion transport found is ascribed to the increase of Li ions near defective sites both in the bulk as well as in the large volume fraction of interfacial regions in nano-LiAlO2. The nanocrystalline ceramic prepared at long milling times is a mixture of γ-LiAlO2 and the high-pressure phase δ-LiAlO2; it adapts an amorphous like structure after it has been treated in a planetary mill under extremely harsh conditions.