Stardust Interstellar Preliminary Examination (ISPE)

In January 2006 the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, C omet 81P/Wild2, and a collector dedicated to the capture and return o f contemporary interstellar dust. Both collectors were approximately 0.1m(exp 2) in area and were composed of aerogel tiles (85% of the co llecting area) and aluminum foils. The Stardust Interstellar Dust Col lector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 m(exp 2-) day during two periods before the co metary encounter. The Stardust Interstellar Preliminary Examination ( ISPE) is a three-year effort to characterize the collection using no ndestructive techniques. The ISPE consists of six interdependent proj ects: (1) Candidate identification through automated digital microsco py and a massively distributed, calibrated search (2) Candidate extr action and photodocumentation (3) Characterization of candidates thro ugh synchrotronbased FourierTranform Infrared Spectroscopy (FTIR), S canning XRay Fluoresence Microscopy (SXRF), and Scanning Transmission Xray Microscopy (STXM) (4) Search for and analysis of craters in f oils through FESEM scanning, Auger Spectroscopy and synchrotronbased Photoemission Electron Microscopy (PEEM) (5) Modeling of interstell ar dust transport in the solar system (6) Laboratory simulations of h ypervelocity dust impacts into the collecting medi

Analysis of "Midnight" Tracks in the Stardust Interstellar Dust Collector: Possible Discovery of a Contemporary Interstellar Dust Grain

In January 2006, the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were approximately 0.1m(exp 2) in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 m(exp 2) day. The Stardust Interstellar Preliminary Examination (ISPE) is a three-year effort to characterize the collection using nondestructive techniques

A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts

Since its commercial introduction three-quarters of a century ago, fluid catalytic cracking has been one of the most important conversion processes in the petroleum industry. In this process, porous composites composed of zeolite and clay crack the heavy fractions in crude oil into transportation fuel and petrochemical feedstocks. Yet, over time the catalytic activity of these composite particles decreases. Here, we report on ptychographic tomography, diffraction, and fluorescence tomography, as well as electron microscopy measurements, which elucidate the structural changes that lead to catalyst deactivation. In combination, these measurements reveal zeolite amorphization and distinct structural changes on the particle exterior as the driving forces behind catalyst deactivation. Amorphization of zeolites, in particular, close to the particle exterior, results in a reduction of catalytic capacity. A concretion of the outermost particle layer into a dense amorphous silica–alumina shell further reduces the mass transport to the active sites within the composite

Mineralogy and petrology of comet 81P/wild 2 nucleus samples

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk

Mineralogy and Petrology of Comet Wild 2 Nucleus Samples

The bulk of the Wild 2 samples appear to be weakly-constructed mixtures of nanometerscale grains with occasional much larger (>1{micro}m) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in Wild 2 require a wide range of formation conditions, probably reflecting different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and absence of hydrous phases indicate that Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require large-scale radial transport in the early protoplanetary disk. The nature of cometary solids is of fundamental importance to our understanding of the early solar nebula and protoplanetary history. Until now we have had to study comets from afar using spectroscopy, or settle for analyses of interplanetary dust particles (IDPs) of uncertain provenance. We report here mineralogical and petrographic analyses of particles derived directly from Comet Wild 2. All of the Wild 2 particles we have thus far examined have been modified in various ways by the capture process. All particles that may have been loose aggregates, ''traveling sand piles'', disaggregated into individual components with the larger, denser components penetrating more deeply into the aerogel. Individual grains experienced a wide range of heating effects that range from excellent preservation to melting (Fig. 1); such behavior was expected (1, 2 ,3). What is remarkable is the extreme variability of these modifications and the fact that severely modified and unmodified materials can be found within a micrometer of each other, requiring tremendous local temperature gradients. Fortunately, we have an internal gauge of impact collection heating. Fe-Ni sulfides are ubiquitous in the Wild 2 samples, are very sensitive indicators of heating, and accurate chemical analyses can reveal which have lost S, and which have not (and are therefore stoichiometric) (Fig. 2). Our surveys show that crystalline grains are found along the entire lengths of tracks, not just at track termini

Reflow processes in micro-bumps studied by synchrotron X-ray projection nanotomography

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A new white beam x-ray microdiffraction setup on the BM32 beamline at the European Synchrotron Radiation Facility

International audienceA white beam microdiffraction setup has been developed on the bending magnet source BM32 at the European Synchrotron Radiation Facility. The instrument allows routine submicrometer beam diffraction to perform orientation and strain mapping of polycrystalline samples. The setup features large source to optics distances allowing large demagnification ratios and small beam sizes. The optics of the beamline is used for beam conditioning upstream a secondary source, suppressing any possible interference of beam conditioning on beam size and position. The setup has been designed for an easy and efficient operation with position control tools embedded on the sample stage, a high magnification large aperture optical microscope, and fast readout detectors. Switching from the white beam mode to the monochromatic mode is made easy by an automatic procedure and allows the determination of both the deviatoric and hydrostatic strain tensors

Role of microstructure on electrode operating mechanisms for mixed ionic electronic conductors: From synchrotron-based 3D reconstruction to electrochemical modeling

A typical La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) electrode was reconstructed by X-ray nanotomography. The new Nano Imaging beamline ID16A-NI of the European Synchrotron Radiation Facility (ESRF) was used to conduct the investigation. Particular attention was paid to prepare samples with a well-adapted shape for the tomographic experiments. The optimized sample preparation and new experimental set-up enables an improved spatial resolution of about 50 nm to be obtained in the electrode reconstruction of 51.2 x 25.6(2) x pi mu m(3). The LSCF microstructural properties were quantified in the 3D volume and used as input data in a dynamic micro scale electrochemical model. The numerical tool includes two parallel reaction pathways with an oxygen exchange at the LSCF/gas surface and a charge transfer at the electrode TPB. Electrochemical impedances were computed in the time domain at OCP, as well as under anodic and cathodic polarizations. Simulations allowed the microstructural parameters to be linked to the basic mechanisms of electrode operation according to the electrode polarization. A microstructural sensitivity analysis was performed on the single-phase LSCF and LSCF-CGO composite electrodes in order to identify the parameters that impact most the electrode response. It was found that the LSCF-CGO composite presents much higher performances compared to the LSCF single phase electrode especially in anodic polarization. (C) 2016 Elsevier B.V. All rights reserved

3D morphological and structural nano-characterization for microelectronics: the potential of recent, long synchrotron beamlines

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Multi-scale 3D imaging of absorbing porous materials for solid oxide fuel cells.

International audienceThe performance of advanced functional materials for fuel cell applications are closely linked to the material composition and morphology at the micro and nano-scales. 3D characterization techniques that can provide bulk information at these fine scales are therefore essential for microstructure optimization of these materials. Here, the X-ray nano-holotomography technique is used to image various multi-phase and absorbing solid oxide fuel cell electrodes. Different porous structures for typical commercial cells and innovative electrode designs obtained using a freeze-casting process are studied. Taking advantage of the geometrical setup and the use of high energy X-rays, both large reconstructions (field of view: 150 A mu m) and local tomography at higher resolution (field of view: 50 A mu m) can be performed on the same sample to have a multi-scale approach. This produces highly representative sample volumes with a size/resolution ratio that allows the geometric and physical properties of the materials to be calculated, e.g., connectivity of each phase, mean particles diameters, specific surface area, particle size distributions, tortuosity factors, and densities of triple boundary lengths