Chemical stability in H2S and creep characterization of the mixed protonic conductor Nd5.5WO11.25-d

[EN] The integration of hydrogen permeable membranes in catalytic membrane reactors for thermodynamically limited reactions such as steam methane reforming can improve the per-pass yield and simultaneously produce a high-purity H-2 stream. Mixed protonic electronic materials based membranes are potential candidates for these applications due to their elevated temperature operation, good stability and potentially low cost. However, a specific mechanical behavior and stability under harsh atmospheres is needed to guarantee sufficient lifetime in real-world processes. This work presents the mechanical characterization and a study of the chemical stability under H2S containing atmospheres for the compound Nd5.5WO11.(25-8) Mechanical characterization was performed by micro indentation and creep measurements in air. Chemical stability was evaluated by XRD and SEM and the effect of the H2S on the transport properties was evaluated by impedance spectroscopy. Under H2S atmospheres, the total conductivity increases at 600 degrees C and 700 degrees C. The conductivity increase is attributed to the incorporation of S2- ions in oxide-ion sublattice. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.This work was financially supported by the Spanish Government (ENE2014-57651-R and SEV-2012-0267 grants). Authors would like to thank to U. Gerhards, M. Fabuel, T. Osipova and Dr. Wesel for WDS and SEM analysis.Escolástico Rozalén, S.; Stournari, V.; Malzbender, J.; Haas-Santo, K.; Dittmeyer, R.; Serra Alfaro, JM. (2018). Chemical stability in H2S and creep characterization of the mixed protonic conductor Nd5.5WO11.25-d. International Journal of Hydrogen Energy. 43(17):8342-8354. https://doi.org/10.1016/j.ijhydene.2018.03.060S83428354431

Promotion of mixed protonic–electronic transport in La5.4_{5.4}WO11.1−δ_{11.1− δ} membranes under H2_2S atmospheres

Catalytic membrane reactors (CMR) based on H$_2$-separation membranes can improve the performance of thermodynamically-limited reactions such as high-pressure steam methane reforming, ammonia cracking, non-oxidative aromatics production, and water gas shift reaction (WGS). In these industrial processes, the membrane surfaces are typically exposed to steam, CO$_2$, CO, H$_2$S, and hydrocarbons in combination with high temperatures. Therefore, the membrane materials require long-term thermo-chemical stability under the mentioned conditions. Stability in H$_2$S is of outstanding importance since its presence, even at ppm level, gives rise to substantial surface poisoning and decomposition of most materials. Here we characterize the influence of H$_2$S on the crystalline structure, lattice composition, and hydrogen-transport properties of La$_{5.4}$WO$_{11.1−δ}$, one of the reference protonic membrane materials. The incorporation of sulfide ions in the crystal lattice is ascertained from XRD, XPS, FESEM, WDS, EDS, and FIB-SIMS analyses. UV-vis spectroscopy and EIS measurements illustrate the effect of the incorporated sulfur in the transport properties, i.e., vigorously promoting the electronic conductivity mediated by the concurrent partial reduction of tungsten cations (W$^{6+}$). The rise in electronic conductivity allowed an H$_2$ flux of 0.042 mL cm$^{−2}$ min$^{−1}$ to be reached at 700 °C for a ∼700 μm-thick membrane, in contrast with negligible H$_2$ permeation in H$_2$S-free conditions

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS

Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector

A search for the direct production of the supersymmetric partners ofτ-leptons (staus) in final stateswith two hadronically decayingτ-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of139fb−1, recorded with the ATLAS detector at the LargeHadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected StandardModel background is observed. Limits are derived in scenarios of direct production of stau pairs with eachstau decaying into the stable lightest neutralino and oneτ-lepton in simplified models where the two staumass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidencelevel for a massless lightest neutralino