2,028 research outputs found
Oxygen-deficient Nd0.8Sr1.2Ni0.8M0.2O4-δ (M = Ni, Co, Fe) nickelates as oxygen electrode materials for SOFC/SOEC
Ruddlesden-Popper Nd0.8Sr1.2Ni0.8M0.2O4±δ (M = Ni, Co, Fe)
nickelates have been characterized as prospective oxygen
electrode materials for solid electrolyte cells. XRD studies
showed that these oxides retain tetragonal K2NiF4-type structure
in air until at least 900°C. Average thermal expansion
coefficients of Nd0.8Sr1.2Ni0.8M0.2O4±δ calculated from the
structural data are in the range 14.5-15.8 ppm/K. TGA studies
revealed that these nickelates are oxygen-deficient in air at
temperature above 700°C but tends to oxygen stoichiometry or
minor excess on cooling. Incorporation of cobalt or iron into
nickel sublattice of Nd0.8Sr1.2NiO4-δ reduces oxygen deficiency
and electrical conductivity. Electrochemical impedance
spectroscopy studies of symmetrical cells showed that porous
Nd0.8Sr1.2Ni0.8M0.2O4-δ electrodes applied onto Ce0.9Gd0.1O2-δ
electrolyte exhibit quite similar performance, with lowest values
of polarization resistance (0.8 Ohm×cm2 at 800°C) observed for
M = Ni. The polarization resistance can be further decreased
(down to 0.04 Ohm×cm2 at 800°C for M = Ni) by surface
modification with PrOx.publishe
Oxygen-deficient perovskite-related (Nd0.4Sr0.6)2Ni0.8M0.2O4-δ as oxygen electrode materials for SOFC/SOEC
Perovskite-related Ln2NiO4+δ (Ln = La, Pr, Nd) nickelates with layered Ruddlesden-Popper combine redox
stability with noticeable oxygen stoichiometry changes, yielding enhanced mixed transport and
electrocatalytic properties. These unique features are promising for applications as oxygen electrodes with
good electrochemical performance in reversible SOFC/SOEC (solid oxide fuel/electrolysis cell) systems.
To date, most efforts were focused on oxygen-hyperstoichiometric Ln2NiO4+δ-based phases, whereas
nickelates with oxygen-deficient lattice remain poorly explored. Recent studies demonstrated that the
highest electrical conductivity in (Ln2-xSrx)2NiO4±δ series at elevated temperatures is observed for the
compositions containing ~ 60 at.% of strontium in A sublattice [1,2]. The present work was focused on the
characterization of (Nd0.4Sr0.6)2Ni0.8M0.2O4-δ (M = Ni, Co, Fe) nickelates for the possible use as materials
for reversible oxygen electrodes.
The ceramic materials were prepared by Pechini method with repeated annealings at 650-1200°C and
sintered at 1250-1300°C for 5 h under oxygen atmosphere. Variable-temperature XRD studies confirmed
that all studied compositions retain tetragonal K2NiF4-type structure in the temperature range 25-900°C.
The results of thermogravimetric analysis showed that the prepared nickelates has oxygen-deficient lattice
under oxidizing conditions at temperatures above 700°C. Partial substitution of nickel by cobalt or iron
results in a decrease of p-type electronic conductivity and the concentration of oxygen vacancies in the
lattice (Fig.1), but also suppresses dimensional changes associated with microcracking effects (due to
anisotropic thermal expansion of tetragonal lattice). Electrochemical performance of porous
(Nd0.4Sr0.6)2Ni0.8M0.2O4-δ electrodes in contact with Ce0.9Gd0.1O2-δ solid electrolyte was evaluated at 600-
800°C employing electrochemical impedance spectroscopy and steady-state polarization (anodic and
cathodic) measurements.publishe
Prototyping of petalets for the Phase-II Upgrade of the silicon strip tracking detector of the ATLAS Experiment
In the high luminosity era of the Large Hadron Collider, the HL-LHC, the
instantaneous luminosity is expected to reach unprecedented values, resulting
in about 200 proton-proton interactions in a typical bunch crossing. To cope
with the resultant increase in occupancy, bandwidth and radiation damage, the
ATLAS Inner Detector will be replaced by an all-silicon system, the Inner
Tracker (ITk). The ITk consists of a silicon pixel and a strip detector and
exploits the concept of modularity. Prototyping and testing of various strip
detector components has been carried out. This paper presents the developments
and results obtained with reduced-size structures equivalent to those foreseen
to be used in the forward region of the silicon strip detector. Referred to as
petalets, these structures are built around a composite sandwich with embedded
cooling pipes and electrical tapes for routing the signals and power. Detector
modules built using electronic flex boards and silicon strip sensors are glued
on both the front and back side surfaces of the carbon structure. Details are
given on the assembly, testing and evaluation of several petalets. Measurement
results of both mechanical and electrical quantities are shown. Moreover, an
outlook is given for improved prototyping plans for large structures.Comment: 22 pages for submission for Journal of Instrumentatio
КРИСТАЛЛИЧЕСКАЯ СТРУКТУРА И ФИЗИКО-ХИМИЧЕСКИЕ СВОЙСТВА ТВЕРДЫХ РАСТВОРОВ La2-xSmxNiO4+δ
Combined QCD and electroweak analysis of HERA data
A simultaneous fit of parton distribution functions (PDFs) and electroweak
parameters to HERA data on deep inelastic scattering is presented. The input
data are the neutral current and charged current inclusive cross sections which
were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In
addition, the polarisation of the electron beam was taken into account for the
ZEUS data recorded between 2004 and 2007. Results on the vector and
axial-vector couplings of the Z boson to u- and d-type quarks, on the value of
the electroweak mixing angle and the mass of the W boson are presented. The
values obtained for the electroweak parameters are in agreement with Standard
Model predictions.Comment: 32 pages, 10 figures, accepted by Phys. Rev. D. Small corrections
from proofing process and small change to Fig. 12 and Table
Measurement of the cross-section ratio sigma_{psi(2S)}/sigma_{J/psi(1S)} in deep inelastic exclusive ep scattering at HERA
The exclusive deep inelastic electroproduction of and
at an centre-of-mass energy of 317 GeV has been studied with the ZEUS
detector at HERA in the kinematic range GeV,
GeV and GeV, where is the photon virtuality, is the
photon-proton centre-of-mass energy and is the squared four-momentum
transfer at the proton vertex. The data for GeV were taken in
the HERA I running period and correspond to an integrated luminosity of 114
pb. The data for GeV are from both HERA I and HERA II
periods and correspond to an integrated luminosity of 468 pb. The decay
modes analysed were and for the
and for the . The cross-section ratio
has been measured as a function of
and . The results are compared to predictions of QCD-inspired
models of exclusive vector-meson production.Comment: 24 pages, 8 figure
Limits on the effective quark radius from inclusive scattering at HERA
The high-precision HERA data allows searches up to TeV scales for Beyond the
Standard Model contributions to electron-quark scattering. Combined
measurements of the inclusive deep inelastic cross sections in neutral and
charged current scattering corresponding to a luminosity of around 1
fb have been used in this analysis. A new approach to the beyond the
Standard Model analysis of the inclusive data is presented; simultaneous
fits of parton distribution functions together with contributions of "new
physics" processes were performed. Results are presented considering a finite
radius of quarks within the quark form-factor model. The resulting 95% C.L.
upper limit on the effective quark radius is cm.Comment: 10 pages, 4 figures, accepted by Phys. Lett.
Search for a narrow baryonic state decaying to and in deep inelastic scattering at HERA
A search for a narrow baryonic state in the and
system has been performed in collisions at HERA with the ZEUS detector
using an integrated luminosity of 358 pb taken in 2003-2007. The search
was performed with deep inelastic scattering events at an centre-of-mass
energy of 318 GeV for exchanged photon virtuality, , between 20 and 100
. Contrary to evidence presented for such a state around 1.52
GeV in a previous ZEUS analysis using a sample of 121 pb taken in
1996-2000, no resonance peak was found in the invariant-mass
distribution in the range 1.45-1.7 GeV. Upper limits on the production cross
section are set.Comment: 16 pages, 4 figures, accepted by Phys. Lett. B. Minor changes from
journal reviewing process, including a small correction to figure
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