611 research outputs found
Correlations between stacked structures and weak itinerant magnetic properties of La Y Ni compounds
Hexagonal LaNi and rhombohedral YNi are weak itinerant
antiferromagnet (wAFM) and ferromagnet (wFM), respectively. The crystal
structure and magnetic properties of intermetallic compounds ( =
La, Y, = Ni) have been investigated combining X-ray powder diffraction and
magnetic measurements. The LaYNi intermetallic compounds with
crystallize in the CeNi-type hexagonal structure
with Y preferentially located in the [] units. The compounds with larger
Y content () crystallize in both hexagonal and rhombohedral
(GdCo-type) structures with a progressive substitution of Y for La in
the sites belonging to the [] units. YNi crystallizes in the
rhombohedral structure only. The average cell volume decreases linearly versus
Y content, whereas the c/a ratio presents a minimum at due to geometric
constrains. The magnetic properties are strongly dependent on the structure
type and the Y content. LaNi displays a complex metamagnetic behavior
with split AFM peaks. Compounds with x = 0.25 and 0.5 display a wAFM ground
state and two metamagnetic transitions, the first one towards an intermediate
wAFM state and the second one towards a FM state.T and the second critical
field increase with the Y content, indicating a stabilization of the AFM state.
LaYNi, which is as the boundary between the two structure types, presents a
very wFM state at low field and an AFM state as the applied field increases.
All the compounds with and containing a rhombohedral phase are wFM with
= 53(2) K. In addition to the experimental studies, first principles
calculations using spin polarization have been performed to interpret the
evolution of both structural phase stability and magnetic ordering for .Comment: 26 pages (7 for supplementary material), 4 tables, 9 main figures and
8 figures in supplementary materia
Study of the ternary system Al–H– RE ( RE = Er, La and Y) in liquid state
International audienc
A Dissipative Model for Hydrogen Storage: Existence and Regularity Results
We prove global existence of a solution to an initial and boundary value
problem for a highly nonlinear PDE system. The problem arises from a
thermomechanical dissipative model describing hydrogen storage by use of metal
hydrides. In order to treat the model from an analytical point of view, we
formulate it as a phase transition phenomenon thanks to the introduction of a
suitable phase variable. Continuum mechanics laws lead to an evolutionary
problem involving three state variables: the temperature, the phase parameter
and the pressure. The problem thus consists of three coupled partial
differential equations combined with initial and boundary conditions. Existence
and regularity of the solutions are here investigated by means of a time
discretization-a priori estimates-passage to the limit procedure joined with
compactness and monotonicity arguments
Solid-state Li-ion batteries operating at room temperature using new borohydride argyrodite electrolytes
Using a new class of (BH4)- substituted argyrodite Li6PS5Z0.83(BH4)0.17, (Z =
Cl, I) solid electrolyte, Li-metal solid-state batteries operating at room
temperature have been developed. The cells were made by combining the modified
argyrodite with an In-Li anode and two types of cathode: an oxide, LixMO2 (M =
1/3Ni, 1/3Mn, 1/3Co; so called NMC) and a titanium disulfide, TiS2. The
performance of the cells was evaluated through galvanostatic cycling and
Alternating Current AC electrochemical impedance measurements. Reversible
capacities were observed for both cathodes for at least tens of cycles.
However, the high-voltage oxide cathode cell shows lower reversible capacity
and larger fading upon cycling than the sulfide one. The AC impedance
measurements revealed an increasing interfacial resistance at the cathode side
for the oxide cathode inducing the capacity fading. This resistance was
attributed to the intrinsic poor conductivity of NMC and interfacial reactions
between the oxide material and the argyrodite electrolyte. On the contrary, the
low interfacial resistance of the TiS2 cell during cycling evidences a better
chemical compatibility between this active material and substituted
argyrodites, allowing full cycling of the cathode material, 240 mAhg-1, for at
least 35 cycles with a coulombic efficiency above 97%
Impact of Surface Chemistry of Silicon Nanoparticles on the Structural and Electrochemical Properties of Si/Ni3.4Sn4 Com-posite Anode for Li-Ion Batteries
Embedding silicon nanoparticles in an intermetallic matrix is a promising
strategy to produce remarkable bulk anode materials for lithium-ion (Li-ion)
batteries with low potential, high electrochemical capacity and good cycling
stability. These composite materials can be synthetized at a large scale using
mechanical milling. However, for Si-Ni3Sn4 composites, milling also induces a
chemical reaction between the two components leading to the formation of free
Sn and NiSi2, which is detrimental to the performance of the electrode. To
prevent this reaction, a modification of the surface chemistry of the silicon
has been undertaken. Si nanoparticles coated with a surface layer of either
carbon or oxide were used instead of pure silicon. The influence of the coating
on the composition, (micro)structure and electrochemical properties of
Si-Ni3Sn4 composites is studied and compared with that of pure Si. Si coating
strongly reduces the reaction between Si and Ni3Sn4 during milling. Moreover,
contrary to pure silicon, Si-coated composites have a plate-like mor-phology in
which the surface-modified silicon particles are surrounded by a
nanostructured, Ni3Sn4-based matrix leading to smooth potential profiles during
electrochemical cycling. The chemical homogeneity of the matrix is more uniform
for carbon-coated than for oxygen-coated silicon. As a consequence, different
electrochemical behaviors are obtained depending on the surface chemistry, with
better lithiation properties for the carbon-covered silicon able to deliver
over 500 mAh/g for at least 400 cycles
Mechanochemical synthesis of pseudobinary Ti-V hydrides and their conversion reaction with Li and Na
Lithium-ion batteries (LiBs) based on insertion electrodes reach intrinsic
capacity limits. Performance improvements and cost reduction require
alternative reaction mechanisms and novel battery chemistries such as
conversion reactions and sodium-ion batteries (NaBs), respectively. We here
study the formation of Ti1-xVxH2 hydrides (0 < x < 1) and their electrochemical
properties as anodes in LiBs and NaBs half-cells. Hydrides were synthesized by
mechanochemistry of the metal powders under hydrogen atmosphere (PH2~ 8 MPa).
For V contents below 80 at.% (x < 0.8), single-phase pseudobinary dihydride
compounds Ti1-xVxH2 are formed. They crystallize in the fluorite-type structure
and are highly nanostructured (crystallite size < 10 nm). Their lattice
parameter decreases linearly with the V content leading to hydride
destabilization. Electrochemical studies were first carried out in Li-ion half
cells with full conversion between Ti1-xVxH2 hydrides and lithium. The
potential of the conversion reaction can be gradually tuned with the vanadium
content due to its destabilization effect. Furthermore, different paths for the
conversion reaction are observed for Ti-rich (x 0.7)
alloys. Na-ion half-cell measurements prove the reactivity between (V,Ti)H2
hydrides and sodium, albeit with significant kinetic limitation
Стратегия хирургического лечения местнораспространенных опухолей малого таза с применением эвисцераций. Сообщение1. Синдромы кишечной непроходимости, кровотечения и сдавления мочевых путей
Представлен обзор и анализ методов хирургической коррекции синдромов кишечной непроходимости, кровотечения и сдавления мочевых путей при местнораспространенных опухолях малого таза. Обобщен 10−летний опыт хирургического лечения данной патологии в Институте общей и неотложной хирургии. Приведена классификация основных методов оперативных пособий, направленных на достижение гемостаза и деривации мочи и кала.The methods of surgical correction of syndromes of intestinal obstruction, hemorrhage and urinary tract compression at local tumors of the small pelvis are reviewed and analyzed. The 10−year experience of surgical treatment for this pathology at Institute for General and Urgent Surgery is generalized. Main methods of operative treatment aimed at achievement of hemostasis and urine and feces derivation are presented
Role of silicon and carbon on the structural and electrochemical properties of Si-NiSn-Al-C anodes for Li-ion batteries
Varying the amounts of silicon and carbon, different composites have been
prepared by ball milling of Si, NiSn, Al and C. Silicon and carbon
contents are varied from 10 to 30 wt.% Si, and 0 to 20 wt.% C. The
microstructural and electrochemical properties of the composites have been
investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and
electrochemical galvanostatic cycling up to 1000 cycles. Impact of silicon and
carbon contents on the phase occurrence, electrochemical capacity and
cycle-life are compared and discussed. For C-content comprised between 9 and 13
wt.% and Si-content >= 20 wt.%, Si nanoparticles are embedded in a
NiSn-Al-C matrix which is chemically homogeneous at the micrometric
scale. For other carbon contents and low Si-amount (10 wt.%), no homogeneous
matrix is formed around Si nanoparticles. When homogenous matrix is formed,
both NiSn and Si participate to the reversible lithiation mechanism,
whereas no reaction between NiSn and Li is observed for no homogenous
matrix. Moreover, best cycle-life performances are obtained when Si
nanoparticles are embedded in a homogenous matrix and Si-content is moderate
(<= 20 wt.%). Composites with carbon in the 9-13 wt.% range and 20 wt.% silicon
lead to the best balance between capacity and life duration upon cycling. This
work experimentally demonstrates that embedding Si in an intermetallic/carbon
matrix allows to efficiently accommodate Si volume changes on cycling to ensure
long cycle-life
In-situ neutron diffraction during reversible deuterium loading in Ti-rich and Mn-substituted Ti(Fe,Mn)0.90 alloys
Hydrogen is an efficient energy carrier that can be produced from renewable sources, enabling the transition towards CO2-free energy. Hydrogen can be stored for a long period in the solid-state, with suitable alloys. Ti-rich TiFe0.90 compound exhibits a mild activation process for the first hydrogenation, and Ti (Fe,Mn)0.90 substituted alloys can lead to the fine tuning of equilibrium pressure as a function of the final application. In this study, the crystal structure of TiFe(0.90-x)Mnx alloys (x = 0, 0.05 and 0.10) and their deuterides has been determined by in-situ neutron diffraction, while recording Pressure-Composition Isotherms at room temperature. The investigation aims at analysing the influence of Mn for Fe substitution in Ti-rich Ti(Fe,Mn)0.90 alloys on structural properties during reversible deuterium loading, which is still unsolved and seldom explored. After activation, samples have been transferred into custom-made stainlesssteel and aluminium alloy cells used for in-situ neutron diffraction experiments during deuterium loading at ILL and ISIS neutron facilities, respectively. The study enables remarkable understanding on hydrogen storage, basic structural knowledge, and support to the industrial application of TiFe-type alloys for integrated hydrogen tank in energy storage systems by determining the volume expansion during deuteration. Furthermore, the study demonstrates that different contents of Mn do not significantly change the volumetric expansion during phase transitions, affecting only the deuterium content for the gamma phase and the cell evolution for the beta phase. The study confirms that the deuterated structures of the gamma phase upon absorption, beta and ' phase upon desorption, correspond to S.G. Cmmm, P2221 and Pm-3m, respectively.(c) 2022 Elsevier B.V. All rights reserved
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