Quantum-Chemical Study of the FeNCN Conversion-Reaction Mechanism in Lithium- and Sodium-Ion Batteries

We report a computational study on 3d transition-metal (Cr, Mn, Fe, and Co) carbodiimides in Li- and Na-ion batteries. The obtained cell voltages semi-quantitatively fit the experiments, highlighting the practicality of PBE+U as an approach for modeling the conversion-reaction mechanism of the FeNCN archetype with lithium and sodium. Also, the calculated voltage profiles agree satisfactorily with experiment both for full (Li-ion battery) and partial (Na-ion battery) discharge, even though experimental atomistic knowledge is missing up to now. Moreover, we rationalize the structural preference of intermediate ternaries and their characteristic lowering in the voltage profile using chemical-bonding and Mulliken-charge analysis. The formation of such ternary intermediates for the lithiation of FeNCN and the contribution of at least one ternary intermediate is also confirmed experimentally. This theoretical approach, aided by experimental findings, supports the atomistic exploration of electrode materials governed by conversion reactions.     

Simple and efficient synthesis of racemic 2-(tert-butoxycarbon-ylamino)-2-methyl-3-(1H-1,2,4-triazol-1-yl)propanoic acid, a new derivative of β-(1,2,4-triazol-1-yl)alanine

A simple synthetic approach to racemic N-tert-butyloxycarbonyl-2-methyl-3-(1H-1,2,4-triazol-1-yl)alanine (5) in four steps and 68% overall yield starting from oxazoline derivative 1 is reported. This synthesis involves the alkylation of 1H-1,2,4-triazole with an O-tosyloxazoline derivative, followed by an oxazoline ring-opening reaction and oxidation of the N-protected β?aminoalcohol by potassium permanganate.     

Structural and magnetic properties of Pr18Li8Fe5−xMxO39 (M=Ru, Mn, Co)

A polycrystalline sample of Pr₁₈Li₈Fe₄RuO₃₉ has been synthesized by a solid state method and characterized by neutron powder diffraction, magnetometry and Mössbauer spectroscopy; samples of Pr₁₈Li₈Fe_5−xMn_xO₃₉ and Pr₁₈Li₈Fe_5−xCo_xO₃₉ (x=1, 2) have been studied by magnetometry. All these compounds adopt a cubic structure (space group , a₀∼11.97 Å) based on intersecting 〈111〉 chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Pr-O framework. The trigonal-prismatic site in Pr₁₈Li₈Fe₄RuO₃₉ is occupied by Li⁺ and high-spin Fe³⁺. The remaining transition-metal cations occupy the two crystallographically-distinct octahedral sites in a disordered manner. All five compositions adopt a spin-glass-like state at 7 K (Pr₁₈Li₈Fe₄RuO₃₉) or below.     

Role of iron in Na <Subscript>1.5</Subscript>Fe <Subscript>0.5</Subscript>Ti <Subscript>1.5</Subscript>(PO <Subscript>4</Subscript>) <Subscript>3</Subscript>/C as electrode material for Na-ion batteries studied by operando Mössbauer spectroscopy

The role of iron in Na _1.5Fe _0.5Ti _1.5(PO ₄)₃/C electrode material for Na batteries has been studied by ⁵⁷Fe Mössbauer spectroscopy in operando mode. The potential profile obtained in the galvanostatic regime shows three plateaus at different voltages due to different reaction mechanisms. Two of them, at 2.2 and 0.3 V vs Na ⁺/Na ⁰, have been associated to redox processes involving iron and titanium in Na _1.5Fe _0.5Ti _1.5(PO ₄)₃. The role of titanium was previously elucidated for NaTi ₂(PO ₄)₃ and the effect of the substitution of Fe for Ti was investigated with ⁵⁷Fe Mössbauer spectroscopy. We show that iron is an electrochemically active center at 2.2 V with the reversible Fe ³⁺/Fe ²⁺ transformation and then remains at the oxidation state Fe ²⁺ along the sodiation until the end of discharge at 0 V.     

Autocatalytic sonolysis of iron pentacarbonyl in room temperature ionic liquid [BuMeIm][Tf2N

The autocatalytic sonochemical reaction of Fe(CO)(5) decomposition in [BuMeIm][Tf(2)N] provides iron nanoparticles in higher yields than in tetralin. Such a difference is explained by the higher decomposition of the intermediate Fe(3)(CO)(12) according to the two-sites model of the sonochemical reactions and the specific properties of the ionic liquid.     

Rheology of physically evolving suspensions

The objective of this work was to investigate the modeling of the whole dynamic rheological behavior of physically evolving suspensions (e.g., polyvinyl chloride plastisols). The evolutions of the complex viscosity with time (isothermal) and with temperature (non-isothermal) were analyzed. To understand the physically involved phenomena, the determination of relationships between the solid volume fraction evolution and the rheological behavior was investigated. Firstly, the evolution of the volume fraction in relation with the variation of radii particle suspensions using a modified Avrami equation was determined. Actually, the rheological study of this physically evolving system is far too complicated due to the many factors involved in the evolving process. Consequently, a phenomenological law using Carreau–Yasuda equation and percolation laws combined with the evolution of the solid volume fraction is investigated to obtain the modeling of the whole dynamic rheological behavior at any frequency and temperature.     

Role of hypaphorine in the toxicity of Astragalus lusitanicus

Hypaphorine, an alpha-N,N,N-trimethyltryptophan betaine, was isolated, for the first time, from Astragalus lusitanicus Lam. (Fabaceae), a plant highly toxic for lambs and goats. This alkaloid was characterized by NMR and MS analysis. Hypaphorine was previously reported to be a convulsive poison. To confirm the toxicity, it was synthesized and tested in goats. Hypaphorine was shown to be non-toxic for goats even at a high dose of 2 g kg(-1) by oral administration.     

Existence Results for Some Partial Integro-Differential Equations

In this note, we deal with semilinear integro-differential equations subject to homogeneous Dirichlet boundary conditions given on the boundaries of the sections. Even if the differentiation will be taken only in some directions, it is not possible to see the main problem parameterized by the other coordinates because of the non-local terms which also obliged the problem to be degenerate. We establish the existence of solutions by employing the singular perturbations method as a natural tool. The perturbed problems are classical, non-local, semilinear elliptic problems and the limits of the subsequences of their solutions, in weighted Sobolev type spaces, are solutions of the main problem. Some improvement, concerning the existence of the solutions and the convergence results depending on the weights, will be established. The paper also gives an idea about the study of the anisotropic singular perturbations in the framework of weighted spaces.     

Comportement mécanique et rupture de milieux granulaires cohésifsMechanical behaviour and rupture of cohesive granular media

The modelling of mechanical behaviour and rupture of cohesive granular media is carried out on a model medium made of aluminium cylinders and cohesive bonds playing the role of cohesion points. The mechanical behaviour of the cohesion point is studied under different loading situations (compression, traction, shearing, torque). The results are introduced into a code, which is based on a discrete element method extended to the cohesive case. The validation is achieved with compression tests of macroscopic samples. We notice a good correlation between simulation and experiment on the mechanical behaviour, on the appearance of fractures and their propagation. To cite this article: J.-Y. Delenne et al., C. R. Mecanique 330 (2002) 475–482.