Investigation of the possible incorporation of protons into oxide cathodes during chemical delithiation

Chemical delithiation of layered LiCoO₂, LiNi_0.5Mn_0.5O₂, and Li₂MnO₃ and spinel LiMn₂O₄ cathodes have been investigated with both an acetonitrile (non-aqueous) solution of the oxidizer NO₂BF₄ and an aqueous acid. The products have been characterized by X-ray diffraction, wet chemical analyses for lithium and oxygen contents, infrared spectroscopy, and thermogravimetric analysis to determine whether or not protons are incorporated into the lattice during the delithiation process. While the delithiation in aqueous acid medium leads to an incorporation of protons into the layered oxide lattice, the non-aqueous delithiation with NO₂BF₄ does not involve any proton insertion into the lattice. In contrast to the layered oxides, the chemical delithiation of spinel LiMn₂O₄ even in the aqueous acid medium does not involve any proton insertion into the lattice.     

Adsorptive removal of thorium from aqueous solution using diglycolamide functionalized multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were functionalized with diglycolamide (DGA) through chemical covalent route. The adsorption behavior of the DGA-functionalized-MWCNTs (DGA-MWCNTs) towards thorium from aqueous solution was studied under varying operating conditions of pH, concentration of thorium, DGA-MWCNTs dosages, contact time, and temperature. The effective range of pH for the removal of Th(IV) is 3.0–4.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. The equilibrium data are best fitted with Langmuir model. The equilibrium Th(IV) sorption capacity was estimated to be 10.58 mg g^?1 at 298 K. The standard enthalpy, entropy, and free energy of adsorption of the thorium with DGA-MWCNTs were calculated to be 8.952 kJ mol^?1, 0.093 kJ mol^?1 K^?1 and -18.521 kJ mol^?1 respectively at 298 K. The determined value of sticking probability (0.072) and observed kinetic and isotherm models reveal the chemical adsorption of thorium on DGA-MWCNTs.     

Synthesis of some 4-substituted and 4,6-disubstituted dibenzothiophenes

The synthesis is described of various 4-substituted ( 1 ) and 4,6-disubstituted ( 2 ) dibenzothiophenes by lithiation reactions. The factors controlling the formation of 4,6-disubstituted dibenzothiophenes by the lithiation of 4-methyl- and 4-ethyl-dibenzothiophene at the 6-position versus lithiation at the α-carbon of the 4-substituent are examined.     

Synthesis of benzosuberone-tethered spirooxindoles: 1-3-dipolar cycloaddition of azomethine ylides and arylidene benzosuberones

Molecular Diversity - Expedient synthesis of benzosuberone-tethered spirooxindoles was accomplished by a three-component 1,3-dipolar cycloaddition reaction between azomethine ylide (generated in...     

Stiffness based technique to probe cyclic damage accumulation in micro-structurally graded bond coats via micro-beam bending tests

This paper highlights a novel technique to delineate the fatigue response of different regions within thin microstructurally graded platinum nickel aluminide bond coats. Notched clamped beam structures fabricated from distinct microstructural zones of these coatings are subjected to programmed cyclic bending using the nano-indentation system. A methodical approach is established herein to quantify the cyclic damage preceding crack pop-in by using the cyclic stiffness of the beam as an indicator to mark failure. Preliminary results from these tests show that there is a characteristic change in the stiffness of the beam before a crack pop-in event occurs and different regions within the coating show different stiffening characteristics. Factors affecting the measured stiffness such as offsets in the loading position and blunting of the notch tip have been estimated using the finite element method. A graded flow stress model has been proposed and implemented in FEM to quantify the local flow stress changes accompanying the measured rise in stiffness. Electron transparent foils lifted off from the notched region of the beam post-testing suggests that the cyclic stiffening of the beams occurs due to dislocation hardening in the plastically deformed region close to the notch tip. Toughening mechanisms active in the crack wake have thus been investigated and correlated to the measured cyclic stiffness.     

Application of ring-closing metathesis for the synthesis of macrocyclic peptidomimetics as inhibitors of HCV NS3 protease

An efficient synthetic approach for the preparation of macrocyclic peptidomimetics for inhibition of HCV NS3 is presented. The macrocyclic core is built using ring-closing metathesis (RCM) of a tripeptidic diene. The presented approach allows the introduction of heteroatoms in strategic places along the macrocyclic ring. The methyl ester moiety in the RCM products was synthetically manipulated to install a keto-amide moiety via a Passerini reaction.     

A DFT and MP2 Study on the Molecular Structure and Vibrational Spectra of Halogenosubstituted Phosphoryl and Thiophosphoryl Compounds

The molecular geometrical parameters, rotational constants, dipole moments and vibrational infrared properties of a series of phosphoryl compounds (OPX _i Y _j Z _k , X, Y, Z = F, Cl, Br; i+ j + k = 3) and their thio analogs are predicted by density functional and MP2 calculations using the 6-311G(2d,2p) basis set. Both methods yielded similar results. The predicted molecular parameters and the vibrational Raman and infrared spectra agree well with the available experimental data. The Raman Scattering Activities (RSA) and depolarization ratios (Dep) of the molecules are obtained by DFT calculations. Considering the different substitution modes of various halogen atoms, the resultant changes in the geometrical and vibrational properties are discussed. Such studies permit detailed information to be obtained concerning unknown molecules and can define the guidelines for synthesizing molecules of particular characteristics.     

Kinetic studies on the radical polymerization of acrylamide initiated by Mn3+–ethoxyacetic acid redox system

The kinetics of polymerization of acrylamide (AM) initiated by manganese(III) acetate–ethoxyacetic acid (EAA) redox system in aqueous sulphuric acid was investigated in the temperature range 35–45°C. The effects of variations in [monomer], [Mn³⁺], [EAA], [H⁺], and ionic strength on the rates of monomer disappearance (R_p) and Mn³⁺ disappearance (?R_m) were studied. The polymerization process is initiated by the free radical arising from the oxidation of ethoxyacetic acid by Mn³⁺ and terminated by the mutual combination of growing polymer radicals. Based on the kinetic results, a suitable reaction scheme is proposed and the rate expressions are derived. The study on degree of polymerization supports the proposed scheme for polymerization. The various rate and thermodynamic parameters are evaluated.     

Evolution of weak shocks in one dimensional planar and non-planar gasdynamic flows

Asymptotic decay laws for planar and non-planar shock waves and the first order associated discontinuities that catch up with the shock from behind are obtained using four different approximation methods. The singular surface theory is used to derive a pair of transport equations for the shock strength and the associated first order discontinuity, which represents the effect of precursor disturbances that overtake the shock from behind. The asymptotic behaviour of both the discontinuities is completely analysed. It is noticed that the decay of a first order discontinuity is much faster than the decay of the shock; indeed, if the amplitude of the accompanying discontinuity is small then the shock decays faster as compared to the case when the amplitude of the first order discontinuity is finite (not necessarily small). It is shown that for a weak shock, the precursor disturbance evolves like an acceleration wave at the leading order. We show that the asymptotic decay laws for weak shocks and the accompanying first order discontinuity are exactly the ones obtained by using the theory of non-linear geometrical optics, the theory of simple waves using Riemann invariants, and the theory of relatively undistorted waves. It follows that the relatively undistorted wave approximation is a consequence of the simple wave formalism using Riemann invariants.