A galvanostatic study of lithium intercalation in RuO2

The diffusion process in a host structure has been studied at constant current with the cells: RuO₂ composite/ LiClO₄PEO/Li and RuO₂ powder/LiClO₄PC/Li. The effect of grain size distribution and temperature has been investigated and the diffusion coefficient for Li in RuO₂ calculated along with the diffusion activation energy (0.52 eV). Results show no intercalation of PC at 25°C.     

Volume properties and compressibility of the graphite-potassium-mercury compounds

Abstract

The volume properties of graphite intercalation compounds (GIGS) C4KHg and of the initial intermetallic compounds KHg and KHg₂ have been investigated in the piston-cylinder apparatus, using the direct volumetric technique, under pressures up to 25 kbar. The compounds, average compressibility K₊, was determined to be 3.8×10^?3 kbar^?1 for C₄KHg, 3.0×10^?3 kbar-^?1 for C₈KHg, 4.8×10^?1 kbar^?1 for KHg, and 4.0 ×10^?1 kbar^?1 for KHg₂ at pressures of 0-20 kbar. The compressibility of the “two-dimensional” KHg layer in the GIC under various pressure conditions has been estimated. These estimates permit comparison of KHg properties in the “three dimensional” and “quasi-two dimensional” states. It was concluded that the influence of the graphite matrix on the intercalant is insignificant for this type ternary GIC.     

Die Diffusionskoeffizienten und mittleren freien Weglängen der geladenen und neutralen Radon-Folgeprodukte in Luft

The knowledge of the diffusion coefficients of radioactive atoms and ions in air is very important in a number of investigations on and computations of the attachment of radon decay products to aerosol particles. In this work measurements of the diffusion coefficients of neutral and charged²¹²Pb atoms are reported. The values found areD ₀=(7.6±0.4)·10^?2cm²s^?1 for neutral atomsD=(5.0±0.3)·10^?2cm²s^?1 for charged atoms The used method of measurement allowed to determine these constants 1–5 seconds after the formation aged²¹²Pb atoms, so that a “cluster” formation was improbable. The mean free path for neutral (λ₀=(4.9±0.3)·10^?6cm) and charged (λ=(3.2±0.2)· 10^?6cm) lead 212 atoms in air were computed from the measured diffusion coefficients. All obtained results were compared with values, calculated from theory.     

Diffusion of sulfur in nickel oxide single crystals

The diffusion of sulfur in nickel oxide single crystals has been investigated over the temperature range from 1000 to 1250°C. The measured data were found to deviate markedly from the error function complement dependence for diffusion from a constant source. The deviation is attributed to the migration of sulfur by the “double mode simultaneous diffusion mechanism.” The faster mode diffusion is suggested to be via nickel vacancies, and the slower mode diffusion is suggested to be via oxygen vacancies. The diffusivities for faster mode are given by D_f = 2.94 exp[? 86.6 kcal/RT] cm² sec^?1 and, the slower mode, D_s = 1.08 × 10^?9 exp [?32.8 kcal/RT]cm²sec^?1.     

Exchange of injected hydrogen isotopes between diffusing and trapped states in Al

Abstract

Exchange of hydrogen isotopes between diffusing and trapped populations was found with successive injections of 25 keV D₂ ⁺ and 100 or 140 keV H₂ ⁺ into Al surface by simultaneously detecting elastically recoilled hydrogen and deuterium using 2 MeV He⁺.

When backward diffusion of injected hydrogen toward surface was supposed to be impeded or by-passed by structural changes in the subsurface layer due to ion bombardment, effective replacement cross-section of about 1.4 × 10^?18 cm² was observed. Otherwise, namely when the hydrogen backward diffusion is supposed to be rather free, the effective cross section of about 7.8 × 10^?18 was observed.

Due to the difference in energy of the first and second injections, this phenomenon is different from that so called “isotopic exchange”, which occurs through collisional process.     

Infrared Spectra Interpretations of Clay-Adsorbed Water in Relation to the “Anomalous” Water Controversy

Abstract

The nature of surface adsorbed water has been the subject of countless investigations. Much of the discussion has centered around the degree and strength of H-bonding to surface groups and between adjacent water molecules.^1,2 Water condensed into glass or quartz capillaries sometimes has unusual properties. This unusual water has been referred to as “orthowater,”³ “anomalous water,”^4,5,6 and “polywater”^7,8 and was thought by some to be polymers of water formed by specific surface catalysis.^1–3 Several possible structures of “polywater” have been suggested which require formation of symmetrical or very strong H-bonds between water molecules.^4,6,7 Infrared spectra of polywater have been presented^7,8 and the strongest absorption band which appeared at 1595 cm^?1 was assigned to the symmetric O-H-O bond. However, more recent investigations suggest that the observed polywater bands may actually be SO₄ ^2-, -COOH^?, or HCO₃ ^? bands, impurities collected by surface diffusion,⁹ or bands of a HNO₃ solution formed by corona discharge.¹⁰ Other observers^11,12 suggest that polywater may be a hydrosol formed by surface contaminates.     

The intercalation/deintercalation kinetic studies on the structure-integrated cathode material 0.5Li2MnO3 0.5LiNi0.5Mn0.5O2

A cathode material, 0.5Li₂MnO₃ 0.5LiNi_0.5Mn_0.5O₂, was prepared by citric acid-assisted sol–gel method and its electrochemical performance was investigated. It delivered a charge capacity of 270 mAh g^?1 and a discharge capacity of 189 mAh g^?1 in the first cycle. With the increase of current density from 14 to 28 mA g^?1, the discharge capacity dropped severely to 130 mA g^?1. Obviously, the rate capability of the material was inferior to most of the oxide cathode materials. The diffusion coefficient of this material was calculated to be 6.04?×?10^?12 cm² s^?1 from the results of cyclic voltammetry measurements. Moreover, diffusion coefficients between 3.13?×?10^?12 and 1.22?×?10^?10 cm² s^?1 in the voltage range of 3.8–4.7 V were obtained by capacity intermittent titration technique. This, together with the localized Li₂MnO₃ domains in the crystal structure, may validate the poor rate capability.     

Molecular constants of SiF4, GeF4, and RuO4: An improvement of the analysis of the ir-band contours of ν3(F2) by low temperature measurements and by using isotopically pure compounds

The ir-band contour of ν₃(F₂) of gaseous SiF₄, GeF₄, and RuO₄ have been analyzed making use of isotope substitution techniques, low temperature measurements, and matrix isolation spectroscopy. In the case of RuO₄ values for the hot band progression ν₃ + nν₄ ? nν₄ (X₃₄ = ?1.1 ± 0.1 cm^?1 for ⁹⁹RuO₄ and ¹⁰⁴RuO₄) have been obtained and F₂ block force constants have been calculated using isotope shifts Δω₃ and ζ₃ constants as additional data.     

Synthesis,Characterization, DNA Binding Studies,Photocleavage, Cytotoxicity and Docking Studies of Ruthenium(II) Light Switch Complexes

A new ligand 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2yl)phenylboronic acid and its (IPPBA) three ruthenium(II) complexes [Ru(phen)₂(IPPBA)](ClO₄)₂ (1), [Ru(bpy)₂(IPPBA)](ClO₄)₂ (2) and [Ru(dmb)₂(IPPBA)](ClO₄)₂ (3) have been synthesized and characterized by elemental analysis, UV/VIS, IR, ¹H-NMR,¹³C-NMR and mass spectra. The binding behaviors of the three complexes to calf thymus DNA were investigated by absorption spectra, emission spectroscopy, viscosity measurements, thermal denaturation and photoactivated cleavage. The DNA-binding constants for complexes 1, 2 and 3 have been determined to be 7.9?×?10⁵ M^?1, 6.7?×?10⁵ M^?1 and 2.9?×?10⁵ M^?1. The results suggest that these complexes bound to double-stranded DNA in an intercalation mode. Upon irradiation at 365 nm, three ruthenium complexes were found to promote the cleavage of plasmid pBR322 DNA from super coiled form ? to nicked form ??. Further in the presence of Co²⁺, the emission of DNA–Ru(ΙΙ) complexes can be quenched. And when EDTA was added, the emission was recovered. The experimental results show that all three complexes exhibited the “on–off–on” properties of molecular “light switch”. The highest Cytotoxicity potential of the complex1 was observed on the Human alveolar adenocarcinoma (A549) cell line. Good agreement was generally found between the spectroscopic techniques and molecular docked model which provides further evidence of groove binding.     

The influence of the activator concentration on electroluminescence properties of thin layers in a system ZnS: Cu,Mn, Cl

The influence of activators, especially copper, on the electric properties of vacuum-evaporated electroluminescent layers excited by dc voltage is investigated. In the course of the “one step” method of preparation, non-uniform incorporation of the activators occurs. The layers are divided into three groups according to the copper concentration. 1 — “low” (1×10^?3 g Cu/g ZnS) with the emission stimulated at Al^? electrode, 2 — “medium” (5–8×10^?3 g Cu/g ZnS) with the emission at both polarities, 3 — “high” (9×10^?3?5×10^?2 g Cu/g ZnS) with the emission at Al⁺ electrode. Layers in these groups differ not only in their electrical properties and in the existence of the forming process but they have also various distribution of the light-emitting regions. The light emission has been found in the intermediate regions between the microcrystalline grains as well as on the interface between the microcrystalline grain and ZnS phosphor phase. According to structural properties the light emission originates from microcrystalline grains too.     

Isotopeneffekt in der paraelastischen relaxation

The kinetics of the reorientation of the molecular impurities¹⁶O₂ ^? and¹⁸O₂ ^? in the host lattices KCl, KBr and KJ has been investigated by means of ESR as a function of uniaxial stress in the temperature range between 1,3°K and 4,5°K. Below 4°K the reorientation rate is proportional to the temperature, indicating that one-phonon processes dominate at low temperatures. ForT>4°K the reorientation through excited librational levels becomes significant. The large isotope effect in the reorientation rate of¹⁶O₂ ^? and¹⁸O₂ ^? confirms that tunneling plays an important role. The analogy between the diffusion of polarons and the reorientation of molecules in solids is discussed in detail. The evaluation and interpretation of the experimental results in terms of the theory of Gosar and Pire yields values for the tunneling matrix elements, the potential barrier between two equilibrium orientations, the libration frequencies and an effective moment of inertia. The theory accounts well for the contribution of the one-phonon processes to the relaxation rate for stress along [001]. For stress along [111] the agreement is only qualitative.     

Effect of the deviation from stoichiometry on cation self-diffusion and isotope effect in wüstite,Fe1−xO

Diffusion of ⁵⁹Fe in Fe_1xO crystals has been measured by a serial-sectioning technique as a function of temperature and deviation from stoichiometry. The results indicate that the diffusivity increases slightly at 1200°C, decreases at 802°C with an increase in x, and is insensitive to change in x at 1003°C. The temperature dependence of the cation diffusivity in Fe_0.94O is given by the expression, $\text{D=(0.6±0.5)×10}{}^{\mathrm{?3}}\text{exp(?29350 ±}\text{300}\text{RT}\text{)cm}{}^2\text{/se}$ the temperature range 700–1340°C. The isotope effect for cation self-diffusion was measured by simultaneous diffusion of ⁵²Fe and ⁵⁹Fe in Fe_1?xO at various temperatures and values of x. Although the measured values of fΔK are independent of temperature within the limits of experimental error, they decrease with an increase in the deviation from stoichiometry. The experimental results appeared to be consistent with the diffusion of Fe ions via “free mobile vacancies” that coexist with defect clusters. As a consequence of a “site-blocking” effect, the mobility of “free mobile vacancies” and the apparent correlation factor for cation tracer diffusion decrease with an increase in deviation from stoichiometry.     

Thermodynamic properties of successive phase transitions in Rb2ZnBr4

Heat capacity measurements have given the following transition temperatures and entropies: 0.027 J K^?1mol^?1 at 76.5 K, 0.47 J K^?1mol^?1 at 111.7 K, and 0.048 J K^?1mol^?1 at 193.6 K. These are interpreted as “lock-in”, soft-mode, and “lock-in” transitions, respectively, from comparison with analogous results for Rb₂ZnCl₄ and K₂SeO₄. The N-IC transition was located at 347 K by DTA.     

Perylene Diimide Appended with 8-Hydroxyquinoline for Ratiometric Detection of Cu2+ Ions and Metal Displacement Driven “Turn on” Cyanide Sensing

Perylene diimide (PDI) 3 and 4 appended with 8-hydroxyquinoline derivatives have been synthesized and their photophysical and spectroscopic properties have been experimentally determined. Moreover, PDIs 3 and 4 show ratiometric behavior to detect Cu²⁺ colorimetrically with visible color change from coral red to light pink, whereas 3 and 4 show “turn-off” behavior in fluorescence with lowest limit of detection 5?×?10^?7 M. The PDI 3 could be further utilized for ratiometric CN^? detection colorimetrically and as “turn-on” sensor for CN^? detection fluorometrically with lowest limit of detection 8?×?10^?6 M. The comparison of spectroscopic properties of PDI 1-4 highlights the importance of linking 8-hydroxyquinoline units on the PDI core at bay position for achieving Cu²⁺ recognition event into ratiometric signal.

A simultaneous analysis of the microwave,submillimeterwave, far infrared,and infrared-microwave two-photon transitions between the ground and ν2 inversion-rotation levels of 14NH3

Fourier transform infrared spectra of the inversion-rotation transitions have been measured with 0.010-cm^?1 resolution between 40 and 300 cm^?1 in the ground state and ν₂ excited states of ¹⁴NH₃. Submillimeterwave spectra of the inversion and inversion-rotation transitions in the ν₂ state of ¹⁴NH₃, including a few Δk = ±3 “perturbation-allowed” transitions, have been measured with microwave accuracy between 540 and 770 GHz. A simultaneous least-squares analysis of these data, the microwave ground-state transition frequencies, and the ν₂ infrared-microwave two-photon transition frequencies has been carried out. A theory of the Δk = ±3n interactions in the ground and ν₂ excited states of ammonia (S. P. Belov, L. I. Gershtein, A. F. Krupnov, A. V. Maslovskij, ?. Urban, V. ?pirko, and D. Papou?ek, J. Mol. Spectrosc.84, 288–304 (1980)) has been used in the analysis. A set of the ground- and ν₂-state molecular parameters has been obtained which describes the experimental data within the precision of the experiment. The “smoothed” values of transition frequencies can be used for calibration purposes with a precision better than 3 × 10^?5 cm^?1 in the submillimeterwave region, better than 10^?3 cm^?1 in the far-infrared region, and better than 1.5 × 10^?3 cm^?1 in the region 700 – 1200 cm^?1.     

Trinuclear Gd(III) Metal Complex with Amide Core Display Remarkable Enhancement in Relaxivity

New trinuclear gadolinium(III) complex having 2-bromoisovaleric acid pendant arm is reported. The longitudinal relaxivity (r _1p) of the complex is 23.17 mM^?1 s^?1 which correspond to a “per Gd” relaxivity of 7.72 mM^?1 s^?1. The transverse relaxivity (r _2p) of the complex is 24.79 mM^?1 s^?1 which correspond to a “per Gd” value of 8.26. The complex exhibit r _1p and r _2p values of 29.19 and 35.20, respectively, in the presence of HSA. The complex also shows pH dependant relaxivity which is an added advantage of the complex for utilization in cancer cell magnetic resonance imaging. The higher relaxivity values in water and HSA indicates a compact solution structure for the complexes and a restricted internal motion about the amide spacer.     

Diffusion of 55Fe in Fe2O3 single crystals

The diffusion of ⁵⁵Fe has been measured parallel to the c axis of Fe₂O₃ single crystals at temperatures in the range 708–1303°C and at an oxygen activity of unity. The tracer penetration profiles were determined using sectioning techniques. For temperatures above 900°C the tracer diffusion coefficient is given byD¹(Fe) = 1.6 × 10⁹ exp[?6.0 (eV)/kT] cm² s^?1 and below 900°C by 2.8 × 10^?9 exp[?1.8 (eV)kT]. The high-temperature behaviour is probably characteristic of pure Fe₂O₃, whereas diffusion at lower temperatures may be influenced by impurities. The most likely defects responsible for diffusion of Fe are iron interstitials and, for oxygen, oxygen vacancies, and the observed activation energies are discussed in terms of the properties of these defects. The diffusion data and defect models have been used to predict the rate of growth of Fe₂O₃ and indicate that outward Fe diffusion is the dominant transport process. Previously published data for Fe₂O₃ growth in a variety of experimental situations have been corrected to a single rate constant using a model for multilayer growth. The corrected data are all in good agreement but are approximately two orders of magnitude greater than predicted from diffusion data, which suggests that grain boundary diffusion controls the growth of Fe₂O₃ in practice.     

Desorption kinetics and directional dependence of the surface diffusion of potassium on stepped W(100) surfaces

Using a surface ionisation ion microscope the desorption parameters and the diffusion constant of potassium were measured on stepped W(100) surfaces. The activation energy of ionic desorption as well as the corresponding prefactor do not depend on the step density; the mean adsorption lifetime τ can be expressed as τ=1.6×10^?14s exp(2.44 eV/kT).Whereas the surface diffusion of potassium on “flat” W(100) and on W(S)-[9(100)×(110)] was found to be isotropic, on W(S)- [5(100)×(110)] and W(S)-[3(100)×(110)] it occurs preferentially parallel to the step direction. The diffusion constant D_∥ for this direction has roughly the same value for all investigated surfaces: D_∥=7.8×10^?2 cm²s^?1 exp(?0.42 eV/kT). For the direction perpendicular to the steps D⊥ depends on the step density, whereby the activation energy as well as the prefactor increase with increasing step density.     

Effect of doping functionalized MWCNTs on the electrochemical performances of Li<Subscript>2</Subscript>CoSiO<Subscript>4</Subscript> for lithium-ion batteries

We report the synthesis of Li₂CoSiO₄ by the sol-gel method and the preparation of a composite electrode by incorporating functionalized multi-walled carbon nanotubes (fn. MWCNTs) as conductive additive. XRD pattern of the composite confirms the structural stability of Li₂CoSiO₄ even after the addition of fn. MWCNTs. SEM images of the composite reveal the presence of conductive bridges formed by MWCNTs between the submicron-sized particles of Li₂CoSiO₄. The cyclic voltammograms of the composite cathode show redox peaks with higher current density than pure Li₂CoSiO₄ and the current density increases with increase in sweep rate. The diffusion coefficient of lithium has been improved by the addition of fn. MWCNTs from 1 × 10^?14 to 8 × 10^?14 cm²/s as calculated using Randles-Sevcik equation. The charge-discharge cycling performance of both pure Li₂CoSiO₄ and composite cathode has been discussed.     

An appraisal of the molecular model for the vk centre

The V_k centre in halide crystals is often described in terms of an X₂^? molecule ion. Recent molecular calculations for the halogen molecule negative ions have enabled a detailed comparison to be made between the theoretical anion and the results from optical and spin resonance studies on the crystals. The optical absorption line widths are naturally dependant on the host lattice, but the excitation energies and spin resonance constants may be readily interpreted in terms of the molecule. Certain anomalies in the spin resonance data for the heteronuclear defects, in particular ClI^? and BrI^?, show that the simple wavefunction constructed from “s” and “p” atomic orbitals does not adequately describe the polarisation of the large halogen atoms, and a more flexible wavefunction will be needed to calculate the spin resonance constants for these ions.