Detailed Description of Pulse Isotopic Exchange Method for Analyzing Oxygen Surface Exchange Behavior on Oxide Ion Conductors

A novel pulse ¹⁸O-¹⁶O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor loaded with the oxide powder. The isothermal response to an ¹⁸O-enriched pulse passing through the reactor, thereby maintaining chemical equilibrium, is measured by on-line mass spectrometry. Evaluation of the apparent exchange rate follows from the uptake of ¹⁸O by the oxide at given reactor residence time and surface area available for exchange. The developed PIE technique is rapid, simple and highly suitable for screening and systematic studies. No rapid heating/quenching steps are required to facilitate ¹⁸O tracer anneal or analysis, as in other commonly used techniques based upon oxygen isotopic exchange. Moreover, the relative distribution of the oxygen isotopologues ¹⁸O₂, ¹⁶O¹⁸O, and ¹⁶O₂ in the effluent pulse provides insight into the mechanism of the oxygen exchange reaction. The PIE technique has been demonstrated by measuring the exchange rate of selected oxides with enhanced oxide ionic conductivity in the range of 350?900 oC. Analysis of the experimental data in terms of a model with two consecutive, lumped steps for the isotopic exchange reaction shows that for mixed conductors Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ(BSCF) and La₂NiO_4+δ the reaction is limited by the apparent rate of dissociative adsorption of O₂ molecules at the oxide surface. For yttria-stabilized zirconia (YSZ), a change-over takes place, from rate-limitations by oxygen incorporation below ∽800 oC to rate-limitations by O₂ dissociative adsorption above this temperature. Good agreement is obtained with exchange rates reported for these materials in literature.     

Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration

This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na₂SO₄, Na₂CO₃, and Na₂SiO₃) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH₃, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. Na₂SO₄ induces cracking in the ≥28-d pastes due to post-hardening gypsum and ettringite formation from the excess SO₄^2– present. Anhydrite dissolves more rapidly in the presence of Na₂CO₃, prompting carbonation. Na₂SiO₃ raises compressive strength and exhibits strätlingite as one of its reaction products.     

Kinetics of Heterogeneous Isotopic Exchange Reaction in Finite Bath

A general method to find the rate constant and particle self-diffusion coefficient is suggested for a heterogeneous isotopic exchange reaction which is controlled by surface mass reaction or controlled by a combination of surface mass reaction and intraparticle diffusion. The values of the kinetic parameter, ξ₁ (ratio of the forward surface mass reaction rate to the intraparticle diffusion rate), particle self-diffusion coefficient D and rate constant k are obtained by the proposed method for the isotopic exchange reaction systems CaCO₃(s)/Ca²⁺(aq) and CaC₂O₄(s)/Ca²⁺(aq).     

Reconsideration on Hydration of Sodium Ion: From Micro-Hydration to Bulk Hydration

Micro hydration structures of the sodium ion, [Na(H₂O) _n ]+, n = 1–12, were probed by density functional theory (DFT) at B3LYP/aug-cc-pVDZ level in both gaseous and aqueous phase. The predicted equilibrium sodium–oxygen distance of 0.240 nm at the present level of theory. The four-, five- and six-coordinated cluster can transform from each other at the ambient condition. The analysis of the successive water binding energy and natural charge population (NBO) on Na⁺ clearly shows that the influence of Na⁺ on the surrounding water molecules goes beyond the first hydration shell with the hydration number of 6. The Car-Parrinello molecular dynamic simulation shows that only the first hydration sphere can be found, and the hydration number of Na⁺ is 5.2 and the hydration distance (r_Na–O) is 0.235 nm. All our simulations mentioned in the present paper show an excellent agreement with the diffraction result from X-ray scattering study.     

Kinetic study of the isotopic exchange of Na+ and Zn2+ ions on iron and chromium titanates

Iron(III) (FeTi) and chromium (III) titanates (CrTi) were prepared as cation exchange materials in a granular form. The rate of the isotopic exchange of Na⁺/*Na⁺ and Zn²⁺/*Zn²⁺ between aqueous solution and iron(III) and chromium(III) titanates in Na⁺ or Zn²⁺form has been carried out radiometrically in the 25-60 °C temperature range. The exchange rate is controlled by a particle diffusion mechanism and experimental and theoretical approaches have been used to obtain the rate of diffusion through the spherical particles of the exchangers. The values of self diffusion () of Na⁺ and Zn²⁺ ions were measured at different operation conditions, particle size, reaction temperatures and drying temperatures of the matrix. The values of kinetic and thermodynamic parameters were calculated and their significance discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dry state preparation of radioiodine labeled meta-iodobenzylguanidine

Radioiodination of meta-iodobenzylguanidine (MIBG) by the isotopic exchange technique in the dry state has been performed. Benzoic acid, pivalic acid and acetamide have been used as molten protic media to promote isotopic exchange reactions. Ammonium sulphate, diammonium hydrogen ortho-phosphate and ammonium chloride were used as catalysts which provide acidic media to facilitate exchange reactions. Maximum radiochemical yields of 97.1±1.3% and 84.3±1.6% [¹³¹I] MIBG were obtained when ammonium sulphate and benzoic acid were used. High radiochemical yields of 88.3±1.1% and 74.4±1.5% [¹³¹I] MIBG were also obtained in case of diammonium hydrogen orthophosphate and pivalic acid which suggests their successful use as reaction media in the radioiodination of MIBG. The activation energy for the exchange reaction in ammonium sulphate was calculated to be 10.8 kcal/mole.     

The effect of sodium cation concentration on the electrochemical reduction of copper(I) thiosulfate complexes

The electrochemical behavior of copper(I) thiosulfate complexes from aqueous solutions containing different amounts of sodium perchlorate NaClO₄ is studied by the methods of hydrodynamic voltammetry and potentiometry with a Na⁺-selective electrode. The electrochemical reaction orders p with respect to Na⁺ cations are determined from the dependences of exchange currents and direct reaction currents at fixed potential on the equilibrium concentration of Na⁺ cations. The reaction order p is close to 1 in the Na⁺ concentration range of 0.06–0.12 M and drops to zero for $c_{Na^ + } $ > 0.12 M. The ion pair (IP) {Na[Cu(S₂O₃)₂]}_2? the formation of which precedes the electron transfer reaction is the electrochemically active species for the reduction of copper(I) thiosulfate complexes. The stability constant of IP is determined (K = 27.0 ± 2.4) as well as the rate constants of IP formation and decomposition.     

Bulk properties and hydration numbers of components of water–salt,water–urea,and water–urea–salt systems

With an increase in the concentration of additives, the hydration numbers of compounds decrease. Thus, in a saturated 54.6% solution, urea loses approximately 3/4 of the initial amount of water, forming an aquacomplex of the composition (NH₂)₂CO?H₂O. In a supersaturated 44% solution, the sodium chloride aquacomplex is dehydrated by 2/3, and in a supersaturated 67% solution, sodium sulfate is dehydrated by 5/6. The density of these solutions is 1.354÷1.360 g/cm³ (44% NaCl) and 1.800÷1.849 g/cm³ (67% Na₂SO₄). In a saturated urea solution, NaNO₃, NaCl, and Na₂SO₄ complexes lose 53÷55% of hydration water. It is shown that the interactions in the binary water–urea system somewhat increase the hydration number of the salts (structural hydration). The hydration water density, a structurally important characteristic, increases in the series of solutions of urea, NaNO₃, NaCl, and Na₂SO₄. In the same series of additives, the excess volume of binary water–urea and water–salt systems becomes more negative.     

LiZr4(PO4)3的Na/Li及Ag/Li离子交换

研究了LiZr2(PO4)3在水溶液中的Na/Li和Ag/Li离子交换行为.结果表明,LiZr2(PO4)3对Na+和Ag+离子均具有很高的选择性,且对Ag+的选择性高于Na+.LiZr2(PO4)3与Ag+的离子交换反应是通过形成固溶体的形式进行的,而与Na+的离子交换反应则是通过置换进行的.温度升高有利于提高LiZr2(PO4)3上Na/Li和Ag/Li的离子交换反应速度.     

Water transference through nickel hydroxide precipitate membrane

The transference of water that results from ion migration through the nickel hydroxide precipitate membrane was studied in chloride, perchlorate, nitrate, and sulphate solutions to estimate the transference number of water and the co-ion transport. In the systems of univalent anions, the moles of water transported per mole of electrons in 0.1 N solutions is almost identical to the hydration number of each anion. This water flow decreases gradually as the concentration of external solution increases, because of increase in the co-ion (cation) transport with increasing concentration of the solution. In the system of sulphate solutions the co-ion transport is remarkable, the transport number of Na⁺ ions being 0.03 in 0.01 N, 0.27 in 0.10 N, and 0.50 in 0.5 N Na₂SO₄ solution. This large co-ion transport in Na₂SO₄ solution is attributed to the partical replacement of hydroxyl groups on the membrane by SO^2?₄ ions, which then acts as a negative fixed charge. The order of the selectivity for co-ion transport is K⁺ > Na⁺ > Li⁺ > Ni²⁺ ? Mg²⁺ in sulphate solutions and also in chloride solutions, although the transport number of the cations is much smaller in chloride solution than in sulphate solution.     

Heats of adsorption of water on vermiculite having large singly-charged cations in the exchange complex

The isotherms and differential heats of adsorption of water vapor on K-, NH₄-, Rb-, and Cs-vermiculites have been studied by means of a Calvet microcalorimeter having a microweighing adsorption attachment. The results are interpreted taking into account that the large cations K₊, NH₄ ⁺, Rb⁺, and especially Cs⁺, may not replace the initial exchange complexes (Na⁺ or Mg²⁺) of the mineral completely, so that besides hydration of the principal exchange cations the reaction of water molecules being adsorbed with the residual Na⁺ or Mg⁺ cations also takes place. The presence of a certain number of the initial cations (Na⁺ or Mg²⁺) in the Cs form of vermiculite is confirmed by the results of studying the ion exchange equilibria on the Na and natural (Mg) forms of the mineral involving the participation of the Cs₊ ions. The nature of the variation in the dependence of the differential heats of adsorption with an increase in the amount of adsorbed substance indicates the segregation (isolation) of the principal (K⁺, NH₄ ⁺, Rb⁺, Cs⁺) and the residual (Na⁺, Mg²⁺) exchange cation in the structure of the mineral.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 1, pp. 91–96, January–February, 1986.     

Realizing Complete Solid‐Solution Reaction in High Sodium Content P2‐Type Cathode for High‐Performance Sodium‐Ion Batteries

P2‐type layered oxides suffer from an ordered Na⁺/vacancy arrangement and P2→O2/OP4 phase transitions, leading them to exhibit multiple voltage plateaus upon Na⁺ extraction/insertion. The deficient sodium in the P2‐type cathode easily induces the bad structural stability at deep desodiation states and limited reversible capacity during Na⁺ de/insertion. These drawbacks cause poor rate capability and fast capacity decay in most P2‐type layered oxides. To address these challenges, a novel high sodium content (0.85) and plateau‐free P2‐type cathode‐Na_0.85Li_0.12Ni_0.22Mn_0.66O₂ (P2‐NLNMO) was developed. The complete solid‐solution reaction over a wide voltage range ensures both fast Na⁺ mobility (10^?11 to 10^?10 cm² s^?1) and small volume variation (1.7 %). The high sodium content P2‐NLNMO exhibits a higher reversible capacity of 123.4 mA h g^?1, superior rate capability of 79.3 mA h g^?1 at 20 C, and 85.4 % capacity retention after 500 cycles at 5 C. The sufficient Na and complete solid‐solution reaction are critical to realizing high‐performance P2‐type cathodes for sodium‐ion batteries.     

Aluminum phosphate dispersed on a cellulose acetate fiber surface: Preparation, characterization and application for Li, Na and K separation

Cellulose acetate fibers with supported highly dispersed aluminum phosphate were prepared by reacting aluminum-containing cellulose acetate (Al₂O₃=3.5 wt.%; 1.1 mmol g⁻¹ aluminum atom per gram of the material) with phosphoric acid. Solid-state NMR spectra (CPMAS ³¹P NMR) data indicated that HPO₄²⁻ is the species present on the fiber surface. The specific concentration of acidic centers, determined by ammonia gas adsorption, is 0.50 mmol g⁻¹. The ion exchange capacities for Li⁺, Na⁺ and K⁺ ions were determined from ion exchange isotherms at 298 K and showed the following values (in mmol g⁻¹): Li⁺=0.03, Na⁺=0.44 and K⁺=0.50. The H⁺/Li⁺ exchange corresponds to the model of the ideal ion exchange with a small value of the corresponding equilibrium constant K=1.1×10⁻². Due to the strong cooperative effect, the H⁺/Na⁺ and H⁺/K⁺ ion exchange is non-ideal. These ion exchange equilibria were treated with the use of models of fixed bi- or tridentate centers, which consider the surface of the sorbent as an assemblage of polyfunctional sorption centers. Both the observed ion exchange capacities with respect to the alkaline metal ions and the equilibrium constants were discussed by taking into consideration the sequence of the ionic hydration radii for Li⁺, Na⁺ and K⁺. The matrix affinity order for the ions decreases as the hydration radii of the cations increase, i.e. Li⁺>Na⁺>K⁺. The high values of the separation factors S_Na⁺/Li⁺ and S_K⁺/Li⁺ (up to several hundred) provide quantitative separation of Na⁺ and K⁺ from Li⁺ from a mixture containing these three ions.     

Effect of the Nature of a Sodium-Conducting Solid Electrolyte on the Impedance of Its Interface with the SmCo0.8Ti0.2O3 Oxide Electrode in an Oxygen Atmosphere

Impedance spectroscopy is employed for studying the behavior of the interface of the SmCo_0.8Ti_0.2O₃ semiconducting oxide electrode with a sodium-conducting solid electrolyte (Na⁺–SE) in atmospheres of argon and oxygen. Compounds with the susceptibility to hydration decreasing in the row Na₅TbSi₄O₁₂ Na₃Zr₂Si₂PO₁₂ Na₃Sc₂(PO₄)₃ are used as the Na⁺–SE. Only the systems containing the Na₅TbSi₄O₁₂ solid electrolyte, the grain surfaces of which acquire boundary layers formed by hydration products, are sensitive to oxygen. The exchange current of the electrode reaction O₂ (g) + e O₂ ^– increases from 1.8 to 19 mA/cm² in the temperature interval 250–300°C. The systems with Na⁺–SE that are not prone to hydration remain inactive in the oxygen atmosphere probably due to quick blocking of the active centers by nonconducting products of the secondary chemical reaction Na⁺ + O₂ ^– NaO₂.     

Realizing Complete Solid-Solution Reaction in High Sodium Content P2-Type Cathode for High-Performance Sodium-Ion Batteries

P2-type layered oxides suffer from an ordered Na⁺/vacancy arrangement and P2→O2/OP4 phase transitions, leading them to exhibit multiple voltage plateaus upon Na⁺ extraction/insertion. The deficient sodium in the P2-type cathode easily induces the bad structural stability at deep desodiation states and limited reversible capacity during Na⁺ de/insertion. These drawbacks cause poor rate capability and fast capacity decay in most P2-type layered oxides. To address these challenges, a novel high sodium content (0.85) and plateau-free P2-type cathode-Na_0.85Li_0.12Ni_0.22Mn_0.66O₂ (P2-NLNMO) was developed. The complete solid-solution reaction over a wide voltage range ensures both fast Na⁺ mobility (10⁻¹¹ to 10⁻¹⁰ cm² s⁻¹) and small volume variation (1.7 %). The high sodium content P2-NLNMO exhibits a higher reversible capacity of 123.4 mA h g⁻¹, superior rate capability of 79.3 mA h g⁻¹ at 20 C, and 85.4 % capacity retention after 500 cycles at 5 C. The sufficient Na and complete solid-solution reaction are critical to realizing high-performance P2-type cathodes for sodium-ion batteries.     

Single Crystalline Na0.7MnO2 Nanoplates as Cathode Materials for Sodium‐Ion Batteries with Enhanced Performance

Single crystalline rhombus‐shaped Na_0.7MnO₂ nanoplates have been synthesized by a hydrothermal method. TEM and HRTEM analyses revealed that the Na_0.7MnO₂ single crystals predominantly exposed their (100) crystal plane, which is active for Na⁺‐ion insertion and extraction. When applied as cathode materials for sodium‐ion batteries, Na_0.7MnO₂ nanoplates exhibited a high reversible capacity of 163 mA h g^?1, a satisfactory cyclability, and a high rate performance. The enhanced electrochemical performance could be ascribed to the predominantly exposed active (100) facet, which could facilitate fast Na⁺‐ion insertion/extraction during the discharge and charge process.     

Die Selektivität Kristalliner Cer(IV)-Phosphatsulfathydrate gegenüber Li+, Na+, K+, Rb+, Cs+ und NH in absolutem Methanol und absolutem Dimethylsulfoxid

Selectivity of Crystalline Ce^IV Phosphate Sulphate Hydrates for Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and NH in Absolute Methanol and Absolute Dimethylsulphoxide The sequence of exchange capacities of Cerium(IV) phosphate sulphate hydrate (CePO₄)₂(HPO₄)_0.74(SO₄)_0.26 · 4,74 H₂O for alkalimetal ions and ammoniumions in absolute methanol at 25°C for the case of a small excess of the exchanger (in relation to the equivalent amount) is given by K⁺ > Rb⁺ ≥ NH₄⁺ > Cs⁺ > Na⁺ > Li⁺. Between the exchange capacity A of these cations and their ionic radii r (given by Ladd) exists the simple relation A = const./r. For Na⁺ the radius of the inner hydration shell must be considered. In absolute dimethyl-sulphoxide under the same conditions the sequence is K⁺ ≥ NH₄ > Rb⁺ > Na⁺ > Cs⁺ > Li⁺. For K⁺, NH₄, Rb⁺ and Cs⁺ the exchange capacity is given by A = const./r + const. · r⁴. The sequences of the alkali ions in both solvents are among the group of 13 sequences which are physicaly significant according to EISENMANNS 's theory. The results are compared with the observations made with water as solvent.     

Synthesis and sorption properties of new synthesized rare-earth-doped sodium titanate

A series of rare-earth-doped sodium titanates with the chemical formula R _x H _y Na_{4 − (x+y)}TiO₄·nH₂O (where R = Ce³⁺, Nd³⁺ and Sm³⁺) were grown employing solid-state fusion reaction technique. The physico-chemical investigations indicated that the new materials were self engineered into large particles enough to be used in sorption process and having crystalline structures containing localized Na⁺ ions. Equilibrium studies revealed that an enhancement in sorption efficiency of sodium titanate after rare-earth doping. The neodymium-rich sodium titanate exhibited a better exchange affinity for Cs⁺ compared to the other studied series. Data on the kinetics of cesium exchange fit well to pseudo-second order and intra-particle diffusion models. In a separate experiment, it was reported that the R-HNaTi series showed responsible sorption affinity toward Ce, Nd and Sm ions in their solution mixture with insignificant selectivity trend which reflects the high stability of titanate matrices.     

Radiolabeling of 1-[N',N'-bis(2-chloroethyl)-4-aminophenyl]-N-methyl-fullereno-C60-[1,9-c]pyrrolidine with 125I

Summary A procedure for labeling of a fullerene derivative 1-[N',N'-bis(2-chloroethyl)-4-aminophenyl]-N-methyl-fullereno-C₆₀-[1,9-c]pyrrolidine (C₆₀-C₁₃H₁₈N₂Cl₂) with ¹²⁵I is reported. The compound was first iodinated with a large excess of iodine monochloride and then radiolabeled by isotopic exchange with Na¹²⁵I in a toluene-water two-phase system. The dependence of the radiolabeling yield on the reaction temperature and exchange time was examined. The radiolabeling yield of the compound was as high as 94% after heating for 2 hours at 130 °C.     

Structural and dynamic investigations of aqueous clusters of Na+ and K+

Using computer modeling, we have studied Na⁺–24H₂O and K⁺–24H₂O clusters. We propose ion-water interaction potentials. We obtain structural, energy, and dynamic characteristics of the studied clusters. We show different mechanisms for exchange of water molecules surrounding the Na⁺ and K⁺ ions: single-particle in the case of Na⁺, and close to K⁺, along with single-particle exchange, a large percentage of multiparticle cooperative exchange of water molecules. This difference is explained by the different degrees of orientation of the water molecules surrounding these ions, by the presence of a unified deformed network of H bonds in the K⁺ cluster and its absence in the Na⁺ cluster. We propose a negative hydration mechanism for the K⁺ ion.Institute of General and Inorganic Chemistry, Russian Academy of Sciences. Institute of Physical Chemistry, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 96–104, March–April, 1993.