The effect of Cs ions on codeposition of SiC particles with nickel

Electrodeposition of SiC particles (technical powder) with nickel matrix in the presence of cesium ions (0–37.6 mM) was investigated. The influence of Cs⁺ concentration on cathodic polarization curves was determined in galvanostatic and potentiodynamic measurements. The presence of Cs⁺ in the solution enhanced in some extent adsorption of Ni²⁺ ions on SiC, but preferential cesium adsorption occurred simultaneously. The last phenomenon resulted in cesium incorporation in the composite coating. The particle content in the deposits (16–24 vol%) was governed by the amount of nickel ions adsorbed on SiC. Structure of the composite coatings was studied by microscopic observations. At highest Cs⁺ concentrations, incorporation of small SiC grains was inhibited. Microhardness of deposits (390–800 HV) was directly dependent on the SiC content in the coatings.     

Thermodynamic and transport properties of cesium vapors on binodal and in its vicinity

To check the earlier proposed hypothesis on the considerable cluster effect and the ion-atom nonideality in saturated cesium vapors, a chemical model is proposed that accounts for the presence of neutral, positively, and negatively charged small-sized cluster ions and the main types of interatomic interactions. The partition sums of atoms, ions, and clusters are calculated as are the composition and pressure of cesium vapors on the binodal. It is shown that, on the saturation line, cesium vapor in the near-critical region consists mainly of atoms and a small admixture of molecules, whereas the charged component consists predominantly of Cs^?, Cs ₃ ⁺ , and Cs ₂ ⁺ ions whose amount is considerably lower than the amount of atoms. Interactions between charged particles and between the charged and neutral ones significantly influence the charge composition of vapors and weakly affect the equation of state and the composition of neutral component of vapors. The calculated compressibility and conductivity of the cesium vapor plasma are in good agreement with the experimental data for the near-critical isobars.     

X-ray photoemission studies of cesium antimonide photoemitters

X-ray photoemission spectra (XPS) of cesium antimonide photosurfaces prepared in ultrahigh vacuum on Pyrex, Suprasil quartz and stainless steel substrates were measured. A comparison of the XPS data for xenon gas, which is isoelectronic with Cs⁺, and cesium in good cesium antimonide photoemitters indicates that cesium exists predominantly in the form Cs⁺, in direct conflict with present theories concerning this surface. Measurements also indicated a slight excess of antimony above that given by the formula Cs₃Sb. Band bending is only inferred from the shifts of the cesium core levels as a function of photosensitivity.     

Influence of the concentrations of potassium, sodium, and ammonium ions on the cesium sorption with mixed nickel potassium ferrocyanide sorbent based on hydrated titanium dioxide

The effect of single-charged cations (Na⁺, K⁺, NH ₄ ⁺ ) on the cesium sorption with mixed nickel potassium ferrocyanide sorbent based on hydrated TiO₂ was studied. The K⁺ and Na⁺ ions exert no effect at their concentrations of up to 0.5 M; the Cs⁺ distribution coefficients from KCl and NaCl solutions are (1.1 ± 0.5) × 10⁵ and (8 ± 3) × 10⁴ mL g^?1, respectively. The sorbent is highly specific to Cs⁺ in the presence of ammonium ions. The sorption mechanisms were studied. The concentration ranges in which Cs⁺ and NH ₄ ⁺ are sorbed by independent mechanisms (Cs⁺, by the ferrocyanide phase; NH ₄ ⁺ , by the phase of hydrated TiO₂) and in which the Cs⁺ distribution coefficient decreases owing to competitive filling of the ferrocyanide phase with ammonium ions were determined. At cesium concentrations in solution exceeding 50 mg L^?1, Cs⁺ and NH ₄ ⁺ are absorbed jointly owing to coprecipitation in the mixed ferrocyanide phase in the pore space of the sorbent.     

Photoluminescence properties and photocatalytic reactivities of Cu/zeolite and Ag/zeolite catalysts prepared by the ion-exchange method

Transition metal ions (Cu⁺, Ag⁺) incorporated within the cavities of zeolites by an ion-exchange method exhibit unique photoluminescence under UV irradiation due to the inner shell type electronic transition (d⁹s¹ → d¹⁰). Detailed photoluminescence investigations revealed that the transition metal ions exist in highly dispersed state with linear 2 coordination sphere and interact with NO_x (NO and N₂O) in their photoexcited states. In fact, Cu⁺ and Ag⁺ ions within zeolites show an efficient and unique photocatalytic performance for the decomposition of NO into N₂ and O₂ at ambient temperature. Detailed studies of the interaction of NO_x with the excited states of these metal ions indicated that an electron transfer from the s orbital of the excited state of Cu⁺ or Ag⁺ ions into the π^* antibonding orbital of NO_x initiates the decomposition of NO_x into N₂ and O₂.     

Quantum Dots of [Na4Cs6PbBr4]8+, Water Stable in Zeolite X,Luminesce Sharply in the Green

Nanocrystals (NCs) of CsPbX₃, X = Cl, Br, or I, have excellent photoluminescent properties: high quantum yield, tunable emission wavelengths (410−700 nm), and narrow emission band widths. CsPbBr₃ NCs show high promise as a green-emitting material for use in wide color gamut displays. CsPbBr₃ NCs have, however, not been commercialized because they are sensitive to moisture and heat. To avoid these problems, this work attempts to introduce CsPbBr₃ into five zeolites. The zeolite X product, Pb,Br,H,Cs,Na−X, shows superior stability toward moisture, maintaining its initial luminescence properties after being under water for more than a month. Its structure, determined using single-crystal X-ray crystallography, shows that quantum dots (QDs) of [Na₄Cs₆PbBr₄]⁸⁺ (not of CsPbBr₃) have formed. They are tetrahedral PbBr₄²⁻ ions (Pb−Br = 3.091(11) Å) surrounded by Na⁺ and Cs⁺ ions. Each fills the zeolite's supercage with its Pb²⁺ ion precisely at the center, a position of high symmetry. The peaks in the emission spectra of Pb,Br,H,Cs,Na−X and the CsPbBr₃ NCs are both at about 520 nm. The FWHM of Pb,Br,H,Cs,Na−X, however, is narrower than any previously reported for any of the CsPbBr₃ NCs, and for zeolite Y and the various mesoporous materials treated with CsPbBr₃.     

Cation exchange applications of synthetic tobermorite for the immobilization and solidification of cesium and strontium in cement matrix

Immobilization and solidification of hazardous cations like Cs¹³⁷ and Sr⁹⁰ are required while handling the radioactive waste of nuclear power plants. Efforts are on to find a fail proof method of safe disposal of nuclear wastes. In this context, various materials like borosilicate glass, zeolites, cements and synthetic rocks have been tried by several workers. This communication deals with the synthesis, characterization, cesium uptake capacity and leaching behaviour of synthetic alumina-substituted calcium silicate hydroxy hydrate, which are close to that obtained for the natural mineral,11 Å tobermorite. The synthetic mineral show cation selectivity for Cs⁺ in presence of500–1000 times concentrated solutions of Na⁺, K⁺, Mg⁺, Ca²⁺, Ba²⁺ and Sr²⁺. Although the ordinary portland cement (OPC) which is often used in waste management operations alone holds negligible amounts of Cs⁺ and Sr²⁺, the addition of alumina-substituted tobermorite to OPC enhances the retention power of cement matrix by drastically lowering the leach rate of cations     

Stabilizing Perovskite Light-Emitting Diodes by Incorporation of Binary Alkali Cations

The poor stability of perovskite light-emitting diodes (PeLEDs) is a key bottleneck that hinders commercialization of this technology. Here, the degradation process of formamidinium lead iodide (FAPbI₃)-based PeLEDs is carefully investigated and the device stability is improved through binary-alkalication incorporation. Using time-of-flight secondary-ion mass spectrometry, it is found that the degradation of FAPbI₃-based PeLEDs during operation is directly associated with ion migration, and incorporation of binary alkali cations, i.e., Cs⁺ and Rb⁺, in FAPbI₃ can suppress ion migration and significantly enhance the lifetime of PeLEDs. Combining experimental and theoretical approaches, it is further revealed that Cs⁺ and Rb⁺ ions stabilize the perovskite films by locating at different lattice positions, with Cs⁺ ions present relatively uniformly throughout the bulk perovskite, while Rb⁺ ions are found preferentially on the surface and grain boundaries. Further chemical bonding analysis shows that both Cs⁺ and Rb⁺ ions raise the net atomic charge of the surrounding I anions, leading to stronger Coulomb interactions between the cations and the inorganic framework. As a result, the Cs⁺–Rb⁺-incorporated PeLEDs exhibit an external quantum efficiency of 15.84%, the highest among alkali cation-incorporated FAPbI₃ devices. More importantly, the PeLEDs show significantly enhanced operation stability, achieving a half-lifetime over 3600 min.     

Improved photochromic stability in less deficient cesium tungsten bronze nanoparticles

Hexagonal cesium tungsten bronze (Cs_0.32WO₃) nanoparticles are well known as near-infrared (NIR) shielding materials. However, one of the critical issues for industrial applications involves a photochromic instability, i.e., a blue color change of this material under ultraviolet (UV) irradiation. This color change is attributed to the formation of H_xWO₃ phase through doping of H⁺ ions into Cs-deficient sites present at the surface of Cs_0.32WO₃ nanoparticles. Therefore, a new approach was adopted to prevent the color change by synthesizing a Cs_0.32WO₃ nanoparticle with less Cs-deficient sites using spray pyrolysis followed by heat treatment and short-time milling. The Cs_0.32WO₃ nanoparticles of spray pyrolysis route exhibited an improved photochromic stability under UV irradiation compared to those synthesized through a solid-state-reaction route. Detailed analysis using atomic resolution transmission electron microscopy revealed that the Cs_0.32WO₃ nanoparticles of spray pyrolysis route retain Cs ions up to a depth of less than 1 nm from the surface. This work demonstrates that the less-Cs-deficient Cs_0.32WO₃ nanoparticles are beneficial to improve the photochromic stability.     

Ion exchange of ammonium in natural and synthesized zeolites

In this study, zeolite Na–P and Na–Y was prepared by hydrothermal treatment of the Chinese natural clinoptilolite with NaOH. The ion exchange of NH₄⁺ into the three zeolites in the temperature range of 288–333 K was also investigated, and the thermodynamic parameters were calculated. The selectivity sequence for NH₄⁺ entering the sodium form of the three materials was Na–clinoptilolite > Na–Y > Na–P, as indicated by values of ΔG°. The results demonstrated that the Si/Al molar ratio of zeolites determined the selectivity for NH₄⁺.     

Interaction of cesium with humic materials: A comparative study of radioactivity and ISE measurements

The interaction of Cs⁺ with the different fractions of humic materials (humic acid, fulvic acid, and humin) is studied radiometrically and with an ion-selective electrode (ISE). The results indicate that Cs⁺ can partially complex humic acid, but not fulvic acid. The uptake of Cs⁺ by humin is small, and the amount of Cs⁺ required for saturation is 3.72 (mg metal)/(g humin). The ISE is a suitable tool for measuring the free metal ions remaining after the formation of the metal humate complex. Published in Russian in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 458–463. The text was submitted by the authors in English.     

Adsorption behavior of iodide ion by silver-doped zeolite 4A in LiCl-KCl molten salt

In this study, the porous material zeolite with cage-like structure was modified to prepare silver-doped zeolite 4A (abbreviated as Ag@4A) using ion exchange method, with a silver loading of 34.2 wt% and a specific surface area of ??23.62 m²/g. The adsorption performance of Ag@4A for anionic iodine in LiCl-KCl molten salt system was investigated through static adsorption experiments. The modified adsorbents and experimental samples were analyzed by XRD, SEM, ICP-OES and other methods. At 550 °C, compared with the unmodified zeolite 4A, adsorption capacity of 34 mg/g of iodine, the maximum adsorption capacity of Ag@4A for iodine ions was up to 160 mg/g. When Cs⁺ existed in the system, the maximum adsorption capacity of Ag@4A for iodide ions was about 64 mg/g; when Cs⁺ and Sr²⁺ coexisted, the maximum adsorption capacity of Ag@4A for iodide ions decreased to 103 mg/g. Ag@4A also showed a certain adsorption capacity for Cs⁺ and Sr²⁺. These results indicated that the Ag@4A has potential application for the removal of iodide ions and other cations in chloride molten salt.     

Efficient Co-Adsorption and Highly Selective Separation of Cs+ and Sr2+ with a K+-Activated Niobium Germanate by the pH Control

¹³⁷Cs and ⁹⁰Sr are hazardous to ecological environment and human health due to their strong radioactivity, long half-life, and high mobility. However, effective adsorption and separation of Cs⁺ and Sr²⁺ from acidic radioactive wastewater is challenging due to stability issues of material and the strong competition of protons. Herein, a K⁺-activated niobium germanate (K-NGH-1) presents efficient Cs⁺/Sr²⁺ coadsorption and highly selective Cs⁺/Sr²⁺ separation, respectively, under different acidity conditions. In neutral solution, K-NGH-1 exhibits ultrafast adsorption kinetics and high adsorption capacity for both Cs⁺ and Sr²⁺ (q_m^Cs = 182.91 mg g⁻¹; q_m^Sr = 41.62 mg g⁻¹). In 1 M HNO₃ solution, K-NGH-1 still possesses q_m^Cs of 91.40 mg g⁻¹ for Cs⁺ but almost no adsorption for Sr²⁺. Moreover, K-NGH-1 can effectively separate Cs⁺ from 1 M HNO₃ solutions with excess competing Sr²⁺ and Mⁿ⁺ (Mⁿ⁺ = Na⁺, Ca²⁺, Mg²⁺) ions. Thus, efficient separation of Cs⁺ and Sr²⁺ is realized under acidic conditions. Besides, K-NGH-1 shows excellent acid and radiation resistance and recyclability. All the merits above endow K-NGH-1 with the first example of niobium germanates for radionuclides remediation. This work highlights the facile pH control approach towards bifunctional ion exchangers for efficient Cs⁺/Sr²⁺ coadsorption and selective separation.     

Crystal structure of cesium zeolite A prepared by complete aqueous exchange

The complete exchange of zeolite 4A with Cs⁺ has been achieved by the reaction of a single crystal of hydrated NH₄⁺-A with a modest excess of CsOH slush. Its structure was determined by X-ray crystallographic methods. Up to one additional molecule of CsOH is taken up per sodalite cavity. To avoid close Cs⁺-Cs⁺ contacts through 6-rings, four Cs⁺ ions per large cavity are found nearly opposite 4-rings rather than opposite 6-rings as is usually seen. The hydroxide ion is presumed to be between the two Cs⁺ ions found in each sodalite cavity.     

Synthesis and application of Poly(acrylamide-itaconic Acid)/Zirconium tungstate composite material for cesium removal from different solutions

This study is conducted to find the conditions required to synthesize composite material for cesium (¹³⁴Cs⁺) removal from the generated liquid waste associated with nuclear, medical, industrial, and/or research activities. The study shows that the optimum conditions required for synthesizing “Poly [acrylamide (AM)-itaconic acid (IA)]/N,N′-methylenediacrylamide (DAM)/Zirconium tungstate (ZrW)” or “Poly(AM-IA)/DAM/ZrW” are 0.01 g DAM dose as a cross-linker, a co-monomer concentration of 20%, a co-monomer composition (AM-IA) (12:88), and 0.03 g (melted at 450 °C–500 °C) ZrW with gamma irradiation dose of 30 kGy. The composite material was characterized by Fourier infrared (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscope (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The adsorption performance of the composite was investigated. The maximum removal efficiency of ¹³⁴Cs⁺ ions was found to be 93% in moderate alkaline solutions at pH 8 ± 0.2 after 90 min. Kinetic studies indicated that the adsorption process is controlled by the pseudo-second-order kinetic model as a chemisorption process. Fitting of the adsorption data has pointed out that the adsorption process follows the Freundlich isotherm model as heterogeneous process. The maximum adsorption capacity (q_max) is 5.298 mmol Cs⁺ g^?1 adsorbent. Applicability of the synthesized composite material was also examined to remove ¹³⁴Cs⁺ ions in different aqueous solutions.     

Reduction behaviour of (AgNa)A and (AgM2+Na)A zeolites

The reduction of silver-exchanged A zeolites proceeds in at least two distinct steps. At lower reduction temperatures up to 500 K about 67% of the silver ions present in the lattice of the unreduced zeolites are reduced and charged silver clusters (Ag₃⁺) are formed. This process is accompanied by a redistribution of the remaining cations resulting in characteristic changes of the adsorption properties. The position of silver ions in (AgNa)A and (AgM²⁺Na)A zeolites does not influence their reduction behaviour in the first reaction step, The further reduction of the Ag₃⁺ clusters at higher temperatures depends on the Ag-exchange and on the kind of M²⁺ ion, It seems that the low temperature reduction proceeds over either Ag₉⁺ or Ag₉²⁺ species depending on the silver content.     

Crystallographic evaluation of sodium zirconium phosphate as a host structure for immobilization of cesium

Sodium zirconium phosphate (NZP) is a potential material for immobilization of nuclear effluents. The existence of cesium containing NZP structure was determined on the basis of crystal data of solid solution. It was found that up to ~9.0 wt% of cesium could be loaded into NZP formulations without significant changes of the three-dimensional framework structure. The crystal chemistry of Na_1−x Cs _x Zr₂P₃O₁₂ (x = 0.1–0.4) has been investigated using General Structure Analysis System programming. The CsNZP phases crystallize in the space group R-3c and Z = 6. Powder diffraction data have been subjected to Rietveld refinement to arrive at a satisfactory structural convergence of R-factors. The unit cell volume and polyhedral (ZrO₆ and PO₄) distortion increase with rise in the mole% of Cs⁺ in the NZP matrix. The PO₄ stretching and bending vibrations in the infrared region have been assigned. SEM, TEM, and EDAX analysis provide analytical evidence of cesium in the matrix.     

Thermoluminescence response of CaS:Bi nanophosphor exposed to 200 MeV Ag ion beam

A study of the thermoluminescence (TL) parameters has been performed on swift heavy ion exposed Bi³⁺ doped CaS nanophosphors prepared by the chemical co-precipitation method. All the samples have been exposed to 200 MeV Ag⁺¹⁵ ions in a fluence range of 1 × 10¹²–1 × 10¹³ ions/cm². The prominent TL glow peak at 403 K (observed for the γ-irradiated sample) appeared at the same position in the 200 MeV Ag⁺¹⁵ ion beam irradiated samples, while the other peak at 466 K disappeared and the broad peak normally measured at 534 K split into two peaks at 535 K and 582 K for the Ag⁺¹⁵ ion beam irradiated samples. The effect of different Bi³⁺ concentration has been investigated and it was found that the maximum TL intensity was measured for the 0.08 mol% sample. The effect of different heating rates on the TL response has also been determined. The trapping parameters (i.e. activation energy, frequency factor, order of kinetic) of all the individual peaks of the glow curves have been analysed by using Chen’s formulae. The low fading and linear TL response in the range of 1 × 10¹²–1 × 10¹³ ions/cm² will be helpful to explore the potential use of this material for heavy ion dosimetry.     

Thermal chemistry of a high temperature solid lubricant, cesium oxythiomolybdate Part I Thermo-oxidative stability of Cs2MoOS3

Cesium oxythiomolybdate (Cs₂MoOS₃) is a potential high temperature solid lubricant. It undergoes complex oxidation reactions at elevated temperatures, but continues to provide lubrication above the oxidation temperature. Therefore, in order to determine the nature of the lubricant at elevated temperature, it is necessary to understand the thermal chemistry of Cs₂MoOS₃in an air environment. The thermo-oxidative stability of Cs₂MoOS₃was evaluated between room temperature and 800°C in air. Melting and phase transition temperatures were determined. X-ray photoelectron spectroscopy, micro-Raman scattering and x-ray diffraction were used to identify the chemical species evolved at increasing temperatures. As-received Cs₂MoOS₃was not pure. It also contained cesium molybdates, molybdenum oxides, and Cs₂SO₄. Between 300–400°C, the material began to decompose forming Cs₂SO₄and MoS₂. Between 400–600°C, Cs₂MoOS₃also formed cesium molybdates and molybdenum oxides. In addition, the Cs₂SO₄began to oxidize to cesium oxides (which melted) and SO _x gas. Also, MoS₂oxidized to MoO₃. At approximately 700°C, MoO₃began to sublime. Upon cooling from 800°C, the material was primarily cesium oxides and Cs₂MoO₄, with small amounts of complex cesium molybdates and molybdenum oxides.     

Electrical conductivity of Cs<Subscript>3</Subscript>PO<Subscript>4</Subscript> doped with trivalent cations

Cs_{3 ? 3x} M _x PO₄ (M = Sc, Y, La, Sm, Nd) solid electrolytes have been synthesized, their phase composition has been determined, and their electrical conductivity has been measured as a function of temperature. In all of the systems, we have identified cesium orthophosphate based solid solutions. Above ～550°C, the solid solutions are isostructural with the high-temperature, cubic phase of Cs₃PO₄. They offer high cesium ion conductivity owing to the formation of cesium vacancies via 3Cs⁺ → M³⁺ substitutions and the decrease in phase transition temperature. The conductivity of the synthesized solid solutions, (4.8?5.6) × 10^?3 S/cm at 300°C and (1.6?1.9) × 10^?1 S/cm at 800°C, is at the level of earlier studied Cs_{3 ? 2x} M _x ^II PO₄ solid electrolytes.