Effect of ZnO doping on morphology and electrochemical properties of sub-micron RuO2 sensing electrode of DO sensor

Thick-film 20 mol% ZnO-doped RuO₂ sensing electrodes (SEs) were fabricated by screen-printing technique on the platinised alumina substrate of the planar electrochemical dissolved oxygen (DO) sensor. The effect of ZnO doping on morphology, electrochemical properties and sensing characteristics of the sensor was investigated. It was found that ZnO doping has not only improved the SE structure, but has also enhanced selectivity of the DO sensor. Selectivity testing exhibited that the presence of Cl⁻, Li⁺, SO₄²⁻, NO³⁻, Ca²⁺, PO₄³⁻, Mg²⁺, Na⁺ and K⁺ with a concentration range of 10⁻⁷ to 10⁻¹ mol/L in the solution had practically no effect on the sensor's emf. The reason in enhancement of the sensor characteristics could be related to the establishment of the better structured SE as more advanced crystallization is achieved for the doped RuO₂-SE.     

Separation of transuranium and transplutonium elements on S-957 sorbent

Sorption of Pu⁴⁺, UO₂²⁺, NpO₂⁺, Am³⁺, and Eu³⁺ ions on S-957 cation exchanger from 2–7 M HNO₃ solutions was studied. The following selectivity series was obtained: Pu⁴⁺ > UO₂²⁺ > NpO₂⁺ > Am³⁺ ≈ Eu³⁺. The static and dynamic capacities of the sorbent for Pu were determined, and the eluent composition for the efficient desorption was chosen. The possibility of separating Pu(IV)-Am(III) and Pu(IV)-Np(V) pairs on the sorbent in the column chromatography mode was demonstrated.     

Effect of compositional variations on charge compensation of AlO4 and BO4 entities and on crystallization tendency of a rare-earth-rich aluminoborosilicate glass

This paper presents the structural and crystallization study of a rare-earth-rich aluminoborosilicate glass that is a simplified version of a new nuclear glass proven to be a potential candidate for the immobilization of highly concentrated radioactive wastes that will be produced in the future. In this work, we studied the impact of changing the nature of alkali (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺) or alkaline-earth (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) cations present in glass composition on glass structure (by ²⁷Al and ¹¹B nuclear magnetic resonance spectroscopy) and on its crystallization tendency during melt cooling at 1 K/min (average cooling rate during industrial process). From these composition changes, it was established that alkali cations were preferentially involved in charge compensation of (AlO₄)⁻ and (BO₄)⁻ entities in the glassy network comparatively to alkaline-earth cations. Whatever the nature of alkali cations, glass compositions containing calcium gave way to the crystallization of an apatite silicate phase bearing calcium and rare-earth (RE) cations (Ca₂RE₈(SiO₄)₆O₂, RE = Nd or La) but melt crystallization tendency during cooling strongly varied with the nature of alkaline-earth cations.     

Photoluminescence properties of RE-activated Na3GdP2O8 (RE = Tb, Dy, Eu, Sm) under VUV excitation

RE³⁺-activated monoclinic Na₃GdP₂O₈ (RE³⁺ = Tb³⁺, Dy³⁺, Eu³⁺, Sm³⁺) phosphors have been synthesized by a solid-state reaction method. Their photoluminescence properties in the vacuum ultraviolet (VUV) region were investigated. By analyzing their excitation spectra, the host-related absorption band was determined to be around 166 nm. The f-d transition bands and the charge transfer bands for Na₃GdP₂O₈:RE³⁺ (RE³⁺ = Tb³⁺, Dy³⁺, Eu³⁺, Sm³⁺) were assigned and corroborated. For the sample Na₃GdP₂O₈:5%Tb³⁺, the strong bands at around 202 and 221 nm are assigned to the 4f-5d spin-allowed transitions and the weak band at 266 nm is related to the spin-forbidden transition of Tb³⁺. For Na₃GdP₂O₈:5%Dy³⁺, the broad band at 176 nm could be related to the f-d transitions of Dy³⁺ and the O²⁻ → Dy³⁺ charge transfer band (CTB) besides the host-related absorption. In the excitation spectrum of Eu³⁺ doped sample, the O²⁻ → Eu³⁺ CTB is observed to be at 245 nm. For the Sm³⁺ doped sample, the O²⁻ → Sm³⁺ CTB is not distinguished obviously and is overlapped with the host-related absorption band.     

Correlation between structure and photoluminescence of the europium doped glaserite-type phosphate Na2SrMg(PO4)2

A new phosphate Na₂SrMg(PO₄)₂ has been synthesized and investigated by X-ray diffraction, DTA, ³¹P NMR spectroscopy and photoluminescence measurements. This compound crystallizes in the space group P2₁/a of the monoclinic system with the cell parameters: a = 9.158(1) Å, b = 5.267(1) Å, c = 13.498 (1) Å, β = 90.01(1)° and four formula units per cell. Its structure is closely related to that of the mineral glaserite K₃Na(SO₄)₂ and thus it can be described by the general formula XY₂M(TO₄)₂. The X, Y, M and T sites are fully occupied by Sr²⁺, Na⁺, Mg²⁺ and P⁵⁺ cations, respectively. The anionic framework is consisted by the stacking along the [001] direction of two kinds of alternating [MgP₂O₈⁴⁻]_∞ mixed layers parallel to the (a, b) plane and resulting from a corner-sharing between MgO₆ octahedra and PO₄ tetrahedra. The Sr²⁺ cations are located within the interlayer space, while those Na⁺ are found in large cavities bounded to the layers. The DTA analysis showed a congruent melting of this compound at 1374 K. The ³¹P NMR spectroscopy confirmed the presence of two distinct phosphors sites in the structure. Optical studies were performed on the Na₂SrMg(PO₄)₂ compound doped with Eu³⁺ and Eu²⁺. The trivalent europium was used as a local probe, replacing strontium and sodium, what gives complementary and consistent results to the crystallographic analyses. The divalent europium was used to analyze preliminary the potentiality for this compound to be integrated as phosphor in Light Emitting Diode (LED).     

KxNa1 − xNbO3 powder synthesized by molten-salt process

K_xNa_1 − xNbO₃ ceramic powders have been successfully synthesized in different salts (NaCl, KCl, NaCl-KCl). Our results reveal that K_xNa_1 − xNbO₃ powders with single-phase perovskite structure can be formed at a low temperature such as 750 °C. The type of salts has significant effects on the morphology and chemical composition of the powders. As Na⁺ has a higher diffusing rate and occupies the A-site in the perovskite structure more easily as compared to K⁺, the powder contains only a small amount of K⁺ (x ∼ 0.10) when it is synthesized according to formula K_0.5Na_0.5NbO₃ and in a flux containing the same molar content of Na⁺ and K⁺. By using a NaCl or KCl salt, the K⁺ concentration x can be adjusted to almost 0 and 0.77, respectively.     

Formation of Cd particles by UV laser irradiation

Formation of the metal particles of Cd has been studied by nanosecond laser flash photolysis using an ArF excimer laser with the oscillation wavelength of 193 nm. The sample was a 10% methanol solution of CdCl₂. The solvated electron, e_aq⁻, was generated by the excitation of charge transfer bands of Cl⁻ to solvent. The e_aq⁻ efficiently reduced Cd²⁺ to Cd⁺ during a laser pulse of 30 ns (FWHM). The Cd particles were produced by the reaction between Cd⁺ and Cd⁺. In the air saturated solution, the Cd⁺ was easily oxidized by dissolved oxygen. The concentration of the Cd particles formed in the degassed solution was approximately twice of that in the air saturated solution.     

Preparation of a modified flue gas desulphurization residue and its effect on pot sorghum growth and acidic soil amelioration

A modified flue gas desulphurization residue (MFGDR) was prepared and its effects on sorghum growth and acidic soil amelioration were evaluated in this paper. The MFGDR was prepared by calcining a mixture of dry/semi-dry flue gas desulphurization (FGD) residue from a coal-fired power plant, sorted potash feldspar and/or limestone powder. The available nutrients from the MFGDR were determined with 4.91 wt% K⁺, 1.15 wt% Mg²⁺, 22.4 wt% Ca²⁺, 7.01 wt% Si⁴⁺ and 2.07 wt% SO₄²⁻-S in 0.1 mol L⁻¹ citric acid solution. Its pH value was held at 9.60 displaying slightly alkaline. The results of sorghum pot growth in both red and crimson acidic soil for 30 days indicated that adding the MFGDR at a dosage of 2 g kg⁻¹ in total soil weight would increase the growth rate of biomass by 24.3-149% (wet weight basis) and 47.3-157% (dry weight), the stem length and thickness increase by 5.75-22.1% and 4.76-30.9% in contrast with CK treatment for two test cuttings, respectively. The effect on sorghum growth was attributed to the increase of available nutrients, the enhancement of soil pH value and the reduction of aluminum toxicity in acidic soil due to the addition of the MFGDR. The experimental results also suggested that the MFGDR could be effectively used to ameliorate the acidic soil which is widely distributed throughout the southern China.     

Adsorptive removal of fluoride from aqueous solution using orange waste loaded with multi-valent metal ions

Adsorption gels for fluoride ion were prepared from orange waste by saponification followed by metal loading. The pectin compounds contained in orange waste creates ligand exchange sites once it is loaded with multi-valent metal ions such as Al³⁺, La³⁺, Ce³⁺, Ti⁴⁺, Sn⁴⁺, and V⁴⁺ to be used for fluoride removal from aqueous solution. The optimum pH for fluoride removal depends on the type of loaded metal ions. The isotherm experiments showed the Langmuir type monolayer adsorption. Among all kinds of metal loaded gels tested, Al loaded gel appeared to exhibit the most favorable adsorption behavior. The adsorption kinetics of fluoride on loaded gel demonstrated fast adsorption process. The presence of NO₃⁻, Cl⁻ and Na⁺ ions has negligible effect on fluoride removal whereas SO₄²⁻ and HCO₃⁻ retarded the fluoride removal capacity in some extent. Fluoride removal at different adsorbent doses showed that fluoride concentration can be successfully lowered down to the acceptable level of environmental standard. The fluoride adsorption mechanism was interpreted in terms of ligand exchange mechanism. The complete elution of adsorbed fluoride from the gel was successfully achieved using NaOH solution.     

Geochemistry of the upper Han River basin, China: 2: Seasonal variations in major ion compositions and contribution of precipitation chemistry to the dissolved load

A total of 252 water samples were collected from 42 sites across the upper Han River basin during the time period from 2005–2006. Major ions (Cl⁻, NO₃⁻, SO₄²⁻, HCO₃⁻, Na⁺, K⁺, Ca²⁺ and Mg²⁺), Si, water temperature, pH, EC and TDS were determined and consequently correlation matrix, analysis of variance, factor analysis and principal component analysis were performed in order to identify their seasonal variations and atmospheric inputs into river solutes. The results reveal that pH, EC, TDS, Cl⁻, SO₄²⁻, HCO₃⁻, Ca²⁺ and Mg²⁺, K⁺ and Si generally tend to show the minimum compositions in months belong to the rainy season, while the dry season for NO₃⁻ and Na⁺. NO₃⁻, Mg²⁺ and Si have the maximum concentrations in months belong to the rainy season. By comparing the major ions relating to hydrological regime, NO₃⁻, contrary to other elements, has higher concentration in the rainy season. The overall water quality is non-polluted, while there are indications of enrichment of inorganic anions including NO₃⁻ causing water entrophication in the near future. The atmospheric inputs contribute to river solutes is limited with a mean inputs of approximate 1% in the basin. The understanding of the major ion dynamics would help water quality conservation in the basin for China's interbasin water transfer project.     

Some barium titanate based dielectrics

Some new potential dielectric materials have been made through the cross-substitution of Ba²⁺ by a 1:1 molar combinations of tri-(La³⁺) and mono-valent (Li⁺, Na⁺, K⁺) ions at the Ba²⁺ site in BaTiO₃. Chemical analysis shows that compositions in the potassium series are about 6·1% deficient in their K₂O content and exhibit interesting dielectric relaxations. The cross-substitution has lowered theT _c down to room temperature. The disorder in the larger ‘A’ cation sublattice of the three systems has been established by infra-red and x-ray data. This leads to microscopic compositional variations, which in turn can account for the diffuseness of the dielectric anomalies observed in the barium titanate-rich compositions (0⩽x⩽0·3). since deceased.     

Fabrication of (K, Na)NbO3 glass-ceramics and crystal line patterning on glass surface

Crystallization behavior of (30−x)K₂O-xNa₂O-25Nb₂O₅-45SiO₂ (KNNS; x = 0, 5, 10, 20 and 30) (mol%) glasses was clarified and perovskite-type nonlinear optical (K, Na)NbO₃ (KNN) crystals were synthesized by using a conventional glass-ceramics method. It was found that Na₂O amounts over around x = 10 mol% were necessary to form perovskite-type KNN crystals showing second-harmonic generations. The substitution of K⁺ and Na⁺ ions was confirmed from X-ray diffraction (XRD) analysis. A continues-wave of Yb:YVO₄ fiber laser (wavelength: 1080 nm) was irradiated onto CuO doped KNNS; x = 10 (Cu-KNNS) surface. The absorption coefficient of this Cu-KNNS glass was determined to be α = 5.0 cm⁻¹. Perovskite-type KNN crystals were patterned in the condition of the laser power of >1.20 W and the laser scanning speed of S = 7 μm/s, and their structure was determined by Raman scattering spectra and XRD analysis.     

Ion-selective properties of metastable (VO)<Subscript>0.09</Subscript>V<Subscript>0.18</Subscript>Mo<Subscript>0.82</Subscript>O<Subscript>3</Subscript> · 0.54H<Subscript>2</Subscript>O

This paper describes a thin-film solid electrode with an ion-sensitive membrane based on the mixed oxide (VO)_0.09V_0.18Mo_0.82O₃ · 0.54H₂O. The electrode is selective for tetravalent vanadium in the concentration range 3 ≤ pC _V ⁴⁺ ≤ 5 and acidity range 4.5 ≤ pH ≤ 6, with a slope close to the theoretical value. In the range 1 ≤ pH < 5, the electrode responds to changes in hydrogen ion concentration, with a slope of 50 ± 2 mV/pH. Its alkali-metal-ion response shows up in the range 1 ≤ pC _M ⁺ ≤ 4 for pH ≥ 6. We examine the effect of the Li⁺, K⁺, Na⁺, Cs⁺, Rb⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Co²⁺, Ni²⁺, Mn²⁺, Al³⁺, Cr³⁺, and VO₂⁺ ions on the potential of the electrode and determine its selectivity coefficients for these cations.     

Emission features of LiBaBO3:Sm3+ red phosphor for white LED

A novel red phosphor, LiBaBO₃:Sm³⁺, was synthesized by solid state reaction, and its emission properties were studied. The excitation and emission spectra indicate that this phosphor can be effectively excited by ultraviolet (UV) 345, 373 and 404 nm light, and exhibit a satisfactory red performance (597 nm), nicely, fitting in with the widely applied UV LED chip. The emission intensity of LiBaBO₃:Sm³⁺ phosphor varies with increasing Sm³⁺ concentration, and occurs to concentration quenching, and the concentration self-quenching mechanisms are the d-d interaction by Dexter theory. Emission intensity of LiBaBO₃:Sm³⁺ phosphor was enhanced by doping charge compensation Li⁺, Na⁺, K⁺, and the emission intensity of doping Li⁺ is higher than that of Na⁺ or K⁺.     

Tl-208, Pb-212, Bi-212, Ra-226 and Ac-228 adsorption onto polyhydroxyethylmethacrylate-bentonite composite

The adsorption of naturally occurring radionuclides (²⁰⁸Tl⁺, ²¹²Pb²⁺, ²²⁶Ra²⁺, ²¹²Bi³⁺ and ²²⁸Ac³⁺) onto Polyhydroxyethylmethacrylate-bentonite (PHEMA-B) composite was investigated. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. The adsorption isotherms were L type of Giles classification proving that PHEMA-B had a high affinity adsorbent for the studied radionuclides. The Langmuir adsorption capacities (X_L) were in the order of ²²⁶Ra (2.8 MBq kg⁻¹)>²¹²Bi (0.4 MBq kg⁻¹)>²¹²Pb (0.3 MBq kg⁻¹)>²²⁸Ac and ²⁰⁸Tl (0.2 MBq kg⁻¹). The adsorption process was physical via complex formation after proton exchanger for which the adsorption energies obtained from DR model was evidence. The enthalpy and entropy changes were positive and the negative free enthalpy change was proof for the spontaneity of adsorption. The reusability tests for PHEMA-B for five uses demonstrated that the adsorbent could be reused after complete recovery of the loaded radionuclide ions by 1 M HCl. The chemical structure of the composite did not change after the reuses and storage foregoing.     

Role of bismuth and titanium in Na2O-Bi2O3-TiO2-P2O5 glasses and a model of structural units

0.60Na₂O-0.40P₂O₅ and (0.55−z)Na₂O-0.05Bi₂O₃-zTiO₂-0.40P₂O₅ glasses (0≤z≤0.15) were prepared by melting at 1000°C mixtures of Na₂CO₃, Bi₂O₃, TiO₂ and (NH₄)₂HPO₄. Differential Scanning Calorimetry (DSC) measurements give the variation of glass transition temperature (T_g) from 269°C (for 0.60Na₂O-0.40P₂O₅) to 440°C (for z=0.15). The density measurements increases from 2.25 to 3.01 g/cm³. FTIR spectroscopy shows the evolution of the phosphate skeleton: (PO₃)_∞ chains for 0.60Na₂O-0.40P₂O₅ to P₂O₇⁴⁻ groups in the glasses containing Bi₂O₃ or both Bi₂O₃ and TiO₂. When bismuth oxide and titania are added to sodium phosphate glass, phosphate chains are depolymerized by the incorporation of distorted Bi(6) and Ti(6) units through POBi and POTi bonds. Bi₂O₃ and TiO₂ are assumed to be present as six co-ordinated octahedral [BiO_6/2]³⁻and [TiO_6/2]²⁻ units again with shared corners. This is accompanied by the simultaneous conversion of [POO_3/2] into [PO_4/2]⁺ units which achieves charge neutrality in the glasses.     

Direct Separation of UO22+ by Coordination Sieve Effect via Spherical Coordination Traps

Molecule sieve effect (MSE) can enable direct separation of target, thus overcoming two major scientific and industrial separation problems in traditional separation, coadsorption, and desorption. Inspired by this, herein, the concept of coordination sieve effect (CSE) for direct separation of UO₂²⁺, different from the previously established two-step separation method, adsorption plus desorption is reported. The used adsorbent, polyhedron-based hydrogen-bond framework (P-HOF-1), made from a metal–organic framework (MOF) precursor through a two-step postmodification approach, afforded high uptake capacity (close to theoretical value) towards monovalent Cs⁺, divalent Sr²⁺, trivalent Eu³⁺, and tetravalent Th⁴⁺ ions, but completely excluded UO₂²⁺ ion, suggesting excellent CSE. Direct separation of UO₂²⁺ can be achieved from a mixed solution containing Cs⁺, Sr²⁺, Eu³⁺, Th⁴⁺, and UO₂²⁺ ions, giving >99.9% removal efficiency for Cs⁺, Sr²⁺, Eu³⁺, and Th⁴⁺ ions, but <1.2% removal efficiency for UO₂²⁺, affording benchmark reverse selectivity (S_M/U) of >83 and direct generation of high purity UO₂²⁺ (>99.9%). The mechanism for such direct separation via CSE, as unveiled by both single crystal X-ray diffraction and density-functional theory (DFT) calculation, is due to the spherical coordination trap in P-HOF-1 that can exactly accommodate the spherical coordination ions of Cs⁺, Sr²⁺, Eu³⁺, and Th⁴⁺, but excludes the planar coordination UO₂²⁺ ion.     

Enhanced red-emitting phosphor Na<Subscript>2</Subscript>Ca<Subscript>3</Subscript>Si<Subscript>2</Subscript>O<Subscript>8</Subscript>:Eu<Superscript>3+</Superscript> by charge compensation

A series of novel red-emitting Na₂Ca_3???x Si₂O₈:xEu³⁺ phosphors were synthesized by solid state reactions. The phosphors can strongly absorb 395 nm light, and show red emission with a good color purity. The excitation and emission spectra properties of Na₂Ca₃Si₂O₈:Eu³⁺ were characterized. Na₂Ca₃Si₂O₈:Eu³⁺ with self-compensated and alkali metal ions charge compensated approaches (2Ca²⁺→Eu³⁺ + M⁺, M?=?Li⁺, Na⁺, K⁺) have investigated, which found that the red emission of luminescent intensity can be greatly enhanced, and shows superior luminescent property to the commercial Y₂0₃S:Eu³⁺. The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs.     

In-situ analysis of positive and negative energetic ions generated during Sn-doped In2O3 deposition by reactive sputtering

Using a quadrupole mass spectrometer combined with an energy analyser, we have investigated the in-situ energy distribution of highly energetic ions generated during reactive sputtering of In-Sn alloy (IT) targets and non-reactive sputtering of Sn-doped In₂O₃ (ITO) ceramic targets. Ar⁺, In⁺, O⁺, O⁻, O₂⁻, InO⁻ and InO₂⁻ ions with kinetic energies greater than 40 eV were clearly observed. Upon increasing the O₂ flow ratio for reactive sputtering, the surface of the IT target changes from metal (metal mode) to oxide (oxide mode) via a state of mixed metal and oxide (transition region). O⁻ ions with the kinetic energy corresponding to cathode voltage are generated at the oxide layer, which expands upon the target surface with increasing O₂ flow ratio in the metal mode and the transition region. In contrast, the flux of 60-eV Ar⁺ ions decreases with increasing O₂ flow ratio. The presence of 125- and 200-eV In⁺ ions is attributed to the dissociation of InSnO₂⁻ and InO₂⁻ with the kinetic energy corresponding to cathode voltage, respectively, while the presence of 40- and 150-eV O⁺ ions is attributed to the dissociation of InO₂⁻ and O₂⁻ with the kinetic energy corresponding to cathode voltage, respectively.     

Improved optical photoluminescence by charge compensation in the phosphor system CaMoO4:Eu3+

It has been found that charge compensated CaMoO₄:Eu³⁺ phosphors show greatly enhanced red emission under 393 and 467 nm-excitation, compared with CaMoO₄:Eu³⁺ without charge compensation. Two approaches to charge compensation, (a) 2Ca²⁺ → Eu³⁺ + M⁺, where M⁺ is a monovalent cation like Li⁺, Na⁺ and K⁺ acting as a charge compensator; (b) 3Ca²⁺ → 2Eu³⁺ + vacancy, are investigated. The influence of sintering temperature and Eu³⁺ concentration on the luminescent property of phosphor samples is also discussed.