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1.
Maiden attempt has been made for the direct estimation of the contributions of silver and copper ions to the ionic conductivity in superionic solids obtained in CuI-doped silver oxysalt systems. The application of the combined electrolysis and EDS techniques towards qualitative and quantitative analyses of the mobile ionic species in solid electrolyte systems having more than one possible mobile ion is reported. These studies confirmed that these electrolyte materials are purely Ag + conducting up to 50 mol% CuI in xCuI–(100 − x)[2Ag 2O–0.7V 2O 5–0.3B 2O 3] and xCuI–(100 − x)[Ag 2O–0.7MoO 3–0.3WO 3] systems and small fraction of tCu+ exists above 60 mol% CuI. These solid electrolyte materials exhibited a high ionic transport numbers ( ti) of >0.985 and the ti increases when two glass formers are used. 相似文献
2.
Electrochemical investigation of the solid superionic conductor Ag 7I 4PO 4 (0.8 AgI + 0.2 Ag 3PO 4) at room temperature and at 40°C were performed by means of cyclic voltammetry, cyclic chronoamperometry and cyclic chronocoulometry, normal pulse polarography and ac polarography. It was shown that the Ag + ↔ Ag redox process on Pt and Ag working electrode occurs with a certain overvoltage, ie that for Ag + → Ag + oxidation and the return of Ag + ions into the electrolyte a certain overvoltage is necessary. From the determined values of the exchange current one estimates the redox process as a rather fast one. The silver working electrode is electrochemically inactive, while only cathodically deposited silver is electrochemically active and can be oxidized to Ag + ions. Chronoamperometry and chronocoulometry show that there is a certain difference in the behaviour of Pt and Ag working electrodes due to uneven passivating anodic processes. On the basis of measurements of faradaic and capacitance currents and their dependence on frequency, diagrams of complex impedance of the Pt/Ag 7I 4PO 4 interface at various anodic and cathodic polarizations of the Pt electrode were plotted. The dependence of the serial capacity of the interface on the dc potential and temperature are discussed. 相似文献
3.
Hydroxyapatite (Ca 10(PO 4) 6(OH) 2: HAP) was co-substituted with Ti(IV) and antibacterial ions (Ag +, Cu 2+ or Zn 2+) (HAPTiM), by coprecipitation and ion-exchange methods. Both HAPTiAg and HAPTiCu coated on porous spumous nickel film showed high efficiency for killing Escherichia coli and Staphylococcus aureus in the dark and under weak UVA irradiation, respectively. Moreover, their bactericidal activities were much higher than that of P25-TiO 2 film. The studies of ESR revealed that not only O 2− was formed on HAPTiM, HAPTi, HAP and P25-TiO 2 films under weak UVA irradiation, but also at ambient temperature without light O 2− was generated on HAPTiCu, HAPTiAg, and HAPTi. The redox couples of Cu 0/Cu 2+ and Ag 0/Ag + in the structure of HAPTiCu (Ag) caused the transfer of electron leading to the O 2− generation under the above conditions. The higher bactericidal activities of HAPTiM were due to the synergy of the oxidation role of the O 2− and the bacteriostatic action of antibacterial ions. The process of the damage of the cell wall and the cell membrane was directly observed by TEM, and further confirmed by the determination of potassium ion (K +) leakage from the killed bacteria. 相似文献
4.
The electronic states of LaMn 1−xCu xO 3+λ ( x=0–0.4) have been studied with X-ray photoelectron spectroscopy (XPS). The valence states of substituted copper ions were Cu 2+ and the manganese ions were a highly mixed state of Mn 3+ and Mn 4+. The nonstoichiometry and electronic state of lattice oxygen have been studied. The samples at x=0 and 0.1 had an excess of lattice oxygen but those at x=0.2–0.4 had lattice oxygen deficiency. A modified Auger parameter (Δ ′) was used to evaluate the electronic states of oxygen ions. The Δ ′ of lattice oxygen increased with increasing substitute quantity. This increase of Δ ′ reflected the decrease of ionic bond character of lattice oxygen. The adsorbed oxygen species on LaMn 1−xCu xO 3+λ was assigned mainly as O − from the peak positions of spectra for the O 1s and O KLL levels, and the Δ ′ of this O − decreased with x. This decrease, i.e., the increase of ionic bond character of adsorbed oxygen was correlated well with the value of nonstoichiometry of lattice oxygen. The rate of CO oxidation at 448 K was increased by the substitution till x=0.4. We consider that this enhancement of reactivity comes from the change of electronic state of adsorbed oxygen, O− itself, i.e., a weak interaction between O− and low coordinated metal site brings about a high reactivity. 相似文献
5.
Bi 0.5(Na 1−x−yK xAg y) 0.5TiO 3 piezoelectric ceramics were prepared by conventional ceramic processes. X-ray diffraction patterns show a pure perovskite structure, indicating that the K + and Ag + ions substitute for the Na + ions in Bi 0.5Na 0.5TiO 3. The temperature dependence of the dielectric constant and dissipation factor shows all ceramics to experience two phase transitions: from ferroelectric to anti-ferroelectric and from anti-ferroelectric to paraelectric. The transition temperature from ferroelectric to anti-ferroelectric and the temperature at which the dielectric constant reaches its maximum value decrease with the increase of K + amount. At room temperature, the ceramics containing 17.5–20 mol% K + and 2 mol% Ag + exhibit high piezoelectric constant ( d33 = 180 pC/N) and high electromechanical coupling factor ( kp = 35%). 相似文献
6.
The formation of Ag 2S monolayer has been studied in 0.1 mol dm −3 NaOH supporting electrolyte by a radiotracer method in the potential range from −400 to +200 mV (on rhe scale) using 35S labelled Na 2S. Comparison of the results obtained with the radiotracer method and cyclic voltammetric measurements leads to the conclusion that the formation of the Ag 2S monolayer takes place at least in two separate steps in two different potential ranges. 相似文献
7.
Catalytic methane combustion and CO oxidation were investigated over AFeO 3 (A=La, Nd, Sm) and LaFe 1−xMg xO 3 ( x=0.1, 0.2, 0.3, 0.4, 0.5) perovskites prepared by citrate method and calcined at 1073 K. The catalysts were characterized by X-ray diffraction (XRD). Redox properties and the content of Fe 4+ were derived from temperature programmed reduction (TPR). Specific surface areas (SA) of perovskites were in 2.3–9.7 m 2 g −1 range. XRD analysis showed that LaFeO 3, NdFeO 3, SmFeO 3 and LaFe 1−xMg xO 3 ( x·0.3) are single phase perovskite-type oxides. Traces of La 2O 3, in addition to the perovskite phase, were detected in the LaFe 1−xMg xO 3 catalysts with x=0.4 and 0.5. TPR gave evidence of the presence in AFeO 3 of a very small fraction of Fe 4+ which reduces to Fe 3+. The fraction of Fe 4+ in the LaFe 1−xMg xO 3 samples increased with increasing magnesium content up to x=0.2, then it remained nearly constant. Catalytic activity tests showed that all samples gave methane and CO complete conversion with 100% selectivity to CO 2 below 973 and 773 K, respectively. For the AFeO 3 materials the order of activity towards methane combustion is La>Nd>Sm, whereas the activity, per unit SA, of the LaFe 1−xMg xO 3 catalysts decreases with the amount of Mg at least for the catalysts showing a single perovskite phase ( x=0.3). Concerning the CO oxidation, the order of activity for the AFeO 3 materials is Nd>La>Sm, while the activity (per unit SA) of the LaFe 1−xMg xO 3 catalysts decreases at high magnesium content. 相似文献
8.
Defective structures, surface textures, oxygen mobility, oxygen storage capacity (OSC), and redox properties of RE 0.6Zr 0.4O 2 and of RE 0.6Zr 0.4−xY xO 2 (RE=Ce, Pr; x=0, 0.05) solid solutions have been investigated using X-ray diffraction (XRD), temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), O 2−H 2 and O 2−CO titration, 18O/ 16O isotope exchange, CO pulsing reaction, and X-ray photoelectron spectroscopy (XPS) techniques. The effects of doping noble metal onto RE 0.6Zr 0.4−xY xO 2 on oxygen mobility and surface oxygen activities have also been studied. Based on the experimental outcomes, we conclude that: (i) a Pr-based solid solution has better redox behavior than a Ce-based one; (ii) incorporation of yttrium ions in the lattices of CZ and PZ solid solutions could result in an enhancement in oxygen vacancy concentration, Ce 4+/Ce 3+ and Pr 4+/Pr 3+ redox properties, lattice oxygen mobility, and oxygen storage capacity; and (iii) doping the noble metal (Rh, Pt, and Pd) onto RE-based solid solution has positive effect on the properties concerned in this work. 相似文献
9.
We have obtained mass spectra of negative ions produced by rays in artificial air at atmospheric pressure (N 2: 80%, O 2: 20%, H 2O: 20–1500 ppm, CO 2: 0.2–300 ppm, NO, NO 2 0.02 ppm). We observed two main categories: hydrates built on simple ions (O 2−, O 3−, OH −, CO 3−, CO 4−, HCO 3−, NO 2−, NO 3−), hydrates built on complex ions (NO x−, HNO γ, HCO 3−HNO x, x = 2,3; Y = 2, 3). For high values of hygrometry, CO 2 content and ageing time (5 msec) we observe the disappearance of O 2−, O 3−, OH − hydrates whereas the major part of the spectrum consists of complex ions. 相似文献
10.
Preparations and physico-chemical characterizations of NASICON-type compounds in the system Li 1+xAl xA 2−xIV(PO 4) 3 (A IV=Ti or Ge) are described. Ceramics have been fabricated by sol-gel and co-grinding processes for use as ionosensitive membrane for Li + selective electrodes. The structural and electrical characteristics of the pellets have been examined. Solid solutions are obtained with Al/Ti and Al/Ge substitutions in the range 0≤ x≤0·6. A minimum of the rhombohedral c parameter appears for x about 0·1 for both solutions. The grain ionic conductivity has been characterized only in the case of Ge-based compounds. It is related to the carrier concentration and the structural properties of the NASICON covalent skeleton. The results confirm that the Ti-based framework is more calibrated to Li + migration than the Ge-based one. A grain conductivity of 10 −3 S cm −1 is obtained at 25°C in the case of Li 1·3Al 0·3Ti 1·7(PO 4) 3. A total conductivity of about 6×10 −5 S cm −1 is measured on sintered pellets because of grain boundary effects. The use of such ceramics in ISE devices has shown that the most confined unit cell (i.e. in Ge-based materials) is more appropriate for selectivity effect, although it is less conductive.© 相似文献
11.
Niobium-molybdenum disulfide solid solution (Nb xMo 1−xS 2) has been prepared in a dispersed state on gamma alumina. The existence of this solid solution supported on alumina carrier has been proven with the help of EXAFS technique. The catalytic properties of these materials have been studied in hydrogenation and hydrodesulfurization reactions. Interestingly, as already observed for niobium sulfide, the activity of the Nb xMo 1−xS 2 solid solution (HDS of DBT, Ptot=33 bar) is not decreased in the presence of H 2S up to p(H 2S)=200 Torr, at least up to x=0.4. 相似文献
12.
Kinetic studies were made on the polymerization of acrolein initated by potassium peroxodiphosphate (PP) in aqueous solution, in the presence and absence of Ag + ions. The rate of polymerization was found to depend on [M] 3/2 (M = monomer) and was independent of both [PP] and [Ag +]. The overall activation energy was calculated to be 4.8 kcal mol −1. A mechanism involving termination by PO 2-4 radicals is proposed and discussed. 相似文献
13.
Layered -titanate materials, Na xM x/2Ti 1−x/2O 2 (M=Co, Ni and Fe, x=0.2–0.4), were synthesized by flux reactions, and electrical properties of polycrystalline products were measured at 300–800 °C. After sintering at 1250 °C in Ar, all products show n-type thermoelectric behavior. The values of both d.c. conductivity and Seebeck coefficient of polycrystalline Na 0.4Ni 0.2Ti 0.8O 2 were ca. 7×10 3 S/m and ca. −193 μV/K around 700 °C, respectively. The measured thermal conductivity of layered -titanate materials has lower value than conductive oxide materials. It was ca. 1.5 Wm −1 K −1 at 800 °C. The estimated thermoelectric figure-of-merit, Z, of Na 0.4Ni 0.2Ti 0.8O 2 and Na 0.4Co 0.2Ti 0.8O 2 was about 1.9×10 −4 and 1.2×10 −4 K −1 around 700 °C, respectively. 相似文献
14.
To clarify the effect of substitutional electron doping on the thermoelectric figure of merit ( ZT = S2σTκ−1) of Ruddlesden–Popper phase SrO(SrTiO 3) n (or Sr n+1Ti nO 3n+1), measurements were conducted for several thermoelectric parameters, e.g. electrical conductivity ( σ), Seebeck coefficient ( S) and thermal conductivity ( κ), of (Sr 1−xREx) n+1Ti nO 3n+1 ( n = 1 or 2, RE (rare earth): La or Nd, x = 0.05 and 0.1) dense ceramics prepared by a conventional solid-state reaction and hot-pressing technique. Crystal structures of the resultant ceramics were represented as (Sr 1−xREx) n+1 Ti nO 3n+1 evaluated by powder X-ray diffraction followed by the Rietveld analysis. All the ceramics exhibited electrical conductivity and the σ values simply depended on the dopant concentration, indicating that both La 3+ and Nd 3+ ions act as electron donors. The | S| values increased with temperature due to decrease in the chemical potential. Significant reduction of the κ values was observed as compared to cubic-perovskite SrTiO 3. The ZT value increased with temperature and reached 0.15 at 1000 K for (Sr 0.95La 0.05) 3Ti 2O 7. 相似文献
15.
Structural, redox and catalytic deep oxidation properties of LaAl 1−xMn xO 3 ( x=0.0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions prepared by the citrate method and calcined at 1073 K were investigated. XRD analysis showed that all the LaAl 1−xMn xO 3 samples are single phase perovskite-type solid solutions. Particle sizes and surface areas (SA) are in the 280–1180 Å and 4–33 m 2 g −1 ranges, respectively. Redox properties and the content of Mn 4+ were derived from temperature programmed reduction (TPR) with H 2. Two reduction steps are observed by TPR for pure LaMnO 3, the first attributed to the reduction of Mn 4+ to Mn 3+ and the second due to complete reduction of Mn 3+ to Mn 2+. The presence of Al in the LaAl 1−xMn xO 3 solid solutions produces a strong promoting effect on the Mn 4+→Mn 3+ reducibility and inhibits the further reduction to Mn 2+. Both for methane combustion and CO oxidation all Mn-containing perovskites are much more active than LaAlO 3, so pointing to the essential role of the transition metal ion in developing highly active catalysts. Partial dilution with Al appears to enhance the specific activity of Mn sites for methane combustion. 相似文献
16.
Polycrystalline (PbS) 1.14(TaS 2) 2, a misfit layer sulfide, was used as cathodic material for lithium secondary battery. One molar LiClO 4 in propylene carbonate (PC) was used as electrolyte. The cell could be galvanostatic discharged down to x = 4.6 [Li x(PbS) 1.14(TaS 2) 2] when the current density was 65 μA cm −2 and the cell was cycled more than 100 times between 3.5 and 1.5 V at a current density of 260 μA cm −2. Lattice expansion increased linearly with lithium content and was less than that reported for the Li/TaS 2 system. Chemical diffusion coefficients were determined by a modified version of the galvanostatic intermittent titration technique and they were fairly constant in the composition range 0.2 < x < 1, and an average value of 8.1 × 10 −11 cm 2 s −1 was calculated. Sodium intercalation was also accomplished, but the uptake of this ion resulting in a significant lattice expansion compared with that observed for lithium ions. Moreover, a similar dependence of the sodium chemical diffusion coefficient on the composition was observed with an average value of 1.4 × 10 −10 cm 2 s −1, somewhat higher than that of lithium ion. We believe that differences in lattice expansion may be responsible for the differences found in the chemical diffusivity values. 相似文献
17.
The cathodic decomposition of II–VI compound semiconductors A ∂+ B ∂− + 2 −e → A + B 2−solv. was studied by differential reflectance spectroscopy. With this technique the relative reflectivity change Δ R/R of the electrode, which is caused by reaction products deposited on the surface, is measured in situ. In this work the cathodic reduction of ZnO and CdS was investigated in aqueous solution. Since the optical properties of the substrate and the metal atoms, deposited, are quite different, fractions of a monolayer coverage can easily be detected even in the presence of other reactions like hydrogen evolution. For comparison, the deposition of Zn and Cd from ions in solution onto ZnO and CdS, respectively, was also investigated. It is shown, that CdS cannot be reduced in the dark at cathodic potentials down to about −2·5 V vs sce. The deposition of Cd from the lattice is only possible when illuminating the surface with light whose energy is equal to or larger than that of the band gap. 相似文献
18.
The influence of Zn substitution on the densification, microstructure, lattice parameters and electromagnetic properties of planar Z-type hexaferrites, which have stoichiometric composition of Ba 3Co 2(10.8−x)Zn 2xCu 0.4Fe 24O 41, were investigated. The results show that the Zn 2+ substitution has no obvious effect on the densification, but Z-type hexagonal phase can form and demonstrate typical planar anisotropic characteristics of soft magnetic materials ( σr6.20 emu/g) in the range of x0.25. The of lattice parameters of planar a (0.588 nm) and axial c (5.25 nm) remain stable. At the certain temperatures, the sintered hexaferrites with an optimal density of about 4.62 g/cm 3 show better electromagnetic properties for x=0.15 than the samples without Zn 2+ incorporation: initial permeability of about 9.0, cut-off frequency of above 800 MHz, resisitivity of above 3.20 Ω cm and dielectric constant of less than 35. 相似文献
19.
A series of palladium-substituted La 2CuO 4, corresponding to the formula La 2Cu 1 −xPd xO 4 ( x = 0−0.2) were prepared by metal nitrate decomposition in a polyacrylamide gel. This method allows an easy incorporation of palladium in the mixed-oxides, which are formed at moderate temperature with rather high specific areas (13–17 m 2/g). The partial substitution of copper for palladium allows a strong improvement of the three-way catalytic activity, in particular for NO reduction. The light-off temperatures for the conversions of CO, NO and C 3H 6 decreased markedly when increasing the palladium content, the activity of catalysts La 2Cu 0.9Pd 0.1O 4 and La 2Cu 0.8Pd 0.2O 4 being comparable to that of a Pt-Rh/CeO 2–Al 2O 3 catalyst for NO reduction, and higher for CO and C 3H 6 oxidation. All the La2Cu1 − x PdxO4 catalysts are activated under reacting conditions. This activation corresponds to the destruction of the mixed-oxide structure, with formation of reduced Pd0 ions atomically dispersed, surrounded by Cu+ and Cu2+ species on a lanthanum oxycarbonate matrix. This high dispersion state of the two transition metals in various oxidation states is supposed to originate from the initial La2Cu1 −xPdxO4 structure. 相似文献
20.
The electrosorption properties of p-norborn-2-yl phenolate ions in alkaline solutions were investigated by ac polarographic and electrocapillary measurements. Two adsorption regions were found. At low bulk surfactant concentrations the adsorption at the positively charged electrode (−0.2 E −0.6 V) is predominant while at higher surfactant concentrations the adsorption at the negatively charged electrode (−0.6 E −1.0 V) is more pronounced. At E = −0.40 V the adsorption parameters were determined (a ≈ 2; ΔG°A = −32.5 ± 1 kJ mol−1. Between −0.6 E −1.0 V one potential of maximum adsorption for all concentrations does not exist and therefore the adsorption parameters could not be calculated. At E = −0.40 V progressive two-dimensional nucleation with a nucleation order of 3 was observed which corresponds well with the high attraction constant. The electrode reaction S2O2−8 + 2e− → 2 SO2−4 is inhibited by norborn-2-yl phenolate ions in the potential range −0.2 E −0.6 V. In the second potential range of capacity decrease the electrode process is much less retarded. At E = −0.40 V, in a similar manner as described for neutral molecules, a linear dependence of the log ks (ks apparent rate constant) on ln cA and π (π = surface film pressure), respectively, has been found. 相似文献
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