Oxide Ion Concentration Research Articles

Analysis of structural phase transition behavior of Ln2NiO4 + δ (Ln: Nd, Pr) with variation of oxygen content

The orthorhombic-tetragonal structural phase transition behaviors of Pr2NiO4+δ and Nd2NiO4+δ were investigated by DSC and TG–DTA under controlled oxygen partial pressure, P(O2), and their difference was discussed. A discrete weight variation originating from the variation of oxide ion content, Δδ, was observed during the phase transition in both Pr2NiO4+δ and Nd2NiO4+δ. The Δδ of Pr2NiO4+δ was larger than that of Nd2NiO4+δ, and the Δδ of Pr2NiO4+δ increased with decreasing P(O2), while that of Nd2NiO4+δ was independent on P(O2), suggesting that not only the valence of Ni but also that of Pr changed during the phase transition in Pr2NiO4+δ.

Potentiometric Titration of ${\rm NH}_{4}{\rm VO}_{3}$ and ${\rm Na}_{2}{\rm HAsO}_{4}$ in Molten ${\rm NaNO}_{3}$ at 623 K Using a Novel Solid-State Glass/${\rm Nb}_{2}{\rm O}_{5}$ pH Indicator Electrode

A solid state glass/ Nb2O5 electrode was prepared by the sol-gel process using the sonocatalytic method. The film reported here was prepared from an NbCl5 as precursor and butanol as solvent. The relation between log [O2-] and glass/ Nb2O5 electrode potential in molten KNO3 at 623 K is linear with a slope of 59.1 mV at 623 K. This value is closer to the theoretical value 2.303 RT/F (61.6 mV at 623 K). The standard potential of this electrode, E0, is computed as -984.7 mV relative to the Ag/Ag reference. The electrode was investigated as an oxide ion indicator electrode in potentiometric titrations between acids and bases in fused salts. This electrode behaves reversibly and responds to the oxide ion concentration in molten nitrate. Two oxide ion acceptors (acids), NH4VO3 and Na2HAsO4, were titrated with oxide ion donors (bases) in fused KNO3 at 625 K. The electrode was found to serve as an excellent indicator for acid base potentiometric titrations in molten salts.

Evidence of variation of oxide ion content in structural phase transition of Ba2Fe2O5+δ observed by simultaneous TG-DTA-MS measurements

The structural phase transition of Ba2Fe2O5+δ from monoclinic to cubic in a N2 atmosphere has been analyzed using simultaneous thermogravimetry-differential thermal analysis and mass spectroscopy (TG-DTA-MS). It has been confirmed that the structural phase transition is reversible, of the first order, endothermic, and involves a mass increase with increasing temperature. From the mass spectrometry, direct evidence that the origin of the mass variation in the phase transition is the variation of oxygen nonstoichiometry has been obtained. From the simultaneously observed TG curves, the variation of δ for the transition from the monoclinic phase to the cubic phase has been evaluated to be about 0.008.

Exhaled breath condensate nitric oxide end products and pH in controlled asthma

ObjectivesAsthma imposes a growing burden on the society in terms of morbidity, quality of life, and healthcare costs. It has the highest morbidity amongst inflammatory lung diseases and its prevalence continues to increase over the world. Inquiry into recent day or nighttime symptoms alone underestimates the burden of asthma and may lead to inadequate treatment of asthma. The aim of the present work is to evaluate the role of nitric oxide (NO) and hydrogen ion concentration (pH) levels in exhaled breath condensate (EBC) in cases of controlled bronchial asthma. Patients and methodsThe present study was conducted on 49 controlled asthmatic patients and 12 control subjects. All patients were subjected to thorough history taking, complete clinical examination and plain postero-anterior chest X-ray. All asthmatics and control subjects were subjected to routine laboratory investigations, spirometric study, EBC collection, processing and analysis for its content of both nitric oxide end products: nitrite and nitrate (NOx) and pH. ResultsAll asthmatics represented Group IT which was further divided into Group Ia: 34 patients on regular inhaled corticosteroid (ICS) therapy and Group Ib: 15 patients on no regular therapy. The control subjects represented Group II. The forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1/FVC, peak expiratory flow rate (PEFR) and forced expiratory flow during the middle portion of a forced expiration (FEF 25–75%) were significantly lower in asthmatics than control subjects. The EBC-NOx mean±SD in μmol/L in Group IT (5.99±1.63), in Group Ia (5.27±1.26) and in Group Ib (7.63±1.15) were significantly higher than in Group II (3.66±0.67) with, respectively (p=0.000), (p=0.000) and (p=0.000); and was significantly higher in Group Ib than Group Ia (p=0.000). The EBC-pH mean±SD in Group IT (7.32±0.27), in Group Ia (7.35±0.25) and in Group Ib (7.27±0.3) were significantly lower than in Group II (7.82±0.09) with, respectively (p=0.000), (p=0.000) and (p=0.000); with no significant difference between Group Ia and Group Ib. The EBC-NOx was significantly directly correlated to eosinophils count (p=0.017) and neutrophils count (p=0.002); and inversely correlated to FEV1 (p=0.016), FEV1/FVC (p=0.001), PEFR (p=0.030) and EBC-pH (p=0.003). The EBC-pH was significantly inversely correlated to eosinophils count (p=0.017) and neutrophils count (p=0.036); and directly correlated to FVC (p=0.004), FEV1 (p=0.004) and PEFR (p=0.000). ConclusionEBC-NOx is significantly higher and EBC-pH is significantly lower in asthmatic patients than in control subjects. Asthmatics receiving ICS have a lower EBC-NOx level than those not. EBC-NOx and EBC-pH were significantly correlated and both of them showed significant correlations with spirometric parameters of airway obstruction.

Protective effect of telmisartan against cadmium-induced nephrotoxicity in mice

AimsTo investigate the nephroprotective effect of telmisartan, the angiotensin II receptor antagonist, against renal injury induced by cadmium in mice. Main methodsMice received cadmium chloride at a dose of 1.2mg Cd/kg/day, s.c., for nine weeks. Telmisartan treatment (1mg/kg/day, orally) was started one week before cadmium administration and continued for ten weeks. Key findingsTelmisartan significantly reduced blood urea nitrogen (BUN) and serum creatinine levels which were increased by cadmium. Also, telmisartan significantly suppressed lipid peroxidation, compensated deficits in the antioxidant defenses [reduced glutathione (GSH) level and catalase activity], decreased the elevations of tumor necrosis factor-α (TNF-α), nitric oxide (NO) and cadmium ion concentration, and attenuated the reductions of selenium and zinc ions in renal tissue resulted from cadmium administration. Histopathological examination revealed that cadmium-induced renal tissue damage was ameliorated by telmisartan treatment. Immunohistochemical analysis revealed that telmisartan significantly decreased the cadmium-induced overexpression of inducible nitric oxide synthase (iNOS), nuclear factor-κB (NF-κB), Fas ligand (FasL) and caspase-3 in renal tissue. SignificanceTelmisartan, through its antioxidant and anti-inflammatory actions, effectively prevented cadmium nephrotoxicity in mice. Hence, telmisartan represents a potential candidate to protect the kidney from the detrimental effect of cadmium toxicity.

On luminescence properties of CsI crystals scavenged by Mg 2+

Features of radioluminescence spectra and scintillation light decay curves of CsI crystals grown from the melt preliminarily scavenged by different amounts of Mg 2+ (MgCl 2) are reported. The scintillation light of CsI usually contains 3 components with the decay time constants equal to 7 ns (I), 30 ns (II) and 2 μs (III). The addition of Mg 2+ amount equivalent to the total concentration of oxide ions in molten CsI results in complete destruction of carbonate and sulfate ions. This is confirmed by the disappearance of 370–550 nm band in the radioluminescence spectrum of CsI crystal; thereat the fraction of component III in CsI scintillation light decreases. The excessive in relation to O 2− concentration amounts of Mg 2+ lead to the decrease of O 2− equilibrium molality in CsI melt from 10 − 3 to 10 −10 mol kg − 1 . That causes a considerable increase of fraction of component I as compared with component II from 0.63:0.35 to 0.88:0.07. The fraction of the slow component III approaches the minimum at the equivalent ratio of initial molalities of Mg 2+ and O 2−.

High temperature mapping of surface electrolyte oxide concentration in solid oxide fuel cells with vibrational Raman spectroscopy

Experiments described in this work employ Raman spectroscopy and electrochemical impedance spectroscopy (EIS) to characterize the properties of a YSZ electrolyte in situ at 715 °C and under electrochemical potential control. The YSZ itself is the electrolyte in a functioning, electrolyte supported SOFC membrane electrode assembly (MEA). Experiments measure the changes in surface chemistry of the YSZ as a function of through-cell overpotential, and experiments are designed to identify what role—if any—surface reduced YSZ plays in electrochemical oxidation and charge transfer. Raman spectra show that the change in YSZ from fully oxidized to surface reduced is reversible and happens on a timescale of minutes at these temperatures. Spatially resolved experiments carried out with polarized cells show that the oxide ion concentration near the three phase boundary (TPB) is depleted even further when an overpotential is applied. The change in relative oxide concentration with respect to overpotential is also reversible. EIS measurements probing lateral impedance across the electrolyte surface show that the surface reduced phase has a lower polarization resistance (Rpol) as through-cell overpotential increases. Results are discussed in terms of reduced resistance to processes involving charge and mass transfer reactions specific to the reduced YSZ surface state.

Coenzyme Q10 treatment ameliorates acute cisplatin nephrotoxicity in mice

The nephroprotective effect of coenzyme Q10 was investigated in mice with acute renal injury induced by a single i.p. injection of cisplatin (5 mg/kg). Coenzyme Q10 treatment (10 mg/kg/day, i.p.) was applied for 6 consecutive days, starting 1 day before cisplatin administration. Coenzyme Q10 significantly reduced blood urea nitrogen and serum creatinine levels which were increased by cisplatin. Coenzyme Q10 significantly compensated deficits in the antioxidant defense mechanisms (reduced glutathione level and superoxide dismutase activity), suppressed lipid peroxidation, decreased the elevations of tumor necrosis factor-α, nitric oxide and platinum ion concentration, and attenuated the reductions of selenium and zinc ions in renal tissue resulted from cisplatin administration. Also, histopathological renal tissue damage mediated by cisplatin was ameliorated by coenzyme Q10 treatment. Immunohistochemical analysis revealed that coenzyme Q10 significantly decreased the cisplatin-induced overexpression of inducible nitric oxide synthase, nuclear factor-κB, caspase-3 and p53 in renal tissue. It was concluded that coenzyme Q10 represents a potential therapeutic option to protect against acute cisplatin nephrotoxicity commonly encountered in clinical practice.

Oxide Ion Conduction in the Perovskite-type LaYO3 Doped with ZrO2

In order to find a new type of oxide ion conductor, the electrical conduction was measured in the substituted perovskite-type oxides. In the present case, LaYO3 was used as a based material with an orthorhombic and comparatively large unit cell, and a novel substitution method was introduced to intend to increase the concentration of oxide ions, e.g., LaY1−xZrxO3+x/2. As a result, the LaYO3-based perovskite-type solid solution was found to be formed, where the enhanced oxide ion conduction was observed as compared with that of the based material. A typical sample was LaY0.95Zr0.05O3.025, the ionic conduction of which was 1.2×10−2 S cm−1 at 1000°C. Another substitution method of La1−xZrxYO3+x/2 resulted in the analogous result. Considering these results and the further structural and density measurements, the charge carriers in these phases were expected to be due to interstitial oxide ions.

Raman spectroscopy studies of apatite-type germanate oxide ion conductors: correlation with interstitial oxide ion location and conduction

A Raman spectroscopy study of the apatite series La8+xBa2−x(GeO4)6O2+x/2 is presented. The results show the presence of a new Raman band appearing at ∼645 cm−1, whose intensity increases with increasing interstitial oxide ion content. This new band is also observed in samples containing cation vacancies, consistent with previous suggestions that the presence of cation vacancies enhances Frenkel-type defect formation. The fact that the new band is in the stretching region of the spectra, rather than the bending region as observed for the silicate analogues, is consistent with the interstitial oxide ions being more closely associated with the Ge. This band is attributed to the presence of interstitial oxide ions leading to the formation of five coordinate Ge, in agreement with recent neutron diffraction and modelling studies. From the observation of a reduction in the intensity of this band with increasing temperature, it is suggested that the activation energy for conduction in these apatite germanates is a combination of the energy to “free” the interstitial oxide ions from the five coordinate Ge, and the energy for their subsequent migration. The former process is ascribed to the observed reduction in Raman intensity with an activation energy of 0.32 ± 0.06 eV. Thus the higher activation energy for the germanate apatites over the related silicates can be ascribed to the defect trapping associated with the closer association of the interstitial oxide ion with the tetrahedra in the former.

Formation of apatite oxynitrides by the reaction between apatite-type oxide ion conductors, La 8+xSr 2−x(Si/Ge) 6O 26+x/2, and ammonia

Following growing interest in the use of ammonia as a fuel in solid oxide fuel cells (SOFCs), we have investigated the possible reaction between the apatite silicate/germanate electrolytes, La 8+ x Sr 2− x (Si/Ge) 6O 26+ x /2, and NH 3 gas. We examine how the composition of the apatite phase affects the reaction with ammonia. For the silicate series, the results showed a small degree of N incorporation at 600 °C, while at higher temperatures (800 °C), substantial N incorporation was observed. For the germanate series, partial decomposition was observed after heating in ammonia at 800 °C, while at the lower temperature (600 °C), significant N incorporation was observed. For both series, the N content in the resulting apatite oxynitride was shown to increase with increasing interstitial oxide ion content ( x/2) in the starting oxide. The results suggest that the driving force for the nitridation process is to remove the interstitial anion content, such that for the silicates the total anion (O+N) content in the oxynitrides approximates to 26.0, the value for an anion stoichiometric apatite. For the germanates, lower total anion contents are observed in some cases, consistent with the ability of the germanates to accommodate anion vacancies. The removal of the mobile interstitial oxide ions on nitridation suggests problems with the use of apatite-type electrolytes in SOFCs utilising NH 3 at elevated temperatures.

Effect of oxide ions on separation factors of actinides from lanthanides in reductive extraction

Abstract The distribution coefficients of Am, Ce, and Eu between the salt and metal phases were measured at 1073 K in a reductive extraction system of equimolar NaCl-KCl melt and liquid Ga. By changing the solute concentrations, it was observed that the distribution coefficients were dependent on the oxide ion concentration in the system, possibly due to the formation of such compounds as AmO+. In addition, the mass balance of Am was possibly affected by the formation and precipitation of its oxychlorides and/or oxides in some runs. Taking these observations into consideration, the separation factor between Am and Ce was found to be around 30 in the present system.

An investigation of the high temperature reaction between the apatiteoxide ion conductor La9.33Si6O26and NH3

There is growing interest in the use of ammonia as a fuel in Solid Oxide Fuel Cells (SOFCs). However, the possible reaction between the electrolyte and ammonia, and its potential effect on performance, has received little attention. In this paper, we report an investigation of the high temperature (950 °C) reaction of the apatite-type oxide ion conductor, La9.33Si6O26, and ammonia. The results show that such treatment leads to nitridation of the sample, with evidence for Si loss leading to an increased La:Si ratio in the final product. From neutron diffraction studies, the composition of the final product was determined to be La9.7(1)Si6O22.6(2)N2.7(2), with structural and 29Si NMR data suggesting the presence of N both within the apatite anion channels, and bonded to Si. An interesting feature of the structural studies are the relatively low atomic displacement parameters compared to the comparable apatite oxide systems, La9.33 + xSi6O26 + 3x/2, which can be related to the lack of interstitial anions in the oxynitride. Further studies on samples heated in ammonia at lower temperatures (600, 800 °C) suggest lower N incorporation, particularly for the 600 °C treatment. Considering the correlation of ionic conductivity, and interstitial oxide ion content in apatite systems, the data suggests the potential use of apatite-type electrolytes in SOFCs utilising NH3 as the fuel should be limited to temperatures <800 °C.

Separation Factor of Americium from Cerium in Molten Chloride-Liquid Gallium Reductive Extraction System

The distribution coefficients of Am and Ce were measured in the eutectic LiCl-KCl/liquid Ga system at 773K. By using ZrCl4 as the oxide ion scavenger in order to avoid the formation of such oxychlorides as MO(n−2)+, the effect of oxide ion concentration was well controlled on the distribution coefficients of Am and Ce. The separation factor between Am and Ce was then obtained to be about 100. By comparing the present value with the other experimental and the predicted ones, it was confirmed that the Ga system was more selective than the Bi and Cd system.

Effect of oxygen content on the 29Si NMR, Raman spectra and oxide ion conductivity of the apatite series, La8+xSr2−x(SiO4)6O2+x/2

29Si NMR data have been recorded for the apatite series La8+xSr2-x(SiO4)6O2+x/2 (0 < or = x < or = 1.0). For x = 0, a single NMR peak is observed at a chemical shift of approximately -77 ppm, while as the La : Sr ratio and hence interstitial oxygen content is increased, a second peak at a chemical shift of approximately -80 ppm is observed, which has been attributed to silicate groups neighbouring interstitial oxide ions. An increase in the intensity of this second peak is observed with increasing x, consistent with an increase in interstitial oxide ion content, and the data are used to estimate the level of interstitial oxide ions, and hence Frenkel-type disorder in these materials. The increase in second 29Si NMR peak intensity/interstitial oxide ion content is also shown to correlate with an increase in conductivity. The effect of interstitial oxygen content can also be studied by means of Raman spectroscopy, with a new mode at 360 cm(-1) appearing for samples with x > 0 in the symmetric bending mode energy region of the SiO4 group. The intensity of this mode increases with increasing oxygen content, yielding results comparable to those from the NMR studies, showing the complementarities of the two techniques.

Titration of Potentiometric NH4VO3, KH2PO4, K2HPO4, and their Mixture in Molten NaNO3 at 350°C Using a Novel Solid‐State Glass/TiO2 pH Indicator Electrode

A solid‐state Glass/TiO2 electrode was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten nitrate. NH4VO3, KH2PO4, K2HPO4, and their mixture were titrated with Na2O2 at 350°C using the glass/TiO2 electrode in molten NaNO3.

Potentiometric Titration of Na2HAsO4, NaPO3, Na4P2O7, and their Binary Mixtures in NaNO3 Melt at 350°C Using a Novel Solid State Glass/TiO2 as pH Indicator Electrode

A solid‐state glass/TiO2 electrode was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten NaNO3 · Na2HAsO4, NaPO3, Na4P2O7, and their binary mixtures were potentiometrically titrated with Na2O2 as titrants in molten NaNO3 at 350°C, using the above mentioned indicator electrode.

Development of a Novel Solid‐State pH Sensor Electrode Based on Titanium Oxide Thin Film as an Indicator Electrode in Potentiometric Acid‐Base Titrations in Fused NaNO3 at 350°C

A solid‐state pH sensor was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. The sensor slope was found to increase as the temperature of the solution was increased. The performance of the sensor was investigated in the pH range from 2.2 to 11.19. The E‐pH curve is linear with slope of 0.054 V at 298.15 K. This value is closed to the theoretical value 2.303RT/F (0.059 V at 298.15). The standard potential of this electrode, E°, is computed as 177.58 mV with respect to the SCE as reference electrode. Results obtained by the suggested sensor compares very well with conventional pH electrodes where the square of the correlation coefficient was 0.998. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten NaNO3. K2Cr2O7 was potentiometrically titrated with Na2O2 and K2CO3 as titrants in molten NaNO3 at 350°C, using the above mentioned indicator electrodes. An acidity/basicity scale of the oxyanions was established in molten NaNO3 at 350°C.

Thermodynamic brønsted basicity of clean MgO surfaces determined by their deprotonation ability: Role of Mg 2+–O 2− pairs

The deprotonation ability of clean (i.e., carbonate- and hydroxyl-free) MgO surfaces of various morphologies towards protic molecules, such as propyne and methanol, is evaluated by following the adsorption modes and amount of dissociated species by FTIR. Photoluminescence is used to identify the nature of the oxide ions involved in deprotonation. The same trend is observed for propyne and methanol: (i) the amount of dissociated species increases with the relative concentration of oxide ions of low coordination O LC 2−, (ii) Mg LC 2+ also are involved in deprotonation. Only ∼0.5% of O LC 2− are implied in propyne deprotonation. Quantitative adsorption and IR measurements suggest that the deprotonating Mg 2+O 2− pairs involve 3- and 4- coordinated ions: Mg 3CO 4C and Mg 4CO 3C. The pairs able to lead to deprotonation have to combine a strong Brønsted basic site O LC 2−, able to abstract a proton and a strong acidic Lewis site able to stabilize the anion generated by deprotonation. The deprotonation equilibrium position is related to the thermodynamic Brønsted basicity. The choice of protic molecules used to identify the catalytically active basic sites was justified a posteriori by the correlation between the relative amount of dissociated propyne and methanol species and the catalytic conversion of 2-methylbut-3-yn-2-ol (MBOH).

Solubilities of zinc oxide and cadmium oxide in KCl-LiCl eutectic melts

ZnO solubility (pP = 4.77 ± 0.1) and CdO solubility (pP = 1.46 ± 0.1) in KCl-LiCl melts at 700°C are determined using the sequential additions method with the potentiometric control of the equilibrium oxide ion concentration. Cadmium oxide is a strong base; it fully dissociates in unsaturated solutions. Zinc oxide is a weak base (pKZnO = 2.89 ± 0.15). As the acidic properties of an ionic solvent strengthen with a fixed anionic composition, the solubilities of the oxides increase in correlation with their basicity index; the surface energy at the interface between the solid oxide and ionic melt decreases in association.