potential-pH Diagrams Research Articles

The Corrosion Behavior of Technetium Metal Exposed to Aqueous Sulfate and Chloride Solutions

Metal waste forms are being studied as possible disposal forms for technetium and other fission products from spent nuclear fuel. As an initial step in assessing the viability of waste forms, technetium corrosion and passivity behavior was assessed across a broad pH spectrum (pH −1 to pH 13). Measurements indicate that the open circuit potential falls into the region of Tc+7 stability, more noble than the region of presumed passivity. Potentiodynamic polarization tests indicate that the Tc samples are not passive. Both electrochemical results and visual inspection suggest the presence of a nonprotective film. The corrosion rate is relatively independent of pH and low, as measured by linear polarization resistance. No evidence of passivity was observed in the Tc+4 region of the potential-pH diagram following in-situ abrasion, suggesting that Tc does not passivate, regardless of potential.

Microscopic Polarization Behavior of Cerium Sulfide Inclusions in Stainless Steel

Stainless steels suffer from pitting corrosion in chloride environments. Sulfide inclusions such as MnS are known to be preferential sites for pit initiation, and the chemical composition of the inclusions has a significant influence on pitting corrosion behavior. 1–3 CeS inclusions have better pitting corrosion resistance than MnS inclusions.4 However, little is known about the electrochemical properties of CeS inclusions and the relationship between those properties and pitting corrosion resistance. In this study, a microelectrochemical technique was applied to elucidate the electrochemical properties of CeS inclusions. A Ce-added austenitic stainless steel (0.011%C, 0.47%Si, <0.05%Mn, 0.033%P, 0.017%S, 0.01%Cu, 9.41%Ni, 17.90%Cr, <0.01%Mo, <0.005%Al, 0.091%Ce, 0.0042%N, 0.008%O) was prepared by vacuum induction melting and then was hot rolled. This steel was heat-treated at 1373 K for 30 min and then quenched in water. After heat-treatment, the steel surface was polished by diamond paste down to 1 µm. A scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) system was used to ascertain the chemical composition of the inclusion. The SEM image and EDS maps of the inclusion shown in Fig. 1 indicate an enrichment of Ce, Cr, and S, and a small amount of O in the inclusion. The relative atomic percentage of Ce:Cr:S:O was 27:22:45:7, indicating the formation of a mixture of CeS and CrS. This type of inclusions is referred as (Ce,Cr)S in this study. The microscopic potentiodynamic polarization curve was measured in naturally aerated 0.1 M NaCl (pH 5.5) at 298 K. The electrode area was ca.70µm × 70µm. All the potentials reported in this study refer to an Ag/AgCl (3.33 M KCl) electrode. As shown in Fig. 2, meta-stable pitting events were generated around 0.95 V, and small pits were observed at the (Ce,Cr)S/steel matrix boundary. To clarify the dissolution potential range of the (Ce,Cr)S inclusion, microscopic anodic polarization was carried out in naturally aerated 0.1 M Na2SO4 (pH 5.7) at 298 K. The anodic polarization curves are shown in Fig. 2a. The increases in current density observed in the potential range from ca. 0.37 to 0.58 V can be attributed to the dissolution of the (Ce,Cr)S inclusion. Interestingly, the dissolution potential of the (Ce,Cr)S inclusion was significantly lower than the initiation potential of the pitting events at the inclusion. In the case of MnS inclusions 5,6, the pits were initiated in the dissolution potential range of the inclusions. It would appear that the dissolution products such as Ce3+ ions inhibit pit initiation, resulting in the increase of the pit initiation potential. To ascertain the dissolution products from (Ce,Cr)S, the potential-pH diagrams were calculated. Figure 3 shows the potential-pH diagrams for the CeS-H2O and CrS-H2O systems at 298 K. The standard chemical potentials of CeO2 and Ce(OH)3 were obtained from the literature.7 Those of other species used in the calculations were obtained from the HSC thermo-chemical database.8 The experimental conditions of the microscopic anodic polarization are indicated by the slashed regions, which are located in the stable regions of S2O3 2-, Ce3+, CeO2, HCrO4 -, and Cr2O3. Among these species, Ce3+, CeO2, and Cr2O3 are expected to be the factors of the improvement of pitting corrosion resistance. As shown in Fig. 3b, Ce3+ ions were released from the CeS inclusion at lower potentials of the conditions employed in this experiment. It is possible that the Ce3+ ions inhibit corrosion. At the higher potentials, CeO2 is estimated to be deposited on the CeS inclusion and suppress the dissolution of the inclusion. In the case of the CrS-H2O system, Cr2O3 is expected to be formed on the CrS inclusion surface and act as a barrier against the dissolution of the inclusion in the lower potential region. References; 1. I. Muto, Y. Izumiyama, and N. Hara, J. Electrochem. Soc., 154, C439 (2007). 2. I. Muto, S. Kurokawa, and N. Hara, J. Electrochem. Soc., 156, C395 (2009). 3. N. Shimahashi, I. Muto, Y. Sugawara, and N. Hara, J. Electrochem. Soc., 160, C262 (2013). 4. B. Baroux, in Corrosion Mechanisms in Theory and Practice (Third Edition), P. Marcus, Editor, p. 443, CRC Press, Boca Raton (2012). 5. A. Chiba, I. Muto, Y. Sugawara, and N. Hara, J. Electrochem. Soc., 159, C341 (2012). 6. A. Chiba, I. Muto, Y. Sugawara, and N. Hara, J. Electrochem. Soc., 160, C511 (2013). 7. S. A. Hayes, P. Yu, T. J. O’Keefe, M. J. O’Keefe, and J. O. Stoffer, J. Electrochem. Soc., 149, C623 (2002). 8. A. Roine, HSC Chemistry Thermo-chemical Database, Version 6.1, Outotec Research Oy, Pori, Finland (2007). Figure 1

Formation of chukanovite in simulated groundwater containing

ABSTRACTChukanovite (Fe2(OH)2CO3) is one of the secondary mineral precipitates on the surfaces of zero-valent iron (ZVI) barriers in groundwater containing carbonates. Synthesizing experiments were conducted in FeCl2, NaOH, and Na2CO3 solutions to investigate the effect of carbonate concentration on the formation of Fe2(OH)2CO3 and estimate the stability field of Fe2(OH)2CO3 on the potential–pH diagram. Results revealed that Fe2(OH)2CO3 is a unique product based on X-ray diffraction. The , OH−, and Fe2+ concentrations and the ratios (R = [Fe2+]/[OH−] and R′ = []/[OH−]) are important parameters in the formation of the Fe2(OH)2CO3. Fe2(OH)2CO3 was better formed in the R = 1.1, R′ = 0.9 system than in the R = 1.1, R′ = 0.7 system. The crystallization of Fe2(OH)2CO3was increased with the concentration of increased from 0.018 to 0.18 mol/L. The standard Gibbs free energy of the formation of Fe2(OH)2CO3 was −1151.1 ± 5.3 kJ/mol from the equilibrium conditions between Fe2(OH)2CO3 and Fe2+, . Potential–pH diagram of iron, including Fe2(OH)2CO3, was drawn in the Fe–C–H2O system. In this diagram, the stable domain of Fe2(OH)2CO3 was 7.87 < pH < 10.34, −740 mV < Eh < −400 mV, which can be converted into FeCO3 in low pH value in the 0.18mol/L carbonate solution. This work will aid in predicting the potential for mineral precipitation, as well as estimating the reactivity, porosity, and hydraulic performance of ZVI permeable reactive barriers.

Is calomel truly a poison and what happens when it enters the human stomach? A study from the thermodynamic viewpoint

AbstractThe chemical and electrochemical equilibria involving mercurous and mercuric chlorides in the conditions, corresponding to the human stomach environment, were studied from the point of view of chemical thermodynamics. The Gibbs free energies of formation of various mercury and chlorine compounds, the equilibrium constants, and the electrode potentials of reactions involving these compounds at 37°C were calculated. The potential-pH diagrams of

Application of Eh–pH Diagram for Activation of Depressed Chalcopyrite in Cyanidation Tailings

ABSTRACTPotential–pH diagrams for a chalcopyrite–xanthate–H2O and chalcopyrite–NaCN–H2O systems at 298 K were constructed to predict depressing components in the flotation of depressed chalcopyrite in cyanidation tailings using xanthate as a collector. Sodium hypochlorite, hydrogen peroxide, and copper sulfate were used as activators to reduce this depression effect, and the potential–pH diagram for the activator–H2O system was constructed to predict the thermodynamic activating ability. and were dominant in the acidic-to-alkaline region. In alkaline solution, the generation potentials of and were lower than that of CuX. Therefore, they are the main depressing components that influence the flotation of chalcopyrite in cyanidation tailings. In the alkaline region, the oxidative potentials of sodium hypochlorite, hydrogen peroxide, and copper sulfate were significantly higher than that of CN–, so CN– was easily oxidized. This resulted in activation through the loss of hydrophilicity.

Interfacial Reactions in the System of MnTe-H2O

The thermodynamically possible reactions in MnTe-H2O system at room temperature have been studied. The potential–pH diagram has been plotted assuming quasi-equilibrium on interfacial boundary. The possible mechanism of formation and the composition of a surface in dependence on electrode potential and pH have been discussed and the stable conditions for manganese telluride, i.e. the specific area in the diagram (pH from −2 to 14 and potential from −1.5…− 1.1 to −0.9…−0.6 V) have been found. The obtained results may help optimize the conditions for electodeposition of manganese telluride thin films and for liquid chemical etching for the formation of interfacial boundaries.

Extraction of metals from saprolitic laterite ore through pressure hydrochloric-acid selective leaching

In this study, pressure hydrochloric-acid selective leaching was used to leach Ni and Co from saprolitic laterite ore on the basis of potential–pH diagrams constructed for Fe–Si–Cl–H2O and Ni–Si–Cl–H2O systems. The leaching of Ni, Co, Mg, Mn, and Fe was investigated under various conditions. The results showed that the optimal output was obtained under the following conditions: leaching temperature of 150°C, HCl concentration of 350g/L, liquid to solid ratio (l/s) of 1.0, and leaching time of 90min. The saprolitic laterite and leached residue were characterized via X-ray diffraction analysis, infrared spectrometry, and mineral liberation analysis. The related acid leaching mechanism was analyzed based on the results, and the kinetics of the leaching process was discussed. The results of this study suggest that pressure hydrochloric-acid selective leaching is a viable method for efficiently leaching Ni from laterite ores.

Extraction of Vanadium from LD Converter Slag by Pressure Leaching Process with Titanium White Waste Acid

The process of extraction vanadium from LD converter slag by pressure leaching with titanium white waste acid was investigated. The mineralogy analysis indicates that several kinds of spinel containing Fe, V, Ti, Mn and Cr, mainly exist in the converter slag. Potential-pH diagrams of V-Fe-H2O, V-Ti-H2O, V-Mn-H2O, V-Cr-H2O system have been calculated at elevated temperature condition (150 °C). The thermodynamics diagrams show that soluble ions of V and Fe2+, Fe3+, Mn2+, Cr2+ and Cr3+ can be extracted by the acidic leachate during the pressure leaching process. The results of orthogonal experiment reveal that the impacts of temperature and initial acid concentration on the vanadium extraction process are effective. The effect of temperature on the leaching process was further investigated with a increased temperature from 100 °C to 160 °C, and the results indicate that the content of titanium in the residue is 4.56% to about 12.0%, while other elements tend to be enriched in the leaching solution. Under the optimization condition (temperature 140 °C, liquid-solid ratio 10:1, concentration of acid at 200 g·L−1, stirring speed 500 r/min and the reaction time of 90 min), the leaching rate of vanadium is 96.85%.

The mechanism of solution acidification during chemical conversion process on aluminium alloys

In this report, chromate-free conversion coating was produced on aluminium alloy by a solution containing cerium nitrate and potassium permanganate. The pH-potential diagram of cerium nitrate/potassium permanganate system was achieved. It was found that the oxidation of Ce3+ by MnO4− led to the solution acidification. The structure, composition and valence state of conversion coating were characterised. The mechanism of conversion coating formation on aluminium alloy in the solution containing cerium/potassium permanganate was studied.

Nonaqueous Halide-Free Flux Reactions with Tin-Based Solders

New halide-free fluxes are becoming more prevalent in electronic packaging; however, their efficacy and reactive behavior with conventional solders has not been well characterized. In this work, we examine nonaqueous halide-free flux reactions of tin (Sn)-based solder surfaces using electrochemical methods. Cyclic voltammetry was used to study reactions of Sn(II) and Sn(IV) species, x-ray photoelectron spectroscopy (XPS) was used to study surface chemistry, and chronopotentiometry was used to quantify equilibrium constants of Sn–carboxylic complexes. Reactions were investigated using carboxylic acid solutions such as adipic acid or maleic acid in polyethylene glycol. Carboxylic acid-based fluxes are practically inactive toward SnO2 removal at room temperature (25°C); however, some species are capable of removing the oxides at temperatures as high as 180°C and at pH as low as 0.1. XPS results suggest the H+ activity of the carboxylic acid is the key to removing SnO2 on Sn-based solder surfaces. Equilibrium coefficients and potential-pH diagrams are given to elucidate the influence of pH on Sn surfaces.

Electrochemical and Photoelectrochemical Properties of Nano-Islands of Zinc and Niobium Oxides Deposited on Aluminum Thin Film by RF Magnetron Reactive Sputtering

Zinc oxide (ZnO) and niobium oxide (NbOx) with a nano-island structure were deposited by a sputtering method on Al-coated glass substrates. Cells with a (ZnO or NbOx)/Al/glass|KNO3aq.|Al/ glass structure were assembled, and electrochemical and photoelectrochemical properties were evaluated. The ZnO and NbOx electrodes had higher electrode potentials than the counter Al/glass electrode, and electron flows from the counter electrode to the ZnO and NbOx electrodes through the external circuit were commonly confirmed. In the ZnO-based cell, only faint photocurrent generation was seen, where Zn and Al elution from the ZnO electrode was found. In the NbOxbased cell, however, stable generation of electricity was successfully achieved, and electrode corrosion was not recognized even in microscopic observations. A photoelectrochemical conversion model was proposed based on potential-pH diagrams. In the case of nano-island structures formed at shorter NbOx deposition time, it was concluded that the photoelectrochemical reactions, which were proceeded in the immediate vicinity of the boundary among nano-islands, substrate, and electrolyte solution, were predominant for the photoelectrochemical conversion, and in the case of film structures with longer deposition time, the predominant reactions took place at the film surface.

Electrochemical Investigation on the Formation of Cu Nanowires by Electroless Deposition

The growth of copper (Cu) nanowires by electroless deposition in aqueous solution at 60-80 °C was studied from an electrochemical perspective using in situ mixed potential measurements and potential-pH diagrams. Scanning Electron Microscopy (SEM) showed that thick and short nanowires were obtained at high temperatures, while long and thin nanowires result from low reaction temperatures. In situ mixed potential measurements reveal that Cu(II) reduction is more favored at higher reaction temperatures, hastening the reduction reaction. The fast reaction leads to a high concentration of Cu atoms in the solution. As a result, Cu deposition occurs rapidly, such that they attached on both sides and ends of the primary Cu nanowires. This results to the formation of thick and short structures. On the other hand, thin and long nanowires are obtained due to the slow reduction reaction, which gives the Cu atoms more time to orderly attach in a wire-like formation.

ICONE23-1091 AOA AND RADIATION-INDUCED ANOMALOUS CRUD DEPOSITION ON LWR FUELS

In 2006, the author published his research on characteristics of boron co-deposition with crud experienced in AOA and crud deposition anomaly (CDA). These anomalous crud deposition phenomena are contrary to the general theory of mineralogy where hydrothermal growth of crystals was widely used and therefore, the crud should not deposit on fuels where the reactor water is at the highest temperature. Significant quantities of meta-ZrO_2 and nickel iron oxyborates (bonaccordite), notably Ni_2FeBO_5 have also been found in deposits on cores with AOA. On the basis of the general characterization information released by EPRI, the author has constructed a potential-pH diagram of Ni_2FeB(OH)_<10>, which is a hydrated state of FeNi_2(BO_3)O_2. However, the theoretical results were not consistent with the reported phenomenology since the removal of excess electrons is needed for metallic cations (e.g. Fe^<++>, Ni^<++> and Cr^<++>) to deposit as CRUD on the fuel's surface. This indicates that the reactor fuels must be cathodic, thus demonstrating that further investigation of the radiation effects on electrochemical reactions are indispensable. This is the main agenda of this paper. Since the author's last paper the author has confirmed that 'long-cell action' corrosion plays a pivotal role in practically all unresolved corrosion issues for all types of water-cooled reactors. Some of these unresolved issues are IGSCC, PWSCC, AOA and FAC. In conventional corrosion science, established by US NBS in 1958, it is well known that 'long cell action' can seriously accelerate or suppress the local cell corrosion activities. The author believes that the omission of this basic corrosion mechanism is the root cause for practically all un-resolved corrosion issues. The long-cell action corrosion mechanism is induced in water-cooled reactors as demonstrated with potential differences between irradiated- and un-irradiated reactor water. The author recently developed a unified theory, which enables the estimation of redox potential differences induced by radiation. The author's previous calculations through modifying the Nernst equation revealed a reasonable agreement with the published in-pile experimental results when a "fitting parameter" is introduced. Based on these new findings this paper revisits previous E-pH diagrams to investigate the effects of radiation. The Nernst equation, applied to reactor water, determines the actual in-core operational environment with a potential shift from the electrochemical potential due to solute species such as dissolved hydrogen and oxygen in the reactor water.

Effect of pressure on corrosion of Inconel 625 in supercritical water up to 100 MPa with acids or oxygen

The corrosion behavior of Inconel 625 in supercritical water was investigated under high pressure (30–100MPa at 400°C) with the addition of acids (5mmol/kg CH3COOH or 0.5mmol/kg HNO3) or O2 (2.5–250mmol/kg). Ni and Cr ions were the main dissolved metal ions in the effluent. The Ni ion concentration showed no clear dependence on the O2 concentration or pressure in the experiment with O2; the concentration was lower than 0.05ppm. The concentration increased with pressure up to 0.09ppm and 3ppm (at 100MPa) in the experiment with CH3COOH and HNO3, respectively. The Cr ion concentration increased with the O2 concentration and pressure; the maximum value of the concentration was about 0.5ppm. The Cr ion concentration was lower than 0.01ppm in the experiment with CH3COOH, while the concentration was considerably higher in the experiment with HNO3: the concentration increased with pressure up to 0.87ppm at 100MPa. The effect of pressure on the corrosion behavior of Inconel 625 was discussed using potential-pH diagrams, metal oxide solubilities, pH, and equilibrium of ionic reactions. Pressure dependence of the metal ion concentrations was analyzed using a model with water density as a parameter; the log–log plots revealed a linear relationship.

The Electrochemical Behavior of A508III Low Alloy Steel in Simulated Pressurized Water Reactor Primary Water Solutions

The corrosion and electrochemical behavior of A508III low alloy steel in boric acid solutions with or without LiOH at 25 °C and 70 °C were studied by weightloss measurements and electrochemical measurements. Depending on the solution composition and the resultant pH, A508III low alloy steel could be in active dissolution state or in passive state. These results were consistent with the potential-pH diagram. Increasing temperature or boric acid concentration of solutions accelerated the corrosion rates and electrochemical processes. Corrosion rates decreased with the addition of LiOH. Adding LiOH in H3BO3 solutions increased the current densities at relatively high anodic potentials, which had a complex effect on electrochemical impedance spectroscopy.

Microelectrochemical Properties of Ti(C,N) Inclusion of High Strength Martensitic Carbon Steel

High strength carbon steels are anticipated to be used in various fields. However, hydrogen embrittlement is always a big problem for high strength steels.As a result of several treatments to strengthen steel Ti(C,N) inclusions form. Although lots of reports have been conducted to in-steel inclusions such as MnS, little is known about Ti(C,N). Therefore the objective of this study is to look in to the microelectrochemial properties of Ti(C,N) inclusions and its effect on hydrogen embrittlement.Titanium added carbon steel(0.24%C, 1.09%Mn, 0.003%S, 0.03%Ni, 0.16%Cr, 0.028% Ti, 0.031% N) was used as a specimen. The specimen was heat–treated at 1163K for 45minutes and then water-quenched. After that the specimen was kept at 493K for 1hr, and tempered. The specimen was mechanically polished with 1mm diamond paste. Electrochemical measurements were performed in a mixture of 50mM CH3COOH-50mM CH3COONa under naturally aerated conditions. The concentration of the solution above was adjusted to achieve maximum electrical conductivity, and its pH was 4.64.The first step conducted was inclusion characterization. By searching the specimen surface with a SEM, Ti(C,N) inclusions were found to be several micrometers long and several micrometers wide. The color of the inclusion was found to be a red-pinkish color. The color of the inclusion varies from a bright color to a dim color depending on the chemical composition of the inclusion. Basically the more Ti composition the brighter the color is. Compared to a MnS inclusion Ti(C,N) inclusions are hard and are not affected by rolling.Macroscopic polarizations were conducted to determine the macroscopic corrosion behavior of the specimen. Under weak acid conditions the specimen showed an active dissolution as soon as it was anodically polarized. On the other hand, cathodic polarizations showed the potential at which hydrogen started to form. (Fig. 1) This potential is important for determining the effect of Ti(C,N) on hydrogen embrittlement.Microscopic polarizations were conducted to elucidate the electrochemical behavior of Ti(C,N) inclusions. Fig. 2 shows the cathodic polarizations curves of areas around Ti(C,N) inclusions and matrix areas that do not have inclusions in the target area. By comparing the open circuit potentials of the two curves we can see that areas around Ti(C,N) shows a high open circuit potential. By taking into account the potential-pH diagram of Ti(C,N) (Fig. 3) we can confirm that Ti(C,N) inclusions show a stable region in a noble region. Since Ti(C,N) are stable in a high potential, Ti(C,N) are likely to act as preferential cathodic reaction site.

Correlation between Electrocatalytic Oxygen Reduction Reaction and Structure of Mononuclear CuII Complex at Various pH

Introduction Cathode catalysts without using platinum have been extensively investigated over the past several decades for the significance of cost reduction of polymer electrolyte fuel cell.Metallocomplexes is one of prospective non-Pt-based cathode catalysts such as metalloporphyrin and metallophthalocyanin. Bisides these complexes, Cu complexes supported by pyridylalkylamine ligands have recently attracted increasing attention as alternative oxygen reduction catalysts, which are known as a model of some dioxygen-activating enzymes. The Cu complex has the potential to have good oxygen reduction reaction (ORR) activity because some original enzymes such as cytochrome c oxidase (CcO) catalyze oxygen reduction with high efficiency. Although, some studies of the ORR activity of the Cu complexes on an immobilized electrode in an aqueous solution have been reported recently1), the correlation between the ORR activity and the redox property of the CuII/CuI couple of the complex has been unclear. Therefore, it is very important to analyze the relationship between the ORR activity and the redox properties of CuII/CuI of the Cu complexes for the improvement of the ORR performance. In this study, we examined the redox properties of a copper complex, CuII-tmpa [tmpa = tris(2-pyridylmethyl)amine] in a buffer solution at various pH, and investigated its effect on the ORR activity. Experiments The CuII complexes supported by tmpa were synthesized according to the reported procedures2). Voltammograms under quiescent conditions were taken in 10 mM Britton-Robinson buffer solution (CH3COOH, H3PO4, H3BO3, supporting electrolyte: 10 mM Na2SO4) containing 0.3 mM of the copper complex. All measurements in this study were performed using glassy carbon as a working electrode, Pt coil as a counter electrode, and Ag|AgCl|KCl(sat.) as a reference electrode. Results and discussion Figure 1 shows voltammograms of CuII–tmpa under quiescent and oxygen-saturated conditions. The data was displayed versus RHE. The voltammograms show that CuII–tmpa has the ORR activity in a wide range of pH and decreases in overpotential as pH was raised, though the current density was decreased above pH 12.0.CuII–tmpa under argon-saturated conditions showed clear reversible voltammograms of CuII/CuI redox pair, so that we were able to evaluate the redox potential. A potential-pH diagram reveals that a pKa value of CuI species is ca. 12.0. This result suggests that hydroxyl anion coordinates the CuI center in the strong alkaline solution, which causes the catalytic current decrease. We will also discuss about additional results of spectroscopic measurement which support the hypothesis as shown above with respect to the structure of CuII–tmpa. References 1) M. A. Thorseth, C. S. Letko, E. C. M. Tse, T. B. Rauchfuss, A. A, Gewirth, Inorg. Chem. 2013, 52, 6282) Z. Tyeklar, R. R. Jacobson, N. Wei, N. N. Murthy, J. Zubieta, K. D. Karlin, J. Am. Chem. Soc., 1993, 115, 2677

Investigation of Metal-Oxide Co-Electro/Electroless Deposition Method for Co-Ce-O Composite Films by Potential-pH Diagrams

Investigation of Metal-Oxide Co-Electro/Electroless Deposition Method for Co-Ce-O Composite Films by Potential-pH Diagrams

Phase transformation behavior of zinc metastannates obtained by aqueous precipitation at different temperatures

Phase transformation studies in ZnO–SnO2 system from zinc metastannate (ZnSnO3) to zinc orthostannate (Zn2SnO4) with annealing temperature are reported. Non-centrosymmetric oxides show unique symmetry dependent and spontaneous polarization properties, which are technologically important. ZnSnO3 particles were synthesized by a simple aqueous synthesis at low temperatures designed with the assistance of potential–pH diagrams. ZnSnO3 particles synthesized at 4 °C are more porous losing the ilmenite structure upon annealing at 200 °C, while the other samples prepared at higher temperatures (25–65 °C) becomes amorphous at 300 °C. The phase transformation into the inverse spinel orthostannate phase occurs around 750 °C in all the samples.

Facilitated proton transfer or protonated species transfer reactions across oil|water interfaces

The main purpose of this paper is to develop the equations for the half-wave potential of facilitated proton transfer or protonated species transfer across liquid|liquid interfaces, including ion pairing. The main equation developed in this research allows simulating different chemical systems (hydrophilic and hydrophobic neutral base, multiple protonated species, ion-pair formation in the organic phase). Five representative chemical systems are studied in detail in order to demonstrate the usefulness of the equations developed. In addition, the effect of the hydrophilicity of neutral weak bases on the domains of predominance of each species is analysed. Finally, the half-wave potential as a function of the pH obtained using the developed equations, are compared to simulated results and to pH-potential diagram.