Solubility Of ZnO Research Articles

Zinc oxoacidity properties in molten LiCl-KCl eutectic at 450� C

The solubility of zinc oxide was studied in molten LiCl-KCI eutectic at 450° C. For that purpose, a yttria-stabilized zirconia electrode was employed as a pO2− indicator. The most common calibration methods were reexamined, and it was shown that the ‘weighed additions’ method failed. The ZnO solubility product was determined.

Thermodynamics of aqueous zinc: Standard partial molar heat capacities and volumes of Zn 2+(aq) from 10 to 55°C

The apparent molar heat capacities and volumes of aqueous Zn(ClO 4) 2 have been measured from 10–55°C in a Picker flow microcalorimeter and vibrating tube densimeter. The Guggenheim form of the extended Debye-Hückel equation was fitted to the experimental data, to obtain the following expressions for the standard-state properties from 10–55°C: C p 0(Zn(ClO 4) 2, aq)/JK −1 mol −1 = 3850.8 − 150720 T−190 − 8.4956T (1) and V 0(Zn(ClO 4) 2, aq)/cm 3 mol −1 = 116.65 − 4073 T−190 − 0.050374T . (2) The standard partial molar heat capacities and volumes for Zn 2+(aq) were extrapolated to higher temperatures by employing the Helgeson-Kirkham-Flowers (HKF) equations, amended to include a standardstate correction term. Gibbs energies calculated from the extrapolated heat capacity and volume functions are consistent with limited experimental data for the solubility of ZnO in acidic to near-neutral aqueous solutions at 200–300°C ( bourcier and barnes, 1987).

Solubility of ZnO and hydrolysis of ZnCl2 in KCl melts

An oxide-ion specific electrode has been used to measure the solubility of ZnO in KCl by potentiometric titration of ZnCl2 in KCl with oxide. The solubility product of ZnO was found to be 2.3 × 10–8 mol2 kg–2 at 1073 K. On the addition of ZnCl2 to oxide ion solutions a zincate species was formed, ZnO2–2, with a formation constant of 3 × 10–12 mol3 kg–3. Attempts to isolate K2ZnO2 have been unsuccessful.The effect of HCl on dissolved oxide ion in ZnCl2(33.3 mol.%)–KCl has been studied over the temperature range 733–873 K. Treatment of this salt with HCl yields an oxide concentration of ca. 10–10 mol. kg–1, but this rapidly increases to ca. 10–3 mol kg–1 when the salt is held under argon, through reaction with trace amounts of water in the gas.The equilibrium reaction: H2O(g)+ 2Cl–⇌ 2HCl(g)+ O2– has been studied and the equilibrium constant is given by: log K= 2.514 – 8163/T

Preparation and several properties of ferroelectric powder Pb {(Mg, Zn) [formula omitted]Nb [formula omitted]} (Part 1) : Substitutional solid solubility of ZnO for MgO in perovskite type lead magnesio-niobate

Preparation and several properties of ferroelectric powder Pb {(Mg, Zn) [formula omitted]Nb [formula omitted]} (Part 1) : Substitutional solid solubility of ZnO for MgO in perovskite type lead magnesio-niobate

Preparation and Several Properties of Ferroelectric Powder Pb{(Mg, Zn)<sub>1/3</sub>Nb<sub>2/3</sub>}O<sub>3</sub> (Part 1)

Powders containing perovskite type double oxides of the series Pb(Mg1/3Nb2/3)O3-Pb(Zn1/3Nb2/3)O3 as a main constituent have been prepared by firing the batch mixture according to the chemical formulae. It is interesting to know the substitutional solid solubility of ZnO for MgO in this series because the latter end member Pb(Zn1/3Nb2/3)O3 is known not to be prepared under ordinary firing conditions. The substituted ratio was estimated by the precise determination of lattice constant and its comparison with the Vegard's line. It was shown that MgO in the Pb(Mg1/3Nb2/3)O3 was able to be substituted by ZnO up to 35 or 40mol% depending on the firing temperature (950° or 1100°C). Peak temperature of capacitance (corresponding to Curie point) of the fired disc varied from 0° to 40°C depending on the substitutional ratio of this series. Parallelism between the observed data and the predicted line connecting the Curie points of the end members suggested that the substitution of ZnO for MgO proceeded up to 30-35mol% in this series. However, a certain unbiguity still remained as the observed data at the higher substitutional ratios of the batch mixture were shown to be considerably high. Single crystals of this series were prepared by the “PbO-flux method”. According to the variation of the lattice constant of perovskite type crystal along with the feed composition, it was judged that the homogeneous substitution of ZnO for MgO went up to 30-35mol% in this series. Summarizing the above-mentioned results it has been concluded that the solid solubility of ZnO for MgO in this series is 35±5mol%.

ZINC ELECTRODE CYCLE-LIFE PERFORMANCE IN ALKALINE ELECTROLYTES HAVING REDUCED ZINC SPECIES SOLUBILITY

Electrolytes having 3.5 M hydroxide-ion concentration were tested in 1.35 Ah Zn/NiOOH cells to evaluate their ability to reduce the extent of zinc species migration and slow the rate of cell capacity decline. Alkaline-fluoride and alkaline-borate electrolytes, in which ZnO solubility is approximately 25° of that in standard 7.4 M KOH electrolyte, exhibited 0.09-0.14°/cycle zinc-electrode area loss, which may be compared to a value of 0.46°/cycle observed in standard electrolyte, In addition, no zinc penetration of the separator occurred in cells that employed alkaline-fluoride and alkaline-borate electrolytes, even when zinc-electrode overpotcntials reached 290 mV at the end of charge. Less than 2° of the zinc remaining after cycling was electrochemically inactive.

Stability of Metal Oxide Doped ZnO in Molten Alkali Carbonates

The decomposition of Cr‐doped ZnO and Zr‐doped ZnO in Li2CO3/K2CO3 melts at 923 K under a humidified 30% CO2/air atmosphere was found to occur by different routes, with the relevant equilibrium solubilities in the carbonate melt mitigating the decomposition path. Chromium–doped ZnO undergoes Cr depletion resulting from dissolution of the doped material followed by reprecipitation of a Cr‐depleted ZnO; the Cr remains dissolved as highly soluble chromate. This reaction progresses until Cr equilibrium solubility is met. Zirconium‐doped ZnO shows preferential ZnO solubility, with reprecipitation of ZrO2 and Li2ZrO3.

Mechanism of photoelectrocatalytic dehydrogenation of 2-propanol on a polycrystalline ZnO photoelectrode

The mechanism of photoelectrocatalytic dehydrogenation of 2-propanol on a ZnO photoelectrode is re-examined. The effect of gaseous atmosphere is studied. The change of pH due to the reaction is followed under different experimental conditions. The larger part of the dissolution of ZnO occurs in the dark itself due to the solubility of ZnO. The photodissolution is comparatively small. 2-Propanol inhibits the photocorrosion slightly. H 2O 2 is detected in the electrolyte irrespective of the presence of 2-propanol. An electron transfer process followed by a free radical mechanism for the formation of H 2O 2 is proposed and discussed.

ZnO-PbO-SiO<SUB>2</SUB>系状態図について

The equilibrium diagram of the system ZnO-PbO-SiO2 was studied by the methods of quenching, differential thermal analysis and X-ray diffraction.(1) In the system 2PbO·SiO2-2ZnO·SiO2, a peritectic reaction (melt+2ZnO·SiO2=PbO·ZnO·SiO2) was found at about 13% 2ZnO·SiO2 and 1, 010±5°C. Moreover, an eutectic reaction (melt=2PbO·SiO2+PbO·ZnO·SiO2) existed to about 2% 2 ZnO·SiO2 and 730±3°C.(2) It was found that only the above 2PbO·SiO2-2ZnO·SiO2 system and the compound PbO·ZnO·SiO2 may be considered besides the three respective binary system.(3) The limiting solubility of ZnO in the silica-rich PbO-SiO2 melt determined the silica-saturated eutectic curve in the temperature range of 750 to 1, 300°C.(4) The isothermal lines of the liquidus surface were obtained in the temperature range of 800 to 1, 200°C.(5) Moreover, two ternary eutectic and three ternary peritectic-eutectic points were presumed, thus the equilibrium diagram of the system ZnO-PbO-SiO2 could be established almost completely.

Löslichkeitsprodukte von Metalloxiden und ‐hydroxiden. 10. Mitteilung. Löslichkeitsprodukte von Zinkoxid, Kupferhydroxid und Kupferoxid in Abhängigkeit von Teilchengrösse und molarer Oberfläche. Ein Beitrag zur Thermodynamik von Grenzflächen fest‐flüssig

AbstractThe effect of particle size and molar surface on the solubilities of ZnO, Cu(OH)2 and CuO has been determined at 25° in solutions of a constant ionic strength (0,2) consisting primarily of sodium perchlorate. From the experimental data, the following values for the free enthalpy of the solid‐liquid interface were calculated: equation image .