Degree Of Oxygen Deficiency Research Articles

A New Method for the Quantitative Analysis of Silver Oxide Cathodes

A new method based on x‐ray diffraction (XRD), thermogravimetry (TG), and gas chromatography (GC), has been developed for the quantitative analysis of silver oxide cathode materials. This method takes into account (i) the existence of, a newly discovered oxygen deficient phase of silver oxide, and (ii) the occurrence of the solid‐state reverse disproportionation reaction between and Ag to form during the TG procedure. In this analysis procedure we use the general formula, (δ is the degree of oxygen deficiency in ), to represent a mixture of and . The weight fractions of , , and Ag were determined by XRD and that of by XRD and/or GC. The degree of oxygen deficiency, δ, was then determined from TG weight loss data. This new comprehensive analysis method is being used to determine compositional changes (aging) in silver oxide cathodes and to relate the changes to battery performance degradation problems. Oxygen deficiency in is a major cause of the high thermal instability seen in many silver oxide cathodes.

Evidence for an Ag4O3 phase of silver oxide

The structure of chemically and electrochemically prepared AgO materials wa investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy. It was found that chemically prepared (CP) AgO is composed of Ag{sup +} and Ag{sup 3+} ions coordinated with two oxygens at 2.13 {angstrom} and four oxygens at 1.99 {angstrom}, respectively. For electrochemically prepared (EP) AgO, the Ag{sup +} ions are also coordinated with two oxygens at a distance of 2.13 {angstrom}. However, the coordination number for the Ag{sup 3+} ion varies from 2.8 to 3.5 oxygens without any significant change in the coordination distance of 1.99 {angstrom}. That is, EP AgO is really AgO{sub 1{minus}{delta}}, where {delta} is the degree of oxygen deficiency near the Ag{sup 3+} ions. The magnitude of {delta} can be as large as 0.29 {plus minus} 0.05 and is a strong function of preparation procedures. The EXAFS results reveal that a phase of silver oxide, Ag{sub 4}O{sub 3}, is formed electrochemically. The EXAFS results also suggest that the electrochemical oxidation of Ag or Ag{sub 2}O to AgO proceeds via the formation of Ag{sub 4}O{sub 3} as an intermediate step.

Kau Bay, Halmahera, a late quaternary palaeoenvironmental record of a poorly ventilated basin

Kau Bay is a small marine basin in between the two northern arms of the Island of Halmahera (Indonesia), separated from the adjacent Philippine Sea by a sill of 40 m deep. Microfossil and radiocarbon data of piston cores indicate that Kau Bay was a freshwater lake in Weichselian times. At 10 ka BP, the Bay became reconnected with the open ocean. Present-day deep water in Kau Bay is poorly ventilated because the sill limits water exchange with the adjacent ocean. Ventilation occurs through occasional inflow of denser oceanic water, but when this fails oxygen depleted conditions rapidly arise. The permanent presence of oxygen tolerant deep water benthic foraminifers over the past 10 ka indicates that dysoxic conditions prevalied and that anoxic conditions, as observed during the Snellius-I Expedition (May 1930), apparently existed for a short time only and left no trace that could be resolved with our time-resolution of 35 years. Slight and long-term variations in the degree of oxygen deficiency most likely are caused by long-term changes in the density of inflowing oceanic water, possibly in consequence of climatic oscillations. The homothermal surface water of Kau Bay shelters a low-diversity planktonic foraminiferal fauna of primarily shallow-dwelling species. This specific association extends back over the past 8 ka indicating that surface waters remained homothermal over much of the Holocene. Surface water productivity most likely changed with variations in river discharge.

A Possible Mechanism in the High-TcSuperconductivity Reflected on the Photoconductivity

A series of experimental evidences has been recently established on “ the Correlations of Novel Spectral Photoconductivity with Superconductivity ” in the La 2 –Cu 1 –O z , Y 1 –Cu 2 –O z , and Y 3- x –Ba x –Cu 3 –O 9- y systems, which clearly feature the excitons and polarons in the Cu 2 O-like part in these systems with various degrees of oxygen deficiency. On the basis of these results as the silhouette induced by photoexcitation, we propose here a possibility of the realistic mechanism of the formations of pairs and eventually of “ a coherent ensemble of united polarons and excitons ” in the ground state of the high- T c superconductivity. We condense our idea into a term of “ the exciton-mediated bipolarons ”.

Oxygen deficiency and excretion of metabolites by strictly aerobic bacteria

Alcaligenes eutrophus, Pseudomonas acidovorans, Pseudomonas delafieldii and Paracoccus denitrificans excrete metabolites when the oxygen demand of cells is not satisfied. The mechanism by which various metabolites are excreted at different degrees of oxygen deficiency is discussed.

The time factor in fetal distress.

It is obviously clinically impossible to establish how long a fetus in distress can survive except in the few recognized cases where death occurs before delivery is achieved. It is therefore an advantage to resort to theoretical calculations which give good Information about the time factor in fetal hypoxia. It will also be shown from scalp blood measurements that the degree of oxygen deficiency may be estimated.

Effects of Substrate Temperature during RF-Sputtering of Silica on Optical and Chemical Properties, and Re-Emission Coefficient

The optical and chemical properties of rf-sputtered silica films have been investigated as a function of film thickness. As the film thickness increases up to 1500 Å, the deposition rate decreases while the etch rate increases. The peak position of absorption near 9 µm for as-sputtered film shifts toward shorter wavelengths with increasing film thickness. This tendency is also observed in the case of heat-treated film, but peak positions shift by smaller amounts than those of as-sputtered film. The above phenomena are closely related to the substrate temperature during the sputtering. Using the absorption coefficient and half-width of the 9 µm absorption-band, the degree of oxygen deficiency is estimated to be 10%. The re-emission coefficient calculated from the film-thickness-dependence of the deposition rate decreases with increasing sputtering voltage.

The phase diagram and phase transition of the V 2O 3-V 2O 5 system

The insulator-metal transition (IMT) in vanadium dioxide (VO2) which occurs above room temperature (67 °C) is highly sensitive to atomic defects caused by oxygen stoichiometry. The strained growth and the degree of oxygen deficiency in VO2 epitaxial films result in lowering of transition temperature below room temperature as well as the broadening of transition parameters such as transition width and hysteresis width, which limit its application potential. Here we demonstrate the growth of highly oriented strain-relaxed VO2 thin films on (001)-oriented TiO2 substrates at various oxygen partial pressures, exhibiting the narrow transition and hysteresis width. The cross-sectional transmission electron microscopy and x-ray diffraction analyses of the films reveal the highly oriented growth of insulating monoclinic VO2. The IMT parameters associated with temperature-dependent phase transition vary with the oxygen partial pressure used during the deposition. The presence of multiple and mixed valence states of vanadium in the films was confirmed by Raman and XPS analyses. We have achieved a narrow transition width (2.3 °C) and hysteresis width (1.2 °C) through controlling the oxygen stoichiometry during the growth of VO2/TiO2 films.