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Oxygen

About: Oxygen is a research topic. Over the lifetime, 48149 publications have been published within this topic receiving 1113788 citations. The topic is also known as: O & Oxygen.


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Journal ArticleDOI
TL;DR: In this article, the selective oxidation of methane to syngas using a gas-solid reaction was investigated at 850°C, where only small amounts of iron ions could be incorporated into the CeO2 lattice with the superfluous Fe2O3 remaining on the surface of the molecule.
Abstract: CeO2, Fe2O3, Fe2O3/Al2O3 and Ce–Fe mixed oxides with different Ce/Fe ratios were prepared and characterized using XRD, Raman, XPS, and H2–TPR techniques. The selective oxidation of methane to syngas using a gas–solid reaction was investigated at 850 °C. For binary Ce–Fe oxides, only small amounts of iron ions could be incorporated into the CeO2 lattice with the superfluous Fe2O3 remaining on the surface of the molecule. Chemical interactions between surface iron sites and the Ce–Fe solid solution strongly enhanced the reducibility of materials. Methane was found to adsorb and activate on the surface iron sites as carbonaceous species and hydrogen. Carbon deposition was selectively oxidized to CO by the release of activated oxygen from the CeO2 lattice. The activation rate of methane was dependent on the quality of dispersion of surface Fe species, while the oxygen mobility of the material dominated the CO formation rate. Hydrothermally prepared Ce0.7Fe0.3O2−δ showed high activity and selectivity during the successive production of syngas using repetitive redox processes (methane reduction/air re-oxidation). Both the dispersion of surface Fe2O3 and the formation of the Ce–Fe solid solution were enhanced by the redox treatment, which made the oxygen carrier more stable.

173 citations

Journal ArticleDOI
TL;DR: The results point out that this model is able to describe adequately not only oxygen dissolved evolution, but also of the production of xanthan and substrate consumption, and the influence of several parameters (k(L)a, air flow rate and dissolved oxygen) in the evolution of the key compounds of the system.

173 citations

Journal ArticleDOI
TL;DR: It is shown that human biconcave discoidal erythrocytes at 38 and 48°C.
Abstract: The uptake of gases such as oxygen, carbon monoxide, or nitric oxide by the erythrocyte involves: ( a ) diffusion across the cellular membrane, ( b ) intraerythrocytic diffusion, and ( c ) chemical combination with hemoglobin. The aim of this investigation was to obtain data which would permit an analysis of each of these factors in limiting the rate of gas uptake. The initial over-all rate of uptake of gases which combine chemically with hemoglobin to produce a color change can be measured by a modified version of the Hartridge-Roughton-Millikan constant flow, rapid reaction apparatus. If nitric oxide is the reactant gas, only ( a ) and ( b ) are measured since the chemical combination of this gas with hemoglobin is extremely rapid. Our studies have shown that human biconcave discoidal erythrocytes at 38 and 48°C., have the same initial rate of carbon monoxide and nitric oxide uptake as the same cells converted into spherocytes of equal volume. Similarly there was no difference between discs and cells sphered with a 30 per cent increase in volume. Shrunken erythrocytes showed a marked decrease in rate of gas uptake. This suggests that surface area and maximum linear distance for intracellular diffusion of this magnitude do not measurably retard gas uptake. In the shrunken cells, a change in the orientation and concentration of intraerythrocytic hemoglobin and/or of the membrane components may have impeded gas diffusion.

173 citations

Journal ArticleDOI
TL;DR: In this article, the temperature dependence of the Co 2p and O 1s XPS spectra for the cobalt-oxygen system was studied in an oxygen atmosphere of 1 × 10−3 Pa.

173 citations

Journal ArticleDOI
TL;DR: In this article, an investigation was made of tantalum films sputtered in argon containing individual small amounts of nitrogen, methane, and oxygen, and it was shown that the nitrides and carbide have specific resistivities from 200-300×10−6 Ω cm, and temperature coefficients between +3×10 −4 and −2×10 -4 deg−1.
Abstract: An investigation was made of tantalum films sputtered in argon containing individual small amounts of nitrogen, methane, and oxygen. With argon alone, 1000‐A bcc tantalum films deposited on glass substrates heated to 400°C had a specific resistivity four times the bulk value, with the increase attributable to a reactive gas residual pressure of 10−6 to 10−5 Torr. The mixed argon‐nitrogen experiments produced initially hcp Ta2N, and at higher pressures an fcc phase attributed to a new TaN structure. With methane only fcc TaC was obtained, while with oxygen an amorphous phase began to grow initially, and at higher pressures was dominant with a structure identical to anodically formed Ta2O5. The nitrides and carbide have specific resistivities from 200–300×10−6 Ω cm, and temperature coefficients between +3×10−4 and −2×10−4 deg−1. With increasing oxygen content, the specific resistivity increases approximately exponentially; the positive temperature coefficient decreases, becomes zero before the precipitation...

173 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20233,516
20226,670
20211,229
20201,164
20191,190
20181,153