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51.
Yu. Dzyadykevych O. Smiyan 《International Journal of Refractory Metals and Hard Materials》2007,25(5-6):361-366
The results of investigation of initial stage of the tantalum borating as well as the effect of oxygen and hydrogen on it are presented. The scheme of the initial stage of tantalum boron saturation is proposed. 相似文献
52.
The interstitial assemblages of the River Rhine were studied in the Rhinau sector (France). The studied area is located in aVegulated channel of the river, controlled by a hydroelectric dam. Twenty stations were sampled in September 1988. Ten litres of interstitial water were pumped at 50 cm depth in each station using the Bou-Rouch technique. Interstitial waters were poorly oxygenated and the hyporheic fauna had three major characteristics: (1) microcrustaceans were dominant, (2) the insects were rare and (3) the stygofauna was absent. The richest stations were well oxygenated and did not correspond to any particular geomorphological features. These findings contrast with the situation observed on other large European rivers (Rhǒne, Danube) where the interstitial assemblages appear to be locally more diversified and rich in stygofauna. 相似文献
53.
铁锈渣对氧气生产的危害 总被引:2,自引:0,他引:2
介绍铁锈、铁锈渣对氧气生产的危害 ,分析一起因铁锈、铁锈渣引起的氧压机着火而殃及氧气囊燃烧的事故 ,针对分析的原因提出预防措施。 相似文献
54.
An original procedure has been established for estimating the overall volumetric mass transfer coefficient using the oxygen concentration curves resulting from the usual gassing-in and gassing-out method. This procedure was applied to experimental data obtained in a small scale bubble column using both tap water and a coalescence-inhibiting liquid mixture that represents the coalescence behavior of biological media. It is based on the analysis of the characteristics times of the system, including those of the hydrodynamics of the two phases, the sensor dynamics and the system inertia when the gas composition is modified. A numerical procedure was developed to estimate the characteristic time of the system inertia ti, using the assumption that this inertia is nearly independent of superficial gas velocity UG. The calculations confirmed that the optimized ti value was nearly independent of UG and of the coalescence behavior of the liquid phase. Additionally, the resulting KLaL values for tap water were closer to the correlation of Shah et al. [1982. Design parameters estimations for bubble column reactors. A.I.Ch.E. Journal 28, 353-379] than those of other conventional models. Finally, the original procedure was also reported to reduce significantly the square sum deviation between the predicted and the measured oxygen response curves. 相似文献
55.
The Steady radial distribution of chemical species in a wire‐to‐cylinder ozone generator filled with pure oxygen has been computed by applying four different plasma chemistry models of increasing complexity. The most complete model considers ten species (e, O2 +, O2 ?, O3 ?, O?, O2, O2(1Δg), O2(1∑g +), O and O3) and 79 reactions, including ionization by electron impact, electron attachment and detachment, electron-ion recombination, charge transfer, etc. The chemical model is coupled with the electrical model through Poisson's equation. The spatially averaged ozone density has been computed as a function of the current intensity and compared with the experimental values obtained by UV spectroscopy. 相似文献
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59.
Ahmad Nozad Golikand Elaheh Lohrasbi Mohammad Ghannadi Maragheh Mehdi Asgari 《Journal of Applied Electrochemistry》2008,38(6):869-874
The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by
cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms,
polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface
area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The
formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of
a gas diffusion electrode for oxygen reduction reaction. 相似文献
60.
Cathodic processes in the leaching and electrochemistry of covellite in mixed sulfate–chloride media
The cathodic processes that occur on a covellite (CuS) surface in mixed sulfate–chloride solutions in the absence and presence
of copper(II) ions have been studied using potentiostatic transients and cyclic voltammetry at rotating disk electrodes in
the potential range 0.3–0.7 V (versus SHE). This range is relevant to the oxidative leaching of this copper mineral in sulfate
and chloride lixiviants. Variations in the concentrations of sulfate and chloride ions had a small effect on the cathodic
reduction of covellite in the potential range of 0.5–0.3 V, although the presence of chloride ion resulted in a significant
increase in the anodic current on the reverse sweep. On the other hand, addition of copper(II) ions resulted in enhanced cathodic
currents and subsequent anodic currents in both sulfate and chloride solutions due to reduction of covellite to an undefined
reduced copper sulfide species. Reduction of copper(II) to copper(I) ions becomes the preferred cathodic reaction as the concentration
of chloride ions increases, becoming mass transport controlled at a rotating disc electrode at potentials below about 0.4 V.
Potentiostatic measurements at potentials negative to the mixed potential in acidic chloride solutions have shown that reduction
of copper(II) ions is reversible and have been used to estimate the rate of oxidative dissolution of the mineral which value
agrees reasonably well with previously reported leaching rates under similar conditions. Reduction of dissolved oxygen has
been found to be very much slower that that of copper(II) ions under ambient conditions. 相似文献