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  • absorption  (2)
  • gas scavenging  (2)
  • Al2O3+Cr2O3 coatings  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Influence of a mixed Al2O3+Cr2O3 superficial coating on the non-isothermal oxidation behavior of Fe and Fe-Cr alloys (1992)
    Springer
    Oxidation of metals 37 (1992), S. 95-108 
    Details
    ISSN: 1573-4889
    Keywords: non-isothermal ; oxidation ; Al2O3+Cr2O3 coatings ; Fe, Fe-Cr alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The non-isothermal oxidation behavior of electrolytic-grade iron and Fe-Cr alloys in dry air has been studied using linear heating rates of 6 K/min, 10 K/ min, and 15 K/min up to a final temperature of 1273–1473 K. Some of the iron and iron-chromium alloy samples were given a surface treatment by dipping them in an aqueous solution containing both Cr and Al ions before their oxidation studies. This pretreatment has resulted in improved oxidation resistance and scale adherence as depicted by no scale rupture even after a second thermal cycle. Mass changes were recorded gravimetrically, and scales have been characterized by SEM, EPMA, and x-ray diffraction analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665633
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  • 2
    Electronic Resource
    Electronic Resource
    On the scavenging of SO2 by cloud and raindrops: II. An experimental study of SO2 absorption and desorption for water drops in air (1983)
    Springer
    Journal of atmospheric chemistry 1 (1983), S. 291-306 
    Details
    ISSN: 1573-0662
    Keywords: Acid rain ; convective diffusion equation ; gas desorption ; gas scavenging ; mass transfer ; reversible washout ; sulfur dioxide ; trace gas absorption ; wet deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract For the purpose of testing our previously described theory of SO2 scavenging a laboratory investigation was carried out in the UCLA 33 m long rainshaft. Drops with radii between 250 and 2500 μm were allowed to come to terminal velocity, after which they passed through a chamber of variable length filled with various SO2 concentrations in air. After falling through a gas separating chamber consisting of a fluorocarbon gas the drops were collected and analyzed for their total S content in order to determine the rate of SO 2 absorption. The SO2 concentration in air studied ranged between 1 and 60% (v). Such relatively large concentrations were necessary due to the short times the drops were exposed to SO2 in the present setup. The present experimental results were therefore not used to simulate atmospheric conditions but rather to test our previously derived theory which is applicable to any laboratory or atmospheric condition. Comparison of our studies with the results from our theory applied to our laboratory conditions led to predicted values for the S concentration in the drops which agreed well with those observed if the drops had radii smaller than 500 μm. In order to obtain agreement between predicted and observed S concentrations in larger drops, an empirically derived eddy diffusivity for SO2 in water had to be included in the theory to take into account the effect of turbulent mixing inside such large drops. In a subsequent set of experiments, drops initially saturated with S (IV) were allowed to fall through S-free air to determine the rate of SO 2 desorption. The results of these studies also agreed well with the results of our theoretical model, thus justifying the reversibility assumption made in our theoretical models. In a final set of experiments, the effects of oxidation on SO2 absorption was studied by means of drops containing various amounts of H2O2. For comparable exposure times to SO2, the S concentration in drops with H2O2 was found to be up to 10 times higher than the concentration in drops in which no oxidation occurred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058733
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  • 3
    Electronic Resource
    Electronic Resource
    On the scavenging of gaseous nitrogen compounds by large and small rain drops I. A wind tunnel and theoretical study of the uptake and desorption of NH3 in the presence of CO2 (1995)
    Springer
    Journal of atmospheric chemistry 21 (1995), S. 293-307 
    Details
    ISSN: 1573-0662
    Keywords: Gas scavenging ; ammonia ; absorption ; desorption ; convective diffusion models ; CO2-hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An experimental study has been carried out in the Mainz vertical wind tunnel to determine the rate at which NH3 in the presence of CO2 is absorbed by freely suspended water drops. The experimental uptake rates were found to be in good agreement with the rates predicted by the Kronig-Brink convective diffusion model and, for gas concentrations in the ppbv range also by the model in which it is assumed that the absorbed gas is well mixed inside the drop (henceforth called well mixed model). The same conclusion was shown to apply also to the desorption of NH3 from a drop previously exposed to NH3. The latter result is in contrast to the desorption of SO2 which must be described by a model which accounts for the diffusion of the species inside the drop. Comparison of our experimental results with theory show further that the uptake of NH3 in presence of CO2 is significantly overestimated if the slow reaction CO2(aq)+H2O⇌HCO 3 − +H+ is neglected in the theoretical computation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696760
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  • 4
    Electronic Resource
    Electronic Resource
    On the scavenging of gaseous nitrogen compounds by large and small rain drops: II. Wind tunnel and theoretical studies of the simultaneous uptake of NH3, SO2 and CO2 by water drops (1996)
    Springer
    Journal of atmospheric chemistry 24 (1996), S. 271-284 
    Details
    ISSN: 1573-0662
    Keywords: gas scavenging ; absorption ; sulfur dioxide ; ammonia ; plume washout ; CO2-hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An experimental investigation of the simultaneous absorption of NH3 and SO2 from the ambient atmosphere by freely falling water drops has been carried out in the Mainz vertical wind tunnel. The experimental results were found to be in good agreement with the results derived from computations with the Kronig-Brink convective diffusion model and also with a model which assumes a drop to be well mixed at all times. Encouraged by this agreement, these computation schemes for the uptake of gas by single drops where incorporated in a pollution washout model with realistic SO2, NH3 and CO2 gas profiles. This model allows an entire raindrop size distribution to fall through a gas layer. The results of this ‘plume-model’ show that the SO2 uptake is strongly dependent on the NH3 concentration in the atmosphere and on the rainrate. We also find that the small drops contribute more towards the washout of these gases. In the case of simultaneous presence of NH3 and SO2, desorption of these gases is negligible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210286
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