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Institution

DECHEMA

NonprofitFrankfurt am Main, Germany
About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.
Topics: Corrosion, Oxide, Coating, Alloy, Catalysis


Papers
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Journal ArticleDOI
S. Bengtsson1, I. Bjerles1
TL;DR: In this article, the rate of reaction of dissolved oxygen and sulphite ions in diluted aqueous solutions, which has industrial importance in abatement of air pollution by sulphur dioxide, was investigated in homogeneous and in heterogeneous systems.

37 citations

Journal ArticleDOI
Gerhard Kreysa1
TL;DR: In this paper, a macrokinetic model of three-dimensional electrodes is established by introducing overpotential distribution within the electrode into the microkinetic rate equation and analytical expressions for penetration depth of diffusion limiting cd into bed electrodes are derived for packed and fluidised bed electrodes.

37 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of O2 and substrate (pollutant) concentration on the overall reaction rate of a trickle-bed reactor used for biological waste gas purification was investigated.
Abstract: This paper presents results of experiments on the influence of O2 and substrate (pollutant) concentration on the overall reaction rate of a trickle-bed reactor used for biological waste gas purification. The biocatalyst was a pollutant-specific bacterial monoculture fixed on porous glass carriers. The conversion of acetone and propionaldehyde, as model pollutants that are easily soluble in water, was measured. Under constant hydrodynamic conditions (gas and liquid flow rates) the inlet pollutant concentration was varied. The O2 partial pressure in the model gas was increased to investigate the influence of O2 supply on pollutant conversion. At higher pollutant concentrations (>117 mg acetone.m-3 gas and > 150 mg propionaldehyde.m-3 gas) higher concentrations of dissolved O2 led to a significant rise in the maximum degradation capacity of the reactor. This maximum reaction rate was independent of the pollutant mass flow. It seems that the diffusion of O2 in the biofilm is rate-determining. The reaction rate at lower inlet concentrations was not affected by the improved O2 supply. Here the external mass transfer through the liquid film limits the reaction rate and the maximum separation efficiency of about 80% at a residence time of 1.2s (space velocity 3000h-1) is achieved.

36 citations

Journal ArticleDOI
S. Lederer1, P. Lutz1, Wolfram Fürbeth1
TL;DR: In this paper, a unipolar pulsed DC plasma electrolytic oxidation (PEO) process was used to produce Titanium oxide coatings with a thickness of several micrometers and a porous structure.
Abstract: Titania coatings were produced on Ti 13Zr 13Nb by a unipolar pulsed DC plasma electrolytic oxidation (PEO) process in an electrolyte containing 1 M H2SO4 + 0.1 M H3PO4. The samples were galvanostatically anodized under a constant charge-carrier density of 63 C cm− 2 and current-densities reaching from 14 mA cm− 2 up to 700 mA cm− 2. Both a constant current mode and a unipolar pulsed mode with a duty-cycle of 50% and frequencies of 1 Hz to 50 Hz were performed. The surface layers were characterized by scanning electron microscopy (SEM/EDX), X-ray diffraction (XRD) and nanoindentation. Titanium oxide coatings with a thickness of several micrometers and a porous structure could be generated. The coatings morphology was evaluated. It can be shown that the porosity can be reduced with increasing frequency. The coatings consist of anatase and rutile, the phase composition of the coatings can be adjusted by the PEO current density. The corrosion resistance of the layers was tested in a simulated body fluid (SBF) with the addition of 0.1 M H2O2 by open circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). EIS data fitting indicates a composed layer structure of an outer porous layer and an inner barrier layer. Higher current densities during the PEO process formed thicker coatings, which consequently resulted in lower corrosion currents. The addition of zirconia nanoparticles into the electrolyte increased the surface hardness to an average value of 12.8 GPa, compared to that of an untreated sample (4.1 GPa) and PEO samples without particle addition (8.5 GPa).

36 citations

Journal ArticleDOI
Abstract: Slurry aluminide coatings have been well known for a number of years and are widely used to protect metallic surfaces from oxidation and corrosion. A variety of commercial slurries is available to aluminize the surfaces of nickel-based superalloys, however, they have several disadvantages. They contain environmentally harmful substances such as chromates or halides which are used as binders or to activate the diffusion species. Additionally, up to now slurry coatings were only used to produce precipitate-rich coatings, with a microstructure comparable to high aluminum activity coatings produced by chemical vapor deposition (CVD) like pack cementation. In this work these limitations have been overcome by carefully designing the powder composition of the slurry. Three different nickel-aluminide coatings were developed and applied onto CM-247 nickel-based alloy and Pt-diffused CM-247. By addition of chromium we achieved coatings with a similar microstructure and Al-content (of around 40 at.%), comparable to the state of the art low-activity coatings produced by CVD. Co-deposition of silicon was also achieved in a single step, maintaining the low-activity structure by combining Al–Si powder and chromium. Furthermore, this coating procedure was combined with a platinum electrodeposition step in order to produce single phase Pt-modified low-activity aluminide coatings.

36 citations


Authors

Showing all 760 results

NameH-indexPapersCitations
Wolf B. Frommer10534530918
Michael W. Anderson10180863603
João Rocha93152149472
Martin Muhler7760625850
Michael Hunger6029511370
Ivars Neretnieks442247159
Michael Schütze403436311
Jens Schrader381294239
Roland Dittmeyer312063762
Lei Li291984003
Dirk Holtmann291073033
Lasse Greiner26741994
Klaus-Michael Mangold23571590
A. Rahmel23591967
Gerhard Kreysa22781305
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20231
20227
202145
202053
201949
201844