DECHEMA

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.

Conductive Geopolymers as Low-Cost Electrode Materials for Microbial Fuel Cells.

Abstract: Geopolymer (GP) inorganic binders have a superior acid resistance compared to conventional cement (e.g., Portland cement, PC) binders, have better microbial compatibility, and are suitable for introducing electrically conductive additives to improve electron and ion transfer properties. In this study, GP-graphite (GPG) composites and PC-graphite (PCG) composites with a graphite content of 1-10 vol % were prepared and characterized. The electrical conductivity percolation threshold of the GPG and PCG composites was around 7 and 8 vol %, respectively. GPG and PCG composites with a graphite content of 8 to 10 vol % were selected as anode electrodes for the electrochemical analysis in two-chamber polarized microbial fuel cells (MFCs). Graphite electrodes were used as the positive control reference material. Geobacter sulfurreducens was used as a biofilm-forming and electroactive model organism for MFC experiments. Compared to the conventional graphite anodes, the anode-respiring biofilms resulted in equal current production on GPG composite anodes, whereas the PCG composites showed a very poor performance. The largest mean value of the measured current densities of a GPG composite used as anodes in MFCs was 380.4 μA cm-2 with a standard deviation of 129.5 μA cm-2. Overall, the best results were obtained with electrodes having a relatively low Ohmic resistance, that is, GPG composites and graphite. The very first approach employing sustainable GPs as a low-cost electrode binder material in an MFC showed promising results with the potential to greatly reduce the production costs of MFCs, which would also increase the feasibility of MFC large-scale applications.

Promotion of the Al2O3-Scale Formation on Ni-Cr-Al Alloys via the Fluorine Effect

Abstract: The halogen effect, which involves the surface enrichment of an alloy with a halogen element to result in improved oxidation resistance, was assessed using model Ni-based Ni–Cr–Al alloys. The alloys studied varied in composition in a manner that produced sub-critical, borderline and protective intrinsic oxidation behaviours from the standpoint of being able to form a continuous Al2O3 scale. Fluorine-ion implantation allowed for a well-defined surface doping of the alloys. It was found that this doping could promote protective Al2O3-scale formation during oxidation at 900 and 1,000 °C in both dry and steam-containing atmospheres. Specifically, the beneficial halogen effect was manifested by lowering the critical Al content in Ni–Cr–Al alloys needed for Al2O3-scale formation.

Untersuchungen über die Bestimmung der Zähigkeit von Bauteilen im Apparatebau durch Messungen an Modellbehältern von praxisähnlicher Größe. Versuche mit Behältern aus Kesselblech H 1 bei Temperaturen −80°C

Abstract: Die Arbeit befast sich mit einem Untersuchungsprogramm des Dechema-Fachausschusses „Werkstoffe fur chemische Apparate”, das versucht, eine Relation zwischen der Zahigkeit als Werkstoffkennwert und dem Zahigkeitsverhalten von Bauteilen zu finden Auf einem Tieftemperaturprufstand werden Modellbehalter bei verschiedenen Temperaturen durch Innendruck bis zum Bersten belastet und dabei die Verformungen eines kompliziert gestalteten Behalterbodens ausgemessen Verformung und Berstdruck in Abhangigkeit von der Temperatur lassen den vorlaufigen Schlus zu, das die Temperatur der beginnenden Versprodung fur solche Bauteile tiefer liegt als die fur den Werkstoff ermittelte Ubergangstemperatur der Kerbschlagzahigkeit Dieses Ergebnis mus jedoch noch durch Versuche mit anderen Werkstoffen und anders gestalteten Bauteilen bestatigt werden Research into the Determination of the Ductility of Structural Elements in Plant Construction by Measurement on Model Vessels of Near Industrial Size— Tests on Boiler Plate Vessels (Kesselblech H 1) at Temperatures Down to −80°C The paper deals with a research program of the Dechema working group “Materials for Chemical Apparatus”, by which an attempt is made to correlate ductility as a characteristic materials property with ductility changes to be expected in structural elements and structures On a low temperature test stand model containers are loaded internally until bursting and the deformations of a container bottom having a complex shape are measured Deformation and bursting pressure vs temperature support the preliminary conclusion that the embrittlement temperature for such structures is lower than the notch toughness transition temperature of the material Corroboration of this finding requires further work with other materials and structures

Oxidation-related life-time assessment using the new ISO standards ISO 21608:2012 and ISO 26146:2012

Abstract: Life-time extrapolation has often been performed based on a parabolic oxidation law. The new standards, ISO 21608 and ISO 26146, aim at determining the actual oxidation rate constant and exponent in order to describe the oxidation behavior as closely as possible to the observed situation. The present paper extends this approach by the kinetics of subsurface zone depletion of the protective scale-forming alloying element (for example, chromium). Four different types of characteristic depletion kinetics are combined with considerations on the minimum amount of chromium necessary to maintain the protective situation in order to define the extrapolation basis for oxidation-related life-time assessment. This approach is applied to experimental data from exposure in simulated coal combustion environments at temperatures of 550–750 °C and exposure times up to 15 000 h. The materials ranged from low-alloy steel to high-alloy austenitic steels and nickel-base alloys. As a result, it is proposed to use data from metallographic investigations rather than mass change data for life-time assessment together with the respective kinetics approaches. Furthermore, it is recommended to base life-time extrapolation on experimental data from tests of at least 10 000 h duration. The investigated materials were categorized with regard to their potential of oxidation-related life-time assessment.