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.

Oxidation und Aufkohlung hochlegierter Werkstoffe für Crackrohre. Teil 1: Das Oxidationsverhalten in Luft

Abstract: Es wurde das Oxidationsverhalten der Guswerkstoffe 1.4848, 1.4857, 2.4813 und einer 25/20/5-CrNiSi-Versuchsschmelze sowie der Knetwerkstoffe 1.4301 und 1.4841 in trockener synthetischer Luft zwischen 800 und 1300° C untersucht. Nur die Oxidation der Werkstoffe 1.4848 und 1.4841 erfolgte angenahert parabolisch, die der anderen Werkstoffe dagegen nach komplexen Zeitgesetzen. Die Oxidationsgeschwindigkeiten aller Guswerkstoffe sind sehr ahnlich. Es bildet sich eine Schichtenfolge Werkstoff/Cr2O3/MnCr2O4 aus. Die MnCr2O4-Schicht weist deutliche Fe-Gehalte auf. Die Cr2O3-Schicht enthalt besonders nahe der Grenze zum Metall SiO2-Einlagerungen. Oberhalb etwa 1000°C tritt deutliche innere Oxidation des Siliziums auf. Eine Ausnahme macht die 25/20/5-CrNiSi-Versuchsschmelze, die aufgrund ihres hohen Si-Gehaltes stets eine geschlossene SiO2-Schicht zwischen Werkstoff und Cr2O3-Schicht bildet. Der Werkstoff 1.4301 zeigt oberhalb 1050°C ortlich verstarkte Oxidation unter Pustelbildung. Der Werkstoff 1.4841 oxidiert oberhalb 1100°C im feinkornigen Gefugezustand erheblich schneller als im grobkornigen, weil oberhalb dieser Temperatur ein starkes Kornwachstum erfolgt, das die Schutzschichtbildung beeintrachtigt. Die Deckschicht enthalt hohe Gehalte an Eisen und der Cr-Gehalt im Werkstoff an der Grenze Metall/Oxid sinkt mit steigender Temperatur wesentlich starker ab als bei dem grobkornigen 1.4841 und den Guswerkstoffen mit rd. 25% Cr. Unterhalb 1100°C sind die Unterschiede gering, und die Oxidationsrate ist vergleichbar der der Guswerkstoffe. Ein Ubergang von innerer Si-Oxidation zu auserer SiO2-Deckschichtbildung erfolgt bei den Werkstoffen 1.4848 und 1.4841 bei 1100°C in H2-H2O-Gemischen bei Unterschreiten des O2-Partialdrucks des Cr/Cr2O3-Gleichgewichts. Oxidation and Carburization of High Alloyed Materials for Cracking Tubes. Part 1: The Oxidation Behaviour in Air The oxidation behaviour has been studied of cast materials (German Materials Numbers 1.4848, 1.4857, 2.4813), an experimental melt of 25/20/5 CrNiSi steel and wrought materials (German Materials Numbers 1.4301 and 1.4841) in dry synthetic air between 800 and 1300°C. Only the oxidation of the materials 1.4848 and 1.4841 follows an approximately parabolic law, with the other materials more complex kinetic laws are found. The oxidation rates of all the cast materials are rather similar; the scale layers successively formed on the base material are Cr2O3 and MnCr2O4. The latter is characterized by clearly distinguishable iron contents. The Cr2O3 layer contains SiO2 inclusions, in particular near the metal boundary. Above 1000°C internal oxidation of silicon is found. An exception to this is the 25/20/5 CrNiSi experimental melt where, because of the high Si content, a continuous SiO2 layer is formed consistently between base material and Cr2O3 layer. The material 1.4301 exhibits locally increased oxidation at temperatures above 1050°C; in this case oxide nodules are formed. The oxidation rate of material 1.4841 at temperatures above 1100°C is higher for the fine grained than for the coarse grained condition; this phenomenon is attributed to the fact that at these temperatures pronounced grain growth occurs which impairs the formation of a protective layer. The scale layers formed contain considerable amounts of iron and the Cr content in the metal at the metal/oxide boundary decreases at a considerable higher rate with increasing temperature than in the case of the coarse grained material 1.4841 and of the cast materials containing about 25% Cr. Below 1100°C the differences in the behaviour are rather small and the oxidation rate is comparable to that of the cast materials. A transition from internal silicon oxidation to external SiO2 scale formation is found with materials 1.4848 and 1.4841 at 1100°C in H2/H2O mixtures below the partial pressure of oxygen corresponding to the Cr/Cr2O3 equilibrium.

Safe biotechnology (5). Recommendations for safe work with animal and human cell cultures concerning potential human pathogens

Abstract: The benefits of using animal or human cell cultures have been clearly demonstrated in diagnostic and therapeutic research and in their application for manufacturing. Cell cultures serve as a tools for the production of vaccines, receptors, enzymes, monoclonal antibodies and recombinant DNA-derived proteins. They represent an integral part of drug development for which corresponding facilities, equipment and manufacturing processes are required. Although the cells themselves offer no particular risk to workers in laboratories and production areas or to the environment, the cell cultures may be contaminated with viruses, mycoplasma, bacteria, yeast and fungi or might contain endogenous viruses. The containment level for animal and human cells is therefore determined by the risk class of these agents. The history of animal and human cell cultures has proved that they can be handled safely. The recommendations in this publication concern the safe handling of cell cultures (tissue explants, primary cell cultures) and permanent cell lines of animal and human origin. A classification system of safety precautions has been elaborated according to the potential for contamination with the pathogenic agents involved.

Modification of the catalytic properties of a Pd membrane catalyst for direct hydroxylation of benzene to phenol in a double-membrane reactor by sputtering of different catalyst systems

Abstract: The surface of hydrogen-permeable PdCu membranes acting as a catalyst for direct hydroxylation of benzene to phenol in the gas phase in a novel catalytic double-membrane reactor was modified by sputtering on it different catalytic layers with the aim to increase the formation rate and selectivity to phenol. Three different systems are described: a 1 μm thick compact layer of Pd 90 Au 10 (10 wt.% Au), a 5 μm thick compact layer of PdGa (50 at.% Ga) and a thin film of Pd 90 Au 10 deposited on a discontinuous V 2 O 5 layer. The different systems were characterized by SEM, EDX, and mainly in terms of their catalytic properties for benzene hydroxylation. The formation rate and the selectivity to phenol could be increased substantially through the catalytic modification. With a maximum phenol selectivity of 67% at 150 °C and a maximum phenol formation rate of 1.67 × 10 −4 mol h −1 m −2 at 200 °C, PdAu reached the best performance in double-membrane operation mode. PdGa showed even more promising results compared to PdAu in kinetic experiments in co-feed operation mode, but suffers from the very low hydrogen permeability of PdGa which stands against its use as a continuous layer in the catalytic membrane reactor.