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.

Sauerstoffaufnahme von Vanadium, Niob und Tantal bei hohen Temperaturen und niedrigen Drücken

Abstract: Es wird eine Ubersicht uber die Sauerstoffaufnahme von Vanadium, Niob und Tantal bei Temperaturen oberhalb von 1000°C und bei Sauerstoffpartialdrucken unterhalb von 10−2 Torr gegeben. Dabei wird die Kinetik der Sauerstofflosung ausfuhrlich behandelt und auf die Oxidation nur kurz eingegangen. Die Ubersicht enthalt eine theoretische Behandlung der Sauerstofflosung. Fernerhin werden quantitative Beziehungen angegeben, die eine Abschatzung der Sauerstofflosung in Vanadium, Niob und Tantal bei gegebenen Bedingungen von Temperatur und Sauerstoffdruck erlauben. Oxygen absorption by vanadium, niobium and tantalum at high temperatures and low pressures A general view is presented of the oxygen absorption by vanadium, niobium and tantalum at temperatures above 1000°C and at oxygen partial pressures below 10−2 torr. In this context the kinetics of oxygen dissolution is given a detailed treatment while oxidation is dealt with but shortly. The review includes a theoretical treatment of oxygen dissolution. In addition quantitative relations are given which enable the oxygen dissolution in vanadium, niobium and tantalum to be estimated at given conditions of temperature and oxygen pressure.

Oxidation Behavior of Intermetallic Titanium Aluminide Alloys

Abstract: Above 750-800°C oxidation becomes a serious life time issue for the new group of intermetallic light-weight high temperature alloys based on titanium aluminides (TiAl). Fast growing titanium oxide competes with protective alumina as a surface scale in the oxidation reaction by which the formation of a slow-growing protective oxide scale is prevented. The key to the development of alloys with sufficient oxidation resistance is the understanding of the thermodynamic and kinetic situation during the oxidation process. The latter is influenced by the type of alloying elements, the Al- and Ti-activities in the alloy, the oxidation temperature and the environment (e.g. dry or humid air, etc.). This paper provides a comprehensive summary of the oxidation mechanisms and the parameters influencing oxide scale formation. Besides the role of metallic alloying elements, the halogen effect will also be discussed. The paper finishes with recent results concerning the prevention of oxidation-induced room temperature embrittlement of TiAl alloys.

Initial Aluminizing Steps of Pure Nickel from Al Micro-Particles

Abstract: Novel, unconventional type of high temperature coating systems can be elaborated by depositing Al micro-particles on nickel base substrates, using an appropriate binder, and converting them into a thermal barrier type coating by a two-step heat treatment under argon. Final result is a coating structure consisting of a quasi-foam top coat, constituted by spherical hollow alumina particles, surmounting a β-NiAl diffusion layer able to form during high-temperature oxidation a protective alumina scale. In this work, pure nickel was employed as a model material to evaluate the effects of moderate temperatures (550-700°C), dwelling times and Al particle size on the final characteristics of the coatings. Almost no diffusion occurred below 600°C. In contrast, a Ni2Al3 layer very quickly formed at 650 or 700°C. The rapidity of coating formation was attributed to the appearance of a liquid phase at the coating/substrate interface. The increase of dwelling time did not provide any significant thickness increase as the Al particles got practically emptied after 2h. In addition, the use of different micro-sized particles resulted in similar Al diffusion coatings under the investigated conditions.

Aktuelle Entwicklungslinien der elektrochemischen Prozeßtechnik

Abstract: Development trends in electrochemical process engineering. Important electrochemical production processes have recently been crucially modified or newly developed and this opened new horizons for the future of industrial electrochemistry. The thrust of this development is discussed in three selected areas: alkali chloride electrolysis, water electrolysis, and organic electrosynthesis. Important past steps are the invention of the dimensionally stable anodes, the development of the cation exchange membrane and membrane electrolysis, the successful testing of zero gap cells, SPE electrolysis and the economic use of two phase electrolytes. These successes have arisen mainly from an improved knowledge and understanding of the fundamental principles of electrochemical engineering.