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.

Reactors for Microbial Electrobiotechnology

Abstract: From the first electromicrobial experiment to a sophisticated microbial electrochemical process – it all takes place in a reactor. Whereas the reactor design and materials used strongly influence the obtained results, there are no common platforms for MES reactors. This is a critical convention gap, as cross-comparison and benchmarking among MES as well as MES vs. conventional biotechnological processes is needed. Only knowledge driven engineering of MES reactors will pave the way to application and commercialization. In this chapter we first assess the requirements on reactors to be used for bioelectrochemical systems as well as potential losses caused by the reactor design. Subsequently, we compile the main types and designs of reactors used for MES so far, starting from simple H-cells to stirred tank reactors. We conclude with a discussion on the weaknesses and strengths of the existing types of reactors for bioelectrochemical systems that are scored on design criteria and draw conclusions for the future engineering of MES reactors.

Fundamentals of High Temperature Corrosion

Abstract: The sections in this article are Introduction High Temperature Corrosion in Technical Applications High Temperature Corrosion Resistance Fundamentals of Oxidation Stability of the Corrosion Product Formation and Growth of Oxide Scales Initial Stages Defect Chemistry Scale Growth by Solid State Diffusion Scale Growth Controlled by Mechanisms Other than Solid State Diffusion Specific Aspects of Oxide Scale Growth on Alloys Internal Oxidation/Corrosion The Influence of Mechanical Stress on Oxidation Stresses in Oxide Scales Mechanical Scale Failure Healing of Oxide Scale Cracks The Role of Internal Corrosion Chemical Scale Failure Sulfate Induced Hot Corrosion Vanadate Induced Hot Corrosion Corrosion Without the Formation of a Solid Scale Molten Phases as Corrosion Products Volatile Corrosion Products Gas Corrosion by Species Other than Oxygen Carburization and Metal Dusting Internal Carburization Metal Dusting Sulfidation Chlorination Water Vapor Hydrogen Experimental Techniques

Thermal barrier coatings on γ-TiAl protected by the halogen effect

Abstract: Establishing the formation of a thin alumina scale, fluorine-treatment of the surface of γ-TiAl alloys can function as a bond coat in thermal barrier coating (TBC) systems, eliminating problems associated with thickness and chemical compatibility of conventional bond coat types. In the present work, yttria partially stabilized zirconia (YSZ) coatings were deposited on two recently developed γ-TiAl alloys, two-phase TNB-V5 and β-stabilized TNM-B1, using electron-beam physical vapor deposition (EB-PVD). The deposition temperature was 900 °C and 1000 °C. Prior to TBC deposition, the substrate materials were treated with fluorine by dipping in dilute hydrofluoric acid or spraying of an organic fluorine-containing compound, followed, in general, by a pre-oxidation step at 900 °C for 24 h in air. With some of the samples, the latter pre-oxidation step was omitted. As revealed by scanning electron microscopy, the as-deposited zirconia topcoats were tightly adherent to both fluorine treated alloys, regardless of the fluorination technique, the TBC deposition temperature and the pre-oxidation treatment. The oxidation behavior of the coated specimens was determined under cyclic oxidation conditions at 900 °C in air. Cyclic short-term oxidation tests revealed that the pre-oxidation step was crucial to maintain the oxidation protection by the halogen effect after EB-PVD TBC application. Whereas a continuous alumina layer was found beneath the zirconia topcoat on pre-oxidized samples, a mixed layered oxide scale of TiO 2 and Al 2 O 3 formed on specimens without pre-oxidation. When thermally cycled at 900 °C, the TBC system on substrates fluorine-treated by hydrofluoric acid exhibited lifetimes exceeding 500 cycles of 1 h dwell time at high temperature. No spallation of the zirconia topcoat was observed for both TNB-V5 and TNM-B1 alloys. Therefore, YSZ TBCs offer a promising concept to thermally protect γ-TiAl based alloys in combination with the fluorine effect.