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.

Mechanical Stability Diagrams for Thermal Barrier Coating Systems

Abstract: Loss of mechanical integrity due to thermal aging and subsequent spallation of the ceramic top layer is one of the dominant failure mechanisms in thermal barrier coating systems. In order to predict and avoid such mechanical failure, a strain-based lifetime assessment model is presented for a novel double-layer thermal barrier system. The investigated ceramic system consists of a gadolinium zirconate layer on top of a layer of yttria-stabilized zirconia prepared by atmospheric plasma spraying. The mechanical stability diagrams generated by the model delineate areas of safe operation from areas where mechanical damage of the thermal barrier coating becomes imminent. Intensive ceramographic inspection is used to investigate the defect growth kinetics in the ceramic top coat after isothermal exposure. Four-point bending experiments with in situ acoustic emission measurement are utilized to determine the critical strain to failure. The results are then used to generate mechanical stability diagrams for the thermal barrier coatings. From these diagrams, it becomes evident that the gadolinium zirconate layer has significantly lower strain tolerance than the yttria-stabilized zirconia. However, the underlying yttria-stabilized zirconia layer will provide some thermal protection even when the gadolinium zirconate layer has failed.

Des Zeitstandverhalten von Werkstoffen und seine Beeinflussung durch Korrosion

Abstract: Im Hinblick auf die Bedeutung, die dem Zeitstandverhalten der Werkstoffe fur die Dimensionierung chemischer Apparate zukommt, wird zunachst der technische Begriff „Zeitstandfestigkeit” und die davon abgeleiteten mechanischen Guteziffern erklart. Anschliesend werden die Verfahren zur Prufung des Zeitstandverhaltens erlautert und typische, an NE-Metall- und Kunststoffproben erhaltene Versuchsergebnisse wiedergegeben und diskutiert. Abschliesend wird uber den grundsatzlichen Einflus einer gleichzeitigen Einwirkung anorganischer Medien auf das Zeitstandverhalten von Kunststoffen (Resistenzfaktor) berichtet. The creep strength of materials, and how it is affected by corrosion In view of the importance of the creep strength of materials in regard to the design of chemical apparatus, an explanation is first given of the technical notion of „creep strength” and of the mechanical quality indices derived from it. This is followed by a description of creep strength test methods and a discussion of typical test results obtained from nonferrous metals and plastics specimens. The paper is concluded by a report on the influence, in principle, of a simultaneous effect of inorganic media on the creep strength of plastics (resistance factor).

Behaviour of NiAl APS‐coatings in chlorine‐containing atmospheres

Abstract: Due to their thermal expansion coefficient being close to those of ferritic steels, NiAl atmospheric plasma spraying (APS)-coatings have been chosen to be tested in chloridizing atmosphere. A new type of quasi-stability diagram which couples thermodynamic and kinetic approaches was developed to define the stability domains of the pure metals aluminium and nickel in dynamic chlorine- and oxygen-containing atmospheres. NiAl APS-coatings (300 µm) with low porosity on steels were applied and tested in an atmosphere containing 0.2 v/o chlorine and 3 ppm oxygen. After 280 h of exposure one quarter of the outer coating was transformed into a protective alumina layer. Much nickel depletion, due to the evaporation of nickel chlorides, was observed.

Identification of a Caldariomyces fumago mutant secreting an inactive form of chloroperoxidase lacking the heme group and N-glycans.

Abstract: By mutant colony screening of Caldariomyces fumago a mutant was isolated which was slightly greenish on fructose minimal medium and grew slower in comparison to the wild type. The supernatant samples lacked the Soret band typical for the heme group of the CPO and nearly no CPO activity was detected. SDS-PAGE analysis of mutant culture supernatant samples showed production of a 38–40 kDa protein while wild type samples contain the 42 kDa CPO protein. Protein identification using nanoLC-ESI-MS/MS was performed and based on three peptides the protein in the mutant culture was identified as CPO. No differences in the CPO gene sequences of wild type and mutant were found indicating a post-translational defect in protein maturation. Deglycosylation experiments using CPO from wild type and mutant were carried out. After removing N-linked oligosaccharides from wild type CPO a protein band at 38–40 kDa was detected. Our results reveal that the mutant protein lacks the heme group as well as the N-glycans.