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.

Expanding the Scope of Laccase‐Mediator Systems

Abstract: The laccase-mediator system (LMS) for the regeneration of oxidised nicotinamide co-factors was revisited to broaden the mediator scope. Among the 18 mediators screened, acetosyringone, syringaldehyde and caffeic acid excelled with respect to activity and stability under process conditions. The LMS based on the laccase from Myceliophthora thermophila and acetosyringone was further investigated and applied to promote the nicotinamide adenine dinucleotide (NAD+)-dependent oxidation of glucose as well as the oxidative lactonisation of 1,4-butanediol to the corresponding γ-butyrolactone.

The scaling of iron in oxygen and sulfur-containing gases

Abstract: The following possible conditions for the simultaneous formation of oxide and sulfide on iron in oxygen and sulfur-containing gases are considered: (7) simultaneous thermodynamic stability of oxide and sulfide; (2) temporal changes in gas composition; (3) intermediary cracking of the oxide film; (4) solubility and diffusion of sulfur in the oxide (lattice diffusion); (5) kinetic conditions for simultaneous oxide and sulfide formation at the scale-gas interface.

The cyclic-oxidation behavior of several nickel-base single-crystal superalloys without and with coatings

Abstract: Several commerical single-crystal superalloys (CMSX-2, CMSX-3, CMSX-4, CMSX-6, SRR 99) and some laboratory versions of one of them (CMSX-4) with various Y additions were investigated concerning their cyclic-oxidation resistance in air at 1000 and 1150°C. The investigations also included two materials (CMSX-6, SRR 99) with an RT-22 coating. Weight changes and acoustic emission were recorded up to 1000 cycles and scales, coatings, and substrates were characterized by metallography, SEM, and microprobe in postexperimental investigations. The best cyclic-oxidation behavior and excellent resistance to spalling even at 1150°C were shown by a laboratory version of CMSX-4 containing between 10 and 60 ppm Y. While at 1000°C interdiffusion can be taken as tolerable for the coated alloys, there is rapid degradation of the coating by interdiffusion at 1150°C.

Cyclic-oxidation behavior of TiAl and of TiAl alloys

Abstract: The cyclic-oxidation behavior of (in w/o) Ti-36Al, Ti-35Al-0.1C, Ti-35Al-1.4V-0.1C and Ti-35Al-5Nb-0.1C was studied between 800 and 1000° C in air. A few experiments were also performed in oxygen. Scale spallation after oxidation in air occurs during cooling on TiAl, TiAl-C, and TiAl-V at or close to the metal/scale interface when a critical scale thickness has been achieved. This process repeats and can lead to a stratified scale. These three materials form scales composed of an inward-growing fine-grain mixture of TiO2-Al2O3 and an outward-growing coarse-grain TiO2 layer or TiO2+Al2O3 mixture. The TiAl-Nb alloy had a significantly different behavior. The scale on this material grew very slowly because a protective Al2O3 layer formed at the metal/scale interface. This behavior resulted in much better resistance to spallation because the critical scale thickness was reached only after a much longer time, and is different from the behavior of the other three alloys. Oxidation in air leads to slight nitridation of the subsurface zone beneath the scale. In comparison to oxidation in air, oxidation in oxygen improves the cyclicoxidation behavior. Whereas the scale formed in air was uniformly thick over the entire surface, the scale grown in oxygen varied locally in structure and thickness. A large fraction of the surface was covered with a thin Al2O3 layer, while the remaining part formed a two-layer scale similar to that formed in air. The results are discussed briefly in the light of a recently published model for scale spallation under compressive stress, however, quantitative estimations are not possible due to a lack of relevant data.