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.

Investigations on the influence of internal nitridation on creep crack growth in alloy 800 H

Abstract: For two batches of Alloy 800 H with Al contents of 0.02 and 0.34 pct, creep crack growth was investigated at 1000 °C in air and in an Ar-5 pct H2 atmosphere. TheK concept, the net-section stress concept, and theC* concept of creep fracture mechanics were applied when plotting the experimental results. TheC* concept proved to give the best correlation between load parameter and crack growth rate. A good agreement was observed between the experimental results and the model calculations for crack extension by constrained diffusive cavity growth. Strong internal nitridation, which occurred in the air tests and which had been shown to increase the creep strength in creep rupture tests, did not show any significant influence on the creep crack growth rate in comparison with tests in an Ar-5 pct H2 atmosphere, in which no internal nitridation was observed. Also, the differences in the Al contents of the two batches did not play a role. This behavior is explained by the fact that neither the nitride particles nor the particle matrix interface is a particularly weak site in the material. It also becomes obvious that theC* concept can be rather insensitive to precipitation strengthening effects, if these only affect the parameterB in Norton's creep law.

Identification of the spinel (Cr, Al)3S4 in the internal sulfidation zone of Al-diffusion coatings

Abstract: The thiospinel (Cr, Al)3S4 has been identified in the internal sulfidation zone of Al-diffusion coatings by electron diffraction in a transmission electron microscope. The Al/Cr ratio of this phase can vary over a rather broad range, obviously dependent on the Al/Cr ratio in the surrounding metallic matrix. The spinel can dissolve significant amounts of Ni and Mo, some Co but only traces of Ti. Increasing Al-content extents its stability to higher temperatures.

Refined Model for the Optimal Metal Content in Semiconductor Photocatalysts

Abstract: Doping with metal ions is a simple and convenient method of improving the photocatalytic activity of semiconducting materials. As revealed previously (Bloh et al. J. Phys. Chem. C 2012, 116, 25558−25562), the optimal doping ratio is strongly dependent on the particle size and can be predicted with an empirical function. This work expands on that model, providing a more accurate physical explanation of the observed behavior. The new model is based on the theory that only the fraction of dopants that is situated on the particle surface has a beneficial effect. Analysis of almost 200 data points from the literature revealed that the optimal doping ratio corresponds well to an equivalent of 3.54 surface dopant atoms per particle, apparently independent of other parameters such as material or dopant. With this knowledge, the optimal doping ratio for a given catalyst can be predicted with good precision. The findings also suggest that doping and grafting essentially cause the same effect, the latter while avoid...