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.

On the underlying mechanisms of the low observed nitrate selectivity in photocatalytic NOx abatement and the importance of the oxygen reduction reaction

Abstract: Semiconductor photocatalysis could be an effective means to combat air pollution, especially nitrogen oxides, which can be mineralized to nitrate. However, the reaction typically shows poor selectivity, releasing a number of unwanted and possibly toxic intermediates such as nitrogen dioxide. Up to now, the underlying principles that lead to this poor selectivity were not understood so a knowledge-based catalyst design for more selective materials was impossible. Herein, we present strong evidence for the slow oxygen reduction being one the causes, as the competing back-reduction of nitrate leads to the release of nitrogen dioxide. Consequently, engineering the photocatalyst for a better oxygen reduction efficiency should also increase the nitrate selectivity.

A Novel Type of Environmentally Friendly Slurry Coatings

Abstract: A variety of commercial slurries are available to aluminize the surfaces of nickel-based superalloys; however, they have three main disadvantages. First, the phosphates and chromates or halides used as binders or to activate the diffusion species are environmentally harmful and toxic; second, the slurry coatings can only produce high-aluminum-activity coatings which form precipitate-rich coatings that are detrimental to adherence. Finally, these coatings are limited to the incorporation of aluminum and silicon, whereas the co-deposition of other elements such as chromium or cobalt has not been achieved so far. In this work, the limitations of slurry coatings have been overcome by carefully designing the powder composition and controlling the process to produce co-deposition coatings with chromium, cobalt, or nickel by using nontoxic water-based slurries. This also opens an effective way to control Al activity and to produce low-activity aluminized coatings for the first time when using the slurry technique. These results expand the application range of slurry coatings so they can also be applied under ambient atmosphere, making it possible to fully coat aero engine pieces or large-scale industrial components, providing all properties that are usually only achieved by using more complex and expensive methods such as chemical vapor deposition. Furthermore, these new coatings offer unique advantages that can be very favorable especially as a repairing technique.

Novel Steel Corrosion Protection by Microbial Extracellular Polymeric Substances (EPS) – Biofilm-Induced Corrosion Inhibition

Abstract: Microbially influenced corrosion (MIC) of steel has gained increasing attention in recent years because the damage caused by this process is a significant cost factor for industry. Consequently, inhibition of corrosion and especially the development of corrosion protective films is an important present-day research topic. In this connection, application of microbially produced EPS for mitigating steel corrosion is an innovative idea. However, observations of ”protective” biofilms on metallic surfaces have been previously reported. Their inhibiting effect is generally thought to be caused by oxygen depletion or the formation of passivating layers. In contrast to many conventional corrosion protective methods, EPS or EPS-derived agents would be a cheap and environmentally friendly solution. Extensive research activities are still required, before biofilms or cell-free EPS can be used for corrosion protection on larger scale. In this study, we are developing a novel EPS-based corrosion protection method for unalloyed and corrosion resistant steel in aqueous media, which is based upon the application of microbial metabolic products. EPS of various sulfatereducing bacteria and other microorganisms are investigated for their inhibiting effect. The extent of such inhibition is evaluated in a model test system, in which different steels are subjected to corrosive conditions under sulfate-reducing conditions. To elucidate the protective mechanisms, comparative analyses of the chemical composition of the applied EPS are performed.