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.

Application of the pack cementation process on SiC/SiC ceramic matrix composites

Abstract: The potentials and limitations of a halide-activated pack cementation process on SiC/SiC Ceramic Matrix Composites for the development of bond coats as part of environmental barrier coating (EBCs) systems were investigated. Different pack compositions using chromium, aluminum and alloys of these elements were tested and the kinetics of coating formation were examined in addition to their microstructure. The results and their analogy to diffusion couples were discussed and it was shown that coating elements which form silicides and carbides are promising candidates for coatings deposited on SiC/SiC via pack cementation. Based on such considerations a two-step pack cementation was proposed, which used chromium, one of the suitable elements, in a first step, to finally achieve an alumina-forming coating. The oxidation resistance of the developed coating was tested via thermogravimetric analysis and compared to the uncoated material. The coating protected the fiber-matrix interface of the SiC/SiC Ceramic Matrix Composites from oxidation.

Hybrid joints of die-casted aluminum/magnesium by ultrasound enhanced friction stir welding (USE-FSW)

Abstract: As consistent lightweight construction nowadays becomes more and more important in smart production processes, the demand for joints of dissimilar materials increases steadily due to their variety of advantages in engineering. Friction stir welding (FSW) is an innovative pressure welding technique, which offers the ability to realize such dissimilar joints while achieving high tensile strengths. Furthermore, it has been proved that ultrasound enhanced friction stir welding (USE-FSW) has an additional positive effect on the joint strength of these compounds due to the additional introduction of mechanical energy into the joining zone through influencing the formation of brittle intermetallic phase (IMP) and particle allocation in the weld nugget. In this paper, the influence of power ultrasound introduction via USE-FSW on hybrid joints of industrially die-cast aluminum alloy EN AC-48000 (AlSi12CuNiMg) and magnesium alloy AZ91 (MgAl9Zn1) has been investigated. Besides mechanical testing, light microscopic and scanning electron microscopic investigations (SEM) as well as differential scanning calorimetry have been conducted. Furthermore, corrosion behavior of the base material and X-ray radiographic images of FSW and USE-FSW joints have been examined. Additionally, the influence of different ultrasound powers and changes in the introduction side on the tensile strength and microstructure of the joints has been investigated.

Electrochemical Engineering in Disperse Multiphase Systems

Abstract: Electrochemical multiphase systems of industrial importance may be divided into dispersed three-dimensional electrodes, gas evolving electrodes, conversion of gaseous reactants and electrochemical extraction systems. The engineering fundamentals of all these types developed by several groups during the recent years will be summarized. Additionally new electrochemical techniques for studying non-electrochemical unit operations like absorption and extraction will be introduced.