Plasmachemisches Ätzen und Beschichten bei Atmosphärendruck

Atmospheric pressure plasma‐chemical etching and deposition. Application in crystalline silicon photovoltaics. For industrial processing of wafer based crystalline silicon solar cells a variety of different technologies are applied. The combination of these requires a complex wafer handling; increasing not only investment costs, but also the risk of wafer breakage. Application of plasma technologies offers the possibility to manufacture crystalline silicon solar cells without any wet chemical or vacuum processes. At Fraunhofer IWS all etching steps necessary for the production of solar cells and the deposition of silicon nitride as passivation and anti‐reflection coating were demonstrated successfully using atmospheric pressure plasma technologies.     

The fabrication of nanoporous Pt-based multimetallic alloy nanowires and their improved electrochemical durability

A general approach for the fabrication of nanoporous Pt-based multimetallic alloy nanowires is reported, which involves electrodeposition of corresponding precursor alloys into porous anodic alumina templates, followed by a mild dealloying process. Nanoporous ternary PtCoNi and PtCoAu as well as quaternary PtRuCoNi nanowires were successfully fabricated, and their microstructure and composition were examined by transmission electron microscopy. Electrochemical tests showed that these porous nanowires exhibit higher electrochemically active surface area and much improved durability compared to commercially available Pt black, and may find potential applications in electrocatalysis and electrochemical sensing.     

An Alternative Route Towards Metal–Polymer Hybrid Materials Prepared by Vapor‐Phase Processing

Transition metals incorporated into polymers lead to unusual or improved physical properties that significantly differ from those of purely organic polymers. A simple and practicable incorporation of diverse transition metals into any available polymer would make an important contribution to overcome some of the synthetic difficulties of metal‐polymer hybrid materials. Here, it is demonstrated that atomic layer deposition (ALD) can be a promising means to resolve some of those difficulties. It is found that even polytetrafluoroethylene (PTFE) with its great physical and chemical stability can be easily transformed into a transition metal–PTFE hybrid material simply by applying a metal‐oxide ALD process to PTFE. Upon metal incorporation into the PTFE, the molecular structure as well as mechanical properties (tensile behavior) of PTFE were observed to significantly change. For a better understanding of the changes to the material, experimental investigations using Raman spectroscopy, attenuated‐total‐reflection Fourier‐transform infrared spectroscopy, wide‐angle X‐ray diffraction, and energy‐dispersive X‐ray analysis were performed. In addition, with density functional theory calculations, potential bonding states of the incorporated metal into PTFE were modeled and predicted. The ALD‐based vapor‐phase approach for metal incorporation into a polymer could bring about rapid progress in the research area of metal–polymer hybrid materials.     

Reaction calorimetric investigation of the ring-opening polymerization of ε-caprolactone

The ring-opening polymerization of ε-caprolactone was investigated by means of the Mettler RC1 reaction calorimeter. In the range of small and medium monomer conversions this method can successfully be used for the determination of the course of the bulk polymerizations. The experimental results obtained by calorimetric and gravimetric method, respectively, are compared and the course of the polymerization is discussed in dependence on the reaction parameters (initiator, temperature).     

Different signals control the activation of glycolysis in the yeast Saccharomyces cerevisiae

The glycolytic pathway in Saccharomyces cerevisiae is activated by fermentable sugars at several steps. Mutants with deletions of genes coding for enzymes of the upper part of glycolysis were used to characterize the triggering mechanisms. Synthesis of fructose-2,6-bisphophate is catalysed by two 6-phosphofructo-2-kinase isoenzymes, one of which is activated by fermentable sugars while synthesis of the second enzyme is induced (Kretschmer and Fraenkel, 1991). Increase in the level of fructose-2, 6-bisphosphate is demonstrated to depend on an internal metabolite upstream of the phosphoglucose isomerase reaction. The signalling process correlates with distinct temporal changes in the concentration of glucose-6-phosphate but not with its absolute level, indicating an adaptational mechanism. It is independent of the uptake and phosphorylation systems used by different sugars. Interestingly, this increase, although delayed, could also be observed in strains lacking the rapid cAMP increase after sugar addition which is thought to be responsible for the activating process. Synthesis of glucose-6-P and fructose-6-P is needed for the complete induction of pyruvate kinase and inactivation of fructose-1,6-bisphosphatase. On the other hand, induction of pyruvate decarboxylase depends mainly on a signal in the lower part of glycolysis.     

Microprocesses of metal dusting on nickel and Ni-base alloys

Microstructural and microchemical investigations were carried out on nickel and Inconel 600 after exposure to strongly carburizing atmospheres at temperatures of about 600 to 650°C to study their metal dusting behaviour. Contrary to iron and low-alloy steels, where metal dusting proceeds via the formation and disintegration of a metastable carbide M₃C, both nickel and Inconel 600 directly disintegrate. Inside the metal this disintegration proceeds by formation of thin graphite filaments of nearly 10 nm in diameter, the atomic basal planes of which are oriented perpendicular to the surface thus effecting a high reactivity at the growth front. Subsequently, fine particles or larger parts of the metal surface layer are released, which are buried in the deposited graphite layer on the surface. In case of Inconel 600, containing Cr with mass contents of about 15%, the disintegration can be delayed by the formation of a chromium oxide layer, but no safe protection against metal dusting is obtained.     

Zur natrium- und kaliumbestimmung mit ionensensitiven elektroden

Zusammenfassung Obwohl sie zu den häufigsten Elementen gehören, zählen die Bestimmungen des Natriums und Kaliums in der Lebensmittelchemie zu den Ausnahmen. Da zwischen der Kochsalzaufnahme und dem Bluthochdruck ein Zusammenhang zu bestehen scheint, nimmt das Interesse an der tatsächlichen Kochsalzaufnahme ständig zu.Vorgestellt wird die Natrium- und Kaliumbestimmung mit Hilfe von ionensensitiven Elektroden, die Vorteile gegenüber der AAS aufweisen. Hierbei ist besonders die minimale Probenvorbereitung zu nennen. Die Methode ist nicht auf Getreideprodukte oder Backwaren beschränkt, sondern läßt sich nach Änderung der Vorbereitung auf praktisch alle Lebensmittel anwenden. Die Richtigkeit und Genauigkeit der Bestimmung konnte durch Vergleiche und Zusatzversuche bestätigt werden.

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Determination of sodium and potassium by ion-sensitive electrodes

Summary Although sodium and potassium belong to the most common elements, their determination in foods is rarely carried out. Because there seems to be a relationship between the consumption of sodium chloride and hypertension there is a growing interest in the actual intake of sodium chloride.Ion-sensitive electrodes are utilized for the determination of sodium and potassium with obvious advantages over the AAS, particularly by requiring a minimum of sample preparation. The method is applicable for practically all types of foods. Recovery rates were 96–102% and the reliability was verified by comparison with other methodology.

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Nr. 5011 der Veröffentlichungen der Bundesforschungsanstalt für Getreide- und Kartoffelverarbeitung, Detmold