The effect of pack-aluminisation on the microstructure of MCrAlY and the performance of thermal barrier coatings

Plasma spraying and pack-aluminising processes were combined and applied to the nickel-base superalloy Mar-M247 to improve its cyclic oxidation resistance. The performance tests of duplex ZrO₂-8 wt.%Y₂O₃/MCrAlY thermal barrier coatings (TBCs) were conducted at 1050 °C, 1075 °C, 1100 °C, 1150 °C and 1200 °C. The results of the experiments in this study showed that TBC specimens with the aluminised MCrAlY bond coat exhibited higher cyclic lives (except for the Ni-22Cr-10Al-1Y bond coat), at all the temperatures tested, than specimens on which the bond coat was not aluminised. The microstructures of the Co-29Cr-6Al-1Y, Co-32Ni-21Cr-8Al-0.5Y and Ni-22Cr-10Al-1Y bond coats with or without aluminising treatment were examined in detail using a scanning electron microscope equipped with an electron probe microanalyzer.     

Energy dissipation via radiative recombination and vibronic relaxation in σ-delocalized silicon backbone network polymers

The nature of ultrafast energy dissipation in poly(n-hexylsilyne), a prototypical σ-delocalized alkysilicon network polymer, is explored. This disordered silicon backbone material exhibits strong near-UV to visible band-edge absorption and a high quantum yield of visible emission. The time evolution of the emission band is studied over four decades of time using time-resolved luminescence as a probe. The data indicate that while there is an ‘intrinsic’ Stokes shift after photoexcitation due to kinetic energy relaxation (<10ps), thermalization within a dense band of vibronic states via intramolecular phonon-assisted hopping on a nanosecond timescale is the dominant mechanism for excited-state decay. The data can be understood in terms of theoretical predictions for energy relaxation in disordered materials.     

Schnelle Lochkorrosion durch ungewöhnliche Anodenstabilisierung in einem Stahl/Wasser-System

Fast pitting corrosion in a steel/water system as a result of unusual stabilization of anodes Corrosion damage as a result of fast pitting was observed in industrial equipment made of unalloyed steel. The rate of formation and the manifestation of the pits are similar to pitting corrosion of stainless steels. Estimation of the kinetics of the localized corrosion in terms of differential aeration cells led to a model which indicates the stabilization of small anodic regions. The stabilization was caused by precipitation of the products of reaction between ferrous ions and polymeric silicate. The high rate of pitting also suggests that the oxygen entering the system during service periods involving the exposure of the system to air has enhanced the corrosion. These ideas could be substantiated by experiments, which also revealed particularly the effect of the concentration of NaCl. Anodic passivation by the addition of Na₂CO₃ or perhaps inhibition may be considered as candidate protective measures.     

Autoklaven-Untersuchungen der Spannungsrißkorrosion von Fe-Cr-Ni-Legierungen in NaCl/Co2/H2S-Medien

Autoclave investigation of stress corrosion cracking behaviour of Fe-Cr-Ni alloys in NaCl/CO₂/H₂S-environment In oil and gas production, the corrosion problems increase as the depth of the reservoirs increases. The oil and gas products contain chloride-rich waters and mixtures of H₂S and CO₂ at high pressures and temperatures. Materials that can be used under these conditions are only high strength high alloy steels and nickel base alloys. These materials must be assessed for corrosion resistance under these conditions. The environment contain chloride ions and hydrogen sulphide, which are known to be critical components for SCC. With the aid of autoclave experiments, the fields of corrosion resistance for the materials no. 1.4462, 1.4563 and 2.4618 were determined as a function of temperature and hydrogen sulphide pressure. The base environment was a 5 Molar sodium chloride solution at 20 bar carbon dioxide. While the corrosion resistance of the duplex steel, material no. 1.4462, decreases markedly as the strength of the material and the hydrogen sulphide pressure increase, the two austenitic materials are completely resistant up to 300 °C and hydrogen sulphide pressure of 15 bar. Only at 300 °C and high partial pressures of hydrogen sulphide the material no. 1.4563 did fail, when stressed to stress levels higher than the YS. The crack path was predominantly transgranular with minute fractions of intergranular cracking. The microstructure appears to have no effect. All results indicate that a mixed mechanism of hydrogen- and chloride induced SCC is operting, while a corrosion enhancement due to interaction of both critical components takes place.     

Alternative fatty food simulants for migration testing of polymeric food contact materials.

The amounts of substances migrating from plastics into foodstuffs with high fat contents are in most cases higher than in foodstuffs with water contents. This increase in migration commonly is due to the higher solubility of the migrating organic compounds in fat compared to water. The increase in migration is not necessarily due to an increase in the substance's diffusion coefficient due to interactions between the fat and the plastic as is often assumed. Ethanol is a good simulant for fatty foods because it has little interaction with many plastics, e.g. polyolefins, migrants are readily soluble in it, and because it is easy to work with analytically. The utilizable limits of ethanol and ethanol/water mixtures as food simulants are developed from the physical background of diffusion. The use of ethanol and ethanol/water mixtures is supported by published experimental migration results.     

Connections to cerebellar cortex (Larsell's HVI) in the rabbit: A WGA-HRP study with implications for classical eyeblink conditioning.

Conditioned eyeblink responses are presumably learned in the cerebellum and relayed to motoneurons by way of the red nucleus. Projections from the red nucleus to cerebellar cortex (Larsell's lobule HVI) could be important for shaping temporally adaptive features of the conditioned response. Rabbits that had pipettes containing wheat germ agglutinated horseradish peroxidase (WGA-HRP) implanted unilaterally into HVI showed retrograde labeling of neurons within subregions of the contralateral red nucleus implicated in eyeblink conditioning by lesioning and recording studies. Retrogradely labeled neurons were also observed in the pontine nuclei, inferior olive, and spinal trigeminal nucleus pars oralis. Projections to HVI provide a possible neural substrate for implementing time-derivative computational models of learning in the cerebellum. Time-derivative models are capable of describing the timing and topography of conditioned responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial eigenvalue decomposition of large images using spatialtemporal adaptive method

Finding eigenvectors of a sequence of real images has usually been considered to require too much computation to be practical. Our spatial temporal adaptive (STA) method reduces the computational complexity of the approximate partial eigenvalue decomposition based on image encoding. Spatial temporal encoding is used to reduce storage and computation, and then, singular value decomposition (SVD) is applied. After the adaptive discrete cosine transform (DCT) encoding, blocks that are similar in consecutive images are consolidated. The computational economy of our method was verified by tests on different large sets of images. The results show that this method is 6 to 10 times faster than the traditional SVD method for several kinds of real images. The economy of this algorithm increases with increasing correlation within the image and with increasing correlation between consecutive images within a set. This algorithm is useful for pattern recognition using eigenvectors, which is a research field that has been active recently.     

Lipasekatalysierte Triglyceridumesterung in einem lösungsmittelfreien Prozeß I: Analytik und Umesterungskinetik

Lipase-Catalyzed Interesterification of Triglycerides in a Solvent-Free Process I: Analytics and Kinetics of the Interesterification The interesterification of lipids catalyzed by immobilized lipases is an interesting substitute to the chemical interesterification. Studies using an industrial manufactured biocatalyst in a solvent-free process were performed. The kinetics of the interesterification were examined as a function of temperature and water content of the reaction system. The reaction rate of the interesterification can be described with reversible first order reaction kinetics. A part of the triglycerides of the substrate is hydrolyzed by a lipasecatalyzed lipolysis. Hydrolysis products are 1,2(2,3) and 1,3-diglycerides. This shows that an unspecific interesterification is catalyzed if the residence time is extended.