Behavior of copper‐containing high‐entropy alloys in harsh metal‐dusting environments

Metal dusting is still an unresolved issue at high temperatures. Currently, two material‐related strategies to mitigate metal dusting are described in the literature. On the one hand, highly alloyed materials are used, which contain large amounts of protective oxide‐forming elements, such as Cr, Al, and Si. The second mitigation strategy is based on inhibiting the catalytic effect of Fe, Ni, and Co. These elements all strongly catalyze the formation of solid carbon from the gas phase. Combining the catalytic protection of Cu alloying for metal dusting with protection by a classical alumina/chromia barrier is a native feature that high‐entropy alloys (HEAs) can offer. In this study, the behavior of different equiatomic HEAs with and without Al and/or Cu are studied when exposed at 620°C in a highly aggressive metal‐dusting environment

Corrosion behaviour of FE and NI-based alloys in solar salt and corrosion mitigation strategies via protective coatings

ABSTRACT: This study investigated the corrosion behaviour of commercial and model Fe- and Ni-based alloys in solar salt at 600°C. The thermal decomposition of nitrate salts led to an increasing concentration of oxidizing agents in the salt melt and thus to a higher corrosion rate. For Fe-based alloys, the oxide scales contained a Na- and Fe-rich outer layer, followed by an inner Cr-rich layer and nitridation as well as Cr-depletion was observed at the scale/metal interface. Furthermore, higher extent of chloride impurities in solar salt, led to a significantly higher corrosion rate for ferritic-martensitic alloys. For Ni-based alloys, the formation of a duplex scale consisting of a NiO outer and Ni-Cr spinel layer showed protective character during isothermal exposure; however even for Ni-based alloys, Cr was detected in the salt melt, which showed evidence for its dissolution in the melt as toxic hexavalent Cr. Diffusion aluminide and electroless Ni-P coatings deposited on cost-efficient ferriticmartensitic alloys led to formation of protective oxide scales and hindered the Cr-dissolution into the salt melt.info:eu-repo/semantics/publishedVersio

All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run

We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration < 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal waveform, polarization, direction or occurrence time. All identified events are consistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGO-Virgo search on the data collected between November 2005 and October 2007. The upper limit on the rate of strong gravitational-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per year and Mpc^3 for sample populations of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range 5 10^-22 Hz^-1/2 to 1 10^-20 Hz^-1/2. The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.Comment: 15 pages, 7 figures: data for plots and archived public version at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=70814&version=19, see also the public announcement at http://www.ligo.org/science/Publication-S6BurstAllSky

Behavior of copper‐containing high‐entropy alloys in harsh metal‐dusting environments

Metal dusting is still an unresolved issue at high temperatures. Currently, two material‐related strategies to mitigate metal dusting are described in the literature. On the one hand, highly alloyed materials are used, which contain large amounts of protective oxide‐forming elements, such as Cr, Al, and Si. The second mitigation strategy is based on inhibiting the catalytic effect of Fe, Ni, and Co. These elements all strongly catalyze the formation of solid carbon from the gas phase. Combining the catalytic protection of Cu alloying for metal dusting with protection by a classical alumina/chromia barrier is a native feature that high‐entropy alloys (HEAs) can offer. In this study, the behavior of different equiatomic HEAs with and without Al and/or Cu are studied when exposed at 620°C in a highly aggressive metal‐dusting environment.</p

Cr–Mn-diffusion coatings on VM12: In situ spinel formation with high solar absorptance for concentrated solar plants

Receiver systems in concentrated solar power plants have to withstand harsh desert conditions and high temperatures, while maintaining high efficiencies converting solar radiation to thermal energy within a heat transfer fluid. The need to improve high absorbing receiver coatings with respect to their lifetime is essential to enhance the economic efficiency of such plants. Diffusion coatings based on Cr and Mn are shown to provide intrinsic selfhealing properties forming black Cr–Mn-oxides in situ. Oxidation tests in air are conducted at temperatures between 527 and 710 ◦C up to 100 h. Thereby, solar absorptances up to 93% and optical coatings efficiencies up to 80% are obtained on coated VM12 steel with the best coating performance shown at around 650 ◦C. Thermocyclic oxidation for up to 640 h at a maximum temperature of 650 ◦C proves that there is a slight drop in solar absorptance after around 50 h of exposure, but afterwards it remains stable. Additionally, it is found that coated VM12 performs better in comparison to P91 steel. A mechanism of oxide formation and coating consumption is proposed showing the importance of Mn diffusion on oxide formation. In the beginning of the exposure, Mn2O3 and cubic MnxCr3-xO4 (β-spinel) form, which transform to tetragonal MnxCr3-xO4 (α-spinel) and with continuing exposure also to Cr2O3. For analysis, metallographic investigations are combined with methods such as Ramanspectroscopy, XRD, spectrophotometry, qualitative and quantitative EPMA measurements

A brief history of the TDIF-PXY signalling module: balancing meristem identity and differentiation during vascular development

A significant proportion of terrestrial biomass is constituted of xylem cells that make up woody plant tissue. Xylem is required for water transport, and is present in the vascular tissue with a second conductive tissue, phloem, required primarily for nutrient transport. Both xylem and phloem are derived from cell divisions in vascular meristems known as the cambium and procambium. One major component that influences several aspects of plant vascular development, including cell division in the vascular meristem, vascular organization and differentiation of vascular cell types, is a signalling module characterized by a peptide ligand called TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF) and its cognate receptor, PHLOEM INTERCALATED WITH XYLEM (PXY). In this review, we explore the literature that describes signalling components, phytohormones and transcription factors that interact with these two central factors, to control the varying outputs required in vascular tissues for normal organization and elaboration of plant vascular tissue