The roles of Eu during the growth of eutectic Si in Al-Si alloys

Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si

Geological Specimens Database Project

This project tasked us with creating a high-usability web application for the Valparaiso University Department of Geology and its geological specimens collection. The application is made using HTML/CSS, PHP, and SQL to hold and show mineral specimen data collected by the professors within the Geology Department. The purpose of this application is to allow students and professors to easily store and access data on the rocks and minerals that they collect. The students can input a unique code or keyword into a search bar within the application, or scan a unique QR code to search specimens of minerals within the collection. Once queried, the application displays the mineral\u27s name, date of collection, who it was collected by, the region the mineral was found, a description of the mineral, as well as photos of the specimen

Aluminum depletion induced by complex co-segregation of carbon and boron in a {\Sigma} 5 [3 1 0] bcc-iron grain boundary

The local variation of grain boundary atomic structure and chemistry caused by segregation of impurities influences the macroscopic properties of poylcrystalline materials. Here, the effect of co-segregation of carbon and boron on the depletion of aluminum at a $\Sigma 5\,(3\,1\,0\,) [0\,0\,1]$ tilt grain boundary in a $\alpha-$Fe-$4~at.~\%$Al bicrystal was studied by combining atomic resolution scanning transmission electron microscopy, atom probe tomography and density functional theory calculations. The atomic grain boundary structural units mostly resemble kite-type motifs and the structure appears disrupted by atomic scale defects. Atom probe tomography reveals that carbon and boron impurities are co-segregating to the grain boundary reaching levels of >1.5 at.\%, whereas aluminum is locally depleted by approx. 2~at.\%. First-principles calculations indicate that carbon and boron exhibit the strongest segregation tendency and their repulsive interaction with aluminum promotes its depletion from the grain boundary. It is also predicted that substitutional segregation of boron atoms may contribute to local distortions of the kite-type structural units. These results suggest that the co-segregation and interaction of interstitial impurities with substitutional solutes strongly influences grain boundary composition and with this the properties of the interface.Comment: 26 pages, 10 Figures, 1 Tabl

Interstitial segregation has the potential to mitigate liquid metal embrittlement in iron

The embrittlement of metallic alloys by liquid metals leads to catastrophic material failure and severely impacts their structural integrity. The weakening of grain boundaries by the ingress of liquid metal and preceding segregation in the solid are thought to promote early fracture. However, the potential of balancing between the segregation of cohesion-enhancing interstitial solutes and embrittling elements inducing grain boundary decohesion is not understood. Here, we unveil the mechanisms of how boron segregation mitigates the detrimental effects of the prime embrittler, zinc, in a $\Sigma 5\,[0\,0\,1]$ tilt grain boundary in $\alpha-$Fe ($4~at.\%$ Al). Zinc forms nanoscale segregation patterns inducing structurally and compositionally complex grain boundary states. Ab-initio simulations reveal that boron hinders zinc segregation and compensates for the zinc induced loss in grain boundary cohesion. Our work sheds new light on how interstitial solutes intimately modify grain boundaries, thereby opening pathways to use them as dopants for preventing disastrous material failure.Comment: 29 pages, 6 figures in the main text and 10 figures in the supplementar

F-SAR Airborne Measurement Campaign in Iceland for VERITAS

Non-vegetated volcanic surfaces are rare on Earth, but are important test beds for preparing an interplanetary mission to Venus, Earth's neighbour, which has a very similar structure and volcanic activity. Both NASA and ESA are planning new SAR missions to Venus in the early 2030s. In August 2023, the German Aerospace Center and the Jet Propulsion Laboratory conducted a joint measurement campaign in Iceland in preparation for the VERITAS (Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy) mission to Venus. While the VERITAS ground team collected ground truth at test sites near the volcano Askja in central Iceland and on the Reykjanes peninsula, the F-SAR sensor on board a DLR research aircraft acquired multi-frequency radar data in seven measurement flights between 31 July and 9 August. Initial processing of some of the data was carried out immediately after the flights to ensure data quality and to satisfy curiosity. The data is currently being fully processed at DLR in Germany and will then be made available for scientific analysis by the VERITAS partners

VARCITIES pilot characterisation : research findings of the environmental conditions and health-related risks in Gzira

Gżira is a small, highly densely populated town in the Maltese Islands measuring just 0.6 km2 in surface area, that is facing many ecological and environmental challenges. The Horizon 2020 project, VARCITIES, aims to co-create visionary solutions (VS) with the Gżira community and various stakeholders to address these problems. A characterisation study was carried out as the first step in the processes needed to develop these solutions. This report shows data gathered by the Research Innovation Unit of the Gżira Local Council and University of Malta, with VSs being suggested involving microgreening and citizen engagement activities to address the lack of green public spaces and health related risks currently perceptible in its geographical location, climate, and infrastructure. Following a series of ethnographic field observations, air quality measurements, academic research and consultations with expert stakeholders three visionary solutions were carefully co-created in order to devise the main Nature-based Solutions (NBS) to be implemented in the pilot city. This article discusses the present situation in Gżira and identifies the challenges of the context, and describes the ways in which VARCITIES attempts to address such problems and how NBS can be of benefit to the Gżira locality and users of space. The main challenges identified about the pilot sites are linked to deprivation of green infrastructure, high levels of air and noise pollution, the Urban Heat Island effect and improper disposal of waste. Visionary Solutions were proposed for these challenges in the form of infrastructural implementation and sociocultural events. These include; the micro-greening of a bus stop area and pop-up activities in Rue d’Argens, a citizen science activity involving residents in conducting air pollution measurements to increase awareness and a green outdoor learning space at St. Clare Gżira Primary School.peer-reviewe

Smart On-board Processing for Next Generation SAR Payloads

Smart on-board processing for Earth observation systems (SOPHOS) is a 3-year Horizon Europe project. SOPHOS will design and implement enabling technology for high-end data products produced on board spacecraft via the implementation of more power efficient high-performance space processing chains for various Low-Earth Orbit (LEO) missions, with a focus on Synthetic Aperture Radar (SAR), which is one of the most data intensive space applications currently used. This paper describes the adopted technology and the selected SAR use cases

First Interferometric Trials with the Airborne Digital-Beamforming DBFSAR System

The Microwaves and Radar Institute of the German Aerospace Center (DLR) is known for its consistent work on the field of airborne Synthetic Aperture Radar and its application. Currently, the Institute is developing a new advanced airborne SAR system, the DBFSAR, which is planned to supplement its operational F-SAR system in near future. The development of DBFSAR was triggered by the various evolving digital beamforming (DBF) techniques for future space-borne SAR systems and the need for an airborne experimental platform for preparation of such missions. Additionally, there is a demand for very high resolution SAR imagery, which cannot anymore be fully satisfied with the existing F-SAR system. This paper should give an overview over the current status and performance of the DBFSAR system, including interferometirc results from test flights performed in spring 2017