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Stress- and Time-dependent Variations of Elastic Properties for Integrity Assessment in a Reinforced Concrete Test Bridge
No full textIn lab experiments, it has been observed that the stress–and time-dependent elastic properties of a complex material at a structural scale perform accordingly to its composition at a microstructural level. We seek complementary practices to the current wavefield-based non-destructive testing techniques to assess not only the integrity level of civil structures but also the microstructural elements that contribute to it. In this paper, we study the systematic evolution of elastic properties of concrete as an alternative to investigate the density of micro imperfections in an outdoor-conditioned concrete structure. We estimate 5-second relative velocity changes in four locations on a Test bridge subjected to the action of vertical impulsive sources, at different prestressing levels (dynamic effects at different static conditions). We describe the structure’s stress- and time-dependent elastic response by means of acoustoelastic effect and Slow-dynamic processes, respectively. We also estimate the conventional ultrasound pulse velocity and perform a cooperative integrity analysis of the structure using the three elastic phenomena. Our findings reveal: 1) The presence of soft microstructures and their orientation’s influence on the acoustoelastic effect and Slow-dynamics in field-conditioned concrete structures. 2) The relation of low ultrasound pulse velocities with high acoustoelastic effect and high magnitudes and variability of Slow-dynamics. 3) Different elastic behaviours on the north and south spans of the bridge, suggesting different heterogeneity levels on the analysed locations of the concrete beam
Fibre-optic thermometry to support the clean energy transition
No full textThe measurement and control of temperature plays a key role in achieving the European Green Deal targets for a low carbon energy system. Fibre-optic thermometry is an emerging technology that can improve temperature measurement in extreme environments for energy providers and industry due to its distributed sensing and immunity to electromagnetic fields. Various applications for optimisation and monitoring in the energy sector are described, covering the whole range from energy generation to transmission and consumption. However, fibre-optic thermometers have cross sensitivities to other quantities (e.g., strain and humidity) and ageing effects that need to be investigated, quantified and minimised to obtain traceable and reliable measurements. This is particularly important so that applications in critical infrastructure can benefit from future measurements that are not possible with conventional sensors. The European INFOTherm project aims to overcome the limitations that currently prevent the widespread use of fibre-optic thermometry by creating a dedicated European metrology infrastructure for research, development and calibration. First results on measurement uncertainty, improvement of measurement techniques and practical field tests are presented
Transport gefährlicher Güter - Bereitstellung reaktiver Stoffe für Prozesse
No full textBei dem Transport gefährlicher Güter handelt es sich um Transporte auf dem Land, also der Straße, der Schiene, auf den Binnenwasserstraßen sowie auf der See und in der Luft. Die gefährlichen Güter sind in aller Regel Stoffe, deren herausragende Eigenschaft die Reaktivität ist. „Reaktivität, auch Reaktionsfreudigkeit oder Triebkraft der Stoffe, ist eine Kern-Eigenschaft der chemischen Stoffe, also auch der einzelnen Elemente und Verbindungen, und bezeichnet damit die Fähigkeit der Stoffe, in Wechselwirkung mit anderen Stoffen zu treten, spontan und unter Freisetzung von Energie chemische Reaktionen auszulösen und im Ergebnis neue chemische Stoffe zu bilden. Diese Triebkraft resultiert aus dem Bestreben der Stoffe, möglichst abgeschlossene und damit energetisch günstigere Elektronenhüllen zu schaffen und damit zu erhalten. Im Verlauf der chemischen Reaktion kommt es daher zwischen den Partnermolekülen zum Austausch, d. h. zur Aufnahme und Abgabe von Elektronen und damit zugleich zur gemeinsamen Nutzung der abgeschlossenen Elektronenhülle und zu einem stabilen energetischen Zustand.
Reaktive Stoffe haben meist sog. funktionelle Gruppen, also Doppel- oder Dreifachbindungen, oder sie enthalten Chlor-, Sauerstoff- oder Stickstoffatome.
Wie es die Begriffe Reaktionsfreudigkeit oder Bildungstrieb andeuten, steckt eine Kraft in den chemischen Stoffen, die sie antreibt, sodass die Reaktionen oft sehr lebhaft bis stürmisch und unter Freisetzung von Wärme verlaufen (exotherme Reaktionen). Verlaufen die Reaktionen sogar explosionsartig, dann kommt es nicht zur Bindung, sondern dann gehen die Moleküle im wahrsten Sinne des Wortes in die Brüche.
Friedrich der Große schrieb dazu 1777 an Voltaire: ‚... Was soll ich zu den Chemikern sagen, die, anstatt Gold zu machen, es bei ihren Experimenten in Rauch aufgehen lassen?’ (Voltaire, Friedrich II, Briefwechsel).“
Soweit ein Zitat aus einem Brief von Frau Prof. Dr. Ursula Stephan, Halle, 2024.
Im Prinzip werden diese reaktiven Stoffe (gefährliche Güter) entweder zum Lager, zum Handel und somit zum Verbraucher oder zu Prozessanlagen transportiert, in denen sie den wesentlichen Bestandteil der stofflichen Seite in den Reaktoren darstellen. In den unterschiedlichsten Prozessen in der Wirtschaft ist diese Reaktivität der eingesetzten Stoffe unverzichtbare Voraussetzung für erfolgreiche Prozessdurchführungen.
Die Vorlesungen der Autoren dieses Buches über den Transport gefährlicher Güter sind seit 2006 an der Hochschule für Wirtschaft und Recht Berlin (HWR), der Hoch-schule Furtwangen (HFU) und der Berliner Hochschule für Technik (BHT, ehemals Beuth Hochschule für Technik) angeboten worden. Die Industrie-und Handelskammern in Berlin und Reutlingen hatten jeweils die Vorlesungen an der HFU und der HWR zeitweise als Ausbildungsstoff und die Vortragenden als Dozenten gleichwertig für die Vorbereitung zur Prüfung für den Gefahrgutbeauftragten für die Straße nach der Gefahrgutbeauftragtenverordnung (GbV) anerkannt. Die Studierenden konnten sich nach absolvierter Vorlesung direkt bei der IHK zur Prüfung anmelden, ohne einen weiteren Kurs bei einem von der IHK anerkannten Schulungsveranstalter zu absolvieren.
Mit diesem Buch soll das komplexe und umfangreiche System zur Beförderung gefährlicher Güter für den Leser aufgeschlossen werden, was auch die Managementebene einschließt.
Die Regulierung bestimmter Vorgänge findet nach Austausch vieler Ideen im inter-nationalen Raum statt und wirkt dann auch in den unmittelbaren Bereich der Firmen, einschließlich der kleinen und mittleren Unternehmen (KMU), zurück. Das Thema muss verstanden werden, und zwar in der Sache und im Prozess des Werdegangs. Hierzu finden sich hilfreiche Texte, die für das Management für zukünftiges Vorgehen wertvoll sein können.
Auch, wenn sich das Buch grundsätzlich auf die Beförderung gefährlicher Güter auf der Straße bezieht, können die meisten Angaben auch auf die Vorschriften für die anderen Verkehrsträger (Schiene, Binnenschifffahrt, Seeschifffahrt und den zivilen Luftverkehr) angewandt werden. Auch wird an dieser Stelle deutlich darauf hingewiesen, dass das Buch keinen Anspruch auf vollständige Abbildung der Gefahrgutvorschriften, insbesondere des ADR, erhebt. Vielmehr wird auf die wichtigsten Aspekte hingewiesen, die aus Sicht der Autoren für das Verstehen und den Umgang mit den Vorschriften essenziell sind
In situ structural evolution and activity descriptor of atomically dispersed catalysts during nitrate electroreduction
No full textSingle‐Atom Catalysts (SAC) have emerged as a promising class of materials for various catalytic applications, including the electrochemical nitrate reduction reaction (eNO3RR) and consequently ammonia production. While the efficiency and selectivity of these materials have been extensively highlighted for the eNO3RR, the in situ evolution to their structure and composition during electrocatalysis is largely unexplored and lacks catalyst design principles. To solve this, we investigated a series of high utilization metal‐nitrogen‐carbon (MNC) SACs (M = Cr, Fe, Co, Ni, and Cu) for eNO3RR. Except for CuNC, which selectively produced nitrite, all catalysts exhibited Faradaic efficiencies (FE) for ammonia exceeding 50%. NiNC demonstrated the highest performance (FE of 78.0 ± 2.9% at −0.4 V versus reversible hydrogen electrode (RHE) at pH 13 and maximum ammonia production rate of 615.7 ± 176.5 µmol·h−1·, corresponding to an energy efficiency of 15.1 ± 1.4% at −0.6 VRHE), followed by CoNC. In situ Synchrotron X‐ray fluorescence (SXRF) mapping at various cathodic potentials (from open circuit potential to 0.0 VRHE and then −0.6 VRHE at 100 mV steps) revealed significant mobility of Ni within the carbon matrix, leading to the formation of metallic clusters from 0.0 VRHE. Similar in situ metal clustering is observed for CoNC. Structure‐activity plots are generated from both MNC literature and results obtained here, finding a clear trend between OH binding energy and turnover frequency, with the high activity of NiNC and CoNC in this work explained by their stronger OH binding in the metallic structure compared to their SAC coordination. This work therefore, reveals the structure‐activity‐stability of MNCs for eNO3RR and provides a simple descriptor for identifying highly active eNO3RR catalysts and their in situ structural evolution
Early Response Prediction for H2 Sensors
No full textGreen hydrogen (H2) is essential for the global transition to clean energy; it will significantly reduce emissions from heavy industry and the long-distance transport system. H2 can be used as fuel in fuel cells, storing surplus renewable energy, and as a feedstock in industrial processes. However, H2 faces significant safety challenges during storage and transportation. Accidents due to H2 leakage and explosions raise serious concerns due to its high flammability, rapid diffusion in air, and extremely low ignition energy. To mitigate risks associated with H2 leakages, reliable and automated H2 safety systems are essential for emergency repairs or shutdown. An early response from H2 sensors is crucial for early warning in accidents. The earlier response time of H2 sensors is often constrained by their sensor principle, which is heavily influenced by the sensor material’s properties. This study explores methods for earlier sensor response through predictive algorithms. Specifically, we investigate transient response predictions using a First-Order (FO) model and propose improvements through the First-Order with early response and the First-Order with adapted early response model. Both models can predict the stable value of the H2 sensor response from a small time window, which is 70.89% and 83.72% earlier, respectively, than the time required for the sensor hardware to reach it physically. The model’s performance is evaluated by calculating the fitting error with a 2 % threshold. Our current research lays the groundwork for future advancements in real-time sensor response predictions for hydrogen leakage
Graeber Lab for Energy Research at Tag der Chemie in Adlershof
No full textHighlighting recent progress in the Graeber Lab for Energy Research in the areas of alkali-metal tensiometry, alkali-metal anodes in contact with solid electrolytes, sulfur cathodes and solid electrolyte synthesis
NASICON Electrolytes for Room-Temperature Sodium-Sulfur Batteries with NaK Alloy Negative Electrode Interface
No full textThe aim of the research is to develop a novel NASICON (NA Super Ionic CONductor) electrolyte for room-temperature (RT) sodium-sulfur (Na-S) cells employing a liquid sodium-potassium (NaK) alloy at the negative-electrode interface. The NaK alloy can improve the interfacial contact between the sodium-metal electrode and the solid electrolyte. The synthesized NASICON material must be stable with the alkali-metal alloy and provide good electrochemical performance at RT
Algae-dominated metaproteomes uncover cellular adaptations to life on the Greenland Ice Sheet
No full textEukaryotic algae-dominated microbiomes thrive on the Greenland Ice Sheet (GrIS) in harsh environmental conditions, including low temperatures, high light, and low nutrient availability. Chlorophyte algae bloom on snow, while streptophyte algae dominate bare ice surfaces. Empirical data about the cellular mechanisms responsible for their survival in these extreme conditions are scarce. This knowledge gap was addressed by quantifying proteins for both algal taxa from samples on the southern margin of the GrIS. We show that the streptophyte glacier ice algae have a relative enrichment in proteins involved in environmental signaling and nutrient transport, indicative of cellular readiness to dynamically respond to extreme GriS environmental cues, linked, for example, to photoprotection and the rapid update of scarce nutrients. In contrast, the chlorophyte snow algae have a high abundance of proteins linked to lipid and nitrogen metabolisms, providing evidence for the biological processes sustaining the cellular carbon and nitrogen stores necessary for survival in an oligotrophic environment. We also identify proteins in both taxa linked to the synthesis and breakdown of key cellular pigments. Our study gives novel insights into the cellular biology of these algae and their adaptation to extreme environments
Unveiling Aging Mechanisms of Electrolytes in Commercial End-of-Life Lithium-Ion Batteries
No full textIn this study, 77 end-of-life (EOL) commercial lithium-ion batteries (LIBs) of different formats were systematically analyzed to investigate electrolyte degradation mechanisms and the influence of pristine electrolyte composition on aging. Comprehensive chemical characterization employed targeted and non-targeted mass spectrometry (MS), combining liquid and gas chromatography (LC-MS/MS, GC-MS) with high-resolution MS (HRMS). This approach identified confirmed pristine components and complex degradation products. Commercial rechargeable pouch and cylindrical cells often deviated from conventional research model systems, using mixed lithium salt anions, ionic liquids (ILs), and high concentrations of triflates, triflimides, and bis(fluorosulfonyl)imide (FSI), functioning as solvents, salts, or additives. Specific IL degradation products and previously unreported pathways were proposed. A novel series of oligomerization products from propylene carbonate (PC) was also identified. In contrast, non-rechargeable coin cells showed prevalent use of per- and polyfluoroalkyl substances (PFAS) in their original electrolytes. Distinct PFAS degradation mechanisms were proposed for the first time. The absence of carbonate oligomers and lithium salt-derived products in coin cells, alongside standard carbonates, suggests lithium counterion coordination critically influences Lewis acid-catalyzed degradation. These findings provide new insight into real-world LIB aging, highlighting differences between commercial devices and model systems