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Paper des Monats
- ja (93)
Isotope analysis plays a critical role in various disciplines, including environmental science, archaeology, and forensic investigations. Traditional methods such as mass spectrometry provide precise isotopic data but often require complex, costly setups and extensive sample preparation. As an alternative, optical spectrometry has emerged as a versatile and less invasive technique. This presentation explores the advancements and applications of optical spectrometry methods in isotope analysis, emphasizing their benefits and challenges.
Lithium (Li), Boron (B), Nitrogen (N), Magnesium (Mg), and Calcium (Ca) are pivotal elements across various spheres such as the hydrosphere, biosphere, and lithosphere, significantly impacting (bio-) geochemical and physiological processes. These elements exhibit stable isotopes with substantial roles in geological, environmental, and biological studies. The traditional method for measuring isotope amount ratios has been through mass spectrometry, which, despite its accuracy, comes with high operational costs, the need for skilled operators, and time-consuming sample preparation processes.
Combining optical spectroscopy with chemometrics introduces an innovative, cost-effective approach by the hand of high-resolution continuum source atomic and molecular absorption spectrometry (HR-CS-AAS and HR-CS-MAS) for the analysis of isotope ratios in Li, B, N, Mg, and Ca. By analyzing the atomic or molecular absorption spectrum of the in-situ generated cloud of atoms of diatomic molecules (e.g., Li, BH, NO, MgF, CaF) during the electronic transition from the fundamental state, this method allows for the rapid determination of isotope ratios directly from sample solutions without the need for complex sample preparation.
For each element, the respective atomic or molecule's absorption spectrum was deconvoluted into its isotopic components using partial least squares regression or machine learning algorithms. Robust calibration models were developed, calibrated with enriched isotope, and validated against certified reference materials. Spectral data underwent preprocessing to optimize the modeling to determine the optimal number of latent variables.
The findings showcase that this optical spectrometric method yields results that agree with those obtained via inductively coupled plasma mass spectrometry (ICP-MS), offering a promising, cost-effective, and rapid alternative for isotope analysis with precisions as low as ± 0.2‰. This approach is a significant advancement in analytical chemistry, providing a new way to study isotope variations in biological, environmental, and geological samples.
What does GD-OES reveal about the aging and manufacturing processes of lithium-ion batteries?
(2024)
Glow-Discharge Optical Emission Spectroscopy (GD-OES), a powerful analytical technique, sheds light on the two critical aspects of lithium-ion batteries (LIBs): manufacturing and aging 1, 2. We optimized cell production in manufacturing by adjusting parameters, including cathode doping, electrolyte concentration, and pressing force. GD-OES provided in-depth elemental composition and homogeneity analysis, which is crucial for identifying optimal manufacturing conditions. These findings were validated by electrochemical impedance spectroscopy, confirming the quality of the manufactured batteries.
Shifting the focus to aging, we use GD-OES for fluorine depth profiling, a key element in understanding polymer and electrolyte degradation. However, fluorine presents analytical challenges. We addressed this by substituting argon with a neon:argon mixture, which significantly enhanced fluorine detection sensitivity. This advancement not only improves accuracy but also holds the potential to guide sustainable and cost-efficient manufacturing strategies.
Through its versatility, GD-OES has proven to be a powerful tool for not only optimizing LIB manufacturing processes but also gaining deeper insights into their aging mechanisms. This research extends beyond academic interest, offering tangible benefits for the industry by translating into improved battery quality, extended lifespan, and overall performance.
-Über 80 Mio. Schwellen im deutschen Schienennetz verbaut
-Lebensdauer einer Schwelle beträgt ca. 20 bis 50 Jahre
-Über 2 Mio. Schwellen werden jährlich ausgetauscht, obwohl die Mehrzahl noch intakt ist
-Zustandsbewertung mittels ZfP kann Ausschuss verringern
-Schadhafte Schwellen könnten mittels ZfP frühzeitig im Gleis erkannt werden, um Gefahren und Unfälle abzuwenden
The properties of laser radiation result in a wide range of applications, making laser technologies indispensable in areas such as industry, science and medicine. The possible areas of application for thermography in this context are just as diverse. Thermography is used in laser applications when permanent monitoring and control of thermal development is necessary. Among others, this is the case in additive manufacturing, laser-based measuring devices and non-destructive testing. Furthermore, thermography is ideally suited as a testing method when it comes to ensuring the quality of the laser itself. In this talk it is outlined, how lasers can be used as a heat source in active thermographic testing. Furthermore, two special variants (spatial & temporal structured heating) are described, for which lasers are highly suitable.
Im Rahmen der von der BAM und anderen Partnern ins Leben gerufenen Initiative „Digitale Qualitätsinfrastruktur“ liegt der Fokus u.a. auf der Entwicklung von neuen Zertifizierungsworkflows. Dabei ist eine besondere Bedeutung dem Zusammenführen von Operational Technology (OT) und Informationstechnik (IT) beizumessen. Zur Datenintegration aus der Sensor-Feldebene einer Versuchs-wasserstofftankstelle wurde eine solche Infrastruktur zunächst in einer Laborumgebung aufgebaut.
Exploring the electrochemical and physical stability of lithium-ion cells exposed to liquid nitrogen
(2024)
The transport and storage of lithium-ion (Li-ion) batteries — damaged or in an undefined state — is a major safety concern for regulatory institutions, transportation companies, and manufacturers. Since (electro)chemical reactivity is exponentially temperature-dependent, cooling such batteries is an obvious measure for increasing their safety.
The present study explores the effect of cryogenic freezing on the electrochemical and physical stability of Li-ion cells. For this purpose, three different types of cells were repeatedly exposed to liquid nitrogen (LN2).
Before and after each cooling cycle, electrical and electrochemical measurements were conducted to assess the impact of the individual freezing steps. While the electrochemical behavior of the cells did not change significantly upon exposure to LN2 , it became apparent that a non-negligible number of cells suffered from physical changes (swelling) and functional failures. The latter defect was found to be caused by the current interrupt device of the cylindrical cells. This safety mechanism is triggered by the overpressure of expanding nitrogen which enters the cells at cryogenic temperatures.
This study underlines that the widely accepted reversibility of LN2 -cooling on a material scale does not allow for a direct extrapolation toward the physical integrity of full cells. Since nitrogen enters the cell at cryogenic temperatures and expands upon rethermalization, it can cause an internal overpressure. This can, in turn, lead to mechanical damage to the cell. Consequently, a more appropriate temperature condition — less extreme than direct LN2 exposure — needs to be found
The corrosion behavior of galvanized steels and zinc components under atmospheric exposure depends mostly on the corrosion product‐based cover layer formation under the prevailing conditions. The use of agar‐based gel electrolytes makes it possible to use electrochemical methods to obtain a characteristic value from these cover layers that describe their current and future protective capacity. It is shown here that different states of galvanized steel can be distinguished very well under laboratory conditions and that this method is also suitable for use under practical conditions. Based on the characteristic values and assuming future time of wetness, it is very easy to draw up a forecast for the future corrosion rate, which provides plausible values.
Rechargeable alkali metal−CO2 batteries, which combine high theoretical energy density and environmentally friendly CO2 fixation ability, have attracted worldwide attention. Unfortunately, their electrochemical performances are usually inferior for practical applications. Aiming to reveal the underlying causes, a combinatorial usage of advanced nondestructive and postmortem characterization tools is used to intensively study the failure mechanisms of Li/Na−CO2 batteries. It is found that a porous interphase layer is formed between the separator and the Li/Na anode during the overvoltage rising and battery performance decaying process. A series of control experiments are designed to identify the underlying mechanisms dictating the observed morphological evolution of Li/Na anodes, and it is found that the CO2 synergist facilitates Li/Na chemical corrosion, the process of which is further promoted by the unwanted galvanic corrosion and the electrochemical cycling conditions. A detailed compositional analysis reveals that the as-formed interphase layers under different conditions are similar in species, with the main differences being their inconsistent quantity. Theoretical calculation results not only suggest an inherent intermolecular affinity between the CO2 and the electrolyte solvent but also provide the most thermodynamically favored CO2 reaction pathways. Based on these results, important implications for the further development of rechargeable alkali metal−CO2 batteries are discussed. The current discoveries not only fundamentally enrich our knowledge of the failure mechanisms of rechargeable alkali metal−CO2 batteries but also provide mechanistic directions for protecting metal anodes to build high-reversible alkali metal−CO2 batteries.
The ongoing geo-political conflicts and the increasing need for the implementation of measures to improve the energetic system sustainability are increasing the importance of tanks for storing cryogenic fluids in the energy industry. The most common example of cryogenic tank applications is the transport of natural gas and hydrogen in their liquid form (LNG and LH2 respectively) for which, considering the same transport volume cryogenic storage ensures significantly higher transport capacities with respect storage based solely on overpressure.
A common feature of all cryogenic transported fluids is that their condition must be maintained minimizing heat leaks from the environment as much as possible. This is achieved by the implementation of thermal super Insulations (TSI) systems based on e. g. rock wool, perlites, microspheres, multilayer insulations (MLI), and vacuum which have proven to be effective in applications. However, due to the relatively short period of use in some applications, the small number of documented incidents, and the still few investigations carried out in the field, the exploitation of such systems in the cryogenic fluids transport sector still suffers from insufficient knowledge about the course and consequences of incidents. Accidents involving collisions, fires, and their combination are quite common in the transportation sector and may generate extraordinary loads on the tank and its insulation system, eventually leading to tank failure.
The present study focuses on the behavior of TSI systems in tanks when it is exposed to an external heat source representative of a hydrocarbon fire scenario. This may cause an increase of the heat flux into a tank by several orders of magnitude with respect to normal design conditions, thus inducing severe and in the TSI, causing the rapid release of flammable gas and even resulting in a Boiling Liquide Expanding Vapour Explosion (BLEVE).
To study such scenarios a test rig was developed at BAM that allows testing of TSI at industrial conditions and enables subsequent analysis of TSI samples. This test rig considers the typical double-walled design of tanks for cryogenic fluids with vacuum and an additional insulating material in the interspace. Adjustable electrical heating elements simulate the fire on one side of the double wall. This process allows the implementation of repeatable heat loads of up to 100 kW/m². The other side of the double wall is represented by a fluid-supported heat exchanger, which allows the simulation of cold or cryogenic conditions in the test rig, and to determine the heat flux transmitted through the double wall. Thus, the test rig allows thermal loading and performance analysis of TSI samples at the same time.
In the presentation, the results of diverse tested TSI systems will be presented and discussed. As a result of this study, the list of advantages and disadvantages for the choice of tested TSI expands. Within the test, all samples degraded as a consequence of a hydrocarbon fire-orientated thermal load. Strong differences in the behavior of the tested TSI systems over temperature, location, and time were observed. Additionally, the tested MLI insulations were significantly more resistant to their base materials. These results are relevant for the design, the definition of national and international regulations, the Risk assessment, and the development of safety concepts for cryogenic tanks.
To combat climate change the share of renewable energy production must increase drastically. Offshore energy production – offshore wind and power-to-X – are crucial to achieving climate targets. However, the impact of these offshore constructions – wind turbines and production platforms – on the marine environment remains unclear in many aspects. Potential sources of chemical emissions are corrosion protection systems, remobilization of contaminants from old sediments during construction, the brine of desalination plants and increased shipping for maintenance and transportation. In order to minimize the environmental impact of renewable energies, close monitoring is essential. The goal of this project is the development of a monitoring concept for an offshore power-to-X production platform.
Maritime exposure poses particular challenges for corrosion
protection in plant construction. In addition to the right choice
of materials, special design features that can have an impact
on corrosion resistance must also be taken into account to
ensure long-lasting corrosion protection. In practice, structural
crevice arrangements are unavoidable, and therefore the
crevice corrosion resistances of stainless steels are of
particular importance. These and other influences are being
investigated in this joint project.
While alkali-activated binders offer certain advantages over traditional Portland cement binders, particu¬larly in terms of resistance against chemical attacks and potentially environmental footprint, their degra¬dation mechanisms remain incompletely understood at present, specifically carbonation. Thus, this study investigates the impact of natural and accelerated carbonation (1% and 4% CO2) on three different compositions of alkali-activated concretes: 100% calcined clay (C100) binder, 100% ground blast furnace slag (S100) binder, and a 40% calcined clay and 60% blast furnace slag blend (C40S60). C100 concretes exhibit faster carbonation kinetics, with five times greater natural carbonation depths than S100. This difference diminishes under accelerated carbonation, showing a 1.5 times difference for 1% CO2 and complete carbonation for 4% CO2 at 90 days. The results thus confirm that accelerated carbonation testing of low-Ca alkali-activated concretes yields results that are not representative of natural carbonation. The C40S60 sample demonstrates a carbonation profile similar to a CEM I concrete, i.e., a high carbonation resistance. Microstructure analysis indicates the formation of three polymorphs of calcium carbonate for S100 (calcite, vaterite, and aragonite), with a higher CO2 concentration favouring aragonite over vaterite. C100 exhibits no calcium carbonates; instead, sodium carbonates form, including trona for 4% CO2 and natrite for both accelerated tests. C40S60 shows calcium and sodium carbonates, although to a lesser extent, containing predominantly calcite and minor signals of natrite. Suitable compositions, like C40S60, prove as effective during natural or accelerated carbonation tests as conventional Portland cement concrete.
3D concrete printing is an innovative new construction technology offering the potential to enable an efficient production of individual structures with less consumption of resources. The technology will mainly shape the future construction philosophy, automate the build process and help reaching the climate goals in civil engineering. From the design of a structure to the printed component, many individual steps based on different software are required which must be repeated for each new or changed structure. First, the geometry of the structure is created in a CAD program. Second, the print path is defined in a slicer software creating the machine code for the printer (G-Code). Finally, the structure can be printed. Furthermore, a numerical model of the printed structure is necessary for process optimization and control. In that way the number of test prints can be reduced, costs can be saved, and the component behavior can be predicted. For those purposes, an automated workflow allowing to run all steps or individual steps without interacting with each individual software program is required. Furthermore, changes in parameters or the exchange of parts (using a different design or different printer) must be possible in a simple manner. In the presented work, such an automated workflow based on the example of a parametrized wall element for extrusion-based concrete printing is developed. The investigated wall structure is parametrized using the global geometry parameters: height, width, thickness, radius, kind of infill structure (honey-comb, zig-zag) and number of repeated infills. All above mentioned steps are implemented via python interfaces using pydoit as workflow tool. General interfaces with prescribed input and output files are defined allowing adaptations for different software and tools. The described workflow is tested by performing a test series investigating the influence of the in-fill structure on the mechanical properties of the test walls.
Sicherheitstechnische Untersuchungen von Wasserstoff Freistrahlflammen bei Hochdruck im Realmaßstab
(2024)
Wasserstoff als Energieträger gewinnt zunehmend an Bedeutung. Die Untersuchung von Störfallauswirkungen mit Wasserstoff rückt somit stärker in den Fokus. Da Wasserstoff meist unter Druck gelagert und transportiert wird, ist ein zu betrachtendes Szenario die Freisetzung aus einer Leckage mit anschließender Zündung. Die daraus resultierende Freistrahlflamme (Jet Flame) muss hinsichtlich der in die Umgebung emittierten Wärmestrahlung charakterisiert werden. In der Literatur existieren bereits verschiedene Modelle, welche jedoch vermehrt auf Daten aus Kohlenwasserstoffflammen mit geringem Impuls basieren. Zur Überprüfung dieser Modelle wird im Zuge des BAM internen H2 Jet Flame Projektes die sicherheitstechnische Untersuchung von impulsbehafteten Wasserstoff Freistrahlflammen vorgenommen. Hierfür finden Versuche im Realmaßstab auf dem Testgelände Technische Sicherheit der BAM (BAM-TTS) statt. Gegenstand der Untersuchungen ist die Beurteilung der Auswirkungen von realistischen Freisetzungsszenarien hinsichtlich der Flammengeometrie und der freigesetzten Wärmestrahlung. Dabei werden Parameter wie Freisetzungswinkel, Leckagedurchmesser (z.Zt. 1 mm bis 30 mm), Druck (z.Zt. bis max. 250 bar) und Massenstrom (bis max. 0,5 kg/s) variiert. Zusätzlich können auch Einflüsse wie Art der Zündung, Zündort sowie Zündung mit zeitlichem Verzug untersucht werden. Gewonnene Erkenntnisse werden mit den Ergebnissen bereits vorhandener Modelle verglichen und diese im Bedarfsfall weiterentwickelt. Insbesondere wird der Fokus auf die Modellierung der freigesetzten Wärmestrahlung von Wasserstoffflammen gelegt. Herausforderung dabei stellt die IR-Vermessung und Modellierung von Sichtmodellen der Flammen dar. Die Visualisierung der Flammengeometrie wird mit Hilfe mehrerer Infrarot Kamerasystemen (aus mindestens zwei Blickwinkeln) vorgenommen.
Bisherige Messungen, die in der Literatur zu finden sind, basieren meist auf instationären Auströmbedingungen. Der hier verwendete Versuchsaufbau ermöglicht ein stationäres Ausströmen für mehrere Minuten und somit eine direkte Vergleichbarkeit mit den existierenden (stationären) Modellen.
Weiterhin ist der Versuchsstand umrüstbar für Vergleichsmessungen mit Kohlenwasserstoffen (Methan etc.) sowie Mischungen aus Wasserstoff und Kohlenwasserstoffen.
In order to reduce the human footprint of CO2 emissions and limit global warming effects hydrogen combustion is becoming increasingly important. To enable fuel cells and gas turbines to operates this carbon free fuel, unprecedently large amounts of hydrogen need to be produced and safely transported and stored. The investigation of the effects of accidents involving hydrogen is therefore becoming of outmost importance. Since hydrogen is usually stored and transported under pressure, one scenario to be considered is the release of hydrogen from a leakage with subsequent ignition. The resulting jet flame must be characterized with respect to the thermal radiation emitted into the environment to define safety regulations. Various models that characterize the resulting flame shape and radiation already exist in the literature, but these are mainly based on empirical data from hydrocarbon jet flames.[1-4] To verify these models, a H2 Jet Flame project conducted at BAM, is investigating the safety of momentum driven hydrogen jet flames. For this purpose, large-scale tests are carried out at the Test Site Technical Safety (BAM-TTS). The object of the investigations is to assess the effects of real scale release scenarios regarding flame geometry and the thermal radiation emitted. Parameters such as release angle, leakage diameter (currently 1 mm to 10 mm), pressure (currently up to max. 250 bar) and mass flow (up to max. 0.5 kg/s) are varied. In addition, influences such as the type of ignition, ignition location as well as delayed ignition can also be investigated. The gained knowledge will be compared with existing jet flame models, to validate these and identify a possible need for further development. In particular, the focus will be laid on the thermal radiation of hydrogen flames. The challenge here is the visualization and characterization of the flame geometry in an open environment. Visualization is performed using infrared (IR) camera systems from at least two viewing angles. Measurements of the heat radiation of jet flames, which can be found in the literature, are mostly based on unsteady outflow conditions.The experimental setup used here allows for the generation of a steady-state outflow for several minutes and thus a direct comparability with existing (steady-state) models. Furthermore, the tests can be carried out for comparative measurements with hydrocarbons (methane, etc.) as well as mixtures of hydrogen and hydrocarbons.