Angewandte Physik
Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (765)
- Zeitschriftenartikel (389)
- Beitrag zu einem Tagungsband (274)
- Posterpräsentation (162)
- Buchkapitel (19)
- Dissertation (7)
- Sonstiges (5)
- Forschungsbericht (5)
- Beitrag zu einem Sammelband (4)
- Monografie (3)
Sprache
- Englisch (1644) (entfernen)
Schlagworte
- Hydrogen (82)
- Corrosion (63)
- Laser-induced periodic surface structures (LIPSS) (52)
- Safety (46)
- Ageing (45)
- Welding (33)
- Surface functionalization (29)
- Drop test (28)
- Femtosecond laser (26)
- Geothermal (26)
Organisationseinheit der BAM
- 3 Gefahrgutumschließungen; Energiespeicher (367)
- 7 Bauwerkssicherheit (204)
- 8 Zerstörungsfreie Prüfung (175)
- 9 Komponentensicherheit (173)
- 6 Materialchemie (152)
- 5 Werkstofftechnik (137)
- 3.3 Sicherheit von Transportbehältern (127)
- 3.4 Sicherheit von Lagerbehältern (118)
- 7.2 Ingenieurbau (94)
- 6.2 Material- und Oberflächentechnologien (90)
- 9.4 Integrität von Schweißverbindungen (89)
- 7.6 Korrosion und Korrosionsschutz (69)
- 1 Analytische Chemie; Referenzmaterialien (65)
- 9.0 Abteilungsleitung und andere (65)
- 2 Prozess- und Anlagensicherheit (59)
- 2.1 Sicherheit von Energieträgern (59)
- 5.1 Mikrostruktur Design und Degradation (58)
- 9.2 Versuchsanlagen und Prüftechnik (56)
- 3.0 Abteilungsleitung und andere (48)
- 8.5 Röntgenbildgebung (46)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (44)
- 3.5 Sicherheit von Gasspeichern (43)
- S Qualitätsinfrastruktur (41)
- 1.4 Prozessanalytik (36)
- 8.0 Abteilungsleitung und andere (34)
- 3.1 Sicherheit von Gefahrgutverpackungen und Batterien (28)
- 5.4 Multimateriale Fertigungsprozesse (27)
- 6.1 Oberflächen- und Dünnschichtanalyse (27)
- 7.4 Baustofftechnologie (26)
- 5.3 Polymere Verbundwerkstoffe (24)
- 5.6 Glas (24)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (23)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (23)
- 8.6 Faseroptische Sensorik (23)
- S.3 Ökodesign und Energieverbrauchskennzeichnung (23)
- 1.6 Anorganische Referenzmaterialien (21)
- 6.3 Strukturanalytik (21)
- 9.5 Tribologie und Verschleißschutz (21)
- 6.6 Physik und chemische Analytik der Polymere (19)
- 8.4 Akustische und elektromagnetische Verfahren (18)
- 5.5 Materialmodellierung (16)
- S.2 Digitalisierung der Qualitätsinfrastruktur (14)
- 3.6 Elektrochemische Energiematerialien (13)
- 5.2 Metallische Hochtemperaturwerkstoffe (13)
- 9.3 Schweißtechnische Fertigungsverfahren (13)
- 6.7 Materialsynthese und Design (12)
- 7.0 Abteilungsleitung und andere (10)
- 3.2 Gefahrguttanks und Unfallmechanik (9)
- 9.6 Additive Fertigung metallischer Komponenten (9)
- 6.4 Materialinformatik (8)
- 7.1 Baustoffe (8)
- 4 Material und Umwelt (6)
- 6.0 Abteilungsleitung und andere (6)
- P Präsident (6)
- P.0 Präsident und andere (6)
- 1.1 Anorganische Spurenanalytik (5)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (5)
- 1.3 Instrumentelle Analytik (4)
- 4.1 Biologische Materialschädigung und Referenzorganismen (4)
- S.1 Qualität im Prüfwesen (4)
- 1.2 Biophotonik (3)
- 1.7 Organische Spuren- und Lebensmittelanalytik (3)
- VP Vizepräsident (3)
- VP.1 eScience (3)
- 5.0 Abteilungsleitung und andere (2)
- 9.1 Komponenten für Energieträger (2)
- 1.9 Chemische und optische Sensorik (1)
- 4.0 Abteilungsleitung und andere (1)
- 4.2 Material-Mikrobiom Wechselwirkungen (1)
- 8.3 Thermografische Verfahren (1)
- PST Präsidiale Stabsstelle (1)
Paper des Monats
- ja (21)
A systematic, nature-inspired chemical engineering approach is employed to solve the issue of flooding in electrochemical devices. The mechanism of passive water transport utilized by lizards living in arid environments is leveraged to design flow-fields with a microchannel structure on their surface, through which capillary pressure rapidly removes the water generated in the electrochemical device. This water management strategy is implemented in proton exchange membrane fuel cells (PEMFCs) with a lunginspired flow-field, which ensures uniform distribution of reactants across the catalyst layer. Jointly, this nature-inspired approach results in flood-free, stable operation at 100% RH and a B60% increase in current (B1.9 A cm-2) and peak power density (B650 mW cm−2) compared to current PEMFCs with a flood-prone, serpentine flow-field (B0.8 A cm-2 and 280 mW cm-2, respectively). This significant advance allows for PEMFC operation at fully humidified conditions.
Evaluation of Heat Fluxes in Fire Reference Test Conducted in BAM Propane Gas Fire Test Facility
(2024)
Packages for the transport of intermediate- and high-level radioactive waste are designed to withstand severe accidents. The International Atomic Energy Agency (IAEA) has established specific mechanical and thermal tests. Packages for the transport of radioactive material must withstand these tests to comply with the Regulations for the Safe Transport of Radioactive Materials IAEA [IAEA (2018)]. A fire reference package was developed with the primary objective to demonstrate that the fire meets the regulatory requirements. Another aim is to characterise the boundary conditions of the actual fire as input parameters for thermo-mechanical simulations. A simple method to characterise the boundary conditions of a real steady state fire with a fire reference package is presented. The thermal test mainly consists of a 30 minute fully engulfing 800°C pool fire or an equally severe fire, such as a propane gas fire. The fire reference tests are performed prior to the actual fire test with the real package. The heat fluxes into the package depend substantially on the fire characteristics and the surface temperature of the package. To investigate local and overall heat fluxes over a wide range of surface temperatures in this test facility a fire reference package was designed for repeated use. The fire reference package presented in this paper represents the outer geometry of a small transport container for radioactive material and is used as a device in civil engineering. It is designed as a closed steel sheet cylinder with a wall thickness of 10 mm, a length of 182 mm and a diameter of 102 mm. The package was instrumented with thermocouples and filled with heat resistant insulation material. Open-air fire tests were performed in a BAM propane gas fire test facility with the fire reference package. The measured temperatures are used to determine the changes of heat fluxes into the fire reference package in relation to the package surface temperature. The calculated heat fluxes allow its fitting to express the thermal exposure as simple mathematical boundary condition. Therefore, in a first approach, fire properties such as adiabatic surface temperature (AST) as proposed by Wickström et al. (2007), convection coefficient and emissivity are determined mathematically fitting the heat flux development presented in this paper. The evaluated results provide an initial picture of local fire characteristics of the conducted propane gas fire and are a further development of previous works from Feldkamp et al. (2020). The results can be used in thermal and thermo-mechanical models to simulate the load on the real transport package in fire. The test shows that the examined propane gas fire covers the IAEA-fire over a wide range of surface temperatures with the chosen test stand parameters.
The Large Aperture Ultrasound System (LAUS) developed at BAM is known for its ability to penetrate thick objects, especially concrete structures commonly used in nuclear waste storage and other applications in civil engineering. Although the current system effectively penetrates up to ~9 m, further optimization is imperative to enhance the safety and integrity of disposal structures for radioactive or toxic waste. This study focuses on enhancing the system’s efficiency by optimizing the transducer spacing, ensuring that resolution is not compromised. An array of twelve horizontal shear wave transducers was used to find a balance between penetration depth and resolution. Systematic adjustments of the spacing between transmitter and receiver units were undertaken based on target depth ranges of known reflectors at depth ranges from 5 m to 10 m. The trade-offs between resolution and artifact generation were meticulously assessed. This comprehensive study employs a dual approach using both simulations and measurements to investigate the performance of transducer units spaced at 10 cm, 20 cm, 30 cm, and 40 cm. We found that for depths up to 5 m, a spacing of 10 cm for LAUS transducer units provided the best resolution as confirmed by both simulations and measurements. This optimal distance is particularly effective in achieving clear reflections and a satisfactory signal-to-noise ratio (SNR) in imaging scenarios with materials such as thick concrete structures. However, when targeting depths greater than 10 m, we recommend increasing the distance between the transducers to 20 cm. This increased spacing improves the SNR in comparison to other spacings, as seen in the simulation of a 10 m deep backwall. Our results emphasize the critical role of transducer spacing in achieving the desired SNR and resolution, especially in the context of depth imaging requirements for LAUS applications. In addition to the transducer spacing, different distances between individual sets of measurement positions were tested. Overall, keeping the minimal possible distance between measurement position offsets provides the best imaging results at greater depths. The proposed optimizations for the LAUS in this study are primarily relevant to applications on massive nuclear structures for nuclear waste management. This research highlights the need for better LAUS efficiency in applications such as sealing structures, laying the foundation for future technological advances in this field.
Ultrasonic echo testing is a well-established non-destructive testing technique used to investigate the interior of concrete structures in civil engineering. For the reconstruction of internal features, methods similar to seismic imaging are applied. To improve the ultrasonic imaging capabilities, we investigate the potential of a newly available 3D matrix mode measurement device in combination with advanced imaging techniques.
Commonly used ultrasonic array measurement devices rely on several ultrasonic transducers coupled to act as one transducer that transmits or receives transversal ultrasound waves. Although this approach is well suited to detect elongated structures such as pipes and rebars, it has limitations if 3D embedded objects are present. Hence, the ultrasonic device MiraA1040Pro used here is designed to measure the ultrasonic wavefield on a 4 by 16 matrix of individual transducers. For testing, we used laboratory specimens with linear and spheric embedded structures first. Both linear and matrix mode measurements were conducted and analysed using the Synthetic Aperture Focusing Technique
(SAFT) which is similar to Kirchhoff migration. Second, we used a data set from Teutschenthal mine at a shotcrete specimen constructed to simulate engineered barriers tailored for nuclear waste repositories. Ultrasonic measurements were investigated as a tool for quality assurance of these structures. The specimen contains both artificial 3D artifacts as well as naturally occurring defects such as a delamination. To make use of the advanced data acquisition, focusing 3D imaging techniques are applied to further improve the imaging quality.
Generally, the reconstructed images from the 3D matrix mode data have a lower level of Signal-to-Noise-Ratio than the 2D linear mode because the source signal is weaker compared to the linear mode. Moreover, complex wave conversions of the SH-transversal wave occur that are reduced in the 2D linear scenario. However, clearer images can be achieved at non-linear features, particularly with focusing imaging methods. Thus, combining 3D data acquisition techniques with advanced imaging methods improves the success in imaging complex concrete structures. This is of particular interest for thick concrete structures in nuclear barrier systems or foundations. Additionally, we demonstrate opportunities to use well-constrained test laboratory scenarios from non-destructive testing as a practical test case for geophysical methods.
AbstractThe sustainable and resource-efficient production of wind energy plants requires the use of modern high-strength fine-grain structural steels. This applies to both foundation and erection structures, like mobile or ship cranes. During the assembly of steel structures, unacceptable defects can occasionally be found in the weld area. In most cases, the economical solution would be local thermal gouging of the affected areas and re-welding. Due to the high shrinkage restraint of the joint groove in the overall structure, the superposition of global and local welding-induced stresses may lead to crack formation and component failure, particularly in interaction with the degradation of the microstructure and mechanical properties of high-strength steels during the repair process. However, manufacturers hardly have any information about these issues and there is a lack of recommendations and guidelines to take these safety-relevant aspects into account in adequate repair concepts. The aim of this research is to derive recommendations for repair concepts appropriate to the stresses and materials involved providing a basis for standards and guidelines to avoid cold cracking, damage and expensive reworking especially for high-strength steels. Part 1 of this study involves systematic investigations of influences of shrinkage restraint during repair welding of two high-strength steels S500MLO for offshore application and S960QL for mobile crane structures. The quantification of the shrinkage restraint of repair weld joints was achieved by means of experimental and numerical restraint intensity analysis. In welding experiments with self-restrained slot specimens, restraint intensity and introduction of hydrogen via the welding arc using anti spatter spray were varied systematically to analyse the effect on welding result, residual stresses and cold cracking. It could be shown that increasing restraint intensities result in significantly higher transverse residual stress levels. In the case of hydrogen introduction S500MLO showed no cold cracking independent of the restraint conditions. However, S960QL was found to be considerably cold cracking sensitive if hydrogen is introduced. With increasing restraint intensity length and number of cold cracks increases significantly. Part 2 [1] of this study is focussed on microstructure and residual stresses due to gouging and stress optimization via adequate heat control parameters in repair welding.
The high potential of hydrogen as a key factor on the pathway towards a climate neutral economy, leads to rising demand in technical applications, where gaseous hydrogen is used. For several metals, hydrogen-metal interactions could cause a degradation of the material properties. This is especially valid for low carbon and highstrength structural steels, as they are commonly used in natural gas pipelines and analyzed in this work.
This work provides an insight to the impact of hydrogen on the mechanical properties of an API 5L X65 pipeline steel tested in 60 bar gaseous hydrogen atmosphere. The analyses were performed using the hollow specimen technique with slow strain rate testing (SSRT). The nature of the crack was visualized thereafter utilizing μCT imaging of the sample pressurized with gaseous hydrogen in comparison to one tested in an inert atmosphere.
The combination of the results from non-conventional mechanical testing procedures and nondestructive imaging techniques has shown unambiguously how the exposure to hydrogen under realistic service pressure influences the mechanical properties of the material and the appearance of failure.
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.
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.
The BAM-GGR 016 explains the requirements of ADR, RID, ADN and IMDG for management systems for design, manufacturing, testing, documentation, use, maintenance, and inspection of packagings for package designs for the transport of radioactive material not requiring competent authority approval for all designs of exempted packages, packages type IP-1, IP-2, IP-3 and type A.
Wind turbines are exposed to a high number of load cycles during their service lifetime. Therefore, the fatigue strength verification plays an important role in their design. In general, the nominal stress method is used for the fatigue verification of the most common used butt-welded joints. The Eurocode 3 part 1–9 is the current design standard for this field of application. This paper presents recent results of fatigue tests on small-scaled specimens and large components with transverse butt welds to discuss the validity of the FAT-class. Furthermore, results from numerical simulations for the verification with the effective notch stress and the crack propagation approach are used for comparison. Based on the consistency between the numerical results and the fatigue tests, the influence of the seam geometry on the fatigue resistance was investigated. Finally, a prediction of the fatigue strength of butt-welded joints with plate thicknesses up to 80 mm was carried out.
The introduction of hydrogen as a safe energy carrier needs a robust knowledge base, tools for the design and safety assessment of hydrogen technologies built on it, and an internationally harmonized set of standards and regulations. Many of the innovative technologies imply hydrogen at high pressures and/or cryogenic temperatures, with which private users come into contact for the first time in distributed applications. In order to avoid over-conservative, expensive safety solutions, while at the same time demonstrating the usability and safety of hydrogen applications and maintaining acceptance for the technology, safety research must also keep pace with, or better yet anticipate, trends in technological development. Thus, this overview article describes not only the current state of knowledge and technology regarding hydrogen safety, but also its further development.
The presentation gives an overview of BAM's activities on processing influences and application properties of MPEAs in the form of joined and machined high and medium entropy alloys (CoCrFeMnNi and CoCrNi). In the case of welding, the focus is on defect-free welded joints with sufficient mechanical properties. In the case of machining, the focus is on the possible influence on the surface quality of the materials through adequate milling parameters. In addition, the hydrogen absorption and diffusion properties as well as the electrochemical corrosion behavior are fundamentally examined.
Concretes produced from salt aggregate and hybrid alkaline cements, an alkali-activated slag/fly ash blend, or a Portland cement were exposed to a magnesium chloride-rich saline solution ([Mg2+] = 3.6 m, [Cl−] = 8.3 m), representing a solution formed after contact of surface water with evaporite rock (rock salt) in a nuclear waste repository. The hydration and deterioration of the concretes were studied with X-ray diffraction, thermogravimetric analysis, pH mapping and permeability measurements. The results show that calcium silicate hydrate (C-S-H) or sodium-substituted calcium aluminium silicate hydrate (C-N-A-S-H) and Friedel's salt were the major reaction products in the concretes prior to exposure to the saline solution. During exposure to the saline solution, increasing amounts of C-S-H/C-N-A-S-H dissolved, and gypsum and a secondary AFm phase formed. The durability of the concretes improved with increasing amounts of Portland clinker in the cements, due to the associated differences in permeability and chemical resistance. Nevertheless, a massive increase of permeability occurred for all concretes, likely caused by crack formation due to the formation of gypsum from anhydrite in the salt aggregate. Thus, the behavior of the concretes differed from, and was more complex than, the behavior of plain cement pastes.
Early detection of fatigue cracks and accurate measurements of the crack growth play an important role in the maintenance and repair strategies of steel structures exposed to cyclic loads during their service life. Observation of welded connections is especially of high relevance due to their higher susceptibility to fatigue damage. The aim of this contribution was to monitor fatigue crack growth in thick welded specimens during fatigue tests as holistically as possible, by implementing multiple NDT methods simultaneously in order to record the crack initiation and propagation until the final fracture. In addition to well-known methods such as strain gauges, thermography, and ultrasound, the crack luminescence method developed at the Bundesanstalt für Materialforschung und -prüfung (BAM), which makes cracks on the surface particularly visible, was also used. For data acquisition, a first data fusion concept was developed and applied in order to synchronize the data of the different methods and to evaluate them to a large extent automatically. The resulting database can ultimately also be used to access, view, and analyze the experimental data for various NDT methods. During the conducted fatigue tests, the simultaneous measurements of the same cracking process enabled a comprehensive comparison of the methods, highlighting their individual strengths and limitations. More importantly, they showed how a synergetic combination of different NDT methods can be beneficial for implementation in large-scale fatigue testing but also in monitoring and inspection programs of in-service structures - such as the support structures of offshore wind turbines.
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.
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.
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