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- 3D imaging (1)
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Organisationseinheit der BAM
Plastic flow of metallic glasses proceeds intermittently in the inhomogeneous deformation regime. Mediated via shear bands, quasi-static straining gives rise to plastic instabilities that are measured as abrupt displacement bursts or pop-ins. The latter is a well-known feature in nanoindentation, where its first occurrence probes the critical and site-specific stress of nano-scale incipient shear deformation. Here we show that the statistical distribution of the stress and magnitude of the first shear instability, as well as its successive higher-order events, universally follow Weibull statistics across ten different metallic glasses. This indicates a fundamentally identical plastic process across glass-forming alloys and progressing deformation that is governed by a weakest-link phenomenon. This finding stands in strong contrast to crystalline alloys, where both defect nucleation and defect-structure evolution control shear instabilities and depend on the deformation history.
The development of all-solid-state lithium metal batteries (ASSLMBs) has pushed beyond the energy density limit of conventional liquid systems. However, stress concentration remains a critical yet poorly understood cause of degradation in ASSLMBs, particularly in widely used polycrystalline (PC) Ni-rich cathode systems. Herein, we design cavity-contained PC LiNi0.9Co0.05Mn0.05O2 (NCM) cathode particles to resolve the stress concentration problem in particle-electrode-battery multiscale by bottom-up stress management. Synchrotron X-ray tomography and multiscale finite element simulations disclose the cathode reaction heterogeneity initiates stress concentration and particle-electrode-battery multiscale mechanical-electrochemical degradation. Compared to cavity-free and multi-cavity NCM, central-cavity NCM suppressed cracking within the particles through shortened ionic transport distances and a built-in stress-relief space, enhanced (de)lithiation depth and uniformity at the cathode, reduced porosity and fracture in the electrolyte, and inhibited lithium dendrite formation at the anode, suggesting significantly improved stress uniformity in particle-electrode-battery levels. Consequently, ASSLMBs using the central-cavity NCM delivers a superior cycling stability (86.4% after 200 cycles and 81.5% after 400 cycles), outperforming both the traditional cavity-free NCM (51.6% after 200 cycles) and highly anticipated single crystal NCM (44.2% after 400 cycles). This work links particle-electrode-battery multiscale mechanical-electrochemical behavior, providing valuable insights for designing ASSLMBs with long lifespan from a holistic perspective.
Persistent and mobile trace organic contaminants (TrOCs) in urban stormwater are difficult to remove through sedimentation- or sorption-based treatment and pose a risk to aquatic ecosystems and drinking water supplies. We demonstrate that the chemical oxidant peroxydisulfate (PDS) can be activated by shrimp shell biochar at pH 7 to form reactive species that selectively react with widespread stormwater contaminants. Of 11 TrOCs tested, oxidative transformation was observed for 1,3-diphenylguanidine, 2-hydroxybenzothiazole, 1H-benzotriazole, 5-methyl-benzotriazole, and diuron during water treatment with biochar and PDS. Laboratory batch experiments conducted with street runoff and a synthetic water showed that the water matrix, containing up to 7.5 mg L-1 dissolved organic carbon and 100 mM chloride, had a minor effect on the formation of reactive species and contaminant transformation. Using a set of scavengers and probe compounds, we provide evidence for singlet oxygen (1O2) as the predominant reactive species in the biochar/PDS system, which is in agreement with the selectivity of the process to oxidize electron-rich organic contaminants. The results of our study inform new strategies for stormwater treatment using heterogeneous oxidation processes for the abatement of persistent and mobile organic contaminants.
Understanding the complicated interplay of the continuously evolving electrode materials in their inherent 3D states during the battery operating condition is of great importance for advancing rechargeable battery research.
In this regard, the synchrotron X-ray tomography technique, which enables non-destructive, multi-scale, and 3D imaging of a variety of electrode components before/during/after battery operation, becomes an essential tool to deepen this understanding. The past few years have witnessed an increasingly growing interest in applying this technique in battery research. Hence, it is time to not only summarize the already obtained battery-related Knowledge by using this technique, but also to present a fundamental elucidation of this technique to boost future studies in battery research. To this end, this review firstly introduces the fundamental principles and experimental Setups of the synchrotron X-ray tomography technique. After that, a user guide to ist application in battery research and examples of its applications in Research of various types of batteries are presented. The current review ends with a discussion of the future opportunities of this technique for next-generation rechargeable batteries research. It is expected that this review can enhance the reader’s understanding of the synchrotron X-ray tomography technique and stimulate new ideas and opportunities in battery research.
The uncontrolled Li dissolution/deposition dynamics and rapid Li pulverizations hinder the widespread deployment of Li metal batteries (LMB). Designing a Li composite electrode possessing a mechanically robust and lithiophilic three-dimensional (3D) framework represents a promising strategy to address these challenges. This study involves the preparation of three uniquely tailored Li-B-Mg composites using a combined metallurgical process of melting, casting, and rolling, along with the synergistic application of in situ X-ray computed tomography (CT) and post-mortem failure analysis to explore the most promising composite electrode candidate for LMBs. During the in-depth investigation, the optimal 70Li-B-Mg composite electrode stands out due to its robust skeleton fiber structure, uniform Li dissolution/deposition characteristics and high capacity of free-Li. Its promising prospects for enabling high-performance LMBs are showcased by the superior performance of the built Li||O2, Li||LiFePO4, Li||NCM622 and Li||NCM811 battery systems. This work offers a novel approach for exploring universally applicable and robust Li composite electrodes to realize high-performance LMBs using in situ CT analysis.
The effect of structural constriction on molecular mobility is investigated by broadband dielectric spectroscopy (BDS) within three types of molecular arrangements: monomers, oligomers and self-assembled monolayers (SAMs). While disordered monomers exhibit a variety of cooperative and local relaxation processes, the constrained nanodomains of oligomers and highly ordered structure of monolayers exhibit much hindered local molecular fluctuations. Particularly, in SAMs, motions of the silane headgroups are totally prevented whereas the polar endgroups forming the monolayer canopy show only one cooperative relaxation process. This latter molecular fluctuation is, for the first time, observed independently from other overlapping dielectric signals. Numerous electrostatic interactions among those dipolar endgroups are responsible for the strong cooperativity and heterogeneity of the canopy relaxation process. Our data analyses also revealed that the bulkiness of dipolar endgroups can disrupt the organization of the monolayer canopy thus increasing their ability to fluctuate as temperature is increased.
Laser-induced breakdown spectroscopy (LIBS) offers a tantalizing glimpse into real-time, on-the-spot aerosol analysis. Yet, the reliance on traditional lasers, with their limitations in energy and frequency, hampers optimal sample handling, dissociation, and excitation. To address those challenges, we propose a novel tactic: utilize a high repetition-rate (rep.-rate) laser with low pulse energy in combination with the two-dimensional correlation (2D-corr.) technique for sea-salt aerosols analyses. By examining the emission patterns from both the laser pulse train and individual pulses, we recognize distinctive analyte-specific rep.-rate responses, which allowed spectral reconstruction of analytes, avoiding background interferences. This discovery enabled the rep.-rate modulation for a 2D-corr. spectroscopy workflow. Consequently, we successfully differentiated between particle-related and air-species-related spectral components, obviating expensive spectrometers or intensified image detectors. For instance, the Na I at 589 nm stemming from aerosols exhibited an entirely different correlation contribution compared to O I at 777 nm, resulting in reconstructed clean aerosol-spectra without spectral peaks originated from air species. This 2D-corr. aerosol LIBS approach shows promising analytical potential streamlining aerosol particle analysis.
