We report the atomic-scale imaging with concurrent transport measurements of the breakdown of individual multiwall carbon nanotubes inside a transmission electron microscope equipped with a piezomanipulator. We found unexpectedly three distinct breakdown sequences: namely, from the outermost wall inward, from the innermost wall outward, and alternatively between the innermost and the outmost walls. Remarkably, a significant amount of current drop was observed when an innermost wall is broken, proving unambiguously that every wall is conducting. Moreover, the breakdown of each wall in any sequence initiates in the middle of the nanotube, not at the contact, proving that the transport is not ballistic.
The action of freeze–thaw (F–T) cycles of claystone exerts a profound impact on the slope stability of open-pit mines in water-rich regions. Microstructural changes are observed as a crucial factor in determining the hydraulic characteristics and mechanical behaviors of claystone. The present work integrates a micro-X-ray computed tomography (Micro-CT) scanner, equipped with image processing and three-dimensional (3D) reconstruction capabilities, employed to observe the microstructure of claystone under varying numbers of F–T cycles (0, 10, 20, 30, and 50). Furthermore, seepage numerical simulations based on Micro-CT measurements are conducted to evaluate the hydraulic characteristics. Through meticulous microscopic observation and mechanical analysis, the damage mechanism induced by F–T cycles is revealed and the evolutionary characteristics are analyzed. The two-dimensional (2D) images of 3D reconstructed models unveil the gradual initiation propagation and coalescence of an intricate fissuring network in claystone during the F–T cycles. As the number of F–T cycles increases from 0 to 50, the 3D porosity exhibits exponential growth. Additionally, the influence of F–T cycles substantially enhances the connectivity of fissures. The seepage numerical simulations demonstrate that the evolutionary progression of fissures substantially augments the number of flow paths and enhances permeability. The increase in permeability follows an exponential trend, reflecting the distribution and evolution of fissures under F–T cycles. The impact on permeability arises from a combination of micromechanical properties and the microstructure of claystones. The present research tries to elucidate the microscopic evolution of fissures and their corresponding hydraulic properties in water-saturated claystone, offering significant insights for investigating the slope stability of open-pit mines in regions.
All-solid-state lithium-ion batteries (ASSLBs) have recently attracted significant attention, however, two major degradation processes at the composite cathode interface in ASSLBs, including side electro-chemical reactions and morphological/structural degradation, still hinder their development seriously. To overcome the above two challenges simultaneously, we propose and demonstrate a successful assembly of an elastic & sticky interfacial layer for ASSLBs by using advanced molecular layer deposition (MLD) technique. Our spectroscopic and mechanical characterization results show that the elastic and sticky Al-GL coating layer (Young’s modulus = 0.17GPa, k = 3.300 N m-1) not only suppresses interfacial side reactions, but also enables single-crystal NCM811 particles to be in close contact with the sulfide electrolyte tightly during repeated cycles. Compared to the irreversible interfacial resistance (51.74 Ω cm-2) formed between bare NCM811 and solid electrolyte during the initial charge progress, the irreversible resistance becomes much less (11.77 Ω cm-2) after Al-GL modification. Therefore, it not only shows a capacity retention of 88.0 % of the composite electrode, which is nearly 30 % higher than bare NCM811 (59.9 %) for 100 cycles at 0.2C (1C =180 mA g-1) with a mass loading of 10.2 mg cm-2 at 30 °C. Furthermore, even with a mass loading of 20.4 mg cm-2 at 60 °C, the capacity retention of 80.0 % is obtained after 1000 cycles at 1C. This work highlights the critical role of elastic and sticky coatings in maintaining the electrochemical-mechanical integrity of composite cathode materials and provides a promising avenue for developing mechanically reliable cathode materials for ASSLBs.
Nanocrystalline (NC) metals are stronger and more radiation-tolerant than their coarse-grained (CG) counterparts, but they often suffer from poor thermal stability as nanograins coarsen significantly when heated to 0.3 to 0.5 of their melting temperature (Tm). Here, we report an NC austenitic stainless steel (NC-SS) containing 1 at% lanthanum with an average grain size of 45 nm and an ultrahigh yield strength of ~2.5 GPa that exhibits exceptional thermal stability up to 1000 °C (0.75 Tm). In-situ irradiation to 40 dpa at 450 °C and ex-situ irradiation to 108 dpa at 600 °C produce neither significant grain growth nor void swelling, in contrast to significant void swelling of CG-SS at similar doses. This thermal stability is due to segregation of elemental lanthanum and (La, O, Si)-rich nanoprecipitates at grain boundaries. Microstructure dependent cluster dynamics show grain boundary sinks effectively reduce steady-state vacancy concentrations to suppress void swelling upon irradiation.
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