Investigation of the microcrack evolution in a Ti-based bulk metallic glass matrix composite

AbstractThe initiation and evolution behavior of the shear-bands and microcracks in a Ti-based metallic-glass–matrix composite (MGMC) were investigated by using an in-situ tensile test under transmission electron microscopy (TEM). It was found that the plastic deformation of the Ti-based MGMC related with the generation of the plastic deformation zone in crystalline and shear deformation zone in glass phase near the crack tip. The dendrites can suppress the propagation of the shear band effectively. Before the rapid propagation of cracks, the extending of plastic deformation zone and shear deformation zone ahead of crack tip is the main pattern in the composite

Dopant Segregation Boosting High‐Voltage Cyclability of Layered Cathode for Sodium Ion Batteries

As a widely used approach to modify a material’s bulk properties, doping can effectively improve electrochemical properties and structural stability of various cathodes for rechargeable batteries, which usually empirically favors a uniform distribution of dopants. It is reported that dopant aggregation effectively boosts the cyclability of a Mg‐doped P2‐type layered cathode (Na0.67Ni0.33Mn0.67O2). Experimental characterization and calculation consistently reveal that randomly distributed Mg dopants tend to segregate into the Na‐layer during high‐voltage cycling, leading to the formation of high‐density precipitates. Intriguingly, such Mg‐enriched precipitates, acting as 3D network pillars, can further enhance a material’s mechanical strength, suppress cracking, and consequently benefit cyclability. This work not only deepens the understanding on dopant evolution but also offers a conceptually new approach by utilizing precipitation strengthening design to counter cracking related degradation and improve high‐voltage cyclability of layered cathodes.Improved cyclability of Mg‐doped P2‐NMM layered cathode is mainly due to suppression of cracking. Randomly distributed Mg dopants tend to segregate into precipitates during high‐voltage cycling, which can further strengthen the layered cathode and suppress cracking, leading to superior cycling stability at elevated voltage. Dopant precipitate is a new design concept to improve layered cathode cyclability.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153093/1/adma201904816.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153093/2/adma201904816-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153093/3/adma201904816_am.pd

Microstructural Study of Two-Dimensional Organic-Inorganic Hybrid Perovskite Nanosheet Degradation under Illumination

Two-dimensional (2D) organic-inorganic hybrid perovskite materials have received substantial attention because of their exceptional optoelectronic properties. Although the applications of 2D perovskite nanosheets are promising in various optoelectronic devices, which all face harsh working conditions of light exposure, little is known about the photo-stability and degradation mechanisms of these 2D perovskite nanosheets. In this work, degradation of (C4H9NH3)2PbBr4 (BA2PbBr4) nanosheets when exposed to ultraviolet (UV) light and white light is explored. The morphology, optical properties, and microstructure of the nanosheets, under different conditions of light exposure, was studied in detail. UV light is more destructive compared to white light, which both led to a nanosheet breakdown. A combination of transmission electron microscopy (TEM) imaging and electron diffraction revealed that the organic moieties are most sensitive to light exposure and partial disorder toward complete disorder takes place during light exposure. Moreover, excessive light exposure further causes a [PbBr6]4− octahedron tilt and re-ordering within the perovskite structure. This study could enrich the understanding of 2D perovskite nanosheets and their photostability, offer a new perspective in interpreting the light−perovskite interaction, and further help the design of robust and light-tunable 2D perovskite-based optoelectronic devices

Recent advances in in-situ transmission electron microscopy techniques for heterogeneous catalysis

Summary: The process of heterogeneous catalytic reaction under working conditions has long been considered a “black box”, which is mainly because of the difficulties in directly characterizing the structural changes of catalysts at the atomic level during catalytic reactions. The development of in situ transmission electron microscopy (TEM) techniques offers opportunities for introducing a realistic chemical reaction environment in TEM, making it possible to uncover the mystery of catalytic reactions. In this article, we present a comprehensive overview of the application of in situ TEM techniques in heterogeneous catalysis, highlighting its utility for observing gas-solid and liquid-solid reactions during thermal catalysis, electrocatalysis, and photocatalysis. in situ TEM has a unique advantage in revealing the complex structural changes of catalysts during chemical reactions. Revealing the real-time dynamic structure during reaction processes is crucial for understanding the intricate relationship between catalyst structure and its catalytic performance. Finally, we present a perspective on the future challenges and opportunities of in situ TEM in heterogeneous catalysis

Synthesis of highly-oriented black CsPbI3 microstructures for high-performance solar cells

Synthesis of a thin layer of perovskite with less pinholes and defects is vital for the construction of a high-performance perovskite solar cell (PSC). We report on an oriented attachment strategy to fabricate a black phase CsPbI3 highly-oriented quasi-single-crystalline microstructures film for constructing a mesoporous PSC device with enhanced power conversion efficiency, from 13.4% to 16.0%. The theoretical calculations and detailed in/ex situ characterizations demonstrate that the oriented attachment is driven by the predominant adsorption of dimethyl sulfoxide (DMSO) on the {212} facets of the yellow phase δ-CsPbI3 crystals which initially form a relatively oriented structure followed by phase transition to α-CsPbI3 crystals and merging into large highly-oriented quasi-single-crystalline microstructures film with {200} planes exposed under annealing. Our work demonstrates that the oriented attachment strategy enables the formation of highly-oriented quasi-single-crystalline microstructures films which are essential for realizing high-efficiency and stable thin film PSCs