The CoCrFeMnNi alloy is one of the most notable first-generation high-entropy alloys and is also known as a Cantor alloy. This alloy was first proposed in 2004 and shows promising performance at cryogenic temperatures (CTs). Subsequent research has indicated that the equiatomic ternary CoCrNi medium-entropy alloy (MEA), as a subset of the Cantor alloy family, has better mechanical properties than the CoCrFeMnNi alloy. Interestingly, both the strength and ductility of the CoCrNi MEA are higher at CTs than at room temperature. CoCrNi-based alloys have attracted considerable attention in the metallic materials community and it is therefore important to generalize and summarize the latest progress in CoCrNi-based MEA research. The present review initially briefly introduces the discovery of the CoCrNi MEA. Subsequently, its tensile response and deformation mechanisms are summarized. In particular, the effects of parameters, such as critical resolved shear stress, stacking fault energy and short-range ordering, on the deformation behavior are discussed in detail. The methods for strengthening the CoCrNi MEA are then reviewed and divided into two categories, namely, modifying microstructures and adjusting chemical compositions. In addition, the mechanical performance of CoCrNi-based MEAs, including their dynamic shear properties, creep behavior and fracture toughness, is also deliberated. Finally, the development prospects of CoCrNi-based MEAs are proposed.

Oxygen electrocatalysis involving the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a vital role in cutting-edge energy conversion and storage technologies. In situ studies of the evolution of catalysts during oxygen electrocatalysis can provide important insights into their structure - activity relationships and stabilities under working conditions. Among the various in situ characterization tools available, in situ electron microscopy has the unique ability to perform structural and compositional analyzes with high spatial resolution. In this review, we present the latest developments in in situ and quasi-in situ electron microscopic techniques, including identical location electron microscopy, in situ liquid cell (scanning) transmission electron microscopy and in situ environmental transmission electron microscopy, and elaborate their applications in the ORR and OER. Our discussion centers on the degradation mechanism, structural evolution and structure - performance correlations of electrocatalysts. Finally, we summarize the earlier discussions and share our perspectives on the current challenges and future research directions of using in situ electron microscopy to explore oxygen electrocatalysis and related processes.

The development of high-entropy alloys (HEAs) based on the novel alloying concept of multi-principal components presents opportunities for achieving new materials with desired properties for increasingly demanding applications. In this study, a low neutron cross-section FeCrVTiNi-based HEA was developed for potential nuclear applications. A face-centred cubic (FCC) HEA with the nominal composition of FeCr_0.4V_0.3Ti_0.2Ni_1.3 is proposed based on the empirical thermodynamic models and the CALculation of PHAse diagrams (CALPHAD) calculation. Verifications of the predictions were performed, including the additive manufacturing of the proposal material and a range of microstructural characterizations and mechanical property tests. Consistent with the prediction, the as-fabricated HEA consists of a dominant FCC phase and minor Ni₃Ti precipitates. Moreover, significant chemical segregation in the alloy, as predicted by the CALPHAD modelling, was observed experimentally in the produced dendritic microstructure showing the enrichment of Ni and Ti elements in the interdendritic regions and the segregation of Cr and V elements in the dendritic cores. Heterogenous mechanical properties, including microhardness and tensile strengths, were observed along the building direction of the additively manufactured HEA. The various solid solution strengthening effects, due to the chemical segregation (in particular Cr and V elements) during solidification, are identified as significant contributing factors to the observed mechanical heterogeneity. Our study provides useful knowledge for the design and additive manufacturing of compositionally complex HEAs and their composition-microstructure-mechanical property correlation.

A new zero-dimensional alkali-metal tin mixed halide, K₆Sn₄F₁₂I₂•0.5H₂O, is synthesized by a hydrothermal method. It crystallizes in the cubic centrosymmetric space group of Fd-3m (No. 227) and its structure consists of crystal water molecules and ordered arranged [Sn₄F₁₂I₄] fundamental structural blocks trapped in [K₁₈] cages. Interestingly, K₆Sn₄F₁₂I₂•0.5H₂O exhibits a color change from colorless to orange when exposed to air. Experimental measurements combined with theoretical calculations reveal that the color change in K₆Sn₄F₁₂I₂•0.5H₂O is attributed to the loss of crystal water.

Single-atom catalysts (SACs) and hollow microstructured materials have recently undergone significant advancements in the field of catalysis. The combination of SACs and hollow microstructured materials can further endow them with extraordinary characteristics, such as high loadings, uniform active sites and unique metal-support interactions and electronic structures. In this review, we focus on the design and construction of SACs supported on hollow microstructured materials for enhancing electrocatalytic reactions. Due to these unique hollow microstructures, most of the active sites can be fully exposed in catalysis. Therefore, the atomic utilization rate is greatly improved. Furthermore, the synergistic effect of SACs and hollow microstructured supports can bring about unpredictable characteristics. The hollow microstructures not only adjust the geometry and electronic structure of the SACs to improve their activity but the SACs can also serve as an auxiliary stimulus to the intrinsic activity of the support to achieve better performance. Compared with the reported traditional dual atomic catalysts, hollow microstructures are conducive for the isolation of atomically dispersed binary atom active sites on both sides of the particle shell. Combined with the current development status, we summarize the challenges and prospects in this area. This review is conducive to the reasonable design and manufacture of advanced SACs supported on hollow materials and the promotion of their future industrial usage in energy applications.