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In order to study the multi-mode damage and fracture mechanisms of thin-walled tubular parts with cross inner ribs (longitudinal and transverse inner ribs, LTIRs), the Gurson–Tvergaard–Needleman (GTN) model was modified with a newly proposed stress state function. Thus, tension damage and shear damage were unified by the new stress state function, which was asymmetric with respect to stress triaxiality. Tension damage dominated the modification, which coupled with the shear damage variable, ensured the optimal prediction of fractures of thin-walled tubular parts with LTIRs by the modified GTN model. This included fractures occurring at the non-rib zone (NRZ), the longitudinal rib (LIR) and the interface between the transverse rib (TIR) and the NRZ. Among them, the stripping of material from the outer surface of the tubular part was mainly caused by the shearing of built-up material in front of the rollers under a large wall thickness reduction (ΔT). Shear and tension deformation were the causes of fractures occurring at the NRZ, while axial tension under a large TIR interval (l) mainly resulted in fractures on LIRs. Fractures at the interface between the TIR and NRZ were due to the shearing applied by rib grooves and radial tension during the formation of ribs. This study can provide guidance for the manufacturing of high-performance aluminum alloy thin-walled tubular components with complex inner ribs. [ABSTRACT FROM AUTHOR]

For rechargeable aqueous Zn-ion batteries (ZIBs), MnO2 is a desirable cathode material because of its structural diversity and high theoretical capacity of ~308 mA h g−1. MnO2 materials' poor cycle life and inferior conductivity, however, continue to be key obstacles to their application in ZIBs. These problems are anticipated to be resolved by developing a nanocomposite system consisting of MnO2 and a carbon-based matrix. Herein, a series of graphite carbon-coated δ-MnO2 nanoparticles (denoted as GC-δ-MnO2-X; X = 1, 2, and 3) for ZIB cathode materials is prepared via a feasible redox route and varying the amount of KMnO4 (7, 8, and 9 mmol). Benefiting from the abundant active sites and boosted Zn2+ ion diffusion rate, the GC-δ-MnO2-2 nanoparticles (8 mmol KMnO4) display excellent capacity of 299.6 mA h g−1 at 0.3 A g−1 with good cycle stability (62% capacity retention after 1500 cycles at 2 A g−1), surpassing that of the GC-δ-MnO2-1 (7 mmol KMnO4) and GC-δ-MnO2-3 (9 mmol KMnO4) samples. Moreover, the constructed quasi-solid-state ZIBs based on the GC-δ-MnO2-2 cathode show respectable capacity of 194.3 mA h g−1 at 0.3 A g−1, as well as outstanding safe properties. [ABSTRACT FROM AUTHOR]

Manganese phosphate‐based materials show great potential in the electrochemical energy field due to the structurally flexible phosphate framework stabilizing active sites. However, the insufficient number of active sites causes unsatisfactory activity. Herein, we prepare Mn3(PO4)2 ⋅ 3H2O nanosheets via simple liquid‐phase precipitation with hydrogen peroxide as an oxidant, which conduces to expose more Mn3+ active sites, thereby accelerating the four‐electron transfer pathway during oxygen reduction reaction. Accordingly, the optimal catalyst (MnPi‐1.0) possesses excellent catalytic performance with a half‐wave potential of 0.81 V and a diffusion‐limited current density of 5.38 mA cm−2 in contrast to the 0.73 V and 5.07 mA cm−2 of the pristine one, respectively. Furthermore, the zinc‐air battery based on MnPi‐1.0 delivers a high peak power density (132 mW cm−2) and outstanding spcific capacity(797 mAh gZn−1). This work provides a facile and feasible solution to tune the density of active sites of manganese phosphate‐based materials for favorable electrochemical performance. [ABSTRACT FROM AUTHOR]