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The electrochemical properties and thermal stability of the LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) material have been significantly improved by Nb 2 O 5 nanocoating. The electrochemical properties were researched systematically by various electrochemical tests, and the molar ratio of Nb 2 O 5 to NCM622 was evaluated as 0.5 mol%. Results showed that Nb 2 O 5 nanocoated sample exhibited good cyclic performance, whose capacity retention was 92.36%, whereas that of the bare NCM was only 87.59% after 200 cycles under 1C at 25 °C. In addition, the Nb 2 O 5 surface-coated sample exhibited a good discharge capacity of 164.05 mAh g−1 after 200 cycles under 1C at 60 °C. The result owing to the nano coating of Nb 2 O 5 , which greatly increased the thermal stability, thereby maintaining remarkable specific capacity even in high-temperature environments. The modified sample could maintain a relatively complete structure after cycling, whereas the bare sample had already collapsed. Based on the transmission electron microscopic images, the thickness of the coating layer was about 15 nm. The nanocoating of Nb 2 O 5 was prepared by solid-phase reaction. This method is simple and convenient, which is conducive to industrial production and commercialisation promotion. The Nb 2 O 5 surface coating can enhance the electrochemical properties of the cathode materials, as well as strengthen the thermal and structural stability, which can extend the battery life. [ABSTRACT FROM AUTHOR]

Abstract: A novel N-heterocycle multicarboxylate ligand 4-(3,5-dicarboxyphenyl)pyridine-2,6-dicarboxylic acid (H4dpda) was synthesized, and then reacted with lanthanide salts to yield a series of lanthanide metal–organic frameworks, [Ln(Hdpda)(H2O)4]·0.5(H2O) (Ln=Eu(1), Gd(2), Tb(3), Dy(4)) and [Tb1− x Eu x (Hdpda)(H2O)4]·0.5(H2O) (x =0.1–10mol%). Single crystal X-ray diffraction and powder XRD patterns confirm these MOFs are isostructural. Luminescent measurements suggest that the ligand can provide efficient sensitization for the lanthanide ion Tb(III) and Eu(III) in the mixed lanthanide MOFs. Additionally, the luminescence color of the mixed MOFs can be easily tuned from green to green–yellow, yellow, orange, red–orange and red by varying the molar ratio of Eu(III)/Tb(III). [Copyright &y& Elsevier]

Recently, organic-inorganic halide perovskite materials were investigated on gas sensing due to their excellent optical properties and gas sensitivities. Here, we designed a stable fluorescent perovskite-based sensor for NH 3 detection, in which the CH 3 NH 3 PbBr 3 (MAPbBr 3) film was deposited on the GeO 2 substrate and also capped by tetrabutylammonium (TBA) ligand as a stabilizing agent. This as-fabricated MAPbBr 3 -TBA-based sensor exhibited the relatively strong and stable photoluminescence (PL) intensity, thereby expanding the fluorescence response range for NH 3 sensing. Upon exposure to NH 3 gas, the PL intensity quenched rapidly by 62.5% with short response time (61 s) and recovery time (65 s). The sensor also possessed a linear relationship between the PL intensity and concentration of NH 3 in the range of 0–100 ppm, and presented excellent reversibility, high gas selectivity, and humidity stability. Furthermore, the NH 3 sensing mechanism was investigated based on X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Differential thermal analysis-Thermogravimetry (DTA-TG) and fluorescence lifetime measurements, in which the NH 3 molecules might permeate the capped TBA ligand and then induce structure transformation of inner MAPbBr 3 crystal. This study indicated that the as-prepared MAPbBr 3 -TBA-based sensor might provide promising applications on NH 3 gas detection. • NH 3 sensor was fabricated based on MAPbBr 3 capped by tetrabutylammonium ligand (TBA). • The PL quenching reached to 62.5% with response time (61 s) and recovery time (65 s). • The sensor possesses excellent linearity, reversibility, selectivity and anti-humidity. • NH 3 would permeate the capped TBA ligand, resulting in decomposition of perovskite. [ABSTRACT FROM AUTHOR]

• P-doping in NiSe2 promotes its electron transfers and interactions with polysulfides. • P-NiSe2 exhibits improved chemical adsorptions and catalysis of polysulfide conversions. • P-NiSe2 enables 3D growth of Li2S2/Li2S to alleviate cathode passivation. • High specific capacities and stable cycling are achieved at sulfur loadings up to 9.9 mg cm-2. [Display omitted] Although lithium-sulfur batteries have drawn widespread attentions due to their high energy densities at low costs, the scale-up applications are still hindered by issues such as dissolution of lithium polysulfides (LiPSs) and slow oxidation/reduction kinetics. Herein, we report a novel cathode composite composed of "moss-like" P-doped NiSe 2 arrays grown on activated carbon cloth substrates (P-NiSe 2 /ACC). Experiments and DFT calculations together suggest that P-doping enhances the electron transfers between P-NiSe 2 and LiPSs, leading to improved chemical adsorptions and catalytic effects towards the redox conversions of the active sulfur species. This effectively inhibits the shuttling of LiPSs and maximizes the utilization of sulfur towards high specific capacities and stable long-term cycling at high sulfur loadings. The strong interactions and effective catalysis of P-NiSe 2 on LiPSs also enables three-dimensional growth of Li 2 S 2 /Li 2 S on the P-NiSe 2 /ACC cathode, realizing effective accommodation of volume expansions and significant alleviation of cathode passivation. As a result, the P-NiSe 2 /ACC cathode provides a high specific capacity of 1211 mAh g−1 at 0.2 C and an outstanding high-rate performance of 679 mAh g−1 at 3 C. At the high sulfur loading of 9.9 mg cm−2, an area capacity of 8.42 mAh cm−2 is achieved with stable cycling for 100 charge/discharge cycles. [ABSTRACT FROM AUTHOR]

The directionally solidified Ni-based superalloy is used in gas turbine blades for advanced aircraft engines because of its high stability and favorable properties at elevated temperatures. The microstructures of superalloys degrade when they are exposed to long-term services, and the recovery of these damaged microstructures in a real turbine blade remains a considerable challenge. In this paper, the microstructural degradation in the leading edge of the serviced turbine blades and its microstructural evolution during the rejuvenation heat treatment are analyzed using scanning transmission electron microscopy. The results show that the service-exposed turbine blade suffers from significant microstructural changes, including the coalescence and coarsening of the γ′-phase, transformation of carbides, and precipitation of a topological close-packed phase. The microstructure of the γ′-phase varies between the dendritic arm and the interdendritic region, while the carbide evolution displays regional differences caused by the complex cooling patterns in blades. After the improved rejuvenation heat treatment, most degraded γ′-phases are restored in size, morphology, and volume fraction, accompanied by an increase in microhardness. Despite the variability in microstructural degradation, it is possible to recover the microstructure and microhardness of a severely overaged blade to meet the requirements of continued service. • The microstructural degradation and heat treatment for a DS turbine blade after actual services are investigated. • The degraded microstructure shows reginal differences due to of the complex cooling patterns in blades. • The microstructure and microhardness of a serviced blade can be partially recovered by heat treatment. [ABSTRACT FROM AUTHOR]