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[Display omitted] • Close-coupled nozzles for gas atomization with different gas Mach number at the outlet were designed. • The structure of gas field and the profile of gas pressure and velocity were analysed by CFD. • The cooling and solidification process of metal droplets were analysed calculated by finite difference method. • Fe-6.5wt.%Si powder was prepared and close-coupled nozzles with higher Mach number can produce finer powder. Gas velocity is a key parameter regulating the particle size and the cooling rate of the gas atomized powder applied in additive manufacturing, metal injection molding, thermal spraying, and soft magnetic composites. In this paper, on basis of the well-designed close-coupled nozzles with different gas Mach numbers at the outlet, the gas field structure was simulated by Computational Fluid Dynamics (CFD) software, and the process of cooling and solidification of Fe-6.5 wt% Si metal droplets was calculated by finite difference method. The results show that with the increase of Mach number, both the gas velocity downstream and the pressure at the base of melt delivery tube tip rise, whereas the mass flow rate of the melt decreases. The nozzles with high Mach number can produce finer powder with higher cooling rate. The median diameter of the powder prepared by the nozzle with Mach numbers of 1.0, 1.5, 2.0, and 2.5 is 44.9, 39.0, 32.5, and 29.1 μm, respectively, and the corresponding cooling rate of the metal droplet with a diameter of 80 μm is 2.85 × 104, 2.98 × 104, 3.32 × 104, and 3.50 × 104 K/s, respectively. This work provides new ideas and suggestions for the preparation of metal powder with small particle size at high cooling rate. [ABSTRACT FROM AUTHOR]

This study provides an effective surface modification method for Li-rich layered oxide (LLO, Li1.2Mn0.54Ni0.13Co0.13O2) with Al2O3 coating. Strong organic acid TFBDC (2,3,5,6-tetrafluoro-1,4-phthalic acid) accumulates near alkali metal oxide LLO to form uniform Al-TFBDC coating. Al-TFBDC modified LLO is subjected to heat treatment to form Al2O3 coating on the surface of LLO. This uniform coating protects LLO from direct contact with electrolyte and does not block the migration of Li+. Meanwhile, F− is successfully doped into LLO particles. The LLO coated with doping has clear layer structures, and its electrochemical properties have been significantly improved. The rate performance is increased by 66% at 10 C. After 150 cycles, its capacity retention rate is 92.5%, while that of uncoated LLO is only 55.8%. [ABSTRACT FROM AUTHOR]

Heterostructure engineering is crucial for enhancing gas sensing performance. However, achieving rapid response for room-temperature NO 2 sensing through rational heterostructure design remains a challenge. In this study, a Bi 2 Se 3 /SnSe 2 2D/2D heterostructure was synthesized by hydrothermal method for the rapid detection of NO 2 at room temperature. By combining Bi 2 Se 3 nanosheets with SnSe 2 nanosheets, the Bi 2 Se 3 /SnSe 2 sensor demonstrated and the lowest detection limit for NO 2 a short response time (15 s) to 10 ppm NO 2 at room temperature, reaches 25 ppb. Furthermore the sensor demonstrates significantly larger response to NO 2 than to other interfering gases, including 10 ppm NO 2 , H 2 S, NH 3 , CH 4 , CO, and SO 2 ,demonstrating its outstanding selectivity. And we discuss the mechanism of related performance enhancement., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yi, Chen, Yu, Hao and Wang.)

The widespread use of electronic equipment, such as computers, cell phones, communication devices and wireless facilities, has increased electromagnetic radiation, which can cause cancer and other diseases in humans. Furthermore, there is an urgent need for excluding the interferences in the aircraft and other precise instruments in military aspects. Therefore, minimizing and attenuating electromagnetic waves are critical issues. In this review, various two-dimensional (2D) materials and structures are discussed for microwave-absorbing and shielding in terms of 'thin, light, wide, and strong' requirements. The typical absorption and attenuation mechanisms are analysed and summarized to deliver an overall view and offer possible trends for future developments. Multiple works have revealed that 2D materials and structures are promising for use in microwave devices. In addition to conventional materials with 2D structures, we focus on new graphene-like materials, such as 2D transition metal dichalcogenides and black phosphorus, due to their beneficial absorbing and shielding properties. These 2D materials will likely play an important role in electromagnetic wave absorption and cancellation in the future. Finally, the related challenges and some new 2D materials are briefly discussed.