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Tb–Al alloys have been frequently employed as grain boundary diffusion (GBD) sources to enhance the coercivity of Nd–Fe–B magnets. With the aim of further optimizing the diffusion efficiency of Tb and reducing the material cost of the Tb–Al alloys, NdxTb80−xAl20 alloys with various Nd substitutions for Tb have been developed as diffusion sources for a commercial sintered Nd–Fe–B magnet (N50) in this work. It is found that the binary Tb80Al20 alloy diffusion enhanced the coercivity of the magnet from 924 kA m−1 to 1718 kA m−1. Although 50 at% Tb was replaced by Nd in the diffusion alloy of Nd40Tb40Al20, the coercivity of the magnet was significantly enhanced from 924 kA m−1 to 1836 kA m−1, along with greatly enhanced thermal stability. The diffusion temperature has also been optimized to 900 °C for the highest coercivity enhancement. The microstructure characterization indicated that the dramatic performance improvement of the Nd40Tb40Al20 diffused magnet is mainly attributed to the effective construction of diffusion channels by Nd, which enables more Tb atoms to enter into the interior of the magnet along the Nd-rich grain boundary phase and, thus, a magnetically hardened shell structure can be formed deep inside the magnets. This work hence presents a potential approach to enhance the utilization efficiency of Tb in the GBD process for Nd–Fe–B magnets. [ABSTRACT FROM AUTHOR]

Low mechanical properties and easy detachment from the hydration layer at the wet interface of hydrogel limit its application as an adhesive‐flexible sensor. In this study, the composition and structure of mussel mucoprotein are replicated using sulfonyl betaine (SBMA) containing zwitterion and N‐hydroxyethyl acrylamide to be polymerized in deep eutectic solvents and integrated with a polydopamine network to create a bionic eutectic gel with exceptionally strong and wet adhesion. Water erosion is effectively inhibited by the extensive hydrogen bond and electrostatic interactions. These dynamic bonds also impart self‐healing properties to the gel, showing a self‐healing efficiency of 55.45% after 48 h healing at room temperature. The zwitterion in SBMA can preferentially react with water to form a hydrated shell to protect the hydrogen bonds and enhance the exceptional water resistance and adhesion of the gel. The peel strength of the gel on a wet substrate is up to 220.71 N m−1, and its tensile strength can reach 1.01 MPa. It also has good mass stability at both low and high temperatures. This eutectic gel has the potential to be used in flexible electronic devices and can detect human movement and bioelectrical impulses on wet skin with great sensitivity. [ABSTRACT FROM AUTHOR]

Helium is a scarce strategic resource. Currently, all economically valuable helium resources are found in natural gas reservoirs. Owing to helium's different formation and migration processes compared to natural gas's, the traditional method of collecting wellhead gas to detect helium concentration may miss helium-rich layers in the vertical direction, which will not only cause the waste of helium resources, but also restrict the study of helium migration and accumulation mechanisms. To solve this problem, we designed a helium detector based on a quadrupole mass spectrometer. Through the combination of different inlet valves, we avoided gas mixing between different vertical layers during the inlet process and realized high-spatial-resolution helium concentration detection. We applied the helium detector to the Dongsheng gas field in the northern Ordos Basin, and the instrumental detection results were consistent with the laboratory analysis results of the wellhead gas, which demonstrated the stability of the helium detector in the field environment and the reliability of the data. Meanwhile, the results showed that the distribution of helium in the plane is highly heterogeneous, and the natural gas dessert layers and the helium dessert layers do not coincide in the vertical direction. In addition, we found a good correlation between helium and hydrogen concentrations. Combining our results with previous data, we propose a hydrogen–helium migration and accumulation model, which enriches the understanding of helium accumulation mechanisms and provides a basis for future helium resource exploration. [ABSTRACT FROM AUTHOR]

The nitrogen isotopic compositions of lunar soil have important implications for the sources of lunar volatiles and even the evolution of the moon. At present, the research on the lunar nitrogen isotopic compositions is mainly based on the lunar meteorites and the samples brought back by the Apollo and Luna missions. However, volatiles adsorbed on the surface of the lunar soil may be lost due to changes in temperature and pressure, as well as vibration and shock effects when the sample is returned. At the same time, in the case of low N content in the sample, since N is the main component of the earth's atmosphere, it is easily affected by the atmosphere during the analysis process. Therefore, in situ nitrogen isotopic analysis of lunar soil on orbit is necessary to avoid the problems mentioned above and is one of the primary science goals for the Lunar Soil Volatile Measuring instrument on Chang'e-7 spacecraft. After the nitrogen purification procedure, the volatiles in lunar soil that are released through single-step or stepped heating techniques diffuse to the quadrupole mass spectrometer to obtain the N contents and isotopic compositions of the lunar soil. This paper introduces the ground test for N isotopic analysis of lunar soil in orbit according to the Lunar Soil Volatile Measuring Instrument. After long-term repeated measurements, the background and CO-corrected Air-STD 14N/15N ratio is 268.986 ± 4.310 (1SD, n = 35), and the overall reproducibility of measurements is 1.6%. The accuracy of N isotopic compositions is calculated to be better than 5%, which can distinguish different sources of N components in lunar soil. [ABSTRACT FROM AUTHOR]

Based on the low-speed communication network, a multi-energy storage operation method of DC microgrid with improved power droop control was proposed so as to realize the balanced control in three aspects: state of charge (SOC) balance, rational power distribution among energy storage units and stable bus voltage. Firstly, considering that the operation of DC microgrid varies with the different system states, the operation mode of the system was divided into three working modes according to the state of energy storage unit and load. Secondly, in order to achieve the purpose of balanced distribution of SOC of each energy storage unit, an improved droop control method was introduced to modify the droop coefficient according to the size of SOC of energy storage unit. By increasing the voltage offset, the DC bus deviation was effectively reduced. Finally, the simulation model was built in Matlab/Simulink and the experimental platform was built in RTDS. The simulation and experimental results prove the effectiveness and correctness of the proposed control strategy. [ABSTRACT FROM AUTHOR]