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187 results on '"ZHENG Xuejun"'

15. Modeling and ignition performance study of Al/Ni multilayer energy-containing microdevices.

Author

Yan, Shaoan, Zang, Junyi, Zhu, Yingfang, Tang, Tao, Chen, Xin, Li, Xingyu, Chen, Yinyu, Zheng, Xuejun, and Tang, Minghua

Subjects
FINITE element method, PERFORMANCE theory, THRESHOLD voltage, CURRENT distribution, ELECTRON beams, INERTIAL confinement fusion
Abstract

In this paper, we designed double V-shaped Al/Ni multilayer energy-containing microdevices with different V-angles, and we performed finite element modeling and simulation of the heat transfer process of the designed energy-containing microdevice. Temperature-dependent resistivity was introduced to effectively simulate the phase change during ignition. We simulated the temperature and current density distribution in the central region of the Al/Ni multilayer energy-containing microdevice and predicted the ignition voltage threshold for the specific device structure. Al/Ni multilayer energy-containing microdevices with different V-angles were prepared by electron beam evaporation technology, and ignition experiments on the prepared devices under the excitation of 47 μF capacitance were conducted. The experimental results show that the critical voltage of ignition increases with the increase in the V-angle, which verifies the correctness of the proposed finite element model. [ABSTRACT FROM AUTHOR]

Published
2023
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43. Reactant conversion–intercalation strategy toward interlayer-expanded MoS2 microflowers with superior supercapacitor performance.

Author

Wang, Jingwei, Zheng, Xuejun, Dong, Yaoyong, Chen, Longyuan, Chen, Lijuan, and He, Wenyuan

Subjects
*SUPERCAPACITORS, *SUPERCAPACITOR performance, *BIOCHEMICAL substrates, *DIFFUSION barriers, *ENERGY density, *DENSITY functional theory, *MOLYBDENUM sulfides, *THIOUREA
Abstract

In order to avoid the complicated control and fussy procedure associated with foreign species and templates in conventional synthesis strategies, a simple reactant conversion–intercalation strategy is developed to synthesize interlayer-expanded MoS2 (E-MoS2) by employing ammonium thiocyanate converted from a thiourea reactant as intercalator. In this strategy, the thiourea plays a bifunctionality role as reactant and intercalator precursor to ensure in situ embedding into the interlayers of MoS2 to expand the interlayer spacing. The optimal E-MoS2 obtained presents superior supercapacitor performance with a specific capacity of 246.8 F g−1 at 0.5 A g−1 in 1 M Na2SO4 electrolyte in a three-electrode system, outperforming pristine MoS2 prepared by a conventional hydrothermal method (42.5 F g−1 at 0.5 A g−1). Furthermore, a symmetric supercapacitor based on an E-MoS2 electrode delivers a high specific capacity of 261.3 F g−1 and energy density of 13.3 W h kg−1 at 0.5 A g−1, and excellent cycling life with 81.7% capacity retention after 3000 cycles at 2 A g−1. Density functional theory calculations reveal that the NH4+ and SCN− can be effectively adsorbed on the surface to be inserted into the interlayers during the growth of MoS2, resulting in an expanded interlayer spacing of 9.4 Å, and the favorable electrochemical performance stems from the large Na+ adsorption capacitance and low diffusion barrier of the E-MoS2. This work offers a novel intercalation strategy that may be generally applicable to other layer-structured materials, shedding some light on the development of high-performance electrode materials via interface engineering for energy applications. [ABSTRACT FROM AUTHOR]

Published
2023
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44. Feasibility Study for the Remanufacturing of H13 Steel Heat-Treated TBM Disc Cutter Rings with Uniform Wear Failure Using GMAW.

Author

Zhang, Kui, Dai, Shuhao, Jiang, Boyan, Zheng, Xuejun, Liu, Jingang, and Zhang, Xuhui

Subjects
REMANUFACTURING, GAS metal arc welding, MECHANICAL properties of metals
Abstract

Given that the heat treatment states of the base metal have a great influence on the surfacing repair layer, this paper carried out a feasibility study for the remanufacturing of the failed cutter rings of TBM disc cutters with uniform wear (hereinafter referred to as normally-worn ring) using the gas metal arc welding technology (GMAW). Firstly, this paper developed a heat treatment process route for H13 steel cutter rings. Secondly, the heat treatment process is numerically analyzed based on the developed route, and the rationality of the route is verified from the distribution characteristics of temperature, phase, and stress fields. Subsequently, heat treatment tests were carried out, and the physical and mechanical properties of the base metal samples prepared under laboratory conditions were evaluated respectively and systematically. Based on the comprehensive performance evaluation value calculated by the weighted comparative analysis method, it was clear that the comprehensive performance of the quenched base metal samples was 7.6% higher than that of the engineering cutter ring interior. Therefore, it is reasonable to replace the failed engineering cutter rings repaired under laboratory conditions with the prepared samples as economical alternatives. Finally, the remanufacturing of the base metal samples using GMAW was carried out, and then the remanufacturing performance of the base metal samples was analyzed. The study concluded that the comprehensive performance of the surfacing repair layer was slightly lower than that of the engineering cutter ring edge (4.1%), thus proving that the idea of surfacing remanufacturing of the normally-worn ring proposed in this paper was basically feasible. [ABSTRACT FROM AUTHOR]

Published
2023
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