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Your search keyword '"Deng, Jun-Bo"' showing total 94 results
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94 results on '"Deng, Jun-Bo"'

3. Construction of Permittivity-Graded Insulator Using Topology-Optimized Lattice Structure

Author

Sun, Peng, Li, Wen-Dong, Chen, Jun-Hong, Wang, Chao, Yin, Wei, Zhang, Yu-Cheng, Li, Jin-Shu, Deng, Jun-Bo, and Zhang, Guan-Jun

Abstract

Dielectrically graded insulation (DGI) is an effective means to mitigate the electric field ( ${E}$ -field) distribution of insulators. The industrial application of DGI remains at an exploratory stage due to the challenge of accurately constructing gradient dielectric properties by an efficient approach. Periodic lattice material (PLM) is a cellular material with periodically arranged unit cells, which can be used to construct graded material systems. In this study, the applicability of PLM in DGI is investigated. The PLM is composed of lattice unit cells with cylinder trusses and solid fillings, and the spatial distribution of permittivity can be modified by changing the permittivity of each unit cell in different regions. First, a quantitative prediction model of PLM’s permittivity from geometrical and material parameters (truss radius, truss permittivity, and filling permittivity) was built using finite element simulation and a feedforward neural network (FNN). The prediction error to the experimental data is less than 4.93%. Second, a construction method of lattice-graded insulator was developed and was used on a truncated cone insulator to reduce the ${E}$ -field concentration at its triple junctions. Finally, a fabrication strategy of the lattice-graded insulator combining 3-D printing and vacuum casting was proposed. The ac flashover voltage (FOV) tests show that the lattice-graded insulator exhibits a maximum FOV improvement of 14.6%, 57.8%, and 48.3% in 0.1 MPa air, C4F7N/CO2, and SF6, respectively. It is thus expected that PLM is promising for accurate and efficient DGI insulations, having the potential to be applied in actual insulation devices.

Published
2024
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17. Identification of electron and hole trap based on isothermal surface potential decay model.

Author

Shen, Wen-Wei, Mu, Hai-Bao, Zhang, Guan-Jun, Deng, Jun-Bo, and Tu, De-Min

Subjects
POLYMERS, SURFACE potential, MOLECULAR models, SPECTRAL energy distribution, LOW density polyethylene, POLYPROPYLENE
Abstract

For identifying electron and hole traps in polymeric materials, we combine the isothermal relaxation current theory and surface potential decay together and present a model called isothermal surface potential decay (ISPD). A non-contact measurement setup is specially designed, which features that energy distribution of electron or hole-type traps can be discriminated with negative or positive corona charging, respectively. By measuring the ISPD characteristics of low-density polyethylene and polypropylene films, their trap distributions are obtained, revealing the different semi-crystalline morphology of these two materials. The results we obtained may imply the essentially distinct nature of electron/hole traps: inter-chain for electron-type traps and intra-chain for hole-type traps, which is in agreement with other researchers' molecular modeling results. [ABSTRACT FROM AUTHOR]

Published
2013
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32. Surface modification of XLPE films by CF4 DBD for dielectric properties.

Author

Zhao, Ai-xuan, Chen, Xi, Chen, Si-le, Yao, Cong-wei, Zhao, Xue-feng, Deng, Jun-bo, and Zhang, Guan-jun

Subjects
CROSS-linked polyethylene insulation, ELECTRIC discharges, X-ray photoelectron spectroscopy
Abstract

Cross-linked polyethylene (XLPE) is often manufactured as pipe, film and foam products and used as electric insulation material. To improve the dielectric properties of XLPE film, CF4 dielectric barrier discharge (DBD) is applied as a surface modification method. The surface of XLPE film was modified at the low pressure of 1 kPa with different treatment time (15s, 30s, 60s, 120s, 240s and 480s). Electrical and optical characteristics are observed during DBD process, including applied voltage, measured current, photograph and emission spectra. Then, the surface properties, which are hydrophobicity, chemical composition, surface morphology, trap depth, dielectric loss and AC breakdown voltage, have been measured or observed by water contact angle test, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), isothermal relaxation current (IRC), frequency domain spectroscopy (FDS) and withstand voltage test. After the surface modification, the water contact angle, trap depth and breakdown voltage increase first and then decrease with treatment time extending. Meanwhile, the dielectric loss has an opposite trend, which represents better dielectric properties. The reason is that fluorine can reduce the surface energy, which can significantly influence the water contact angle. Better hydrophobicity can restrain the accumulation of outside pollution on the surface. Moreover, fluorine has strong electronegativity, so amorphous crystalline and impurities interface trap depth become deeper and the dielectric loss becomes lower. Therefore, appropriate DBD treatment conditions can apparently improve XLPE dielectric properties. [ABSTRACT FROM AUTHOR]

Published
2019
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