PROGRESS IN ORGANIC COATINGS
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2022
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IF 6.206
Feng Lang,Yu Xiang,Chunguang Xiao,Duxin Li
High-frequency trend of electrical equipment puts forward higher requirements on the dielectric properties of insulating materials, especially under corona ageing environment. Therefore, a facile and effective method for improved corona resistance is essential for the development of high-frequency power systems. In this article, 4,4′-Oxydiphthalic anhydride (ODPA) was chosen as the dianhydride while 4,4′-Diaminodiphenyl ether (ODA) and 4,4′-diaminodiphenyl sulphide (SDA) as diamines. Consequently, thermally imidized ODPA-ODA-SDA copolyimides were synthesized, and the influence of ODPA and SDA on the dielectric properties was discussed. High-frequency corona ageing test was also conducted to investigate the relationship between dielectric properties and the corona resistance. From dielectric frequency spectra analysis, the ODPA-ODA-SDA copolyimide was considered to exhibit the best dielectric properties when SDA accounted for 30% mole fraction of diamine, the dielectric loss of which was 24.03% lower than that of ODPA-ODA at 20 kHz. Meanwhile, the better corona resistance property and mechanical properties were obtained, especially the corona ageing lifetime was 2.26 times higher than that of ODPA-ODA. To further improve the corona resistance property, a series of modified-PI/Al 2 O 3 nanocomposite films based on ODPA-ODA-SDA matrix were prepared by in-situ polymerization. When the content of Al 2 O 3 nanoparticles reached 12 wt%, the thermal stability was improved and the corona ageing lifetime was 6.14 times longer than that of ODPA-ODA. This experiment provides new ideas and directions for reducing mechanical and thermal performance losses as well as achieving high-efficiency corona resistance, which is expected to promote the development of advanced insulating films.
研究领域:
材料科学
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电气工程
✓ 已验证
产品关联
DOI
高影响因子
Polymers
·
2022
·Vol. 14
·期 21
·4604
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IF 4.967
Zhiqing Wu,Fan Lei,Zhiqiang Zhan,Jiangshan Luo,Gao Niu,Zhaoguo Li,Tao Yi,Shufan Chen,Bo Yang,Qiubo Fu,Zhiming Zhang
The exploding foil initiator (EFI) system has been extensively used in ignition and detonation sequences and proved to be of high safety and reliability. Polyimide is considered the ideal flyer material for EFI due to its excellent performance, including thermal stability, outstanding mechanical properties, high radiation resistance, and excellent dielectric properties. In this study, we prepared the EFI based on a polyimide (ODPA-ODA) flyer, which is spin-coated and solidified on patterned copper film in situ. The electric explosion test shows that the prepared EFI has good working performance, and the 4000 V working voltage drove the flyer to reach a maximum velocity of 5096 m/s. The polyimide morphology and chemical structure after the electric explosion was observed by microscope, SEM, XPS, and FTIR, which showed that the polyimide flyer underwent thermal deformation and complex chemical reactions during an electric explosion. A large number of polyimide bonds broke to form new carbonyl compounds, and the opening of aromatic rings was accompanied by the formation of aliphatic hydrocarbon chains. The morphology and chemical structure analysis after the electric explosion test will lay a foundation for us to further understand the working principle and evolution process of polyimide (ODPA-ODA) flyer.Keywords:exploding foil initiator;polyimide;flyer;plasma;morphology;chemical structure
研究领域:
材料科学
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爆炸物理
✓ 已验证
DOI
PubMed
高影响因子
JOURNAL OF NANOPARTICLE RESEARCH
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2014
·Vol. 16
·期 8
·1-12
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IF 2.278
Yang Ping,Chen Hsueh Shin,Zhang Qiang,Shi Ruixia,Wang Junpeng,Che Quande
To investigate the shell deposited kinetics, CdSe quantum dots (QDs) and nanorods (NRs) with a maximum length of 17 nm were fabricated via organic synthesis routes. CdSe with a hexagonal crystal structure (wurtzite) favors epitaxial growth on the {002} surfaces when well-controlled conditions were used. The morphologies and sizes of CdSe samples depended strongly on chemicals and temperature. In the case of 320 °C, CdSe NRs with adjusted length of 7–17 nm were obtained from trioctylphosphine oxide (TOPO) and tetradecylphosphonic acid (TDPA). In contrast, short CdSe NRs (less than 10 nm) were created from octadecylphosphonic acid (ODPA) and trioctylamine (TOA). Spherical CdSe QDs were further fabricated using stearic acid (SA) and TOPO at 300 °C. CdSe cores were coated with Cd 0.5 Zn 0.5 S and CdTe shells. Anisotropic growth occurred during shell deposition because CdS shells grown preferentially on the {001} facet of the CdSe core. In the case of CdSe core prepared from TOPO and TDPA, CdSe/Cd 0.5 Zn 0.5 S core/shell samples prepared from long CdSe NRs (more than 10 nm) revealed a peanut morphology while the core/shell samples created from short ones (less than 10 nm) exhibited a spherical morphology. All of the CdSe/Cd 0.5 Zn 0.5 S core/shell samples revealed a similar length to that of the CdSe cores. This phenomenon was also observed for the core/shell samples fabricated using CdSe NRs prepared by ODPA and TOA. This is ascribed to the well-developed crystal structure of CdSe NRs fabricated using an organic synthesis at high temperature. In contrast, this anisotropic growth did not occur when spherical CdSe QDs prepared from SA and TOPO and the shell (Cd 0.5 Zn 0.5 S) coating carried out using SA and TOA. To indicate the shell depositing process, CdSe NRs fabricated using TDPA and TOPO were coated with a CdTe shell. CdTe monomers were deposited on the middle and tip parts of the CdSe NRs to form a tetrapod-like morphology at 220 °C. This is ascribed to the large difference of structure of CdSe (hexagonal) and CdTe (zinc blende).
研究领域:
材料科学
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纳米技术
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化学合成
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2023
·
IF 9.5
Qiushi Hu,Yuling Huang,Xuemeng Yu,Shaokuan Gong,Yifan Wen,Yong Liu,Geng Li,Qiang Zhang,Ruquan Ye,Xihan Chen
Solar-driven photocatalysis is a promising approach for renewable energy application. H2O2 photocatalysis by metal-free graphitic carbon nitride has been gaining attention. Compared with traditional thermal catalysis, metal-free graphitic carbon nitride photocatalysis could lower material cost and achieve greener production of H2O2. Also, to better guide photocatalyst design, a fundamental understanding of the reaction mechanism is needed. Here, we develop a series of model cost-effective metal-free H2O2 photocatalysts made from graphitic carbon nitride (melem) and common imide groups. With 4,4′-oxydiphthalic anhydride (ODPA)-modified g-C3N4, a H2O2 yield rate of 10781 μmol/h·g·L could be achieved. Transient absorption and ex situ Fourier transform infrared (FTIR) measurements revealed an ultrafast charge transfer from the melem core to water with ∼3 ps to form unique N–OH intermediates. The electron withdrawing ability of the anhydride group plays a role in governing the rate of electron transfer, ensuring efficient charge separation. Our strategy represents a new way to achieve a low material cost, simple synthesizing strategy, good environment impact, and high H2O2 production for renewable energy application.
研究领域:
材料科学
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化学
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可再生能源
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催化
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF MEMBRANE SCIENCE
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2014
·
IF 4.908
Cuijia Duan,Xingming Jie,Dandan Liu,Yiming Cao,Quan Yuan
In this work a series of mixed matrix membranes (MMMs) containing metal organic frameworks (MOFs) were fabricated to investigate the influence of post-treatment on their gas separation properties. It was revealed that gas permeabilities increased considerably as treatment temperature increased from 150 °C to 180 °C and remained almost unchanged after 200 °C; gas permeability of MMMs from 200 °C treatment was about 3 times higher when compared with MMMs treated at 150 °C. From results of physical characterization including TGA , XRD , SEM, ATR-FTIR and nitrogen absorption it was inferred that higher temperature treatment induced gas permeability increase should be mainly attributed to more effective removal of residual solvent in micro-pores of MOFs; and gas permeation properties of MMMs with different treatment durations from 24 h to 96 h further confirmed our conclusion. This heat treatment induced permeability increase phenomenon was further verified by varying the polymer and MOF combinations. At the end Cu 3 (BTC) 2 /ODPA–TMPDA MMMs with different MOF loadings were prepared and the one with best performance appeared at 40 wt% loading: a dramatic increase of CO 2 permeability from 47.7 Barrer to 260.7 Barrer with almost unchanged CO 2 /CH 4 selectivity from 29.26 to 27.75.
研究领域:
化学工程
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材料科学
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膜技术
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）