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Fabrication of Rigid Polyimide Foams by Constructing Dual Crosslinking Network Structures

INDUSTRIAL & engineering CHEMISTRY RESEARCH 2023年第3期62卷 1358-1372页

作者： Luo, Yinfu Ni, Long Shen, Lu Qiu, Chen Liu, Pengbo Liang, Mei Zou, Huawei Zhou, Shengtai Polymer Res Inst Sichuan Univ State Key Lab Polymer Mat Engn Chengdu 610065 Peoples R China

Herein, lightweight rigid polyimide foams (PIFs) with excellent mechanical and thermal properties were fabricated by constructing dual crosslinking structures combined with the thermal foaming of polyester ammonium salt (PEAS) precursor powders. The dual crosslinking network relied on the self-crosslinking of pararosaniline base (PA) and active crosslinking derived from the breakage of C= C bonds in 5-norbornene-2, 3-dicarboxylic anhydride (NA) under heating. The results showed that melt viscosity and micro-foaming behavior of PEASs and the cell morphology of PIFs could be regulated by varying the molar ratio of PA/NA and the number of repeating units amid crosslinking points. The compressive strength of PIF(P1BMN3-)5 (density: 165.5 kgmiddotm(-3)) with dual crosslinking structures at 10% strain reached 1.36 MPa at room temperature and 0.75 MPa at 200 degrees C. The PIFs exhibited outstanding thermal properties with the initial thermal degradation temperature falling in a temperature range of 458.2-503.0 degrees C and the glass-transition temperatures exceeding 310 degrees C. In addition, PIFs exhibited excellent thermal insulation properties since the thermal conductivity of PIFs was between 0.048 and 0.065 Wmiddotm(-1) K-1, and the temperature increase of the top surface of the cubic sample block (height: 15 mm) was approximately 20 degrees C when they were placed on a preheated hot stage at 200 degrees C for 30 min. Thus, mechanically strong rigid PIFs with dual crosslinking structures were successfully prepared, which show promising applications as lightweight, high-temperature resistant structural materials in high-end engineering fields.

关键词： Compressive strength

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Effect of adding Ni nanoparticles on the melting characteristics, mechanical properties and intermetallic compound growth of Sn58Bi solder

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SOLDERING & SURFACE MOUNT technology 2025年第1期37卷 60-70页

作者： Zhang, Jiamin Zhang, Liang Huang, Xi Wu, Chuanjiang Deng, Kai Long, Wei-Min Xiamen Univ Technol Sch Mat Sci & Engn Xiamen Peoples R China Zhengzhou Res Inst Mech Engn Co Ltd State Key Lab Adv Brazing Filler Met & Technol Zhengzhou Peoples R China

Purpose - This paper aims to investigate the improvement of Sn58Bi solder properties by Ni nanoparticle to provide theoretical support in the field of electronic packaging. Design/methodology/approach - In this study, nickel nanoparticles (Ni NPs) were doped into Sn58Bi solder as a reinforcing agent to prepare a composite solder. The wettability of composite solder, melting characteristics of solder alloy, microstructure of joints, mechanical properties and intermetallics growth at the interface were investigated. Findings - Test results show that Ni had little substantial effect on the solders alloy melting temperature yet decreased the alloy undercooling. Notably, Ni enhanced solders wettability on Cu substrates. The spreading area increased by 14% at 0.6 wt.% Ni. The Ni refined the microstructure of Sn58Bi solder joints and inhibited the coarsening of the Bi-rich phase in the solder. At the same time, it also led to the production of free intermetallic compounds, increasing growth of the intermetallic compound (IMC) layer. However, upon surpassing 0.6 wt.% Ni, (Cu, Ni)(6)Sn-5 accumulated and formed irregular clumps in the matrix. The grain size of the IMC layer gradually decreased as Ni was added. In shear tests, the fracture of joints occurred mainly inside the solder matrix. Sn58Bi-0.6Ni joints displayed a 40% rise in shear strength and a 25% rise in Vickers hardness. In addition, the appearance of dimples at the fracture indicated the improved fl exibility of joints. Originality/value - In this paper, Ni nanoparticle with different contents were added to Sn58Bi solder to prepare a composite solder, and the properties of the composite solder were investigated from different perspectives.

关键词： Ni nanoparticle Sn58Bi solder Microstructure Mechanical properties

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Laser Liftoff Enabled Batch Fabrication of Ultrathin Graphene Hall Devices

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ACS APPLIED MATERIALS & INTERFACES 2024年第49期16卷 68533-68541页

作者： Tian, Jinpeng Huang, Junqi Wang, Man Yu, Keqing Guo, Hu Luo, Wenchao Dong, Yinghui Wang, Yizhe Zhang, Zhixing Zhang, Wenwei Wang, Cheng Jia, Yuan Shenzhen Technol Univ Sino German Coll Intelligent Mfg Industrializat Ctr Micro & Nano ICs & Devices Shenzhen 518118 Peoples R China Tianjin Normal Univ Coll Elect & Commun Engn Tianjin Key Lab Wireless Mobile Commun & Power Tra Tianjin 300387 Peoples R China Tianjin Normal Univ Coll Artificial Intelligence Dept Intelligence Sci & Technol Tianjin 300387 Peoples R China Shenzhen Technol Univ Coll Integrated Circuits & Optoelect Chips Shenzhen 518118 Peoples R China Shenzhen Technol Univ Coll New Mat & New Energies Shenzhen 518118 Peoples R China Guangdong Univ Technol State Key Lab Precis Elect Mfg Technol & Equipment Guangzhou 510006 Peoples R China

When optimizing the interface between low-dimensional materials and flexible substrates, the surface properties are essential for preserving their exceptional electronic properties. This study presents an approach to fabricating flexible low-dimensional electronic devices using a laser liftoff process that enables optimal interface quality and batch fabrication. Graphene Hall sensors on 6-mu m polyimide substrates were batch-fabricated to demonstrate the utility of this approach. The sensors showed a linear response to magnetic fields up to 25 mT and an average current-normalized sensitivity of 140 V AT-1, outperforming other flexible graphene Hall devices without gate modulation or encapsulation. Owing to the ultrathin substrate, sensor-bending tests showed stable electrical characteristics under strain. The developments in this study represent a step toward extending the applications of low-dimensional flexible electronics.

关键词： laser liftoff flexible graphene electronics Hall devices batch fabrication surface properties

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Effect of doping Si3N4 nanoparticles on the properties and microstructure of Sn1.0Ag0.5Cu solder

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MATERIALS TODAY COMMUNICATIONS 2025年 43卷

作者： Chen, Mo Zhang, Liang Chen, Yu-hao Jiang, Nan Yu, Xin-quan Lu, Quan-bin Xiamen Univ Technol Sch Mat Sci & Engn Xiamen 361000 Fujian Peoples R China POSTECH Pohang Univ Sci & Technol Grad Inst Ferrous & Eco Mat Technol Pohang 790794 South Korea Harbin Inst Technol State Key Lab Precis Welding & Joining Mat & Struc Harbin 150001 Peoples R China Zhengzhou Res Inst Mech Engn State Key Lab Adv Brazing Filler Met & Technol Zhengzhou 450001 Peoples R China

This study focused on the comprehensive performance of Sn1.0Ag0.5Cu (SAC105)-Si3N4 solder joints. Changes in the wettability and thermal properties of this solder were mainly studied comprehensively, along with observations on the microstructure, intermetallic compounds (IMC) and mechanical properties of solder joints. The incorporation of Si3N4 nanoparticles (NPs) in SAC105 solder demonstrated negligible effects on its melting point, with slight fluctuations in the degree of undercooling. When the adding amount reached 0.4 wt%, the spreading area was the largest, 82.06 mm2, which was 26.67 % more than that without Si3N4 NPs. At the same time, the minimum contact angle was 18.6 degrees. Afterwards, the moderate addition of Si3N4 could significantly refine the solder joint microstructure and the IMC layer grain. Meanwhile, the highest shear strength of 29.55 MPa was achieved, reaching a significant 21.78 % enhancement in the shear strength compared to pure SAC105 solder/Cu joints. The solder joints attained a hardness value of 14.07 HV, marking a 9.6 % enhancement over SAC105 solder joints. Evidently, the judicious inclusion of Si3N4 NPs with SAC105 solder enhances the overall performance characteristics of both the solder alloy and solder joints.

关键词： Sn1.0Ag0.5Cu solder Si 3 N 4 nanoparticles IMC Microstructure Mechanical properties

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Analysis of hydrodynamic and loss characteristics of hydrofoil under the effect of tip clearance

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OCEAN engineering 2025年 316卷

作者： Wang, Hai-Yang Huang, Bin Guo, Tao Wang, Peng-Zhong Zhang, Zi-Hao Zhejiang Univ Ocean Coll Zhoushan 316021 Peoples R China Kunming Univ Sci & Technol Fac Civil Engn & Mech Kunming 650500 Peoples R China

Tip leakage flow widely exists in fluid machinery, which affects the unit's mainstream flow state and induces significant flow loss. This study explores the relationship between vortex motion and hydraulic loss in the fluid field of single hydrofoil and tandem double hydrofoils under the effect of tip clearance. The validation work indicates that the simulation results in this study align with previous experimental findings, verifying the accuracy of the method employed herein. Further analysis reveals that: (1) The existence of clearance can induce a series of vortex structures such as tip leakage vortex(TLV), tip separation vortex(TSV), hairpin vortex(HV), and wingtip vortex(WTV). The length of TLV is greatly affected by increase of clearance width. The TLV and TSV undergo three stages of generation, development, and dissipation during the fluid flows though hydrofoil, greatly affecting flow stability. (2) Vortex motion is accompanied by significant turbulent pulsation, resulting in entropy production and inducing hydraulic loss. The calculation results indicate that approximately 75% of the loss is generated in the zones of midstream and downstream(V2+V3), where the vortex structure is full developed and the vortex motion is violent. Additionally, the loss caused by turbulent dissipation term accounts for 98%, while the loss caused by viscous dissipation accounts less 2%. (3) The loss in single hydrofoil is approximately positively correlated with the clearance width, while it fluctuates with the increase of width in tandem double hydrofoils.

关键词： Tip clearance Single hydrofoil and tandem double hydrofoils Entropy production Vortexes and energy dissipation

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Doubled strength of FeSiB/316L composites and strengthening mechanism

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MATERIALIA 2024年 33卷

作者： Yu, Jingui Xiao, Jibin Zhang, Qiaoxin Zhao, Gang Lin, Shangchao Wuhan Univ Technol Sch Mech & Elect Engn Wuhan 430070 Peoples R China Shanghai Jiao Tong Univ Sch Mech & Power Engn Key Lab Power Machinery & Engn Minist Educ Shanghai 200240 Peoples R China Harbin Inst Technol State Key Lab Adv Welding & Joining Harbin 150001 Peoples R China Wuhan Univ Sci & Technol Hubei Key Lab Mech Transmiss & Mfg Engn Wuhan Peoples R China

Amorphous alloys with excellent strength and wettability are used to enhance the mechanical properties of alloys. However, the strengthening mechanism of amorphous alloy on 316 L stainless steel formed by Selective Laser Melting (SLM) needs to be further explored. In this paper, amorphous FeSiB powder is used as the reinforcing material of FeSiB/316 L composite. The strength and elongation of SLM formation of amorphous FeSiB powders with different mass fractions were studied. As the amorphous FeSiB content increased from 0 to 20 wt. %, the tensile strength of FeSiB/316 L composites increased from 632 MPa to 1222 MPa with sacrificial elongation. The strengthening mechanism is macroscopically attributed to the formation of more equiaxed crystals under the influence of amorphous FeSiB, and microscopically to the solid solution of amorphous FeSiB and its promotion of grain refinement. Meanwhile, the sacrificial elongation is due to the structural embrittlement caused by carbon segregation at the grain boundary. This study provides fundamental guidance for SLM forming of FeSiB/316 L composites with excellent mechanical properties.

关键词： Selective laser melting 316 L stainless steel Amorphous fesib power Strengthening mechanism FeSiB/316 L composite

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Foam Ni-cu enhancement of ultrasound-assisted cu/Sn58Bi/cu joint properties

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MATERIALS CHARACTERIZATION 2025年 225卷

作者： Zhang, Jia-min Zhang, Liang Chen, Yu-hao Long, Wei-min Zhang, Xiao-bin Xiamen Univ Technol Sch Mat Sci & Engn Xiamen 361000 Peoples R China Zhengzhou Res Inst Mech Engn State Key Lab Adv Brazing Filler Met & Technol Zhengzhou 450001 Peoples R China

Foam Cu-Ni possesses a three-dimensional continuous structure, making it a practical reinforcing phase to enhanced joint strength. This study employed ultrasound-assisted soldering to strengthen the bonding between foam Cu-Ni, Sn58Bi solder, and Cu substrates. The microstructure of the composite joints, the growth behavior of interfacial intermetallic compounds (IMCs), and the shear strength were systematically investigated. The study results demonstrated that ultrasonication enhanced the metallurgical reaction between Cu/Sn58Bi-foam Cu-Ni/ Cu, achieving excellent metallurgical bonding and accelerated the shaping of interfacial (Cu, Ni)6Sn5 IMC and altered the composition of the IMC layer. The average thickness of the IMC layer increased with prolonged ultrasonic time. The thickness of IMC was 2.04 mu m when no ultrasound was applied and increased to 2.79 mu m when ultrasound time reached 30s. When the ultrasonic time was lengthened, (Cu, Ni)6Sn5 grew within the matrix, establishing structural continuity with the foam Cu-Ni, significantly improved joint strength. The joint strength reached 62.47 MPa, 17.71 MPa higher strength than joints without ultrasonic treatment while the fracture characteristics showed a mixed fracture mode.

关键词： Foam cu-Ni Ultrasound-assisted Sn58Bi solder Shear strength

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An Improved PLL Control Method for DFIG Under Asymmetric Faults 27

An Improved PLL Control Method for DFIG Under Asymmetric Fau...

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27th International Conference on Electrical Machines and Systems, ICEMS 2024

作者： Kong, Xianglong Xu, Hailiang Ge, Pingjuan Chen, Xiangyu Mao, Ruitong College of New Energy Qingdao266580 China

ISBN: (纸本)9784886864406

With the continuous expansion of new energy sources, the issue of system instability caused by the large-scale integration of wind power into weak grids has become increasingly prominent. To address this challenge, this paper first develops a sequential impedance model for the doubly fed induction generator (DFIG) grid-connected system with a single-input-single-output (SISO) framework. Building upon this model, the critical role of phase-locked loop (PLL) performance in system stability is analyzed, highlighting that voltage disturbance components can significantly impair PLL performance and potentially lead to system instability. Subsequently, a voltage disturbance separation compensation (VDSC) control strategy based on an improved second-order generalized integrator frequency-locked loop (ISOGI-FLL) is proposed. Nyquist stability analysis and simulation results demonstrate that the proposed control strategy effectively enhances PLL performance and improves overall system stability. © 2024 The Institute of Electrical Engineers of Japan.

关键词： Asynchronous generators

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Influence of the Fluctuating Input on Hydrogen Production by Alkaline Water Electrolysis

Influence of the Fluctuating Input on Hydrogen Production by...

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2023 IEEE Sustainable Power and Energy Conference, iSPEC 2023

作者： Ying, Yuheng Li, Hao Zhong, Zhiyao Huang, Danji Hu, Kewei Lu, Ang Fang, Jiakun State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

ISBN: (纸本)9798350322699

Water electrolysis by renewable energy is a popular and promising solution for power-to-hydrogen. Conventional water electrolysis prefers DC voltage which needs converters and filters. However, the fluctuation cannot be completely eliminated and the effect of AC power on electrolyzers may not be entirely negative. In this paper, a multi-physics model for hydrogen production by alkaline water electrolysis has been built. Through the latency of bubble accumulation and the convexity of the I-V curve, it is been proved that the fluctuating input may have a positive effect on the hydrogen production. The transient process of the bubble accumulation has been elaborated. An integrated industrial system for hydrogen production by water electrolysis has been built for experiments. From the results, we conclude that dynamic process of the bubble on the electrode will affect the current dynamic process of the electrolyzer. The fluctuating input promotes the hydrogen production rate and reduces the energy conversion efficiency. In the specific case, a 0.7% loss in efficiency can bring 5.3% generation rate, which may be benefit for the industry. © 2023 IEEE.

关键词： bubbles power-to-hydrogen (PtH) voltage fluctuation water electrolysis

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Design of Pulse Power Supply for Nonlinear Kicker of Synchrotron Radiation Light Source 4

Design of Pulse Power Supply for Nonlinear Kicker of Synchro...

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4th IEEE China International Youth Conference on Electrical engineering, CIYCEE 2023

作者： Zhu, Bing She, Jiahao Liu, Yuan Wang, Xulong Li, Xiaofei Yang, Jun Fan, Kuanjun Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Technology School of Electrical and Electronic Engineering Wuhan430074 China China Electric Power Research Institute Wuhan430074 China

ISBN: (纸本)9798350305562

Synchrotron radiation light source has evolved into the fourth generation of diffraction-limited storage ring sources. Off-axis injection is a common approach at many leading international light sources, with the core element being Nonlinear Kicker (NLK). The pulse power supply is a critical component for ensuring the proper operation of NLK. This paper focuses on the design of pulse power supplies for NLK used in synchrotron light sources, using the off-axis injection NLK at the 1.5 GeV low-energy ring of Wuhan Light Source as a case study. The study employs Matlab/Simulink simulation to analyze the impact of various parameters on the output current of pulse power supply. The outcome of this study culminated in the design of a pulse power supply featuring a pulse current amplitude of 5440 A and a pulse width of 1 μs. © 2023 IEEE.

关键词： Light sources

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