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Effect of CNT content on microstructure and tribological properties of CNTs/AlSi10Mg composites by LPBF

China Foundry 2025年 1-10页

作者： Jiang, Li-Yi Shen, Chao-Yi Liu, Ting-Ting Zhang, Chang-Dong Su, Xiang Xu, Wei-Wei Wang, Bo-Xiang Qi, Zhi-Xiang Liao, Wen-He School of Mechanical Engineering Nanjing Institute of Technology Nanjing 211167 China National Joint Engineering Research Center of NC forming technology and equipment School of Mechanical Engineering Nanjing University of Science and Technology Nanjing 210094 China Jiangsu Belight Laboratory State Key Laboratory of Advanced Casting Technologies Nanjing University of Science and Technology Nanjing 210094 China School of Aviation and Mechanical Engineering Changzhou Institute of Technology Jiangsu Changzhou 213032 China

In this study, carbon nanotubes (CNTs)/AlSi10Mg composite parts with CNTs contents ranging from 0.0 to 2.0wt.% were successfully fabricated via laser powder bed fusion (LPBF) with laser scan speeds ranging from 900 to 1,900 mm·s−1. Uniform dispersion of CNTs in the powders can be achieved when their content is below 2.0wt.%. In the LPBF samples, the morphology of the CNTs is found to be directly related to their content. Especially, the length of CNTs in samples prepared by LPBF increases as the CNT content increases. The length of CNTs is approximately 200–300 nm in the 1.0wt.% CNTs/AlSi10Mg composites and approximately 500–1,000 nm in the 2.0wt.% CNTs/AlSi10Mg composites. The hardness of the composites reaches its highest value of 143.3 HV when the CNTs content is 1.0wt.% and the laser scan speed is 1,300 mm·s−1. It is found that the self-lubricating properties of the CNTs improve the tribological properties of the composites. The coefficient of friction (CoF) and wear rate of the samples decrease with increasing CNT content. At a CNTs content of 2.0wt.%, the CoF and wear rate of the composite decrease by approximately 14% and 30%, respectively, compared to the unreinforced matrix. The presence of CNTs leads to a more complete and refined network microstructure within the samples. Both the CNTs and the aluminum carbide contribute to the Orowan mechanism and the Hall-Petch effect within the matrix. © Foundry Journal Agency 2025.

关键词： A aluminum matrix composites carbon nanotubes (CNTs) coefficient of friction (CoF) hardness laser powder bed fusion (LPBF) TG146.21

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Influence of n = 1 resonant magnetic perturbation on flow and turbulence towards L-H transition

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Nuclear Fusion 2025年第6期65卷

作者： Zhang, Y. Jiang, M. Guo, Z.B. Diamond, P.H. Guo, W.X. Xu, J.Q. Zhang, N. Wang, Z. Li, Z.J. Zhou, Y. Liang, A.S. Sun, T.F. Ke, R. Gong, S.B. He, X.X. Chen, W. Zhong, W.L. Southwestern Institute of Physics PO Box 432 Chengdu610041 China State Key Laboratory of Nuclear Physics and Technology Fusion Simulation Center School of Physics Peking University Beijing100871 China University of California San Diego San DiegoCA92093 United States International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electric and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China

The application of resonant magnetic perturbation (RMP) with toroidal mode number n = 1 on HL-3 tokamak inhibits the L-H transition at specific heating power. Following RMP application, the electron density increases in the outer plasma region (ρ > 0.85, where ρ is the normalized toroidal flux), while the electron/ion temperature decreases. Notably, the equilibrium flow shear in the edge region is substantially reduced. This reduction, combined with enhanced micro-instabilities driven by increased profile gradients, leads to enhanced turbulence levels. Consequently, the diminished flow shear becomes less effective in suppressing turbulence, providing a comprehensive explanation for the inhibited access to H-mode. Through a modified one-dimensional predator-prey model that incorporates the effects of RMP-induced radial magnetic perturbations, we have conducted a quantitative analysis of the turbulence and flow dynamics during the L-H transition process. Our results indicate that as the strength of magnetic perturbation increases, the turbulence intensity increases and edge flow shear decreases, in agreement with experimental observations. Additionally, we found that the L-H transition power threshold increases almost linearly with the square of the radial magnetic perturbation intensity. These results enhance our understanding of RMP-induced changes in edge plasma transport, providing valuable insights for optimizing the operation of future tokamaks and improving the performance of fusion reactors. © 2025 The Author(s). Published by IOP Publishing Ltd on behalf of the IAEA.

关键词： Tokamak devices

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Enhancing SiC/Nb brazed joints by negative thermal expansion (Sr0.2Ba0.8)TiO3 nanoparticle-coated Cu foam

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Ceramics International 2025年

作者： Han, Ao Wang, Gang Wang, Wei Zhao, Yu He, Rujie Tan, Caiwang Anhui Key Laboratory of High-performance Non-Ferrous Metal Materials Anhui Polytechnic University Wuhu241000 China of Anhui Province Wuhu241000 China School of Aviation and Materials Anhui Technical College of Mechanical and Electrical Engineering Wuhu241000 China Institute of Advanced Structure Technology Beijing Institute of Technology Beijing100081 China State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology Harbin150001 China

Negative coefficient of thermal expansion (Sr0.2Ba0.8)TiO3 (SBT) nanoparticles are produced by ball milling and twice sintering process and coated with Cu foam (Cuf) as an interlayer for brazing SiC and Nb. The influence of SBT content on the microstructural, shear strength, and fracture mechanism of SiC/Nb joints is investigated. In particular, SBT/Cuf foam is utilized to modify the coefficient of thermal expansion of the AgCuTi/SBT/Cuf/AgCuTi composite filler, resulting in a reduction of residual stresses in the joints. The residual stresses at the joints are calculated as well as analyzed the mechanism of residual stress relief by SBT. Following the introduction of the interlayer, the maximum shear strength of the joint is approximately 72 MPa, which is 164 % higher than the performance of the joint with uncoated SBT. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Negative thermal expansion

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Film cooling effectiveness in the presence of internal hole random roughness: A comprehensive analysis

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International Communications in Heat and Mass Transfer 2025年 165卷

作者： Wang, Xinyu Ye, Lin Li, Wei Zheng, Tianyi Liang, Xiyuan Liu, Cunliang School of Power and Energy Northwestern Polytechnical University Shaanxi Xi'an710129 China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University Shaanxi Xi'an710049 China Science and Technology on Altitude Simulation Laboratory Sichuan Mianyang621000 China Hunan Aviation Powerplant Research Institute Aero Engine Corporation of China Hunan Zhuzhou412002 China

Film cooling, with its excellent cooling performance, is widely applied in the active thermal protection design of aerospace propulsion systems. However, during manufacturing and service, film holes are affected by drilling processes and particle deposition, leading to significant deviations between the actual cooling structures and the original design. These deviations primarily manifest as hole blockage and increased surface roughness, which may cause cooling degradation. Therefore, it is essential to investigate the film cooling performance under structural damage and the jet-mainstream mixing mechanisms of damaged holes. This study focuses on internal roughness as a form of structural damage by investigating three levels of hole roughness—Ra = 3.1 μm (Film hole I), Ra = 35.9 μm (Film hole II), and Ra = 64.9 μm (Film hole III). The selected roughness levels and blowing ratios correspond to the practical range encountered in turbine cooling. The film cooling effectiveness distribution is measured using pressure-sensitive paint technology, and numerical simulations are conducted to analyze the flow field and support the experimental results. The results indicate that cooling degradation caused by internal roughness is mainly reflected in the reduction of high cooling effectiveness areas and the deterioration of cooling performance near the film hole exit. However, increased roughness also leads to an expansion of the film coverage in the spanwise, enhancing cooling performance downstream. Flow field analysis reveals that internal roughness increases the inhomogeneity of coolant velocity distribution inside the hole, strengthening the counter-rotating vortex pair and causing jet lift-off, which reduces the high cooling effectiveness area. Additionally, roughness-induced disturbances enhance turbulence intensity, promoting jet-mainstream mixing and increasing the overall film coverage. © 2025

关键词： Solar sails

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First-principles study on Pr-doped Bilayer Nickelate La3Ni2O7

arXiv

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arXiv 2025年

作者： Huo, Zihao Zhang, Peng Shi, Haoliang Yan, Xiaochun Duan, Defang Cui, Tian Key Laboratory of Material Simulation Methods & Software of Ministry of Education State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun130012 China MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter Shaanxi Province Key Laboratory of Advanced Functional Materials and Mesoscopic Physics School of Physics Xi’an Jiaotong University Xi’an710049 China Institute of High Pressure Physics School of Physical Science and Technology Ningbo University Ningbo315211 China

Recently, the Pr-doped Ruddlesden-Popper phase of bilayer nickelate La3Ni2O7 has been reported to exhibit a superconducting transition temperature (Tc) of 82.5 K and superconducting volume fraction of about 57 % at high pressure. However, the effect of Pr-doping on La3Ni2O7 remains unclear. Here, we studied the crystal structures and electronic properties of Pr-doped La3Ni2O7 at 0 and 15 GPa based on the first-principles calculations to explore the doping effect of Pr. Our findings indicate that the praseodymium atoms prefer to occupy the outer La-O layers site. We then investigated the evolution of crystal structures in both the ambient pressure phase and high pressure phase of La3Ni2O7 as a function of doping concentration, revealing inconsistent trends in their evolution with increasing doping levels. Finally, by fitting the bilayer two-orbital model, we propose that doping Pr may benefit for superconductivity of La3Ni2O7. These results not only can help the further experimental search of RP phase nickelate at lower pressure, but also provide helpful guide for understanding the effect of chemical pressure in isovalent doped RP phase nickelate superconductor. Copyright © 2025, The Authors. All rights reserved.

关键词： Superconducting transition temperature

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Active control of thermoacoustic instability in a lean-premixed hydrogen-enriched combustor via open-loop acoustic forcing

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Combustion and Flame 2025年 277卷

作者： Liao, Yu Choi, Yongseok Liu, Peijin Kim, Kyu Tae Guan, Yu Department of Aeronautical and Aviation Engineering The Hong Kong Polytechnic University Kowloon Hong Kong National Key Laboratory of Solid Rocket Propulsion Northwestern Polytechnical University Xi'an710072 China Department of Aerospace Engineering Korea Advanced Institute of Science and Technology Daejeon34141 Korea Republic of

Open-loop control is proven effective in mitigating self-excited oscillations in conventional hydrocarbon-fueled combustors, but its effectiveness in hydrogen-fueled combustors remains unknown. This study experimentally investigates the effectiveness of open-loop acoustic forcing in mitigating self-excited periodic thermoacoustic oscillations in a lean-premixed, hydrogen-enriched turbulent combustor. We conducted experiments across a range of hydrogen volume fractions (20% to 50%), varying both the frequencies and amplitudes of the acoustic forcing introduced via three loudspeakers positioned upstream of the combustor. For the first time, we have demonstrated the effectiveness of open-loop acoustic forcing in mitigating self-excited periodic thermoacoustic oscillations in a hydrogen-enriched combustor, with suppression effects becoming more pronounced as the hydrogen content increases. We achieve up to a 90% reduction in pressure amplitude with minimal energy input—less than 1% of the combustor's thermal power. At lower hydrogen fractions, the acoustic forcing fails to effectively decouple the flame dynamics from the acoustic field, resulting in significant oscillation amplification, with natural mode amplitudes increasing by over 2000%. A critical transition from global amplification to suppression occurs at a hydrogen volume fraction of 40%, where successful decoupling between the flame dynamics from the acoustic field is observed. These findings highlight the potential of open-loop control for mitigating thermoacoustic oscillations in hydrogen-enriched combustion systems, offering a promising approach to aid the decarbonization of gas turbines. Novelty and significance statement This study provides the first experimental evidence that open-loop acoustic forcing can effectively suppress thermoacoustic oscillations in hydrogen-enriched turbulent combustors. We show that increasing hydrogen volume fraction (20% to 50%) in the reactant mixtures enhances oscillation s

关键词： Combustors

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Research on Robust Measurement Method of Heart Rate Using Remote Photoplethysmography Based on Adversarial Learning Network with High and Low Frequency Features

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IEEE Transactions on Circuits and Systems for Video technology 2025年

作者： Zhai, Dezhao Chen, Wei Ding, Yinghao Yu, Ming Li, Qinwei Wu, Hang Tianjin University of Technology Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China People's Liberation Army Systems Engineering Institute Academy of Military Sciences Tianjin300161 China Civil Aviation University of China Tianjin Key Laboratory for Advanced Signal Processing Tianjin300300 China Nankai University School of Artificial Intelligence Tianjin300381 China

Remote Photoplethysmography (rPPG) is a non-contact method for measuring heart rate (HR) through facial video, breaking the constraints of contact measurements and offering broad application prospects. However, in real monitoring scenarios, the distance of subjects and facial illumination often vary. This leads to degradation of rPPG signals due to changes in facial resolution and light intensity. This paper presents the High and Low Frequency Feature Adversarial Learning Network (HLFF-AL), which utilizes feature space interpolation and composite feature capture to perform multi-band global and local signal extraction. By adopting an adversarial learning strategy, it enhances the capability to capture semantic information of rPPG under varying resolutions and lighting, bridging the differences in rPPG signal generation due to resolution changes. While maintaining accuracy in HR measuring, the robustness of the network is improved to achieve robust measurement of HR via rPPG. Even under high-resolution conditions, the Mean Absolute Error (MAE) for the three public datasets - unchanging lighting (COHFACE, UBFC-rPPG) and varying lighting (BUAA-MIHR) - reached 1.10 bpm, 1.64 bpm, and 4.41 bpm, respectively, with a mere 0.29 bpm difference in MAE between high and low resolutions on the BUAA-MIHR dataset. This demonstrates that HLFF-AL can predict more robust rPPG signals in various resolutions and lighting scenarios, achieving competitive results compared to state-of-the-art methods. © 1991-2012 IEEE.

关键词： Heart

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Enhancing particle heat resistance of the silicon-oxygen network skeleton in silica aerogel via Y/Yb dual-doping for thermal insulation

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Ceramics International 2025年

作者： Wu, Sijia Yu, Yuxi Luo, Zhong Huang, Liuying Fu, Zhongyi Zhao, Shuyuan College of Materials Xiamen University Xiamen361005 China China Aviation Power Machinery Research Institute Zhuzhou412002 China College of Naval Architecture & Ocean Engineering Naval University of Engineering Wuhan430033 China National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin150080 China

SiO2 aerogels are nanoporous thermal insulation materials composed of a network of interconnected nanoparticles, but they are easy to crack and collapse above 800 °C which resulting in failure of thermal insulation. To improve the temperature resistance of nanoparticles, rare earth elements yttrium (Y) and ytterbium (Yb) were introduced as an enhancement system by sol-gel method to change the chemical interaction on the chemical structure and molecular bonding, together with improving the thermal stability. TEOS as the silicon source, yttrium nitrate and ytterbium nitrate as the rare earth sources, aerogel material with a density of 0.0904 g/cm3 was prepared by adjusting the finally chosen molar ratio of Si:Y:Yb = 1:0.05:0.05. By investigating the influence of RE on the microstructure, Y and Yb were found to be involved in the molecular bonding forming Si-O-Y and Si-O-Yb and changing the surface of primary particles. The thermal stability showed that the phase transition process after 573 °C was greatly inhibited by the introduction of single or dual RE. By analyzing the high temperature microstructural evolution, the shrinkage was decreased 25 % when at 1200 °C. The Cristobalite phase above 1200 °C was inhibited due to the Y/Yb dual-doping system. Furthermore, the decomposition stability was enhanced and the crack formation was significantly reduced at 1000 °C with thermal conductivity reducing from 0.2111W/(m·K) to 0.1187 W/(m·K) after heat treatment at 1000 °C. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Sol-gel process

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High-temperature tensile failure mechanism of RTM-made composite T-joints

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Defence technology 2025年

作者： Zhang, Yujin Obara, Evance Wang, Shuai Zhu, Longyu Li, Weidong Lin, Shiyun Han, Zhilin Luo, Chuyang Center for Civil Aviation Composites Donghua University Shanghai201620 China Composite Center AVIC Manufacturing Technology Institute National Key Laboratory of Advanced Composites Beijing101300 China School of Aeronautics Chongqing Jiaotong University Chongqing400074 China College of Physics Donghua University Shanghai201620 China

This paper focuses on the high-temperature tensile failure mechanism of RTM (resin transfer moulding)-made symmetric and asymmetric composite T-joints. The failure modes as well as the load-displacement curves of symmetric (three specimens) and asymmetric (three specimens) composite T-joints were determined by tensile tests at room and high temperatures. Progressive damage models (PDMs) of symmetric and asymmetric composite T-joints at room and high temperatures were established based on mixed criteria, and the result predicted from the aforementioned PDMs were compared with experimental data. The predicted initial and final failure loads and failure modes are in good agreement with the experimental results. The failure mechanisms of composite T-joints at different temperatures were investigated by scanning electron microscopy. The results reveal that while the failure mode of asymmetric T-joints at high temperatures resembles that at room temperature, there is a difference in the failure modes of symmetric T-joints. The ultimate failure load of symmetric and asymmetric T-joints at elevated temperatures increases and reduces by 18.4% and 4.97%, albeit with a more discrete distribution. This work is expected to provide us with more knowledge about the usability of composite T-joints in elevated temperature environments. © 2025 China Ordnance Society

关键词： Tensile testing

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Observation of molecular and polymeric nitrogen stuffed NaCl ionic layers

arXiv

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arXiv 2025年

作者： Ning, Ping Tian, Yifan Liu, Guangtao Wang, Hongbo Hu, Qingyang Liu, Hanyu Zhou, Mi Ma, Yanming Key Laboratory of Material Simulation Methods and Software Ministry of Education College of Physics Jilin University Changchun130012 China State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun130012 China Center for High Pressure Science and Technology Advanced Research Beijing100094 China International Center of Future Science Jilin University Changchun130012 China

Sodium chloride (NaCl), a ubiquitous and chemically stable compound, has been considered inert under ambient conditions. Its typical B1 structure is highly isotropic without preferential direction, favoring the growth of a three-dimensional network of strong Na-Cl ionic bonds. Here, we employ first-principles structural searching and synchrotron X-ray diffraction to unravel an unexpected chemical reaction between NaCl and N2 to produce a hybrid salt-NaCl(N2)2, where N2 molecules break the isotropic NaCl structure into two-dimensional layers upon synthesis at 50 GPa. In contrast to the insulating properties of pristine NaCl, the electronic bandgap of the N2-stuffed NaCl narrowed to 1.8 eV, becoming an indirect bandgap semiconductor. Further compression to 130 GPa induced the polymerization of N atoms into zigzag N-chains. Our findings not only demonstrate the possibility of unusual N-chemistry under extreme conditions, but also suggest a feasible approach for the design of layered NaCl frameworks to modulate the polymerization of nitrogen. Copyright © 2025, The Authors. All rights reserved.

关键词： Sodium chloride

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