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Flower-Branch-Like Carbon Microtube/Vanadium Selenide: A Highly Efficient Electromagnetic Wave Absorbing Composite

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SSRN 2024年

作者： Ma, Guansheng Zhang, Kaili Yan, Yuefeng Gao, Boshi Weng, Jun Qin, Guangyu Ramakrishna, Seeram Huang, Xiaoxiao Center for Nanofibers and Nanotechnology Singapore National Key Laboratory of Precision Welding & Joining of Materials and Structures Harbin Institute of Technology Harbin150001 China School of Materials Science and Engineering Harbin Institute of Technology Harbin150001 China MIIT Key Laboratory of Advanced Structural-Functional Integration Materials&Green Manufacturing Technology Harbin Institute of Technology Harbin150001 China Department of Mechanical Engineering National University of Singapore Singapore117576 Singapore

The unique layered structure and adjustable band gap of transition metal dichalcogenides (TMDs) have prompted extensive investigations into their potential for electromagnetic wave absorption (EWA). Vanadium selenide (VSe2), a notable representative of TMDs, has a larger interlayer spacing (6.1 Å) and higher conductivity (1 × 10-3 S/m), which has high advantageous in EWA applications. However, the existing research on the use of VSe2 for EWA remains relatively limited. Herein, a flower-branch-like carbon microtube/vanadium selenide (CMT/VSe2) composite was successfully synthesized via a facile solvothermal method. This composite material is composed of flower-like VSe2 nanostructures integrated with carbon microtubes. Importantly, the EWA properties of this composite can be effectively tailored by adjusting the concentration of the VSe2 precursor. The CMT/VSe2 composite exhibited a remarkable minimum reflection loss (RL) of -60.54 dB in the Ku-band, with a matching thickness of 2.27 mm. Moreover, the effective absorption bandwidth reached 6.38 GHz. These results demonstrate the great potential of this CMT/VSe2 composite material as a highly efficient EWA material. Furthermore, this work broadens the application of two-dimensional TMDs in the area of electromagnetic wave shielding and absorption. © 2024, The Authors. All rights reserved.

关键词： Transition metals

Analysis of the Texture Evolution During Multipass Tube Spinning of a Ta15 Alloy Using the Crystal Plasticity Finite Element Model

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SSRN 2023年

作者： Wang, Xianxian Wu, Wenhao Zhan, Mei Zheng, Zebang Li, Zhixin Liu, Tao School of Mechanical and Electrical Engineering Shaanxi University of Science and Technology Xi’an710021 China Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University Xi’an710072 China School of Science Civil Aviation Flight University of China Guanghan618307 China

In this study, we present an explicit crystal plasticity finite element model (CPFEM) to investigate the texture evolution during multipass tube spinning of a TA15 alloy. The texture formation mechanism is further revealed by analyzing grain rotation and slip behaviors. The results indicate that, for the grains whose c-axis are far from the normal direction (ND), basal slip is dominant under the significant compression deformation state of spinning. Therefore, the c-axis gradually turns toward the ND. However, for the grains whose c-axis are close to ND, the contribution ratios of prism , pyramidal and pyramidal increase, especially that of prism . Under these conditions, the c-axis deviates slightly from the ND, and grains mainly rotate around the c-axis. Therefore, most of the {0001} poles cluster around the ND and {10-10} poles are distributed in the rolling-hoop plane, exhibiting an obvious basal texture component. These results imply that the CPFEM can effectively predict the formation of basal texture component during spinning. With an increase in the number of spinning pass, the texture distribution becomes slightly inhomogeneous along the ND owing to the uneven distribution of macroscopic strain. In addition, the grain rotation first increases and then decreases with deformation. The smaller grain rotation at the first pass is because a large number of basal preferentially operates in the grain with favorable orientation, resulting in localized inhomogeneous deformation. The decrease at larger deformation is due to the lower Schmidt factor of basal , which limits the grain rotation. © 2023, The Authors. All rights reserved.

关键词： Prisms

Reversely tailoring antiresonant hollow-core fibers with elliptical-shaped tubes for enhanced in-line bandpass filters

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Optics Express 2025年第12期33卷 26641-26650页

作者： Jie Zhu Yu Qin Cong Xiong Wei Ji Caoyuan Wang Jonas H Osório Wei Jiang Yichun Shen Limin Xiao Advanced Fiber Devices and Systems Group Key Laboratory of Micro and Nano Photonic Structures (MoE) Key Laboratory for Information Science of Electromagnetic Waves (MoE) Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing School of Information Science and Technology Fudan University Shanghai 200433 China Zhongtian Technology Advanced Materials Co. Ltd. Nantong Jiangsu 226009 China Multiuser Laboratory of Optics and Photonics (LaMOF) Department of Physics Federal University of Lavras Lavras 37203-202 Brazil Heraeus (China) Investment Co. Ltd. Shanghai China

We report a simple and effective approach to reversely tailoring the tubes of an antiresonant hollow-core fiber (AR-HCF). The AR-HCFs with elliptical-shaped shrinkage tubes, implemented by a traditional flame brushing technique, were characterized for what we believe to be the first time. We have thus achieved a 70 nm wide bandpass filter with a minimum extra loss below 0.1 dB and the out-of-band suppression up to 28 dB in the 800 nm wide spectral range via the combination of down-tapering and reverse-tapering of AR-HCFs. The elliptical-shaped tubes can reduce the deformation-induced confinement loss when tailoring the thickness of HCF. The ability to tailor the shape and thickness of tubes of AR-HCF in a submicron-scale using a traditional flame taper rig will benefit the fabrication of in-fiber HCF devices such as the low-loss HCF bandpass filter with high out-of-band suppression.

关键词： Acoustooptic modulators Bandpass filters Fiber tapers Fresnel reflection Optical fibers Polarizers

Simultaneous Measurement of Magnetic Field and Temperature by Using 3D Printed Multicore Fiber-Tip Probes

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Simultaneous Measurement of Magnetic Field and Temperature b...

Asia Communications and Photonics Conference and Exhibition (ACP)

作者： Cong Xiong Caoyuan Wang Wei Ji Limin Xiao Advanced Fiber Devices and Systems Group Key Laboratory of Micro and Nano Photonic Structures (MoE) Key Laboratory for Information Science of Electromagnetic Waves (MoE) Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing School of Information Science and Technology Fudan Shanghai China

An ultracompact multicore fiber-tip sensor is proposed, designed, and experimentally demonstrated. The 3D printed multicore fiber-tip probes provide a highly sensitive and reliable scheme for discriminative measuremen...

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An Optimized Scanning Strategy to Mitigate Excessive Heat-Accumulation Caused by Short Scanning-Lines in Laser Powder Bed Fusion Process

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SSRN 2022年

作者： Wei, Qingsong Liu, Yanbing Li, Jikang Xu, Ke Cheng, Tan Zhao, Danlei Li, Wei Teng, Qing State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan430074 China Key Laboratory of Metallurgical Equipment and Control Technology Ministry of Education Wuhan University of Science and Technology Wuhan430081 China Hubei Key Laboratory of Mechanical Transmission and Manufacturing Engineering Wuhan University of Science and Technology Wuhan430081 China Precision Manufacturing Institute Wuhan University of Science and Technology Wuhan430081 China

In laser powder bed fusion (LPBF) additive manufacturing of components with complex geometries, short scanning-lines easily induce localized excessive heat-accumulation, resulting in poor manufacturing qualities, e.g., rough surface and low hardness, etc. An optimized scanning strategy was proposed to mitigate this heat-accumulation to be consistent with the standard case. In the proposed strategy, a specific length of scanning line without laser energy was added to each short scanning line, making each scanning line of the same length. The temperature simulation results of 1mm thin-walled and 8mm standard specimens showed that the peak temperature in the thin-walled case with traditional scanning strategy rose by 1919 K, and the melt pool diameter expanded to nearly four times that of the standard sample. After applying optimized scanning strategy, the peak temperature in thin-walled sample only rose by 436 K and the melt pool diameter was almost similar with that of the standard sample. Meanwhile, the corresponding experiments indicated that the average surface roughness and hardness of 1mm thin-walled case processed by traditional scanning was Ra70 and 320 HV10. The deformation and bumpy area can be observed on the surface, the boundary of melt tracks was not neat, the porosity was high, and the grain tended to grow up. In comparison, the average surface roughness of that processed by optimized scanning strategy decreased to Ra37 but the hardness increased to 370 HV10, and almost none of the above defects were observed. The above scanning strategy was integrated into the self-developed LPBF equipment and manufacturing process, and the thin-walled blade model was processed to verify the feasibility of the optimized scanning strategy for complex parts. Since the scanning strategy is independent of the material and process parameters, it is beneficial to improve the process and quality stability of LPBF manufacturing complex parts. © 2022, The Authors. All rights re

关键词： 3D printers

A first-principles study of the electronic structure and mechanical and optical properties of Mn-doped K₂SiF₆

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Chinese Journal of Physics 2024年 89卷 1493-1499页

作者： Zhao, Wuyan Chen, Kai Zhou, Jian Ma, Fengyang Xu, Youmin Lei, Yusheng Chen, Yi-Jinn Lillian Su, Wan-Sheng Zheng, Yuxiang Zhang, Rongjun Chen, Liangyao Wang, Songyou Shanghai Ultra-Precision Optical Manufacturing Engineering Center Department of Optical Science and Engineering Fudan University Shanghai 200433 China Institute of Optoelectronics Department of Optical Science and Engineering Fudan University Shanghai 200433 China Department of Physics National Kaohsiung Normal University Kaohsiung 824004 Taiwan National Taiwan Science Education Center Taipei 111081 Taiwan Department of Electro-Optical Engineering National Taipei University of Technology Taipei 106344 Taiwan National Applied Research Laboratories Taiwan Semiconductor Research Institute Hsinchu 300091 Taiwan Key Laboratory for Information Science of Electromagnetic Waves (MoE) Shanghai 200433 China

The lattice constants, electronic structures, mechanical and optical properties of non-doped and Mn4+-doped K2SiF6 (KSF:Mn4+) were investigated using first-principles calculations. The calculated results show that Mn4... 详细信息

The lattice constants, electronic structures, mechanical and optical properties of non-doped and Mn⁴⁺-doped K₂SiF₆ (KSF:Mn⁴⁺) were investigated using first-principles calculations. The calculated results show that Mn⁴⁺ doping enlarges the lattice constant and cell volume of KSF. Around the Fermi energy level, there is a decrease in the peak of density of states, significantly weakening the electron localization property. Mn⁴⁺ doping induces two impurity energy levels, causing a shift in the electronic states of KSF towards to the low-energy, thereby altering in the energy band structure. This alteration results in a narrower forbidden bandwidth, which reduces the photon energy required for electron transitions. Consequently, it increases the probability of electron transitions from the valence band to the conduction band, thereby enhancing the material's photocatalytic ability in the visible and ultraviolet regions. The pressure-volume relations are described using the Birch-Murnaghan's equation of state to calculate the bulk modulus of KSF and KSF:Mn⁴⁺, which is associated to the hardness of a material under particular conditions. This study provides a theoretical basis for a better understanding of the effects of Mn⁴⁺ doping on the mechanical properties, electronic structure and optical properties of KSF. © 2024 The Physical Society of the Republic of China (Taiwan)

关键词： Electronic structure First-principles K2SiF6:Mn4+ phosphors Mechanical and optical properties

Effect mechanism analysis of low-temperature on short-circuit robustness of SiC MOSFETs

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Effect mechanism analysis of low-temperature on short-circui...

IEEE Conference on Industrial Electronics and Applications (ICIEA)

作者： Pengkai Wang Yuan Chen Xinyu Zhu Hu He Junhui Li State Key Laboratory of Precision Manufacturing for Extreme Service Performance School of Mechanical and Electrical Engineering Central South University Changsha China National Key Laboratory of Science and Technology on Reliability Physics and Application of Electronic Component The China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou China

ISBN: (数字)9798350360868

ISBN: (纸本)9798350360875

The performance of SiC MOSFETs in practical operational environments is challenged by multifaceted stress scenarios, encompassing thermal, mechanical, and electrical stress, which significantly influence their reliability and operational longevity. Consequently, a comprehensive exploration of aging precursors and failure mechanisms becomes imperative for the SiC MOSFETs under diverse stress interactions. This study focused on the impact of low- temperature storage (LTS) on short-circuit (SC) ruggedness through direct current characteristic tests (DC test), low- frequency noise tests (LFN), and failure analysis (FA) for 1.2 kV SiC MOSFETs. The outcomes revealed that LTS stress adversely affected short-circuit withstand time (SCWT). These findings provide insights into the reliability and operational lifespan of SiC MOSFETs under real-world operating conditions.

关键词： MOSFET Electron traps Temperature Silicon carbide Noise Failure analysis Logic gates

Constitutive Modelling Of The Thermal Deformation Behavior and the Processing Map for the Nickel-Based Wrought Superalloy Gh4065a

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SSRN 2024年

作者： Sun, Fuqian Li, Jiang An, Xuehan Zhu, E. Li, Fuguo State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University Xi’an710072 China AECC Aviation Power Co. Ltd Xi’an710021 China Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment Northwestern Polytechnical University Xi’an710072 China

Abstract: Thermal deformation behavior of Nickel-based wrought superalloy GH4065A was investigated through hot compression experiments under different deformation temperatures and strain rates on a Gleeble-3500 thermal simulation tester. It was found that the true stress-strain curves of the alloy exhibited dynamic softening characteristics, while the variation of flow stress was highly correlated with deformation temperature and strain rate. With the increase in deformation rate, the peak strain under the same deformation temperature was delayed, but under the deformation condition of 1030°C and a rate of 1, the peak strain was advanced due to dislocation accumulations at high strain rates migrate through the phase and generate subgrain boundaries, thereby accelerating the onset of recrystallization softening. Based on the effects of adiabatic temperature rise and friction during the thermal deformation process on flow stress, dual corrections for adiabatic and friction influences were conducted, stress-strain curves closer to reality were plotted, and a constitutive equation considering the strain compensation effect was established based on the corrected data. The thermal activation energy Q was calculated to be 910.37 kJ/mol. The correlation coefficient (R) between the predicted values and experimental values was 99.8%, with an average absolute relative error (AARE) of 5.2%, indicating a more accurate representation of the mathematical relationship between flow stress and strain. The processing map was constructed utilizing the dynamic material model theory, and the optimal thermal processing window of 1060~1090°C/0.01~0.08 s-1 was determined using the criterion of plastic flow instability. © 2024, The Authors. All rights reserved.

关键词： Constitutive models

Cryogenic Incipient Plasticity in Bicrystalline Copper with a Spherical Void and Sigma 5 Stgb by Molecular Dynamics Simulation

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SSRN 2024年

作者： Jing, Peng Shao, Bin Fan, Qichao Yang, Chuan Shi, Wenchao Liu, Hongxi School of Mechanical Engineering Jiangsu University of Science and Technology Jiangsu Zhenjiang212003 China The National Key Laboratory for Precision Hot Forming of Metals Harbin Institute of Technology Heilongjiang Harbin150001 China Institute of Machinery Manufacturing Technology China Academy of Engineering Physics Sichuan Mianyang621900 China Institute of Industry and Equipment Technology Hefei University of Technology Anhui Hefei230009 China

Grain Boundaries and voids are common defects in nanocrystalline metals and play a crucial role in plastic deformation. In this study, molecular dynamics simulation is conducted to investigate the incipient plasticity of Σ5 STGB bicrystalline Cu with a spherical void, as well as its component monocrystals at 10 K. The results show a homogeneous nucleation of an elliptical 1/6 Shockley partial dislocation loop in the monocrystals. In the void-free Σ5 STGB bicrystal, initial dislocation nucleates homogeneously in grain interior rather than from the Σ5 STGB, forming a Shockley partial dislocation loop. In the monocrystals with a large spherical void, four initial dislocations nucleate from void surface on four slip systems. In the Σ5 STGB bicrystals with a spherical void, when the void diameter is 0.5 nm, the initial dislocation is an arc-shaped Shockley partial dislocation nucleated from the Σ5 STGB. For void diameters larger than 0.5 nm, initial dislocations nucleate from void surface. Through this study, the conditions for the nucleation, number, and morphology of initial dislocations can be further understood, facilitating the evaluation of subsequent plastic deformation. This research provides theoretical support for improving the mechanical properties and the design of high-performance nanocrystalline metals. © 2024, The Authors. All rights reserved.

关键词： Molecular dynamics