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Controlling the Si/C ratio in SiC matrix based on the modified polymethysilane for C/C-SiC composites with enhanced mechanical properties

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Journal of Advanced Ceramics 2024年第2期13卷 220-236页

作者： Mingdong Liao Xiebo Hu Chenghao Zhong Ping Xu Xiaodong Wang Ze Zhang Peng Zhou Mingyu Zhang Zhean Su Qizhong Huang national key laboratory of Science and Technology on High-strength structural Materials Central South UniversityChangsha 410083China

Fabricating SiC matrix with controllable Si/C ratio for C/C-SiC composites via precursor infiltration and pyrolysis is difficult to realize due to the absence of suitable precursors.Here,SiC precursors with Si-rich(Si/C=1.23),nearstoichiometric(Si/C=1.01),and C-rich(Si/C=0.88)pyrolyzed ceramics at 1200℃ were successfully synthesized by the novel modification of polymethysilane.The structure and ceramization of synthesized SiC precursors were studied,and C/C-SiC composites with similar Si/C ratio in SiC matrix were also fabricated.The results revealed that the defects and Young’s modulus of SiC matrix and the thermal residual stress on pyrolytic carbon coated carbon fiber were determined by the Si/C ratio.As a result,the Si/C ratio exerted significant effects on the crack deflection behavior and the mechanical properties of the composites.The composites with near-stoichiometric SiC matrix showed excellent mechanical properties because of the effective crack deflection and the moderate Young’s modulus of their SiC matrix.The flexural strength,flexural modulus,and compressive strength were 423±27 MPa,33.41±4.52 GPa,and 393±8 MPa,respectively.Meanwhile,after a heat treatment at 1600℃,the role of carbon fiber toughening was improved and accompanied by a decrease in mechanical properties for all composites,which was attributed to the increased defects in SiC matrix and the damaged interfaces by the thermal residual stress.

关键词： SiC precursor Si/C ratio polymethysilane C/C–SiC composites mechanical properties

Interface Design Strategy for GNS/AZ91 Composites with Semi-Coherent Structure

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Acta Metallurgica Sinica(English Letters) 2024年第3期37卷 467-483页

作者： Jing-Peng Xiong Yi-Qi Zeng Jin-Long Liu Wei-Cheng Wang Lan Luo Yong Liu key laboratory of Lightweight and High strength structural Materials of Jiangxi Province School of Advanced ManufacturingNanchang UniversityNanchang 330031China School of Physics and Materials Science Nanchang UniversityNanchang 330031China

The interfacial structure plays an important role in the mechanical properties of magnesium matrix composite(MMCs)reinforced with graphene nanosheet(GNS)due to their poor wettability with the Mg matrix.An interface design strategy was proposed to form the semi-coherent interfacial structure with superior bonding strength.The lattice mismatch and interfacial bonding strength between Mg/rare earth oxide/carbon were utilized as key characteristics to evaluate the interfacial structure.Lanthanum oxide(La2O3)was selected as the intermediate candidate due to its low lattice mismatch and high interfacial bonding strength.To identify the interfacial structure of Mg/La2O3/graphene,first-principles calculations were conducted to calculate the ideal work of separation and electronic structure of the interfaces.Results demonstrated the presence of strong ionic and covalent interactions at the interface,which theoretically verified the strong interfacial bonding strength among Mg/La2O3/graphene interfaces.To experimentally validate the interface strength,MMCs with the interface structure of Mg/La2O3/GNS were developed.The formation of in-situ La2O3 led to the successful attainment of semi-coherent structures between Mg/La2O3 and La2O3/GNS,resulting in high strength and good ductility of the composite.Overall,this work proposes a new approach to interface design in MMCs with an enhancement of mechanical properties.

关键词： Interface design strategy Magnesium matrix composite Graphene nanosheets Semi-coherent interface Mechanical properties

原位反应法制备Zr/Hf-ZrC_(1-x)/HfC_(1-x)棒的碳化机制及烧蚀行为

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Journal of Central South University 2024年第3期31卷 679-692页

作者：田甜卿馨孙威楚宇昊 State key laboratory of Powder Metallurgy Central South UniversityChangsha 410083China national key laboratory of Science and Technology on High-strength structural Materials Central South UniversityChangsha 410083China

采用碳扩散原位反应法制备了Zr/Hf-ZrC_(1-x)/HfC_(1-x)棒,研究了不同的碳化温度和碳源对棒材微观结构和烧蚀行为的影响。研究结果表明,由于HfC和ZrC的无限固溶,在Zr-Hf合金棒中形成了一种双层结构,外层为ZrC/HfC层,内层为含有ZrC_(1-x)... 详细信息

采用碳扩散原位反应法制备了Zr/Hf-ZrC_(1-x)/HfC_(1-x)棒,研究了不同的碳化温度和碳源对棒材微观结构和烧蚀行为的影响。研究结果表明,由于HfC和ZrC的无限固溶,在Zr-Hf合金棒中形成了一种双层结构,外层为ZrC/HfC层,内层为含有ZrC_(1-x)/HfC_(1-x)颗粒的Zr/Hf-ZrC_(1-x)/HfC_(1-x)混合层。随着碳化温度的升高,陶瓷层逐渐增厚。当C/C-ZrC-SiC作为碳源时,陶瓷层的厚度明显高于石墨作为碳源时的厚度。烧蚀后,在棒材表面形成一层熔融的ZrO_(2)-HfO_(2)外层,这一氧化层起着对基体表面进行氧化物补偿的作用,在棒材内部形成一层具有低氧透过率的ZrC_(x)O_(y)/HfC_(x)O_(y)层。同时,ZrO_(2)、HfO_(2)及其固溶体颗粒被烧结致密化,从而降低了氧化层的透氧性,并增强了该氧化层的抗烧蚀性。

关键词：碳扩散陶瓷层原位反应耐烧蚀

Deployment analysis of composite thin-walled lenticular tubes with effect of storage time and temperature

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Chinese Journal of Aeronautics 2024年第1期37卷 162-172页

作者： Jinfeng DENG Ning AN Qilong JIA Xiaofei MA School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China State key laboratory for strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China State key laboratory of structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China Xi’an Institute of Space Radio Technology Xi’an 710100China

Composite Thin-walled Lenticular Tube(CTLT)is increasingly utilized in small satellites missions as a lightweight,foldable,and rollable structural material that facilitates the construction of large deployable systems.The CTLT is initially flattened and coiled around a central hub for storage before launch,during which elastic energy is stored as deformation energy,allowing it to be self-deployed on demand for use in orbit.This work presents a comprehensive investigation into the coiling,storage and deployment behaviors of CTLT that wraps around a central hub.A nonlinear explicit dynamic finite element model was developed with both deformable CTLT and rigidbodies mechanisms including the central hub and guide rollers,as well as the complex interactions among them.The coiling mechanics characteristics such as stored strain energy and rotational moment were presented and validated against experimental data in the literature.Then,the dynamic deployment behaviors were analyzed in terms of two different deployment methods,namely,controlled deployment and free deployment.The effect of material property change during storage was also discussed through numerical experiments.

关键词： Composite deployable structures Deployment dynamics Finite element method Stress relaxation Thin-walled booms

Numerical Simulation of Radial Ultrasonic Assisted MIG Welding Arc

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Journal of Shanghai Jiaotong university(Science) 2024年第2期29卷 330-338页

作者：洪蕾肖皓叶佳马国红 key laboratory of Lightweight and High strength structural Materials of Jiangxi Province School of Mechanical EngineeringNanchang UniversityNanchang 330031China Applied Materials Inc.Santa ClaraCA 95054-3299USA

The numerical simulation of arc was carried out for both conventional melt inert gas(MIG)welding and ultrasonic assisted melt inert gas(U-MIG)welding.Based on the model established by Fluent,the arc shape,temperature field,and potential distribution were simulated.The study found that the shape of the arc changed when ultrasonic was added radially;the high-temperature area of the arc stretched,and the temperature peak increased.But as the current increased,the increase in temperature decreased.In addition,under the same conditions,the potential of U-MIG decreased and the pressure on the workpiece increased.To verify the accuracy of the simulation results,welding experiments under identical conditions were carried out,and a high-speed camera was used to collect dynamic pictures of the arc.The simulation results were in a favorable agreement with the experimental results,which provided a certain reference value for ultrasonic assisted arc welding.

关键词： numerical simulation welding arc ultrasonic arc welding arc temperature

The chemical environment and structural ordering in liquid Mg-Y-Zn system:An ab-initio molecular dynamics investigation of melt for the formation mechanism of LPSO structure

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Journal of Magnesium and Alloys 2024年第2期12卷 815-824页

作者： Tangpeng Ma Jin Wang Kaiming Cheng Chengwei Zhan Jixue Zhou Jingyu Qin Guochen Zhao Xinfang Zhang Shandong Provincial key laboratory of High strength Lightweight Metallic Materials Advanced Materials InstituteQilu University of Technology(Shandong Academy of Sciences)Jinan 250014China key laboratory for Liquid-Solid structural Evolution and Processing of Materials Ministry of EducationShandong UniversityJinan 250061China School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China

In an effort to clarify the formation mechanism of LPSO structure in Mg-Y-Zn alloy,the chemical environment and structural ordering in liquid Mg-rich Mg-Y-Zn system are investigated with the aid of ab-initio molecular dynamics simulation.In liquid Mg-rich Mg-Y alloys,the strong Mg-Y interaction is determined,which promotes the formation of fivefold symmetric local structure.For Mg-Zn alloys,the weak Mg-Zn interaction results in the fivefold symmetry weakening in the liquid structure.Due to the coexistence of Y and Zn,the strong attractive interaction is introduced in liquid Mg-Y-Zn ternary alloy,and contributes to the clustering of Mg,Y,Zn launched from Zn.What is more,the distribution of local structures becomes closer to that in pure Mg compared with that in binary Mg-Y and Mg-Zn alloys.These results should relate to the origins of the Y/Zn segregation zone and close-packed stacking mode in LPSO structure,which provides a new insight into the formation mechanism of LPSO structure at atomic level.

关键词： Mg-Y-Zn Chemical environment structural ordering ab-initio molecular dynamics

Strain engineering in electrocatalysis:Strategies,characterization,and insights

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Nano Research 2024年第5期17卷 3603-3621页

作者： Qibo Deng Peng Xu Hassanien Gomaa Mohamed A.Shenashen Sherif A.El-Safty Cuihua An Li-Hua Shao Ning Hu School of Mechanical Engineering Hebei University of TechnologyTianjin 300401China Department of Chemistry Faculty of ScienceAl-Azhar University71524AssiutEgypt Department of Petrochemical Egyptian Petroleum Research Institute(EPRI)Nasr City11727CairoEgypt Center for Functional Materials National Institute for Materials Science(NIMS)1-2-1 SengenTsukubaIbaraki-ken305-0047Japan State key laboratory of Reliability and Intelligence Electrical Equipment Key Laboratory of Advanced Intelligent Protective Equipment TechnologyMinistry of Educationand School of Mechanical EngineeringHebei University of TechnologyTianjin 300401China national key laboratory of strength and structural integrity Institute of Solid MechanicsSchool of Aeronautic Science and EngineeringBeihang UniversityBeijing100191China Advanced Equipment Research Institute Co. Ltd.of HEBUTTianjin 300401China

Strain engineering,as a cutting-edge method for modulating the electronic structure of catalysts,plays a crucial role in regulating the interaction between the catalytic surface and the adsorbed molecules.The electrocatalytic performance is influenced by the electronic structure,which can be achieved by introducing the external forces or stresses to adjust interatomic spacing between surface atoms.The challenges in strain engineering research lie in accurately understanding the mechanical impact of strain on performance.This paper first introduces the basic strategy for generating the strain,summarizes the different strain generation forms and their advantages and disadvantages.The progress in researching the characterization means for the lattice strains and their applications in the field of electrocatalysis is also emphasized.Finally,the challenges of strain engineering are introduced,and an outlook on the future research directions is provided.

关键词： strain electrocatalysis characterization chemical reaction kinetics lattice mismatch

预制体结构对SiC_(f)/SiC复合材料力学和热性能的影响

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Journal of Central South University 2024年第1期31卷 101-113页

作者：王徐辉吴宗绪陈招科伍艳熊翔 Science and Technology on High strength structural Materials laboratory Central South UniversityChangsha 410083China State key laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

本文采用化学气相渗透法制备了具有二维多层、三维角联锁机织和多轴三维编织三种预制体结构的SiC_(f)/SiC复合材料。在综合分析纤维排列、SiC基体和孔隙分布的基础上,详细讨论了预制体结构对SiC_(f)/SiC复合材料力学性能和热性能的影响... 详细信息

本文采用化学气相渗透法制备了具有二维多层、三维角联锁机织和多轴三维编织三种预制体结构的SiC_(f)/SiC复合材料。在综合分析纤维排列、SiC基体和孔隙分布的基础上,详细讨论了预制体结构对SiC_(f)/SiC复合材料力学性能和热性能的影响。结果表明,复合材料的力学性能和热导率受纤维排列方式和复合材料密度的综合影响,而热膨胀系数主要受纤维排列方式的影响。此外,二维多层复合材料、三维角联锁机织复合材料和多轴三维编织复合材料的热导率可以分别用串联模型和平行模型来解释。多轴三维编织复合材料由于内部具有连续的可以作为热流快速通道的三维网状SiC基体层,因此具有较高的室温热导率。而随着温度的升高,SiC声子间的散射逐渐增强,SiC基体层在多轴三维编织复合材料中作为声子传播快速通道的作用逐渐减弱,热导率随温度降低的趋势更明显。

关键词：预制体结构抗弯强度热导率热膨胀系数 SiC_(f)/SiC复合材料

Robust, breathable, and chemical-resistant polytetrafluoroethylene (PTFE) films achieved by novel in-situ fibrillation strategy for highperformance triboelectric nanogenerators

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Nano Research 2024年第3期17卷 1942-1951页

作者： Jialong Chai Guilong Wang Jinchuan Zhao Guizhen Wang Chao Wei Aimin Zhang Guoqun Zhao laboratory for Liquid-Solid structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China key laboratory of Chinese Education Ministry for Tropical Biological Resources Hainan UniversityHaikou 570228China

In the era of advanced wearable electronic devices,the triboelectric nanogenerators(TENGs)as energy harvesting and self-powered sensing units hold great promise.Selecting appropriate triboelectric material is the crucial factor to optimize the performance of TENG,while polytetrafluoroethylene(PTFE)stands out as a highly versatile option among the various materials.In this study,we present an ultrafine nanofibrous PTFE(NF-PTFE)films prepared by novel in-situ fibrillation strategy as the triboelectric material in TENG devices.The innovative processing methodology facilely addresses the dilemma between high porosity and fine pore size of traditional porous PTFE films,meanwhile achieves exceptional mechanical strength,hydrophobicity,air permeability,and chemical resistance of the films.With the integration of nanofibrous PTFE films into contact-separation mode TENG and droplet-based TENG,these devices realize the peak electrical output of 131 V/10.8μA and 54 V/14μA with great durability,which surpass the performance of TENGs using traditional expanded PTFE films.Furthermore,a smart glove capable of recognizing hand gestures is proposed,which demonstrates the versatility,flexibility,and practicality of this material for potential use in smart devices.This reported NF-PTFE film provides insights for the design of high-performance TENG device for advanced wearable electrical applications.

关键词： polytetrafluoroethylene(PTFE) nanofibrous film hydrophobic triboelectric nanogenerator self-powered sensor