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Seynergistic effect of Mo and Zr additions on microstructure and mechanical properties of Nb-Ti-Si-based alloys additively manufactured by laser directed energy deposition

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Journal of Materials Science & Technology 2022年第8期103卷 84-97页

作者： Yunlong Li Xin lin yunlong Hu Jun Yu Junguo Zhao Hongbiao Dong Weidong Huang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design MIIT ChinaNorthwestern Polytechnical UniversityXi’an 710072China School of Engineering University of LeicesterLE17RHUK

The synergistic effect of Mo and Zr additions on microstructure evolution,room-temperature fracture toughness and microhardness of Nb-22Ti-15Si-xMo-yZr(x=4,8,y=3,6)alloys manufactured by laser directed energy deposited(L-DED)have been investigated.The major phases in as-deposited 4Mo-3Zr alloy are Nb solid solution(Nbss),Nb_(3)Si andγ-Nb_(5)Si_(3).The Nb_(3)Si phases disappear with increasing Mo content to 8 at.%or increasing Zr content to 6%.γ-Nb_(5)Si_(3) precipitates formed in the Nbss of as-deposited xMo-yZr alloys due to the cyclic re-heating,and theγ-Nb_(5)Si_(3) precipitates and Nbss matrix exhibits orientation relationship(OR)of[001]Nbss//[1112]γand(110)Nbss//(0110)γin as-deposited 4Mo-6Zr alloy.The microstructure of xMo-yZr alloys became relative homogeneity and the Nbss matrix showed the better continuity after the heat treatment(1400°C/30 h).The Nb_(3)Si phase has transformed into Nbss andαNb_(5)Si_(3) with the OR have been determined as{100}Nbss//{100}αand{111}Nbss//{111}αin the heat-treated 4Mo-3Zr alloy.When Mo content increase to 8at.%,a part ofγ-Nb_(5)Si_(3) phase also transformed into theα-Nb_(5)Si_(3) phase with the OR have been determined as{1120}γ//{110}αand{1010}γ//{111}αafter heat treatment.Among the as-deposited alloys,the 4Mo-6Zr alloy has the highest fracture toughness KQ with the lowest hardness.The average KQ of 4Mo-6Zr and 8Mo-6Zr alloys increased by 28%and 30%after the heat treatment,and reached 13.61 and 11.43 MPa·m^(1/2),respectively.The hardness of Nb-22Ti-15Si-xMoyZr alloys is significantly decreased after the heat treatment.

关键词： alloys microstructure toughness

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Research of influence of reduced-order boundary on accuracy and solution of interior points

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Applied Mathematics and Mechanics(English Edition) 2017年第1期38卷 111-124页

作者： Yunlong Li Wei CAO Department of Mechanics Tianjin UniversityTianjin 300072China

The flow field with a high order scheme is usually calculated so as to solve complex flow problems and describe the flow structure accurately. However, there are two problems, i.e., the reduced-order boundary is inevitable and the order of the scheme at the discontinuous shock wave contained in the flow field as the supersonic flow field is low. It is questionable whether the reduced-order boundary and the low-order scheme at the shock wave have an effect on the numerical solution and accuracy of the flow field inside. In this paper, according to the actual situation of the direct numerical simulation of the flow field, two model equations with the exact solutions are solved, which are steady and unsteady, respectively, to study the question with a high order scheme at the interior of the domain and the reduced-order method at the boundary and center of the domain. Comparing with the exact solutions, it is found that the effect of reduced-order exists and cannot be ignored. In addition, the other two model equations with the exact solutions, which are often used in fluid mechanics, are also studied with the same process for the reduced-order problem.

关键词： reduced-order boundary shock wave accuracy numerical solution high order scheme

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Dynamic Characteristics of Rotor System with a Slant Crack Based on Fractional Damping

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Chinese Journal of Mechanical Engineering 2021年第2期34卷 79-96页

作者： Zhinong li Yunlong Li Dong Wang Zhike Peng Haifeng Wang Key Laboratory of Nondestructive Testing Ministry of EducationNanchang Hangkong UniversityNanchang 330063China Laboratory of Science and Technology on Integrated Logistics Support National University of Defense TechnologyChangsha 410073China State Key Laboratory of Mechanical Systems and Vibration Shanghai Jiaotong UniversityShanghai 200240China

The traditional modeling method of rotor system with a slant crack considers only integer-order calculus.However,the model of rotor system based on integer-order calculus can merely describe local characteristics,not historical dependent process.The occur of fractional order calculus just makes up for the deficiency in integer-order calculus.Therefore,a new dynamic model with a slant crack based on fractional damping is proposed.Here,the stiffness of rotor system with a slant crack is solved by zero stress intensity factor method.The proposed model is simulated by Runge-Kutta method and continued fraction Euler method.The influence of the fractional order,rotating speed,and crack depth on the dynamic characteristics of rotor system is discussed.The simulation results show that the amplitude of torsional excitation frequency increases significantly with the increase of the fractional order.With the increase of the rotating speed,the amplitude of first harmonic component becomes gradually larger,the amplitude of the second harmonic becomes smaller,while the amplitude of the other frequency components is almost invariant.The shaft orbit changes gradually from an internal 8-type shape to an ellipse-type shape without overlapping.With the increase of the slant crack depth,the amplitude of the transverse response frequency in the rotor system with a slant crack increases,and the amplitude in the second harmonic component also increases significantly.In addition,the torsional excitation frequency and other coupling frequency components also occur.The proposed model is further verified by the experiment.The valuable conclusion can provide an important guideline for the fault diagnosis of rotor system with a slant crack.

关键词： Fractional calculus Slant crack Rotor system Dynamic characteristics

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Molecular Dynamics Simulations of Thermal Properties of Polymer Composites Enhanced by Cross-linked Graphene Sheets

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Acta Mechanica Solida Sinica 2018年第6期31卷 673-682页

作者： Yunlong Li Shijie Wang Quan Wang School of Mechanical Engineering Shenyang University of TechnologyShenliao West Road No.111 Shenyang 110870China Department of Mechanics and Aerospace Engineering Southern University of Science and Technology Shenzhen 518055China

Molecular models of pristine, functionalized and cross-linked graphene sheet/polymer composites are developed. Temperature cooling processes are conducted to examine the improve-ment of glass transition temperature of cross-linked graphene sheet/polymer composites using molecular dynamics simulations. The results show that increases of about 12.2% and 8.9% in the glass transition temperature of cross-linked graphene sheet/polymer composites are obtained, respectively, than those of the pristine and functionalized graphene sheet/polymer composites. In order to reveal the enhanced thermal properties from atomic views, the interfacial interaction energy and radius distribution function between the graphene sheets and the polymer matrix, the mean square displacement variations and the free volume of polymer composites are examined and discussed.

关键词： Molecular dynamics simulation Polymer composites Graphene sheet Glass tran-sition temperature

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Perspective on perovskite materials as X-ray detectors

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Science China(Technological Sciences) 2022年第1期65卷 244-246页

作者： CHEN HuiWen li yunlong XUE DongFeng Multiscale Crystal Materials Research Center Shenzhen Institute of Advanced TechnologyChinese Academy of SciencesShenzhen 518055China

X-ray imaging plays an important role in medical applications[1].Two available strategies are currently employed for X-ray detection,direct conversion and indirect conversion method(Figure 1).In the direct method,X-ra... 详细信息

关键词： Figure perovskite converted

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Radar Sensing via OTFS Signaling

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中国通信:英文版 2023年第9期20卷 34-45页

作者： Kecheng Zhang Zhongjie li Weijie Yuan yunlong Cai Feifei Gao Department of Electronic and Electrical Engineering Southern University of Science and TechnologyShenzhen 518055China College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Department of Automation Tsinghua UniversityBeijing 100084China

By multiplexing information symbols in the delay-Doppler(DD)domain,orthogonal time frequency space(OTFS)is a promising candidate for future wireless communication in high-mobility scenarios.In addition to the superior communication performance,OTFS is also a natural choice for radar sensing since the primary parameters(range and velocity of targets)in radar signal processing can be inferred directly from the delay and Doppler shifts.Though there are several works on OTFS radar sensing,most of them consider the integer parameter estimation only,while the delay and Doppler shifts are usually fractional in the real world.In this paper,we propose a two-step method to estimate the fractional delay and Doppler shifts.We first perform the two-dimensional(2D)correlation between the received and transmitted DD domain symbols to obtain the integer parts of the parameters.Then a difference-based method is implemented to estimate the fractional parts of delay and Doppler indices.Meanwhile,we implement a target detection method based on a generalized likelihood ratio test since the number of potential targets in the sensing scenario is usually unknown.The simulation results show that the proposed method can obtain the delay and Doppler shifts accurately and get the number of sensing targets with a high detection probability.

关键词： OTFS radar sensing delay-Doppler(DD)domain fractional delay and Doppler

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Towards Practical Application of li-S Battery with High Sulfur Loading and Lean Electrolyte:Will Carbon-Based Hosts Win This Race?

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Nano-Micro Letters 2023年第9期15卷 384-422页

作者： Yi Gong Jing li Kai Yang Shaoyin li Ming Xu Guangpeng Zhang Yan Shi Qiong Cai Huanxin li yunlong Zhao Advanced Technology Institute University of SurreyGuildfordSurrey GU27XHUK Department of Chemical and Process Engineering University of SurreyGuildford GU27XHUK Department of Chemistry Physical and Theoretical Chemistry LaboratoryUniversity of OxfordOxford OX13QZUK Department of Engineering University of Cambridge9 JJ Thomson AvenueCambridge CB30FAUK State Key Laboratory for Chemo/Biosensing and Chemometrics College of Chemistry and Chemical EngineeringHunan UniversityChangsha 410082HunanPeople’s Republic of China College of Materials and Metallurgy Guizhou UniversityGuiyang 550025People’s Republic of China

As the need for high-energy–density batteries continues to grow, lithium-sulfur(li–S) batteries have become a highly promising next-generation energy solution due to their low cost and exceptional energy density compared to commercially available li-ion batteries. Research into carbon-based sulfur hosts for li–S batteries has been ongoing for over two decades, leading to a significant number of publications and patents.However, the commercialization of li–S batteries has yet to be realized. This can be attributed, in part, to the instability of the li metal anode. However, even when considering just the cathode side, there is still no consensus on whether carbon-based hosts will prove to be the best sulfur hosts for the industrialization of li–S batteries. Recently, there has been controversy surrounding the use of carbon-based materials as the ideal sulfur hosts for practical applications of li–S batteries under high sulfur loading and lean electrolyte conditions. To address this question, it is important to review the results of research into carbon-based hosts, assess their strengths and weaknesses, and provide a clear perspective. This review systematically evaluates the merits and mechanisms of various strategies for developing carbon-based host materials for high sulfur loading and lean electrolyte conditions. The review covers structural design and functional optimization strategies in detail, providing a comprehensive understanding of the development of sulfur hosts. The review also describes the use of efficient machine learning methods for investigating li–S batteries. Finally, the outlook section lists and discusses current trends, challenges, and uncertainties surrounding carbon-based hosts, and concludes by presenting our standpoint and perspective on the subject.

关键词： li-S batteries Carbon materials Structural design Functional modification Machine learning

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Mechanical reliable,NIR light-induced rapid self-healing hydrogel electrolyte towards flexible zinc-ion hybrid supercapacitors with low-temperature adaptability and long service life

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Journal of Energy Chemistry 2024年第5期92卷 63-73页

作者： Tengjia Gao Na li Yang Yang Jing li Peng Ji yunlong Zhou Jianxiong Xu School of Materials and Advanced Manufacturing Hunan Key Laboratory of Electrochemical Green Metallurgy TechnologyHunan University of TechnologyZhuzhou 412007HunanChina School of life Sciences and Chemistry Hunan Key Laboratory of Biomedical Nanomaterials and DevicesHunan University of TechnologyZhuzhou 412007HunanChina

Hydrogel electrolytes hold great potential in flexible zinc ion supercapacitors(ZICs)due to their high conductivity,good safety,and flexibility.However,freezing of electrolytes at low temperature(subzero)leads to drastic reduction in ionic conductivity and mechanical properties that deteriorates the performance of flexible ZICs.Besides,the mechanical fracture during arbitrary deformations significantly prunes out the lifespan of the flexible device.Herein,a Zn^(2+)and li^(+)co-doped,polypyrrole-dopamine decorated Sb_(2)S_(3)incorporated,and polyvinyl alcohol/poly(N-(2-hydroxyethyl)acrylamide)double-network hydrogel electrolyte is constructed with favorable mechanical reliability,anti-freezing,and self-healing ability.In addition,it delivers ultra-high ionic conductivity of 8.6 and 3.7 S m^(-1)at 20 and−30°C,respectively,and displays excellent mechanical properties to withstand tensile stress of 1.85 MPa with tensile elongation of 760%,together with fracture energy of 5.14 MJ m^(-3).Notably,the fractured hydrogel electrolyte can recover itself after only 90 s of infrared illumination,while regaining 83%of its tensile strain and almost 100%of its ionic conductivity during−30–60°C.Moreover,ZICs coupled with this hydrogel electrolyte not only show a wide voltage window(up to 2 V),but also provide high energy density of 230 Wh kg^(-1)at power density of 500 W kg^(-1)with a capacity retention of 86.7%after 20,000 cycles under 20°C.Furthermore,the ZICs are able to retain excellent capacity even under various mechanical deformation at−30°C.This contribution will open up new insights into design of advanced wearable flexible electronics with environmental adaptability and long-life span.

关键词： Flexible zinc ion supercapacitor Hydrogel electrolyte Self-healing Anti-freezing

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Enhanced Removal of Phenols by MIZ-Cu Nanozyme Exhibiting Laccase-like Activity and Broader Adaptability to Temperature and pH Conditions

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Chemical Research in Chinese Universities 2023年第6期39卷 1111-1118页

作者： WANG yunlong SUN Yue WANG Le ZHANG Hao HU Jiakang li Yongxin Key Lab of Groundwater Resources and Environment of Ministry of Education Key Lab of Water Resources and Aquatic Environment of Jilin ProvinceCollege of New Energy and EnvironmentJilin UniversityChangchun 130021P.R.China

Phenolic compounds,classified as persistent organic pollutants,pose a significant threat to both human health and environmental safety.Therefore,the efficient removal of phenolic substances from water is of paramount importance.Laccase,a multicopper oxidase,is commonly utilized for the efficient removal of phenolic contaminants from water due to its highly effective catalytic activity towards phenolic compounds.However,natural laccase exhibits certain limitations that impede its practical implementation in industrial settings,including a restricted pH activity range,diminished enzymatic efficacy at elevated temperatures,and substantial cost implications.In this work,we prepared a nanozyme(MIZ-Cu,MIZ:2-methylimidazole)with laccase-like activity by coordinating 2-methylimidazole and copper.This nanozyme overcomes the deactivation issues observed in natural laccase under high temperature and alkaline conditions.The catalytic activity of the MIZ-Cu towards phenolic compounds surpasses that of natural laccase across a wide range of temperature and pH conditions.Under pH=9,80℃,and 500 mmol/L NaCl conditions,the removal rate of four phenols(catechol,hydroquinone,resorcinol,and phloroglucinol)by MIZ-Cu was much higher than that of natural laccase.The results also demonstrate exceptional removal rates in natural aquatic environments,thereby presenting a promising approach for the treatment of phenol-containing wastewater originating from industrial facilities.

关键词： Nanozyme Laccase Phenol Pollutant removal Wastewater treatment

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Monolithic polyimine vitrimer/graphene aerogel composites

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Chinese Chemical Letters 2023年第2期34卷 529-533页

作者： Jinye Zhang Shichang Luo yunlong Ma Ruiyang li Yinghua Jin li Qiu Wei Zhang Yunnan Key Laboratory for Micro/Nano Materials&Technology National Center for International Research on Photoelectric and Energy MaterialsSchool of Materials and EnergyYunnan UniversityKunming 650091China Department of Chemistry University of Colorado BoulderBoulderCO 80309United States

Graphene-polymer composites have attracted great attention as sensing materials due to their tailorable electrical conductivity, physicochemical properties, and sensitivity to geometric and functional changes.Herein, we report the first example of cylindrical monolithic polyimine vitrimer/graphene composites with excellent mechanical, compressive, rehealable and recyclable, and piezoresistive properties via simple infiltration of polymer monomers into the pores of graphene aerogel followed by thermal curing. The composites exhibit excellent durable compressibility(negligible reduction in the compression properties even after 3000 consecutive compression cycles), rapid recovery to the original size upon stress released,high compressive strength(up to 1.2 MPa), and high conductivity(up to 79 S/m). Excellent piezoresistive properties were observed, displaying consistent and reliable change of the electrical resistance with the compression ratio. Furthermore, rehealing with ~100% recovery of the compressive strength and electric conductivity was achieved under mild rehealing conditions, which is highly desired but has rarely been reported for electronic materials. The facile strategy for fabrication of rehealable monolithic polymer/GAs can open new possibilities for the sustainable development of composites with high electrical conductivity for various applications such as sensing, health monitoring, and movement detection.

关键词： Vitrimer Graphene aerogel Polyimine Rehealable Piezoresistive Monolithic

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