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Developing high-Q × f value MgNb_(2–x)Ta_(x)O_(6)(0≤x≤0.8) columbite ceramics and clarifying the impact mechanism of dielectric loss: Crystal structure, Raman vibrations, microstructure, lattice defects, chemical bond characteristics, structural parameters, and microwave dielectric properties in-depth studies

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Journal of Materials Science & Technology 2023年第15期146卷 186-199页

作者： lingxia li yuting li Jianli Qiao Mingkun Du School of Microelectronics Tianjin UniversityTianjin300072China Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin UniversityTianjin300072China Tianjin Key Laboratory of Imaging and Sensing Microelectronic Technology Tianjin UniversityTianjin300072China

With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid attenuation of high-frequency signals during *** order to improve the Q×f of the MgNb2O6 system and study the internal mechanism between the structure and microwave dielectric properties,Ta5+ion is introduced to design and fabricate MgNb_(2-x)Ta_(x)O_(6)(0≤x≤0.8)ceramics by the solid-state reaction *** single columbite phase and dense structure are observed throughout the entire composition *** elements(Mg,Nb,Ta,and O)can be detected by X-ray photoelectron *** from the Raman spectroscopy and group theoretical analysis reveal that the Ag(2)and Ag(3)modes located at∼905 cm−1 dominate the Raman *** addition,theɛr depends on the polarizability reflected by the C–M equation and Raman ***τf closely relates to the bond energy of the Nb/Ta–O bond and restoring force characterized by average octahedral distortion of[Nb/TaO6].Notably,the crucial factors for the huge improvement of Q×f are clarified deeply,in terms of the lower internal strain,the reduced ordering-induced domain size,and the chemical bond valence closer to the ionic valence state,which promotes the stability of crystal ***,the introduction of lower electronegative ions enhances the ability of electrons to compensate for oxygen vacancies,thereby reducing the dielectric loss caused by the *** microwave properties(ɛr=19.2,Q×f=170,000 GHz,andτf=−55.6 ppm℃–1)are achieved in MgNb1.4Ta0.6O6 ceramic,specifically a nearly 40%increase in the Q×*** work has enriched the theory associated with low dielectric loss and provided the MgNb_(1.4)Ta_(0.6)O_(6) ceramic with a pretty high-Q×f for the application in the design of the 5G/6G wireless communication devices.

关键词： Advances in 5G/6G materials High-Q×f value ceramic Group theoretical analysis Oxygen vacancy Chemical bond characteristics Microwave dielectric properties

Implications of Stahl's Theorems to Holomorphic Embedding Part II: Numerical Convergence

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CSEE Journal of Power and Energy Systems 2021年第4期7卷 773-784页

作者： Abhinav Dronamraju Songyan li Qirui li yuting li Daniel Tylavsky Di Shi Zhiwei Wang School of Electrical Computer and Energy Engineering in Arizona State University TempeAZ 85287USA Southwest Electric Power Design Institute Co. Ltd.of China Siemens 8850 Fallbrook Dr.HoustonTexas 77064United States AINERGY LLC Santa ClaraCA 95051 State Grid Jiangsu Electric Power Company Nanjing 210024China

What has become known as Stahl's Theorem in power-engineering circles has been used to justify a convergence guarantee of the Holomorphic Embedding Method(HEM)as it applies to the power-flow *** this,the second part of a two-part paper,we examine implications to numerical convergence of the HEM and the numerical properties of a Pade approximant *** show that even if the point of interest is within the convergence domain,numerical convergence of the sequence of Pade approximants computed with finite precision is not *** propose a convergence factor equation that can be used to both estimate the convergence rate and the capacity of the branch *** also show that the study of convergence properties of the Pade approximant is the study of the location of the branch-points of the function,which in turn dictate branch-cut topology and capacity and,therefore,convergence rate.

关键词： Analytic continuation HEM holomorphic embedding method power flow Pade approximants StahPs theorems

Computational screening of transition metal-doped CdS for photocatalytic hydrogen production

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npj Computational Materials 2022年第1期8卷 2190-2198页

作者： yuting li Daniel Bahamon Mutasem Sinnokrot Lourdes F.Vega Research and Innovation Center on CO_(2) and Hydrogen(RICH) Khalifa UniversityPO Box 127788Abu DhabiUAE Chemical Engineering Department.Khalifa University PO Box 127788Abu DhabiUAE Chemistry Department Khalifa UniversityPO Box 127788Abu DhabiUAE

A novel computational screening study of single transition metal(TM),TM-doped,and dual TMs-doped on CdS(110)surfaces via DFT calculations is presented,focusing on their stability and catalytic activity,searching for efficient photocatalysts for hydrogen *** based on key performance descriptors allowed to fine-tune the *** indicate that TM dopants can reduce the energy band gap and enhance impurity ***,Rh,and Pd were found to be the best dopants in TM-doped CdS,since their|ΔG_(H)|is 80%smaller compared to the pristine CdS ***,TM1-TM2-co-doped CdS catalysts show better performance for the hydrogen evolution reaction(HER)due to synergistic effects of the two TMs,where Co-Pt,Pd-Pt and Co-Rh co-doping CdS significantly reduced|ΔGH|to less than 0.1 *** point out four promising novel co-catalysts(i.e.,Co,Co-Pt,Co-Rh,Rh-Ag)with very good performance in HER,to be further explored in experimental studies.

关键词： surface transition allowed

Insights into the tribological behavior of choline chloride-urea and choline chloride-thiourea deep eutectic solvents

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Friction 2023年第1期11卷 76-92页

作者： yuting li Yuan li Hao li Xiaoqiang FAN Han YAN Meng CAI Xiaojun XU Minhao ZHU Key Laboratory of Advanced Technologies of Materials(Ministry of Education) School of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China Tribology Research Institute School of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Deep eutectic solvents(DESs)have been considered as novel and economic alternatives to traditional lubricants because of their similar physicochemical *** this study,choline chloride(ChCl)DESs were successfully synthesized via hydrogen-bonding networks of urea and thiourea as the hydrogen bond donors(HBDs).The as-synthesized ChCl-urea and ChCl-thiourea DESs had excellent thermal stability and displayed good lubrication between steel/steel *** friction coefficient and wear rate of ChCl-thiourea DES were 50.1%and 80.6%,respectively,lower than those of ChCl-urea DES for GCr15/45 steel ***,for GCr15/Q45 steel,ChCl-urea DES decreased the wear rate by 85.0%in comparison to ChCl-thiourea *** ChCl-thiourea DES lubrication,the tribo-chemical reaction film composed of FeS formed at the interfaces and contributed to low friction and ***,under high von Mises stress,the film could not be stably retained and serious wear was obtained through direct contact of friction *** illustrated that the evolution of the tribo-chemical reaction film was responsible for the anti-friction and anti-wearproperties of the DESs.

关键词： deep eutectic solvents(DESs) tribo-chemical film von Mises stress lubrication mechanism

FeCo alloy/N,S co-doped carbon aerogel derived from directionalcasting cellulose nanofibers for rechargeable liquid flow and flexible Zn–air batteries

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Nano Research 2023年第5期16卷 6870-6880页

作者： Yiwen Zhang Xifeng Zhang yuting li Juan Wang Sibudjing Kawi Qin Zhong School of Chemistry and Chemical Engineering Nanjing University of Science and TechnologyNanjing 210094China Department of Chemical and Biomolecular Engineering National University of SingaporeSingapore 117582Singapore

Bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalysts with the advantages of excellent activity and stability are the vital components of air cathodes for rechargeable Zn–air batteries(ZABs).Herein,the carbon aerogel with honeycomb-like structure,N and S double doping and loaded with FeCo alloy nanoparticles(NSCA/FeCo)was prepared successfully as cathodes for rechargeable liquid flow and two-dimensional flexible ZABs by clever directional *** interaction between the bimetallic alloy and the double-doped carbon with specifical structure,large surface,great conductivity endows NSCA/FeCo with effective ORR/OER active sites and small charge/mass transport barrier,thus achieving outstanding bifunctional catalytic *** NSCA/FeCo displays a half-wave potential of+0.85 V(*** hydrogen electrode(RHE))for ORR and an overpotential of 335 mV at a current density of 10 mA·cm^(−2)for OER,which is even comparable to the performance of noble-metal catalysts in relevant fields(Pt/C for ORR and RuO_(2)for OER).Consequently,the rechargeable liquid flow ZABs assembled with NSCA/FeCo showed excellent performance(maximum power density:132.0 mW·cm^(−2),specific capacity:804.5 Wh·kg^(−1)at 10 mA·cm^(−2),charge and discharge cycle stability of more than 250 cycles).Furthermore,the flexible NSCA/FeCo-based ZABs have a maximum power density of 43.0 mW·cm^(−2),outstanding charging–discharge stability of more than 450 cycles,exhibit good flexibility under different bending ***,this work has provided an efficient bifunctional electrocatalyst for OER/ORR and a promising strategy of air cathodes for rechargeable and wearable ZABs.

关键词： carbon aerogel bifunctional electrocatalyst FeCo alloy directional freeze-casting rechargeable zinc–air batteries flexible batteries

Hierarchical Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures:A first principles calculation and application in corrosion/wear protection

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Journal of Materials Science & Technology 2022年第21期116卷 151-160页

作者： Meng Cai Peng Feng Han Yan yuting li Shijie Song Wen li Hao li Xiaoqiang Fan Minhao Zhu Tribology Research Institute School of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu 610031China Key Laboratory of Advanced Technologies of Materials(Ministry of Education) School of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Surface and interface engineering plays a crucial role in modulating the properties of materials,especially two-dimensional(2D)***,a strategy,forming heterostructures with MoS_(2),is proposed to overcome the natural agglomeration of Ti_(3)C_(2)T_(x) MXene *** importantly,the interactions between Ti_(3)C_(2)Tx and MoS_(2) were elaborately investigated by first-principles calculations based on density functional theory(DFT)for the first *** calculations demonstrate that van der Waals forces dominate the interface interactions of Ti_(3)C_(2)T_(x) and MoS_(2),rendering Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures favorable *** Ti_(3)C_(2)T_(x)@MoS_(2) heterostructure composites were synthesized through a facile one-step hydrothermal method and exhibit a 2D hierarchical ***,the corrosion and tribological properties of epoxy composite coatings with varying proportions of Ti_(3)C_(2)T_(x)@MoS_(2) composites were studied in *** a result,the epoxy composite coating with 0.1 wt.%Ti_(3)C_(2)T_(x)@MoS_(2) composites(Ti_(3)C_(2)T_(x)@MoS_(2)-0.1)exhibits excellent corrosion protection and antiwear *** Ti_(3)C_(2)T_(x)@MoS_(2)-0.1 keeps the largest low-frequency impedance modulus(|Z|_(0.)01 Hz)and coating resistance(R_(c))during the whole immersion *** wear rate is 0.09μm^(3)/(Nμm)under the load of 10 N,one half of that of pure epoxy coating(EP).This work further broadens the application of MXene-based heterostructure composites.

关键词： First-principles calculations Ti_(3)C_(2)T_(x)MXene MoS_(2) Heterostructure Corrosion/wear

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Stochastic Responses and Bifurcations of Shape Memory Alloy Beam under Asymmetric Impacting Constraint

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Journal of Mathematical Research with Applications 2022年第5期42卷 539-550页

作者： yuting li Jinqian FENG College of Mathematics Jilin University College of Science Xi'an Polytechnic University

Shape Memory Alloy(SMA) is a new type of smart material with shape memory effect in the 21st century. In this work, the vibro-impact(VI) system is constructed for an SMA beam with asymmetric constraint. In two cases of non-impacting and impacting for Hamiltonian function, the approximate analytical results are presented by taking advantage of the stochastic averaging method. Numerical simulation emerges as the tool that verifies the obtained analytical results. In particular, the discussed results reveal that the probability response curve of the system energy demonstrates non-smooth characteristics. Moreover, the stochastic P-bifurcation and D-bifurcation can occur when the constraint position changes.

关键词： shape memory alloy stochastic averaging probability density function stochastic P-bifurcation stochastic D-bifurcation

Probability Response of Shape Memory Alloy Beam Subjected to Noise Excitation

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Journal of Harbin Institute of Technology(New Series) 2020年第1期27卷 85-90页

作者： yuting li Jinqian Feng Yingxiao Wang School of Science Xi’an Polytechnic University

Shape Memory Alloy(SMA)is a typical material with memory effect,and it is widely used in many engineering *** on the elastic theory and Galerkin method,a vibration system of SMA beam with rigid constraints is *** non⁃smooth transformation was employed to deal with the discontinuous position,and the original system was turned into an approximate equivalent system associated with the Dirac ***,using the stochastic averaging method,the drift and diffusion coefficients of the corresponding Fokker Planck Kolmogorov equation were ***,the approximate probability response of the system was formulated ***,numerical simulation was carried out to verify the effectiveness of analytical ***,stochastic bifurcation was *** show that the stationary probability response of the system was affected by the increase of noise amplitude and restitution force,and a certain restitution value and damping could induce P⁃bifurcation.

关键词： Shape Memory Alloy stochastic averaging stationary probability density stochastic bifurcation

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Well-Dispersed Graphene Enhanced lithium Complex Grease Toward High-Efcient Lubrication

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Chinese Journal of Mechanical Engineering 2023年第5期36卷 341-352页

作者： Kaiyue lin Zhuang Zhao yuting li Zihan Zeng Xiaofeng Wei Xiaoqiang Fan Minhao Zhu Key Laboratory of Advanced Technologies of Materials(Ministry of Education) School of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China Tribology Research Institute School of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the infuence of graphene dispersion on the thickening efect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modifed graphene ([P_(66614)][DEHP]-G). Then lithium complex grease was prepared by saponifcation with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefn (PAO20) as base oil and the modifed-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modifed-graphene lithium complex grease ofered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefcient and wear volume up to 18.84% and 67.34%, respectively. With base oil overfow and afux, well-dispersed [P_(66614)][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition flm. The synergy of deposited graphene-flm, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.

关键词： Graphene additive lithium complex grease Dispersion Tribological properties

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