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Exotic surface magnetotransport phenomena in the antiferromagnetic Mott insulator NiS2

Physical Review materials 2023年第10期7卷 104401-104401页

作者： Sami El-Khatib Faisal Mustafa Mehmet Egilmez Bhaskar Das Yu Tao Moumita Maiti Yeon Lee Chris Leighton Department of Physics American University of Sharjah Sharjah PO Box 26666 United Arab Emirates Materials Science and Engineering Program American University of Sharjah Sharjah PO Box 26666 United Arab Emirates Department of Chemical Engineering and Materials Science University of Minnesota Minneapolis Minnesota 55455 USA

The pyrite-structure transition-metal disulfide NiS2 is in principle a model cubic antiferromagnetic Mott insulator that can be doped through insulator-metal transitions with both electrons and holes (in Ni1–xCuxS2 and Ni1–xCoxS2), eventually inducing superconductivity and ferromagnetism, respectively. Magnetism and transport have proven challenging to understand in NiS2, however. The antiferromagnetic spin structure below ∼39K is complex due to frustration, while unexplained weak ferromagnetism emerges below ∼30K. Surface conduction is also now understood to dominate in NiS2 at low temperatures, raising questions about the interpretation of decades of prior data. Here, we present a complete study of the surface magnetotransport phenomena that emerge at low temperatures in high-quality single-crystal NiS2, which turn out to be strikingly rich. On cooling, isotropic magnetoresistance due to a field-induced shift of the first-order weak ferromagnetic ordering transition is first uncovered, i.e., metamagnetic magnetoresistance. At lower temperatures, larger, anisotropic magnetoresistance effects arise due to distinct switching events associated with the weak ferromagnetism. Strong evidence is presented that this is due to a field-driven in-plane to out-of-plane reorientation of surface spins, likely correlated with surface steps and terraces. In-plane exchange bias accompanies these effects, further supporting this interpretation. At the lowest temperatures, the spin reorientation field eventually exceeds the 9-T measurement window, generating strongly field-asymmetric magnetoresistance. Some of these unusual phenomena also manifest in the Hall channel, culminating in a sizable anomalous Hall effect at low temperatures. These results significantly demystify recent magnetoresistance and magnetic microscopy observations in NiS2 crystals and nanoflakes, and constitute an important step in elucidating the complex electronic and magnetic properties of this pivotal antiferro

关键词： Electrical properties Electronic structure Magnetism Antiferromagnets Ferromagnets Mott insulators Magnetic techniques Transport techniques

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A study on structural characteristics and metallurgical mechanism of carbides for 440 martensitic stainless steel with different melt refining processes

Journal of Alloys and Metallurgical Systems

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Journal of Alloys and Metallurgical Systems 2023年 3卷

作者： Kuo, Yu-An Hung, Fei-Yi Zhao, Jun-Ren Wu, Bo-Ding Huang, Bo-Chin Chang, Kai-Chieh Chen, Kuan-Jen Ku, Chen-Wang Huang, Chih-Ying Hsieh, Ho-Yen Department of Materials Science and Engineering National Cheng Kung University Tainan Taiwan Department of Mechanical Engineering Southern Taiwan University of Science and Technology Tainan710 Taiwan Walsin Lihwa Corporation Tainan Taiwan

The melt refining process of Martensitic stainless steel smelting is closely related to the characteristics of the matrix;the formation mechanism and distribution of carbides, especially, influence the mechanical properties of steel. In this study, three different melt refining processes of 440 stainless steel were used for analysis: aluminum reduction process (440 M-Al), silicon reduction process (440 M-Si), and electro slag remelting (440 C-ESR). The results show the main carbides of 440 stainless steel after three different melt refining processes are M7C3 and M23C6. The carbides of 440 M-Al and 440 M-Si are fine particles;the carbide of 440 C-ESR is a small block. The 440 M-Al carbides are micron- and nanoscale-sized particles. The micron-sized carbides solidify and aggregate at the unit cell boundary, and the structure is Cr7C3. There are gaps between the carbide particles, and the solid solution carbon content of the adjacent matrix is high, which makes the hardness of the matrix greater than that of the carbide aggregation area. On the contrary, the matrix of 440 C-ESR solid dissolves many alloying elements, and the fine lump carbide is also Cr7C3. The carbide diffusion interface layer of 440 C-ESR can improve the bonding characteristics of the interface of the carbide and the matrix, thus enhancing the mechanical properties. © 2023 The Authors

关键词： Slags

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On the Mobility of Dislocations Intersecting Free Surfaces in Cu

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SSRN 2025年

作者： Duong, Ta Demkowicz, Michael J. Department of Materials Science and Engineering Texas A&M University College StationTX77843 United States Department of Mechanical and Aerospace Engineering University of Florida GainesvilleFL32611 United States

We perform atomistic simulations to study the motion of edge dislocations intersecting {112} free surfaces in Cu. For dislocations of length ≥11nm, intersections with the free surface exert a drag force that reduces mobility. This force increases with velocity and appears to diverge below the Rayleigh wave speed (CR). New dislocations emitted from the surface effectively prevent the intersections from exceeding CR. For line lengths below 11nm, dislocations additionally excite Lamb (bending) waves in the medium. Resonances with these waves generate new, subsonic branches in the stress-velocity relation, giving rise to intermittent fluctuations in dislocation velocity at constant imposed strain rate. These findings exhibit qualitative differences to the behavior of dislocations under periodic boundaries, suggesting that experiments measuring mobilities from the displacements of dislocation intersections with free surfaces are not fully representative of dislocations within crystal interiors, especially at near-sonic velocities and above. © 2025, The Authors. All rights reserved.

关键词： Rayleigh waves

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(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B:A novel high-entropy monoboride with good electromagnetic interference shielding performance in K-band

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Journal of materials science & Technology 2021年第18期77卷 58-65页

作者： Haiming Zhang Biao Zhao Fu-Zhi Dai Huimin Xiang Zhili Zhang Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyNo.1 South Dahongmen RoadBeijing100076China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou450046China

A novel equimolar high-entropy(HE)transition metal monoboride,(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B,was designed and prepared in powder and bulk form by high temperature elemental reaction method and spark plasma sintering(SPS)method,*** analysis shows that HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B possesses orthorhombic structure with Pnma space *** Rietveld refinement,the lattice parameters of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B are a=5.6675,b=2.9714,c=4.2209 and the theoretical density is 6.95 g/cm~*** Vickers hardness and electrical conductivity of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B bulk with relative density of 90%is 12.3±0.5 GPa and 0.49±0.04×10~6 S/m,*** to high electrical conductivity,HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B bulk with 3.0 mm thickness displays superior EMI shielding performance in 18.0–26.5 GHz(K-band),and the average values of SET,SER,and SEAare 23.3 dB,13.9 dB,and 9.4 dB,*** EMI shielding mechanism of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B mainly results from reflection.

关键词： High-entropy ceramics Transition metal monoboride Electromagnetic interference(EMI)shielding mechanical properties Electrical conductive ceramics

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Tuning the mechanical Properties of Ti6al4v Builds Produced by Direct-Write Additive Manufacturing and Pressureless Sintering

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SSRN 2024年

作者： Sakri, Shambhavi Haridas, Ravi Sankar Mishra, Rajiv S. Shepherd, Nigel D. Department of Materials Science and Engineering University of North Texas DentonTX76203 United States Department of Mechanical Engineering University of North Texas DentonTX76203 United States

The capability of direct-write extrusion-based microdispensing for additive manufacturing of Ti6Al4V was assessed, and a relative density of 88% of the bulk Ti6Al4V value was achieved with post-print pressureless sintering. Debinding in a high vacuum of 10-6 Torr or better was essential for the elimination of the dispersing phase and obtaining good Ti6Al4V phase purity without the formation of undesired oxides or carbides. Through control of the particle size distribution in the slurry design, the available interfacial free energy to drive diffusion, sintering, densification, and the resultant mechanical properties could be tuned. Specifically, high yield strengths (786 [[EQUATION]] 76 MPa which compares to 905 MPa for bulk titanium) and low plasticity could be obtained for the smallest particle sizes/largest specific surface area specimens, while the opposite was observed for builds that used larger particle sizes/smaller specific surface areas. Compression testing revealed that the pathways for failure generally increased with increasing porosity, and comparison of the modeled energy absorption vs relative density correlation with its experimental equivalent yielded good fits. Overall, the mechanical properties appear to be dominated by the pore structure. The results highlight the potential of direct-write, slurry design, and pressureless sintering for creating components with graded mechanical properties and architectured materials. © 2024, The Authors. All rights reserved.

关键词： Sintering

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Cooperative Jamming of Multi UAVs to Netted Radar

Cooperative Jamming of Multi UAVs to Netted Radar

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2021 International Conference on Advances in Optics and Computational sciences, ICAOCS 2021

作者： Gao, Zhi Sun, Hao Li, Fei Guo, Sai Wang, Jianming Fang, Lei Zhao, Chaohui School of Mechanical Engineering University of Shanghai for Science and Technology Shanghai200093 China School of Materials Science and Engineering University of Shanghai for Science and Technology Shanghai200093 China

This paper analyzes the cooperative jamming problem of multi UAVs to netted radar, controls the given constraints, adopts the optimal control algorithm to analyze the movement law of UAVs in layers. Based on the single UAV track model, the cooperative jamming track model of multiple UAVs is established, and the optimal UAV track number and the number of false target tracks are calculated, The movement law of UAV track and false target track is analyzed. Firstly, according to the range deception principle of cooperative jamming of UAV to netted radar, the kinematics model of single UAV is established, and the motion parameters of false target point and UAV are obtained;on the basis of single UAV, the motion model of multiple UAVs Cooperative jamming netted radar is established, and the motion parameters of false target point and UAV are also determined. Since multiple UAVs need to meet the "homology test"of Netted Radars, it is necessary to select the optimal control algorithm to optimize the control of multiple UAVs to obtain the optimized UAV and false target track, so as to achieve the purpose of cooperative jamming. Then, according to the optimal trajectory of UAV, the change of speed is determined, and the number of UAVs is determined by selecting the number of time points of UAV moving in a straight line with uniform speed by optimizing the value of speed. In this paper, by layering the tracks of potential false targets, several reasonable tracks which are most likely to exist are selected, and then the tracks and motion laws of the other two UAVs are determined by the linear equation between these track points and the other two radars which determine the track points, flight altitude and flight speed. © Published under licence by IOP Publishing Ltd.

关键词： Unmanned aerial vehicles (UAV)

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Giant twist-angle dependence of thermal conductivity in bilayer graphene originating from strong interlayer coupling

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Physical Review B 2023年第24期108卷 L241405-L241405页

作者： H. F. Feng B. Liu Zhi-Xin Guo State Key Laboratory for Mechanical Behavior of Materials Center for Spintronics and Quantum System School of Materials Science and Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

Recently, the twist-angle effect on two-dimensional van der Waals (vdW) materials, such as bilayer graphene, has attracted great attention. Many novel electronic, magnetic, and even optical properties induced by such effects have been discovered. However, the twist-angle effect on a phononic property is not so remarkable. By investigating the thermal conductivity of twisted bilayer graphene (TBG), we reveal that the trivial twist-angle effect on a phononic property observed in previous studies is owing to the nonlocalization nature of phonons. This characteristic makes phonons hardly trapped by the weak interlayer potentials induced by the twist-angle dependent moiré pattern. We propose that the twist-angle effect can be effectively enhanced by increasing the interface coupling. Using a sandwich structure composed of hexagonal boron nitride and TBG, we demonstrate that the thermal conductivity of TBG can be either significantly increased or dramatically decreased under the synergistic modulation of interlayer-coupling strength and twist angle. Particularly, the twist-angle effect can lead to a nontrivial reduction of thermal conductivity by up to 78% when a strong interlayer coupling is applied. The reduction is several times larger than that observed in the freestanding TBG originating from the twist-angle dependent phonon scatterings induced by the edge phonons. The underlying mechanism for the giant twist-angle dependent thermal conductivity is further revealed based on phonon transport theory. Our findings provide a platform for achieving efficient twist-angle modulation on the phonon transport property of vdW materials.

关键词： Phonons Twisted bilayer graphene Molecular dynamics

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Analysis and Comparison of Sliding Mode Controller for the Boost Driver in LED Headlamps

Analysis and Comparison of Sliding Mode Controller for the B...

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2022 International Conference on Electrical, Electronics and Information engineering, EEIE 2022

作者： Cheng, Xufeng Liu, Chenyang Zhang, Yuliang Wang, Dianlong School of Mechanical Engineering Hebei University of Science and Technology Shijiazhuang China Marine Electrical College Dalian Maritime University Dalian China Shijiazhuang Tonhe Electronics Technologies Co. Ltd Shijiazhuang China School of Materials Science and Engineering Hebei University of Science and Technology Shijiazhuang China

In this paper, the performance of several sliding mode control strategies used for the boost driver in LED headlamps is analysed and compared. At first the topology, control framework, and mathematical model of the boost LED driver is presented. Based on the mathematical model, a traditional differential sliding mode control law, a terminal sliding mode control law with finite convergence time, and a 2nd-order sliding mode control law with the Super-Twisting algorithm are derived and designed. Finally the simulation models of these sliding mode control laws are built. Simulation results show that the terminal sliding mode control has a faster convergence speed than the traditional differential sliding mode control. And the 2nd-order sliding mode control has a fastest convergence speed and low chattering, but the control result has a certain overshoot. © Published under licence by IOP Publishing Ltd.

关键词： Sliding mode control

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Transforming layered 2D mats into multiphasic 3D nanofiber scaffolds with tailored gradient features for tissue regeneration

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BMEMat(BioMedical engineering materials) 2024年第1期2卷 160-179页

作者： S.M.Shatil Shahriar Navatha Shree Polavoram Syed Muntazir Andrabi Yajuan Su Donghee Lee Huy Quang Tran Samantha J.Schindler Jingwei Xie Department of Surgery-Transplant and Mary&Dick Holland Regenerative Medicine Program College of MedicineUniversity of Nebraska Medical CenterOmahaNebraskaUSA Eppley Institute for Research in Cancer and Allied Diseases College of MedicineUniversity of Nebraska Medical CenterOmahaNebraskaUSA Department of Mechanical and Materials Engineering University of Nebraska LincolnLincolnNebraskaUSA

Multiphasic scaffolds with tailored gradient features hold significant promise for tissue regeneration applications. Herein, this work reports the transformation of two-dimensional (2D) layered fiber mats into three-dimensional (3D) multiphasic scaffolds using a ‘solids-of-revolution’ inspired gas-foaming expansion technology. These scaffolds feature precise control over fiber alignment, pore size, and regional structure. Manipulating nanofiber mat layers and Pluronic F127 concentrations allows further customization of pore size and fiber alignment within different scaffold regions. The cellular response to multiphasic scaffolds demonstrates that the number of cells migrated and proliferated onto the scaffolds is mainly dependent on the pore size rather than fiber alignment. In vivo subcutaneous implantation of multiphasic scaffolds to rats reveals substantial cell infiltration, neo tissue formation, collagen deposition, and new vessel formation within scaffolds, greatly surpassing the capabilities of traditional nanofiber mats. Histological examination indicates the importance of optimizing pore size and fiber alignment for the promotion of cell infiltration and tissue regeneration. Overall, these scaffolds have potential applications in tissue modeling, studying tissue-tissue interactions, interface tissue engineering, and highthroughput screening for optimized tissue regeneration.

关键词： expansion gradients multiphasic scaffolds nanofiber mats tissue regeneration

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Doping Shortens the Metal/Metal Distance and Promotes OH Coverage in Non-Noble Acidic Oxygen Evolution Reaction Catalysts

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Journal of the American Chemical Society 2023年第14期145卷 7829-7836页

作者： Wang, Ning Ou, Pengfei Miao, Rui Kai Chang, Yuxin Wang, Ziyun Hung, Sung-Fu Abed, Jehad Ozden, Adnan Chen, Hsuan-Yu Wu, Heng-Liang Huang, Jianan Erick Zhou, Daojin Ni, Weiyan Fan, Lizhou Yan, Yu Peng, Tao Sinton, David Liu, Yongchang Liang, Hongyan Sargent, Edward H. Department of Electrical and Computer Engineering University of Toronto 35 St George Street TorontoONM5S 1A4 Canada School of Materials Science and Engineering Key Laboratory of Efficient Utilization of Low and Medium Grade Energy Ministry of Education Tianjin University Tianjin300350 China Department of Mechanical and Industrial Engineering University of Toronto 5 King’s College Road TorontoONM5S 3G8 Canada School of Chemical Sciences The University of Auckl Auckland1010 New Zealand Department of Applied Chemistry National Yang Ming Chiao Tung University Hsinchu300 Taiwan Center for Condensed Matter Sciences National Taiwan University Taipei10617 Taiwan Center of Atomic Initiative for New Materials National Taiwan University Taipei10617 Taiwan State Key Lab of Hydraulic Engineering Simulation and Safety School of Materials Science & Engineering Tianjin University Tianjin300354 China

Acidic water electrolysis enables the production of hydrogen for use as a chemical and as a fuel. The acidic environment hinders water electrolysis on non-noble catalysts, a result of the sluggish kinetics associated with the adsorbate evolution mechanism, reliant as it is on four concerted proton-electron transfer steps. Enabling a faster mechanism with non-noble catalysts will help to further advance acidic water electrolysis. Here, we report evidence that doping Ba cations into a Co3O4 framework to form Co3-xBaxO4 promotes the oxide path mechanism and simultaneously improves activity in acidic electrolytes. Co3-xBaxO4 catalysts reported herein exhibit an overpotential of 278 mV at 10 mA/cm2 in 0.5 M H2SO4 electrolyte and are stable over 110 h of continuous water oxidation operation. We find that the incorporation of Ba cations shortens the Co-Co distance and promotes OH adsorption, findings we link to improved water oxidation in acidic electrolyte. © 2023 American Chemical Society.

关键词： Catalysts

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