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SSRN 2022年

作者： Gunnewiek, Rodolfo Foster Klein Perdomo, Claudia P.F. Almeida, Diógenes F. Cancellieri, Igor C. Garcia, Leonardo A. Cardoso, André L.F. Federal University of São Carlos Graduate Program in Materials Science and Engineering Rod. Washington Luiz km 235 SP São Carlos13565-905 Brazil Federal University of Alfenas Graduate Program in Materials Science and Engineering Rod. José Aurélio Vilela BR 267 Km 533 11999 MG Poços de Caldas37715-400 Brazil Federal University of Alfenas Institute of Science and Technology Rod. José Aurélio Vilela BR 267 Km 533 11999 MG Poços de Caldas37715-400 Brazil

Room temperature ferromagnetism (RTFM) is the main condition for searching for materials to be applied in spintronics. Beyond the candidates, the diluted magnetic semiconductors (DMS) are potential materials for such application. The introduction of a foreign transition metal ion in the semiconductor lattice may lead to the RTFM, where the intrinsic ferromagnetism developed by a nonmagnetic ion is preferable for spintronics application. In this work, single-phase Cu-substituted zinc oxide was synthesized by a fast polymeric precursor method, providing nanocrystallites from 4 to 11 nm. Copper hindered grain growth, even for high Cu concentrations. The crystallites assembled to superstructures with petal and spike-like morphologies, following an unconventional crystallization. The texturization observed during the crystallization led to the development of unexpected weak RTFM. The number of oxygen vacancies is too small to promote the RTFM since few atoms of copper find attached to the vacancies. Probably the RTFM arises from overlapped spin-split bound magnetic polarons (BMP) due to the interaction of the hybridized O 2p and localized unoccupied twofold t2 subband of Cu 3d states. Although the sintering of pure and Cu-doped ZnO particles was equivalent, the electrical properties diverged. The copper insertion enhanced the resistivity and the non-linearity coefficient reached values higher than the unity. This is maybe due to the presence of copper at the grain boundaries forming a Schottky barrier. Neither the non-ohmic electrical behavior nor the RTFM from nanostructured superstructures was ever reported before. © 2022, The Authors. All rights reserved.

关键词： II-VI semiconductors

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Reduction of interface defects in gate-recessed GaN HEMTs by neutral beam etching

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materials Today Advances 2024年 23卷

作者： Yu, Chia Hao Chiang, Wei Hsiang Chen, Yi-Ho Samukawa, Seiji Wuu, Dong Sing Chung, Chin-Han Hsiao, Ching-Lien Horng, Ray Hua Institute of Electronics National Yang Ming Chiao Tung University Department of Materials Science and Engineering National Chung Hsing University Graduate Degree Program of College of Electrical and Computer Engineering National Yang Ming Chiao Tung University Institute of Comunications Engineering National Yang Ming Chiao Tung University Department of Applied Materials and Optoelectronic Engineering National Chi Nan University International College of Semiconductor Technology National Yang Ming Chiao Tung University Thin Film Physics Division Department of Physics Chemistry and Biology (IFM) Linköping University

This study investigates and compares the impact of different etching techniques on the fabrication of GaN high electron mobility transistors (HEMTs) between the inductively coupled plasma reactive ion etching (ICP-RIE) and the neutral beam etching (NBE) for the gate recess. By conducting direct current analysis, it was found that devices manufactured using the NBE exhibited superior electrical performance as compared with those produced using the ICP-RIE. These enhanced electrical characteristics include a transconductance of up to 100.4 mS/mm, a threshold voltage (V_th) of −2.3 V, an on/off current ratio of 1.1 × 10⁹, a subthreshold swing (S.S.) of 99.63 mV/dec, and a remarkably low gate leakage current. Additionally, we noted varying degrees of hysteresis in the I–V characteristics were related to process disparities possibly leading to interface defects. Multi-frequency capacitance-voltage (C–V) measurements were used to identify the interface defects at the oxide/AlGaN interface of the gate. The results revealed that devices fabricated using the NBE exhibited a lower interface defect density as compared with those fabricated using the ICP-RIE, thereby elucidating the reduced hysteresis observed in the I–V characteristics. These findings indicated the significant advantages of the NBE process in the fabrication of GaN HEMTs. © 2024 The Authors

关键词： GaN HEMTs Gate recess Interface defects Multi-frequency C–V Neutral beam etching

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Exotic Magnetism in Oxidized Copper Chloride

SSRN

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SSRN 2023年

作者： Pimentel, Dyvison Pedreira Campinas São Paulo13083-859 Brazil Federal Institute of Maranhão IFMA-PPGEM Avenida Getúlio Vargas 4 MA São LuísCEP 65030-005 Brazil PPGCM-Materials Science and Engineering Graduate Program UFPI-Federal University of Piaui PI Teresina64049-550 Brazil

In this work magnetization measurements in oxidized CuCl are presented. Two magnetic transitions are clearly observed, one around 6.4 K and the other around 18 K. Such magnetic transitions are closely related to Clinoatacamite Cu2Cl(OH)3. Interestingly, another transition is observed at 16 K which is also very difficult to know its origin. The apparent "diamagnetism" observed in the ZFC measurements is due to the exchange bias effect, leading to the conclusion that our CuCl samples are in a highly frustrated state due to the presence of clinoatacamite. X-ray diffractograms at different time intervals of exposure to air of the virgin CuCl sample to determine the appearance of new phases in the material composition were carried out. The results obtained show us that an exposure prolonged exposure to air, air humidity and oxygen actually leads to the gradual transformation of CuCl to Clinoatacamite. © 2023, The Authors. All rights reserved.

关键词： Copper compounds

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Magnetically tuned continuous transition from weak to strong coupling in terahertz magnon polaritons

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Physical Review Research 2023年第1期5卷 L012039-L012039页

作者： Andrey Baydin Kenji Hayashida Takuma Makihara Fuyang Tay Xiaoxuan Ma Wei Ren Guohong Ma G. Timothy Noe, II Ikufumi Katayama Jun Takeda Hiroyuki Nojiri Shixun Cao Motoaki Bamba Junichiro Kono Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Smalley-Curl Institute Rice University Houston Texas 77005 USA Division of Applied Physics Graduate School of Engineering Hokkaido University Sapporo Hokkaido 060-8628 Japan Department of Physics and Astronomy Rice University Houston Texas 77005 USA Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA Department of Physics International Center of Quantum and Molecular Structures and Materials Genome Institute Shanghai University 200444 Shanghai China Department of Physics Graduate School of Engineering Science Yokohama National University Yokohama 240-8501 Japan Institute for Materials Research Tohoku University Sendai 980-8577 Japan The Hakubi Center for Advanced Research Kyoto University Kyoto 606-8502 Japan Department of Physics I Kyoto University Kyoto 606-8502 Japan PRESTO Japan Science and Technology Agency Kawaguchi 332-0012 Japan Department of Materials Science and NanoEngineering Rice University Houston Texas 77005 USA

Depending on the relative rates of coupling and dissipation, a light-matter coupled system is either in the weak- or strong-coupling regime. Here, we present a unique system where the coupling rate continuously increases with an externally applied magnetic field while the dissipation rate remains constant, allowing us to monitor a weak-to-strong coupling transition as a function of magnetic field. We observed a Rabi splitting of a terahertz magnon mode in yttrium orthoferrite above a threshold magnetic field of ∼14 T. Based on a microscopic theoretical model, we show that with increasing magnetic field the magnons transition into magnon polaritons through an exceptional point, which will open up new opportunities for in situ control of non-Hermitian systems.

关键词： Antiferromagnetism High magnetic fields Magneto-optics Magnons Polaritons Non-Hermitean systems Terahertz time-domain spectroscopy Transfer matrix method

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Effect of Surface Activation on the Corrosion Resistance of a MAO/Ni-P Composite Coating on LZ91 Magnesium Alloy

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Journal of the Taiwan Institute of Chemical Engineers 2023年第1期147卷

作者： Chen, Chi-An Lee, Jeou-Long Jian, Shun-Yi Lee, Chia-Yu Ger, Ming-Der Combination Medical Device Technology Division Medical Devices R&D Service Department Metal Industries Research & Development Centre Kaohsiung802 Taiwan Department of Chemical and Materials Engineering Lung Hwa University of Science and Technology Taoyuan330 Taiwan Department of Material Engineering Ming Chi University of Technology New Taipei City Taiwan Center for Plasma and Thin Film Technologies Ming Chi University of Technology New Taipei Taiwan Graduate School of Defense Science Chung Cheng Institute of Technology National Defense University Taoyuan Taiwan Department of Chemical & Materials Engineering Chung Cheng Institute of Technology National Defense University Taoyuan Taiwan System Engineering and Technology Program National Chiao Tung University Hsin-Chu Taiwan

Background: LZ91 Magnesium alloy with a dual-phase structure has improved mechanical properties and a low density of about 1.48 g/cm3 but their limited resistance to corrosion limits their application. Therefore, it is a great challenge to increase the stability of LZ91 alloys under corrosive factors and environments. Methods: This study uses micro-arc oxidation (MAO) and an electroless nickel-phosphorus (Ni-P) plated composite film to increase the corrosion resistance of LZ91 magnesium alloy. Before electroless Ni-P plating, the MAO layers are activated by palladium catalysts at different pH values to produce composite coatings. SEM, EDS and Image J are used to determine the surface properties and elemental composition of the samples. The corrosion resistance is measured using a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. Findings: The results show that the MAO coating is activated by an acid catalyst and the surface is obviously corroded. The electroless Ni-P plating grows into the MAO coating and the substrate corrodes. Therefore, corrosive medium (chloride ion) easily enter to the substrate and pitting corrosion occurred. On the contrary, activation by a neutral catalyst (pH=7) maintains the original structure of the MAO coating and provides a good bonding interface for the Ni-P coating. Form the potentiodynamic analysis can be finds that the corrosion potential for the neutral catalyst treated sample is -0.35V and the corrosion current density value is 1.77×10−6 A/cm2, so the corrosion characteristic become better than the acid catalyst treated samples. In terms of the long-term resistance after 48 h, EIS analysis shows that the resistance value remains at about 7.6×104 Ω•cm2. A composite coating that is compact and with excellent resistance to corrosion resistance is produced, which provides better protection for LZ91 magnesium alloys. © 2023 Taiwan Institute of Chemical Engineers

关键词： Corrosion resistance

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Amino-functionalized reduced graphene oxide@MoS2@CoS2 heterostructure as a high-rate anode material for ultralong lifespan sodium–sulfur batteries

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New Journal of Chemistry 2025年第24期49卷 10379-10387页

作者： Navid Aslfattahi Maryam Sadat Kiai Nilgun Baydogan Lingenthiran Samylingam Kumaran Kadirgama Chee Kuang Kok Department of Fluid Dynamics and Thermodynamics Faculty of Mechanical Engineering Czech Technical University in Prague Prague 166 07 Czech Republic Nano-Science and Nano-Engineering Program Graduate School of Science Engineering and Technology Istanbul Technical University Istanbul-34469 Turkey Energy Institute Ayazaga Campus Istanbul Technical University Maslak Istanbul Turkey Centre for Advanced Mechanical and Green Technology Center of Excellence for Robotics & Sensing Technologies Faculty of Engineering and Technology Multimedia University Jalan Ayer Keroh Lama Bukit Beruang 75450 Melaka Malaysia Faculty of Mechanical and Automotive Engineering Technology Universiti Malaysia Pahang 26600 Pekan Malaysia Centre for Research in Advanced Fluid and Process University Malaysia Pahang Al-Sultan Abdullah Lebuhraya Tun Razak Gambang Kuantan Pahang Malaysia Centre for Sustainable Materials & Surface Metamorphosis (CSMSM) Chennai Institute of Technology Chennai India

A nanocomposite comprising MoS2@CoS2 amino-functionalized graphene (En-RGO) with a two-dimensional structure has been successfully synthesized using a simple self-assembly technique. The resulting cell with a MoS2@CoS...

A nanocomposite comprising MoS₂@CoS₂ amino-functionalized graphene (En-RGO) with a two-dimensional structure has been successfully synthesized using a simple self-assembly technique. The resulting cell with a MoS₂@CoS₂@En-RGO anode and a sulfur cathode exhibits a superior hierarchical architecture that significantly facilitates ion mobility, cell conductivity, and pseudocapacitance. Consequently, this leads to improved rate performance and extended cycle stability in Na–S batteries. Micron-sized CoS₂ was synthesized by solvothermal growth of MoS₂ nanosheets on its surface. This composite material presents enhanced sodium-ion diffusion kinetics attributed to its heterogeneous interface, reduced ion diffusion pathways and increased exposure of active sites for sodium storage due to its hierarchical nanosheet structure. Additionally, amino functionalized graphene oxide with uniform nitrogen doping could improve electronic conductivity. The cell employing MoS₂@CoS₂@En-RGO with superior ion mobility and enhanced adsorption energy of Na⁺ ions achieves a cycle stability of 541.2 mA h g⁻¹ after 1800 cycles. The increased adsorption energy facilitates a more efficient sodiation process at MoS₂@CoS₂@En-RGO compared to En-RGO. Additionally, the MoS₂@CoS₂@En-RGO anode demonstrates a capacity retention of 95.8% after 1800 cycles at 1 A g⁻¹. The enhanced mobility of Na ions and the effective adsorption of polysulfide chains in MoS₂@CoS₂@En-RGO have been examined through DFT calculations, confirming its potential as a promising anode material for

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Evidence for Two-Stage Hardening in an Al-Zn-Mg-Cu Alloy Processed by High-Pressure Torsion

SSRN

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SSRN 2022年

作者： dos Santos, Igor Cuzzuol Mazzer, Eric M. Figueiredo, Roberto B. Langdon, Terence G. Rodrigues Pereira, Pedro Henrique Graduate Program in Metallurgical Materials and Mining Engineering Universidade Federal de Minas Gerais MG Belo Horizonte31270-901 Brazil Department of Materials Science and Engineering Universidade Federal de São Carlos SP São Carlos13565-905 Brazil Department of Metallurgical and Materials Engineering Universidade Federal de Minas Gerais MG Belo Horizonte31270-901 Brazil Materials Research Group Department of Mechanical Engineering University of Southampton SouthamptonSO17 1BJ United Kingdom

Experiments were conducted to assess the effect of torsional straining on the microstructural evolution of an Al-5.7Zn-1.8Mg-2.1Cu alloy containing dispersed second phase particles prior to deformation. The results show that the material exhibits two distinct and consecutive hardening stages when processed through 1/8, 1, 5, 30, 50 and 100 turns in high-pressure torsion (HPT). There is an initial increase in the Vickers hardness from ~120 Hv in the unprocessed state to ~240 Hv after 1 turn. In this first stage, hardening occurs primarily through the accumulation and rearrangement of dislocations into fine cells/subgrains. A quasi-stationary condition is achieved with further straining where the microhardness remains nearly constant and the grain size is ~140 nm up to 30 revolutions. Thereafter, the microstructure consists of ultrafine and slightly elongated grains but the second phases are continuously fragmented. This fragmentation produces a new hardening stage and the development of a uniform array of highly elongated grains with an average size of ~93 nm after 100 HPT turns. It is shown that this two-stage hardening is consistent with conventional Hall-Petch strengthening and the development of the second stage is attributed to a reduction in grain boundary mobility due to the segregation of solutes. © 2022, The Authors. All rights reserved.

关键词： Aluminum alloys

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Anomalous properties of spark plasma sintered boron nitride solids

arXiv

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arXiv 2024年

作者： Biswas, Abhijit Serles, Peter Alvarez, Gustavo A. Schimpf, Jesse Hache, Michel Kong, Jonathan Demingos, Pedro Guerra Yuan, Bo Pieshkov, Tymofii S. Li, Chenxi Puthirath, Anand B. Gao, Bin Gray, Tia Zhang, Xiang Murukeshan, Jishnu Vajtai, Robert Dai, Pengcheng Singh, Chandra Veer Howe, Jane Zou, Yu Martin, Lane W. Clancy, James Patrick Tian, Zhiting Filleter, Tobin Ajayan, Pulickel M. Department of Materials Science and Nanoengineering Rice University HoustonTX77005 United States Department of Mechanical & Industrial Engineering University of Toronto 5 King’s College Road TorontoM5S 3G8 Canada Sibley School of Mechanical and Aerospace Engineering Cornell University IthacaNY14853 United States Department of Materials Science and Engineering University of California Berkeley United States Department of Materials Science and Engineering University of Toronto 184 College St TorontoM5S 3E4 Canada Department of Physics and Astronomy McMaster University HamiltonL8S 4M1 Canada Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Materials Sciences Division Lawrence Berkeley National Laboratory United States

Hexagonal boron nitride (h-BN) is brittle, however, its atomic-scale structural engineering can lead to unprecedented physical properties. Here we report the bulk synthesis of high-density crystalline h-BN solids by using high-temperature spark plasma sintering (SPS) of micron size h-BN powders. In addition to the high mechanical strength and ductile response of such materials, we have obtained anomalous values of dielectric constant beyond theoretical limits, high thermal conductivity, and exceptional neutron radiation shielding capability. Through exhaustive characterizations we reveal that SPS induces non-basal plane crystallinity, twisting of layers, and facilitates inter-grain fusion with a high degree of in-plane alignment across macroscale dimensions, resulting in near-theoretical density and anomalous properties. Our findings highlight the importance of material design, via new approaches such as twisting and interconnections between atomically thin layers, to create novel ceramics with properties that could go beyond their intrinsic theoretical predictions. © 2024, CC BY.

关键词： Spark plasma sintering

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Nonlocal phase-change metaoptics for reconfigurable nonvolatile image processing

arXiv

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arXiv 2024年

作者： Yang, Guoce Wang, Mengyun Lee, June Sang Farmakidis, Nikolaos Shields, Joe de Galarreta, Carlota Ruiz Kendall, Stuart Bertolotti, Jacopo Moskalenko, Andriy Huang, Kairan Alù, Andrea Wright, C. David Bhaskaran, Harish Department of Materials University of Oxford Parks Road OX1 3PH United Kingdom Department of Engineering University of Exeter ExeterEX4 QF United Kingdom Photonics Initiative Advanced Science Research Center City University of New York New York United States Physics Program Graduate Center City University of New York New York United States

The next generation of smart imaging and vision systems will require compact and tunable optical computing hardware to perform high-speed and low-power image processing. These requirements are driving the development of computing metasurfaces to realize efficient front-end analog optical pre-processors, especially for edge-detection capability. Yet, there is still a lack of reconfigurable or programmable schemes, which may drastically enhance the impact of these devices at the system level. Here, we propose and experimentally demonstrate a reconfigurable flat optical image processor using low-loss phase-change nonlocal metasurfaces. The metasurface is configured to realize different transfer functions in spatial frequency space, when transitioning the phase-change material between its amorphous and crystalline phases. This enables edge detection and bright-field imaging modes on the same device. The metasurface is compatible with a large numerical aperture of ~0.5, making it suitable for high resolution coherent optical imaging microscopy. The concept of phase-change reconfigurable nonlocal metasurfaces may enable emerging applications of artificial intelligence-assisted imaging and vision devices with switchable multitasking. © 2024, CC BY.

关键词： Image enhancement

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A Novel Method for the Fabrication of Antibacterial Stainless Steel with Uniform Silver Dispersions by Silver Nanoparticle/Polyethyleneimine Composites

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materials 2023年第10期16卷 3719-3719页

作者： Chih, Yu-Kun You, Jhu-Lin Lin, Wei-Hsuan Chang, Yen-Hao Tseng, Chun-Chieh Ger, Ming-Der Graduate School of Defense Science Chung Cheng Institute of Technology National Defense University Taoyuan335 Taiwan Department of Chemical and Materials Engineering Chung Cheng Institute of Technology National Defense University Taoyuan335 Taiwan System Engineering and Technology Program National Chiao Tung University Hsinchu300 Taiwan Combination Medical Device Technology Division Medical Devices and Opto-Electronics Equipment Department Metal Industries Research & Development Centre Kaohsiung821 Taiwan

Only a few studies have so far focused on the addition of silver to SS316L alloys by conventional sintering methods. Unfortunately, the metallurgical process of silver-containing antimicrobial SS is greatly limited due to the extremely low solubility of silver in iron and its tendency to precipitate at the grain boundaries, resulting in an inhomogeneous distribution of the antimicrobial phase and loss of antimicrobial properties. In this work, we present a novel approach to fabricate antibacterial stainless steel 316L by functional polyethyleneimine-glutaraldehyde copolymer (PEI-co-GA/Ag catalyst) composites. PEI is a highly branched cationic polymer, which makes it exhibit very good adhesion on the surface of the substrate. Unlike the effect of the conventional silver mirror reaction, the introduction of functional polymers can effectively improve the adhesion and distribution of Ag particles on the surface of 316LSS. It can be seen from the SEM images that a large number of silver particles are retained and well dispersed in 316LSS after sintering. PEI-co-GA/Ag 316LSS exhibits excellent antimicrobial properties and does not release free silver ions to affect the surrounding environment. Furthermore, the probable mechanism for the influence of the functional composites on the enhancement of adhesion is also proposed. The formation of a large number of hydrogen bonds and van der Waals forces, as well as the negative zeta potential of the 316LSS surface, can effectively enable the formation of a tight attraction between the Cu layer and the surface of 316LSS. These results meet our expectations of designing passive antimicrobial properties on the contact surface of medical devices. © 2023 by the authors.

关键词： Silver nanoparticles

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