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X-ray and molecular dynamics study of the temperature-dependent structure of molten NaF-ZrF4

Physical Review materials 2024年第7期8卷 075402-075402页

作者： Anubhav Wadehra Rajni Chahal Shubhojit Banerjee Alexander Levy Yifan Zhang Haoxuan Yan Daniel Olds Yu Zhong Uday Pal Stephen Lam Karl Ludwig Division of Materials Science and Engineering Chemical Science Division Department of Chemical Engineering Department of Mechanical Engineering Department of Mechanical and Materials Engineering National Synchrotron Light Source II Department of Physics

The local atomic structure of NaF-ZrF4 (53–47 mol%) molten system and its evolution with temperature are examined with x-ray scattering measurements which are then used to validate the quality of ab initio and neural network-based molecular dynamics (NNMD) calculations in the temperature range 515−700∘C. The machine-learning enhanced NNMD calculations offer improved efficiency while maintaining accuracy at higher distances compared to ab initio calculations. Looking at the evolution of the pair distribution function with increasing temperature, a fundamental change in the liquid structure within the selected temperature range, accompanied by a slight decrease in overall correlation is revealed. NNMD calculations indicate the coexistence of three different fluorozirconate complexes: [ZrF6]2−, [ZrF7]3−, and [ZrF8]4−, with a shift in the dominant coordination state from the 7-coordinated Zr cation toward a 6-coordinated cation with increasing temperature. The study also highlights the metastability of different local coordination structures, with frequent interconversions between the 6- and 7-coordinate states. Analysis of the Zr-F-Zr angular distribution function reveals the presence of both “edge-sharing” and “corner-sharing” fluorozirconate complexes with specific bond angles and distances in accord with previous studies, while the next-nearest-neighbor cation-cation correlations demonstrate a clear preference for unlike cations as nearest-neighbor pairs, emphasizing nonrandom arrangement. These findings contribute to a comprehensive understanding of the complex local structure of the molten salt, providing insights into temperature-dependent preferences and correlations within the molten system.

关键词： Atomic & molecular structure Ionic fluids Liquids Ab initio molecular dynamics Machine learning X-ray pair-distribution function analysis X-ray scattering

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High sound pressure piezoelectric micromachined ultrasonic transducers using sputtered potassium sodium niobate

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Microsystems & Nanoengineering 2024年第6期10卷 311-323页

作者： Fan Xia Yande Peng Wei Yue Mingze Luo Megan Teng Chun-Ming Chen Sedat Pala Xiaoyang Yu Yuanzheng Ma Megha Acharya Ryuichi Arakawa Lane W.Martin Liwei Lin Department of Mechanical Engineering University of CaliforniaBerkeleyCA 94720USA School of Electronic Science and Engineering Southeast UniversityNanjingJiangsu 210096China Bioengineering and Biomedical Engineering Xi’an Jiaotong UniversityXi’anShaanxi 710049China Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China Department of Materials Science and Engineering University of CaliforniaBerkeleyCA 94720USA Scientific Research Laboratory Div. Niterra Co.LtdNagoya 461-0005Japan Departments of Materials Science and NanoEngineering Chemistryand Physics and Astronomy and the Rice Advanced Materials InstituteRice UniversityHoustonTX 77005USA

This work presents air-coupled piezoelectric micromachined ultrasonic transducers(pMUTs)with high sound pressure level(SPL)under low-driving voltages by utilizing sputtered potassium sodium niobate K0.34Na0.66NbO3(KNN)films.A prototype single KNN pMUT has been tested to show a resonant frequency at 106.3 kHz under 4 Vp-p with outstanding characteristics:(1)a large vibration amplitude of 3.74μm/V,and(2)a high acoustic root mean square(RMS)sound pressure level of 105.5 dB/V at 10 cm,which is 5–10 times higher than those of AlN-based pMUTs at a similar *** are various potential sensing and actuating applications,such as fingerprint sensing,touch point,and gesture *** this work,we present demonstrations in three fields:haptics,loudspeakers,and *** haptics,an array of 15×15 KNN pMUTs is used as a non-contact actuator to provide a focal pressure of around 160.3 dB RMS SPL at a distance of 15 *** represents the highest output pressure achieved by an airborne pMUT for haptic sensation on human *** used as a loudspeaker,a single pMUT element with a resonant frequency close to the audible range at 22.8 kHz is *** is shown to be able to generate a uniform acoustic output with an amplitude modulation *** the rangefinder application,pulse-echo measurements using a single pMUT element demonstrate good transceiving results,capable of detecting objects up to 2.82 m *** such,this new class of high-SPL and low-driving-voltage pMUTs could be further extended to other applications requiring high acoustic pressure and a small form factor.

关键词： potassium piezoelectric sound

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A Low-cost Surface Modified Battery-used Polyethylene Membranes for Reverse Osmosis Applications

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materials Research Innovations 2023年第5期27卷 348-354页

作者： Song, Yiye Zhang, Ye Yang, Hongjun Jiangsu Key Laboratory of Environmentally Friendly Polymeric Materials School of Materials Science and Engineering Jiangsu Collaborative Innovation Centre of Photovoltaic Science and Engineering Changzhou University Changzhou213164 China Department of Mechanical and Material Engineering Changzhou University Huaide College Jingjiang214500 China

Reverse osmosis (RO) membranes have been widely used in the field of membrane separation. However, most of the commercial RO membranes are fabricated based on a polysulphones- or polyethersulfone-modified polyethylene glycol terephthalate (PET) support, which are thick and exhibit poor solvent resistance. In this study, polyethylene (PE) battery membranes without any hydrophilic modification were directly used to prepare PE-RO membranes. The structures of the products were confirmed via attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The resulting RO membrane prepared with 0.05 wt.% of trimesoyl chloride and 2 wt.% of m-phenylenediamine exhibited a water flux of 12.61 L m−2 h−1 with a desalination (NaCl) rate of 98.6%. The thickness of the PE-RO membrane is 80% of the thickness of the traditional RO membranes and hence has a wider application as a separation membrane. © 2022 Informa UK Limited, trading as Taylor & Francis Group.

关键词： Polyethylenes

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Correlation between hydration properties and electrochemical performances on Ln cation size effect in layered perovskite for protonic ceramic fuel cells

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Journal of Energy Chemistry 2024年第1期88卷 1-9,I0001页

作者： Inhyeok Cho Jiwon Yun Boseok Seong Junseok Kim Sun Hee Choi Ho-Il Ji Sihyuk Choi Department of Mechanical Engineering Kumoh National Institute of TechnologyGumi 39177GyeongbukRepublic of Korea Department of Aeronautics Mechanical and Electronic Convergence EngineeringKumoh National Institute of TechnologyGumi 39177GyeongbukRepublic of Korea Center for Energy Materials Research Korea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Center for Hydrogen and Fuel Cell Research Clean Technology Research DivisionKorea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Department of Energy and Environmental Engineering University of Science and TechnologySeoul 02792Republic of Korea Nanomaterials Science and Engineering Korea University of Science and Technology(UST)KIST CampusSeoul 02792Republic of Korea

PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula for Pr BSCF is AA'B_(2)O_(5+δ), with Pr(A-site) and Ba/Sr(A'-site) alternately stacked along the c-axis. Due to these structural features, the bulk oxygen ion diffusivity is significantly enhanced through the disorder-free channels in the PrO layer;thus, the A site cations(lanthanide ions) play a pivotal role in determining the overall electrochemical properties of layered perovskites. Consequently, previous research has predominantly focused on the electrical properties and oxygen bulk/surface kinetics of Ln cation effects,whereas the hydration properties for PCFC systems remain unidentified. Here, we thoroughly examined the proton uptake behavior and thermodynamic parameters for the hydration reaction to conclusively determine the changes in the electrochemical performances depending on LnBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(LnBSCF,Ln=Pr, Nd, and Gd) cathodes. At 500 ℃, the quantitative proton concentration of PrBSCF was 2.04 mol% and progressively decreased as the Ln cation size decreased. Similarly, the Gibbs free energy indicated that less energy was required for the formation of protonic defects in the order of Pr BSCF < Nd BSCF < Gd BSCF. To elucidate the close relationship between hydration properties and electrochemical performances in LnBSCF cathodes, PCFC single cell measurements and analysis of the distribution of relaxation time were further investigated.

关键词： Protonic ceramic fuel cell Cathode Triple ionic and electronic conductor Hydration property Proton uptake Gibbs free energy

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Analyzing the Effects of Milling and Sintering Parameters on Crystalline Phase Evolution and mechanical Properties of Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) Amorphous Ribbons

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Acta Metallurgica Sinica(English Letters) 2022年第6期35卷 1043-1054页

作者： Ashutosh Sahu Ram Sajeevan Maurya Lavish Kumar Singh Tapas Laha Department of Mechanical Engineering School of Engineering and TechnologySharda UniversityGreater Noida 201310India Department of Metallurgy Engineering and Materials Science Indian Institute of Technology IndoreIndore 453552India Department of Metallurgical and Materials Engineering Indian Institute of Technology KharagpurKharagpur 721302India

In the present study,Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) bulk amorphous nanocomposites were synthesized by spark plasma sintering of milled melt spun ribbon *** as-cast ribbons were of near amorphous nature with minute amount of FCC Al embedded in the amorphous *** of the ribbons resulted in partial devitrifi cation due to mechanical *** milled ribbon particles were sintered in the temperature and pressure range of 300-500℃ and 500-700 MPa,*** was observed that nominal amount of amorphous phase was retained at 500℃ and 500 *** increase in sintering pressure and decrease in sintering temperature,the amount of crystalline phase evolution decreased,and maximum amount of amorphous phase was retained at 300℃ and 700 *** microstructure consisting of amorphous phase embedded with hard intermetallic phases led to increase in the nanohardness of Al_(86)Ni_(8)Y_(6) and Al_(86)Ni_(6)Y_(4.5)Co_(2)La_(1.5) as-cast ribbons from 3.26±0.59 GPa and 3.81±0.58 GPa to 6.06±0.70 GPa and 6.14±0.82 GPa,respectively,for the corresponding consolidated amorphous *** of the three and five component system bulk samples was 4.19±0.13GPa and 3.6±0.13 GPa,respectively.

关键词： Amorphous alloy Milled ribbon Spark plasma Sintering Nanohardness Internetallic compound

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Modified tight-binding model for strain effects in monolayer transition metal dichalcogenides

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Physical Review B 2024年第24期109卷 245412-245412页

作者： Zhiwei Peng Zhizi Guan Hongfei Wang David J. Srolovitz Dangyuan Lei Department of Materials Science and Engineering and Centre for Functional Photonics Department of Mechanical Engineering

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have emerged as a materials paradigm for realizing next-generation on-chip electronic and optoelectronic devices. Strain engineering is actively pursued to tune the electronic properties of 2D TMDCs. However, a generalizable, analytical approach for describing the underlying physics of strain effects on band structure is still lacking. Here, we develop a tight-binding model (TBM) that incorporates strain effect to characterize the band structure tuning of TMDC (MoS2, MoSe2, WS2, and WSe2) monolayers under biaxial strain fields; strain-dependent Slater-Koster parameters are employed to describe electron hopping and orbital overlap in the strained monolayers. Our approach follows from the Wills-Harrison suggestions of a linear relationship between biaxial strain and Slater-Koster parameters. This leads to a linear dependence of the electronic band gap on applied strain for both direct-indirect (MoX2) and indirect-direct (WX2) band gap transitions. We further study the influence of biaxial strain on the energy differences between different high-symmetry points in k space to deduce the physical origin of strain-induced variations in the band gap type and size. In this process, we select different TBMs (6- or 11-band) and compare them with different first-principles calculation results (DFT-PBE or DFT-HSE) to demonstrate the effectiveness and completeness of our method. Building on this model, we also examined the changes in effective mass and optical conductivity of TMDCs under strain, offering insights that can aid in the development of practical device applications utilizing these materials. Our investigation may be extended to general strained monolayer TMDCs, paving the way for exploring the electronic properties of nanotubes, wrinkled 2D materials, and van der Waals heterostructures under inhomogeneous strain.

关键词： Strain Transition metal dichalcogenides Tight-binding model

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Promoting polysulfide conversions via cobalt single-atom catalyst for fast and durable lithium-sulfur batteries

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Nano Research 2023年第7期16卷 9335-9343页

作者： Ziwei Wang Yuwen Cheng Shanying Wang Jie Xu Bo Peng Dan Luo Lianbo Ma Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials&School of Materials Science and Engineering Anhui University of TechnologyMaanshan 243002China School of Information and Optoelectronic Science and Engineering South China Normal UniversityGuangzhou 510006China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology(HKUST)Clear Water BayHong Kong 999077China

Although promising strategies have been developed to resolve the critical drawbacks of lithium-sulfur(Li-S)batteries,the intractable issues including undesirable shuttling of polysulfides and sluggish redox reaction kinetics have still been unresolved ***,a cobalt single-atom(CoSA)catalyst comprising of atomic Co distributed homogeneously within nitrogen(N)-doped porous carbon(Co-NPC)nanosphere is constructed and utilized as a separator coating in Li-S *** Co-NPC exposes abundant active sites participating in sulfur redox reactions,and remarkable catalytic activity boosting the rapid polysulfide *** a result,Li-S batteries with Co-NPC coating layer realize significantly enhanced specific capacity(1295 mAh·g^(-1)at 0.2 C),rate capability(753 mAh·g^(-1)at 3.0 C),and long-life cyclic stability(601 mAh·g^(-1)after 500 cycles at 1.0 C).Increasing the areal sulfur loading to 6.2 mg·cm^(-2),an extremely high areal capacity of 7.92 mAh·cm^(-2)is *** in situ X-ray diffraction,density functional theory calculations,and secondary ion mass spectrometry confirm the high catalytic capability of CoSA towards reversible polysulfide *** study supplies new insights for adopting single-atom catalyst to upgrade the electrochemical performance of Li-S batteries.

关键词： lithium-sulfur batteries polysulfide shuttling sluggish redox kinetics cobalt single-atom catalyst catalytic capability

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Stress Distributions in Brazed Single-Lap Joints Under Tensile Loading (vol 54, pg 1116, 2023)

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METALLURGICAL AND materials TRANSACTIONS A-PHYSICAL METALLURGY AND materials science 2023年第8期54卷 3370-3370页

作者： Kemmenoe, D. J. Sibley School of Mechanical and Aerospace Engineering Cornell University Upson Hall Ithaca NY 14853 USA Department of Materials Science and Engineering Cornell University Bard Hall Ithaca NY 14853 USA

The most common method for characterizing the strength of brazed joints is uniaxial tension testing of single lap joints (SLJs). Standard interpretations depend on the assumption that the average shear stress at failure is the key metric in determining joint strength. However, it is evident from the geometry that the stress distributions must be inhomogeneous with shear lag type stress concentrations at the ends of the overlap regions. Eccentric loading causes overlap rotation and bending stresses that amplify the stress concentrations and result in geometric nonlinearity. Unfortunately, details of the distributions of normal and shear stresses on the braze needed to understand failure have not been presented. Thus, finite element analysis was used to quantify these stress distributions using 2D elastic and elasto-plastic models of monolithic stainless steel SLJs. Bending stresses and normal and shear stresses acting on the braze were determined over a wide range of overlap ratios and applied stresses. For all conditions, stresses are highly concentrated in a narrow region at overlap ends with peak normal stresses exceeding peak shear stresses. Variations in peak stresses with applied stress and overlap ratio were found to fully explain experimental joint strength data. Common interpretations based on the average shear stress at failure are found to be incorrect. Implications for testing, interpretation, and joint design are discussed.

关键词： Stress concentration

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Carbon nanotube-carbon black/CaCu_(3)Ti_(4)O_(12) ternary metacomposites with tunable negative permittivity and thermal conductivity fabricated by spark plasma sintering

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Rare Metals 2023年第12期42卷 4201-4211页

作者： Yun-Peng Qu Hai-Kun Wu Pei-Tao Xie Ni Zeng Yan-Li Chen Xiu Gong Jing-Liang Yang Qiong Peng Yu Xie Xiao-Si Qi College of Physics Guizhou UniversityGuiyang 550025China Department of Chemistry City University of Hong KongHong Kong 999077China College of Materials Science and Engineering Qingdao UniversityQingdao 266071China Foshan(Southern China)Institute for New Materials Foshan 528200China Faculty of Science and Engineering Department of MaterialsThe University of ManchesterManchester M139PLUK Department of Mechanical and Electrical Engineering Xiamen UniversityXiamen 361005China

Metacomposites with negative permittivity usually possess huge dielectric loss,showing potential for micro-wave attenuation devices where huge heat would ***,carbon nanotube-carbon black/CaCu_(3-)Ti_(4)O_(12)(CNT-CB/CCTO)ternary metacomposites were fabricated by spark plasma *** CNT-CB dualphase filler was pre-pared through electrostatic selfassembly process in order to construct an effective 3-dimensional(3D)carbon network in CCTO *** percolation threshold of CNT-CB/CCTO composites was identified at filler content of 12.52 wt%which accompanied with an essential change of conduction *** negative permittivity was derived from low-frequency plasmonic state of the 3D carbon network,described by Drude *** problem of heat transport,generally occurring in negative permittivity materials,has been solved and optimized in obtained ternary metacomposites beneftting from the substantially high thermal conductivity(9.49-2.00 W·m^(-1)·K^(-1))and diffusivity(2.74-1.22mm^(2)·s^(-1)).This work could spark significant development of practical application of metacomposites on novel electronic devices and electromagnetic apparatus.

关键词： Metacomposites Ceramic matrix composites Negative permittivity Thermal conductivity

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Deposition of shear-thinning viscoelastic fluids by an elongated bubble in a circular channel regarding the weakly elastic regime

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Droplet 2024年第3期3卷 49-56页

作者： SungGyu Chun Zhengyu Yang Jie Feng Department of Mechanical Science and Engineering University of Illinois Urbana-ChampaignUrbanaIllinoisUSA Materials Research Laboratory University of Illinois Urbana-ChampaignUrbanaIllinoisUSA

Thin-film deposition of fluids is ubiquitous in a wide range of engineering and biological applications,such as surface coating,polymer processing,and biomedical device *** the thin viscous film deposition in Newtonian fluids has been extensively investigated,the deposition dynamics in frequently encountered non-Newtonian com-plex fluids remain elusive,with respect to predictive scaling laws for the film ***,we investigate the deposition of thin films of shear-thinning viscoelastic fluids by the motion of a long bubble translating in a circular capillary *** the weakly elastic regime with a shear-thinning viscosity,we provide a quantitative measurement of the film thickness with systematic *** further harness the recently developed hydrodynamic lubrication theory to quantitatively rationalize our experimental observations considering the effective capillary number Cae and the effective Weissenberg number Wie,which describe the shear-thinning and the vis-coelastic effects on the film formation,*** obtained scaling law agrees reasonably well with the experimentally measured film thickness for all test *** work may potentially advance the fundamental understanding of the thin-film deposi-tion in a confined geometry and provide valuable engineering guidance for processes that incorporate thin-film flows and non-Newtonian fluids.

关键词： film weakly bubble

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