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Polarization switching in ferroelectric HfO2 from first-principles lattice mode analysis

Physical Review B 2025年第13期111卷 134106-134106页

作者： Yubo Qi Sobhit Singh Karin M. Rabe Department of Physics University of Alabama at Birmingham Birmingham Alabama 35294 USA Department of Mechanical Engineering University of Rochester Rochester New York 14627 USA Materials Science Program University of Rochester Rochester New York 14627 USA Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA

In this paper, we introduce a first-principles-based lattice mode analysis method to investigate the competition between different polarization switching paths in HfO2. Because the stability of the polar orthorhombic Pca21 phase of HfO2 arises from a trilinear coupling, polarization switching requires the flipping of not only the polar Γ15Z mode, but also at least one zone-boundary antipolar mode. This means that each polarization state has multiple variants, leading to multiple possible switching paths connecting up- and down-polarized states, which can be systemically enumerated within this framework for efficient identification of the optimal switching path. Our lattice mode analysis also explains why the activation energy of propagation of the most widely studied domain-wall structure in HfO2, which requires the reversal of the X2− mode, is much larger than that of propagation of domain-wall structures with a uniform sign for the X2− mode. This approach deepens our understanding of distinctive properties of ferroelectric HfO2 related to polarization switching and domain-wall motion, including sluggish domain-wall motion, robust ferroelectricity in thin films, and the observation that the antipolar Pbca phase can hardly be transformed to the ferroelectric Pca21 phase by an electric field. Our mode analysis method can be more generally applied to any improper or hybrid improper ferroelectric, in which polarization switching requires changes of nonpolar distortions, for systematic and efficient prediction of optimal switching paths and estimation of coercive fields.

关键词： Ferroelectricity

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In-situ Environmental TEM Observations of Structural Evolution of Oxygenated Cu(110) in CO

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Microscopy and Microanalysis 2022年第S1期28卷 186-188页

作者： Sun, Xianhu Wang, Jianyu Chen, Xiaobo Ye, Shuonan Liang, Zhilu Yang, Judith C Zhou, Guangwen Department of Mechanical Engineering & Materials Science and Engineering Program State University of New York at Binghamton Binghamton NY USA Department of Chemical and Petroleum Engineering University of Pittsburgh Pittsburgh PA USA

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Preparation of graphitic carbon nitride (g-C3N4) for novel dielectric and photocatalytic dye removal applications

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Physica Scripta 2023年第9期98卷 095904-095904页

作者： Gupta, Aayush Jaidka, Sachin Rajagopalan, Pandey Mehtani, Hitesh Kumar Singhal, Varun Pandey, O.P. Department of Mechanical Engineering GLA University Uttar Pradesh Mathura281406 India School of Physics and Materials Science Thapar Institute of Engineering and Technology Punjab Patiala147004 India Cross College of Elite Program National Cheng Kung University Tainan70101 Taiwan Mechanical Engineering Department Thapar Institute of Engineering and Technology Punjab Patiala147004 India

Recent developments in 2D nanomaterials have greatly expanded their use in engineering applications. Graphitic carbon nitride (g-C3N4) shows a combination of electrical conductivity, sensing and luminescence abilities, biocompatibility, and chemical stability. The present study showcases the effectiveness of g-C3N4 as a photocatalyst for removing various organic molecules from water (such as methylene blue, 4-nitrophenol, and pharmaceutical drugs) and its potential use in dielectric applications when combined with an organic polymer (polyvinylidene fluoride;PVDF). XRD patterns confirmed the formation of g-C3N4 (which is complimented by the UV-Visible and FTIR results) and PVDF-g-C3N4 composite film. SEM-EDS verified the chemical homogeneity of the as-prepared g-C3N4 powder. Maximum photocatalytic degradation was observed for methylene blue dye (96.48%) with a half-life of 24.18 min, whereas the least degradation was detected for hydroxychloroquine (53.10%) with a half-life of 90.12 min after 120 min of UV-visible exposure. 10 wt% C3N4 reinforced PVDF thick films exhibited stable dielectric properties at low temperature (below 60°C) as compared to PVDF alone. At 1 kHz, the dielectric permittivity and tangent loss of the PVDF-g-C3N4 composites come out to be ∼6 and ∼0.05, respectively (at room temperature). The AC conductivity and activation energy of the synthesized composite was also studied. © 2023 IOP Publishing Ltd

关键词： Organic pollutants

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Ultrafast evanescent heat transfer across solid interfaces via hyperbolic phonon-polaritons in hexagonal boron nitride

arXiv

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arXiv 2024年

作者： Hutchins, William Tomko, John A. Hirt, Dan M. Zare, Saman Matson, Joseph R. Diaz-Granados, Katja He, Mingze Pfeifer, Thomas Li, Jiahan Edgar, James Maria, Jon-Paul Caldwell, Joshua D. Hopkins, Patrick E. Department of Mechanical and Aerospace Engineering University of Virginia CharlottesvilleVA22904 United States Interdisciplinary Materials Science Program Vanderbilt University NashvilleTN37212 United States Department of Mechanical Engineering Vanderbilt University NashvilleTN37212 United States Tim Taylor Dept. of Chemical Engineering Kansas State University ManhattanKS United States Department of Materials Science and Engineering Pennsylvania State University University ParkPA16802 United States Department of Materials Science and Engineering University of Virginia CharlottesvilleVA22904 United States Department of Physics University of Virginia CharlottesvilleVA22904 United States

The efficiency of phonon-mediated heat transport is limited by the intrinsic atomistic properties of materials, seemingly providing an upper limit to heat transfer in materials and across their interfaces. The typical speeds of conductive transport, which are inherently limited by the chemical bonds and atomic masses, dictate how quickly heat will move in solids. Given that phonon-polaritons (PhPs), or coupled phonon-photon modes, can propagate at speeds approaching 1% of the speed of light – orders of magnitude faster than transport within a pure diffusive phonon conductor – we demonstrate that volume-confined, hyperbolic phonon-polariton (HPhP) modes supported by many biaxial polar crystals can couple energy across solid-solid interfaces at an order of magnitude higher rates than phonon-phonon conduction alone. Using pump-probe thermoreflectance with a mid-infrared, tunable, probe pulse with sub-picosecond resolution, we demonstrate remote and spectrally selective excitation of the HPhP modes in hexagonal boron nitride (hBN) in response to radiative heating from a thermally emitting gold source. Our work demonstrates a new avenue for interfacial heat transfer based on broadband radiative coupling from a hot spot in a gold film to hBN HPhPs, independent of the broad spectral mismatch between the pump (visible) and probe (mid-IR) pulses employed. This methodology can be used to bypass the intrinsically limiting phonon-phonon conductive pathway, thus providing an alternative means of heat transfer across interfaces. Further, our time-resolved measurements of the temperature changes of the HPhP modes in hBN show that through polaritonic coupling, a material can transfer heat across and away from an interface at rates orders of magnitude faster than diffusive phonon speeds intrinsic to the material, thus demonstrating a pronounced thermal transport enhancement in hBN via phonon-polariton coupling. © 2024, CC BY.

关键词： III-V semiconductors

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Low-symmetry vacancy-related spin qubit in hexagonal boron nitride

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npj Computational materials 2024年第1期10卷 1318-1326页

作者： Rohit Babar Gergely Barcza Anton Pershin Hyoju Park Oscar Bulancea Lindvall GergőThiering Örs Legeza Jamie H.Warner Igor A.Abrikosov Adam Gali Viktor Ivády HUN-REN Wigner Research Centre for Physics PO Box 49H-1525 BudapestHungary MTA-ELTE Lendület“Momentum”NewQubit Research Group Pázmány PéterSétány 1/A1117 BudapestHungary Department of Atomic Physics Insitute of PhysicsBudapest University of Technology and EconomicsMűegyetem rakpart 3.H-1111 BudapestHungary Walker Department of Mechanical Engineering and Materials Graduate Program Texas Materials InstituteThe University of Texas at AustinAustinTX78712USA Department of Physics Chemistry and BiologyLinköping UniversitySE-58183 LinköpingSweden Institute for Advanced Study Technical University of MunichLichtenbergstrasse 2a85748 GarchingGermany MTA-WFK Lendület“Momentum”Semiconductor Nanostructures Research Group PO Box 49H-1525 BudapestHungary Department of Physics of Complex Systems Eötvös Loránd UniversityEgyetem tér 1-3H-1053 BudapestHungary

Point defect qubits in semiconductors have demonstrated their outstanding capabilities for high spatial resolution sensing generating broad multidisciplinary *** boron nitride(hBN)hosting point defect qubits have recently opened up new horizons for quantum sensing by implementing sensing *** sensitivity of point defect sensors in hBN is currently limited by the linewidth of the magnetic resonance signal,which is broadened due to strong hyperfine couplings.

关键词： boron defect hexagonal

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Inverse Design of Nonlinear Mechanics of Bio-inspired materials Through Interface engineering and Bayesian Optimization

arXiv

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arXiv 2024年

作者： Zhang, Wei Tang, Mingjian Mu, Haoxuan Yang, Xingzi Zeng, Xiaowei Tuo, Rui Chen, Wei Gao, Wei J. Mike Walker ′66 Department of Mechanical Engineering Texas A&M University College StationTX77843 United States Department of Mechanical Engineering The University of Texas at San Antonio San AntonioTX78249 United States Department of Industrial & Systems Engineering Texas A&M University College StationTX77843 United States Department of Materials Science & Engineering Texas A&M University College StationTX77843 United States

In many biological materials such as nacre and bone, the material structure consists of hard grains and soft interfaces, with the interfaces playing a significant role in the material’s mechanical behavior. This type of structures has been utilized in the design of various bio-inspired composite materials. Such applications often require the materials to exhibit a specified nonlinear stress-strain relationship. A key challenge lies in identifying appropriate interface properties from an infinite search space to achieve a given target stress-strain curve. This study introduces a Bayesian optimization (BO) framework specifically tailored for the inverse design of interfaces in bio-inspired composites. As a notable advantage, this method is capable of expanding the design space, allowing the discovery of optimal solutions even when the target curve deviates significantly from the initial dataset. Furthermore, our results show that BO can identify distinct interface designs that produce similar target stress-strain responses, yet differ in their deformation and failure mechanisms. These findings highlight the potential of the proposed BO framework to address a wide range of inverse design challenges in nonlinear mechanics problems. © 2024, CC BY.

关键词： Stress-strain curves

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Data-Augmented Modeling for Melt Pool Dimensions in Laser Powder Bed Fusion: A Bayesian Approach

SSRN

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SSRN 2024年

作者： Morcos, Peter Vela, Brent Acemi, Cafer Elwany, Alaa Karaman, Ibrahim Arróyave, Raymundo Department of Materials Science and Engineering Texas A&M University College StationTX United States Department of Industrial and Systems Engineering Texas A&M University College StationTX United States J. Mike Walker’66 Department of Mechanical Engineering Texas A&M University College StationTX77840 United States

The laser powder bed fusion (LPBF) technique has become increasingly prominent in metal additive manufacturing. However, tuning parameters for printing defect-free parts requires labor-intensive experimental work and computationally expensive simulations. Moreover, to calibrate LPBF models against the experimental data, typically MCMC methods or similar methods are used which is also time-consuming. These procedures are viable when calibrating LPBF models against data for individual chemistries but are not efficient for alloy design. A rapid method to calibrate LPBF models is needed to design for printable alloys. We address this challenge by integrating a low-fidelity analytical thermal model, a machine learning model, and proxy experimental data to create an accurate and rapidly-trained model that leverages the principles of Bayesian updating. As a case study in 'printability extrapolation', a dataset of 195 single-tracks on 16 unique chemistries was used to probe the method's ability to predict melt-pool dimensions on `unseen' chemistries. As a case study in 'printability interpolation' the framework was deployed on two compositions that were studied rigorously in the literature for their printability, namely, the ultra-high strength martensitic steel alloy AF9628 and the nickel super alloy 718. The interpolative/extrapolative abilities of the proposed method were compared to a set of 4 control models under data sparse conditions. © 2024, The Authors. All rights reserved.

关键词： Nickel alloys

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Evolution of hierarchical petal-like 3D SnS2 as high-performance electrode materials for supercapacitor applications

Evolution of hierarchical petal-like 3D SnS2 as high-perform...

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作者： Kumar, Niraj Bhusan Sahoo, Bibhuti Chandra Sahu, Krushna Kumar Sahoo, Naresh Naik, Brundabana Soam, Ankur Kumar, Rahul Tripathi, Abhishek Kumar Sahoo, Prasanta Maharashtra Pune411025 India Department of Mechanical Engineering Siksha ‘O’ Anusandhan Deemed to be University Odisha Bhubaneswar751030 India Department of Chemistry Environmental Science and Technology Program Siksha ‘O’ Anusandhan Deemed to be University Odisha Bhubaneswar751030 India Department of Energy Science and Engineering IIT Delhi New Delhi110016 India Department of Metallurgical and Materials Engineering Malaviya National Institute of Technology Jaipur Jaipur302017 India

A simple one-step solvothermal approach has been adopted for the synthesis of SnS2. SEM shows hierarchically SnS2 with petal-like 3-dimensional layer structures because of this process. In this investigation, the as-prepared electrode material have an excellent specific capacitance of 721F g−1 at 1 mVs−1, indicating extraordinary performance. The improved electrochemical performance is because to unique ultrathin petal discrete structure, which provides increased electrolyte/electrode interface, high active sites, rapid ion/electron transfer, and short diffusion distances. A manufactured symmetric solid-state supercapacitor (SSC) device also has a large capacity to operate commercial LEDs, which allows for the assessment of its practical applicability in device-level application. According to the findings of this work, suitably layered 3D SnS2 electrode materials could be a promising route for the development of environmentally friendly energy storage applications. © 2022

关键词： Supercapacitor

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A Soft Robotic Wrist Orthosis Using Textile Pneumatic Actuators For Passive Rehabilitation

A Soft Robotic Wrist Orthosis Using Textile Pneumatic Actuat...

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IEEE International Conference on Soft Robotics (RoboSoft)

作者： Anoush Sepehri Samuel Ward Michael T. Tolley Tania K. Morimoto The Department of Mechanical and Aerospace Engineering University of California San Diego La Jolla CA USA The Departments of Orthopaedic Surgery and the Department of Radiology University of California San Diego La Jolla CA USA The Department of Mechanical and Aerospace Engineering and the Materials Science and Engineering Program University of California San Diego. La Jolla CA USA The Department of Mechanical and Aerospace Engineering and the Department of Surgery University of California San Diego La Jolla CA USA

Wearable soft robots can be effective tools for rehabilitation due to their inherent safety and compliance. Challenges, however, exist regarding the development of suitable on-body actuation methods. Furthermore, the majority of existing soft wearable devices are not accessible and easy to use for those with physical disabilities. This paper presents the design, fabrication, and characterization of a soft robotic wrist orthosis to achieve flexion and extension for continuous passive motion therapy. First, we developed bending textile pneumatic actuators that could be mechanically programmed to conform to the target joint's anatomy when mounted on the body. The textile pneumatic actuators achieved up to 2.24 Nm of torque at 124 kP $a$ . We then embedded the textile pneumatic actuators into a soft wrist orthosis that we designed to ensure it was easy to don/doff without assistance. To determine the operating pressures and range of motion achievable by our soft robotic wrist orthosis, we conducted a device evaluation study with three healthy individuals. Our device achieved over 100 degrees of flexion/extension assistance at operating pressures below 90 kPa. This work takes the first steps towards developing a wearable soft robotic device that can deliver passive therapy at home without the need for a physical therapist or assistant.

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Porous FeAl alloys via powder sintering:Phase transformation,microstructure and aqueous corrosion behavior

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Journal of materials science & Technology 2021年第27期86卷 64-69页

作者： Gang Chen Klaus-Dieter Liss Chao Chen Yuehui He Xuanhui Qu Peng Cao Beijing Advanced Innovation Center for Materials Genome Engineering Institute for Advanced Materials and TechnologyUniversity of Science and Technology BeijingBeijing100083PR China Materials and Engineering Science Program Guangdong Technion-Israel Institute of TechnologyShantouGuangdong515063PR China Technion-Israel Institute of Technology Haifa32000Israel School of Mechanical MaterialsMechatronic and Biomedical EngineeringFaculty of Engineering&Information SciencesUniversity of WollongongWollongongNSW2522Australia State Key Laboratory for Powder Metallurgy Central South UniversityChangsha410083PR China Department of Chemical and Materials Engineering The University of AucklandPrivate Bag 92019Auckland1142New Zealand MacDiarmid Institute of Advanced Materials and Nanotechnology Victoria University of WellingtonPO Box 600Wellington6140New Zealand

This study investigates the phase transformation and microstructure of porous Fe Al parts sintered from elemental powder mixtures using in-situ neutron diffraction and in-situ thermal dilatometry.A single B2 structured Fe Al phase was determined in the sintered Fe Al *** combined effects of the Kirkendall porosity,transient liquid phase,and phase transformations associated with powder sintering all contribute to the swelling phenomenon of the final sintered *** aqueous corrosion test indicates that the corrosion products include iron oxides in the porous Fe Al *** accumulation of corrosion products blocks the pore channel and decreases pore size and permeability over the soaking time.

关键词： Powder sintering Intermetallic Porous Corrosion Neutron diffraction

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