The triboelectric effect, charge transfer during sliding, is well established but the thermodynamic driver is not well understood. We hypothesize here that flexoelectric potential differences induced by inhomogeneous strains at nanoscale asperities drive tribocharge separation. Modeling single asperity elastic contacts suggests that nanoscale flexoelectric potential differences of ±1-10 V or larger arise during indentation and pull-off. This hypothesis agrees with several experimental observations, including bipolar charging during stick slip, inhomogeneous tribocharge patterns, charging between similar materials, and surface charge density measurements.
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http://dx.doi.org/10.1103/PhysRevLett.123.116103 | DOI Listing |
Langmuir
December 2024
Department of Chemistry and Physics of Materials, Paris-Lodron University Salzburg, Jakob-Haringer-Straße 2a, A-5020 Salzburg, Austria.
Chemical transformations at metal oxide interfaces that are triggered by mechanical energy set the basis for applications in the fields of tribo- and mechanochemistry, ceramic and composite processing, and piezoelectric devices. We investigated the early stages of tribochemically initiated radical chemistry of structurally well-defined TiO and BaTiO nanoparticles in argon or in oxygen atmosphere. Electron paramagnetic resonance spectroscopy enabled the determination of the chemical nature and concentration of paramagnetic surface species which form upon uniaxial powder compaction at room temperature.
View Article and Find Full Text PDFACS Appl Mater Interfaces
December 2024
Intelligent Materials Lab, School of Physics and Materials Science, Nanchang University, Nanchang 330031, People's Republic of China.
Interface effects and strain engineering have emerged as critical strategies for modulating polarization and internal electric fields in ferroelectric materials, playing a vital role in exploring coupling mechanisms and developing ferroelectric diode devices. In this study, we selected BiFeO as a representative ferroelectric material and utilized interface engineering to control its polarization. By precisely manipulating the atomic stacking sequence at the interface, we influenced the electrostatic potential step across the interface, resulting in a bias voltage in the ferroelectric hysteresis loops that defined the ferroelectric state.
View Article and Find Full Text PDFSmall Methods
December 2024
Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-sen University, Guangzhou, 510275, China.
2D) Van der Waals ferroelectrics offer the opportunity for developing novel nanoelectronics devices. For device applications, it is necessary to generate controllable ferroelectric polarization domains and achieve non-destructive polarization switching. However, it is very challenging to use the electric field to manipulate the domain state of ultra-thin ferroelectric film due to the large leakage current and even electric breakdown.
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November 2024
Department of Mechanical Engineering and Science, Kyoto University, Kyoto Daigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan.
Exploring complex topological structures in condensed matter has shown promising applications in nanotechnology. Although polar topologies such as chiral vortices and skyrmions have been observed in ferroelectric heterostructures, their existence in simple systems has posed challenges due to the absence of intrinsic noncollinear interaction (like Dzyaloshinskii-Moriya interaction in ferromagnetics). Here, we demonstrate that a nanoindentation mechanically switches local polarizations to stable polar topologies, including skyrmions, within a room-temperature PbTiO thin film via the flexoelectric effect as a noncollinear (Dzyaloshinskii-Moriya-like) driving force using phase-field simulations.
View Article and Find Full Text PDFSmall
December 2024
NanoBioMedical Centre, Adam Mickiewicz University, Wszechnicy Piastowskiej 3, Poznan, 61-614, Poland.
Flexoelectricity, an intrinsic property observed in materials under nonuniform deformation, entails a coupling between polarization and strain gradients. Recent catalyst advancements have reignited interest in flexoelectricity, particularly at the nanoscale, where pronounced strain gradients promote robust flexoelectric effects. This paper comprehensively examines flexoelectricity, encompassing methodologies for precise measurement, elucidating its distinctions from related phenomena, and exploring its potential applications in augmenting catalytic properties.
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