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Tunable Wide-Bandwidth Resonators Based on Layered Gallium Sulfide
摘要： Wide-bandwidth and high-frequency operation are the two desired properties from resonators in a wide range of applications, such as communication devices, energy harvesters, inertial sensors, and electronic components. However, achieving both of these prerequisites along with detectable vibration amplitudes is very challenging. Herein, nano-electromechanical resonators based on layered gallium sulfide (GaS) are demonstrated. These resonators show resonance frequencies in the range of 10–25 MHz under ambient conditions and a bandwidth of hundreds of kilohertz, which can be simply tuned by predetermining the dimensions of the devices. Therefore, this study emphasizes that, in addition to excellent performances in electronic and optoelectronic applications, GaS can also be implemented as a high performance core element in nanoresonator applications.
关键词： electromechanical properties,wide-bandwidth resonators,gallium sulfide,2D materials
更新于2025-09-23 15:23:52
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The role of dipole structure and their interaction on the electromechanical and actuation performance of homogeneous silicone dielectric elastomers
摘要： Grafting polar groups onto elastomer chains has proven to be an effective method to achieve high performance homogenous dielectric elastomers (DE). Up to now, there still lacks an in-depth understanding of the effect of structure and content of these grafted dipoles on the electromechanical properties of the modified DE. In this study, three kinds of polar groups including carboxyl (COOH), hydroxyl (OH), and ester (COOCH3) are grafted onto Polymethylvinylsiloxane (PMVS) by using a photochemical thiol-ene reaction to prepare PMVS-COOH, PMVS-OH and PMVS-COOCH3 DE. Three grafting degrees (15%, 50% and 95%) were prepared for each kind of modified PMVS. Interestingly, although the dipolar moment of COOH is higher than that of OH and COOCH3, at the same grafting degree, the dielectric constant of PMVS-OH is much higher than that of PMVS-COOCH3 and PMVS-COOH. At high grafting degree (50% and 95%), the actuated strain at a specific electric field of PMVS-OH is significantly higher than that of PMVS-COOH and PMVS-COOCH3. The actuated train at a 15 kV/mm sharply increases from 0.2% for PMVS to 9.1% for PMVS-OH with the grafting degree of 95%, higher than that of the commercial silicone DE and the new structured silicone DE reported previously. These dielectric, mechanical and actuated properties are affected by the combined effects of moment, mobility and interactions of these dipoles, which have been deeply discussed. The present study provides guidance for the preparation of high-performance homogeneous DE by rational designing the dipolar structure and content.
关键词： Polymethylvinylsiloxane,dipoles,electromechanical properties,thiol-ene click chemistry,dielectric elastomers,actuated strain
更新于2025-09-23 15:23:52
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A thermodynamic potential for barium zirconate titanate solid solutions
摘要： Barium zirconate titanate [Ba(ZrxTi1?x)O3] solid solutions are promising lead-free ferroelectric materials that have received substantial interest. Thermodynamic analysis based on phenomenological Landau–Devonshire theory is a powerful method for theoretical investigation of ferroelectric materials, but cannot be applied to Ba(ZrxTi1?x)O3 because there is no thermodynamic potential. In this paper, a thermodynamic potential for Ba(ZrxTi1?x)O3 (0 ≤ x ≤ 0.3) solid solutions is constructed, and then a thermodynamic analysis carried out. The results accurately reproduce known phase structures and their transition temperatures, with good agreement with experimentally measured polarization, dielectric, and piezoelectric constants. It is found that Ba(ZrxTi1?x)O3 solid solutions at room temperature have three phase boundaries, including a tetragonal–orthorhombic phase boundary at x = 0.013, an orthorhombic–rhombohedral phase boundary at x = 0.0798, and a rhombohedral–paraelectric phase boundary at x = 0.2135. The results also indicate that the chemical composition-induced ferroelectric–paraelectric phase boundary has superior electromechanical properties, suggesting a new way to enhance electromechanical coupling in Ba(ZrxTi1?x)O3 solid solutions.
关键词： Landau–Devonshire theory,electromechanical properties,solid solutions,lead-free ferroelectric materials,Barium zirconate titanate,phase boundaries,thermodynamic potential
更新于2025-09-23 15:21:21
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3-3 Piezoelectric Metamaterial with Negative and Zero Poisson’s Ratio for Hydrophones Applications
摘要： This study presents the electromechanical properties of the 3-3 piezoelectric metamaterial based on variants of honeycomb (HC) structure. Three kinds of three-dimensional (3D) elastically anisotropic and piezoelectrically active HC structures were introduced, namely, conventional HC (3D-CHC), a re-entrant HC (3D-RE) and a semi-re-entrant HC (3D-SRE). Highly porous 3D finite element models of the mentioned three kinds of metamaterials were developed and the role of ligament orientation on their effective elastic, piezoelectric and dielectric properties was completely characterized. The intrinsic symmetry of HC structure was utilized and simplified mixed boundary conditions equivalent to periodic boundary conditions were recognized. In comparison to their bulk constituent, all the 3-3 type piezoelectric HC networks exhibited an enhanced response, especially for the longitudinal poling. The normalized figures of merit show a mild dependence on the angle θ and the underlying deformation mechanisms associated with the zero, positive and negative Poisson’s ratios. Figures of merit such as hydrostatic strain coefficient (hd), the hydrostatic figure of merit (ghhd) and the acoustic impedance (Z) reached their best values at small angles, i.e., θ=30°. Longitudinally poled networks exhibited four order of magnitude increase in their hydrostatic figure of merit (foam to solid ratio >10,000) and one order of magnitude decrease in the acoustic impedance indicating their applicability for the design of hydrophones.
关键词： piezoelectric materials,auxetic smart structures,metamaterials,electromechanical properties,cellular materials,honey comb structures,unit cell method
更新于2025-09-23 15:19:57
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Enhanced dielectric, electromechanical and hydrophobic behaviors of core-shell AgNWs@SiO2/PDMS composites
摘要： This paper reports a feasible method to prepare polymeric nanocomposites with enhanced dielectric, electromechanical and hydrophobic performance by introducing the core-shell AgNWs@SiO2 filler into polydimethylsiloxane (PDMS). The homogenous core-shell AgNWs@SiO2 was firstly synthesized through a two-step sol-gel process. The thicknesses of AgNWs and SiO2 coating layer are approximately 70 nm and 20 nm, respectively. The dielectric constant is improved effectively due to enhanced interfacial polarization, while extremely low dielectric loss and conductivity are achieved by introducing the insulating SiO2 interlayer to moderate the internal surface area of core-shell nanowires and restrict the electron transfer between Ag nanowires. Typically, the PDMS nanocomposites with 20 wt% AgNWs@SiO2 have a dielectric constant of 6.7, nearly 2.7 times larger than that of pure PDMS, and remains a quite low loss of 0.02 at 1 kHz. Meanwhile, nanocomposites also show improved electromechanical and hydrophoic properties. Nanocomposites with 10 wt% AgNWs@SiO2 exhibit the highest electromechanical sensitivity (β=9.04), about 12.6 times higher than that of pure PDMS at 1 kHz. The static contact angle of nanocomposties with 20 wt% AgNWs@SiO2 reaches 129°. All the improved performances show great potential application for dielectric elastomer material and electrowetting devices.
关键词： Dielectric properties,Electromechanical properties,Core-shell structure,Interfacial polarization
更新于2025-09-10 09:29:36