Dielectric capacitors are promising for high power energy storage, but their breakdown strength (Eb) and energy density (Ue) usually degrade rapidly at high temperatures. Adding boron nitride (BN) nanosheets can improve the Eb and high‐temperature endurance but with a limited Ue due to its low dielectric constant. Here, freestanding single‐crystalline BaZr0.2Ti0.8O3 (BZT) membranes with high dielectric constant are fabricated, and introduced into BN doped polyetherimide (PEI) to obtain laminated PEI–BN/BZT/PEI–BN composites. At room temperature, the composite shows a maximum Ue of 17.94 J cm−3 at 730 MV m−1, which is more than two times the pure PEI. Particularly, the composites exhibit excellent dielectric‐temperature stability between 25 and 150 °C. An outstanding Ue = 7.90 J cm−3 is obtained at a relatively large electric field of 650 MV m−1 under 150 °C, which is superior to the most high‐temperature dielectric capacitors reported so far. Phase‐field simulation reveals that the depolarization electric field generated at the BZT/PEI–BN interfaces can effectively reduce carrier mobility, leading to the remarkable enhancement of the Eb and Ue over a wide temperature range. This work provides a promising and scalable route to develop sandwich‐structured composites with prominent energy storage performances for high‐temperature capacitive applications.
Oxide nano-springs have attracted many research interests because of their anti-corrosion, hightemperature tolerance, oxidation resistance, and enhanced-mechanic-response from unique helix structures, enabling various nano-manipulators, nano-motors, nano-switches, sensors, and energy harvesters. However, preparing oxide nano-springs is a challenge for their intrinsic nature of lacking elasticity. Here, we developed an approach for preparing self-assembled, epitaxial, ferroelectric nanosprings with built-in strain due to the lattice mismatch in freestanding La 0.7 Sr 0.3 MnO 3 /BaTiO 3 (LSMO/BTO) bilayer heterostructures. We nd that these LSMO/BTO nano-springs can be extensively pulled or pushed up to their geometry limits back and forth without breaking, exhibiting super-scalability with full recovery capability. The phase-eld simulations reveal that the excellent scalability originates from the continuous ferroelastic domain structures, resulting from twisting under co-existing axial and shear strains. In addition, the oxide hetero-structural springs exhibit strong resilience due to the limited plastic deformation nature and the built-in strain between the bilayers. This discovery provides an alternative way for preparing and operating functional oxide nano-springs that can be applied to various technologies.
Flexible strain sensors have attracted extensive research interest in health monitoring and early diagnosis owing to their superiority in continuous measurement of physiological signals. However, the design of flexible sensors with high sensitivity for subtle strain measurement coupled with biocompatibility, breathability, and eco-friendly properties is still challenging. In this study, a facile and universal approach was developed for the preparation of highly sensitive, biocompatible, and eco-friendly flexible strain sensors in reduced graphene oxide (rGO)/silk composites. The microcrack structures generated in rGO functional layers were achieved by vacuum filtration of GO onto silk nanofibrous matrices followed by a reduction process. The optimized flexible sensor exhibited high sensitivity with a gauge factor (GF) of 436 and 204 at a stretching strain of 8−8.7% and a bending strain of 0.12%, respectively. The sensor also revealed a superfast response of 8.8 ms, excellent durability for over 2000 cycles of bending, and waterproof ability up to 80 °C after 9 cycles. The degradability of the silk substrates enables the recycling of conductive materials, leading to eco-friendly sensor materials. The optimized rGO/silk sensor was able to sensitively and stably detect physiological signals with subtle strain changes (voices, pulse, and airflow), demonstrating great potential for use in flexible strain sensing of human health monitoring and medical diagnostics.
Nanosprings
In article number 2108419, Ziyao Zhou, Houbing Huang, Yong Peng, Ming Liu, and co‐workers report freestanding, epitaxial, ferroelectric nanosprings with superscalability, which provide insights regarding mechanical behaviors and domain evolution of ferroelectric oxide springs. The excellent scalability originates from the continuous ferroelastic domain structures, resulting from twisting under coexisting axial and shear strains. The superstretchable, elastic, and recoverable oxide spring provides a novel platform to flexible electronics.
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