33 research outputs found
P(VDF-HFP)/Cerium composite films with improved dielectric properties for energy storage applications
No full textIn situ synthesis of bismuth oxide nanorods and fabrication of self-poled PVDF nanogenerator for mechanical energy harvesting application
No full textProperties of solutions to some weighted p-Laplacian equation
No full textIn this paper, we prove some qualitative properties for the positive solutions to some degenerate elliptic equation given by-div (w|∇u|p-2∇u) = f(x, u), u ∈ Ap, on smooth domain and for varying nonlinearity f.Peer reviewe
Existence and nonexistence results for anisotropic p-Laplace equation with singular nonlinearities
No full textLet pi≥ 2 and consider the following anisotropic p-Laplace equation −∑Ni=1∂∂xi(∣∣∂u∂xi∣∣pi−2∂u∂xi)=g(x)f(u),u>0 in Ω. Under suitable hypothesis on the weight function g we present an existence result for f(u)=e1u in a bounded smooth domain Ω and nonexistence results for f(u)=−e1u or −(u−δ+u−γ), δ,γ>0 with Ω=RN respectively.Peer reviewe
Enhancement of Electroactive β-phase and Superior Dielectric Properties in Cerium Based Poly(vinylidene fluoride) Composite Films
No full textThe influence of hydrogen bonding on the dielectric constant and the piezoelectric energy harvesting performance of hydrated metal salt mediated PVDF films
No full textPolyvinylidene fluoride (PVDF) films are filled with various mass fractions (wt%) of hydrated metal salt (MgCl2 center dot 6H(2)O) (Mg-salt) to fabricate high performance piezoelectric energy harvesters (PEHs). They deliver up to 4 V of open circuit voltage by simply repeated human finger imparting (under a pressure of similar to 4.45 kPa) and also generate sufficient power to turn on at least ten commercial blue light emitting diodes (LEDs) instantly. The enhanced piezo-response is attributed to the combined effect of the change in the inherent dipole moment of the electroactive phase containing PVDF itself and H-bonding arising between the Mg-salt filler and PVDF via electrostatic interactions. Furthermore, it also successfully charged the capacitors, signifying practical applicability as a piezoelectric based energy harvester power source. UV-visible optical absorption spectral analysis revealed the possibility to estimate a change in the optical band gap value at different concentrations of Mg-salt filler added PVDF films that possess a useful methodology where the Mg-salt can be used as an optical probe. In addition dielectric properties have been studied to understand the role of molecular kinetic and interfacial polarization occurs in H-bond PVDF films at different applied frequencies at room temperature
Enhancement of Electroactive beta-phase and Superior Dielectric Properties in Cerium Based Poly(vinylidene fluoride) Composite Films
No full textIn this work we report on the preparation of poly(vinylidene fluoride) (PVDF) films with various mass fractions (wt%) of hydrated rare earth metal salt (NH4)(4)Ce(SO4)(4)center dot 2H(2)O] (CAS) and its electroactive phase (beta- and gamma-phase) formation. It was found that CAS can yield high amount of electroactive phases in PVDF. Compared to the neat PVDF film, a significantly increment of dielectric constant (epsilon similar to 41) and a low loss factor (tan delta similar to 0.8) were observed in the PVDF-CAS composite films. Thus the PVDF-CAS composite films with high electroactive phase and superior dielectric properties may meet the requirements of next generation electronic components. (C) 2017 Elsevier Ltd. All rights reserved
Halide‐Tunable Bond Engineering for High‐Performance Multi‐Responsive Piezoelectric Sensors via Enhanced Electrostatic Polarization in In Situ Perovskite‐Embedded PVDF Nanofibers
No full textInternational audienceAbstract Developing piezoelectric materials with substantial strain output and large voltage constant, alongside superior piezoelectric performance and mechanical softness remains a long‐standing challenge for promising practical applications. Herein, an in‐situ fabrication strategy is demonstrated to resolve these obstacles by engineering molecular bond angle/length and simultaneously improving electrostatic polarization domain in self‐aligned halide perovskite nanorods (NRs) embedded polyvinylidene fluoride (PVDF) nanofibers (NFs). Introducing large‐size iodine into CsPbBr 3 crystals weakens metal‐halide bonds in CsPbI 2 Br, softening bond strength and enhancing electrostatic polarization in PVDF. The optimized CsPbI 2 Br/PVDF NFs membrane achieves exceptional piezoelectric performance, with a high piezoelectric coefficient ( d 33 ) of 67.5 pC N −1 and a piezoelectric figure of merit of 10.7 × 10 −12 m 2 N −1 , representing 562% and 443% enhancements over the pure PVDF NFs membrane, respectively. Simultaneously, it offers superior mechanical softness, exhibiting a Young's modulus of ≈208 MPa and a strain up to 91.5%. Density functional theory is employed to predict the halide‐tunable latice distortion, which is responsible for the enhanced piezoelectricity. Furthermore, the fabricated sensor demonstrates excellent stability (≈10 000 cycles), detects various mechanical deformations, and powers multiple commercial LEDs through simple daily human activities, highlighting its strong potential as a high‐performance, portable, and wearable energy harvesting device
Weak Harnack inequality for a mixed local and nonlocal parabolic equation
No full textPublisher Copyright: © 2023 The Author(s)This article proves a weak Harnack inequality with a tail term for sign changing supersolutions of a mixed local and nonlocal parabolic equation. Our argument is purely analytic. It is based on energy estimates and the Moser iteration technique. Instead of the parabolic John-Nirenberg lemma, we adopt a lemma of Bombieri-Giusti to the mixed local and nonlocal parabolic case. To this end, we prove an appropriate reverse Hölder inequality and a logarithmic estimate for weak supersolutions.Peer reviewe
Self-Powered Human-Health Monitoring through Aligned PVDF Nanofibers Interfaced Skin-Interactive Piezoelectric Sensor
No full textFlexible
and wearable e-skin sensors are attracting a great interest
for their smart sensing applications in next-generation electronics.
However, implant ability, sensitivity, and biosignal detection capability
in a self-powered manner are the prime concerns in embedded devices.
In particular, electrode compatibility and imperishability have become
challenging issues in wearable sensors due to the poor compatibility
and fragileness of metal electrodes. In this context, we report on
a skin-interactive metal-free spongy electrode in a piezoelectric
sensor where highly aligned poly(vinylidene fluoride) (PVDF) nanofibers
(NFs) arrays are introduced as the piezoelectric active component
and conducting polyaniline- (PANI-) coated PVDF (PANI–PVDF)
NFs mats served as flexible electrodes. Notably, a 99% yield of piezoelectric
phases of the aligned PVDF arrays is the key factor to exhibit promising
mechano-sensitivity (0.8 V/kPa) performance that in turn helps in
human-health monitoring. The sensor shows excellent mechanical to
electrical energy conversion that enable to sense human finger touch
(10 V under 10 kPa) with energy conversion efficiency of 53%. Most
importantly, due to the compatible electrodes excellent mechanical
stability has been found showing negligible degradation over 12,000
periodic cycles. Furthermore, under mechanical stimuli, it is also
possible to charge up a capacitor (1 μF) to 4 V within 60 s
confirming the possibility to use the device as a self-powered piezo-organic-e-skin
sensor (POESS). This type of structural design enables to trace elusive
movement of muscles and the operation in several conditions such as
bending, compression and stretching. We demonstrated various human
gestures monitoring, such as wrist bending, neck stretching, and arm
compressions, throat movements during drinking water, coughing actions,
and swallowing. In addition, diverse specific phonation recognition,
heart-pulse measurement and its respective short-time Fourier transform
(STFT) analysis indicate an efficient and convenient way of monitoring
human-health status particularly in hospital-free mode
