Nanotexture influence of BaTiO3 particles on piezoelectric behaviour of PA 11/BaTiO3 nanocomposites

The piezoelectric activity of a hybrid ferroelectric nanocomposite, i.e. polyamide 11/barium titanate (BT), has been investigated for different loadings of BT particles. The BT volume fraction (/) was ranging from 0.024 to 0.4 with a particle size of 50, 100, 300 and 700 nm. The influence of polarization mode on the piezoelectric behaviour has been studied. The magnitude of the poling field used in this study is in the same order of magnitude of the one used for bulk BT i.e. significantly lower than for piezoelectric polymers. The optimum piezoelectric coefficient is reached when the amorphous phase of the polymeric matrix is in the liquid state i.e. for a polarization temperature higher than the glass transition and for time constant allowing macromolecular mobility. The composite piezoelectric activity decreases for particles size lower than 300 nm due to the loss of the tetragonal phase. The nanotexture of these particles has been investigated by transmission electron microscopy (TEM) and high-resolution TEM. A core shell structure has been observed. An increase of the longitudinal piezoelectric strain coefficient d33 with the raising of BT volume fraction was shown. Contrary to inorganic piezoelectric ceramics, the dielectric permittivity of hybrid composites remains moderate; therefore it allows the piezoelectric voltage coefficient of composites to be higher than ceramics

Dielectric relaxations and ferroelectric behaviour of even–odd polyamide PA 6,9

Thermo Stimulated Current (TSC) combined with Dynamic Dielectric Spectroscopy (DDS) have been applied to the investigation of dielectric relaxation modes of an even–odd Polyamide PA 6,9. The correlation between results obtained by both methods allows us to describe precisely the molecular mobility. At high temperature, the various dielectric relaxation phenomena are separated by applying the dielectric modulus formalism. The comparison between the activation enthalpy values obtained by DDS and TSC leads to the assignment of the so-called α mode to cooperative movements of polymeric sequences. Molecular mobility of PA 6,9 is compared with the one of PA 11. The piezoelectric activity of PA 6,9 is shown and analyzed

Dielectric relaxations in PEEK by combined dynamic dielectric spectroscopy and thermally stimulated current

The molecular dynamics of a quenched poly (ether ether ketone) (PEEK) was studied over a broad frequency range from 10-3 to 106 Hz by combining dynamic dielectric spectroscopy (DDS) and thermo-stimulated current (TSC) analysis. The dielectric relaxation losses e00 KK has been determined from the real part e0 T(x) thanks to Kramers–Kronig transform. In this way, conduction and relaxation processes can be analyzed independently. Two secondary dipolar relaxations, the c and the b modes, corresponding to non-cooperative localized molecular mobility have been pointed out. The main a relaxation appeared close to the glass transition temperature as determined by DSC; it has been attributed to the delocalized cooperative mobility of the free amorphous phase. The relaxation times of dielectric relaxations determined with TSC at low frequency converge with relaxation times extracted from DDS at high frequency. This correlation emphasized continuity of mobility kinetics between vitreous and liquid state. The dielectric spectroscopy exhibits the ac relaxation, near 443 K, which has been associated with the rigid amorphous phase confined by crystallites. This present experiment demonstrates coherence of the dynamics of the PEEK heterogeneous amorphous phase between glassy and liquid state and significantly improve the knowledge of molecular/dynamic structure relationships

A comprehensive investigation of poly(vinylidene fluoride- trifluoroethylene-chlorofluoroethylene) terpolymer nanocomposites with carbon black for electrostrictive applications

cited By 15International audienceA percolative poly(vinylidene fluoride-trifluoroethylene- chlorofluoroethylene)/carbon black nanocomposite was fabricated via a simple solution blending method. The dielectric properties, mechanical properties, and breakdown strength were comprehensively investigated for electrostrictive applications. The nanocomposites exhibit excellent mechanical properties and dielectric properties with a dielectric permittivity of 140 and a low dielectric loss of 0.05 at 100Hz. The significant enhancement of dielectric properties was explained by percolation theory, and a percolation threshold of 4.68wt.% was observed. Breakdown strength results were analyzed by Weibull probability, and the observed inevitable decrease of breakdown strength limits its practical applications. © 2014 AIP Publishing LLC

Scale-like compliant gold electrode: Towards high strain capacitive devices for energy harvesting

cited By 2International audienceHighly compliant electrodes are of primary importance for high strain capacitive energy harvesting. Herein, we present a compliant gold sputtered electrode on a natural rubber substrate. Electrical conductivity remained remarkably good even at strains of 500%. The robustness of the electrodes has been assessed in fatigue tests and resistivity of less than 25 Ω cm -1 were observed after 1500 cycles between 200% and 300% strain. These electrodes were then used in harvesting energy for large strains and experimental energy densities up to 3.3 mJ cm-3 cycle-1 have been recorded, showing the capabilities of such electrodes for efficiently ensuring electrical contact under high strain for converting mechanical energy into electricity. © 2014 Elsevier B.V

Advances in relaxor ferroelectric terpolymer: New applications

International audienc

Advances in relaxor ferroelectric terpolymer: New applications

International audienc

Plasticized relaxor ferroelectric terpolymer: Toward giant electrostriction, high mechanical energy and low electric field actuators

cited By 18International audienceEnhancing the electrostrictive strain under low electric field of a dielectric electroactive polymer (EAP) is essential in soft actuators applications. Conventional electrostrictive polymers suffer of the high electric fields usually required to reach sufficient strain. Here we report a new approach that greatly enhanced the strain under electric field and the mechanical energy density of fluorinated terpolymer EAP. A new all organic composite based on poly(vinylidene fluoride-trifluoroethylene- chlorofluoroethylene) terpolymer (P(VDF-TrFE-CFE)) doped with bis(2-ethylhexyl) phthalate (DEHP) was synthesized. DEHP molecule acts as a plasticizer that leads to large dipolar interfacial effects. This chemical modification allows a 28-fold increase of the electrostrictive strain and a 215-fold increase of the mechanical energy density. As a consequence, this new approach permits the uses of the exceptional properties of the fluorinated terpolymer for an electric field nearly 5 times lower and represents a simple and effective solution to this technological barrier. © 2013 Elsevier B.V. All rights reserved

Converse electrostrictive effect in dielectric polymers

cited By 9International audienceThis paper aims at exposing a physical model for converse dielectric electrostrictive effect using Debye/Langevin formalism through the use of Boltzmann's statistics. The principle of the proposed approach consists of considering the electric field orientability of dipoles within the polymer matrix as a function of the applied strain, allowing the derivation of the polarization or electric displacement as a function of the electric field and strain or stress. The proposed model also permits taking into account the saturation effect that occurs in the polarization and that limits the mechanical to electrical conversion in electrostrictive dielectric polymers. © 2013 Elsevier B.V

Mechanical energy harvesting via a plasticizer-modified electrostrictive polymer

cited By 3International audienceA plasticizer-modified electrostrictive terpolymer with improved electromechanical properties was investigated for mechanical energy harvesting via a pseudo-piezoelectric cycle. Experimental results indicate that the modified terpolymer exhibited improved energy harvesting performances in contrast with the pure terpolymer. A maximum generated short-circuit current of 3.635 μA (much higher than the leakage current) and a power density of 607 μW/cm3 were observed for modified terpolymer. Based on the quadric relationship between the energy conversion efficiency and the DC bias electric field, an energy conversion efficiency as high as 34% and a corresponding electrical power density of 4.31 mW/cm3 could be achieved for the modified terpolymer working at a DC bias electric field of 30 MV/m. © 2016 AIP Publishing LLC