Corona Poling Research Articles

Investigation on in-situ sprayed, annealed and corona poled PVDF-TrFE coatings for guided wave-based structural health monitoring: From crystallization to piezoelectricity

Large-area, lightweight and flexible sensing networks are highly demanded in complex (either in structural topology or material property) structural health monitoring (SHM) applications. Development of piezopolymer offers a feasible solution. In pursuit of maximum exploitation of their functionality, the optimal fabrication technique requires to be investigated first. In this study, PVDF-TrFE coatings were in-situ fabricated and directly functionalized on structural surfaces in the consecutive processing steps as spray, thermal annealing, and corona poling. The processing conditions, including annealing temperature/time and poling voltage/duration, were correlated with their crystallinity, ferroelectric phase, morphology, polarization, and final piezoelectricity, through a systematic study. With the help of various characterization methods, the conditions of optimal functional performance were identified and rationalized. To study the feasibility of thus-prepared functional coatings in transducing guided waves, the host structures with sensors made of such coatings were interrogated by passive acoustic emission and active ultrasonic transmission to validate the sensing and actuation capability, respectively. The developed piezopolymer coatings possess excellent performance as a novel configuration of sensing networks, with lightweight, ultrathin, flexible, rapid-prototyping and adhesive-free features, manifesting high adaptability, high consistency, negligible inter-path interference, and minimal extra penalty for a robust SHM system.

Modification of glass durability in reactive ion etching with thermal poling and ion exchange

The influence of thermal poling and ion exchange on the rate of reactive ion etching of a soda-lime silicate glass in CF4-Ar plasma was studied. It is shown that the replacement of Na+ by Ag+ ions increases the durability of the glass etching while thermal poling of the glass increases the etching rate. The fastest etching was registered for the glasses poled using deposited metal film anodic electrode and using corona discharge in nitrogen atmosphere. Corona poling of the glass in atmospheric air instead of nitrogen essentially decreased the rate.

Ferroelectric behavior in paracrystalline poly(vinyl trifluoroacetate)

Abstract Dielectric behavior in paracrystalline poly(vinyl trifluoroacetate) was investigated from the viewpoint of ferroelectricity. This polymer has a large CF3 dipole moment (2.3 Debye) and structural defects due to the atactic sequence in its chain conformation. It is possible to rotate the dipoles in paracrystals with defects under high electric field. The dielectric behavior was measured from 20 to 200 °C. A large dielectric constant and dielectric relaxation strength (Δε = 17 at 110 °C) were observed in the α-relaxation region. Corona poling on the samples was carried out at DC field 80 MV/m and 80 °C. Ferroelectric D–E hysteresis loop was observed under high electric field, and the remanent polarization and coercive field at 40 °C were 15 mC/m2 and 155 MV/m, respectively. Pyroelectric response and thermally stimulated current were measured from the current through the electrode irradiated by a pulsed semiconductor laser. A pyroelectric constant of about 6 μC/m2K was observed, which was stable up to near the poling temperature. The ferroelectricity in poly(vinyltrifluoroacetate) stems from the rotation of molecular chains in its paracrystals and orientation of the CF2 dipoles. Poly(vinyltrifluoroacetate) dielectrics can be used for capacitors with high power density, artificial skins, muscles and other flexible electronics.

A Piezo Smart‐Braid Harvester and Damper for Multifunctional Fiber Reinforced Polymer Composites

The past decade has seen the rapid development of wearable electronics, wireless sensor networks (WSNs), and self‐powered implantable sensors. However, these devices usually require a continuous source of power supply to operate safely and accurately while having the least reliance on conventional battery systems—due to the recharging/maintenance burdens of batteries. Vibration‐based piezoelectric energy harvesting (PEH) from environment, man‐made machinery, and human body movements seems to be a promising solution. Herein, the first integration of a piezoelectric poly(vinylidene fluoride) (PVDF) yarn‐braid microgenerator into a fiber reinforced polymer composite (FRPC) structure is reported. It is demonstrated that the developed smart composite exhibits multifunctional performances, including simultaneous structural (with ≈10% increased Young's modulus), energy harvesting, and vibration damping (with a damping factor of 125%). The results show that an average output voltage of 3.6 V and a power density of 2.2 mW cm−3 can be achieved at strains below 0.15%, under cyclic loading tests between 1 and 10 Hz. Moreover, noticeable improvements are made in the crystallinity percentage and β‐phase content of as‐received PVDF yarns by, respectively, ≈34% and ≈37%, as a result of the applied coreless radial and axial corona poling techniques.

Rapid apatite induction of polarized hydrophilic HA/PVDF bio-piezoelectric coating on titanium surface

Coatings with piezoelectric characteristics were prepared on the titanium alloy's surface to improve its biological properties, so that the titanium alloy possessed a piezoelectric effect similar to that of bones, thereby promoting bone growth and shortening bone repair time. Compared with other piezoelectric ceramic coatings, PVDF bio-piezoelectric coatings have better piezoelectric properties. However, the PVDF coating is hydrophobic, which is not conducive to calcium deposition. In this study, HA/PVDF coating was obtained on the titanium surface, which indicated a piezoelectric effect. The hydrophilicity of the coating has been improved with the increase of HA content. Corona poling gives the HA/PVDF coating piezoelectric characteristics, and also effectively reduces the contact angle. Moreover, the contact angle of the polarized HA/PVDF coating decreased by 66.9%. The synergistic effect of the introduction of HA and the high piezoelectric coefficient promotes the coating's mineralization. Surprisingly, the poled 20HA/PVDF coating surface was entirely covered by apatite after soaking in simulated body fluids (SBF) for 1 day with physiological loading. Additionally, the coating with rapid apatite deposition ability allows titanium alloy implants to obtain excellent biological activity, which has potential application value in the rapid repair of bone defects.

Ferroelectric membrane for water purification with arsenic as model pollutant

Membrane filtration is widely applied, but often subject to a trade-off between permeability and selectivity, an inherent challenge in membrane processes. Charged membranes are a promising alternative to address this challenge. Here, ferroelectric BaTiO3 nanoparticles, with a spontaneous electric polarization, were assembled into the traditional polyamide nanofiltration membranes by interfacial polymerization then charged by corona poling. Importantly, charges of ferroelectric BaTiO3 nanoparticles sealed in polymers were hardly affected by ambient aqueous environment. The polarized ferroelectric membrane (TFN-mBTO-E) showed higher permeability (2.4 and 1.5 times) and favorable rejection ratio about 97% for arsenic removal, a strictly controlled contaminant, compared with common membranes and unpolarized TFN-mBTO membranes, due to strong hydrophilicity and increased surface potential derived from ferroelectric charges. Thereby, it could provide new insight into charged membrane, laying a foundation for the application of ferroelectric materials in membrane filtration.

New architecture of organo electronic chalcones derivatives: Synthesis, crystal structures and optical properties

A series of four organics conjugate chalcone derivatives [ 1 : (E)-2-(1-(3-oxo-1,3-diphenylprop-1-en-2-yl)pyridin-2(1H)-ylidene)malononitrile, 2 : (E)-2-(1-(3-oxo-3-phenyl-1-(p-tolyl)prop-1-en-2-yl)pyridin-2(1H)-ylidene)malononitrile, 3 : (E)-2-(1-(1-(4-methoxyphenyl)-3-oxo-3-phenylprop-1-en-2-yl)pyridin-2(1H)-ylidene)malononitrile, 4 : (E)-2-(1-(1-(4-chlorophenyl)-3-oxo-3-phenylprop-1-en-2-yl)pyridin-2(1H)-ylidene)malononitrile] were synthesized and structurally characterized by single-crystal X-ray diffraction, 1 H and 13 C NMR, FTIR and UV–Visible spectral analysis. The four studied compounds have the same molecular skeleton and the main difference corresponds to the substitution on the C13 carbon atom of the phenyl ring by a methyl, methoxy and chloride groups for 2 , 3 and 4 respectively. Third harmonic generation (THG) measurements have been performed on thin films at 1064 nm. To perform induced second harmonic generation measurements, the four molecular compounds were reoriented by using the corona poling technique on the films. These measurements highlight that compound 1 exhibits a significant NLO signature compared to the three other compounds. The effects of the substitution on the structural organizations and the optical properties is investigated and discussed. • A series of four organics conjugate chalcone derivatives were synthesized. • Their molecular structures were characterized by single-crystal X-ray diffraction, 1 H and 13 C NMR, FTIR and UV–Visible spectral analysis. • The quadratic and cubic nonlinear optical properties of chalcones derivatives were evaluated. • Three-dimensional intermolecular interactions network is favorable for efficient charge transfer.

Alignment Effect on the Piezoelectric Properties of Ultrathin Cellulose Nanofiber Films.

This study aims at evaluating the piezoelectric property of an ultrathin cellulose nanofiber (CNF) film in a thickness direction. Cellulose is known to have piezoelectric properties. However, its measurement is not easy. By making an ultrathin CNF film and eliminating space charges, the pure piezoelectric property of CNF is intended to be measured. A 600 nm thick ultrathin CNF film was prepared using a microfabrication process. The effect of alignment methods on the piezoelectric property of the ultrathin CNF film in the thickness direction was investigated with the three alignment methods: corona poling, electrical in-plane alignment, and high magnetic field (HiMA) alignment. Piezoresponse force microscopy (PFM) was utilized to analyze the piezoelectric property. By applying AC voltages using PFM, the vertical displacement on the ultrathin CNF film surface was recorded and converted into the piezoelectric coefficient, d33. The aligned ultrathin CNF films show different piezoelectric coefficients. The corona-poled ultrathin CNF film shows the largest piezoelectric coefficient among the three alignment methods. Water contact angle measurement proves that the piezoelectric constant in the thickness direction is associated with hydroxyl groups in cellulose chains appearing on the surface of the ultrathin CNF films.

Flexible Piezoelectric 0–3 PZT-PDMS Thin Film for Tactile Sensing

In this paper, Lead Zirconate-Titanate (PZT)/Poly-dimethylsiloxane (PDMS) based composite is fabricated and characterized for its potential application as a flexible piezoelectric material. Thin films of the composite are prepared by dispersing different volume percentage of PZT particles in cross-linked PDMS matrix. Corona poling of the films is performed to increase the piezoelectric charge constant. X-ray diffraction results indicate that poling aligns the randomly oriented ferroelectric domains in the PZT particles along the poling axis. Piezoelectric voltage response and piezoelectric charge constant values before and after the poling show the improvement in piezoelectricity due to poling. The piezoelectric charge constant, d33 and magnitude of relative permittivity of the films increase and flexibility of the films decrease with the increase of PZT particle volume percentage in the composite. Results show that for 28 v% PZT composite poled film a d33 of 78.33 pC/N was achieved with a Young’s modulus of around 10 MPa and magnitude of relative permittivity of 10. The film demonstrates effectiveness for tactile sensing by generating charges across the film proportional to the finger pressure applied on them. The easy fabrication process makes the composite a promising candidate to build flexible low cost tactile sensing devices.

Polarity effect of corona discharge poling for sol-gel composite-based ultrasonic transducers

Corona discharge was produced in air atmosphere by applying positive and negative high voltage to a needle to investigate the poling effects for two kinds of sol-gel composite materials, Pb(Zr, Ti)O3(PZT)/PZT and Bi4Ti3O12 (BiT)/PZT. Concerning piezoelectric constant d33, only polarity was different. The samples poled by negative corona discharge showed superior temperature durability above certain temperatures even though no significant difference was observed regarding ultrasonic performance characteristics such as center frequency, 6 dB frequency bandwidth. When the pulse voltage supplied by pulser/receiver increased, that difference starting temperature decreased and negative corona poling effect increased. Negative corona discharge poling was effective to improve thermal durability of sol-gel composite ultrasonic transducers when normal pulser/receiver with negative excitation pulse voltage was used for measurements.

Synthesis and Characterization of Carbazole Based Donor-Acceptor-Donor Type Polymer for NLO Applications

Carbazole based NLO polymer was synthesized by using Knoevenagel condensation. The polymer is found to be fully soluble in high polar solvents like dimethyl formamide and dimethylsulphoxide. By using GPC and tetrahydrofuran as a solvent, the molecular weight is found to be 5000 g/mol. Thermal analysis exhibited thermal stability of the polymer up to 400 °C and glass transition temperature (Tg) at 214 °C. The polymer film has good optical transparency. The non-centrosymmetry in the film was induced by corona poling for second order NLO property, whereas z-scan technique is used to understand third order NLO property. The effective TPA coefficient (β) found to be 5.1 X 10−12 m/W. Computational study indicated that the total charge is located at the center of the molecule in HUMO case whereas in the case of LUMO the charge is spreads out from the center of the molecule.

Frequency dependent energy storage and dielectric performance of Ba–Zr Co-doped BiFeO3 loaded PVDF based mechanical energy harvesters: effect of corona poling

Bi0.95Ba0.05Fe0.95Zr0.05O3 (BBFZO) nanoparticles were synthesized by a sol-gel technique to develop a filler material with lower leakage current and oxygen vacancies compared to the host BiFeO3. In this work, we report the enhanced dielectric, ferroelectric, energy storage and energy harvesting performance of BBFZO incorporated PVDF composites. 15 wt% BBFZO loaded PVDF (15BBFZO) exhibited improved polarity (F(EA) = 77.42%) compared to neat PVDF (F(EA) = 37.01%). At an applied field of ∼14 kV cm-1 (1 Hz), this film (15BBFZO) exhibited a maximum energy storage density of 151.18 μJ cm-3 (at 1 Hz). Upon repeated human finger tapping, an average open circuit peak to peak a.c. voltage (VOC) ∼ 20 V was obtained from 15BBFZO. A comprehensive study of frequency dependent D-E loops and an extensive study of the effect of electrical poling on the output performance of the developed composite films have been performed. An improvement of the dipolar polarization was established through a frequency dependent D-E loop study of unpoled and poled 15BBFZO and from other experiments. After poling the energy storage density and VOC of 15BBFZO were 154.66 μJ cm-3 (at 1 Hz) and ∼30 V, respectively. After rectification this output electrical signal was able to charge a 10 μF commercial capacitor up to ∼5.5 V. After poling, the energy storage efficiency (η) of 15BBFZO also improved from 52.49% to 67.85% (at 1 Hz). The frequency dependence of the storage efficiency for all the samples has also been extensively investigated here. At 1 kHz, η improved to 93.30% for poled 15BBFZO.

Use of Flat Ribbon like Electrode Geometry to Pole PVDF Piezoelectrics in Solution Processing

We study how ribbons of fluids subjected to electric fields can serve applications in energy harvesting. In particular the emphasis is on how the geometry (i.e. 2-D ribbons) can influence functionality. For applications related to energy harvesting, we consider the use of polymer Piezo-electric Polyvinylidene Fluoride (PVDF). Corona poling, photo-induced, photo-thermal and electron beam poling are the different conventional techniques used for PVDF poling. The parallel plate capacitor structure made for poling the PVDF material while the PVDF is being cured. One key advantage of preparing PVDF is the ability of solution processing. Normally, the liquid is then spin coated on a substrate and left to dry. Either during the process of spin coating, or after drying - the film of PVDF is poled so as to align the dipoles and make a piezoelectric. We propose the use of a metal-insulator ribbon like electrode geometry to combine the process of fabrication and poling thereby making the process more efficient. On the application of a voltage across the electrodes, the voltage of Vs is developed across the fluid. This result in a field of Vs/d across the PVDF fills aiding the process of poling while the film is in liquid phase. Therefore the ribbon like geometry aids the use of PVDF piezo-electrics in two ways. Firstly, it makes the fabrication process efficient by combining the poling with the structure development. Secondly, the control of width (w) and length (l) aids the setup of the PVDF piezoelectric resonant frequency for a given thickness (d). This helps match the resonant frequency of the ribbon with the incoming low frequency vibration to improve the energy harvesting levels. Piezo-electrics can be used in submerged applications, large area PVDF energy scavengers, mechanical filters and sensors, rural electrification, and charging circuits for hand-held devices.

Fabrication of potassium sodium niobate nano-particle/polymer composites with piezoelectric stability and their application to unsteady wind energy harvesters

We investigated the effects of poling conditions on the piezoelectric performance of potassium sodium niobate [(K,Na)NbO3, KNN]/polymer composites, to obtain their unsteady energy harvesting potential. KNN nanoparticle/polymer composites were designed and fabricated and the poling condition test was performed. The composites were polarized using the corona poling method for various poling conditions and then the piezoelectric coefficient d33 was measured. It was found that piezoelectricity does not decrease over days. Scanning electron microscopic observations were conducted to study the distribution of the nanoparticles in the matrix. Meanwhile, the microstructure of the composites was studied by X-ray diffraction. Unsteady wind energy harvesting tests were accomplished to investigate the output voltage characteristics in the KNN nanoparticle/polymer composites in unsteady winds. The study represents an important step in developing flexible energy harvesters with stable performance.

Surface potential uniformity and sensitivity of large-area PTFE electret discs of different thicknesses produced by a modified corona poling rotating system for dosimetry applications

In this study, large-area (6-cm diameter) Teflon polytetrafluoroethylene (PTFE) discs of different thicknesses (0.2-, 0.5- and 1 -mm) were negatively and positively charged by using the “modified single point-to-plane corona poling rotating system”. The effects of some crucial parameters of the PTFE disc as well as the modified corona poling rotating system on the PTFE surface potential uniformity such as: (a) PTFE disc thickness, (b) PTFE disc polarity and (c) needle-to-PTFE disc distance were successfully reported. Accordingly, closer needle-to-PTFE disc distance, positive charging mode and thinner PTFE disc provided a better PTFE surface potential uniformity. However, the effects of PTFE charge polarity and needle distance on the electrostatic charge potential uniformity were much more remarkable in comparison with the effects of PTFE thickness. Additionally, the surface potential distribution profiles of charged PTFE discs were totally flat and independent of the PTFE thickness at 5- and 13-[Formula: see text]mm needle distances for the negative and positive charging modes, respectively. At the optimized charging conditions, large-area PTFE electret disc (0.5-mm-thick) with positive uniform surface charge potential especially at the edges up to [Formula: see text] 1.8[Formula: see text]kV with stability up to 77 days studied was produced by applying a new multiple heat treatment protocol to the PTFE disc for radon dosimetry. As also observed in this study, the sensitivity of PTFE electret dosimeters to a defined radon gas concentration increases as the PTFE thickness increases. Meanwhile, 0.5-mm-thick PTFE electret disc produced was selected to be used as a high quality electret dosimeter with acceptable and superior parameters for different applications in particular medium-term radiation dosimetry in both low and high dose rate ionizing radiation fields.

Smart Piezoelectric Nanohybrid of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Barium Titanate for Stimulated Cartilage Regeneration.

Piezoelectric materials strive to articulate smart materials and transduce electric fields by applying mechanical pressure and vice versa. This study demarcates augmented cartilage regeneration from the praxis of the smart material intervention that denotes the method of the utilized piezoelectric mechanism. The smart piezoelectric nanohybrid is developed from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and barium titanate (BaTiO3). Further, the electrospinning technique is adopted for the scaffolding to mimic the structure of natural cartilage. The scaffold with 20% BaTiO3 shows enhanced mechanical properties and a piezoelectric coefficient (1.4 pC/N) similar to native tissue. Interestingly, the corona poled (electrically polarized) scaffolds demonstrated better cellular activity than unpoled. Human mesenchymal stem-cell-derived chondrocytes are utilized for in vitro studies. The polarized scaffolds highly promote the cell attachment, proliferation, and collagen II gene expression against control (pure PHBV) and unpolarised scaffolds; the effect was quite dominant even in high-piezoelectric-coefficient scaffolds. Therefore, the electric-field-originated scaffolds show the potential effect on cartilage regeneration without the addition of any stimulating molecules.

Effect of Ce on piezo/photocatalytic effects of Ba0.9Ca0.1CexTi1-xO3 ceramics for dye/pharmaceutical waste water treatment

Ba0.9Ca0.1CexTi1-xO3 (x = 0, 0.1, 0.12 and 0.15) ferroelectric ceramics were fabricated via conventional solid-state reaction route. Ba0.9Ca0.1CexTi1-xO3 (BCT-Ce) powder was poled using corona poling. Systematic investigation was carried out for microstructural, photocatalytic and piezocatalysis performance of various compositions of poled and unpoled Ba0.9Ca0.1CexTi1-xO3 ceramics. To assess catalytic activities, rhodamine B (RB) dye, methylene blue (MB) dye and diclofenac (pharmaceutical compounds) were degraded from water under ultrasonication (piezocatalysis) and using 420 nm light (photocatalysis). Photocatalytic activities were improved by almost 100% in poled samples (as compare to the that of observed from unpoled samples) of all the compositions understudy. Incorporation of Ce in Ba0.9Ca0.1TiO3 (BCT) induces photocatalytic activity in visible region along with enhancement in piezocatalytic performance.

Ultraviolet light effect on characteristics of PbZrxTi1-xO3 (PZT) film during poling process

Poling process is one of the widely used strategies to enhance the film properties during the manufacturing processes of ceramic film. A lab-made PbZrxTi1-xO3 (PZT) film by spin-coating on Ti substrate is presented. After heating treatments, the fabricated film was passed corona poling under ultraviolent (UV) light of various power. The characteristics of the PZT film have been evaluated by several instruments, such as X-ray diffractometer (XRD), scanning electron microscopy (SEM) and impedance analyzer. The results indicated that UV light would affect the orientation of crystallization, microstructure and grain size of PZT film surface during poling process under room temperature.

Improvement of the magneto-electric effect of composites loaded with different magnetic particles for current sensor applications

This article proposes a methodology to improve the magneto-electric effect of a poly(vinylidene fluoride-co-trifluoroethylene) P(VDF-TrFe) copolymer, doped with nanoparticles of nickel (Ni) and nickel iron (NiFe). The preparation of the composite films were achieved through the solvent casting approach. First, P(VDF-TrFe) powders and (Ni and NiFe) nanoparticles are dispersed in dimethyl formamide (DMF) as a solvent to form a homogeneous solution. Then, the solution obtained is deposited on a flexible substrate by a spin coating process. After that, the NiFe doped composites are corona polarized, to improve the magneto-electric response of these composites. The purpose of this work is to investigate the influence of the magnetic charges added in the P(VDF-TrFe) copolymer, and to reveal the effect of corona charging (polarization) on the magneto-electric behavior of the used composites. The obtained results in this article show that both the doping and the electric polarization (piezo coefficient) significantly affect the generated alternating current during the application of an alternating magnetic field. However, the magneto-electric response of composites increases by doping and charging via corona poling effect and also by increasing the excitation frequency and the magnetic field amplitude. In addition, the magneto-electric responses of all composites after corona polarization were also discussed. This indicates that the magneto-electric coefficient and the current can be increased with polarized composites. A good response is observed for P(VDF-TrFe) + 3% Ni with a piezoelectric coefficient d33 = 21.2 (pC/N)

Substituent engineering of electrooptic chromophores to suppress their aggregation

Chromophores composed of 4-cyano-5-dicyanomethylene-2-oxo-3-pyrroline (CDCOP) and a donor have been synthsized for electrooptic applications. Three substituents of [5-(4-aminophenyl)-2-thienyl]-substituted CDCOP 1 and (4-aminophenyl)-substituted CDCOP 2 were modified to suppress the aggregation for effective poling. To 1, bulky and branched 2-ethylhexyl groups were introduced instead of linear alkyl groups. Less aggregation was confirmed in the polymer dispersion films, and the corona poling behaviors were examined. To 2, we introduced norbornyl epoxide groups as bulky and thermally crosslinkable moieties. The aggregation was suppressed as well, and the thermal crosslinking of the epoxide with acid anhydride in the presence of a base was investigated.