Piezoelectric Properties Of Poly Research Articles

Ytterbium-doping effect on the electrochemical and piezoelectric properties of poly(vinylidene fluoride) films

The optimal molar ratio of poly(vinylidene fluoride) (PVDF): dimethyl sulfoxide (DMSO) was investigated that promoted the β-phase formation, used during the PVDF film synthesis. The solution cast method was used for doping the PVDF films with ytterbium (III) nitrate salt hexahydrate. In general, Yb-doping in PVDF films improves thermal resistance, promotes β-phase formation, modifies the monomer conformation, reduces reversibility to electrochemical processes, and increases the d33 coefficient of piezoelectricity. The β-phase formation caused by Yb-doping alters the internal structures of the trans-gauche-trans-gauche’ (TGTG’) and all-trans (TTTT) chains inside the polymeric network. The coexistence between the trans-gauche and all-trans structures provides in both films the α-phase and β-phase coexistence. The presence of self-polarized CH2-CF2 dipoles, where the concentration of fluorine remains the same and the CH2 drastically increases after Yb3+ incorporation. The quasi-reversible shape shown in both voltammetry cyclic curves is related to irreversible oxidation and reduction reactions. Yb-PVDF exhibits specific pseudocapacitance values that are 30% higher than those of the PVDF films. Finally, the piezoelectric properties were improved with ytterbium incorporation.

Hydrophilic Carbon Quantum Dots Assisting Porous P(VDF-HFP) film for Self-powered Humidity Sensing with High Sensitivity and Low Hysteresis

The self-powered has become the development trend of electronic devices in the "double carbon" era. However, environmental humidity has a significant impact on the piezoelectric properties of poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP))...

Review of Piezoelectric Properties and Power Output of PVDF and Copolymer-Based Piezoelectric Nanogenerators.

The highest energy conversion efficiencies are typically shown by lead-containing piezoelectric materials, but the harmful environmental impacts of lead and its toxicity limit future use. At the bulk scale, lead-based piezoelectric materials have significantly higher piezoelectric properties when compared to lead-free piezoelectric materials. However, at the nanoscale, the piezoelectric properties of lead-free piezoelectric material can be significantly larger than the bulk scale. The piezoelectric properties of Poly(vinylidene fluoride) (PVDF) and Poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) lead-free piezoelectric nanomaterials are reviewed and their suitability for use in piezoelectric nanogenerators (PENGs) is determined. The impact of different PVDF/PVDF-TrFE composite structures on power output is explained. Strategies to improve the power output are given. Overall, this review finds that PVDF/PVDF-TrFE can have significantly increased piezoelectric properties at the nanoscale. However, these values are still lower than lead-free ceramics at the nanoscale. If the sole goal in developing a lead-free PENG is to maximize output power, lead-free ceramics at the nanoscale should be considered. However, lead-free ceramics are brittle, and thus encapsulation of lead-free ceramics in PVDF is a way to increase the flexibility of these PENGs. PVDF/PVDF-TrFE offers the advantage of being nontoxic and biocompatible, which is useful for many applications.

The Micro-Capacitance Enhancement of Polyionic Liquids Grafted Onto Carbon Nanotubes on the Piezoelectric Properties of Poly(Vinylidene Fluoride) Films and Their Sensor Applications

The increased micro-capacitance of a poly (vinylidene fluoride) (PVDF) matrix can effectively improve the piezoelectric properties of the composite material. This work used chemically modified carbon nanotubes (CNTs) as the main reinforcement material. Atom transfer radical polymerization (ATRP) was used to graft polyionic liquids (PILs) with different hydrophilic anions to the CNTs’ surfaces. Solution casting and compressive melt molding were used to prepare the PVDF-composite piezoelectric films. Micro-capacitance formed by the PIL grafted CNTs dispersed well in the PVDF matrix, and their effects on the crystalline form and piezoelectric properties were studied. The hydrophobic hexafluorophosphate anion (-PF6 -) can significantly improve the CNTs dispersion and enhance the micro-capacitance formation in the PVDF matrix. During solution crystallization, the synergistic effect of CNTs and PIL on the PVDF and the solvent effect made the content of β phase of PVDF/CNTs@PIL-PF6 film reach 80.2%, resulting in a high dielectric constant of 188 and a piezoelectric coefficient of 36. In the process of melt crystallization, due to shear stretching and extrusion, the CNTs@PIL-PF6 had an obvious nucleation effect on the polar crystalline phase of PVDF, with a β phase content up to 99.3%, leading to the higher dielectric constant of 530 and the piezoelectric coefficient of 31. The current discovery provides a development direction for smart piezoelectric polymer matrix composites, which have great potential in preparing piezoelectric energy storage materials.

Cell Behavior Changes and Enzymatic Biodegradation of Hybrid Electrospun Poly(3-hydroxybutyrate)-Based Scaffolds with an Enhanced Piezoresponse after the Addition of Reduced Graphene Oxide.

This is the first comprehensive study of the impact of biodegradation on the structure, surface potential, mechanical and piezoelectric properties of poly(3-hydroxybutyrate) (PHB) scaffolds supplemented with reduced graphene oxide (rGO) as well as cell behavior under static and dynamic mechanical conditions. There is no effect of the rGO addition up to 1.0 wt% on the rate of enzymatic biodegradation of PHB scaffolds for 30 d. The biodegradation of scaffolds leads to the depolymerization of the amorphous phase, resulting in an increase in the degree of crystallinity. Because of more regular dipole order in the crystalline phase, surface potential of all fibers increases after the biodegradation, with a maximum (361 ± 5mV) after the addition of 1 wt% rGO into PHB as compared to pristine PHB fibers. By contrast, PHB-0.7rGO fibers manifest the strongest effective vertical (0.59 ± 0.03 pm V-1 ) and lateral (1.06 ± 0.02 pm V-1 ) piezoresponse owing to a greater presence of electroactive β-phase. In vitro assays involving primary human fibroblasts reveal equal biocompatibility and faster cell proliferation on PHB-0.7rGO scaffolds compared to pure PHB and nonpiezoelectric polycaprolactone scaffolds. Thus, the developed biodegradable PHB-rGO scaffolds with enhanced piezoresponse are promising for tissue-engineering applications.

A comprehensive investigation on the influence of processing techniques on the morphology, structure, dielectric and piezoelectric properties of poly (vinylidene fluoride)/Graphene oxide nanocomposites

Graphene Oxide (GO) incorporated poly (vinylidene fluoride) (PVDF) nanocomposites were fabricated by employing two processing methodologies viz. solution casting and compression moulding. ‘Ultrasonication’ followed by ‘centrifugation’ was adopted to obtain a finer dispersion of GO in the PVDF matrix. Subsequently, the effect of different processing techniques on the morphology, crystalline structure, dielectric and piezoelectric properties of PVDF/GO nanocomposites were investigated. Solution casted PVDF/GO nanocomposite of 0.15 wt% GO has resulted in ∼86% of the polar phase. Further, solution casted PVDF/GO nanocomposite of 0.15 wt% GO exhibited d33 value of ∼59 p.m./V, which was significantly higher as compared to the corresponding compression moulded nanocomposite. Finally, sensor devices were fabricated based on solution casted PVDF/GO nanocomposite film, which showed a peak-to-peak voltage of ∼10.2 V at 0.08 wt% GO. A systemic comparison and interrelation has been simultaneously established with respect to processing, structure and property of PVDF/GO nanocomposites.

Poly(vinylidene fluoride‐co‐trifluoroethylene) Thin Films after Dip‐ and Spin‐Coating

AbstractThe ferro‐, pyro‐ and piezoelectric properties of poly(vinylidene fluoride‐co‐trifluoroethylene) P(VDF‐TrFE) have created interest with regard to its application in aqueous and ambient surroundings for sensors, functional coatings, and in the field of life sciences. P(VDF‐TrFE) thin films are usually applied via spin‐coating, but dip‐coating will be advantageous especially for irregularly shaped substrates. The morphology of dip‐ and spin‐coated semi‐crystalline thin films is studied as a function of both the film thickness and the annealing temperature. The characterization of the films is carried out by grazing incidence wide‐angle X‐ray scattering (GIWAXS), X‐ray reflectometry (XRR), and infrared reflection absorption spectroscopy (IRRAS). Atomic force microscopy measurements (AFM) are used to examine the resulting topography. It is found that both spin‐ and dip‐coated thin films crystallize in the desired edge‐on orientation, but the overall crystallinity after dip‐coating is decreased compared to the spin‐coated films of comparable thickness and the resulting roughness is increased. The higher roughness is most probably caused by the slower evaporation of the solvents and a secondary crystallization process at the air‐polymer interface.

Rational design of PVDF/BaTiO3 nanoparticle/Cu nanowire ternary nanocomposite films for optimal piezoelectric power generation

Flexible polymers, ferroelectric ceramic nanoparticles, and conductive nanomaterials have been intensively studied with the aim of exploiting their unique properties synergistically and producing a ternary composite displaying excellent piezoelectric performance. Therefore, it is important to understand the role of conductive nanomaterials in ternary nanocomposites for piezoelectric power generation. In this study, the effect of Cu nanowire (CuNW) addition on the dielectric, ferroelectric, and piezoelectric properties of poly(vinylidene fluoride) (PVDF)/BaTiO3 nanoparticle (BTNP)/CuNW composite films was systematically investigated. The experimental results reveal that ternary composites with 0.04 vol. % CuNWs generated the highest total charge and power density among samples of varying CuNW content. When 0.04 vol. % CuNWs were incorporated into the PVDF/BTNP binary composite, the remanent polarization (Pr) increased from 0.51 to 1.63μC/cm2 due to an enhanced effective electric field. However, when the CuNW content exceeded 0.04 vol. %, Pr started to decrease owing to an increase in the leakage current and the enhancement in the pinning effect of the PVDF dipoles. When an excessive amount of CuNWs was added to the composite, the piezoelectric performance showed only a moderate decrease owing to the enhanced stress transfer. Conductive nanowires are often incorporated into piezoelectric ternary composites to facilitate the dispersion of piezoelectric nanoparticles and for stress transfer. However, composites with a more than 0.04 vol. % CuNWs have a lower net polarization and piezoelectric power density. When the CuNW content is optimized (0.04 vol. %), the maximum power density of the ternary composite film can be enhanced by up to 520%.

Zinc Oxide Nanoparticles Coated with (3-Aminopropyl)triethoxysilane as Additives for Boosting the Dielectric, Ferroelectric, and Piezoelectric Properties of Poly(vinylidene fluoride) Films for Energy Harvesting

In this study, we report the synergistic role of (3-aminopropyl)triethoxysilane (APTES) functionalization of zinc oxide (ZnO) nanoparticles and low-temperature phase-inversion for boosting the pola...

A mixed solvent approach to make poly(vinylidene fluoride) nanofibers with high β-phase using solution blow spinning

The excellent mechanical and piezoelectric properties of poly(vinylidene fluoride) (PVDF) are its most valuable characteristics, and improving the piezoelectric performance of PVDF is an important subject of the study. However, several existing methodological studies have been regarded as complex and ineffective. The most efficient method to produce PVDF nanofibers with high β-phase contents is still electrospinning; however, this process does not facilitate the mass production of PVDF nanofibers and produces PVDF with a relatively low fraction of β-phase. Both these issues can be solved by solution blow spinning (SBS). This work focused on the optimum ratio of solvents to produce beadless PVDF nanofibers and highlighted the relationship between the spinning solution viscosity and the average diameter of the SBS nanofibers obtained. Using Fourier transform infrared reflection, it was evaluated that the fraction of the β-phase increased after the SBS process, which was calculated to be 85%; this value was considered as a relatively high fraction of β-phase, which was similar to that obtained by electrospinning. Consequently, a simple and convenient alternative to produce PVDF nanofibers with high β-phase contents was achieved.

A printable P(VDF-TrFE)-PZT Composite with Very High Piezoelectric Coefficient

In this paper a significant advance in the piezoelectric properties of poly(vinylidenefluoride-trifluoroethylene)-lead zirconate titanate (P(VDF-TrFE)-PZT) composite ink has been achieved by coating the ceramic particles prior to formulation with a polymeric surfactant containing carboxylic acid anhydride functional groups and the piezoelectric response of a unimorph cantilever is further enhanced by introducing a reinforced substrate. The measured effective transverse piezoelectric coefficient (d31eff) was -56 pm/V, which is 3.3 times higher than that of the same composite without surfactant and is the highest reported for a printable polymer-ceramic composite. In addition, the printability of the ink and dispersion of the ceramic particles was enhanced. The samples were fabricated by stencil printing of a single piezoelectric layer on a flexible PET substrate followed by curing at only 120°C, thus enabling utilization on a wide range of substrates. The results also show the improved particle dispersion and layer quality in 0-3 composite inks with surfactant added and the effect of sample structure and mechanical coupling between the hard ceramic particles and the soft matrix. The developed composite ink is suitable, for example, in sensors in printed wearable and portable electronics.

On the Nanoscale Mapping of the Mechanical and Piezoelectric Properties of Poly (L-Lactic Acid) Electrospun Nanofibers

The effect of the post-annealing process on different properties of poly (L-lactic acid) (PLLA) nanofibers has been investigated in view of their use in energy-harvesting devices. Polymeric PLLA nanofibers were prepared by using electrospinning and then were thermally treated above their glass transition. A detailed comparison between as-spun (amorphous) and annealed (semi-crystalline) samples was performed in terms of the crystallinity, morphology and mechanical as well as piezoelectric properties using a multi-technique approach combining DSC, XRD, FTIR, and AFM measurements. A significant increase in the crystallinity of PLLA nanofibers has been observed after the post-annealing process, together with a major improvement of the mechanical and piezoelectric properties.

Mechanical and piezoelectric characterizations of electrospun PVDF-nanosilica fibrous scaffolds for biomedical applications

The effects of hydrophilic and hydrophobic nanosilica (SiO2) on the morphology, mean diameter distribution of fibers, mechanical and piezoelectric properties of poly (vinylidene fluoride) (PVDF) nanofibers were studies. We prepared Nanofibers by the electrospinning of PVDF solutions containing 1.5 wt.% both hydrophilic and hydrophobic nano-SiO2 loadings. Morphology and diameter distribution of the electrospun nanofibers were studied using field emission scanning electron microscopy (FE-SEM) analysis. Tensile test was used to study the effect of both types of nanosilica on the tensile strength, young’s modulus and strain at break. Piezoelectric characterization of the electrospun fibers were determined using calculation of the output voltages under certain loading force. Results showed that the fibers diameter and mechanical properties of the nanofibers increase in presence of hydrophilic SiO2 nanoparticles. Furthermore, the output voltages of the electrospun fibers demonstrated that both types of silica could considerably amplify electroactive properties of PVDF fibers. However, the results for PVDF fibers containing the hydrophilic silica nanoparticle were more highlighted.

Investigation of the Effect of Nanosilica on Rheological, Thermal, Mechanical, Structural, and Piezoelectric Properties of Poly(vinylidene fluoride) Nanofibers Fabricated Using an Electrospinning Technique

The effects of different nano-SiO2 contents on the rheological properties of poly(vinylidene fluoride) (PVDF) solution and mechanical, thermal, structural, and piezoelectric properties of composite nanofibers were investigated. Results showed an increase in fiber diameter (∼125 to 350 nm) and ∼450% increase in tensile strength as the content of nano-SiO2 particles increased. The degree of crystallinity decreased by 19% as the nano-SiO2 content increased by 2% (w/w). Further investigation demonstrated that silica could significantly improve the piezoelectric properties of PVDF nanofibers as the output voltage showed an increase in the presence of silica attributed to change in the crystalline structure of PVDF.

Ferroelectric and piezoelectric properties of poly(vinylidene fluoride–trifluoroethylene) gels

The structural, ferroelectric, and piezoelectric properties of poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] gels fabricated using poly(pyridinium-1,4-diyliminocarbonyl-1,4-phenylenemethylene thiocyanate) (PICPM-SCN) as a gelator are investigated in this study. The P(VDF–TrFE)/PICPM-SCN composites formed thermally reversible physical gels and their analysis by Fourier transform infrared spectroscopy revealed that the P(VDF–TrFE) molecules in these gels exhibit predominantly the ferroelectric phase I (Form β). Furthermore, the polarization switching peaks of the P(VDF–TrFE)/PICPM-SCN gel films were clearly observed. The coercive electric field for these gel films was estimated to be 2 MV/m, which is dramatically lower than the values typically observed for P(VDF–TrFE) solid films (50 MV/m). Finally, the P(VDF–TrFE)/PICPM-SCN gel films exhibited a piezoelectric response, and the highest piezoelectric coefficient was determined to be ∼53 pm/V at an applied voltage frequency of 4 kHz.

Effect of ultrasonication and other processing conditions on the morphology, thermomechanical, and piezoelectric properties of poly(vinylidene difluoride-trifluoroethylene) copolymer films

This study is carried out on the effect of processing conditions including preparation methods, ultrasonication, film thickness, and thermal annealing on the thermal, mechanical, and piezoelectric properties of copolymer of poly(vinylidene difluoride-trifluoroethylene) (P(VDF-TrFE)). Free-standing films and films on substrates are prepared by solvent casting and spin-coating, respectively. The results obtained by differential scanning calorimetry show that the Curie transition of the copolymer films was influenced by the preparation methods, with very little difference in the melting transition. The difference was attributed to a less uniform distribution of TrFE comonomer units within the crystalline and amorphous regions of the spin-coating films. However, no effect of the preparation methods on the piezoelectric properties of the films was observed. It is also found that the short ultrasonication, film thickness higher than critical value of crystallization of P(VDF-TrFE) (about 100 nm), and drying before annealing did not have a significant effect on the properties of the films. Surprisingly, the ultrasonication had a clear impact on the relaxations at high temperature of the polymer chains. In addition, this study indicates that a short annealing by 10 min at 140°C was enough to obtain well-crystallized films, which is interesting from the industrial point of view. POLYM. ENG. SCI., 54:1280–1288, 2014. © 2013 Society of Plastics Engineers

Effect of electric field on the structure and piezoelectric properties of poly(vinylidene fluoride) studied by density functional theory

The geometry and piezoelectric properties of chain in PVDF under different electric fields are studied by density functional theory (DFT). The simulation gives optimized geometry of PVDF of α chain and β chain, with rotation angle around ±50° and arbitrary angle between 175° and 185° respectively. The energy barrier is about 16.16 kJ/mol in the chain transition from α chain to β chain, and the one of reverse transition is about 6.24 kJ/mol. The positive electric decreases the energies of α chain and β chain. There would be a critical positive electric field inducing the transition from α chain to β chain. Positive electric field increases dipole moment of the β chain and has few effects on mean molecular polarizibility. It is found that the change of geometry increases dipole moment and the change of electronic properties decrease dipole moment under positive electric field and the geometry plays an important role.

Piezoelectric properties of poly(vinylidene fluoride) and carbon nanotube blends: β-phase development

In order to get poly(vinylidene fluoride) (PVDF) films containing high beta-phase content, multiwalled carbon nanotubes (MWCNTs) were blended with PVDF. For drawn samples, the content of piezoelectric beta-form crystal was increased with MWCNT addition due to the rapid crystallization rate offered by the nucleating action of MWCNT, but soon reached a plateau. Poling on the drawn samples helps additional beta-phase formation when the added MWCNT content was less than 0.2 wt%; at this MWCNT amount, almost pure beta-phase crystal was obtained. More MWCNT addition induced depolarization to reduce the beta-phase content. Undrawn samples show monotonous increase of beta-phase content with MWCNT amount when subjected to poling.

Influence of extrusion, stretching and poling on the structural and piezoelectric properties of poly (vinylidene fluoride‐hexafluoropropylene) copolymer films

AbstractThree types of poly (vinylidene fluoride‐hexafluoropropylene) (PVDF–HFP) copolymer films were prepared by extrusion, stretching as well as simultaneously stretching and static electric field poling (SSSEP), respectively, and measured by the differential scanning calorimetric, wide angle X‐ray diffraction, fourier transformation infrared‐attenuated total reflection, and Dynamic mechanical analysis. The experimental results showed that the films prepared by stretching and SSSEP have higher crystallinity and β phase than by extrusion. SSSEP improved the chain orientation enormously both in crystalline and amorphous regions, resulting in the highest storage modulus. Because of the lower β phase content, the extruded films exhibited the lowest piezoelectric coefficient d33. For the stretched and SSSEP films, although the β phase content was similar, the d33 was distinct because of the different potential energy for the rotation of the dipoles. In addition, the SSSEP films gave the maximum d33 (24 pC/N), higher than the other PVDF–HFP copolymer films that have been reported. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 858–862, 2007

Structure and piezoelectric properties of poly(vinylidene fluoride) studied by density functional theory

Abstract The internal rotation, geometry, energy, vibrational spectra, dipole moments and molecular polarizabilities of poly(vinylidene fluoride) (PVDF) of α- and β-chain models were studied by density functional theory at B3PW91/6-31G(d) level. The effects of chain lengths and monomer inversion defects on the electric properties and vibrational spectra were examined. The results show that the tgtg′ conformation angle between g and g′ is about 55° and the ttt conformation is a slightly distorted all-trans alternating planar zigzag with ±175° repeating motif. The average distance between adjacent monomer units in the β-PVDF is 2.567 A. The energy difference between the α- and β-chains is about 10 kJ/mol per monomer unit. The dipole moment will be affected by chain curvature (with a radius of about 30.0 A for ideal β-chain) and by defect concentration other than localization. The chain lengths and defects will not significantly affect the mean polarizability. The calculations indicated that there are some additional characteristic vibrational modes that may help identification of the α- and β-phase PVDF.