Synthesis and characterization of poly(vinylidene fluoride)/carbon nanotube composite piezoelectric powders (original) (raw)
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A flexible piezoelectric force sensor based on PVDF fabrics
Smart Materials and Structures, 2011
Polyvinylidene fluoride (PVDF) film has been widely investigated as a sensor and transducer material due to its high piezo-, pyro-and ferroelectric properties. To activate these properties, PVDF films require a mechanical treatment, stretching or poling. In this paper, we report on a force sensor based on PVDF fabrics with excellent flexibility and breathability, to be used as a specific human-related sensor. PVDF nanofibrous fabrics were prepared by using an electrospinning unit and characterized by means of scanning electron microscopy (SEM), FTIR spectroscopy and x-ray diffraction. Preliminary force sensors have been fabricated and demonstrated excellent sensitivity and response to external mechanical forces. This implies that promising applications can be made for sensing garment pressure, blood pressure, heartbeat rate, respiration rate and accidental impact on the human body.
Characteristics of Piezoelectric Polymeric PVDF Sensor by Impact Testing
Polymer Korea, 2019
The 18 wt% poly(vinylidene fluoride) (PVDF) fibers were near-field electrospun at a flow rate of 139 nL/min, an electric field of 12 kV/cm, and a collector speed of 500 mm/s. A PVDF fiber array consisting of 20 fibers was adhered to the flexible PET film. A PVDF and a lead zirconate titanate (PZT) sensors were attached at a distance of 5 mm from the clamped end of the Al cantilever. The vibration sensing capabilities of sensors were examined by measuring the potential generated by the sensors during impact testing. Although the voltage of PVDF sensor was 200 times smaller than that of PZT sensor, the waveforms of the sensor output were similar. Both sensors were determined to be sensitive to variations in the level of dynamic strain due to the inherent piezoelectricity. The spectral results of both sensors exhibited the same signal generated by natural frequency of cantilever.
Nano-Scale Characterization of a Piezoelectric Polymer (Polyvinylidene Difluoride, PVDF)
Sensors, 2008
The polymer polyvinylidene difluoride (PVDF) has unique piezoelectric properties favorable for Micro-Electro-Mechanical Systems (MEMS) and Nano-Electro-Mechanical Systems (NEMS) applications. In the present research, we conducted nanometer-length scale characterization of this material using several high-resolution techniques. Specifically, we used an atomic force microscope (AFM) to study the nanoand microstructures of the PVDF under stress and to measure their nanoscale conductivity and piezoelectricity. We found that the surface morphology, electronic structure, and microstructure are profoundly affected under electrical potential. Such a behavior is important for the properties and performance of MEMS and NEMS.
Mechanisms for Enhancing Polarization Orientation and Piezoelectric Parameters of PVDF Nanofibers
Advanced Electronic Materials, 2018
In 1941, Martin presented piezoelectricity in aligned human hair. [5b] In 1950, quantitative studies on the piezoelectricity of wood were originated by Bazhenov and Konstantinova. [5c] In 1957, Fukada and Yasuda found shear piezoelectricity in bone. [5d] Fukada extended the research on shear piezoelectricity to many kinds of polymers such as polysaccharide, proteins, and synthetic polymers. [6] Strong piezoelectric effect in polar polymers was first revealed by Kawai in 1969 by drawing and poling a polyvinylidene fluoride (PVDF) film, [7] followed by reports of piezoelectric effect in polyvinylchloride, polycarbonate, and nylon 11. [8] Currently, PVDF and its copolymers are the most technically important piezoelectric polymers. [2] PVDF is a semicrystalline polymer consists of a repeated monomer unit of CH 2 CF 2 which is characteristically polar because of the electropositive hydrogen atoms and the electronegative fluorine atoms in contrast to the carbon chain. [7] PVDF exhibits four crystalline phases, designated as α, β, γ, and δ. [8] Among those phases, β phase has the largest spontaneous polarization, exhibiting the most significant ferroelectric and piezoelectric effects. [9] The piezoelectric strain and voltage coefficients (such as d 33 and g 33) are often used as the metrics for evaluating piezoelectric property. Typically, β-phase PVDF polymers exhibit a d 33 value of about −25 to −35 pm V −1. Theoretical study on PVDF has suggested that equivalent macroscopic piezoelectric d 33 value could possibly reach −186 pm V −1 , but this has not been achieved experimentally. [10] As α phase is the thermodynamic stable crystalline phase to improve piezoelectric performance of PVDF, many studies focus on enhancing the polar phase formation through various techniques, such as mechanical stretching, [7] high electrical field poling, [11] melting and crystallization under high pressure, [12] electrospinning, [3] and use of additives including hydrated salts, [13] clay, [14] ferrite nanoparticles, and carbon nanotubes. [15] Among them, introducing hydrated salts in PVDF precursor solution proves very effective in improving the content of polar β phase, promoted by hydrogen bonds formation between fluorine and hydroxyl group in the hydrated salts. [13,16,17] On the other hand, it is noted that the structure and piezoelectric properties of PVDF can be manipulated through nanoscale Many emerging applications strongly demand flexible and efficient electromechanical conversion materials. Polymeric piezoelectric materials, with ability of large area and low temperature processing, are attractive to obtain wide applications for electromechanical sensors, transducers, and mechanical energy harvesters. A major drawback of the polymeric piezoelectric materials is their much lower piezoelectric performance property, such as piezoelectric strain coefficient, than their ceramic counterparts. Here, outstanding piezoelectric performance properties with giant effective strain and voltage coefficients of −116 pm V −1 and −1180 V mm N −1 are achieved in electrospun polyvinylidene fluoride nanofiber films from the precursor solution modified with hydrated salt. The experimental results and theoretical analysis clarify a synergistic interactive role from the hydrated salt and the electric field during electrospinning, effectively leading to polarization enhancement and alignment, and hence the giant macroscopic piezoelectric coefficients in the obtained electrospun fiber films. The demonstrated results and the understanding on the underlying mechanism exhibit the potential and strategy in achieving high-performance functional materials through dedicated control on their nanostructures and polarizations.
A Review of Piezoelectric PVDF Film by Electrospinning and Its Applications
Sensors
With the increase of interest in the application of piezoelectric polyvinylidene fluoride (PVDF) in nanogenerators (NGs), sensors, and microdevices, the most efficient and suitable methods of their synthesis are being pursued. Electrospinning is an effective method to prepare higher content β-phase PVDF nanofiber films without additional high voltage poling or mechanical stretching, and thus, it is considered an economically viable and relatively simple method. This work discusses the parameters affecting the preparation of the desired phase of the PVDF film with a higher electrical output. The design and selection of optimum preparation conditions such as solution concentration, solvents, the molecular weight of PVDF, and others lead to electrical properties and performance enhancement in the NG, sensor, and other applications. Additionally, the effect of the nanoparticle additives that showed efficient improvements in the PVDF films was discussed as well. For instance, additives o...
A Dynamic Micro Force Sensing Probe Based on PVDF
Sensors & Transducers, 2010
Polyvinylidene fluoride (PVDF) membrane structure is presented as micro-force sensor which has potential applications in dynamic amplitude modulation scanning probe microscopy (SPM). Driven by two symmetric aligned PZT actuators near its resonance, the membrane has high force and spatial sensitivity. Glued at the bottom of the membrane's center, an electrochemical etched tungsten stylus is utilized as micro force picker which has high height diameter ratio. Experiments are conducted to verify its dynamic performance like resonant frequencies, spring constant, quality factor and spatial sensitivity of this micro-force sensing probe. This micro-force sensor can be used for high step height surface topographic measurement of soft materials with little damage.
Characterization of Piezoelectric Response of PZT Nanofibers
2007
A mixture of reduced graphene oxide (rGO) with esmeraldine (rGO-Esmeraldine) was used in order to modify the piezoelectric properties of vinylidene polyfluoride (PVDF). PVDF films were prepared by dissolving PVDF powder in a solution of N, N-Dimethylformamide (DMF), preheated at 60 ° C, to enhance the β phase of 4798 Lina Marcela Hoyos Palacio et al. the PVDF, the phase responsible for the piezoelectric effect. The influence of the r-GO-Esmeraldine mixture on the piezoelectric properties of the PVDF was characterized by X-ray diffraction. Changes in piezoelectric potential were observed by varying the mass percentage of the rGO-emeraldine mixture in the PVDF films. The results show an increase in potential by adding 0.1 wt% and 0.3 wt% of the rGO-emeraldine mixture. At concentrations greater than 0.3wt% the formation of the β phase in the PVDF is reduced due to the inhomogeneous distribution of the rGO in the PVDF film and the crystallization thereof as a consequence of the addition of esmeraldine that was evidenced by Scanning Electron Microscopy (SEM).
Voltage tunable sensitivity of piezoelectric materials based sensors and actuators
2009
This paper presents the results from dynamic measurements of piezoelectric constant d 33 using Atomic Force Microscopy. It is found that d 33 constant linearly depends on the DC bias voltage applied across the pre-polarized samples of Polyninylidene Fluoride-Trifluoroethylene i.e. P(VDF-TrFE). Thus, the DC voltage can be used to tune the piezoelectric constant and hence the sensitivity of the sensors and actuators using piezoelectric materials.