Hot pressing process ameliorates internal defects of PBZ/PVDF composite film for a high electrocaloric effect near room temperature

2021 ◽  
Author(s):  
Guoming Qian ◽  
Kongjun Zhu ◽  
Kang Yan ◽  
Jing Wang ◽  
Jinsong Liu ◽  
...  
Keyword(s):  
Electric Field ◽  
Composite Film ◽  
Hot Pressing ◽  
Polyvinylidene Fluoride ◽  
Organic Polymer ◽  
Interface Problem ◽  
Pvdf Film ◽  
Internal Defects ◽  
Electrocaloric Effect ◽  
The Impact

The poor interface compatibility between inorganic fillers and organic polymer matrix in nanocomposite has presented considerable challenges, which limit the applicable electric field ranges and reduce the interface polarization interaction. In this paper, Pb[Formula: see text]Ba[Formula: see text]ZrO3 (PBZ) nanofibers were introduced into the polyvinylidene fluoride (PVDF) matrix to prepare composite film, and the effect of hot pressing on interface compatibility was investigated at volume composite ratios of 3% and 4%. For the untreated film, [Formula: see text] and [Formula: see text] of the 3 vol.% composite film are 9.68 [Formula: see text]C/cm2 and 401 MV/m, respectively, and those for the 4 vol.% composite film are 9.15 [Formula: see text]C/cm2 and 408 MV/m, respectively. These differences are mainly due to the impact of internal defects. After hot pressing, [Formula: see text] and [Formula: see text] for the 3 vol.% composite film became 10.22 [Formula: see text]C/cm2 and 490 MV/m, respectively. Those for the 4 vol.% composite film are 9.85 [Formula: see text]C/cm2 and 485 MV/m. Experiment and simulation results showed the beneficial effect of hot pressing, which ameliorated poor interfacial compatibility, reduced internal defects, and improved the crystallinity of the composite film. A high electrocaloric effect (ECE) was obtained by using the direct measure method. At −30[Formula: see text]C, the [Formula: see text] values of hot-pressed PBZ/PVDF film at 3[Formula: see text] and 4[Formula: see text] vol.% were 23.81 and 19.73 K, respectively. When temperature increased to 70[Formula: see text]C, the [Formula: see text] values were 9.44 and 7.01 K, respectively, which were 1.58 times of the values of a non-hot-pressed film. These results indicated that hot pressing alleviated the interface problem and resulted in high EC performance under a high-strength electric field.

Heartbeat Monitoring Technique Based on Corona-Poled PVDF Film Sensor for Smart Apparel Application

2007 ◽  
Vol 124-126 ◽  
pp. 299-302 ◽  
Author(s):  
You Min Chang ◽  
Jong Soon Lee ◽  
Kap Jin Kim
Keyword(s):  
Electric Field ◽  
Polyvinylidene Fluoride ◽  
Ferroelectric Properties ◽  
Computer Applications ◽  
Polymer Materials ◽  
Pvdf Film ◽  
Internal Electric Field ◽  
Film Sensor ◽  
Β Phase ◽  
Voltage Amplifier

Flexible piezoelectric polymer materials for smart apparel and wearable computer applications are of great interest. Among known ferroelectric and piezoelectric polymers, polyvinylidene fluoride (PVDF) exhibit β-phase under poling and is known to give highest piezo-, pyro-, and ferroelectric properties. Previous reports suggests that, during corona poling of the PVDF film, a high surface electric potential is generated resulting in a high internal electric field within the polymer film causing the polarization of the dipoles along the direction of the applied electric field. The resultant phase change from α- to β-phase and the dipole switching generates displacement of charges or piezoelectricity. And also mechanical variation would change dipole density of PVDF film. In this report, we measured human heartbeat signal from an DAQ interfaced with a custommade voltage-amplifier with specific frequency filtering function using the corona-poled PVDF film of various sizes and thickness as a piezoelectric sensor and analyzed it. We employed elastic textile band to sensor system for comfortable fit on wrist or ankle. And then, we found the feasibility of applying flexible PVDF film sensor to smart apparel application which can sense heartbeat rate, blood pressure, respiration rate, accidental external impact on human body, etc.

scholarly journals Electric Field Simulation and Effect of Different Solvent Ratios on the Performance of Single Electrospun PVDF/PEI Composite Film

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Jin-gang Jiang ◽  
Zhao Wang ◽  
Hong-wei Duan ◽  
Jing-qiang Liu ◽  
Xiao-wei Guo
Keyword(s):  
Mechanical Properties ◽  
Electric Field ◽  
Composite Film ◽  
Polyvinylidene Fluoride ◽  
Mixed Solvent ◽  
Composite Fiber ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Fiber Membranes ◽  
Vector Distribution

On the basis of the finite element calculation theory of electric field, the electric field distribution in a representative electrospinning device is computed. The electric field structure of a needle-plate type electrospinning device was simulated by means of ANSYS software. And the vector distribution of the nozzle on the spinneret pipe was got. For the purpose of the analysis on the influence of different solvent ratios on the performance of a single electrospun PVDF/PEI composite film, polyvinylidene fluoride and polyetherimide with a mass ratio of 8/2 were dissolved in a mixed solvent. The mixed solvent is composed of N,N-dimethylformamide and tetrahydrofuran, added in different proportions. Through the electrostatic spinning technology, PVDF/PEI composite fiber membranes were prepared. Using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and mechanical properties testing, the effects of tetrahydrofuran on the composite microstructure, crystallinity, and mechanical properties of the PVDF/PEI composite fiber membranes are discussed.

scholarly journals The Impact of the Electric Field on Surface Condensation of Water Vapor: Insight from Molecular Dynamics Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 64 ◽  
Author(s):  
Qin Wang ◽  
Hui Xie ◽  
Zhiming Hu ◽  
Chao Liu
Keyword(s):  
Molecular Dynamics ◽  
Water Vapor ◽  
Electric Field ◽  
Intermolecular Forces ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Attraction Force ◽  
Condensation Rate ◽  
Shape Transformation ◽  
The Impact

In this study, molecular dynamics simulations were carried out to study the coupling effect of electric field strength and surface wettability on the condensation process of water vapor. Our results show that an electric field can rotate water molecules upward and restrict condensation. Formed clusters are stretched to become columns above the threshold strength of the field, causing the condensation rate to drop quickly. The enhancement of surface attraction force boosts the rearrangement of water molecules adjacent to the surface and exaggerates the threshold value for shape transformation. In addition, the contact area between clusters and the surface increases with increasing amounts of surface attraction force, which raises the condensation efficiency. Thus, the condensation rate of water vapor on a surface under an electric field is determined by competition between intermolecular forces from the electric field and the surface.

scholarly journals Generating Electricity from Natural Evaporation Using PVDF Thin Films Incorporating Nanocomposite Materials

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 585
Author(s):  
Ariel Ma ◽  
Jian Yu ◽  
William Uspal
Keyword(s):  
Thin Films ◽  
Graphene Oxide ◽  
Polyvinylidene Fluoride ◽  
Capillary Flow ◽  
Short Circuit ◽  
Current Source ◽  
Nanocomposite Materials ◽  
The Other ◽  
Pvdf Film ◽  
Ambient Conditions

Natural evaporation has recently come under consideration as a viable source of renewable energy. Demonstrations of the validity of the concept have been reported for devices incorporating carbon-based nanocomposite materials. In this study, we investigated the possibility of using polymer thin films to generate electricity from natural evaporation. We considered a polymeric system based on polyvinylidene fluoride (PVDF). Porous PVDF films were created by incorporating a variety of nanocomposite materials into the polymer structure through a simple mixing procedure. Three nanocomposite materials were considered: carbon nanotubes, graphene oxide, and silica. The evaporation-induced electricity generation was confirmed experimentally under various ambient conditions. Among the nanocomposite materials considered, mesoporous silica (SBA-15) was found to outperform the other two materials in terms of open-circuit voltage, and graphene oxide generated the highest short-circuit current. It was found that the nanocomposite material content in the PVDF film plays an important role: on the one hand, if particles are too few in number, the number of channels will be insufficient to support a strong capillary flow; on the other hand, an excessive number of particles will suppress the flow due to excessive water absorption underneath the surface. We show that the device can be modeled as a simple circuit powered by a current source with excellent agreement between the theoretical predictions and experimental data.

scholarly journals Restraining Surface Charge Accumulation and Enhancing Surface Flashover Voltage through Dielectric Coating

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 750
Author(s):  
Jixing Sun ◽  
Sibo Song ◽  
Xiyu Li ◽  
Yunlong Lv ◽  
Jiayi Ren ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Electric Field ◽  
Electric Fields ◽  
Transition Process ◽  
Metallic Particle ◽  
Particle Charging ◽  
Insulating Surfaces ◽  
Surface Flashover ◽  
Charging Time ◽  
The Impact

A conductive metallic particle in a gas-insulated metal-enclosed system can charge through conduction or induction and move between electrodes or on insulating surfaces, which may lead to breakdown and flashover. The charge on the metallic particle and the charging time vary depending on the spatial electric field intensity, the particle shape, and the electrode surface coating. The charged metallic particle can move between the electrodes under the influence of the spatial electric field, and it can discharge and become electrically conductive when colliding with the electrodes, thus changing its charge. This process and its factors are mainly affected by the coating condition of the colliding electrode. In addition, the interface characteristics affect the particle when it is near the insulator. The charge transition process also changes due to the electric field strength and the particle charging state. This paper explores the impact of the coating material on particle charging characteristics, movement, and discharge. Particle charging, movement, and charge transfer in DC, AC, and superimposed electric fields are summarized. Furthermore, the effects of conductive particles on discharge characteristics are compared between coated and bare electrodes. The reviewed studies demonstrate that the coating can effectively reduce particle charge and thus the probability of discharge. The presented research results can provide theoretical support and data for studying charge transfer theory and design optimization in a gas-insulated system.

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