Enhanced Piezoelectric Coefficient of PVDF-TrFE Films via In Situ Polarization

The d33 coefficient = 28 pC/N of PVDF-TrFE piezoelectric films was achieved by the in situ polarization. Compared with traditional poling methods, the in situ polarization is performed with low poling voltage and short poling time, and it can ensure the PVDF-TrFE film with enhanced piezoelectric performances and uniform distribution among a large area of 200 mm2 × 200 mm2. The processing influence of drying, annealing, and poling on the crystalline properties and piezoelectric performances were investigated. Besides, the obtained PVDF-TrFE films present a good piezoelectric response to different extents of mechanical stimulations, which have great potential in energy harvesting applications.

Preparation of PVDF/PAR Composites with Piezoelectric Properties by Post-Treatment

Thermoplastic composites were prepared using poly (vinylidene fluoride) (PVDF) as the matrix with piezoelectric properties and aromatic polyarylate (PAR) as the reinforcing component. The PVDF/PAR conjugate fibers were prepared by melt conjugate spinning. The PVDF/PAR composites were prepared by compression molding of the PVDF/PAR conjugate fiber laminates at various molding temperatures. Drawing and poling post-treatments of the PVDF/PAR composites were performed to increase the β crystalline phase content of the PVDF. The morphologies of the PVDF/PAR composites were observed by scanning electron microscopy, and the tensile properties were tested using an universal testing machine. The crystal structure of the PVDF/PAR composites was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction. The piezoelectric properties were tested using voltmeters and multimeters. The post-treatments enhanced the content of the β crystalline phase of the PVDF matrix, thereby improving the piezoelectric properties of the composites. A molding temperature of 180 °C, drawing temperature of 90 °C, and poling voltage of 12 kV were identified as the optimal conditions for the preparation of the PVDF/PAR composite.

Vibration Reduction of MLCCS Using Vibration-Canceling Effects of Poling Process

MLCC vibrates due to its piezoelectric characteristics and it makes circuit board vibrate and lead to acoustic noise. In order to reduce vibration, piezoelectric coefficient should be reduced. In this study, poling process was used to decrease piezoelectric coefficient. Due to the electrostriction coefficient, response at fundamental frequency can be cancelled by applying voltage to opposite direction. Through the experiment, vibration-cancelling voltage increases as the poling voltage increases. Also, vibration-cancelling voltage increase inversely proportion to MLCC’s capacitance. By applying proper DC bias after poling process, vibration can be reduced.

Poling Effects in Melt-Spun PVDF Bicomponent Fibres

This research shows the successful functionalisation of bicomponent fibres, consisting of a conductive polypropylene (PP) core, doped with carbon nanotubes (CNT) and a piezoelectric sheath (polyvinylidene fluoride, PVDF) by draw winding and poling. These steps lead to the usability of the PVDF’s piezoelectric capabilities. The PP/CNT constitutes the fibre core that is conductive due to a percolation CNT network. The PVDF sheath’s piezoelectric effect is based on the formation of β phase crystals (all-trans conformation), caused by draw-winding of the fibres. This β phase eventually has to be poled for the uniform alignment of polymer chains. The material’s behaviour in high electric field is analysed recording the poling voltage during the poling process. The outcome is hysteresis curves for different β phase contents, which verify a successful material poling.

Real-Time Investigation of Thermal Poling Process in Optic Fiber

Thermal poling could make centrosymmetric fused silica optical fibers generate second-order nonlinearity effect and linear electooptic effect. In order to investigate the influence of thermal poling parameters on linear electooptic effect, a real-time test system, which mainly consists of an all polarization maintaining fiber Mach-Zehnder interferometer, has been utilized to monitor the whole thermal poling process in fibers. The processing parameters in thermal poling, such as applied poling voltage, poling duration and temperature, have been measured in real time. Based on those measurements, their influence on the linear electrooptic effect has been discussed. Experiment results show that the linear electrooptic coefficient would increase when a stronger electric field is applied on fibers. Considering the anti-high-voltage breakdown capability of fibers, a DC voltage from 3KV to 4KV is suitable for polarization in thermal poling. When using 3KV, the optimum poling duration is about 16 minutes and the best temperature for thermal poling is around 190°C. Keywords: electro-optic effect, poled fiber, thermal poling, real time test system, fiber optic interferometer