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Title:	Enhanced piezoelectric properties of poly(vinylidene fluoride) (PVDF) as smart materials for sensor application
Authors:	Ibtisam Yahya Abdullah (P68086)
Supervisor:	Muhammad Yahaya, Prof. Emeritus Dato�� Dr.
Keywords:	Smart materials Sensor application Poly vinylidene fluoride Piezoelectric coefficient Dissertations, Academic -- Malaysia
Issue Date:	16-Feb-2017
Description:	Smart materials such as poly(vinylidene fluoride), PVDF, attracted enormous potential research for sensor and actuators. This is due to its excellent thermal stability, chemical resistance, outstanding mechanical properties, as well as high pyro and piezoelectric coefficient. PVDF is still relatively under development in terms of enhanced piezoelectricity and other physical parameters. One of the main concern is the presence of β-phase fraction in PVDF for sensors application. The main objective of this work is to fabricate PVDF thin film as a piezoelectric pressure sensor. PVDF thin films have been prepared by spin coating and cast techniques. To improve piezoelectric properties in the PVDF thin films, there are two necessary steps: annealing at the specific temperature for suitable time and poling in a high electric field. Primary attention was given to the effect of preparation parameters on the microstructures of PVDF films. The morphology of thin films was determined using SEM and the crystallization structure was investigated by XRD and FTIR. Corona poling method was used to pole the films while the dielectric properties as a function of the frequency were studied using LCR meter. Ferroelectric polarization P-E loop and switching cycling were recorded before poling the samples at different high electric fields using the sawyer-tower circuit. The piezometer were used to measure the piezoelectric constant (d33). By using information of resonance and antiresonans frequency, the electromechanical coupling factor kp were calculated. The essentially spherulites structure, rough and highly porous pure PVDF film were improved by changing the preparation condition. XRD analysis revealed that the main structure of PVDF films was β-phase which was supported by FTIR results. Interestingly, the β-phase fraction increased after poling. Composite films of PVDF/KNaNbO3 (KNN) with different weight ratios demonstrated the enhancement in β phase. The dielectric constant of the composite significantly enhanced with addition the KNN to the PVDF matrix. All samples pure and composite showed a ferroelectric properties, but the hysteresis loop were not saturated. The remnant polarization (2Pr), coercive energy (2Ec) and maximum polarization (2Pmax) were increased with increasing the electric field. The better ferroelectricity with higher 2Pr and lower 2Ec achieved by using lower addition of ceramic KNN. The fatigue tests of composite exhibited the reduction of switchable polarization at 1 × 103 cycles. It was found that the PVDF sensor prepared by cast method displayed a good sensitivity to the applied pressure with good hysteresis, repeatability and unstable. Based on this study, the high fraction of β-phase in PVDF thin films can be achieved by using N,N-dimethylformamide (DMF) and indium tin oxide (ITO) as solvent and substrate respectively together with high annealing temperature. The good pressure sensitivity of PVDF sensor can be improved by the small addition of ceramic. Moreover, this study also provides a facile and low cost method using a new composite material for fabricating pressure sensors.,Certification of Master's/Doctoral Thesis" is not available
Pages:	160
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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