Enerji Hasatı ve Biyomedikal Uygulamalar İçin Manyetik Polimer Kompozitler
Özet
Polyvinylidene fluoride (PVDF), which is a family of piezoelectric polymers, is a material that stands out in technologies such as energy harvesting and sensor applications because it is flexible, lightweight and biocompatible. The PVDF polymer has five different semicrystalline phases i.e. Alpha, Beta, Eta, Sigma and Gamma. The most stable Alpha-phase is not polar, Beta and Gamma phases are polar, Beta-phase has the highest piezoelectric property. The structure of PVDF can be altered between phases depending on the production technique. In this study, electrospinning method was used to obtain PVDF in the form of a mixture of polar Beta and Gamma phases (Electro Active; EA). The structural properties of the produced PVDF fibers were determined by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimeter (DSC) methods. In this study, changes in EA phase ratio versus electrospinning parameters such as pumping rate, distance, solvent and rotation speed were determined by FTIR analysis. It was determined that the ratio of EA phase in PVDF fibers could be increased from 80% to 97% by optimizing the physical parameters controlled in electrospinning. The morphologies of the PVDF fibers / films were analyzed by scanning electron microscopy (SEM) images. In order to determine the piezoelectric properties of samples containing different ratios of EA phase, the piezoelectric coefficient measurement device was designed in our lab. The change of d(1,2) piezolectric constant was measured within the range of 2.7±0.2 - 7.2±0.4 [pC / N]. In the second part of the study, the efficiency of composite structures formed by adding superparamagnetic Fe3O4 nanoparticles of 10±2 nm in size to the PVDF fibers in hyperthermia treatment was determined by measuring magneto-thermal properties. For this, three different nanocomposites were created by 7.57±0.01 wt.%, 12.51±0.01 wt.% and 15.40 ±0.01 wt.% (Fe3O4/(PVDF+ Fe3O4)). Time-dependent temperature changes of the samples were measured in the presence of RF magnetic field and Specific Absorption Rates (SAR) of samples were calculated as 8.5±0.1, 8.4±0.1 and 8.2±0.1 W/g respectively.
