Dielectric behavior characterization of functional fibrous-ceramic/polymer nanocomposites
Dağdeviren, Canan (2009) Dielectric behavior characterization of functional fibrous-ceramic/polymer nanocomposites. [Thesis]
Official URL: http://192.168.1.20/record=b1293709
This study is mainly focused on forming fibrous-ceramic/polymer nanocomposites and characterizing their dielectric behavior. The fibrous-ZnO/PVDF nanocomposite is prepared in two steps. First, a network of nano-scale zinc oxide (ZnO) fibers is produced by sintering electrospun PVA/Zinc Acetate fibers. Second, the ZnO fibrous non-woven mat is sandwiched between two polyvinylidine fluoride (PVDF) thermoplastic polymer films by hot-press casting. Referring to the extensive literature search within the thesis, this work is the first demonstration of the use of electrospinning to secure the dispersion and distribution of a network of inorganic fillers. Moreover, processing a fibrous-ZnO/PVDF flexible composite facilitate material handling and enable dielectric property measurement, in contrast to that on a fibrous mat of pure ZnO. Due to the high surface area of the short ZnO fibers and their polycrystalline structure, interfacial polarization is pronounced in the nanocomposite film. The dielectric constant is enhanced significantly—up to a factor of ten at low frequencies compared to the dielectric constant of constituent materials (both bulk ZnO and PVDF), and up to a factor of two compared to a bulk- ZnO/PVDF composite. Similar effort is also presented for the fibrous-PZT/polyvinylester nanocomposite. Nanofibers are obtained by electrospinning a sol-gel based solution and polyvinyl pyrrolidone (PVP) polymer, and subsequent sintering of the electrospun precursor fibers. The average diameter of the precursor PZT/PVP green fibers is increased with the aging of the precursor solution along with an increase in the viscosity. Preparation of 3-3 nanocomposites by infusion of polyvinylester into the nanofiber mat facilitates successful handling of the mats and enables measurements of dielectric properties.
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