Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Materials Science and EngineeringSubject: search.filters.subject.Nanocomposites

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  • Master Thesis
    Ferroelectric Ceramic Polymer Nanocomposites for Electrocaloric Cooling Applications
    (Izmir Institute of Technology, 2020) Tokkan, Melike; Adem, Umut; Adem, Umut; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study, nanocomposites consisting of the polymer matrix and nanometer sized ceramic supporting phase were produced for electrocaloric cooling applications, which show potential as alternative refrigerant system. The aim of this study was to be able to estimate adiabatic temperature change (?T) of the composites by measuring saturated hysteresis loops for the composite materials that allow accurate calculation of the ?T using the indirect method based on Maxwell's relations. Ba0.94Ca0.06Ti0.925Sn0.075O3(BCST) composition ceramic was used as the supporting phase of the composite and P(VDF-TrFE)(55-45) co-polymer was chosen as the matrix. The ceramics were synthesized, as pellets by conventional solid-state method. Ferroelectric nanocomposites were manufactured by solution casting method by adding 5, 7.5, 10 volume percent of the ceramic powder, which was obtained by grinding the pellets by using ball milling. Phase analysis of all materials done using X-ray Diffraction method. Fourier Transform Infrared Spectroscopy was used to clearly understand the phase structure of polymer. Scanning electron microscopy was used for understand the distribution of ceramic particles in polymer matrix. Dielectric constant-dielectric loss and ferroelectric hysteresis loops were measured as a function of temperature for the electrical characterization of the materials. Adiabatic temperature change under electric field (?T) of the materials were calculated based on Maxwell's equations indirectly using the temperature dependent electrical polarization data. The dielectric constant and electrical polarization of the polymer matrix have increased with the addition of ceramic particles. The hysteresis loops of thebn pure polymer and composites were saturated, therefore the temperature change can be calculated accurately with the indirect method. Maximum ?T was calculated on the composite having 10vol% ceramic particles. (6.964K at 900 kV/cm).
  • Master Thesis
    Development of Whey Protein Isolate Based Nanocomposite Food Packaging Film Incorporated With Chitosan and Zein Nanoparticles
    (Izmir Institute of Technology, 2014) Oymacı, Pelin; Demir, Mustafa Muammer; Alsoy Altınkaya, Sacide; Alsoy Altınkaya, Sacide; Demir, Mustafa Muammer; 03.02. Department of Chemical Engineering; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The purpose of this study was to investigate the effect of chitosan and zein nanoparticles addition on the barrier and mechanical properties of whey protein isolate (WPI) films as an alternative to conventional synthetic packaging materials. Chitosan nanoparticles (CSNP) were produced via ionic gelation method using sodium tripolyphosphate (TPP) and deacetylated chitosan. Zein nanoparticles (ZNP) were synthesized based on antisolvent procedure in the presence of sodium caseinate (SC) to enable dispersion in water. Both plain and nanoparticle added WPI films were prepared by solution casting method. Water vapor barrier and mechanical properties of films were measured and the improvements in these properties with nanoparticle addition was further investigated through surface wetting, morphological, viscoelastic and thermal properties of the films. Both nanoparticles significantly decreased the water vapor permeability (WVP) and improved the mechanical properties of the WPI film. The highest enhancement in barrier and mechanical properties of the WPI films were recorded with 20% (w/w of WPI) CSNP and 120% (w/w of WPI) ZNP addition which corresponded to the maximum nanoparticle loading levels. At these loadings, the average WVP of pure WPI films loaded with ZNP and CSNP decreased by 84% and 57%, and the average tensile strength increased by 304% and 161%, respectively. On the other hand, the nanoparticles did not change the elongation at break significantly. ZNP was found more effective than CSNP in improving barrier and mechanical properties of the WPI films due to its hydrophobic nature and better dispersion in the protein matrix which allowed much higher loadings compared with the maximum loading levels achieved with CSNP. CSNP addition imparted antibacterial activity to the WPI films.