Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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Publisher: search.filters.publisher.Izmir Institute of TechnologySubject: search.filters.subject.Nanocomposites (Materials)

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  • Doctoral Thesis
    Enhancement of Thermal, Electrical and Optical Properties of Zinc Oxide Filled Polymer Matrix Nano Composites
    (Izmir Institute of Technology, 2009) Özmıhçı, Filiz; Balköse, Devrim; Balköse, Devrim; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The purpose of this study is to enhance the electrical, thermal and optical properties of polyethylene and polypropylene by the addition of zinc oxide (ZnO) filler.Embedding ZnO in a polymeric matrix could make an economic, weight saving, chemically resistive, optical, flexible and conductive materials which possesses the properties of zinc oxide.Composites with higher electrical and thermal conductivity having luminescence properties were prepared using commercial and hydrothermally synthesized ZnO powders with different particle size and conductivity. Effect of ZnO loading and surface treatment on composite properties was investigated. Luminescence effects in green and blue regions were detected in all powders due to the defects on the structure of ZnO.The powders were found to be moderately conductive materials, as well. Un-homogenously dispersed composites were prepared using rheomixer since especially nano powders tended to be agglomerated in the composite. On the other hand, different surface properties of powder and polymer caused adhesion and wetting problems. Microvoids were detected in the interphase, as well.Composites can be used as an electrostatic dissipation and moderate electrical conductive applications in the field of electrical conductivity, as a heat sink in the field of thermal conductivity and as a solid state lamp due to luminescence properties. Stiffness of the composites was very high compared to neat polymer and can be properly used as an engineering material.
  • Doctoral Thesis
    Use of Bio-Nano Composites as Protective Coating on Natural Stone Surfaces
    (Izmir Institute of Technology, 2013) Ocak, Yılmaz; Sofuoğlu, Aysun; Sofuoğlu, Aysun; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Historical monuments are important heritages to pass cultural values to next generations. Most of the historical monuments were composed of natural stones like marble. SO2 and NOx reacts with marble composed primarily of calcite (CaCO3) is a dry deposition process, gypsum (CaSO4.2H2O) and nitrocalcite (Ca(NO3)2.4H2O) are formed after reaction. The polylactic acid (PLA), 2, 5 and 7 wt.% montmorillonite (MMT) clay added PLA (PLA/MMT2, PLA/MMT5 and PLA/MMT7) bio-nano composites coated and uncoated surfaces were tested for capillary water absorption, water vapor permeability, color alteration, and surface hydrophobicity regarding the nanofiller concentrations before reaction. Results indicated that the bio-nano composite coatings didn’t alter the color of the marble, improved the hydrophobicity and barrier properties of the marbles. The level of layered silicate delamination in the PLA matrix and structural characterizations of PLA nanocomposite coatings were affected the barrier properties of the composites coatings. The X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM) analysis pointed out that 5% layered silicates were homogenously dispersed in the polymer matrix, exfoliated structures also were observed in some parts of the polymer matrix and nano particles enhanced the nano-composite coating barrier performance. The protection capabilities of the bio-nano composite coatings were studied in laboratory setup (include nearly 8 ppm SO2) and ambient city atmosphere (include nearly 8 ppb SO2 and 64 ppb NO2). The PLAMMT5 bio-nano composite showed significant reduction (~5 times) in the crust formation after 180 days SO2-calcite reaction in laboratory and 9-10 times after 20 months ambient city exposures for outdoor conditions. Bio-nano composites also decreased the kinetic parameters such as rate constant (ks) and effective diffusivity (De) values of the marbles. These results indicated that PLA/MMT bio-nano composite coating seems to be significant promising materials as protective coating agents in reducing the effects of atmospheric pollutants on the marble surfaces.