Phd Degree / Doktora

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Separation of Macromolecules From Aqueous Systems Using Electrospun Fibers
(Izmir Institute of Technology, 2018) Işık, Tuğba; Demir, Mustafa Muammer
Electrospinning has been recognised as a versatile method for the fabrication of continuous polymeric fibers with various type of morphology. Since it allows changing the fiber diameter, surface morphology and porosity by adjusting the solution and instrumental parameters, electrospun fibers present a wide range of properties that cannot be found in bulk materials. Through this thesis, removal of several types of pollutants from the aqueous systems was studied by using the electrospun fibers fabricated from both virgin and waste polymers. The first part of the dissertation deals with the removal of macromolecular pollutants from aqueous systems by using waste-based electrospun fibers. Electrospun fibers fabricated from CD cover and expanded polystyrene wastes were utilized for the protein-rich medical waste treatment by using Bovine Serum Albumin, Myoglobin and Trypsin as protein models. Electrospun fibers from expanded polystyrene wastes were utilized for the remediation of oily wastewaters. The second part of the dissertation deals with the polyatomic nuclear waste removal using uranyl ions as analyte and amidoxime functionalized PIM-1 electrospun fibers. The last part of this dissertation describes an approach for the fabrication of fluorine-free hydrophobic surfaces by electrospraying of methacrylate based linear and hyperbranched copolymers.
Toughening of Carbon Fiber Based Composites With Electrospun Fabric Layers
(Izmir Institute of Technology, 2017) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, Engin
The objective of this PhD thesis is to investigate interlaminar Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by micro and/or nano scaled PA66 nonwoven veils. Also, the effects of electrospun PVA nanofibers on the mechanical performance of these composites were investigated. Additionally, this thesis also deals with the effects of aramid nonwoven veils on the mechanical properties of CF/EP composites. The produced nanofibers produced by electrospinning were directly deposited on carbon fiber fabrics. Then, reference and nano-modified laminates were manufactured by vacuum infusion method. A series of mechanical tests such as tensile, compression, three point bending, Charpy-impact, interlaminar shear strength and open hole tensile tests (OHT) were carried out on the prepared specimens. Double cantilever beam (DCB) tests were conducted on reference and interleaf-modified laminates. The effect of PA 66 nanofiber areal weight density was also evaluated with varying electrospinning time. Scanning electron microscopy (SEM) was used to investigate the fiber morphology and to understand the toughening mechanisms. Dynamic mechanic analysis (DMA) was used to investigate the thermo-mechanical behavior of reference and interleaf-modified composite specimens. Differential scanning calorimetry (DSC) was used to determine the thermal properties of micro and electrospun PA66 nonwoven veils. Comparing the mechanical test results, the most effective nonwoven interleaving system was determined in terms of higher delamination resistance and in-plane mechanical properties. Finite element method (FEM) was used to evaluate the effects of electrospun PA66 nonwoven veils on the CF/EP composites. Numerical simulations of Mode-I fracture toughness tests were carried out using ANSYS Workbench. The results showed that the most effective material was electrospun PA66 nonwovens considering the higher delamination resistance. Additionally, the electrospun PA 66 nonwovens also improved Charpy-impact and interlaminar shear strength of the reference CF/EP composites. Numerical results showed good agreement with the experimental ones.
Applications of Electrospun Nanofibers in Filtration Processe
(Izmir Institute of Technology, 2013) Horzum Polat, Nesrin; Elçi, Latif
Electrospinning is a simple and versatile method to fabricate ultrathin fibrous mats from a wide variety of organic and/or inorganic materials. Since it allows fabricating fiber diameter and surface/internal structures by solution and instrumental parameters, electrospun fibers provide much enhanced functionalities, which can not be obtained by bulk materials. This thesis examines the filtration, sensing and catalytical applications associated with the remarkable features of electrospun nanofibers. The systems studied are reported herein; (i) The first part of this dissertation deals with the filtration applications of electrospun nanofibrous membranes.  Nano-sized chitosan fibers were utilized for sorption of Fe(III), Cu(II), Ag(I), and Cd(II) ions from aqueous solutions.  The surface of chitosan fibers were further functionalized by monodisperse nano zero-valent iron (nZVI) particles for the removal of inorganic arsenic species.  Sorption of radioactive U(VI) ions from aqueous systems via column sorption under continuous flow was performed using amidoximated polyacrylonitrile fibers. (ii) The second part of this dissertation presents sensing applications of ceramic fibers.  Humidity sensing properties of electrospun ZnO fiber mats were investigated by quartz crystal microbalance (QCM) method and electrical measurements.  Electrospinning technique was used as coating process for deposition of CeO2/ZnO and ZnO based nanofibers on the electrode of QCM. The fiber-coated QCM sensors were used for the detection of volatile organic compounds (VOCs). (iii) The last part of this dissertation describes an approach to fabricate hierarchically structured composite nanofibers. The nanostructured materials prepared by the simultaneous electrospinning of CeO2 and LiCoO2 precursors and SiO2 nanoparticles were used for the photocatalytic degradation of Rhodamine B.

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