İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı Tez Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/420

Browse

Now showing 1 - 2 of 2

Proton conductive polymer/metal organic framework composi·te membranes / Proton iletken polimer/metal organik kafes yapılar içeren
(Abdullah Gül Üniversitesi, 2015) MUSTAFA ERKARTAL; AGÜ, Fen Bilimleri Enstitüsü, Malzeme Bilimi ve Makine Mühendisliği Ana Bilim Dalı; MUSTAFA ERKARTAL
Proton exchange membrane fuel cells (PEMFCs) are one of the most innovative research areas in search of novel power sources, especially because of their no to low greenhouse gas emissions, high efficiency, diverse fuel options and low maintenance costs. Hence, PEMFCs are regarded as one of the potential alternatives for the conventional power generators. Proton exchange membrane (PEM) is the core component of the PEMFC. Still, Nafion® and PBI are the commonly used membrane materials in fuel cell technology. The development of novel PEMs with high proton conductivity, good mechanical and chemical stability and cost-effective manufacturing remain as obstacles for the commercialization of PEMFCs. In this thesis for the first time, we present preparation and characterization of two types of novel composite proton exchange membranes which consist of zeolitic imidazolat framework-8 (ZIF-8). In the first part of this study, consisting of poly(vinyl alcohol) (PVA), poly(2- acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and zeolitic imidazolat framework-8 (ZIF-8) ternary Nafion-like composite membranes were prepared with different composition to use in the PEMFCs which of their operation temperatures below 100 0C. All of the membranes were structurally characterized and their proton conductivities were measured by electrochemical impedance spectroscopy. The fully hydrated membrane with 55 PVA/40 PAMPS/5 ZIF-8 composition shows the highest proton conductivity with about 0.13 S cm-1 at 80 0C and the result thus obtained is comparable to the proton conductivity value of the Nafion in the literature. The aim of second part of this study is the preparing of membranes for high temperature proton exchange fuel cells (HTPEMFCs), which operate between 100-200 0C, the binary mixed membrane were manufactured incorporation of PBI and ZIF-8. In the membrane PBI ii was used as host polymer whereas ZIF-8 is used as filler material. Among the structurally well-characterized membranes, the membrane with 12.5 ZIF-8/PBI membrane has the highest proton conductivity with about 0.0045 S cm-1 at 160 0C under anhydrous condition.
Solution-processable rodshaped molecular semiconductors and fieldeffect transistor applications
(Abdullah Gül Üniversitesi, 2018) DENEME, İBRAHİM; AGÜ, Fen Bilimleri Enstitüsü, Malzeme Bilimi ve Makine Mühendisliği Ana Bilim Dalı; DENEME, İBRAHİM
The structural design and synthetic development of novel n-channel organic semiconductors have attracted considerable scientific and technological attention in order to understand the fundamentals of charge-transport mechanisms in organic (opto)electronics. Although large number of n-channel semiconductors have been reported in the literature over the past few decades, solution-processable and air-stable n-channel semiconductors are still scarce. Herein, we report the design, synthesis, single crystal structures, optoelectronic properties, solution-processed thin-film morphologies/microstructures, and organic field effect characteristics of two molecular indeno[1,2-b]fluorenes containing (triisopropylsilyl)ethynyl groups in the 2,8-positions functionalized with carbonyl and dicyanovinylene moieties in the 6,12-positions. Inclusion of electron-withdrawing carbonyl, dicyanovinylene, and (triisopropylsilyl)ethynyl groups to indeno[1,2-b]fluorene cores create fully acceptor type ?-conjugated structures, 2,8-(triisopropylsilyl)ethynyl-indeno[1,2-b]fluorine-6,12- diones (TIPS-IFDK) and 2,8-(triisopropylsilyl)ethynyl-indeno [1,2-b]fluorine-6,12- bis(dicyanoviynlene) (TIPS-IFDM). HOMO/LUMO energies of the new compounds are -5.77/-3.65 eV and -5.84/-4.18 eV for TIPS-IFDK and TIPS-IFDM, respectively. Slightly increased optical band gaps of 2.12 eV (for TIPS-IFDK) and 1.66 eV (for TIPS-IFDM) compared to previously developed donor-acceptor type indenofluorenes could be attributable to their acceptor type ?-conjugated structures. Solid-state ii arrangements and intermolecular ?-? interactions of TIPS-IFDK and TIPS-IFDM were examined via single single-crystal X-ray diffraction (XRD) analysis. The new semiconductors exhibited 1-D columns in the solid-state. OFETs in top-contact/bottomgate transistor geometry utilizing TIPS-IFDM semiconductor layer fabricated via solution-shearing possessed n-channel charge transporting characteristics with an airstable electron mobility 0.02 cm2 (V s)-1 and Ion/Ioff ratios of 107 . However, TIPS-IFDK exhibited three orders of magnitude lower electron mobility in OFETs because of less effective ?-? interactions and the poor crystallinity in thin-film phase, and TIPS-IFDK based OFETs did not exhibit ambient stability. Electronic effects of (trialkylsilyl)ethynyl grops substitutions on frontier molecular orbitals were reavealed by DFT calculations. To the best of our knowledge, TIPS-IFDM is the first example of a solution-processable, air-stable n-type molecular semiconductor functionalized with (trialkylsilyl)ethynyl groups along the long molecular axis. Our results clearly provide a novel molecular design approach for the development of easily synthesizable, solution-processable semiconductors for ambientstable n-channel organic field-effect transistors and potentially various organic (opto)electronic technologies.

Browse

Browsing İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı Tez Koleksiyonu by Author "AGÜ, Fen Bilimleri Enstitüsü, Malzeme Bilimi ve Makine Mühendisliği Ana Bilim Dalı"