Filtreler
Nanocomposites with graphene

Doktora Tezi | 2018 | İzmir Katip Çelebi Üniversitesi Fen Bilimleri Enstitüsü

The carbon fiber used in the manufacturing of advanced composites has various applications in the automotive, aerospace, and electronics industry because of their comprehensive properties such as lightweight, flexibility, high strength to weight ratio, excellent chemical resistance, superior electrical conductivity and thermal conductivity. Different kinds of carbon fiber precursors have been used and polyacrylonitrile (PAN) is the mostly utilized polymer type which is a petroleum-based, expensive and unsustainable. Remarkably, lignin is a highly accessible, low-cost, and renewable resource. Also, lignin is a byproduct of pulp and . . .paper industry as well as cellulosic ethanol fuel production. So, the reuse of this byproduct is very significant for the bioeconomy. Accordingly, understanding the structure, types, and extraction methods of lignin are of great importance for transferring these biomass residues from a low-value material to a higher value product. This work started with the extracted lignin from Turkish resources (Turkish Pine and Turkish Vine stem) by sulfuric acid treatment and to compare with commercial lignin. Additionally, we investigated lignin to identify its suitability as a carbon fiber precursor and to use for reducing the processing cost of carbon fiber production compared to other precursors. In this thesis, sub-micron lignin-based nanofibers were produced by electrospinning of solutions obtained by dispersing lignin, polyacrylonitrile (PAN) and then graphene (GRP) in N, N-dimethylformamide (DMF). Lignin-based carbon nanofibers were investigated by focusing on the steps of manufacture. Resource types and corresponding pretreatments improve the processability of spinning and thermal treatments. Defect-free nanofibers with up to 5 wt. % lignin/PAN and 1% graphene were fabricated successfully. The succeeding step is the most significant process of stabilization, where nanofibers are oxidized, crosslinked, and thermally stabilized for the following step. After carbonization, lignin-based carbon nanofibers are obtained. When carbonized at 900 °C, PAN/Lignin/GRP carbon nanofiber presents carbon content of 94.3% and with average diameter ~ 100 nm. Effects of every single step on the lignin-based carbon nanofibers have been discussed comprehensively. To sum up, the low cost of carbon nanofibers and graphene reinforced carbon nanofibers can be used in numerous fields, mainly for electronic devices containing biosensors and supercapacitors. In this thesis, the characterization of carbon nanofiber (CNF) and graphene reinforced carbon nanofiber (CNF-G) modification onto the screen printed electrode (SPE) has been verified via Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The charge transfer resistance, Rct values obtained by electrochemical circle fit option of EIS have been utilized for conductivity detection of modified electrodes. In the last part of this thesis, CNF and CNF-G modified electrodes were performed for an effective biosensor to detect acetaminophen Daha fazlası Daha az

New grade of thermoplastic polyurethane with high thermal conductivity and low coefficient of friction

Semiz, Seçkin

Yüksek Lisans | 2017 | İzmir Katip Çelebi Üniversitesi Fen Bilimleri Enstitüsü

Today, thermoplastic polyurethane materials are widely used in many different applications. There are many types of thermoplastic polyurethanes which offers different mechanical and chemical properties according to application area. In addition to the existing properties, thermoplastic polyurethane materials mixed with various additives to obtain specific, targeted thermoplastic polyurethane materials in order to impart different properties to the material for application. In this study, materials of the sealing elements are approached which is one of the most important parts of the hydraulic & pneumatic systems widely used i . . .n industry. Nowadays when energy efficiency and product life become vital, it is quite important that prolongation of the sealing element life, increasing the energy efficiency and reducing maintenance requirements for hydraulic & pneumatic sealing elements sector. This study gains importance in terms of bringing the properties such as low coefficient of friction and high thermal conductivity coefficient in materials of hydraulic pneumatic sealing materials without breaking the standard physical and chemical properties of the material. Standard features expected from hydraulic & pneumatic sealing materials summarized as tensile strength, elongation at break, hardness, deformation under pressure (compression set) and wear resistance. In addition to these properties of standard materials, it envisaged that imparting low coefficient of friction to materials will reduce wearing because of friction and heat formation, imparting high thermal conductivity will facilitate transferring the heat generated from the material to the surrounding area. If these two properties are insufficient, burn spots and abrasions due to temperature increase observed in the working surfaces of the sealing elements. Herewith these problems cause leakage that is the indication of failure. By preventing these situations, the sealing elements will be able to benefit from the sector with higher energy efficiency and longer working life. Four different additive materials such as boron nitride, MoS2 ,graphite and PTFE were used at three different doses each to gain the specified properties to the thermoplastic material which is used in this study. The base material compounded with the additives was re-granulated with twin-screw extruder and after heat treatment of the materials, test plaques and sealing elements were produced with the help of plastic injection machines. xxvi FTIR, thermal conductivity coefficient, tensile, compression set, coefficient of friction and friction tests carried out to examine the properties expected to change. When all the results analyzed according to the tests performed, it has been observing that Sample 6 which has 5% PTFE acquired the targeted properties without deteriorating the existing properties. In this compounded material, the coefficient of thermal conductivity increases and the coefficient of friction decreases while the hardness, stress at 100% strain and compression set values are within acceptable limits Daha fazlası Daha az

6698 sayılı Kişisel Verilerin Korunması Kanunu kapsamında yükümlülüklerimiz ve çerez politikamız hakkında bilgi sahibi olmak için alttaki bağlantıyı kullanabilirsiniz.

creativecommons
Bu site altında yer alan tüm kaynaklar Creative Commons Alıntı-GayriTicari-Türetilemez 4.0 Uluslararası Lisansı ile lisanslanmıştır.
Platforms