Master Degree / Yüksek Lisans Tezleri

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  • Master Thesis
    Processing and Characterization of Novel Graphene Containing Inks
    (01. Izmir Institute of Technology, 2022) Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Scientific and industrial community currently has an increased interest in printed electronics due to its many advantages. Metallic nanoparticles and conductive polymers are mostly used in the processing of commercial conductive inks. There is extensive research and development efforts on alternative materials as conductive fillers due to high cost, chemical instability in air and liquid media of widely used fillers. Graphene materials comprised of a single layer or multiple layers of graphene flakes have recently attracted great interest and used in applications as an excellent conductive filler due to its optical transparency, high conductivity, and flexibility. The aim of this MSc work was to prepare graphite and carbon black based conductive inks. Effects of graphite (G) to carbon black (CB) ratio and the use of exfoliation liquid on conductivity, rheology and particle size distribution were investigated for graphite containing conductive inks. Inks with the lowest resistance of 0.02 kΩ was obtained by using ball milling in N-metil-2-pirrolidon (NMP) as exfoliation liquid with the lowest particle size with an average of 18.0 µm. Inks prepared in this work showed shear thinning behavior independent of the exfoliation liquid used in their preparation. The highest thixotropy was measured in water exfoliated ink with 1801 Pa.s-1 and this dispersion had the lowest conductivity. A series of inks with different graphite to carbon black ratios were prepared under similar conditions. The lowest resistance 0.045 kΩ was determined at a graphite to carbon black ratio of 1 by using ethylene glycol as an exfoliation liquid. The use of ethylene glycol in commercial ink preparation may be advantageous due to its lower cost and environmentally friendly chemical properties. The highest degree of thixotropy and viscosity was measured in ink prepared at G/CB ratio of 0.5. This ink also had the highest resistance due to low amount of graphite compared to carbon black which indicated the critical importance of G/CB ratio.
  • Master Thesis
    Rheological Behavior of Carbon Black Inks
    (01. Izmir Institute of Technology, 2022) Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The printing ink industry is increasingly facing challenges in terms of high manufacturing costs and quality requirements. Rheological properties of the inks must be better understood for the development of production and application processes. Effects of pigment and dispersant content, varnish/solvent ratio, grinding medium, grinding time and storage period on rheological and printed optical properties were investigated for carbon black inks in this thesis work. The viscosity of the dispersant free ink was higher than inks with dispersant. The viscosity of the dispersant-free ink increased after three months storage whereas the viscosity of the dispersant-containing ink remained almost constant. Pigment content or V/S ratio increase resulted in higher viscosities. Grinding with 0.5 mm beads provided a finer size distribution and lower viscosities than ink ground with 0.8 mm beads. Longer grinding time increased the ink viscosities at pigment contents over 20 wt%. Thixotropy of dispersant free ink was determined to be about 12 times higher than 0.5 wt% dispersant containing ink. The thixotropy area of the 30 wt% pigment containing ink was determined to be five times higher than that of 25 wt% pigment containing ink. The thixotropy of the 25 wt% pigmented ink increased when the grinding time was changed from 30 to 60 minutes. Inks with coarser particle size distribution had higher thixotropy. Loss tangent (G''/G') at 10 Hz was used to create a correlation with color strength. Color strength of 14 out of 16 inks was determined higher with lower loss tangent values. Inks containing dispersant, higher pigment contents, varnish/solvent ratios close to one, increasing grinding time at higher pigment content increased the color strengths in printings.