Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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2011 - 20172

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  • Master Thesis
    Investigation of Liquid Transport in Micro and Nanoscale Porous Media at Different Pore To Throat Size Ratios
    (Izmir Institute of Technology, 2017) Kalyoncu, Gülce; Barışık, Murat; Özkol, Ünver
    Extensive usage of micro/nanoscale porous media in various applications, require comprehensive understanding of fluid transport in those systems, such as in the unconventional oil-reservoirs, micro/nano-membrane technologies and lab-on-a-chip applications. The frequently employed transport calculations in literature do not consider any effects related to size or shape of the pore. Instead, dynamically similar flow systems assumed by the porosity of a given medium that an “ability of flow” definition named permeability is employed for a given solid/liquid couple based on the corresponding porosity. However, in such small-scales, liquid flow characteristics diverge from continuum behavior and non-equilibrium effects should be considered to estimate the transport. Furthermore, geometrical parameters of pore structures and networks should be considered, in addition to porosity, for a proper characterization. Hence, pore scale analyses of fluid flow were performed by solving Navier-Stokes equation numerica lly with finite element method in a representative elementary volume. Permeability values were calculated based on the Darcy’s Law, at different pore-to-throat-size ratios, porosities, and velocity slips whose range determined by a literature review. Permeability showed a strong dependence on pore-to-throat-size ratios, and slip conditions. Using the permeability of pores across a wide range of conditions, the Kozeny-Carman (KC) relation was re-considered. An extended phenomenological Kozeny Carman model to predict micro/nanoscale liquid transport as a function of porosity, pore-to-throat size ratio, and slip length was developed. The pore-to-throat-size ratio and slip effects were found substantial on transport, which was successfully predicted by developed model.
  • Master Thesis
    Use of Metal Templates for Microcavity Formation in Alumina
    (Izmir Institute of Technology, 2011) Balkan, Sırma; Akkurt, Sedat
    Alumina ceramics with microtunnels are produced by compressing submicron sized alumina powder and Ti, Cu or stainless steel wires in a metal die before firing the compacts at 1350oC for 4 hours. Diameters of wires ranged from 50 to 125 micrometers. Copper was found to completely melt and flow away from the compact leaving no trace of copper in alumina. Stainless steel diffused out into the alumina leaving few pores behind. Titanium, on the other hand, diffused into alumina at 20 to 30micrometers/hour and left plenty of Kirkendal porosity behind. The amount of porosity could have been increased further by applying intensive milling to the powder. But no milling was done in this study and hence a complete micro-tunnel was not obtained. The Kirkendal effect was observed to be effective in producing pores in the ceramic. Densification behavior of the ceramic was also investigated with a vertical dilatometer. Densities up to 93% were achieved in the ceramics. In some tests Ti metal plates were used as diffusion couples with alumina compacts. Similar diffusion behavior was observed with plates and wires.