Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Modelling of Pore Formation in Porous Materials(Izmir Institute of Technology, 2017) Ülker, Sevkan; Güden, Mustafa; Akdoğan, YaşarThe purpose of this thesis is to model the expansion behavior of aqueous slurries. Foamed or cellular material made using such method is known, especially in the concrete industry. What appears to be lacking in the literature is the knowledge of pore formation and pore growth in inorganic particles based on aqueous slurry systems that result in the formation of cellular structures. The motivation of this study is to provide a scientific view in identifying and explaining the critical parameters that govern the pore growth and expansion of such slurry based systems. Bubble growth and pore formation are also studied experimentally. Experimental results are used to compare with the empirical study conducted by Kanehira at al. (Kanehira, et al., 2013), and mathematical modeling of pore formation plotted with Wolfram Mathematica software. Experimental procedure consists of three types of aluminum and calcium ratios which provide information about bubble growth and pore formation. These types are 50% aluminum – 50% calcium hydroxide (50/50), 70% aluminum – 30% calcium hydroxide (70/30), and 80% aluminum – 20% calcium hydroxide (80/20). According to the results of studies, mathematical modeling system consists of the pressure difference between the inside and outside of a spherical bubble as the driving force for defining growth. While aluminum ratio increases, bubble growth rate decreases due to release of hydrogen gases which affect bubble expansion phenomenon. In the experimental and mathematical modeling, 50/50 ratio has maximum bubble growth rate compared to 70/30 and 80/20 ratios. The results of experimental and mathematical modeling suggest that viscosity is a very significant parameter which controls the bubble growth rate.Master Thesis Designing and Manufacturing of Porous Spinal Cages Using Ti6a14v Foamed Metal(Izmir Institute of Technology, 2009) Dizlek, Mustafa Eren; Güden, MustafaOpen cell Ti6Al4V foams with varying porosities (50, 60 and 70%) were prepared at sintering temperatures between 1200 and 1350 °C using ammonium bicarbonate particles (315 - 500 .m) as space holder. Two different biomedical grade commercial, gas atomized spherical Ti6Al4V powders were used to prepare foams. Powder 1 was in size range of between 45 - 150 .m and Powder 2 in size range of between 30 - 90 .m. The foams were sintered under argon atmosphere in a tightly enclosed tube furnace. The resulting cellular structure of the foams showed bimodal pore size distribution, comprising macro pores (300 - 500 .m) and micro pores (1 - 30 .m). Compression tests of foam samples have shown that increasing sintering temperature or decreasing porosity increased the elastic modulus, yield and compressive strength and failure strain. The improvement in the mechanical properties of foams prepared using smaller size Ti6Al4V powder with bimodal particle distribution were attributed to the increased number of sintering necks and contact areas between the particles. The foam prepared with optimum porosity, pore size and mechanical properties for bone in-growth was further used to produce prototype porous spinal cages which are widely used in spinal surgery for vertebrae fixation. The geometries and size of the prototype spinal cages were determined through the measurements taken from human vertebrae. The foams for spinal cage preparation were first prepared in the form of plates and then core-drilled using water jet based on the design geometrical parameters determined for each vertebra segment.