Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Preparation and Rheological Characterization of Calcium Silicate/Aluminate Based Cementitious Inks(01. Izmir Institute of Technology, 2022) Keleş, Pelin; Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; Şahin, Erdem; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIncreasing number of bone tissue transplant operations conducted every year has increased the use of bone grafts and bone replacement materials. The commonly employed treatment methods however have several disadvantages. Bone tissue engineering scientists has been conducting intensive research on 3D scaffolds to overcome these disadvantages. Although different materials such as hydrogels, polymers, and metals are heavily used for scaffolds the most suitable material is agreed to have a ceramic/inorganic structure since they have a similar composition to the natural bone. The perfect material for 3D scaffolds formation however has not been found due to the rheological limits of inks/suspensions used in this versatile consolidation technique. Tricalcium aluminate (C3A) and tricalcium silicate (C3S) cement powders were produced with three different marble dust sources and two different silica sources in this work. The produced powders were combined with additives such as magnesium sulfate (MgSO4), hydroxyethyl cellulose (HEC), gluconic acid (GA), polyethylene glycol (PEG), trisodium sulfate (TSC) and sodium dodecyl sulfate (SDS) for the optimization of 3D printing cementitious inks/suspensions through the investigation of their rheological properties. The optimum firing temperature for C3A powder was determined to be 1300oC with 2 hours hold period while it was found to be 1400oC for 4 hours for C3S powder preparation with rapid cooling to room temperature. The use of C3A suspensions in 3D printers necessitate the presence of 1M MgSO4 which acts as a retarder; 2% HEC and 1% PEG for increasing stability; and finally, 10% marble dust and silica. C3S suspensions should contain 1M gluconic acid, 2.5% HEC, 1% PEG, 0.1M trisodium citrate and 0.1M sodium dodecyl sulfate. Capillary rheometer results are compatible with oscillating rheometer results and have been the subject of a preliminary study for 3D printers in this thesis work.Master Thesis Synthesis and Characterization of Hydroxyapatite-Alumina Biocomposites(Izmir Institute of Technology, 2006) Şahin, Erdem; Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThree component hydroxyapatite-alumina-zirconia composite presents a promising candidate material for bone replacement implants. Two methods were employed to synthesize the composite that is expected to have high bioactivity, high strength and high chemical stability in physiologic environment. Wet mixing and heterogeneous precipitation methods were used for the synthesis. Commercial hydroxyapatite, alum ina and yttria stabilized zirconia were mixed in varying proportions and obtained powders were sintered upto 1300 °C subsequent to dry pressing at 160MPa. An optimum composition of 10-20-70 volume percent zirconia, alumina and hydroxyapatite respectively was found to present the most suitable proportion in terms of sinterability and phase purity. -tricalcium phosphate formation at temperatures higher than 1150 °C was found to be the only source of impurity phase in the material.Heterogeneous precipitation method was applied to synthesize a composite material with a functionally graded structure. The three components were aimed to be coated on one another, zirconia (TZ-3Y) being the core, alumina being the intermediate layer and hydroxyapatite being the outer shell. The bulk composite was expected to have both enhanced mechanical properties and enhanced phase purity due to separation of two reactive phases, hydroxyapatite and zirconia by the alumina layer. The coating was done in two steps using urea as the precipitant, aluminum sulfate as the Al3+ source, calcium nitrate as the Ca2+ source and ammonium phosphate as the P source.Precipitation of aluminum hydroxides on TZ-3Y particulates and precipitation of calcium hydroxides as a nucleation point for hydroxyapatite on cores were facilitated through decomposition of urea above 85 °C in aqueous media. Particle size, distribution and morphology were monitored for alumina coated zirconia samples prepared with varying Al2(SO4)/Zirconia and urea/Al2(SO4) molar ratios. The sample prepared with stoichiometric Al2(SO4)/Zirconia ratio and urea/Al2(SO4) ratio 10 exhibited the most suitable composition and morphology for hydroxyapatite coating. Samples synthesized in the first step were used as cores for hydroxyapatite coating.