Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis The Preparation and Characterization of Hydroxyapatite Bioceramic Implant Material(Izmir Institute of Technology, 2000) Çiftçioğlu, Rukiye; Harsa, Hayriye ŞebnemThe use of hydroxyapatite (HA) powders and ceramIcs as a biomaterial was investigated in this work. A commercial HA powder was used for the preparation of HA ceramics and the adsorption of Bovine Serum Albumin (BSA) onto HA has been investigated.The powder and the sintered ceramics were characterized by TGA, DT A, Optical Microscopy, Microhardness Tester, XRD, and FTIR.The sintering studies have shown that it was possible to prepare porous ceramics above 800°C and dense ceramics at 1200-1250°C range.The HA powder lost about 5.5% by weight during heat treatment up to 1000DC and 80% of this weight loss is due to adsorbed water.The particle size of the powder was determined to be submicron whereas the grain sizes of the 1250°C sintered ceramic was in the 1-5 /l um range.A maximum Vickers Hardness of 585 Hv was determined for the 1250°C sintered 97.2% dense ceramic.XRD patterns of the powder and the 1250°C sintered ceramic were identical and almost phase pure. A small CaO peak was detected in the samples which was believed to be remnants of the powder preparation process.The adsorption of BSA onto HA has been studied as a function of time, protein concentration, pH, ionic strength, and HA solids loading. Adsorption experiments were also conducted with commercial alumina and zirconia ceramic powders. Uptake curves have shown that the adsorption process was almost completed in less than ten minutes Adsorption isotherms 'at different pH ( 4.5-7.4) have been obtained and analyzed using the Langmuir model. The Langmuir parameters qm ( maximum amount of protein adsorbed, mg BSA/g HA) and K' (affinity constant, mllmg BSA) have been calculated. qm decreased from 119 to 61.3 with the increase in pH from 4.7 to 7.4. A maximum of 46.1 for K' was determined at pH.5.6 and K' had the lowest value of 3.5 at pH.7.4. Electrostatic attractions were held responsible for the K' maximum at pH.5.6 since HA and BSA surfaces are oppositely charged. The presence of a considerably high amount of BSA adsorption on the HA surface at pH.4.7 where the protein should have close to zero net charge was attributed to hydrophobic effects. The amount of adsorption at equilibrium in the 4.5-5.8 pH range was determined to be twice of that in the 6-8 pH range. Almost 100% of the protein was recovered with a HA solids loading of 750 mg HA/50 ml solution at equilibrium for an initial BSA concentration of I mg BSA/ml solution.Master Thesis Development of Dense Ceramic Tiles From Mixtures of Alumina Powders With Different Psd(Izmir Institute of Technology, 2004) Sütçü, Mücahit; Akkurt, Sedat; Akkurt, SedatIn Turkey, domestic alumina powders are generally used as an intermediate product in metallic aluminum production. Recently, its usage as a raw material for technical applications in ceramic industry has gained importance. The properties of domestic powders must be improved in order to be used in technical ceramic applications. Because these powders have coarse particle size with a high amount of sodium oxide as well as incomplete transformation to stable form. Therefore, sodium oxide that has been physically and chemically bound to aluminum oxide during Bayer process must be removed. In this study, sodium oxide (Na2O) content of the domestic powders was decreased to desirable levels (<0.15% Na2O) by hot washing treatments. These powders were calcined to transform into stable alpha form. X-Ray Diffraction (XRD) was preformed to analyze the calcined and as-received powders. Chemical analyses of the powders were done using Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). Domestic powders were ground. Scanning Electron Microscopy (SEM) was performed to analyze the morphology and particle size distributions of as-received and ground powders. Particle size distributions (PSD) were plotted using lineal intercept method. In this study, it was aimed to provide maximum packing by blending the powders in different combinations (binary and ternary powder blends). In addition to this, dense ceramic tiles were produced by blending different proportions of the powders that provide maximum packing. In this study, the improved domestic (coarse size-SKA and medium size-SEA) and superground (Alcoa CT3000SG) alumina powders with three different particle size distributions were used. The packing of binary (SEA-CT3000SG) and ternary (SKA-SEA-CT3000SG) blends were predicted by using the softwares, MXENTRY® and MIX10®. These softwares utilized the Dinger-Funk (DF) equation for predictions of packing. Prepared blends were uniaxially dry-pressed and sintered. Archimedes method was used to measure the density and porosity of the pellets. All results showed that the blend contained 100% superground alumina powders achieved almost full density (98%) at 1550C. The binary and ternary blends that contained a relatively higher proportion of fine alumina powders provided higher fired densities. In binary blends, if the proportion of SEA was up to 50%, porosity values of these blends increased. Also the effects of additives such as TiO2 and MnO2 on densification and mechanical properties of pellets were investigated. The additives provided higher fired densities between 91 and 99%. Vickers hardness tests were conducted to determine mechanical properties of the sintered pellets. The samples that contained relatively higher proportions of fine particles provided higher hardness values in a range of 1500 and 2100 kg.mm-2. Also, microstructural characterization of the pellets was done using SEM. Finally, the tiles at desired dimensions were produced based on the blends that give the highest density and hardness values. Porosity and density measurements, microstructural and mechanical characterizations of the tiles were carried out.Master Thesis Production of Ceramic Tiles by Using Marine Sludge Additives(Izmir Institute of Technology, 2006) Göl, Cem; Çiftçioğlu, MuhsinThe harbour sediment accumulated in time in the zmir Bay was investigated by a number of researchers from various aspects. These sediments called marine sludge in this thesis contain organics and heavy metals which pose an important environmental problem. Marine sludge removed from the harbor is required to be safely kept in some form. In this thesis, production of ceramic tiles by using marine sludge additives was investigated. The sludge is regarded as a suitable raw material for ceramic tile production because of its physical properties and chemical composition. After the sludge is removed from the harbor floor, it was subjected to a series of treatments such as washing, sieving, dewatering, drying and grinding. This treated marine sludge was pressed in the form of pellets and sintered in the 1000-1100 °C range. The treated, untreated and sintered marine sludge along with the separated shells present in marine sludge were characterized by a variety of techniques such as XRD, FTIR, and SEM-EDX. Marine sludge powders at different proportions (0-50 %) were blended via incorporation into a structural ceramic tile raw material. The mixtures were compressed, and then pellets were fired at temperatures in the 1000-1200 °C range with one-hour hold with a firing rate of 10 °C/min. The products were characterized for mechanical and microstructural properties. Marine sludge added tiles were observed to have higher compressive strength after firing at 1100 °C. The sludge addition caused a lower firing temperature for densification/vitrification of the pellets with higher pore content. Their densities and water absorption values were determined. The densities and water absorption of the tiles fired at 1100 °C was observed to decrease with increasing sludge addition. Leaching tests were performed by varying the leach solution pH and ground tile particle size for chemical durability of the products in the final part of the work. The leaching data have shown that heavy metals were immobilized in the vitrified ceramic structure. The results of this work indicated that blending marine sludge in to the ceramic powder mixtures in the 20-50% range was beneficial for tile production.