Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Determination of the Particle Interactions -Rheology Suface Roughness Relationship for Dental Ceramics(Izmir Institute of Technology, 2007) Kes, Mürşide; Polat, HürriyetIn this study, relationship between particle interactions, rheology and surface roughness for dental ceramics was determined. For this purpose IPS Empress 2 veneer powder was chosen and characterized with XRD, SEM, EDS, Zeta Potential and Particle Size measurements.Particle interactions have been interpreted in the light of DLVO Theory for distilled water and electrolyte solutions at different concentrations (0.1, 0.25, 0.5, 0.75,1 M NaCl and CaCl2). The results indicated that interactions between particles change with electrolyte concentration and valency. Electrical Double Layer Thickness (Debye Length) compresses and Energy Barrier height decreases as electrolyte concentration and valency increase mean that there is agglomeration between particles. In order to understand the rheological properties of the system shear rate versus shear stress and shear rate versus viscosity graphs were interpreted for the same environmental conditions, distilled water and electrolyte solutions at different concentrations. It was obtained that at low electrolyte conditions particles formed agglomerates, however at high electrolyte conditions the system reached equilibrium where particles formed gel structures due to their non-Newtonian behaviour.The results obtained from rheological measurements were compared with the results obtained from AFM, profilometer and SEM measurements for the surfaces prepared with IPS Empress 2 veneer powder and it was concluded that in the presence of electrolytes (Na+ and Ca2+) surface roughness increased at low concentrations due to agglomeration of particles whereas surface roughness decreased at high concentrations most probably due to gelation in the system. Moreover, this situation was supported with contact angle measurements where contact angle mean values are high and ditributions are wide at low electrolyte concentrations while contact angle mean values are small and distributions are narrow at high concentrationsMaster Thesis Modeling of Collection of Non-Spherical Particle Assemblies by Liquid Droplets Under Potential Flow Conditions(Izmir Institute of Technology, 2006) Selvi, İlker; Doymaz, FuatA model, which explains the collection of non-spherical particle assemblies by liquid droplets, was constructed. The system was investigated under potential flow conditions. It was possible to generate the streamlines around the particles and droplets via potential flow theory. Therefore, the complexity coming from eddies and vorticity was eliminated. Non-spherical particles and agglomerated particles were modeled using equivalent diameter assumption due to the boundary layer, rotation, and oscillation behaviors of the particles. Collection probability was calculated as a function of three different collection mechanisms: collision, adhesion, and engulfment. The interaction forces between particles and droplets were divided into two groups as external and internal forces. The gravitational force and the drag force due to the uniform flow rate caused collection mechanisms. Van der Waals and Electrostatic interactions were investigated in order to explain adhesion and wetting mechanisms. Through simulations, we have found that particle and droplet diameters were the most influencing parameters on the collision mechanism. The engulfment possibility could be increased by adding surfactant to the liquid solution. The results of this model showed similarities with the other models in the literature, as well as with that of the experimental studies.