Magnetite (Fe3O4) thin films were prepared by a sol-gel process in which, a solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. Xerogel films were obtained by drying the coated films at 110 &deg / C. The films were sintered between 300 &deg / C and 450 &deg / C in order to observe the phases existing in the films at different temperatures. Coating solution showed Newtonian behaviour and viscosity was found as 0.0215 Pa.s. DTA analysis showed that, sintering temperature should be selected between 291 &deg / C and 350 &deg / C in order to produce magnetite thin films. Prepared magnetite thin films were characterized by XRD, SEM, AFM, TEM, VSM and UV-Vis spectrometer. In-plane grazing angle diffraction studies showed that magnetite phase was present upon sintering the films at 300 &deg / C. From the SEM studies, it was shown that films with defect free surfaces were obtained and by cross section studies, thickness of the films was found as ~10-200 nm. AFM images showed that no cracks or any other defects on the film surface were present. TEM results proved the existence of single phase magnetite in the produced films. UV-Vis spectrum results showed that transmittance of the films increases with decreasing sintering temperature and increasing spinning rate. Up to 96% transmittance was observed between the wavelengths of 900-1100 nm. Magnetic properties of magnetite thin films were also examined by VSM (Vibrating Sample Magnetometer) and ferromagnetic behaviour was shown using VSM data.

Albite (Na-feldspar) and orthoclase (K-feldspar) are the major feldspar minerals used in the production of glass and ceramics. They are found together with impurities like biotite, muscovite, quartz and rutile which are not desired for ceramics and glass industries. Therefore, these have to be removed to make the ore available for industrial use. In order to shed light on the actual feldspar ores, in this study / the flotation characteristics of albite, biotite, muscovite, orthoclase, quartz and rutile were investigated separately in their pure forms. In the investigation, the electrokinetic potential measurements and micro-flotation studies have been carried out to get information about their flotation characteristics under the effect of three different collectors, Aero 704, Aero 3000C and Aero 825, and the pH of the medium. The flotation recoveries were found to be pH dependent and the effective between the pH range of 7.0 and 11.5 in the presence of Aero 704. In the case of flotation with Aero 3000C, the recoveries reached up to 95.0% at certain concentrations and pH values and decreased sharply below pH 3.0 and above pH 9.5 for all the minerals tested. In the presence of Aero 825, the flotation recoveries of the minerals except for rutile, were found to be insufficient even with its highest concentration. In order to evaluate the adsorption mechanism of the collectors, Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses were carried out. From the AFM results it might be deduced that the behavior of Aero 3000C and Aero 825 was found to be almost similar for biotite and muscovite as monolayer adsorption and for the remaining minerals, albite, orthoclase, quartz and rutile, as monolayer and bilayer adsorption together. In the case of Aero 704, for albite and orthoclase, the adsorption of the collector might be the reason for monolayer and bilayer formation on their surfaces. The strength of the interaction of the collectors on the mineral surfaces was followed by FTIR analyses before and after acetone washing. The interaction of all the collectors was found to be weak in the case of albite, orthoclase, quartz and rutile whereas the interaction of Aero 704 and Aero 3000C was found to be strong in the case of biotite and muscovite.

The aim of this study is to investigate the deterioration in mechanical integrity of the collagen network in bovine bone with aging, which are related to fracture toughness. Age-related changes in collagen molecular structures formed by non-enzymatic glycation were examined and indentation fracture technique was used as a method for measuring the microstructural toughness of cortical bone. Microcrack propagation characteristics of bone for fragility were also studied. Young and old group of bovine cortical bone specimens were grouped into 2 as ribosylated and non-ribosylated which were rested in solutions for four weeks. Series of indentations were made on bone specimen groups for each of five masses 10g, 25g, 50g, 100g and 200g for 10 sec to detect the effect of applied indentation load. The applied load was increased to 300g, 500g, 1000g and 2000g for 10 sec to be able to make microcracks. Series of indentations were made on bone specimen groups for each of five durations 5sec, 10sec, 20sec, 30sec for 100g to study the effect of indentation duration. Specimens were examined in the wet and dry state while studying the factors effecting microhardness measurement. Microhardness values measured by 10g of load for 10sec were indifferent between the ribosylated and non-ribosylated groups in the young and old bovine bone pointing that this load is not indicative of the structural collagen changes. Loads of 25g, 50g, 100g and 200g for 10 sec were able to differ ribosylated bone from non-ribosylated bone for the young and old bovine bones. Degree of microhardness increased with increased incubation period. Microhardness of dry specimens being either ribosylated or non-ribosylated were found to be statistically higher than wet specimens in young and old bone except for 10g for 10sec. It has been shown that the calculated fracture toughness measured by the indentation method is a function of indentation load. Additionally, effect of indentation size might have resulted in a higher toughness measurement for higher indent loads with longer cracks even if the toughness is not actually higher.Methods using indentation technique has difficulty in relating the resistance to crack growth to the Mode I fracture toughness definition.Indentation fracture toughness allows sampling only one point on the R&shy / curve methods and was not considered as successful for assessing materials with rising R&shy / curve. Toughness is ranked incorrectly among riboslated and non-ribosylated bovine bone by this technique. Presence of extrinsic toughening mechanisms including crack bridging due to uncracked ligaments and collagen fibers were directly observed by scanning electron microscope. Ribosylated bone was found to have lower number of collagen bridging compared ton on-ribosylated bovine bone.As a summary, indentation fracture method by Vickers indentation in bone is a method for measuring the fracture toughness.

The influence of drying parameters namely residence time before drying, drying temperature, drying time, relative humidity, and slip recipe on the drying rate of slip cast sanitary wares, predominantly lavatories and toilet closets, was studied. The drying temperatures were changed from 80 oC to 110 oC with an increment of 10 oC. The drying time was changed from 10 to 7 h with a decrease of 1 hour. Relative humidity of the environment was changed from 60 to 75 %. The percent weight loss, percent residual moisture and the percent shrinkage of the samples were determined by weighing and measuring the samples before and after the tests. The percent weight loss was within the range of 6.5 to 6.6 % after holding the as cast samples for 6 hours at ambient casting shop conditions while it was within the range of 17.96 to 18.10 % when subsequently dried for 10 hours at 110 oC in the dryer. The percent shrinkage was within the range of 2.9 - 3.0 % after holding the as cast samples 6 h at ambient laboratory conditions. No shrinkage was observed in the sample when it was subsequently dried for 10 hours at 110 oC in the dryer. Optimum moisture content of dried wares was obtained after drying for 8 hours at 100 oC in the dryer. It has been seen that the relative humidity of the dryer at the beginning of the drying should be lower than 75 %. As the non-plastic content in the recipe of the sanitary ware slip increased, drying shrinkage and residual moisture content decreased. The results of this study showed that through increasing the residence time up to 6h with a casting shop environment of approximately 30 oC and 60 % relative humidity, the drying time could be safely reduced from 10 h to 8 h with a drying temperature of 100 oC for the test plates. The same approach can be used for more complex shapes, e.g., WC closets, basins, tanks etc. in EczacibaSi Vitra plant. Once the drying time was reduced, the amount of natural gas per ware would be reduced to a certain extent. Aside from that the reduction in the drying time would increase the quantity of the drying cycles per week so that more wares could be dried. When all these observations were taken into account, this thesis study could also be utilized by other sanitary ware producing companies whose processes require slip cast drying.