This study investigates the physical, mineralogical and chemical characteristics of a group of pottery sherds that are mostly Miletus-ware ceramics, belonging to the Early Ottoman period and excavated during 2003 season, from the The sherds examined are mostly characterized by cobalt-blue designs which are occasionally coupled with black, green and purple paintings. After grouping the sherds according to their stylistic and color differences / petrographic, X-ray diffraction, scanning electron microscope coupled with energy dispersive X-ray and Fourier Transform Infrared analyses were carried out for investigating the mineralogical and chemical properties. Most of the ceramic samples have slip and glaze on both sides. The glaze part is mostly fresh without any devitrification products. Bodies of the ceramics have tones of reddish yellow and/or red, indicating abundant amount of iron in their raw material. Grains consist mainly of metamorphic rock fragments (quartz-mica schist), quartz, feldspar, hornblende, hematite and biotite. Pyroxene, epidote, chert, muscovite, opaque minerals, chlorite are also encountered. Micritic calcite occurs in some of the pores. Ceramic bodies investigated are usually fine-grained and well-sorted. Clay raw material used for the production of the ceramics seems to be originated from a metamorphic source. Bodies usually show a low degree of vitrification with few exceptions, indicating a rather simple technology with non-uniform and low degree of firing, probably not exceeding 900&deg / C. Technological characteristics of the sherds examined do not seem to have changed much between 14th and 16th century.

MFI type zeolites, are the most widely studied zeolites for membrane separations. Conventionally, zeolite membranes are prepared in batch systems by hydrothermal synthesis in autoclaves. This method has several disadvantages for use in industrial scale for the synthesis of membranes with large areas and complex geometries that are commonly used in membrane modules. The objective of this study is to prepare MFI type zeolite membranes on tubular alumina supports in a continuous system where the synthesis solution is circulated through the tubular supports. Syntheses were carried out using clear solutions, at atmospheric pressure and at temperatures below 100&deg / C. The membranes were characterized by N2, SF6, n-butane and isobutane permeances, X-ray diffraction and scanning electron microscopy. A 2-&amp / #956 / m membrane was synthesized using the composition 80SiO2: 16TPAOH: 1536H2O at 95&deg / C in the continuous system. The membrane showed N2 permeance of 4.4 x 10-7 mol/m2.s.Pa and N2/SF6 selectivity of 11. The membrane synthesized in the batch system showed a N2 permeance of 3.4 x 10-7 mol/m2.s.Pa and a N2/SF6 selectivity of 27. Both membranes showed n-butane/isobutane mixture (50%-50%) selectivities of about 6 at temperatures of 150 and 200&deg / C. Among many zeolite membranes reported in literature, these membranes are one of the few zeolite membranes synthesized in a flow system and the first MFI type membranes synthesized in a continuous flow system with circulation of the synthesis solution. The permeances and selectivities of the membranes synthesized in the continuous system are comparable with the MFI type membranes synthesized in batch systems in literature.

Clinoptilolite is the most abundant zeolite mineral in nature. In this study a reproducible synthesis recipe for clinoptilolite was established and the limits of the crystallization field were developed by changing synthesis parameters such as temperature, composition and the nature of reactants. Clinoptilolite was reproducibly synthesized as a pure phase and in high yield at 140oC using a benchmark batch composition of 2.1 Na2O:Al2O3:10SiO2:110.1 H2O. Clinoptilolite was crystallized from 10wt% or 28wt% seeded systems while it was not formed if no seeds were present. Clinoptilolite was also crystallized as a pure phase when the cation in the benchmark batch composition was Na,K mixture, or when alkali salts such as carbonates or chlorides were used besides alkali hydroxides, or when the SiO2/Al2O3 ratio was in the range of 10-12. Clinoptilolite was still crystallized as a single phase when alkali hydroxides in the batch were reduced by 20%. With the benchmark batch composition, clinoptilolite was crystallized in pure phase form at 100oC, 120oC, 140oC and 160oC while synthesis at 175oC resulted in the formation of pure mordenite. At 140oC clinoptilolite was crystallized together with Linde L when cation in the benchmark composition is only potassium. Phillipsite crystallized together with clinoptilolite at SiO2/Al2O3 ratio of 8 to 9. At SiO2/Al2O3 ratios of 6 or 4, phillipsite or analcime was formed as pure phase respectively. When the alkali hydroxides in the batch was increased by 20%, sanidine was formed. Use of reactive aluminosilicate gels enhanced the formation of clinoptilolite while attempts to use mineral raw materials were unsuccessful. For both Na and (Na,K)-clinoptilolite, Si/Al ratio of products were greater than four. Thermal stability of synthetic clinoptilolites were comparable with natural clinoptilolite and potassium ion increased thermal stability of clinoptilolite.

The effect of seeding on the properties of alumina supported MFI membranes was investigated in this study. Membranes were synthesized from clear solutions with a molar batch composition of TPAOH:9.80SiO2:0.025NaOH:0.019Al2O3: 602.27H2O:39.16C2H5OH on bare and seeded alumina supports at 130oC in autoclaves. The amount of seed on the support surface was changed between 0.6 mg/cm2 and 6.9 mg/cm2 by vacuum seeding method, which provided uniform and closely packed seed layers. Membranes were characterized by XRD and SEM, and by measuring single gas permeances of N2, SF6, n-C4H10 and i-C4H10. The quality of membranes was evaluated on the basis of N2/SF6 ideal selectivity. Membranes, which showed N2/SF6 ideal selectivity higher than 40, were considered to be good quality, comprising few defects. Good quality membranes were also used to separate butane isomers. Membranes synthesized on seeded supports had compact and uniform MFI layer if the seed amount is less than 1.0 mg/cm2 on the support surface. Membranes that were synthesized on the supports coated with higher amount of seed crystals showed an asymmetric structure with a dense and uniform MFI layer at the top, the support at the bottom and a seed layer between. Half of the membranes synthesized on seeded supports had N2/SF6 ideal selectivity higher than 40. These membranes exhibited n-C4H10/i-C4H10 separation selectivities between 5 and 27 and 8 and 21 at room temperature and at 200oC, respectively. High ideal and separation selectivities showed that membranes did not include non-zeolitic pores. Membranes synthesized on bare support had non-uniform MFI layer. Those membranes showed N2/SF6 ideal selectivities below Knudsen selectivity, indicating the existence of large non-zeolitic pores in the MFI layer.

No description available.

No description available.

Specimens of ZrB2 containing various concentrations of B4C, SiC, TaB2, and TaSi2 were pressureless-sintered and post-hot isostatic pressed to their theoretical densities. Oxidation resistances were studied by scanning thermogravimetry over the range 1150 - 1550 degree C. SiC additions improved oxidation resistance over a broadening range of temperatures with increasing SiC content. Tantalum additions to ZrB2-B4C-SiC in the form of TaB2 and/or TaSi2 increased oxidation resistance over the entire evaluated spectrum of temperatures. TaSi2 proved to be a more effective additive than TaB2. Silicon-containing compositions formed a glassy surface layer, covering an interior oxide layer. This interior layer was less porous in tantalum-containing compositions. The oxidation resistances of ZrB2 containing SiC, TaB2, and TaSi2 additions of various concentrations was studied using isothermal thermogravimetry at 1200, 1400, and 1500 degree C, and specimens were further characterized using x-ray diffraction and electron microscopy. Increasing SiC concentration resulted in thinner glassy surface layers as well as thinner ZrO2 underlayers deficient in silica. This silica deficiency was argued to occur by a wicking process of interior-formed borosilicate liquid to the initially-formed borosilicate liquid at the surface. Small (3.32 mol%) concentrations of TaB2 additions were more effective at increasing oxidation resistance than equal additions of TaSi2. The benefit of these additives was related to the formation of zirconium-tantalum boride solid solution during sintering, which during oxidation, fragmented into fine particles of ZrO2 and TaC. These particles resisted wicking of their liquid/glassy borosilicate encapsulation, which increased overall oxidation resistance. With increasing TaB2 or TaSi2 concentration, oxidation resistance degraded, most egregiously with TaB2 additions. In these cases, zirconia dendrites appeared to grow through the glassy layers, providing conduits for oxygen migration.

In this thesis different aspects of calcium-aluminate (CA) as biomaterial are presented. Calcium aluminate is a chemically bonded ceramic with inherent properties making it suitable for use as biomaterial in some applications. In this thesis the emphasis is put on the basic chemical, physical and mechanical properties that may be achieved using the CA system as well as synthesis of the CA raw material. The basis for using CA in any application is the synthesis of the raw material. Different synthesis routes for producing CA are presented with focus on high temperature routes and the micro-structural and phase development during synthesis. As a base for further understanding of the CA properties a thorough outline of the reaction chemistry for CA is presented also including a description of how the reactions may be controlled and how formulations can be designed. The surface reactions of CA when subjected to simulated body fluid showed that CA is in vitro bioactive. An in vivo study in teeth also indicates that CA produces apatite at the tooth material interface. Dental materials are subjected to a harsh environment in the mouth with high mechanical forces, erosion and thermal changes. Also the demands on precise handling characteristics are high. For these reasons the in vitro evaluation of physical and mechanical properties are important. In this work several mechanical and physical properties of Ca-based formulations for dental applications has been tested using different methods. Some attention is also put on the specific characteristics of CA and the difficulties that arise when new material classes needs to be tested according to consensus standard methods. Finally studies on a CA-based formulation intended for Vertebroplasty is presented. The studies include basic mechanical properties as well as testing the material in an in vitro model utilising synthetic cancellous bone.

Background Surface treatments and irregularities in the surfaces may affect the fracture of ceramics. The effects of various treatments on the surface texture of different types of ceramic cores/substructures was therefore qualitatively, quantitatively and numerically evaluated. Since fractures in ceramics are not fully understood, the fracture behavior in dental ceramic core/substructures was also studied using both established laboratory methods and newly developed numerical methods. Methods The surfaces of dental ceramic cores/substructures were studied qualitatively by means of a fluorescence penetrant method and scanning electron microscopy, quantitatively evaluated using a profilometer and also numerical simulation. In order to study fracture in zirconia-based fixed partial denture (FPD) frameworks, fractographic analysis in combination with fracture tests and newly developed two-dimensional (2D) and three-dimensional (3D) numerical modeling methods were used. In the numerical modeling methods, the heterogeneity within the materials was described by means of the Weibull distribution law. The Mohr–Coulomb failure criterion with tensile strength cut-off was used to judge whether the material was in an elastic or failed state. Results Manual grinding/polishing could smooth the surfaces on some of the types of dental ceramic cores/substructures studied. Using the fluorescence penetrant method, no cracks/flaws apart from milling grooves could be seen on the surfaces of machined zirconia-based frameworks. Numerical simulations demonstrated that surface grooves affect the fracture of the ceramic bars and the deeper the groove, the sooner the bar fractured. In the laboratory tests the fracture mechanism in the FPD frameworks was identified as tensile failure and irregularities on the ceramic surfaces could act as fracture initiation sites. The numerical modeling codes allowed a better understanding of the fracture mechanism than the laboratory tests; the stress distribution and the fracture process could be reproduced using the mathematical methods of mechanics. Furthermore, a strong correlation was found between the numerical and the laboratory results. Conclusion Based on the findings in the current thesis, smooth surfaces in areas of concentrated tensile stress would be preferable regarding the survival of ceramic restorations, however, the surfaces of only some of the ceramic cores/substructures could be significantly affected by manual polishing. The newly developed 3D method clearly showed the stress distribution and the fracture process in ceramic FPD frameworks, step by step, and seems to be an appropriate tool for use in the prediction of the fracture process in ceramic FPD frameworks.

The expanding potential for the dissemination and archiving of aphorisms is explored in this practice-based research thesis. An aphorism is a short statement that communicates an insight about the world (and can sometimes function as a guide to action). Eric McLuhan, interviewed in Signs of the Times: The History of Writing (Goëss Video, 1996), suggests that the future of the book is the aphoristic statement. Aphoristic knowledge has traditionally been transmitted through texts and through libraries, but this project brings into play various modes of recirculating aphoristic texts using contemporary distribution networks and digital media such as moving image, projection on to urban screens, artists’ books, archival digital photography and glazed ceramics. Texts ‘virally inhabit’ a number of sites and languages in a series of works situated in the interdisciplinary context of contemporary text art and artists’ books. The sayings rejoin the cultural river of ideas in local and international incarnations. Practice-based work (80%) and exegesis (20%)