<p>Nano-powders of BaTiO₃, SrTiO₃, Ba_0.6Sr_0.4TiO₃, a mixture of the composition (BaTiO₃)_0.6(SrTiO₃)_0.4 with particle sizes in the range of 60 to 80 nm, and Bi₄Ti₃O₁₂ with an average particle size of 100 nm were consolidated by spark plasma sintering (SPS). The kinetics of reaction, densification and grain growth were studied. An experimental procedure is outlined that allows the determination of a “kinetic window” within which dense nano-sized compacts can be prepared. It is shown that the sintering behaviour of the five powders varies somewhat, but is generally speaking fairly similar. However, the types of grain growth behaviour of these powders are quite different, exemplified by the observation that the kinetic window for the (BaTiO₃)_0.6(SrTiO₃)_0.4 mixture is 125 ^oC, ~75 ^oC for Bi₄Ti₃O₁₂, ~25^oC for BaTiO₃ and SrTiO₃, while it is hard to observe an apparent kinetic window for obtaining nano-sized compacts of Ba_0.6Sr_0.4TiO₃. During the densification of the (BaTiO₃)_0.6(SrTiO₃)_0.4 mixture the reaction 0.6BaTiO₃+0.4SrTiO₃ → Ba_0.6Sr_0.4TiO₃ takes place, and this reaction is suggested to have a self-pinning effect on the grain growth, which in turn explains why this powder has a large kinetic window. Notably, SPS offers a unique opportunity to more preciously investigate and monitor the sintering kinetics of nano-powders, and it allows preparation of ceramics with tailored microstructures.</p><p>The dielectric properties of selected samples of (Ba, Sr)TiO₃ ceramics have been studied. The results are correlated with the microstructural features of these samples, <i>e.g.</i> to the grain sizes present in the compacts. The ceramic with nano-sized microstructure exhibits a diffuse transition in permittivity and reduced dielectric losses in the vicinity of the Curie temperature, whereas the more coarse-grained compacts exhibit normal dielectric properties in the ferroelectric region.</p><p>The morphology evolution, with increasing sintering temperature, of bismuth layer-structured ferroelectric ceramics such as Bi₄Ti₃O₁₂ (BIT) and CaBi₂Nb₂O₉ (CBNO) was investigated. The subsequent isothermal sintering experiments revealed that the nano-sized particles of the BIT precursor powder grew into elongated plate-like grains within a few minutes, via a dynamic ripening mechanism.</p><p>A new processing strategy for obtaining highly textured ceramics is described. It is based on a<i> directional dynamic ripening mechanism</i> <i>induced by superplastic deformation</i>. The new strategy makes it possible to produce a <i>textured</i> microstructure within minutes, and it allows production of textured ferroelectric ceramics with tailored morphology and improved physical properties.</p><p>The ferroelectric, dielectric, and piezoelectric properties of the textured bismuth layer-structured ferroelectric ceramics have been studied, and it was revealed that all textured samples exhibited anisotropic properties and improved performance. The highly textured Bi₄Ti₃O₁₂ ceramic exhibited ferroelectric properties equal to or better than those of corresponding single crystals, and much better than those previously reported for grain-orientated Bi₄Ti₃O₁₂ ceramics. Textured CaBi₂Nb₂O₉ ceramics exhibited a very high Curie temperature, <i>d</i><i>33</i>-values nearly three times larger than those of conventionally sintered materials, and a high thermal depoling temperature indicating that it is a very promising material for high-temperature piezoelectric applications.</p>

<p>The technique of Nanoindentation <em>in situ</em> Transmission Electron Microscope has been implemented on a Philips CM20. Indentations have been performed on Si and Sapphire (<em>α-Al</em><em>2</em><em>O</em><em>3</em>) cut from wafers; Cr/Sc multilayers and <em>Ti</em><em>3</em><em>SiC</em><em>2</em> thin films. Different sample geometries and preparation methods have been evaluated. Both conventional ion and Focused Ion Beam milling were used, with different ways of protecting the sample during milling. Observations were made of bending and fracture of samples, dislocation nucleation and dislocation movement. Basal slip was observed upon unloading in Sapphire. Dislocation movement constricted along the basal planes were observed in <em>Ti</em><em>3</em><em>SiC</em><em>2</em>. Post indentation electron microscopy revealed kink formation in <em>Ti</em><em>3</em><em>SiC</em><em>2</em> and layer rotation and slip across layers in Cr/Sc multilayer stacks. Limitations of the technique are presented and discussed.</p>

During the fall of 1973, the newly formed (American) Institute of Nautical Archaeology conducted its first systematic underwater survey of the southwestern coast of Turkey with the goal of locating the first shipwreck to be subsequently excavated by the Institute. Of the 18 wreck sites identified during the survey, a site off Sheytan Deresi (Devil’s Creek) proved to be the one that attracted George Bass, director of the survey, as most meriting further study. During the excavation that followed in September and October 1975, the site produced a number of complete and fragmentary ceramic vessels that formed the main artifact assemblage. Although the ceramic vessels brought to light at Sheytan Deresi have been studied by George Bass, Roxani Margariti and others since the 1975 excavation, locating precise parallels for the assemblage proved a difficult task and resulted in a less than full understanding of the site. The following thesis represents a renewed effort to answer a number of questions still surrounding the Sheytan Deresi site. In addition to expanding the extensive search for parallels undertaken by Bass and Margariti, recent research has involved a number of scientific analyses, including petrographic analysis of the ceramic assemblage, luminescence dating of ceramic fragments, and elemental examination of the fabric through neutron activation analysis and energy dispersive spectroscopy. The use of three-dimensional modeling has been adopted for the purposes of site interpretation. Although the impact of this more holistic approach cannot be entirely foreseen at this time, a number of interesting hypotheses regarding the site can now be suggested. It appears that the ceramic assemblage, which is now conclusively of a single origin, may be of a specialized maritime nature, and likely belongs to the Middle Bronze Age, reminiscent of, but entirely similar to, regional types of Anatolian and Cretan vessels. These tentative conclusions, as well as an examination of the site itself, suggest that the (Minoanizing) ceramic assemblage of Sheytan Deresi stood witness to a fairly small Middle Bronze Age coastal trading vessel that capsized rounding a dangerous cape, not far from its point of origin. We are still not in a position to fully comprehend the wrecking event that took place at Sheytan Deresi, but we are now firmly on course towards reaching that objective.

A number of charred surface residues, adhering to ceramic containers, were obtained from various coastal and inland sites in north-west Europe dating from the sixth to the fourth millennium cal bc. In order to investigate the use of these vessels and in particular to identify any marine products, the residues were subjected to carbon and nitrogen stable isotope analysis. Variation in carbon isotope ratios between different samples indicated that some vessels may have been used to process marine products. This analysis was corroborated by specific identification of aquatic products following structural and isotopic characterization of lipids extracted from selected samples.

Spark Plasma Sintering (SPS) is a promising rapid consolidation technique that allows a better understanding and manipulating of sintering kinetics and therefore makes it possible to obtain Si3N4-based ceramics with tailored microstructures, consisting of grains with either equiaxed or elongated morphology. The presence of an extra liquid phase is necessary for forming tough interlocking microstructures in Yb/Y-stabilised α-sialon by HP. The liquid is introduced by a new method, namely by increasing the O/N ratio in the general formula RExSi12-(3x+n)Al3x+nOnN16-n while keeping the cation ratios of RE, Si and Al constant. Monophasic α-sialon ceramics with tailored microstructures, consisting of either fine equiaxed or elongated grains, have been obtained by using SPS, whether or not such an extra liquid phase is involved. The three processes, namely densification, phase transformation and grain growth, which usually occur simultaneously during conventional HP consolidation of Si3N4-based ceramics, have been precisely followed and separately investigated in the SPS process. The enhanced densification is attributed to the non-equilibrium nature of the liquid phase formed during heating. The dominating mechanism during densification is the enhanced grain boundary sliding accompanied by diffusion- and/or reaction-controlled processes. The rapid grain growth is ascribed to a dynamic ripening mechanism based on the formation of a liquid phase that is grossly out of equilibrium, which in turn generates an extra chemical driving force for mass transfer. Monophasic α-sialon ceramics with interlocking microstructures exhibit improved damage tolerance. Y/Yb- stabilised monophasic α-sialon ceramics containing approximately 3 vol% liquid with refined interlocking microstructures have excellent thermal-shock resistance, comparable to the best β-sialon ceramics with 20 vol% additional liquid phase prepared by HP. The obtained sialon ceramics with fine-grained microstructure show formidably improved superplasticity in the presence of an electric field. The compressive strain rate reaches the order of 10-2 s-1 at temperatures above 1500oC, that is, two orders of magnitude higher than that has been realised so far by any other conventional approaches. The high deformation rate recorded in this work opens up possibilities for making ceramic components with complex shapes through super-plastic forming.

Nano-powders of BaTiO3, SrTiO3, Ba0.6Sr0.4TiO3, a mixture of the composition (BaTiO3)0.6(SrTiO3)0.4 with particle sizes in the range of 60 to 80 nm, and Bi4Ti3O12 with an average particle size of 100 nm were consolidated by spark plasma sintering (SPS). The kinetics of reaction, densification and grain growth were studied. An experimental procedure is outlined that allows the determination of a “kinetic window” within which dense nano-sized compacts can be prepared. It is shown that the sintering behaviour of the five powders varies somewhat, but is generally speaking fairly similar. However, the types of grain growth behaviour of these powders are quite different, exemplified by the observation that the kinetic window for the (BaTiO3)0.6(SrTiO3)0.4 mixture is 125 oC, ~75 oC for Bi4Ti3O12, ~25oC for BaTiO3 and SrTiO3, while it is hard to observe an apparent kinetic window for obtaining nano-sized compacts of Ba0.6Sr0.4TiO3. During the densification of the (BaTiO3)0.6(SrTiO3)0.4 mixture the reaction 0.6BaTiO3+0.4SrTiO3 → Ba0.6Sr0.4TiO3 takes place, and this reaction is suggested to have a self-pinning effect on the grain growth, which in turn explains why this powder has a large kinetic window. Notably, SPS offers a unique opportunity to more preciously investigate and monitor the sintering kinetics of nano-powders, and it allows preparation of ceramics with tailored microstructures. The dielectric properties of selected samples of (Ba, Sr)TiO3 ceramics have been studied. The results are correlated with the microstructural features of these samples, e.g. to the grain sizes present in the compacts. The ceramic with nano-sized microstructure exhibits a diffuse transition in permittivity and reduced dielectric losses in the vicinity of the Curie temperature, whereas the more coarse-grained compacts exhibit normal dielectric properties in the ferroelectric region. The morphology evolution, with increasing sintering temperature, of bismuth layer-structured ferroelectric ceramics such as Bi4Ti3O12 (BIT) and CaBi2Nb2O9 (CBNO) was investigated. The subsequent isothermal sintering experiments revealed that the nano-sized particles of the BIT precursor powder grew into elongated plate-like grains within a few minutes, via a dynamic ripening mechanism. A new processing strategy for obtaining highly textured ceramics is described. It is based on a directional dynamic ripening mechanism induced by superplastic deformation. The new strategy makes it possible to produce a textured microstructure within minutes, and it allows production of textured ferroelectric ceramics with tailored morphology and improved physical properties. The ferroelectric, dielectric, and piezoelectric properties of the textured bismuth layer-structured ferroelectric ceramics have been studied, and it was revealed that all textured samples exhibited anisotropic properties and improved performance. The highly textured Bi4Ti3O12 ceramic exhibited ferroelectric properties equal to or better than those of corresponding single crystals, and much better than those previously reported for grain-orientated Bi4Ti3O12 ceramics. Textured CaBi2Nb2O9 ceramics exhibited a very high Curie temperature, d33-values nearly three times larger than those of conventionally sintered materials, and a high thermal depoling temperature indicating that it is a very promising material for high-temperature piezoelectric applications.

Dental restorative materials interact with their surrounding oral environment. Interaction factors can be release of toxic components and/or effects on biofilm formation and gingiva. In the end of the nineties, a calcium aluminate cement (CAC) was manufactured as a “bioceramic” alternative to resin composite. Dental ceramics are considered to be chemically stable and not to favour dental biofilm formation. Since the influence of aged, resin-bonded ceramic coverages is not fully investigated and the effect of CAC restorations on the dental biofilm formation and gingival response is unknown, those issues were evaluated in this thesis. With or without oral hygiene, in clinical trials including cervical surfaces of CAC, and approximal surfaces of a leucite-reinforced bonded ceramic; biofilm growth, presence of caries-associated bacteria, clinical expressions of gingivitis, the amounts of gingival crevicular fluid (GCF) and its levels of IL-1α, IL-1β and IL-1 ra were investigated in comparison with resin composite and enamel. In addition, the unknown cytotoxic effect of specimens of CAC on fibroblasts was assessed in vitro. With current oral hygiene a similar biofilm formation and gingival response, as evaluated, were observed at sites of CAC, resin composite and enamel. After ceased oral hygiene, more biofilm was assembled on CAC and on resin composite than on enamel. Neither with, nor without oral hygiene, biofilm formation, presence of caries-associated bacteria, clinical gingivitis and the levels of IL-1α, IL-1β and IL-1 ra differed between sites of ceramic, resin composite and enamel. Higher volumes of GCF were collected at ceramic sites compared to enamel. Fresh specimens of CAC showed the lowest cytotoxic effects on fibroblasts compared with three resin composites, zinc phosphate and glass ionomer cements. In conclusion, the low cytotoxic effect of CAC and the limited increase in dental biofilm formation on that material compared with enamel suggest CAC to be a biocompatible dental material with respect to dental biofilm formation, presence of caries-associated microflora and gingival response. This finding, together with the observation that the influence of bonded ceramic on dental biofilm formation, caries-associated microflora and clinical gingivitis was not different from that of enamel, implicates for both CAC restorations and bonded ceramic that the need of oral hygiene and professional oral health care is not reduced.

In recent years, the United States Departments of Homeland Security (DHS) and Customs and Border Protection (CBP) have been charged with the task of scanning every cargo container crossing domestic borders for illicit radioactive material. This is accomplished by using gamma-ray detection systems capable of discriminating between non-threatening radioisotopes, such as Cs-137, which is often used in nuclear medicine, and fissile material, such as U-238, that can be used to make nuclear weapons or "dirty" bombs. Scintillation detector systems, specifically thallium-doped sodium iodide (NaI(Tl)) single crystals, are by far the most popular choice for this purpose because they are inexpensive relative to other types of detectors, but are still able to identify isotopes with reasonable accuracy. However, increased demand for these systems has served as a catalyst for the research and development of new scintillator materials with potential to surpass NaI(Tl). The focus of a majority of recent scintillator materials research has centered on sintered transparent ceramics, phosphor-doped organic matrices, and the development of novel single crystal compositions. Some of the most promising new materials are glass-ceramic nanocomposites. By precipitating a dense array of nano-scale scintillating crystals rather than growing a single monolith, novel compositions such as LaBr₃(Ce) may be fabricated to useful sizes, and their potential to supersede the energy resolution of NaI(Tl) can be fully explored. Also, because glass-ceramic synthesis begins by casting a homogeneous glass melt, a broad range of geometries beyond the ubiquitous cylinder can be fabricated and characterized. Finally, the glass matrix ensures environmental isolation of the hygroscopic scintillating crystals, and so glass-ceramic scintillators show potential to serve as viable detectors in alpha- and neutron-spectroscopy in addition to gamma-rays. However, for the improvements promised by glass-ceramics to become reality, several material properties must be considered. These include the degree of control over precipitated crystallite size, the solubility limit of the glass matrix with respect to the scintillating compounds, the variation in maximum achievable light yield with composition, and the peak wavelength of emitted photons. Studies will focus on three base glass systems, sodium-aluminosilicate (NAS), sodium-borosilicate (NBS), and alumino-borosilicate (ABS), into which a cerium-doped gadolinium bromide (GdBr₃(Ce)) scintillating phase will be incorporated. Scintillator volumes of 50 cubic centimeters or greater will be fabricated to facilitate comparison with NaI(Tl) crystals currently available.

Yttria Partially Stabilized Zirconia (Y-PSZ) plasma-sprayed coatings are widely used in turbine engines as thermal barrier coatings. However, in diesel engines Y-PSZ TBCs have not met with wide success. To reach the desirable temperature of 850-900˚C in the combustion chamber from the current temperature of 400-600˚C, a coating with a thickness of approximately 1mm is required. This introduces different considerations than in the case of turbine blade coatings, which are on the order of 100µm thick. Of the many factors affecting the durability and failure mechanism of TBCs, in service and residual stresses play an especially important role as the thickness of the coating increases. For decreasing the residual stress in the system, a multi-layer coating is helpful. The design of a multilayer coating employing relatively low cost materials with complementary thermal properties is described. Numerical models were used to describe the residual stress after deposition and under operating conditions for a multilayer coating that exhibited the desired temperature gradient. Results showed that the multilayer coating had a lower maximum stress under service conditions than a conventional Y-PSZ coating. Model validation with experiments showed a good match between the two.

Clarks Crossing, FbNo-24, is a farmstead site occupied during the late nineteenth century by John Fowler and Maggie Clark. It was during the excavation of this site during the Department of Archaeology Historical Archaeology Field School (2002-2005) at the University of Saskatchewan, under the direction of Dr. Margaret Kennedy, that interesting patterns in the ceramic assemblage were observed. There seemed to be a preference in the assemblage for moulded relief decorated white granite ware ceramics. This research was undertaken to explore that preference and possible meanings behind it. Three avenues of study are undertaken to accomplish the goal of learning more about the relationship between ceramics, consumer behaviour and the sociocultural landscape of the nineteenth century west. These avenues are as follows; a historical and archaeological study of the Clarks and the site of Clarks Crossing, a discussion of white granite ware ceramics and the issues regarding its classification, and an analysis of the ceramics at Clarks Crossing including an examination of the ware types, the makers marks, and the decorative technique and images found on the ceramics.<p> The behaviour of consumers can be influenced by several factors, including marketing and group membership or identity. Marketing can be a separate influence but it can also be seen as a factor in creating a perceived group identity. This thesis explores the influences on consumer behaviour in ceramics, specifically the ceramics of Clarks Crossing. It will discuss the implication that the ware type and decorative images on the ceramics act as the material manifestation of such influences.