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archives@tulane.edu / I often find myself drawn toward objects that most would consider mundane. I am compelled to reevaluate subject matter that I have previously conditioned myself to disregard, investigate what I believe to know about the objects, and consider their new potential based on unexpected findings. My thesis exhibition explores my initial perception of repurposed cardboard boxes by fabricating realistic and formally exaggerated variations of them in clay. The three distinct categories of work within the show (trompe l’eoil boxes, abstracted cardboard boxes, and fragmented wall pieces) are an embodiment of my analytical approach to observing cardboard with a fresh perspective. Trompe l’eoil boxes provide a frame of reference. Abstracted cardboard boxes utilize unexpected characteristics of cardboard—as well as recognizable traits of clay—to challenge preconceived notions of how a cardboard box looks and functions. Wall pieces that partially resemble torn scraps of cardboard questions what remains of objects incapable of serving their intended function, while also discussing cardboard and clay materiality. A one-dimensional perspective of cardboard boxes presents them as utilitarian vessels, manufactured without ostentatious appeal, designed to protect objects we cherish, and meant to ultimately be discarded without contemplation. Through unbiased observation, formally and conceptually multifaceted layers emerge from behind initial perceptions of the box. / 1 / Holly E Ross

acase@tulane.edu / 1 / Nina Neivens

Doctor of Dental Science / This work was digitised and made available on open access by the University of Sydney, Faculty of Dentistry and Sydney eScholarship . It may only be used for the purposes of research and study. Where possible, the Faculty will try to notify the author of this work. If you have any inquiries or issues regarding this work being made available please contact the Sydney eScholarship Repository Coordinator - ses@library.usyd.edu.au

The chemical preparation of ceramic materials has been widely studied over the past few decades, and provides the potential for excellent control over the microstructure and properties of the final product. This control is dependent on a comprehensive understanding of the microstructure and physical/chemical processes that occur at each stage. Aqueous routes have much potential for adoption by industry, but in many cases a comprehensive understanding of the microstructure and chemistry is lacking, partly due to the complicated aqueous chemistry of many transition-metals. This investigation has focussed on a specific inorganic, aqueous, sol-gel route for the preparation of pure zirconia (Zr02). Zirconia is a ceramic with a wide range of current and potential applications, such as catalysis, fuel-cells, coatings and biomaterials. The emphasis has been placed on the characterisation of the structure at each stage of the route, leading to an understanding of the various mechanisms that are at work. This project has also provided an opportunity to investigate broader issues concerning the solution-based processing of zirconia, particularly those involving the 'metastable' tetragonal phase. This phase is frequently observed to be formed by non-equilibrium methods, but the mechanisms of formation and de-stabilisation are not properly understood. The studied route consists of a number of stages: the preparation of an aqueous sol of 'zirconium hydroxide' particles by forced hydrolysis of a zirconyl nitrate solution; the conversion of the sol to a gel by removal of the aqueous phase; the conversion of the gel to a crystalline tetragonal zirconia powder by heating; and transformation of the tetragonal phase to the stable monoclinic phase with further treatment. At each stage of processing a number of aspects of the material structure have been investigated, including the short-range order, crystalline lattice parameters, particle packing, porosity, and speciation of the nitrate anion. This has required a wide range of complementary characterisation techniques, including Raman spectroscopy, XRD, TEM, DTA/TGA, SAXS, dynamic light scattering, EXAFS, NMR, and nitrogen sorption. The importance of techniques that allow changes in structure to be characterised in-situ during heating has been emphasised. The particles in the sol and gel are plate-shaped, approximately 0.5 nm thick and 3 - 4 nm across. They are composed of up to several stacked `sheets' of zirconium hydroxide, each of which is composed of zirconium atoms arranged in a regular square lattice, joined by double hydroxy-bridges. Detailed evidence for this structure has not been previously reported. The stages of decomposition of the precursor have been elucidated, including the stages at which oxolation and loss of nitrate occur. The complex crystallisation process at 450°C has been investigated, and a structural mechanism for crystallisation of the 'metastable' tetragonal phase proposed, based on similarities between the tetragonal crystal structure and the disordered sheet structure in the amorphous material just prior to crystallisation. The crystalline material consists of nano-sized crystals, containing unusual intracrystalline mesopores. The lattice parameters of the tetragonal phase change with increasing heat treatment, with the unit-cell tetragonality (c/a) increasing from 1.017 to 1.020. This is a previously-unreported phenomenon which may be associated with the stability of the phase. The tetragonal phase transforms to the monoclinic phase after heating to a 'critical temperature' between 900 and 950°C; this temperature is associated with the loss of residual surface nitrate species and/or a substantial increase in the mass diffusion rate. The crystal size and surface area has little influence on the tetragonal-to-monoclinic transformation, a result which is contrary to much previously-published work and that has significant implications for certain theories explaining the stability of the tetragonal phase. The transformation itself occurs during cooling, over a range between 400 and 100°C, and has been studied in-situ by time-resolved Raman spectroscopy. The conclusions of this investigation contribute not only to the understanding of this particular route for processing zirconia, but also to a broader understanding of aqueous zirconium systems, the chemical processing of zirconia, and the tetragonal-to-monoclinic zirconia transformation mechanisms.

Thesis (Ph. D.)--University of Washington, 1983. / Vita. Includes bibliographical references.

Friction, wear, and lubrication have direct influence on performance, reliability, and service life of mechanical systems with moving components. The useful life of these systems and their efficiency can be improved by improving the surface properties/ performance at sliding interfaces. Further, the usage of materials for sliding systems is limited in extreme environments, such as high temperature, and space, etc., due to their limited surface properties. This thesis focuses on the development of a new class of composites with superior surface properties, i.e., low friction and high wear resistance for extreme environmental conditions. Alumina, a well understood material for its tribological performance, is a merit choice for applications where high wear resistance is required, such as pump bearings, seal rings, valve seats, piston components, gears, cutting tool inserts and artificial joints. We propose to develop a novel alumina based ceramic composite to enhance its surface and tribological properties using a powder compaction technique. The newly developed composites will be characterized by X-ray Diffraction (XRD), Fourier Transform Infrared spectroscope (FTIR), Optical microscope, Environmental Scanning Electron Microscope (E-SEM), Goniometer and Surface profilometer. In-situ formation of high temperature stable phases, effect of sintering temperature, and percentage of reinforcement on phase formation will be studied. Investigation of effect of sintering temperature and percentage of reinforcement on density, porosity, and grain size will be conducted. The composites will be characterized for their tribological properties (friction and wear). The mechanisms for modified friction and wear will be proposed. The process parameters and compositions will be optimized. XRD results confirmed the formation of Al18B4O33, and AlB2 and FTIR confirmed the presence of B2O3. Increase in sintering temperature and wt % of boron affected the porosity, grain size, and hardness of the composites. The coefficient of friction was lower for the composites compared to pure alumina ceramic. The coefficient of friction decreased with increase in sintering temperature. The wear mechanism was found to be micro-fracture using ESEM and SEM studies.

This study makes a simple model of ball grinder to simulate the dynamics of grinding process. This theoretical analysis of the dynamic characteristics can be used to explain the phenomenon of the Kato¡¦s experiment and it hopes to a useful tool for the design of the ball grinder. The high removal rate is obtained with magnetic fluid grinding when high sliding velocity occurs between the ball and a high rotating drive shaft. When the balls circulation rate breaks away from the shaft speed can be used to predict the onset of skidding. Since the maximum driving friction force is proportional to contact normal force and frictional coefficient, the skidding occurs at the smaller normal force and frictional coefficient. The high viscosity of fluid, the larger fluid drag force is, when overcome the driving force then the skidding occurs. The magnetic gradient is steeper when the width of magnet of the bed is thinner, the effects of supporting stiffness of the floating pad is higher. When the magnetic buoyant force of the ball is larger, the contact normal force is larger, then the removal rate is higher.