Browsing by Subject "Ceramics"

Now showing 1 - 4 of 4
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    Archaeomagnetic dating of bronze age pottery from Tell Mozan, Syria
    (2013-04) Stillinger, Michele D.
    The ancient city-state of Urkesh, located at Tell Mozan, Syria, was the political and religious center of the Hurrians, a unique culture that inhabited the northern Syro-Mesopotamian region during the 3rd millennium BCE. The chronology of Urkesh has been divided into seven primary occupational phases, dating from the Early Dynastic II period (2800-2500 BCE) to the Middle Babylonian/ Mitanni Period (1500-1300 BCE). The site has provided an abundance of distinguishing ceramics, seals, seal impressions, and cuneiform tablets, which serve as the foundation for the Urkesh chronology. Working under the assumption that the archaeologically derived chronology at Mozan was reliable, this research tested the accuracy of archaeomagnetic dating using pottery samples from six successive occupational phases. Samples underwent a suite of magnetic mineral characterization tests and archaeointensity measurements using the Thellier-style absolute paleointensity technique of Tauxe and Staudigel (2004). Archaeointensity experiments displayed an 88% success rate and 80% of the samples correlated well with their archaeologically determined dates. A small subset of samples appeared to indicate a possible intensity spike occurring around 2000 BCE. The final results refine the archaeointensity curve for Syria between 2350 and 1200 BCE.
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    Forgetting the Hand: Wedgwood, Sèvres, and the Industrial Fate of Skill
    (2020-07) Studelska, Dustin
    This dissertation explores how our modern perspective of skill developed from the 1760s to the 1840s in Western Europe. As industrial capitalism became bolstered by changes in design, business practice, international commerce, and mechanization, skill became conceptually jettisoned from the specific experiences of individual people, abstracted into industrial objects, economic categories, and physical force. This abstraction has subsequently caused a form of cultural forgetting in industrial modernity in which we, the heirs of this process, fail to appreciate the fundamental connection of skills to our essential humanity. Through the use of case studies of Josiah Wedgwood’s pottery in Stoke-on-Trent, England and the French Royal Porcelain Manufactory at Sèvres, each chapter illuminates skill’s historical complexity with relation to design, manufacture, management, industrial promotion, and technological development. This dissertation uses an analysis of private letters, printed pamphlets, royal correspondence, and ceramic objects themselves to examine the hand skills hidden within neoclassical ceramics, the skills of shrewdness utilized by Wedgwood and Sèvres, the debated notion of skill surrounding the Anglo-French Commercial Treaty of 1786, and the cultural discourses on skill’s role in mechanical progress. This research draws on recent scholarly characterizations of “the mindful hand” and “artisanal epistemology,” but moves beyond them to argue that skill, and the people who embodied it, cannot be defined by categories of knowledge.
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    Gestures of Pressure and Time
    (2021-06-16) Tibbott, Rick
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    Thermal Plasma Synthesis of Phosphor Nanoparticles
    (2011-05) Jain, Ricky
    Advanced phosphors are currently of interest for applications in various emerging technologies, such as electronic printing jets, lighting and display devices and medical devices such as fluorescence markers. Compared to conventional phosphors, nanoparticle phosphors offer potential advantages with regard to reduced light backscatter losses and dispersibility in polymer substrates. With current phosphor synthesis techniques it is challenging to simultaneously control the particle morphology and phase to synthesize phosphor nanoparticles in a commercially viable manner. This study is focused on developing a cost effective method for bulk production of nanoscale phosphor powders through a single-step radio frequency (RF) plasma process. Synthesis of several phosphor material systems were studied for this purpose, including cerium-doped yttrium aluminum garnet (Ce:YAG), which is among the most commonly used phosphors for white LED applications. Previous studies have shown that it is difficult to produce the desired YAG phase without ex-situ annealing irrespective of the synthesis technique used. Preliminary efforts to directly synthesize Ce:YAG nanoparticles with the RF plasma system were not successful. Characterization results of the as-synthesized particles showed the presence of the perovskite (YAP) phase with broad size distribution ranging from hundreds of nanometers to a few microns. Novel methods were developed to control the size and phase of the particles in the synthesis process. The experimental setup was modified by inserting a ceramic tube coaxially with the reactor inlet to incorporate a central annealing zone. Numerical modeling performed to determine the influence of the tube insertion on the thermofluid fields in the reactor indicates that the tube provides a more uniform high-temperature region, without flow recirculation. The tube is hypothesized to aid in size and phase control through selective particle collection and in-flight annealing. Ce:YAG particles synthesis experiments conducted with the tube-insertion setup indicate that phase and size control of the particles is possible to a certain extent, depending on the size of the tube. Characterization results of the synthesized particles showed that submicron sized YAG particles are synthesized as the majority phase through the 47.5 mm tube-insertion setup. Synthesis of other phosphor materials such as Ce:CaSc2O4 and Eu:SrAl2O4 also indicate that the tube insertion setup helps to control the particle size and phase partially and to improve the photoluminescence through in-flight annealing. The precursor atomization process was studied with the aim of developing effective methods to control the size and phase of the particles in the synthesis process. A laser imaging technique was used to characterize the high density spray generated with the Tekna atomizer probe. Image processing results indicate that sprays generated with flow conditions similar to that used in experiments have broad droplet size distribution ranging from 10s to 100s of microns. An effective method studied to fragment water based droplets in the plasma is by adding an organic fuel such as urea. The urea decomposes exothermically in the high temperature region, thereby aiding in the secondary fragmentation and evaporation of the droplets. Smaller droplets and enhanced evaporation rates are hypothesized to increase the gas phase nucleation synthesis route of particles, leading to smaller particles. Experiments were performed with varying concentrations of urea in nitrate salts and water based precursors for synthesis of various phosphor materials. The results indicated that the particle size decreases with increasing urea concentrations. Using >7M urea concentration with 0.4M salt concentrations in the precursor results in primarily nano sized particles. Adding urea in the precursor was also observed to affect the phase of the particles by providing a reducing chemical environment in the synthesis. Finally a novel precursor developed by Nitto Denko Tech. Corp. for the synthesis Ce:YAG particles was studied. Thermal analysis of the dried precursor was performed to study the YAG crystallization process. YAG nanoparticles were synthesized through the precursor atomization and annealing process. Diluted precursor was also injected in the plasma to achieve single phase YAG particles directly from the RF plasma system. However, the precursor synthesis method is expensive and time intensive. Therefore it was not used for synthesis of other phosphor materials.