A high temperature magnetic bearing system using high temperature permanent magnets from Electron Energy Corporation (EEC) is under development. The system consists of two radial bearings, one thrust bearing, two radial catcher bearings and one motor. The purpose of this research is to develop one of the critical components of the system, namely, the High Temperature Permanent Magnet motor. A novel High Temperature Permanent Magnet (HTPM) Brushless DC(BLDC) motor capable of operating at 1000 degrees F (538 degrees C) is designed. HTPMs developed at Electron Energy Corporation are buried into the rotor. The high temperature motor is designed to produce 5.1kw of power at a top running speed of 20000 rpm. The numerical values of the motor voltage, power and torque output are predicted from calculations of the nonlinear finite element model of the motor. The motor stator is wound, potted, cured and high potential tested at 1000 degrees F. A servo amplifier from Advanced Motion Control is used to drive the high temperature motor. High temperature displacement sensors are set up for sensing the rotor position to form a closed loop motion control. However, the noise problem of the high temperature sensors causes a failure of this approach. An open loop approach is then developed and this approach succeeds in spinning the rotor with the capability of self-starting. The status of the full system assembling is introduced. Some other components of the system are briefly presented.

To assure nuclear power sustainability, ongoing efforts on advanced closed-fuel cycle options and adapted open cycles have led to investigations of various strategies involving utilization of Transuranic (TRU) nuclides in nuclear reactors. Due to favorable performance characteristics, multiple studies are focused on transmutation options using High Temperature Gas-cooled Reactors (HTGRs). Prismatic HTGRs allow for 3-Dimensional (3D) fuel shuffling and prior shuffling algorithms were based on experimental block movement and/or manual block shuffle patterns. In this dissertation, a physics based 3D multi-directional reloading algorithm for prismatic deep burn very high temperature reactors (DB-VHTRs) was developed and tested to meet DB-VHTR operation constraints utilizing a high fidelity neutronics model developed for this dissertation. The high fidelity automated neutronics model allows design flexibility and metric tracking in spatial and temporal dimensions. Reduction of TRUs in DB-VHTRs utilizing full vectors of TRUs from light water reactor spent nuclear fuel has been demonstrated for both a single and two-fuel composition cores. Performance of the beginning-of-life and end-of-life (EOL) domains for multi-dimensional permutations were evaluated. Utilizing a two-fuel assembly permutation within the two-fuel system domain for a Single-Fuel vector, the developed shuffling algorithm for this dissertation has successfully been tested to meet performance objectives and operation constraints.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 87-88). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 87-88). Also available on the Internet.

The aim of this project was to investigate the potential of fused-slurry coatings for improving the oxidation resistance of wrought alloys. Slurry-aluminised coatings were deposited on Alloy 800H (Fe-33Ni-20Cr), Alloy HCM12A (Fe-12Cr-2W), Alloy 214 (Ni-16Cr-4Al-3Fe), Fe-27Cr-4Al and Fe-14Cr-4Al alloys. The slurry contained a cellulose-based binder in an aqueous carrier and spherical aluminium powder, with a particle size below 20 microns. The slurries were applied with a paint-brush, dried in air and heat treated in either hydrogen or argon at temperatures between 700 and 1150C. The slurries were characterised by thermogravimetry, differential scanning calorimetry and viscometry. The coatings were characterised by optical microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction and Vickers hardness measurements. The oxidation resistance of selected slurry-coated specimens was assessed in air at 1000 and 1100C in tests lasting up to 1000 hours.Slurry-aluminising was found to be a simple, effective way of forming protective coatings that were similar in composition and microstructure to chemical vapour deposits. However, it was difficult to control the amount of slurry applied to the substrate and produce coatings of uniform thickness.The coatings on Alloy HCM12A and the Fe-Cr-Al alloys contained cracks in the brittle FeAl phase due to tensile stresses arising from differences in the thermal expansion coefficients of the substrates and the coatings. Rapid interdiffusion between the coatings and the ferritic substrates resulted in the appearance of Kirkendall voids.Coatings on Alloy 214 required a two-stage heat treatment to convert the brittle δ-Ni2Al3 to β-NiAl. Cracking along the coating/substrate interface was prevented by limiting the coating thickness to a maximum of 250 microns. During oxidation at 1100C, the β-NiAl was converted to γ'-Ni3Al. After 1000 h, the centre of the coating consisted chiefly of γ'-Ni3Al and bands of austenite (γ-Ni) were present at the inner and outer edges of the coating. The aluminium content at the coated surface was higher than the original aluminium content of the alloy, the protective alumina scale was improved and the oxidation life of the substrate was extended. An additional life of 1250 h at 1100C is estimated from a slurry coating before the aluminium content returns to that of the original alloy (4%), providing a potential improvement in oxidation resistance.Microstructural changes such as grain growth, sensitisation and formation of aluminium nitride particles near the coating/substrate interface, were detected in the alloy substrates after forming the slurry coatings. However, these microstructural changes did not detract from the good performance of the coatings during oxidation tests at 1100C.The work in this study has demonstrated a low-cost method of coating high-temperature alloys providing coatings with microstructures, densities and modes of degradation similar to those obtained by other coating methods. The coatings are potentially applicable to a wide range of high-temperature substrates.

This dissertation presents new solutions for turbine engines in need of wireless temperature sensors at temperatures up to 1300oC. Two important goals have been achieved in this dissertation. First, a novel method for precisely characterizing the dielectric properties of high temperature ceramic materials at high temperatures is presented for microwave frequencies. This technique is based on a high-quality (Q)-factor dielectrically-loaded cavity resonator, which allows for accurate characterization of both dielectric constant and loss tangent of the material. The dielectric properties of Silicon Carbonitride (SiCN) and Silicoboron Carbonitride (SiBCN) ceramics, developed at UCF Advanced Materials Processing and Analysis Center (AMPC) are characterized from 25 to 1300oC. It is observed that the dielectric constant and loss tangent of SiCN and SiBCN materials increase monotonously with temperature. This temperature dependency provides the valuable basis for development of wireless passive temperature sensors for high-temperature applications. Second, wireless temperature sensors are designed based on the aforementioned hightemperature ceramic materials. The dielectric constant of high-temperature ceramics increases monotonically with temperature and as a result changes the resonant frequency of the resonator. Therefore, the temperature can be extracted by measuring the change of the resonant frequency of the resonator. In order for the resonator to operate wirelessly, antennas need to be included in the design. Three different types of sensors, corresponding to different antenna configurations, are designed and the prototypes are fabricated and tested. All of the sensors successfully perform at temperatures over 1000oC. These wireless passive sensor designs will significantly benefit turbine engines in need of sensors operating at harsh environments

From space exploration and advanced aircraft to next generation weapons, achieving hypersonic speed is becoming increasingly important across a range of research domains. The immense challenge associated with this goal involves the development of suitable materials and systems for the different components of a hypersonic vehicle, each of which must have the inherent capability to resist extreme temperatures, high thermal shock due to high heat flux, and high oxidation and ablation. First, the ultra-high temperature ceramic (UHTC) zirconium diboride or ZrB2 was sintered by ultra-fast high temperature sintering (UHS). The UHS process was optimized and the sintering parameters for ZrB2 and other UHTCs were studied. ZrB2 is an ultra-high temperature ceramic (UHTC) with a very high melting point; thus, its densification is difficult, energy intensive, and time-consuming. Commercial ZrB2 powders were rapidly densified via UHS to >90% relative density within 60 second in vacuum without pressure. The effect of sintering time on densification and final grain size were studied. An innovative process for manufacturing bulk UHTC materials was studied and is detailed herein. Second, the work function (W_f) of electron emitting materials was reduced to improved performance. A reduction of W_f in multicomponent hexaborides was achieved by doping with highly electropositive Ba, which enhances electron emission. Single-phase bulk multicomponent polycrystalline hexaborides of La0.5Ba0.5B6, Ce0.5Ba0.5B6, and BaB6 powders were first synthesized and then densified by UHS sintering. W_f measurements were obtained by Kelvin probe force microscopy. Ba-substitution was found to lower W_f (~25%) in synthesized multicomponent hexaborides. The specific techniques required to engineer the W_f of these materials are also provided herein. Finally, combining low W_f materials with UHTCs was explored for thin film systems for the exterior surface of hypersonic vehicles. The thin films of CeB6, a low W_f material, was deposited on sintered ZrB2 by RF-sputtering and single crystalline SrTiO3 (STO) substrates. Epitaxial thin films of SrHfO3 (SHO) were also deposited on (100), (110) and (111) STO substrates at 600°C. X-ray diffraction (XRD) results confirmed the formation of epitaxial layer, and reciprocal space mapping (RSM) was used to characterize film's mosaicity / texture on different substrates. XRD and RSM data demonstrated that the most favorable film growth direction was (110). As detailed herein, an inexpensive thin film production process, RF-sputtering, was exploited to manufacture various epitaxial and non-epitaxial layers of low W_f materials on UHTC and single-crystal substrates for hypersonic vehicles. To summarize, a range of bulk UHTCs and low W_f materials were prepared by UHS, and various thin films of low W_f material were produced on UHTC. Thereafter, the properties of synthesized materials were studied to develop new material systems for hypersonic applications. The findings from this research shed light on the development of suitable materials for implementation of electron transpiration cooling for hypersonic vehicle development. / Doctor of Philosophy / Rapid sintering of ultra-high temperature ceramics (UHTCs) and synthesis of low work-function electron emitting materials have been performed by ultra-fast high temperature sintering technique (UHS). Sintering of UHTCs is a difficult process, due to their high melting temperature, presence of covalent bond, and slower diffusion coefficient. A long sintering duration is used to achieve a high relative density along with adding sintering aid, using fine powder (produced by milling), and utilizing pressure (such as field assisted sintering and hot-pressing technology) during sintering. Synthesis and densification of multicomponent hexaboride is difficult, involves multi-steps and complicated processes. These long and complicated processes not only prolong development of new materials but also cause chemical wastes. To overcome all the aforementioned processing issues, an advanced processing technique, UHS, is used and densified pure and commercially available UHTCs to >90% within 60 second without applying sintering aid, powder milling, and pressure. The outcome of this research demonstrates the potential for a simple, cost-effective, fast, and adjustable processes, UHS, to develop a wide range of bulk UHTCs and other technical ceramics, and it gives new insight into the mechanisms of rapid sintering of UHTCs by rapid heating. The first detailed studies (experimental report) on rapid sintering of ZrB2 (and other UHTCs) by UHS technique and a through characterizations of the UHS sintered sample were performed to understand rapid sintering mechanism and how the processing effects the microstructure and properties of UHS ZrB2. The rapid microstructural evolution during the UHS sintering is investigated at 10, 30, and 60 second sintering interval. The UHS technique enables a heating rate of 103 - 104 °C/min and reaches a sintering temperature of 2600 °C in 30 seconds. Microstructural analysis was conducted on polished sample surfaces by using ImageJ software (National Institutes of Health, version 1.53e), measuring the grain size perpendicular to two diagonals of each grain. A comparison of grain size from sample center and periphery showed a homogeneous microstructure after sintering. Furthermore, the rapid sintering did not change/effect crystallinity, boron to metal stoichiometry, and grain boundary elemental composition as observed by XRD and EDS analysis. Additional characterization of the UHS sintered ZrB2 shows a hardness and elastic modulus of 30 GPa and 412 GPa respectively by nanoindentation method. Finally, the oxidation test at 1100 °C in isothermal condition showed a weight gain of 1.4% in air. The low work-function (W_f) materials are famous for electron emitting applications like electron guns for scanning electron microscopy. DFT simulation predicts the W_f of the widely used electron emitters (such as LaB6 and CeB6) can be reduced by changing their compositions, which increase electron generation efficiency of those materials. Previously, those materials were synthesized by long processes that involved multiple processing steps, which required expensive starting materials and yielded chemical wastes. The advantages of rapid sintering technique, UHS, had been exploited to synthesize low work function electron emitting materials. Single-phase bulk polycrystalline hexaborides were produced by using electrically powered UHS technique using a vacuum atmosphere. A reaction synthesis route: B4C reduction technique was first used to form pure phase hexaboride. Then, the synthesized compositions were densified to ~90% theoretical density in 180 seconds by UHS densification. After UHS sintering, XRD analysis confirmed the presence of a phase pure cubic BaB6, La0.5Ba0.5B6, and Ce0.5Ba0.5B6. Additional analyses were conducted to determine an optimum reaction temperature 1500 and 2100 °C for the formation BaB6 and multi-component hexaborides. Microstructural analyses were conducted to observe both reaction-synthesized and densified products. EDS compositional analysis and elemental mapping revealed a stoichiometric reaction product with homogeneous metal cation and boron distributions. The W_f of BaB6, La0.5Ba0.5B6, and Ce0.5Ba0.5B6 was determined to be 1.95 ± 0.1, 2.05 ± 0.1 and 2.0 ± 0.1 eV, respectively. The addition of BaB6 in La0.5Ba0.5B6, and Ce0.5Ba0.5B6 resulted in a 25% decrease in W_f for LaB6 from 2.7 ± 0.1 to 2.00 ± 0.1 eV and a 23% decrease in W_f for CeB6 from 2.68 ± 0.08 to 2.05 ± 0.1 eV. Ba substitution is shown to be a general method for lowering W_f in a variety of multicomponent hexaborides. Finally, the polycrystalline thin films of CeB6, a low W_f material, was deposited on sintered ZrB2 by RF-sputtering technique. Additionally, epitaxial thin films of SrHfO3 (SHO) were also deposited on (100), (110) and (111) STO single crystalline substrates. Both types of thin films were deposited at 600 °C temperature and at a vacuum pressure of 10-3 Torr. After deposition of the SHO films, X-ray diffraction (XRD) was conducted to confirm the formation of epitaxial layer, and reciprocal space mapping (RSM) was used to characterize film's mosaicity / texture on different substrates. XRD and RSM data demonstrated that the most favorable film growth direction was (110). The XRD of the CeB6 film showed highly crystalline film was formed. For both the films, a detailed microstructural analysis was performed by scanning electron microscopy and film smoothness was characterized by atomic force microscopy method. As detailed herein, an inexpensive thin film production process, RF-sputtering, was exploited to manufacture various epitaxial and non-epitaxial layers of low W_f materials on UHTC and single-crystal substrates for hypersonic vehicles applications.

Emission regulations for heavy-duty diesel engines are becoming increasingly restrictive to limit the environmental impacts of exhaust gases and particles. Increasing the specific power output of diesel engines would improve fuel efficiency and greatly reduce emissions, but these changes could lead to increased exhaust gas temperature, increasing demands on the exhaust manifold material. This is currently the ferritic ductile cast iron alloy SiMo51, containing about 4 wt% Si and ~1 wt% Mo, which operates close to its fatigue and oxidation resistance limits at peak temperature (750C). To ensure high durability at higher temperatures, three different approaches to improving the life of exhaust manifolds were developed in this thesis. The first approach was to modify SiMo51 by adding different combinations of Cr and Ni to improve its high-temperature strength and oxidation resistance, or by applying a thermal barrier coating (TBC) to reduce the material temperature and thereby improve fatigue life. In the second approach, new materials for engine components, e.g. austenitic ductile iron and cast stainless steel, were investigated for their high-temperature fatigue and oxidation properties. In order to identify the most suitable alloys for this application, in the third the environmental effects of the corrosive diesel exhaust gas on the fatigue life of SiMo51 were investigated. The high-temperature oxidation resistance of SiMo51 at 700 and 800C in air was found to be improved by adding Cr, whereas Ni showed adverse effects. The effects of solid-solution hardening from Ni and precipitation hardening from Cr were low at 700C, with improvements only at lower temperatures. Applying a TBC system, providing thermal protection from a ceramic topcoat and oxidation protection from a metallic bond coat, resulted in only small reductions in material temperature, but according to finite element calculations still effectively improved the fatigue life of a turbo manifold. Possible alternative materials to SiMo51 identified were austenitic cast ductile iron Ni-resistant D5S and austenitic cast stainless steel HK30, which provided high durability of exhaust manifolds up to 800 and 900C, respectively. Corrosion fatigue testing of SiMo51 at 700C in diesel exhaust gas demonstrated that the corrosive gas reduced fatigue life by 30-50% compared with air and by 60-75% compared with an inert environment. The reduced fatigue life was associated with a mechanism whereby the crack tip oxidized, followed by crack growth. Thus another potential benefit of TBC systems is that the bond coat may reduce oxidation interactions and further improve fatigue life. These results can be used for selecting materials for exhaust applications. They also reveal many new research questions for future studies. Combining the different approaches of alloy modification, new material testing and improving the performance using coatings widened the scope of how component life in exhaust manifolds can be improved. Moreover, the findings on environmental interactions on SiMo51 fatigue provide a completely new understanding of these processes in ductile irons, important knowledge when designing components exposed to corrosive environments. The novel facility developed for high-temperature corrosion fatigue testing can be useful to other researchers working in this field. / <p>QC 20150507</p>

No description available.

Master of Science / Food Science Institute / Karen A. Schmidt / The demand for ultra high temperature processed and aseptically packaged dairy foods is growing throughout the U.S. The technology provides value-added food preservation for many foods including flavored milks, puddings, custards, creams, ice-cream mixes, whey-based drinks, sports drinks, and yogurt. Ultra high temperature nonfat milk, milk, light cream, and 18% cream are used throughout the U.S. by the restaurant and food service industries. There are several advantages to aseptic processing and packaging over traditional pasteurization. Advantages include extended shelf life, lower energy costs, and the elimination of required refrigeration during storage and distribution. Challenges are present in all aspects of dairy processing. Major challenges associated with ultra high temperature processing and aseptic packaging of dairy foods include product quality loss, such as age gelation, fat separation, and flavor loss, as well as manufacturing issues such as limited production capacity, potential contamination, slow packaging speeds, and limited shelf life knowledge. This report reviews the history of aseptic processing, principles of ultra high temperature processing, principles of aseptic filling, quality control of UHT dairy foods, and regulations for dairy processors.