Conventional stainless steel - water and ceramic fabric composite water heat pipes have been built and tested. The tests have been conducted to compare the performance characteristics between conventional and fabric composite heat pipe radiators for space nuclear power heat rejection systems. The fabric composite concept combines a strong ceramic fabric with a thin metal liner to form a very lightweight heat pipe. The heat pipes tested have used identical, homogeneous fabric wicks and water as the working fluid. One fabric composite heat pipe has been constructed by fitting a braided aluminoborosilicate fabric tube over the outside of the conventional stainless steel heat pipe. A more advanced fabric composite design combines the woven fabric with a 0.25 mm (10 mil) stainless steel tube as the liner, and reduces the mass of the heat pipe by a factor of three. A heat pipe testing facility was designed and built for the purpose of testing various conventional and fabric composite heat pipes. This facility allows the testing of heat pipes in a vacuum, at low temperatures, and can accommodate a variety of heat pipe designs. Instrumentation and computer interfacing provide for continuous monitoring and evaluation of heat pipe performance. Tests show that heat pipe radiator capacity can be significantly enhanced by using the fabric composite design. Tests comparing a conventional heat pipe with fabric composite heat pipes achieved a 100% increase in the emissivity and heat rejection capacity of the radiator. Since the ceramic fabric is strong enough to withstand the internal pressure of the heat pipe, a very thin metal foil can be used to contain the working fluid. The increase in heat rejection capacity, combined with the significant reduction in the heat pipe mass, translates into a substantial savings for space power systems employing fabric composite heat pipe radiators. / Graduation date: 1993

The Advanced Fuel Cycle Initiative (AFCI) is a Department of Energy (DOE) program, that has been investigating technologies to improve fuel cycle sustainability and proliferation resistance. One of the program's goals is to reduce the amount of radioactive waste requiring repository disposal. Cesium and strontium are two primary heat sources during the first 300 years of spent nuclear fuel's decay, specifically isotopes Cs-137 and Sr-90. Removal of these isotopes from spent nuclear fuel will reduce the activity of the bulk spent fuel, reducing the heat given off by the waste. Once the cesium and strontium are separated from the bulk of the spent nuclear fuel, the isotopes must be immobilized. This study is focused on a method to immobilize a cesium- and strontium-bearing radioactive liquid waste stream. While there are various schemes to remove these isotopes from spent fuel, this study has focused on a nitric acid based liquid waste. The waste liquid was mixed with the bentonite, dried then sintered. To be effective sintering temperatures from 1100 to 1200 degrees C were required, and waste concentrations must be at least 25 wt%. The product is a leach resistant ceramic solid with the waste elements embedded within alumino-silicates and a silicon rich phase. The cesium is primarily incorporated into pollucite and the strontium into a monoclinic feldspar. The simulated waste was prepared from nitrate salts of stable ions. These ions were limited to cesium, strontium, barium and rubidium. Barium and rubidium will be co-extracted during separation due to similar chemical properties to cesium and strontium. The waste liquid was added to the bentonite clay incrementally with drying steps between each addition. The dry powder was pressed and then sintered at various temperatures. The maximum loading tested is 32 wt. percent waste, which refers to 13.9 wt. percent cesium, 12.2 wt. percent barium, 4.1 wt. percent strontium, and 2.0 wt. percent rubidium. Lower loadings of waste were also tested. The final solid product was a hard dense ceramic with a density that varied from 2.12 g/cm3 for a 19% waste loading with a 1200 degrees C sintering temperature to 3.03 g/cm3 with a 29% waste loading and sintered at 1100 degrees C. Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA) of the loaded bentonite displayed mass loss steps which were consistent with water losses in pure bentonite. Water losses were complete after dehydroxylation at ~650 degrees C. No mass losses were evident beyond the dehydroxylation. The ceramic melts at temperatures greater than 1300 degrees C. Light flash analysis found heat capacities of the ceramic to be comparable to those of strontium and barium feldspars as well as pollucite. Thermal conductivity improved with higher sintering temperatures, attributed to lower porosity. Porosity was minimized in 1200 degrees C sinterings. Ceramics with waste loadings less than 25 wt% displayed slump, the lowest waste loading, 15 wt% bloated at a 1200 degrees C sintering. Waste loading above 25 wt% produced smooth uniform ceramics when sintered >1100 degrees C. Sintered bentonite may provide a simple alternative to vitrification and other engineered radioactive waste-forms.

Design of the circularly polarized ceramic antenna, suitable for GPS system, on an asymmetric ground plane is presented in this thesis. Firstly, to obtain two isolated ground planes, we insert an L slit on an asymmetric ground plane, making the antenna with a symmetric ground plane. Then, we isolate the excited surface current between the two ground planes by using a quarter-wavelength mini-coaxial cable. The surface current can distribute uniformly on the ground plane when the proposed antenna is in operation, which makes possible a good circularly polarized radiation pattern in the operation band.

In this thesis we propose several novel configurations of bandpass filters (BPFs) with two transmission zeros by using the fractal theory. By means of the fractal theory, the dimension of the proposed BPFs can be effectively reduced. Furthermore, the proposed BPFs can be easily fabricated by using multilayer structure based on low-temperature cofired ceramic (LTCC) technology. Under the condition of the same dielectric thickness and coupling coefficient, we compared the conventional square open-loop BPF with the proposed fractal ones. The results show that the reduction in the dimension of the proposed BPFs is evident. Specifically, the dimension of the proposed Koch¡¦s, Minkowski_1st, and Minkowski_2nd filters can be reduced by about 36.5%, 32%, and 51.5%, respectively. Finally, the simulation and measurement results are reported in this thesis.

The ceramic industry of Jingdezhen in China can be traced back to the Han Dynasty. Up to the Ming and Qing dynasties, it has become a mature and professionally divided work site handicraft model. Because it has the heritage of the official kiln culture, its status has never changed even though dynasties have changed; it has always been emphasized and supported by the government. However, the competitiveness of Jingdezhen ceramic industry today is far below that of the other ceramic industry community areas in China. In order to clarify the nature of problems of the industry, this study uses the concept and theory of ¡§entrepreneurship¡¨ as well as establishment of the analytical framework to seek the historical context of Jingdezhen ceramic industry development from tradition to the modern. This study also compares it to the 18th Century rise of the English ceramic industry ¡§The Potteries.¡¨ This study finds that development of the Jingdezhen ceramic industry has not been like ¡¥The Potteries¡¨ ceramic industry of England because the social environment and industrial economic system is not conducive to the appearance of entrepreneurs, who can use entrepreneurship to optimize the internal and external conditions of the industry to create success. Such research results can not only help readers understand the current industrial situation in Jingdezhen, but can also help the government or corporate units to reevaluate the appropriateness of their developmental strategies.

This thesis proposes methodology to design a balun with imaginary impedance. Under given specification, including center frequency, size, output impedance, our methodology can be used to evaluate its feasibility of implementation using high-DK LTCC(Low Temperature Cofired Ceramic) process. We then extend the design to incorporate a filter, which can simplify the circuit to reduce the required components. An example of our design operating at 2.4 GHz is implemented. Its size is 1600¡Ñ800¡Ñ650 um3, showing significant miniature. The simulation and measurement results are shown to verify the effectiveness of our design.

This thesis deals with the investigations on the nonlinear electrical and manganetotransport properties of polycrystalline multi-phase ceramic composites of Zno/pervoskite manganite. Multifunctional properties are studied such as the enhanced low-field magnetoresistance(LFMR). magnetically tuneable low-voltage nonlinear current-voltage (I-V) characteristics with larger nonlinearity coefficients suitable for semiconducting and magnetoelectric devices. A brief introduction on the structure-property correlations, electronic and magnetic structures, nonlinear electrical conduction, phase separation, grain size and grain boundary effects on transport properties of manganites are presented. The nonlinear current-voltage characteristics of ZnO based varistors are also summarized. The thesis describes the synthesis of the ceramics and the methodology of different techniques utilized in characterizing the samples. The phase conversions in calcium manganite with changing Ca/Mn ratios as well as the oxygen non-stoichiometry and their influence on electrical transport properties were studied. The realization of low-voltage varistors prepared from ZnO+ CaMnO3 ceramic composites was described. An energy band model consisting of n-p-n heterojunctions of n-ZnO1-γ:Mn/p-CMZO/n-ZnO1 γ:Mn has been proposed in order to explain the large nonlinearity coefficients obtained at low field-strengths of 1.8 to 12 V/mm. The detailed investigationos on the structural identification and physico-chemical analyses of Ca4Mn7Zn3O21-δ(CMZO) phases having the beta-alumina or magnetoplumbite-type structures were carried out. The thesis also embodies the magnetically tuneable nonlinear I-V characteristics and the magnetotransport properties of ZnO/La(Sr)MnO3 and ZnO/La(Ca,Sr)MnO3 ceramic composites. The present investigations demonstrate that the ferromagnetic insulating (FMI) La06 Sr04Mn1-yZnyO3(y = 3 to 8 at.%) when present as minor phase in ZnO1- γ:Mn ceramics enables in attaining magnetically tunealbe nonlinear I-V characteristics. Wherein, the dominant ZnO1- γ:Mn phase remains paramagnetic. The results also indicate that the prevalence of ferromagnetism in ZnO1-γ:Mn is not significant for realizing magnetically tuneable I-V curves. The controversial results related to the existence of ferromagnetism in ZnO(doped)leading to diluted magnetic semiconductors(DMS) have been investigated. Another novel aspect of the present work is the low-field magnetoresistive(LFMR) property of ZnO/La(Sr)MnO3 and ZnO/La(Ca.Sr)MnO3 ceramic composites which been explained on the basis of spin-polarised tunneling across the intergrain regions. The influence of Zn2+ as a diamagnetic substitutent in modifying the crystallographic phase content, electrical transport and magnetic properties of Lao6Sro4MnO3 were studied in detail. The results point towards the fact the large decrease of Tc and Ms at lower Zn contents(≤ 8 at.%)is due to the dominant role played by the excess oxygen vacancy (Vo) as an electron donor in p-type Lao6Sro4Mn1-yZnyO3-δ rather than the charge compensatively predictable values. The modifications of electronic and magnetotransport properties were carried out on Lao6Sro4MnO3 substituted with diamagnetic ions such as Mg2+ - Al3+ - Ti4+ - Nb5+ - Mo6+ or W6+ at Mn-sublattice. The TEM studies including HREM results point to the fact the large ΔT(= Tc-TM-1)is accountable in terms of charge conduction within the electronically heterogeneous phase mixtures of charge ordered insulating (CO1) bi-stripes prevailing within the charge disordered FMI phases.

Thesis (M.F.A.)--Rochester Institute of Technology, 1966. / Bibliography.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 202-206).

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Ceramic and Materials Science and Engineering." Includes bibliographical references.