Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [167]-170).

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 207-210). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 118).

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The aim of this thesis is to propose the design process and considerations to be employed in the fabrication of a high-volumetric-power-density intermediate temperature solid oxide fuel cell (IT-SOFC), as well as the necessary characterization and analysis techniques for such a device. A novel hexagonal honeycomb design will be proposed with functionally graded electrodes and an alternative electrolyte – a previously unexplored configuration based on attained research. The potential use of CFD software to investigate mass and heat transport properties of an SOFC having such a design shall be discussed, as well as the utility of experimental methods such as the generation of a polarization curve and the use of SEM to characterize electrochemical performance and microstructure, respectively. Fabrication methods shall also be evaluated, and it will be shown that the proposed design is not only feasible but meets the goal of designing an SOFC with a power density of 2 W/cm3 operating at or below 650 C.

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Dissertation (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

No description available.

Ceramic cellular solids, mainly honeycombs and foams, are a novel class of composite materials where one phase is an interconnected network of solid struts or plates and the other one an empty phase or possibly a fluid. Honeycombs are an array of two dimensional prismatic cells whereas in foams the arrangements of cells are three dimensional polyhedral cells. Unlike solids, the properties of honeycombs are based on three major variables i.e. a) relative density (p* /p s where p* is the density of the cellular material and ps that of the solid of which it is made) b) cell wall material and c) geometry of the cells. Because of the flexibility in tailoring these variables, cellular solids can be engineered to exhibit a unique combination of mechanical and thermal properties for diversified thermostructural applications. Ceramic based honeycombs fabricated out of cordierite (2MgO.2Al2O35SiO2), mullite (3Al2O32SiO2), cordierite: mullite (2MgO.2Al2O35SiO2) with specific configurations are the leading candidates for many of the applications such as substrates for catalytic converters, molten metal filters, air heaters and heat exchangers etc. Zirconia by the virtue of its high fracture toughness and low thermal conductivity and high refractoriness is an interesting ceramic material and explored for versatile applications. However, no significant efforts have been reported to produce zirconia/alumina and their composite based honeycomb structures and also they have not been explored for their thermo-mechanical and energy absorption based applications. In the present study, looking at the possible potential applications of the honeycombs of Zirconia/alumina and their composites such as solid oxide fuel cells, high temperature filters, blast protection tiles etc., attempts are made to fabricate honeycomb structures. Chapter 1 of the thesis describes the detailed literature survey that has been carried out using advanced search packages regarding the evolution of ceramic honeycomb structures and their properties followed by the advantages of zirconia/alumina and their composites as candidate materials for targeted applications. Literature survey also covers the various processing techniques, characterization procedures with special emphasis on the thermo-mechanical properties. Chapter II describes attempts on developing an optimum scheme of processing of zirconia honeycomb which includes selection of precursor oxides, mixing of formulations, dough making based on viscosity measurements, shaping by extrusion, microwave drying, debinding and sintering to obtain the defect free monolithic structures keeping in view of the scale up possibilities. The chapter also describes a specially developed die fabrication process with innovative machining procedures. (Patent no. 198045). Sintered honeycombs were also characterized for their critical physiochemical properties. In chapter III mechanical characterization of honeycomb samples is reported after subjecting them to compression testing with varying cell channel orientation, compositions and configurations. It is observed that all honeycombs, irrespective of the composition and configuration exhibited anisotropic behavior. In addition, the anisotropy increases with the rib thickness and decreases with increase in the unit cell length. Thermal conductivity measurement studies of the honeycombs are reported in chapter IV. Two types of measurement techniques viz. laser diffraction and monotonic heating technique have confirmed the reduction of thermal conductivity of the honeycomb samples as compared to their solid counterpart. It is observed that the finer channel honeycombs offer low thermal conductivity as compared to the coarser channel when tested across the channel direction. For equivalent relative density, the thermal conductivity value for triangular channel is found to be more as compared to the square channel. Also, the thermal conductivity values were found less when measured across the channel as compared to the values when measured along the channels. The thermal conductivity value for fine channel zirconia-alumina composite honeycombs was found much less than the thermal conductivity of the alumina matrix. Chapter V summarises the implications of the study, conclusions and the target applications.

Axxor is one the main leader in paper honeycomb production by supplying automotive, furniture, and door manufacturers. Paper honeycomb material holds the lead over any existing cores in performance, price and density ratio. The main drawback of PHC products is its lack of water/fire resistance which reduces significantly its scope of applications. Consequently, the Axxor company intends to perform a new type of product which could withstand a water exposition: impregnated paper honeycomb. By coating the paper honeycomb cellulose fibers, the mechanical properties are significantly improved with three times higher compressive strength compared to PHC. Two impregnated resins have been selected for a potential large scale production: Epoxy and Polyurethane resins. The totality of IPHC is produced through two processes which are a manual impregnation performed by hand or a continuous impregnation performed by an impregnation machine. With these independent variables in mind, this study concerns the degree of water resistance by comparing three IPHC samples: - Epoxy IPHC performed with handmade impregnation - Polyurethane IPHC performed with handmade impregnation - Polyurethane IPHC performed with the impregnation machine (higher resin content) By using the available characterization devices, water resistance is defined by measuring the decreases of the mechanical performances depending on the remaining water content in each samples.