Microbial fuel cells were designed and operated using waste activated sludge as a substrate and as a source of microorganisms for the anodic chamber. Waste activated sludge provided a bacterial consortium predisposed to the solubilization of particulate matter and utilization of substrates commonly found in wastewater. Dissolved oxygen and ferricyanide were used as the electron acceptors in the catholytes. Microbial fuel cell comparisons were made while operating under identical conditions but using the two different electron acceptors. Comparisons were based on the electricity production observed during MFC operation, wastewater quality of the waste activated sludge anolytes and the community level physiological profiling of the microbial communities in the anolytes. Electrons liberated during substrate utilization in the anodic chamber traveled to the cathodic chamber where they reduced the electron acceptors. The anode and cathode chambers were connected by a Nafion ® proton exchange membrane to allow for cation migration. Various soluble carbon sources were dosed to the microbial fuel cells at measured intervals during operation via direct injection to the anolyte. During bovine serum albumin dosing, average power production levels reached 0.062 mW and 0.122 mW for the dissolved oxygen microbial fuel cell and the ferricyanide microbial fuel cell, respectively. These were 100% and 25% greater than the power production levels observed throughout the rest of the study. Increases in current production were observed following the dosing of sodium acetate, glucose and bovine serum albumin. No increase in current was observed following glycerol dosing. Sodium acetate dosing triggered an immediate response, while glucose and bovine serum albumin responded in approximately 2 minutes. A chemical oxygen demand mass balance was calculated for both microbial fuel cells. The lack of balance closure was attributed to unmeasured methane production. An accumulation of particulate waste activated sludge components was observed for both microbial fuel cells. The anolyte pH during operation was typically less than waste activated sludge pH, which was attributed to volatile fatty acid accumulation in the anolytes during fermentation processes. Community level physiological profiling was accomplished through the analysis of ecological data obtained with BIOLOG ® ECOplates. Samples were plated and analyzed under anaerobic conditions, mimicking the environment in the anode chamber of the MFCs. ECOplate data were transformed by a logarithmic function prior to principle component analysis. The community level physiological profiling indicated that shifts in the microbial community profile, as measured through the carbon source utilization patterns, occurred throughout acclimation and following the dosing of various carbon source substrates. Shifts due to glycerol dosing differed from shifts due to the dosing of sodium acetate, glucose and bovine serum albumin.

Distributed generation is expected to play a significant role in remedying the many shortcomings in today’s energy market. In particular, fuel cell power generation will play a big part due to several advantages. Still, it is faced with its own challenges to tap into its potential as a solution to the crisis. The responsibilities of the Power Conditioning Unit (PCU), and thus its design, are therefore complex, yet critical to the fuel cell system’s performance and ability to meet the requirements. To this end, the dc-dc converter, considered the most critical component of the PCU for optimum performance, is closely examined. The selected converter is first modeled to gain insight into its behavior for the purpose of designing suitable compensators. MATLAB is then used to study the results using the frequency domain, and it was observed that the converter offers its own unique challenges in terms of closed-loop performance and stability. These limitations must therefore be carefully accounted for and compensated against when designing the control loops to achieve the desired objectives. Negative feedback control to ensure robustness is then discussed. The insertion of a second inner loop in Current Mode Control (CMC) offers several key advantages over single-loop Voltage Mode Control (VMC). Furthermore, the insertion of a Current Error Amplifier (CEA) in Average Current Mode Control (ACMC) helps overcome many of the problems present in Peak Current Mode Control (PCMC) whilst allowing much needed design flexibility. It is therefore well suited for this application in an attempt to improve the dynamic behavior and overcoming the shortcomings inherent in the converter. The modulator and controller for ACMC are then modeled separately and combined with the converter’s model previously derived to form the complete small-signal model. A suitable compensation network is selected based on the models and corresponding Bode plots used to assess the system’s performance and stability. The resulting Bode plot for the complete system verifies that the design objectives are clearly met. The complete system was also built in MATLAB/Simulink, and subjected to external disturbances in the form of stepped load changes. The results confirm the system’s excellent behavior despite the disturbance, and the effectiveness of the control strategy in conjunction with the derived models. To meet the demand in many applications for power sources with high energy density and high power density, it is constructive to combine the fuel cell with an Energy Storage System (ESS). The hybrid system results in a synergistic system that brings about numerous potential advantages. Nevertheless, in order to reap these potential benefits and avoid detrimental effects to the components, a suitable configuration and control strategy to regulate the power flow amongst the various sources is of utmost importance. A robust and flexible control strategy that allows direct implementation of the ACMC scheme is devised. The excellent performance and versatility of the proposed system and control strategy are once again verified using simulations. Finally, experimental tests are also conducted to validate the results presented in the dissertation. A scalable and modular test station is built that allows an efficient and effective design and testing process of the research. The results show good correspondence and performance of the models and control design derived throughout the thesis.

Vehicle design and control is an attractive area of research in that it embodies a convergence of societal need, technical limitation, and emerging capability. Environmental, political, and monetary concerns are driving the automotive industry towards sustainable transportation, manifested as increasing powertrain electrification in a gradual transition to fossil-free energy vectors. From an electrochemical degradation and control systems perspective, this transition introduces significant technical uncertainty. Initial indications are that the initial battery designs will have twice the required capacity due to degradation concerns. As the battery is a major contributor to the cost of these vehicles the over-sizing represents a significant threat to the ability of OEMs to produce cost-competitive vehicles. This potential barrier is further amplified when the combustion engine is removed and battery-electric or fuel-cell hybrid vehicles are considered. This thesis researches the application of model-based design for optimal design of fuel cell hybrid powertrains considering power source degradation. The intent is to develop and evaluate tools that can determine the optimal sizing and control of the powertrain; reducing the amount of over-sizing by numerically optimization rather than a sub-optimal heuristic design. A baseline hybrid fuel cell vehicle model is developed and validated to a hybrid fuel cell SUV designed and built at the University of Waterloo. Lithium-ion battery degradation models are developed and validated to data captured off a hybrid powertrain test stand built as part of this research. A fuel cell degradation model is developed and integrated into the vehicle model. Lifetime performance is modeled for four hybrid control strategies, demonstrating a significant impact of the hybrid control strategy on powertrain degradation. A plug-in variation of the architecture is developed. The capacity degradation of the battery is found to be more significant than the power degradation. Blended and All-electric charge-depleting hybrid control strategies are integrated and lifetime performance is simulated. The blended charge-depleting control strategy demonstrated significantly less degradation than the all-electric strategy. An oversized battery is integrated into the vehicle model and the benefit of oversizing on reducing the battery degradation rate is demonstrated.

There has always been a desire to develop industrial processes that minimize the resources they use, and the wastes they generate. The problem is when new guidelines are forced upon long established processes, such as solvent based coating operations. This means instead of integrating an emission reduction technology into the original design of the process, it is added on after the fact. This significantly increases the costs associated with treating emissions. In this work the ultimate goal is the design of an “add-on” abatement system to treat emissions from solvent based coating processes with high destruction efficiency, and lower costs than systems in current use. Since emissions from processes that utilize solvent based coatings are primarily comprised of volatile organic compounds (VOCs), the treatment of these compounds will be the focus. VOCs themselves contain a significant amount of energy. If these compounds could be destroyed by simultaneously extracting the energy they release, operational costs could be substantially reduced. This thesis examines the use of model-based design to develop and optimize a VOC abatement technology that uses a Solid Oxide Fuel Cell (SOFC) for energy recovery. The model was built using existing HYSYS unit operation models, and was able to provide a detailed thermodynamic and parametric analysis of this technology. The model was validated by comparison to published literature results and through the use of several Design of Experiment factorial analyses. The model itself illustrated that this type of system could achieve 95% destruction efficiency with performance that was superior to that of Thermal Oxidation, Biological Oxidation, or Adsorption VOC abatement technologies. This was based upon design criteria that included ten year lifecycle costs and operational flexibility, as well as the constraint of meeting (or exceeding) current regulatory thresholds.

Polymer electrolyte membrane (PEM) fuel cells have increasingly become promising green energy sources for automobile and stationary cogeneration applications but its success in commercialization depends on performance optimization and manufacturing cost. The activation losses, expensive platinum catalyst, and water flooding phenomenon are the key factors currently hindering commercialization of PEM fuel cells. These factors are associated with the cathode catalyst layer (CCL), which is about ten micrometers thick. Given the small scale of this layer, it is extremely difficult to study transport phenomena inside the catalyst layer experimentally, either intrusively or non-intrusively. Therefore, mathematical and numerical models become the only means to provide insight on the physical phenomena occurring inside the CCL and to optimize the CCL designs before building a prototype for engineering application. In this thesis research, a comprehensive two-phase mathematical model for the CCL has been derived from the fundamental conservation equations using a volume-averaging method. The model also considers several water transport and physical processes that are involved in the CCL. The processes are: (a) electro-osmotic transport from the membrane to the CCL, (b) back-diffusion of water from the CCL to the membrane, (c) condensation and evaporation of water, and (d) removal of liquid water to the gas flow channel through the gas diffusion layer (GDL). A simple analytical model for the activation overpotential in the CCL has also been developed and an optimization study has been carried out using the analytical activation overpotential formulation. Further, the mathematical model has been simplified for the CCL and an analytical approach has been provided for the liquid water transport in the catalyst layer. The volume-averaged mathematical model of the CCL is finally implemented numerically along with an investigation how the physical structure of a catalyst layer affects fuel cell performance. Since the numerical model requires various effective transport properties, a set of mathematical expressions has been developed for estimating the effective transport properties in the CCL and GDL of a PEM fuel cell. The two-dimensional (2D) numerical model has been compared with the analytical model to validate the numerical results. Subsequently, using this validated model, 2D numerical studies have been carried out to investigate the effect of various physical and wetting properties of CCL and GDL on the performance of a PEM fuel cell. It has been observed that the wetting properties of a CCL control the flooding behavior, and hydrophilic characteristics of the CCL play a significant role on the cell performance. To investigate the effect of concentration variation in the flow channel, a three-dimensional numerical simulation is also presented.

Solid oxide fuel cells (SOFCs) conventionally operate between 800 and 1000°C. The barriers for full-scale commercialization of SOFCs are the high cost and relatively poor long-term stability due to the high temperatures used in current state-of-the-art SOFCs. One solution is to decrease the operating temperature, e.g. to 550-750°C but this requires developing new electrolytes and electrode materials. Also, to increase efficiency and practicality, the anode should be able to internally reform hydrocarbon fuels especially methane because it is the most common hydrocarbon in natural gas. The overall goal of this research is to develop a coke-tolerant Ni1-x-yCuxMgyO-SDC anode for methane fuelled IT-SOFCs. The Ni-Cu-Mg-O-SDC anode has been chosen based on the premises that doped-ceria is suitable for intermediate operating temperatures (550-800°C), Ni is known as an active metal and good electronic conductor, Cu increases resistance to coking, MgO helps prevent agglomeration of Ni during reduction, and finally SDC improves oxide ion transport to the cell at this intermediate temperature range. In this work, these materials were characterized in three primary ways: material physical and chemical properties, methane steam reforming activity and electrochemical performance. Two different methods have been used to add Cu to Ni1-yMgyO: a one-step co-precipitation method and a two-step co-precipitation/impregnation method. For the first method, Ni1-x-yCuxMgyO was synthesized via co-precipitation of Ni, Mg and Cu. In the two-step method, Ni0.9Mg0.1O was first prepared by co-precipitation, followed by addition of copper to Ni0.9Mg0.1O by impregnation. However, co-precipitation of all metal in one step limits the sintering temperature of the anode in the cell fabrication due to the low boiling point of CuO. Therefore, co-precipitation of Cu is not a practical method and only Cu impregnation should be considered for practical SOFC applications. It was found that the addition of Mg (Ni0.9Mg0.1O) lowers the reducibility of NiO. Addition of Cu to Ni0.9Mg0.1O up to 5% shows similar reducibility as Ni0.9Mg0.1O. The reducibility of Ni1-x-yCuxMgyO becomes lower when the Cu content is increased to 10%. Nonetheless, all materials are fully reduced at 750ºC. The XRD patterns of pure NiO, Ni0.9Mg0.1O, and the Cu-containing material when Cu is less than 10 mol% are similar. The lower reducibility of Ni-Mg-O and Ni-Cu-Mg-O compared to NiO indicates that they form a solid solution with NiO as the matrix. Solid oxide fuel cells (SOFCs) conventionally operate between 800 and 1000°C. The barriers for full-scale commercialization of SOFCs are the high cost and relatively poor long-term stability due to the high temperatures used in current state-of-the-art SOFCs. One solution is to decrease the operating temperature, e.g. to 550-750°C but this requires developing new electrolytes and electrode materials. Also, to increase efficiency and practicality, the anode should be able to internally reform hydrocarbon fuels especially methane because it is the most common hydrocarbon in natural gas. The overall goal of this research is to develop a coke-tolerant Ni1-x-yCuxMgyO-SDC anode for methane fuelled IT-SOFCs. The Ni-Cu-Mg-O-SDC anode has been chosen based on the premises that doped-ceria is suitable for intermediate operating temperatures (550-800°C), Ni is known as an active metal and good electronic conductor, Cu increases resistance to coking, MgO helps prevent agglomeration of Ni during reduction, and finally SDC improves oxide ion transport to the cell at this intermediate temperature range. In this work, these materials were characterized in three primary ways: material physical and chemical properties, methane steam reforming activity and electrochemical performance. Two different methods have been used to add Cu to Ni1-yMgyO: a one-step co-precipitation method and a two-step co-precipitation/impregnation method. For the first method, Ni1-x-yCuxMgyO was synthesized via co-precipitation of Ni, Mg and Cu. In the two-step method, Ni0.9Mg0.1O was first prepared by co-precipitation, followed by addition of copper to Ni0.9Mg0.1O by impregnation. However, co-precipitation of all metal in one step limits the sintering temperature of the anode in the cell fabrication due to the low boiling point of CuO. Therefore, co-precipitation of Cu is not a practical method and only Cu impregnation should be considered for practical SOFC applications. It was found that the addition of Mg (Ni0.9Mg0.1O) lowers the reducibility of NiO. Addition of Cu to Ni0.9Mg0.1O up to 5% shows similar reducibility as Ni0.9Mg0.1O. The reducibility of Ni1-x-yCuxMgyO becomes lower when the Cu content is increased to 10%. Nonetheless, all materials are fully reduced at 750ºC. The XRD patterns of pure NiO, Ni0.9Mg0.1O, and the Cu-containing material when Cu is less than 10 mol% are similar. The lower reducibility of Ni-Mg-O and Ni-Cu-Mg-O compared to NiO indicates that they form a solid solution with NiO as the matrix. Addition of Mg also lowers the BET specific surface area from 11.5 m2/g for NiO:SDC to 10.4 m2/g for Ni0.9Mg0.1O. The surface area is further reduced when Cu is added; for example, at 10% Cu, the surface area is 8.2 m2/g. The activity of 50wt% Ni1-x-yCuxMgyO/50wt% SDC samples for methane steam reforming (SMR) and water-gas-shift reaction (WGS) was evaluated in a fully automated catalytic fixed-bed reactor where the exiting gases were analyzed online by a gas chromatograph (GC). The tests were performed at steam-to-carbon ratios (S/C) of 3, 2 and 1, and at temperatures of 750°C and 650°C for twenty hours. Higher methane conversions were obtained at the higher temperature and higher S/C ratio. Higher methane conversion are obtained using NiO:SDC and Ni0.9Mg0.1O:SDC than Ni-Cu-Mg-O. The conversion decreases with increasing Cu content. Over NiO:SDC and Ni0.9Mg0.1O:SDC the methane conversions are the same; for example 85% at 750°C for S/C of 3. At the same conditions, impregnation of 5%Cu and 10%Cu yields lower conversions: 62% and 48%, respectively. The activity for the WGS reaction was determined by mornitoring CO2/(CO+CO2) ratio. As expected because WGS is a moderately exothermic reaction, this ratio decreases when increasing the temperature. However, the CO2/(CO+CO2) ratio increases with higher S/C. The results indicate that adding Mg does not affect the WGS activity of NiO. The WGS activity of Ni0.9Mg0.1O:SDC is higher when Cu is added. The effect of additional Cu is more pronounced at 650ºC. At 750°C, changing the amount of Cu does not change the WGS activity because the WGS reaction rapidly reaches equilibrium at this high temperature. At 750°C for S/C of 1, carbon filaments were found in all samples. At 650ºC, different types of deposited carbon were observed: carbon fibers and thin graphite layers. Spent NiO:SDC had the longest carbon fibers. Addition of Mg significantly reduced the formation of carbon fibers. Impregnating 5% Cu on Ni0.9Mg0.1O:SDC did not change the type of deposited carbon. Monitoring the amount of deposited carbon on Ni0.9Mg0.1O:SDC, 3%Cu and 5%Cu impregnated on Ni0.9Mg0.1O:SDC for S/C of 0 at 750ºC showed that Cu addition deactivated methane cracking causing a reduction in the amount of carbon deposited. Electrochemical performance in the presence of dry and humidified hydrogen was determined at 600, 650, 700 and 750ºC. Electrolyte-supported cells constructed with four different anodes were tested using polarization curve and electrochemical impedance spectra. The four anodes were NiO:SDC, Ni0.9Mg0.1O:SDC, 3%Cu and 5%Cu on Ni0.9Mg0.1O:SDC. Adding Mg improved the maximum power density from 356 mW.cm-2 with NiO:SDC to 369 mW.cm-2 with Ni0.9Mg0.1O:SDC at 750ºC in dry hydrogen. Addition of Cu, on the other hand, lowered the maximum power density to 325 mW.cm-2 with 3%Cu impregnated and to 303 mW.cm-2 with 5% Cu impregnated. The cell with Ni0.9Mg0.1O:SDC was also tested under dry methane. To minimize methane cracking under this extreme condition, a current density of 0.10 A.cm-2 was always drawn when methane was present in the feed. The voltage decreased during the first hour from 0.8 to 0.5 V, then remained stable for 10 hours, and then started to drop again. Many small cracks were observed on the anode after completion of the electrochemical test, but there was no evidence of much carbon being deposited. In addition to dry methane, tests were also carried out, using the same material, with a H2O/CH4 mixture of 1/6 in order to generate a polarization curve at 750°C. Under these conditions, the maximum power density was 226 mW.cm-2. This is lower than the maximum power density obtained with humidified hydrogen, which was 362 mW.cm-2.

Polymer electrolyte membrane fuel cells (PEMFCs) have the potential to play a major role as energy generators for transportation and portable applications. One of the current barriers to their commercialization is the cost of the components and manufacturing, specifically the bipolar plates. One approach to preparing PEMFCs for commercialization is to develop new bipolar plate materials, related to mass production of fuel cells. Thermoplastic/carbon filler composites with low filler loading have a major advantage in that they can be produced by a conventional low-cost injection molding technique. In addition, the materials used are inexpensive, easy to shape, and lightweight. An optimal bipolar plate must possess high surface and bulk electronic conductivity, sufficient mechanical integrity, low permeability, and corrosion resistance. However, it is difficult to achieve high electrical conductivity from a low-cost thermoplastic composite with low conductive filler loading. Concerns over electrical conductivity improvement and the injection processability of composites have brought forth the idea of producing a polypropylene/three-carbon-filler composite for bipolar plate application. The thesis addresses the development of synergistic effects of filler combinations, investigating composite conductive materials and using composite bipolar plate testing in PEMFCs. One significant effect of conductive network formation is the synergetic effects of different carbon filler sizes, shapes, and multiple filler ratios on the electrical conductivity of bipolar plate materials. A polypropylene resin combined with low-cost conductive fillers (graphite, conductive carbon black, and carbon fibers with 55 wt% of filler loading) compose the main composite for all investigations in this research. Numerous composite formulations, based on single-, two-, and three-filler systems, have been created to investigate the characteristics and synergistic effects of multiple fillers on composite conductivity. Electrical conductivity measurements corresponding to PEMFC performance and processing characteristics were investigated. Experimental work also involved other ex-situ testing for the physical requirements of commercial bipolar plates. All combinations of fillers were found to have a significant synergistic effect that increased the composite electrical conductivity. Carbon black was found to have the highest influence on the increase of electrical conductivity compared to the other fillers. The use of conjugated conducting polymers such as polypyrrole (PPy) to help the composite blends gain desirable conductivities was also studied. Electrical conductivity was significantly improved conductivity by enriching the conducting paths on the interfaces between fillers and the PP matrix with PPy. The conductive network was found to have a linkage of carbon fibers following the respective size distributions of fibers. The combination of Fortafil and Asbury carbon fiber mixture ameliorated the structure of conductive paths, especially in the through-plane direction. However, using small fibers such as carbon nanofibers did not significantly improve in electrical conductivity. The useful characteristics of an individual filler and filler supportive functions were combined to create a novel formula that significantly improved electrical conductivity. Other properties, such as mechanical and rheological ones, demonstrate the potential to use the composites in bipolar plate applications. This research contributes a direction for further improvement of marketable thermoplastic bipolar plate composite materials.

A single polymer electrolyte membrane fuel cell (PEMFC) is comprised of several sub-millimetre thick layers of varying porosity sandwiched together. The thickness of each layer, which typically ranges from 10 to 200μm, is kept small in order to minimize the transport resistance of heat, mass, electrons, and protons, that limit reaction rate. However, the thickness of these materials presents a significant challenge to engineers characterizing the transport properties through them, which is of considerable importance to the development and optimization of fuel cells. The objective of this research is to address the challenges associated with measuring the heat conduction and gas diffusion transport properties of thin porous media used in PEMFCs. An improvement in the accuracy of the guarded heat flow technique for measuring thermal conductivity and the modified Loschmidt Cell technique for measuring gas diffusivity are presented for porous media with a sub-millimetre thickness. The improvement in accuracy is achieved by analyzing parameters in each apparatus that are sensitive to measurement error and have the largest contribution to measurement uncertainty, and then developing ways to minimize the error. The experimental apparatuses are used to investigate the transport properties of the gas diffusion layer (GDL) and the microporous layer (MPL), while the methods would also be useful in the study of the catalyst layer (CL). Gas diffusion through porous media is critical for the high current density operation of a PEMFC, where the electrochemical reaction becomes rate-limited by the diffusive flux of reactants reaching reaction sites. However, geometric models that predict diffusivity of the GDL have been identified as inaccurate in current literature. Experimental results give a better estimate of diffusivity, but published works to date have been limited by high measurement uncertainty. In this thesis, the effective diffusivity of various GDLs are measured using a modified Loschmidt cell and the relative differences between GDLs are explained using scanning electron microscopy and the method of standard porosimetry. The experimental results from this study and others in current literature are used to develop a generalized correlation for predicting diffusivity as a function of porosity in the through-plane direction of a GDL. The thermal conductivity and contact resistance of porous media are important for accurate thermal analysis of a fuel cell, especially at high current densities where the heat flux becomes large. In this thesis, the effective through-plane thermal conductivity and contact resistance of the GDL and MPL are measured. GDL samples with and without a MPL and coated with 30%-wt. PTFE are measured using the guarded steady-state heat flow technique described in the ASTM standard E 1225-04. Thermal contact resistance of the MPL with the iron clamping surface was found to be negligible, owing to the high surface contact area. Thermal conductivity and thickness of the MPL remained constant for compression pressures up to 15bar at 0.30W/m°K and 55μm, respectively. The thermal conductivity of the GDL substrate containing 30%−wt. PTFE varied from 0.30 to 0.56W/m°K as compression was increased from 4 to 15bar. As a result, the GDL contain- ing MPL had a lower effective thermal conductivity at high compression than the GDL without MPL. At low compression, differences were negligible. The constant thickness of the MPL suggests that the porosity, as well as heat and mass transport properties, remain independent of the inhomogeneous compression by the bipolar plate. Despite the low effective thermal conductivity of the MPL, thermal performance of the GDL can be improved by exploiting the excellent surface contact resistance of the MPL while minimizing its thickness.

Recent developments in powder metal oxide processing have enabled co-extrusion of a honeycomb structure with alternating layers of metal and ceramic. Such a structure is envisioned for use as a Solid Oxide Fuel Cell (SOFC) if defects can be minimized during the manufacturing process. The two dissimilar materials tend to shrink at different rates during hydrogen reduction and sintering, inducing internal stresses that lead to structural defects such as cracks, or high residual stresses. The objective of this thesis is to characterize the shrinkage and relaxation mechanisms inherent in both the metal and ceramic so that internal stresses developed during manufacturing can be estimated and ultimately minimized. Constitutive models are adapted from the literature to simulate the sintering and viscoelastic behaviors of the ceramic. Likewise, existing models in the literature are used to characterize the viscoplastic relaxation of the porous powder metal phase and its sintering behavior. Empirical models are developed for the reduction behavior of the metal oxides, based on a series of experiments conducted that measure water vapor (hygrometry) and dimensional change (dilatometry) during reduction and sintering. Similarly, the necessary parameters for the sintering model and viscoplastic model were determined through a series of experiments. The constructed system of constitutive equations appears to have the essential elements for modeling dimensional change, porosity/strength and development of internal (residual) stresses in co-extruded SOFC structures.

A program of study has been established for the quantitative study of electrode reactions in solid oxide fuel cells. The initial focus of the program is the mixed conducting cathode material strontium-doped lanthanum manganate (LSM). A formalism was established treating reactions taking place at the gas-exposed surface of mixed conducting electrodes. This formalism was incorporated into a phenomenological model for oxygen reduction in LSM, which treats the phenomenon of sheet resistance. Patterned electrodes were designed that reduce the dimensionality of the appropriate model, and these electrodes were successfully fabricated using DC sputtering and photolithography. A new model for the bulk defect equilibrium in LSM was proposed and shown to be a better fit to nonstoichiometry data at low temperatures. The fitting was carried out with a particle swarm optimizer and a rigorous method for identification. It was shown that a model for the interface structure between LSM and yttria-stabilized zirconia (YSZ) that assumes free oxygen vacancies in YSZ does not accord with experimental observations. Cluster variation method (CVM) was adapted for analysis of the problem, and a new analytical method combining CVM and electrical contributions to the free energy was proposed.