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[en] The object of this program is to experimentally determine the utility of selected perovskite related solid electrolytes for application in SOFC's operating at intermediate temperatures (600-750 degrees C). Specific technical objectives addressed in this program include: Gaining useful insight into those crystallographic and thermodynamic parameters which influence both activation energy (Ea) for ionic transport and the population of ionic charge carriers. Synthesizing selected perovskite related solid electrolyte powders expected to possess (i) low Ea for ionic conduction and (ii) an intrinsically high population of ionic charge carriers. Preparing sintered solid electrolyte disks and determine their ionic conductivity. Incorporating solid electrolytes demonstrating acceptable ionic conductivity into small research size SOFC's operating at intermediate temperatures and determine their electrochemical performance. Determining the long-term stability of selected solid electrolyte materials incorporated into SOFC'S
[en] The purpose of this research is to develop alternative materials for solid oxide fuel cell (SOFC) interconnections and electrodes with improved electrical, thermal and electrochemical properties. Another objective is to develop synthesis and fabrication processes for these materials whereby they can be consolidated in air into SOFC's. The approach is to (1) develop modifications of the current, state-of-the-art materials used in SOFC's, (2) minimize the number of cations used in the SOFC materials to reduce potential deleterious interactions, (3) improve thermal, electrical, and electrochemical properties, (4) develop methods to synthesize both state-of-the-art and alternative materials for the simultaneous fabrication and consolidation in air of the interconnections and electrodes with the solid electrolyte, and (5) understand electrochemical reactions at materials interfaces and the effects of component compositions and processing on those reactions
[en] The behavior of an electrochemical integrator based on a solid electrolyte is studied in the galvanoharmonic charging mode. The possibility of applying simpler and more graphic calculation techniques and separating the impedance of electrochemical systems into active and reactive components is shown. The plotting of the dependences of the active and reactive impedance components on the ac frequency is used to determine the parameters of the studied equivalent electric cuircuits.
[en] Developed in the early 1900s, the “Haber–Bosch” synthesis is the dominant NH3 synthesis process. Parallel to catalyst optimization, current research efforts are also focused on the investigation of new methods for ammonia synthesis, including the electrochemical synthesis with the use of solid electrolyte cells. Since the first report on Solid State Ammonia Synthesis (SSAS), more than 30 solid electrolyte materials were tested and at least 15 catalysts were used as working electrodes. Thus far, the highest rate of ammonia formation reported is 1.13 × 10-8 mol s-1 cm-2, obtained at 80°C with a Nafion solid electrolyte and a mixed oxide, SmFe0.7Cu0.1Ni0.2O3, cathode. At high temperatures (>500°C), the maximum rate was 9.5 × 10−9 mol s-1 cm-2 using Ce0.8Y0.2O2-δ–[Ca3(PO4)2–K3PO4] as electrolyte and Ag–Pd as cathode. In this paper, the advantages and the disadvantages of SSAS vs. the conventional process and the requirements that must be met in order to promote the electrochemical process into an industrial level are discussed.
[en] Superionic solids and solid electrolytes are a special group of materials showing high ionic conductivity with tremendous technological potential. This book updates the present status of the field. Starting with an overview of recent trends in solid state ionics, the book ends with the assessment of future implications. Different theoretical, experimental (including NMR), and materials aspects have been covered along with applications. Important materials covered include alkali and silver ion conductors, fluorites, Nasicon, heterogeneous solid electrolytes, and glasses. The theoretical topics covered in this volume include phenomenological models, fractal techniques, the pre-exponential problem, and fluctuations
[en] Lanthan-Strontium-Manganite perowskites are the most widespread materials in use for solid oxide fuel cell cathodes. The electrode reaction taking place, i.e. the reduction of oxygen supplied by air, was investigated by electrochemical means to obtain further knowledge about the electrode processes. The high activation energy of this reaction (200 kJ/mol), preventing lower operation temperatures of the SOFC, was the starting point for the investigation. Quasi steady state current voltage measurements and impedance spectroscopy were performed in a three electrode configuration. The electrodes were of circular shape with a diameter of 10 mm. The preparation was made by screen printing as well as wet powder spraying onto plates made of Yttria-stabilized zirconia. Perowskite powders of varying chemical and stoichiometric composition were used. To obtain higher power densities and, more important, lower apparent activation energies, catalytic layers were added at the interface electrode/electrolyte. Additionally, a less complex system, a model electrode/electrolyte setup made from single-crystal YSZ as electrolyte and gold in liquid and solid state as electrode was developed to create a better defined system. This setup was used to investigate the behaviour of the electrode/electrolyte interface. Reliable, reproducible results could be obtained using either setup. The experimental conditions i.e. oxygen partial pressure, temperature and overpotential were varied in order to determine the kinetic properties of the electrodes. Apparent activation energies, pre-exponential factors, apparent charge-transfer coefficients and electrochemical orders of reaction were calculated from the current-voltage data in order to propose possible reaction steps. (orig.)
[en] Fuel cells made with solid electrolytes such as yttria stabilized zirconia (YSZ) offer many advantages for energy generation . These arise from fast electrode kinetics, a management free solid elecytrolyte of invariant composition, the ability to reform fuels and burn CO without need for CO2 recycle and an overall high system efficiency. However, several limitations hamper progress in SOFC'S: (a) the solid electrolyte has an intrinsic high resistivity (b) high temperature operation requires electrode materials which also are poorly conductive and (c) manufacturing costs are high. In order to circumvent these difficulties, Barnett  has recently proposed that the SOFC electrolyte be deposited as a thin film. The reduction in electrolyte resistivity permits lower temperature operation; conductive Ag thin films could then be used in place of oxide electrodes, and both the range of usable fuels as well as the thermodynamic reaction efficiency would be improved. The economic application of thin film techniques to fuel cell development poses unique problems. Here we describe our first attempts to demonstrate Jet Vapor Deposition (JVD) as a fast, economical route to making high quality YSZ thin film electrolyte layers for incorporation in SOFC's
[en] In order to get an understanding of the general characteristics of carbon nanotube (CNT) based actuators, the system response of the actuator was analyzed. Special techniques were developed in order to generate a reproducible characteristic measure for the material: the R-curve. In addition, the dynamic response of the system was evaluated in different states of the actuator. A model was generated to capture the general behavior of the system. Finally an actuator incorporating a solid electrolyte was built and tested, showing similar characteristics to an actuator with an aqueous electrolyte
[en] Polymer electrolytes have many attractive features which enable them to be used in 'smart' window applications. Transparency, flexibility, durability and thin-film formation make polymer electrolytes the favoured option for use as the conducting layer in electrochromic devices. A number of polymer systems were investigated including comb-branch polymer acrylate glycols (2) with bi-ionic salts such as LiCF3SO3. Single-ion conducting co-polymers were also prepared from lithiated ion-pairs of triflate (8), sulfonate (12) and carboxylate (16) end-groups within acrylate monomers, in combination with the acrylate glycol monomer (1). Macroporous poly(ethylene) films and β-cyclodextrin systems with high concentrations of 'liquid' electrolyte were analyzed using poly(ethylene glycol) 300 or dimethylacetamide and triflate salts. The conductivity of these systems ranged from 10-4 to 10-6 S cm-1. Polyglucosan gels and films led to the most promising systems, with rigid gels A and B being formed with specific formulations of Cellulose, LiCI and Dimethylacetamide or N-methylpyrrolidinone. Cellulose gels showed conductivities > 10-4 S cm-1 at ambient temperatures and had the additional advantage of 'instantaneous' colouring responses when the gels were used as the conducting layer in electrochromic devices. This allowed excellent colouring and bleaching responses on the first cycle when a voltage > 2V was applied. A major development, as cells currently on the market often require a number of completed cycles before their optimum optical transmission is reached. An example from our own studies being the acrylate glycol homopolymer (2) containing LiCF3SO3 which did not show respectable colouring or bleaching responses until > 100 cycles had been completed. A superior system was prepared utilizing the photofunctional moieties of cellulose cinnamate (16) allowing a crosslinked film to be obtained in situ. This led to fewer processing difficulties with greater mechanical stability along with all the other properties the gels had shown. The 'instantaneous' colouring response and cinnamate film analysis has been filed as Patent Application Number 9709885-9. (author)