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Many processes contribute to the overall impedance of an electrochemical cell, and these may be difficult to separate in the impedance spectrum. Here, we present an investigation of a solid oxide fuel cell based on differences in impedance spectra due to a change of operating parameters and present the result as the derivative of the impedance with respect to ln(f) . The method is used to separate the anode and cathode contributions and to identify various types of processes.

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Battery systems based on alkali metal anodes and solid solution cathodes,i.e., cathodes based on the insertion of the alkali cation in a “host lattice,” show considerable promise for high energy density storage batteries. This paper discusses the interaction between battery requirements, in particular for vehicle propulsion, and electrochemical and constructional factors. It is argued that the energy obtainable at a given load is limited by saturation of the surface layers of cathode particles with cations, and that the time before saturation occurs is determined by diffusion of cations and electrons into the host lattice. Expressions are developed for plane, cylindrical, and spherical particles, giving the relation between battery load and the amount of cathode material utilized before saturation. The particle shape and a single parameter Q is used to describe cathode performance. Q is the ratio between discharge time at 100% utilization of the cathode at the given load, and the time constant for diffusion through the cathode particles. This description is extended to cover short peak loads characteristic of vehicle propulsion. On the basis of estimated parameters for the normalLi/TiS2 couple with LiClO4‐normalpropylene‐normalcarbonate electrolyte the properties of plane cathodes or cathodes consisting of few layers of particles are examined in relation to traction requirements. In this context limiting currents in the electrolyte phase are discussed, and a relation between the maximal allowed values for particle size and electrode spacing is derived. For nonporous electrodes the limiting factor is cathode surface saturation. A qualitative discussion of porous cathodes indicates that the cathode thickness, and thus the over‐all specific energy, is limited by cation transport in the pore electrolyte when the cation diffusion coefficient in the solid exceeds 10−10 cm2 sec−1. On the basis of an approximate relation between cathode thickness and electrode spacing the specific energy for the normalLi/TiS2 system with organic electrolyte is estimated to be 120–150 W‐hr/kg in agreement with published values.

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Abstract:We report on a detailed study of the inscription and characterization of fiber Bragg gratings (FBGs) in commercial step index polymer optical fibers (POFs). Through the growth dynamics of the gratings, we identify the effect of UV-induced heating during the grating inscription. We found that FBGs in annealed commercial POFs can offer more stable short-term performance at both higher temperature and larger strain. Furthermore, the FBGs' operational temperature and strain range without hysteresis was extended by the annealing process. We identified long-term stability problem of even the annealed POF FBGs. [7][8][9][10][11][12][13][14][15][16]. 325nm has been employed as a mainstream wavelength for writing grating in PMMA POFs [1][2][3][4][5][8][9][10][11][12][13][14][15]. Other wavelength such as 355nm obtained from a frequency-tripled Nd:YAG laser has been used to write grating in CYTOP fiber developed by Asahi Glass Co. and Keio University [15,16]. On the other hand, 800nm femtosecond pulses from Ti:Sapphire laser or its double frequency was mainly used for point by point direct writing [6] or grating writing with a phasemask [7]. However, the mechanism of index change does not appear to be fully understood [5,13,[18][19][20]. It is believed that more than one process is involved in the photo-induced refractive index changes and hence in the grating formation dynamics [18][19][20]. The widely accepted point is that the principle mechanism of index change is an increase due to the photo-induced polymerization of the unreacted monomers [5,[18][19][20], while laser-induced heating in the irradiated region during the inscription may also contribute to the index change [5]. Previous reports indicated that annealing of the POF before FBG inscription can relieve the frozen-in stress induced by the fiber drawing process [21] and increase the linear operation temperature range of FBGs [22]. However, the effect of annealing on the strain sensitivity performance was not yet considered. Polymer optical FBGs have shown great potential for sensor applications to sense for example temperature and strain with higher sensitivity and wider tunability than its silica counterpart [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Those advantages are due to the lower Young's modulus and higher thermo-optic coefficient of POFs [23,24]. In addition, polymers are clinically

This review gives first a brief view of the potential availability of sustainable energy. It is clear that over 100 times more solar photovoltaic energy than necessary is readily accessible and that practically available wind alone may deliver sufficient energy supply to the world. Due to the intermittency of these sources, effective and inexpensive energy-conversion and storage technology is needed. Motivation for the possible electrolysis application of reversible solid-oxide cells (RSOCs), including a comparison of power-to-fuel/fuel-to-power to other energy-conversion and storage technologies is presented. RSOC electrochemistry and chemistry of H2O, CO2, H2, CO, CnHm (hydrocarbons) and NH3, including thermodynamics and cell performance, are described. The mechanical strength of popular cell supports is outlined, and newly found stronger materials are mentioned. Common cell-degradation mechanisms, including the effect of common impurities in gases and materials (such as S and Si), plus the deleterious effects of carbon deposition in the fuel electrode are described followed by explanations of how to avoid or ease the consequences. Visions of how RSOCs powered by sustainable energy may be applied on a large scale for the transportation sector via power-to-fuel technology and for integration with the electrical grid together with seasonal storage are presented. Finally, a brief comparison of RSOCs to other electrolysis cells and an outlook with examples of actions necessary to commercialize RSOC applications are sketched.