Polarisation early developments

Impedance Some of the errors arising from the use of linear polarisation resistance led to interest and development in a.c. systems.An early development used a fixed a.c. frequency and a commercial instrument was produced in the UK. Inaccuracies still occurred, however, and were due to the electrode impedance which is fequency dependent. Electrode reactions have a capacitance component, in addition to resistance, resulting in a requirement to measure the impedance. However, the total impedance comprises values for the reaction, solution, diffusion and capacitance. Measurements at different frequency are more reliable, particularly where high solution resistances occur. Simplifications for industrial monitoring have been developed consisting of two measurements, i.e. at a high (10 kHz) and low frequency (0-1 Hz). The high-frequency measurement can identify the... 

Since the heroic early mechanistic investigations, there have been two developments of major significance in radical chemistry. The first was the advent of electron spin resonance (ESR) spectroscopy (and the associated technique of chemically induced dynamic nuclear polarisation, CIDNP) [24], which provided structural as well as kinetic information the second is the more recent development of a wide range of synthetically useful radical reactions [20]. Another recent development, the combination of the pulse radiolysis and laser-flash photolysis techniques, is enormously powerful for the study of radicals but beyond the scope of this book. 

Another technique in an early stage of development - spin polarised electron energy loss spectroscopy (SPEELS) - is expected to have particularly strong impact on rare earth surface science. In electron spectrometers with good temperature control of the sample the technique should unfold a wealth of interesting magnetic phases at surfaces and in ultra thin films on substrates. 

Just as important as these developments in magnet design has been the introduction of pulsed Fourier transform methods, for these permit the performance of new types of experiment by the computerised systems that control the production, acquisition and processing of the experimental data. New pulse sequences increasingly made available by instrument manufacturers within their software suites permit the routine performance of these new experiments an early example is the distortionless enhancement polarisation transfer, or DEPT, experiment to identify the number of protons attached to a carbon by controlling the final... 

The basic concepts of composite or single-phase MIEC electrodes are equally applicable to anodes. Traditionally, however, the typical anode used to date has been a composite mixture of Ni and YSZ. The presence of YSZ not only suppresses the thermally induced coarsening of Ni, but it also introduces MIEC characteristics. Other anodes currently under investigation are based on cermets of copper, which are being explored for direct oxidation of hydrocarbon fuels [39]. These types of anodes are in an early stage of development and thus their polarisation behavior is not discussed here. In so far as single-phase anodes are concerned, some work has been reported in the literature, most notably on La-SrTi03 [40, 41]. Work on this as well as other perovskite-based anodes is in its infancy, and is not elaborated upon further. The discussion in this chapter is confined to Ni + YSZ cermet anodes. 

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