We report on actuation in high tensile strength yarns of twist-spun multi-wall carbon nanotubes. Actuation in response to voltage ramps and potentiostatic pulses is studied to quantify the dependence of the actuation strain on the applied voltage. Strains of up to 0.5% are obtained in response to applied potentials of 2.5 V. The dependence of strain on applied voltage and charge is found to be quadratic, in agreement with previous results on the actuation of single-wall carbon nanotubes, with the magnitude of strain also being very similar. The specific capacitance reaches 26 F g−1. The modulus of the yarns was found to be independent of applied load and voltage within experimental uncertainty.

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In this work, use of the galvanostatic intermittent titration technique to extract lithium ion diffusion coefficients in tin thin films is studied. The measured results are first analyzed under the traditional solid solution assumptions. The change of phase in the electrode is then modeled using a moving boundary model, which more accurately predicts the potential transients during the galvanostatic pulse.

An analytical model is presented to describe the electrochemical impedance of conducting polymer based devices. The analytical expression of the impedance is obtained from a two dimensional finite transmission line equivalent circuit. The model relates impedance to cell geometry, electrolyte conductivity, polymer ionic and electronic conductivities and capacitance. These parameters were measured for a hexafluorophosphate (PF 6 -) doped polypyrrole material (the conducting polymer used in this study) and entered to the model to predict its impedance as a function of frequency. The model is unique in representing the two dimensional charging of the polymer, namely ionic mass transport through the thickness of the polymer structure and electronic resistance along its length. Close agreement is observed between impedance spectroscopy results and model prections of the charging of a polypyrrole film electrically connected at one end. This provides a means of modeling the electrochemical charging of conducting polymers and electrochemical double layer capacitor electrodes having significant ionic and electronic conductivities.

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