High-voltage electron paramagnetic resonance study of some electro-rheological fluids

Abstract

An EPR cell has been constructed which allows voltages up to 20 kV to be applied to a sample in an EPR cavity. The cell has been used to investigate the influence of applied electric fields on spin probes dissolved in the water contained in the cavities of zeolites. Zeolite particles can be used as the active component in electro-rheological (ER) fluids, the latter being dispersions of solid particles in a non-conducting liquid. The ER-active zeolites Na-X, Na-Y, H-ZSM-5 and Na-mordenite were examined in their hydrated states with the spin probes TEMPOL, TEMPYO^– and TEMPTMA⁺ incorporated into them. It was discovered that an applied electric field reduces the mobility of TEMPOL but the negatively and positively charged spin probes are unaffected. From this preliminary investigation it seems likely that a technique can be evolved for assessing the performance of solids for use in ER fluids.