ELECTRORHEOLOGICAL EFFECT IN SUSPENSIONS OF AgI/Ag2O/V2O5/P2O5 GLASSES

Abstract

The ER effect results from bulk and surface electric polarization processes in solid grains of ER suspensions but detailed mechanisms are not very clear. The aim of the present study was to find correlations between the character of bulk charge transport processes (electronic and/or ionic) in particles of a dispersion and parameters of the ER effect. As the dispersed phase we used glasses comprising oxides of silver, vanadium and phosphorus with addition of silver iodide. Bulk electric properties of this material could be modified without changing other properties influencing the ER effect like porosity, shape of grains, hardness, affinity to a liquid matrix etc. Variations of concentration of the components result in changes of ionic and electronic conductivity whilst other properties remain constant. The suspensions of the powdered glasses showed relatively high ER effect. The dynamic yield stress figured from 35 to 160 Pa at 2.0kV/mm for 12% concentration by volume. The highest values were observed for ionically conducting samples. The values of relaxation frequencies ( f R ) based on bulk properties of the glass sample were calculated and correlated with the yield stress whose maximum was obtained for samples of f R close to 100 kHz. High ER effect was observed also for samples of f R in the MHz range but in this case different polarization mechanism was postulated. The influence of polarization mechanisms on rheological behavior of the prepared fluids was discussed.