Amorphous ceramics as the particulate phase in electrorheological materials systems
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Amorphous ceramics as the particulate phase in electrorheological materials systems Daniel R. Gamota Motorola, Corporate Manufacturing Research Center, Schaumburg, Illinois 60196
Adam W. Schubring Delco Electronics Corp., Hybrid Microelectronics Manufacturing, Kokomo, Indiana 46904
Brian L. Mueller Henkel Corporation, Parker & Amchem, Madison Heights, Michigan 48071
Frank E. Filisko Department of Materials Science and Engineering, College of Engineering, The University of Michigan, Ann Arbor, Michigan 48109-2136 (Received 24 February 1995; accepted 20 September 1995)
Several electrorheological (ER) materials systems composed of amorphous ceramic powders dispersed in light paraffin oil were developed to determine if relationships among ER activities, dielectric properties, compositions, porosities, and oxide species could be identified. The results of the studies suggested that trends among ER activity, dielectric phenomena, and alkali metal species existed. The aluminosilicate powders developed with various alkali metals showed that the ER activity increased as the activation energy decreased. The sodium aluminosilicate appeared to have the greatest ER activity and the lowest activation energy, while the cesium aluminosilicate displayed the weakest ER response, but had the highest activation energy. The thermodielectric responses of the different oxide materials systems developed with sodium showed that the mechanisms contributing to the dielectric dispersions had similar activation energies; however, the magnitudes of the recorded ER activities varied, and thus a direct correlation was not apparent. In addition, studies conducted with ER materials composed of sodium aluminosilicate powders of varying porosities showed that ER activities increased with increasing porosity. Furthermore, the analysis of the results of the thermodielectric and rheological studies of the different amorphous materials ER systems suggested that these materials may have an optimal stimulus frequency/temperature for ER activity.
I. INTRODUCTION
A unique class of polymeric solutions and ceramic suspensions whose rheological properties (i.e., flow and deformation responses to an applied stimulus) are modified when subjected to an electric field are referred to as electrorheological (ER) materials. In the automotive and aerospace industries, there is an interest to develop semiactive dynamic control systems incorporating ER materials; however, the acceptance of these materials for engineering systems was limited due to an inherent need for adsorbed water.1–3 The requirement for water for these materials to exhibit ER activity presented several significant drawbacks, including unstable and irreproducible properties, limitation in the functional temperature range, and the presence of high currents which caused resistance heating of the material leading to thermal runaway. These factors, along with the need to synthesize materials with reproducible ER material prop144
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