关键词: electrorheological fluid, induced dipole, vacancies, high energy ball milling

Abstract: Traditional dielectric electrorheological fluid (ER) is based on the interaction of dielectric particle polarization, and the yield stress is low, which cannot meet the application requirements. The giant ER (GER) effect is caused by orientations and interactions of polar molecules adsorbed on the particle surfaces. Despite the high yield stress, these polar molecules are prone to wear and fall off, resulting in a continuous reduction in shear stress of GER liquid, which is also not suitable for application. Here we introduce a new type of ER fluid called induced dipole dominant ER fluid (ID-ER), of which the particles contain oxygen vacancies or conductor microclusters both prepared by high energy ball milling (HEBM) technique. In the electric field $E$, oxygen vacancies or conductor microclusters form induced dipoles. Because the local electric field $E_{\rm loc}$ in the gaps between particles can be two to three orders of magnitude larger than $E,$ the induced dipole moments must be large. The strong interactions of these induced dipoles make the yield stress of the ID-ER fluid reaching more than 100 kPa. Since there are oxygen vacancies or conductor microclusters everywhere in the particles, the particles will not lose the function due to surface wear during use. The experimental results show that the ID-ER fluid possesses the advantages of high shear stress, low current density, short response time, good temperature stability, long service life, and anti-settlement, etc. The comprehensive performance is much better than the existing ER materials, and also the preparation method is simple and easy to repeat, thus it should be a new generation of ER fluid suitable for practical applications.

Key words: electrorheological fluid, induced dipole, vacancies, high energy ball milling