Rheological and magnetic properties of stable poly alpha olefins based ferrofluids with high viscosity and magnetization

Abstract

Poly alpha olefins (PAO) based ferrofluids (FFs) have been synthesized containing novel double-layer surfactants stabilized 10 nm diameter magnetite nano powders, which could maintain stable in PAO-4 and PAO-10 base liquids for more than 2 months. The PAO based FFs prepared in this study could reach a viscosity of 3000 mPa·s at the room temperature and a powder ratio of over 30 %wt. The viscosity performance of FFs under diverse magnetic fields and temperatures are characterized systematically. The smooth variation curves of viscosity under diverse shear rates indicate that the FFs maintains stable under the shear stress in our study. Yield stress for PAO-4 and PAO-10 based FFs are obtained as values of 3.7 Pa and 1.5 Pa, respectively. PAO based ferrofluids exhibit high viscosity, high saturated magnetization, steady performance of viscosity with the variation of magnetic fields and moderate yield stress, ensuring the PAO based FFs a promising candidate material for magnetic rotary sealing and lubrication uses.