Stable silicone oil based ferrofluids with well low-temperature fluidity applied to magnetic fluid seal

Stable silicone oil based ferrofluids with high magnetization and low-temperature fluidity have been successfully synthesized. The ferrofluids containing surfactant coated magnetite nano particles with average diameters of 10 nm could maintain stable for more than 2 months. Silicone oil based ferrofluids could reach a saturated magnetization of 24.6 emu/g, which ensures them to be easily controlled by the magnetic fields. Silicone oil based ferrofluids could maintain their fluidity at −40 °C while the LAN15 (engine oil) based ferrofluids could not. The property of low- temperature fluidity is systematically explained by the magneto-rheological experiments. This outstanding property of low-temperature fluidity ensures the silicone oil based ferrofluids a promising candidate material for applications in magnetic fluid seal. Herein, the magnetic rotary sealing performed by different ferrofluids at low temperature are systematically characterized. As result, the silicone oil based ferrofluids have lower starting torque and higher sealing pressure endurance compared to LAN15 based ferrofluids at −40 °C. Based on our experimental results, the theoretical analysis and numerical simulation results systematically explained the advantages silicone oil based ferrofluids have on low-temperature magnetic fluid seal.