A novel nanoparticle-enhanced magnetic fluid for low-temperature sealing application

The large starting torque of magnetic fluid seals at low temperatures is a key challenge hindering their application in low-temperature environments. Numerous studies have shown that there is an inherent contradiction between reducing starting torque and maintaining pressure resistance, making it difficult to achieve both simultaneously. In this study, a detachable magnetic fluid sealing device and a sealing testing bench were designed to measure the pressure resistance and starting torque of the magnetic fluid seal at low temperatures. We found that as the temperature decreased, the starting torque increased exponentially. Further experiments revealed that adding hydrophilic silica nanoparticles to the magnetic fluid significantly reduced the starting torque of the sealing device. Molecular dynamics simulations indicated that the formation of large-scale, field-induced structures in the magnetic fluid at low temperature is the key reason for the increase in starting torque. The silica nanoparticles can hinder the formation of these structures, thereby reducing the starting torque without significantly affecting the pressure resistance of the sealing device. Our research is of great significance for solving the low-temperature sealing problem in high-end equipment.