Dual-Surface Engineering of Fe3O4 Magnetic Nanoparticles: Enhanced Magnetorheological Performance and Tribological Mechanisms

Magnetic fluids are smart materials that fall under the category of magnetic materials and possess the property of fluidity. Nevertheless, conventional modifications using a monolayer surfactant are limited due to poor thermal stability and insufficient nanoparticle-carrier fluid compatibility. The synthesis of Fe3O4 nanoparticles via co-precipitation, is followed by a unique bilayer surface coating of oleic acid and boron-modified high molecular weight succinimide. The nanoparticles' characterization result indicates that as the nanoparticles were modified their diameter decreased from 13.66 nm to 11.39 nm. Their structure remained as cubic spinel structure with saturation magnetization of 61.48 emu/g. Analysis of FT-IR spectra confirmed that OA is anchored to the surface of the particles through the formation of Fe-OOC-R bonds. Hence, BSI will form a stable interfacial layer in this case. Rheological studies have shown a strong magnetoviscous effect in the magnetic field of 200 kA/m at 263 K which was suppressed when the temperature was raised to 313 K. According to tribological tests, the use of 4.5 wt% tungsten dialkyldithiocarbamate (WTDC) reduced friction, as the lowest CoF is indicated to occur at a value of N Load = 35 N at 6 Hz. Consequently, the technique presented herein will be used to create high-performance magnetic fluids for applications such as aerospace sealing and MEMS lubrication.