Lipophilic magnetite nanoparticles coated with stearic acid: A potential agent for friction and wear reduction

Lipophilic magnetite nanoparticles (MagNP; d≈10 nm) functionalized with stearic acid were synthetized and tested as additive in polyalphaolefin synthetic base oil (PAO8) in a model system. The thermal properties of the starting base oil and of the base oil mixed with nanoparticles were evaluated using TG/DTA under inert and oxidizing atmosphere. The frictional response of the lubricants was evaluated under a broad range of operating conditions at the boundary lubrication regime using a 10 mm AISI 52,100 bearing steel ball against the flat face of an AISI H13 steel disc. The results showed that: i) MagNP improved the thermal stability of the base oil; ii) reduced the friction values, mostly during load step transition; iii) reduced significantly the wear marks.