Eco-Friendly Trinickel Disulfide Nanoparticles Advancing Poly-α-olefin Lubrication

Friction and wear remain formidable challenges for mechanical components in modern industrial applications. Traditional lubricants rely on a combination of additives that synergistically enhance performance but often undergo thermal degradation at increased temperatures, causing mechanical lubrication failure. Trinickel disulfide (Ni₃S₂) nanoparticles have emerged as promising candidates owing to their excellent tribological properties, chemical stability, and resilience at high temperatures. Compared with nonmagnetic nanoparticles, the magnetic properties of Ni₃S₂ nanoparticles can quickly form a protective film on the metal surface and reduce mechanical damage. Nevertheless, the conventional synthesis route of Ni₃S₂ requires high-temperature conditions and the release of toxic gases, resulting in environmental pollution. To address these limitations, we synthesized oleylamine-modified magnetic Ni₃S₂ nanoparticles (OA-Ni₃S₂ NPs) through a liquid-phase approach under mild conditions. Transmission electron microscopy (TEM) analysis indicated that OA-Ni₃S₂ NPs had an average particle size of ∼40 nm. Tribological evaluation in poly-α-olefin-6 (PAO6) base oil, conducted using a four-ball tribometer, revealed that OA-Ni₃S₂ NPs reduced the coefficient of friction (COF) by 31% and wear scar diameter (WSD) by 40% compared to pristine PAO6, underscoring their exceptional friction-reducing and antiwear performance, while mechanistic studies further clarified the sliding behavior of the nanoparticles at the friction interface. These findings underscore the potential of OA-Ni₃S₂ NPs as sustainable lubricant additives and provide a promising foundation for their deployment in high-temperature industrial systems.