Enhancing stability and rheological behavior of nanolubricants for hermetic compressor bearings

• Published in: Journal of molecular liquids 2024-12, Vol.416, p.126501, Article 126501
• Main Authors: Canever, Sílvia Betta, Martins, Mateus Melo, Evangelista, Leandro Lima, Binder, Cristiano, Hotza, Dachamir
• Format: Article
• Language: English
• Subjects: Alumina; Hermetic compressor bearings; Nanolubricants; Rheological behavior; Stability
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2024.126501

[Display omitted] •Nanolubricants containing surface-modified alumina remained stable longer.•The viscosity of the pure oil and nanolubricants decreased with increasing temperature.•The plate-plate configuration is not suitable for rheological analysis of fluids with low viscosity at high temperatures.•Nanoadditives present potential alternatives to additives in oils used in compressor bearings. The use of nanoparticles as nanoadditives in lubricating oils for hermetic compressor bearings presents a potential alternative to conventional additives. Alumina nanoparticles stand out as a promising candidate because they significantly improve lubrication by filling surface asperities, reducing friction and wear. Additionally, their large-scale production and lower cost, coupled with their environmentally friendly nature, make them an attractive option. However, the rheological behavior and stability of the lubricants must be evaluated, as nanoparticles can agglomerate and sediment. In this work, nanolubricants containing 0.5 and 1 vol% of pure alumina (A) and surface-modified alumina (AS) were prepared using a two-step method. Visual inspection and accelerated stability tests were conducted to evaluate the stability of the nanofluids. Rheological behavior was examined at temperatures of 25, 50, and 75 °C across shear rates up to 70,000 s−1, pertinent to hermetic compressor bearing applications. The results demonstrated that AS nanolubricants remained stable for an additional 1–2 weeks compared to A nanolubricants, which can be attributed to the chemical affinities of oleic acid with the oil. At 25 and 50 °C, both pure oil and AS nanolubricants exhibited Newtonian behavior, while A nanolubricants displayed slight pseudoplasticity, as confirmed by the Power Law model. At 75 °C, all lubricants exhibited thixotropic behavior.