Tribological and Thermal Transport of Ag-Vegetable Nanofluids Prepared by Laser Ablation

Lubricants and fluids are critical for metal-mechanic manufacturing operations as they reduce the friction and wear of tooling and components, and serve as coolants to dissipate the heat generated in these operations. The proper application of these materials improves machine operative life and tooling, and decreases cost, energy, and time consumption for maintenance, damage, repairs, or the need to exchange pieces/components within the machinery. Natural or vegetable-based lubricants have emerged as a substitute for mineral oils, which harm the environment due to their low biodegradability and have negative effects on human health (e.g., causing skin/respiratory diseases). Thus, finding biocompatible and efficient lubricants has become a technology objective for researchers and industry. This study evaluates soybean-, corn-, and sunflower-based lubricants reinforced with silver (Ag) nanostructures by a pulsed laser ablation process. Thermal and tribological evaluations were performed with varying Ag contents, and temperature-dependent behavior was observed. Thermal conductivity improvements were observed for all nanofluids as the temperature and Ag concentration increased (between 15% and 24%). A maximum improvement of 24% at 50 °C and 10 min exposure time of the pulsed laser ablation process for soybean oil was observed. The tribological evaluations showed improvements in the load-carrying capacity of the vegetable oils, i.e., an increase from 6% to 24% compared to conventional materials. The coefficient of friction performance also showed enhancements with Ag concentrations between 4% and 15%.