Thermal Conductivity and Viscosity of Vegetable Oil–Based Cu, Zn, and Cu–Zn Hybrid Nanofluids

Abstract Sustainable manufacturing can be considered as one of the most important issues, which use the processes that play down negative environmental impacts in pursuing the bigger picture of sustainable development. An eco-friendly cutting fluid will go along with machining to achieve relative sustainability. To achieve relative sustainability level in machining, eco-friendly nanofluids are developed in this paper. Nanofluid is a stable colloidal suspension of ultrafine solid particles in a nanometric dimension dispersed in conventional and lubrication fluids. A two-step approach of synthesis of Zn, Cu, and Cu–Zn nanoparticles by mechanical alloying, followed by dispersing them in a base fluid (vegetable oil) to prepare nanofluids has been adopted. Powder particles were characterized by x-ray diffraction (XRD) and a particle-size analyzer. It is found from the XRD results that the crystallite size was around 26 nm for Cu powders, 59 nm for Zn powders, and 25 nm for Cu–Zn alloy after 60 h of milling. The particles size reduced to 60 nm for Zn, 60 nm for Cu, and 70 nm for Cu–Zn alloy after 60 h of milling. The enhanced thermal conductivity for Zn, Cu, and Cu–Zn nanofluids were 36 %, 42 %, and 48 %, respectively, with a volume concentration of 0.5 %, compared to base fluid (vegetable oil). The enhancement in viscosity for Zn, Cu, and Cu–Zn nanofluids are 47 %, 53 %, and 61 %, respectively, with a volume fraction of 0.5 % were reported.