Effects of temperature and concentration of nanoparticles on rheological behavior of hexagonal boron nitride/coconut oil nanofluid

Abstract

In this work, a nano-lubricant composed of hexagonal boron nitride (hBN) nanoparticles suspended in pure coconut oil was developed using a two-step method that involved ultrasonic assistance. The synthesis was carried out at varying solid volume concentrations, ranging from 0.2% to 1.2%. X-ray diffraction and Transmission electron microscope techniques were utilized to conduct investigations into the structure and morphology of nanoparticles. These examinations reveal that the nanoparticles exhibit a hexagonal arrangement, with an average diameter measuring 40 nm. The viscosity of pure coconut oil/ hexagonal boron nitride (hBN) nanofluids was evaluated at temperatures ranging from 303 to 403 K. utilizing shear rates varying from 10 to 50 s−1. With the use of a rotational Anton Paar rheometer, the shear dynamic viscosity of the nanofluids was determined. The study focused on examining how the viscosity of pure coconut oil/ hexagonal boron nitride (hBN) nanofluids is influenced by variations in solid volume concentration and temperature. The results revealed that as the temperature increased, the viscosity of the nanofluids decreased. Conversely, when the quantity of nanoparticles was raised in the base fluid, the nanofluids demonstrated an increase in viscosity values. This study found that at a shear rate of 10 s−1, the nanofluid with a 1.0% solid volume concentration exhibits a viscosity 58% higher at 303 K compared to 403 K. Additionally, it was observed that when the concentration of nanoparticles increased from 0% to 1%, and the shear rate decreased from 50 to 10 s−1, the viscosity of the nanofluid increased by 32% at 303 K temperature. Furthermore, this study shows a significant impact of hexagonal boron nitride (hBN) nanoparticles in pure coconut oil as the prepared nanofluids with different nanoparticle concentrations demonstrated a relative viscosity higher than one.