Surfactant additive enhanced stability and thermal conductivity of graphene (Gr) and ALN (AlN) nanolubricants

Abstract

The stability of the nanoparticles is a vital concern in nanolubricants research, where poor dispersion stability has a negative impact on their heat transmission and tribological performance. Adding surfactants is a useful and effective way to change the surface properties of nanoparticles and lower the surface tension of base fluids. This makes nanoparticles more stable and easier to disperse in base fluids. Hence, this paper aims to study the compability of surfactant in terms of stability and thermal conductivity performance played by Graphene (Gr) and Aluminium Nitride (AlN) nanoparticles in the composition of 4GS Suniso compressor oil (CO) and Petronas 15W-40 engine oil (EO) nanolubricants. Additionally, the performance of the nanolubricants and the compatibility of the nanoparticles with surfactant in various base fluids were examined in this study providing insights into their suitability for enhancing the thermophysical properties of different base fluids. Furthermore, the majority of research have examined the same kind of nanoparticles; however, in this study, Gr and AlN, which are carbon- and ceramic-based nanoparticles, respectively, belong to two distinct classes of nanoparticles. Cetyltrimethylammonium bromide (CTAB), Sodium dodecylbenzene sulfonate (SDBS), and Sorbitan Monooleate (SPAN-80) are the surfactants employed in this study. Each of these surfactants has a different type; CTAB is cationic, SDBS is anionic, and SPAN-80 is a non-ionic surfactant. Hence, this study investigates the effect of surfactant type (cationic, anionic, and non-ionic) on the thermal conductivity performance of Gr and AlN-based nanolubricants in both compressor oil and engine oil, highlighting the role of surfactant-nanoparticle interactions in improving nanolubricant performance. Visual observation, thermal conductivity measurement, pH value measurement, Zeta Potential analyzer and viscosity measurement are used for the identification of compatibility surfactant for Gr and AlN in both base oils. The study revealed that SPAN-80 and CTAB are the most suitable for AlN and Gr, respectively, in both of CO and EO.