OBRABOTKAMETALLOV technology Vol. 27 No. 1 2025 of sedimentation or agglomeration phenomena. Different nanopowders such as CuO, Al2O3, graphene, and multi-walled carbon nanotubes were evaluated across different nanofluids. Among these, graphene nanofluids exhibited the most promising thermal conductivity performance. Compared to corn oil’s thermal conductivity of 0.154 W/mK, graphene oil with a 0.8 % nanoparticle concentration demonstrated an improvement of 9.74 %, reaching 0.169 W/mK. Remarkable fact is that graphene nanofluids exhibited the most promising thermal conductivity performance. In particular, graphene nanofluids consistently outperformed other types, with multi-walled carbon nanotubes following closely, next by copper oxide and aluminum oxide. These findings underscore the remarkable potential of graphene-based nanofluids in enhancing thermal conductivity compared to conventional base fluids. Graphene’s exceptional thermal conductivity is attributed to its unique atomic structure. Graphene consists of a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice, enabling efficient heat transfer due to its high phonon mean free path and ballistic transport of heat carriers. Furthermore, graphene exhibits superior mechanical strength and stability, preventing structural deformations that could impede heat transfer. Its immense surface area allows for easier interaction with neighboring molecules, enhancing heat transfer efficiency. Fig. 6 illustrates the change in viscosity of different nanofluids with the incorporation of different nanoparticles. Across all nanofluids, there is a noticeable increase in viscosity of up to 0.8 % upon the addition of nanoparticles. However, once the nanoparticle concentration reaches 1 %, a decrease in viscosity occurs due to sedimentation or agglomeration phenomena. Various nanopowders, including CuO, Al2O3, graphene, and multi-walled carbon nanotubes, underwent evaluation in different nanofluid formulations. Graphene nanofluids demonstrated the most favorable viscosity performance. In comparison to corn oil’s viscosity of 61 cP, the viscosity of graphene oil with a 0.8 % nanoparticle concentration saw a notable increase of 21.3 %, reaching 74 cP. Remarkably, graphene nanofluids consistently surpassed other types in terms of viscosity enhancement. These results highlight the potential of graphene-based nanofluids in improving viscosity characteristics compared to conventional base fluids because graphene’s inherent robustness minimizes structural deformations within the fluid, thus contributing to enhanced viscosity. High cutting forces lead to rapid tool wear, shortening tool lifespan and increasing the frequency of tool changes, and result in poor surface finish due to vibration and chatter during machining. Various nanopowders, such as CuO, Al2O3, graphene, and multi-walled carbon nanotubes, were evaluated in Fig. 6. Viscosity of different nanofluids
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