Synthesis of ternary MWCNT/Fe3O4/Ag hybrid nanocomposites and nanofluid stability evaluation: Role of MWCNT surface modification

Ternary hybrid nanofluids have attracted significant attention for advanced thermal management applications due to their ability to combine complementary properties of multiple nanomaterials. However, their practical performance is often limited by insufficient dispersion stability, particularly in multi-component systems. In this study, ternary MWCNT/Fe₃O₄/Ag nanocomposites were synthesized using both functionalized and non-functionalized multi-walled carbon nanotubes (MWCNTs) to investigate the influence of surface chemistry on nanofluid stability. The dispersion stability of the nanofluids was evaluated over a 30-day period using UV–Vis spectroscopy and zeta potential measurements. All samples exhibited high electrostatic stability, with ζ-potential values ranging from −50 to −70 mV. Notably, nanofluids prepared with non-functionalized MWCNTs showed more negative ζ-potential values (≈ −70 mV) compared to functionalized systems (≈ −50 to −55 mV) and maintained nearly constant absorbance throughout the aging period, whereas functionalized systems exhibited a gradual decline due to aggregation. These results demonstrate that surface functionalization does not necessarily improve long-term stability and that stronger surfactant adsorption on pristine MWCNT surfaces leads to enhanced electrostatic stabilization. Importantly, improved dispersion stability prevents nanoparticle aggregation and sedimentation, which are known to disrupt conductive pathways and degrade thermal performance over time. Therefore, the identified stable nanofluid formulations provide a more reliable basis for sustaining consistent thermal conductivity and heat transfer efficiency in practical thermal management systems. • Ternary MWCNT/Fe₃O₄/Ag nanocomposites were successfully synthesized. • MWCNT surface chemistry strongly influences nanofluid dispersion stability. • Non-functionalized MWCNT nanofluids showed superior long-term stability. • Strong SDS adsorption enhanced electrostatic stabilization (ζ ≈ −70 mV). • Stability governed by surfactant–particle and MWCNT surface interactions.