Thermal and rheological formulation of novel Hardystonite and Åkermanite hybrid nanofluids dispersed in biocompatible olive oil/silica base fluid
摘要
A systematic experimental study was conducted on a non-aqueous, biocompatible hybrid bioceramic nanofluid comprising Hardystonite and Åkermanite dispersed in a silica/olive-oil carrier, in which silica acted as a non-ionic stabilizer and thermal enhancer. Thermal conductivity and rheology were measured directly over 20–40 °C and 0.5–2.0 mass% total solids, with shear rates of 13–130 s−1. Thermal conductivity increased with both temperature and loading, with super-linear gains for the hybrid systems. At 40 °C and 2.0 mass%, k reached 0.441 W m−1 K−1 for silica/olive-oil, 0.551 W m−1 K−1 for Åkermanite–silica, and 0.592 W m−1 K−1 for Hardystonite–silica. Relative to the base fluid, thermal-conductivity enhancement (TCE) at 1.0 mass% ranged 13.3–14.5% (silica), 21.8–22.9% (Åkermanite hybrid), and 27.1–28.0% (Hardystonite hybrid); at 2.0 mass% these increased to 22.4–24.1%, 35.3–37.1%, and 42.7–44.6%, respectively. All formulations exhibited pseudoplastic behavior. At 20 °C and 13 s−1, viscosity rose from 85 mPa s (olive oil) to 403.8 mPa s (silica, 0.5 mass%) and 3230 mPa s (silica, 2.0 mass%); corresponding 2.0 mass% hybrids reached 14,858 mPa s (Hardystonite) and 21,802.5 mPa s (Åkermanite), decreasing at 40 °C to 6992 and 10,640 mPa s, respectively. FESEM revealed silica-dominated spherical hybrid particles (~ 30–55 nm), consistent with improved dispersion and stability. Overall, the Hardystonite–silica formulation delivered the highest thermal enhancement, whereas the Åkermanite–silica formulation produced the strongest viscosity increase, enabling tunable trade-offs between heat transport and flow resistance for applications in biomedical heat management, hyperthermia, and targeted delivery.