Investigation of thermal properties of SiO2 and TiO2 composite nanofluids synthesized using sol-gel method for solar thermal applications

This study investigates the thermal properties of hybrid nanofluids composed of titanium dioxide (TiO2) and silicon dioxide (SiO2), synthesized via the sol-gel method at varying pH levels. The nanofluids, with concentrations between 0.1 and 0.5%, were prepared using a two-step process and characterized using a hydrometer, viscometer and rapid hot-wire technique. FTIR (Fourier transform infrared spectra) analysis confirmed the formation of Ti-O and Ti-O-Si bonds, enhancing TiO2's structural and thermal properties due to SiO2 incorporation. The results showed significant thermal conductivity improvements, even at low concentrations, with performance increasing as concentration rises. Notably, a maximum specific heat capacity of 4177.02 J kg-1 K-1 was achieved at a 0.1% volume concentration, while thermal conductivity reached 0.62 W m-1 K-1 at a 0.5% volume concentration. Overall, the TiO2-SiO2 nanofluids demonstrated exceptional thermal properties, particularly under high-solar-energy conditions, making them promising for efficient thermal management applications.