Thermal Diffusivity Dependence with Highly Concentrated Graphene Oxide/Water Nanofluids by Mode-Mismatched Dual-Beam Thermal Lens Technique

The thermal properties of graphene oxide (GO) nanoparticles’ colloidal suspensions prepared using the microwave-assisted hydrothermal method were determined. The mode-mismatched dual-beam thermal lens technique was employed to measure the thermal diffusivity of GO nanoparticles for different concentrations in the base fluid. By fitting the experimental data to the theoretical expression, the characteristic time constant was determined. The thermal diffusivity of the fluids seemed to be strongly dependent on the presence of the nanoparticles, increasing from 15.02 ± 0.16 × 10⁻⁴ cm²·s⁻¹ to 27.59 ± 0.51 × 10⁻⁴ cm²·s⁻¹ for concentrations ranging from 0.82 %V to 4.00 %V of GO/H₂O. As nanofluids concentration increased, a higher value of thermal diffusivity was obtained. The optical properties, morphology and chemical structure and functional groups of the nanoparticles were characterized by UV–Vis spectroscopy, transmission electron microscopy (TEM) and Fourier Transform infrared spectroscopy (FTIR). Two main absorption peaks at 230 nm and at 303 nm in the UV–Vis spectra were observed. TEM images revealed a uniform size distribution and spherical in shape NPs with mean diameter of 7.4 nm. This novel type of nanofluids have potential applications for heat transfer fluids like solar collectors and heat exchange systems.