Thermal diffusivity measurements in fluids containing metallic nanoparticles using transient thermal lens

Thermal diffusivity measurements are carried out in nanofluids, solutions containing gold nanoparticles (similar to 10-40 nm size), using the mode-mismatched dual-beam thermal lens technique. An Ar+ laser is used as the heating source, and an intensity stabilized He-Ne laser serves as the probe beam. This technique provides a reliable photothermal alternative for measuring thermal diffusivities of nanofluids and semitransparent samples. The characteristic time constant of the transient thermal lens was obtained by fitting the experimental data to the theoretical expression for the transient thermal lens. From this characteristic time, the fluid thermal diffusivity, which increases when the particle sizes increase was obtained. The size of the nanoparticles was obtained from transmission electron microscopy (TEM) analysis.