Ultrasonic Investigation of Viscoelastic Properties in Silver Nanofluids

Silver nanofluids have been prepared by a one-step simple, green and cost-effective method using tannic acid as both reducing and stabilizing agent. The physical parameters such as ultrasonic velocity, density and viscosity of silver nanofluids were measured at (298.15 K, 303.15 K, 308.15 K and 313.15 K) and derived parameters like adiabatic compressibility (β), mean free path (Lmfp), bulk modulus (E), ultrasonic attenuation coefficient (α/f2), diffusion coefficient (D) and relaxation time (t) were computed. The variation of ultrasonic velocity with temperature, concentration and frequency shows anomalous behaviour and the parameters β, Lmfp, E too reflected this behaviour. Viscosity variation as a function of temperature and concentration is also studied and correlated with particle size. Ultrasonic attenuation coefficient (α/f2), diffusion coefficient and relaxation time exhibited a similar pattern as that of viscosity of samples confirming the significant role of viscosity in transport phenomena and flow characteristics of fluids. Results are interpreted in terms of nanoparticlenanoparticle and nanoparticle-fluid interactions.