Effects of rare earth doped on thermal conductivity of ZnO-water nanofluid by ultrasonic velocity measurements

Abstract

In the current work, pure zinc oxide (ZnO), cerium (Ce) doped ZnO, lanthanum (La) doped ZnO and cerium-lanthanum (Ce-La) doped ZnO nanoparticles (NPs) have been synthesized by the wet chemical method. The prepared samples have been dispersed into water and mixed thoroughly by the way of ultrasonication process to acquire nanofluid samples. The change of ultrasound velocity in aqueous solution was investigated as a function of particle size and suspension density. The thermal conductivity and acoustical parameters such as adiabatic compressibility, intermolecular free length and acoustic impedance have been evaluated from the experimental data. Also, the thermal conductivities of nanofluids have been calculated through ultrasonic method and the results were compared experimentally with the flash laser technique method. The thermal conductivities decrease with doping according to the rare earth atomic mass and ionic radius.