Fluid Hyperthermia and Ultrasonic Studies on Nickel Ferrite Magnetic Nanoparticles

Abstract

Superparamagnetic nickel ferrite (NiFe2O4) nanoparticles were synthesized by low temperature hydrothermal method using EDTA as templating agent. The synthesized nanoparticles were characterized by FTIR, XRD, FESEM and TEM analysis. The XRD analysis shows the presence of cubic spinel phase with crystallite size of 26.42 nm. The morphology analyzed by FESEM and TEM techniques indicate the presence of cubical shape particles having average particle size of 28.44 nm with no agglomeration. The VSM analysis gives “S” shape curve with zero coercivity and saturation magnetization (Ms) of 30 emu/g indicating the presence of small magnetic particles exhibiting the superparamagnetic behaviour. Nickel ferrite nanofluids were prepared by mixing carrier fluid water with varying amounts of nickel ferrite nanopowder. Zeta potential measurements of dilute solution of nickel ferrite show the formation of stable nickel ferrite nanofluids. Hyperthermia and ultrasonic studies were carried out on various concentrations of nickel ferrite nanofluids. The SAR values and ultrasonic parameters were calculated. Less concentrated nickel ferrite nanofluids quickly attain threshold hyperthermia temperature of 43 °C when exposed to lower applied AC magnetic field of range 5 mT to 20 mT. Ultrasonic studies show at lower concentrations nickel nanoparticles interact with carrier fluid water through cohesive forces mainly hydrogen bonding and keep the particles in an isolated state there by continue to exhibit superparamagnetic characteristics. At higher concentrations, particle-particle interaction predominantly occurs leading to increase in particle size beyond 30 nm, so that the magnetic characteristics of nickel ferrite nanoparticles changes from superparamagnetic to ferromagnetic nature. At low concentrations induction heating occurs through Neel and Brownian relaxation mechanism whereas at high concentrations hysteresis loss mechanism operate to attain the threshold temperature of 43 ºC.