TEODORA MALAERU, EROS ALEXANDRU PATROI, VIRGIL MARINESCU, OVIDIU OPREA, DELIA PATROI, CRISTIAN MORARI, EUGEN MANTA, GABRIELA GEORGESCU PREPARATION AND CHARACTERIZATION OF FE3O4 MAGNETIC NANOFLUID IN VEGETABLE OIL This paper reports the synthesis of Fe3O4 nanoparticles with a hydrophobic surface functionalized with oleic acid through a simple and efficient route in air atmosphere and by co-precipitation. The hydrophobic surfactant agent was added in the magnetic crystal growth stage. Magnetic nanofluid was obtained by ultrasonic dispersion of magnetic nanoparticles in a carrier liquid – vegetable oil. The sample as powder has been characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), and Vibrating Sample Magnetometry (VSM) at room temperature. The magnetic nanofluid in vegetal oil was investigated by determining the stability of the nanoparticles in the vegetable oil through UV-Vis spectrometry method, the magnetic properties through Vibrating Sample Magnetometry (VSM) method at room temperature, and thermal conductivity as function of magnetic nanoparticles volume concentration and of temperature.