Sintesis nanopartikel magnetik Fe3O4 (MNPs) tersalut poliakrilamida (PAM) dan termodifikasi asam oleat (OA) sebagai aplikasi enhanced oil recovery (EOR) = Novel synthesis magnetic nanoparticles Fe3O4 (MNPs) coated by polyacrylamide (PAM) and modified by oleic acid (OA) for enhanced oil recovery (EOR)