Abstract In this study, the effects of CoFe 2 O 4 (as hard magnetic) nanoparticle addition and MnFe 2 O 4 (as soft magnetic) nanoparticle addition in carbonyl iron powder-based magnetorheological fluid were investigated. Both types of nanoparticles (CoFe 2 O 4 and MnFe 2 O 4 ) were analyzed for grain morphology shape using field emission scanning electron microscopy (FESEM) and magnetic properties using a vibrating sample magnetometer (VSM). FESEM and VSM analysis revealed that CoFe 2 O 4 nanoparticles exhibit smaller grain size than MnFe 2 O 4 , while the coercivity and remanence of CoFe 2 O 4 nanoparticles are higher than MnFe 2 O 4 . Three types of MRF samples were made (CIP MRF without nanoparticles, CIP MRF with CoFe 2 O 4 nanoparticles and CIP MRF with MnFe 2 O 4 nanoparticles). The concentration of nanoparticles addition was selected as 1wt%, while the concentration of dispersed particles was kept at 70wt%. The results showed that the addition of both types of nanoparticles to MRF to the MRF increase the shear stress and storage modulus. However, the addition of both types of nanoparticles has a negative effect during the sudden removal of magnetic field test. In sudden removal magnetic fields, the presence of nanoparticles in MRF causes the shear stress value of MRF to be higher and the value is not stable.
Nugroho et al. (Thu,) studied this question.