VP1-11 Rheological properties of magnetorheological fluids using magnetic spherical nickel particles with different surface roughness
Creators: George Stoian
Georgiana Balusescu
Marian Grigoras
Horia Chiriac and Nicoleta Lupu
Publisher: name: IEEE
Year: 2025

Magnetorheological fluids (MRFs) are fluids suspension composed by micron magnetic particles dispersed in non-magnetic carrier fluid [1]. These intelligent materials respond to applied magnetic fields by changing the rheological behaviour, developing a yield stress that increases with the applied magnetic field [2]. MRFs are visible in a variety of applications in science and engineering [3]. The rheological properties of MRFs are determined by concentration of magnetic particles, their size, shape and magnetic properties [4]. This study investigates the influence of the surface characteristics of the magnetic nickel particles on the performances of MR fluids. Micrometric Ni powders, with spherical and similar size particles, with different surface roughness (smooth-MRF1 vs. high surface roughness-MRF2) were used for the preparation of the MRFs. Engine oil was used as carrier fluid for the dispersed phase. The particles were characterized by SEM and VSM, while the magnetorheological properties have been studied using a magneto-rheometer. Ni particles (Fig.1) have similar sizes, same saturation magnetization and soft magnetic properties but they differ on the surface. The share stress vs. share rate curves were plotted with the magnetic field as a parameter. From these flow curves the yield stress corresponding to different values of the magnetic field were calculated according to the Bingham model. Fig. 2 shows that MRF1 based on smooth surface particles exhibits much higher yield stresses. To explain this behaviour, we performed oscillation tests to investigate the internal structure of MRFs. Although the surface roughness is expected to increase the friction forces between particles and create stronger particle chains, it seems that the roughness of the particles negatively impacts the formation of the chains. In conclusion, the surface has a significant influence on the performance of MRFs. A higher roughness negatively impacts the flow behaviour in magnetic field. Acknowledgements. Financial support from NUCLEU Programme - Contract No. 18N/01.01.2023, project PN 23 11 01 01 is highly acknowledged.References: 1. Sun, Y., Wang, Y., Deng, H., Sang, M., Gong, X., (2022), Effect of MXene nanosheets attached to carbonyl iron microspheres on the performance and stability of magnetorheological fluid, Journal of Industrial and Engineering Chemistry, 114, 508–517. 2. Zhang, L., Luo, Y., Ren, H., Wang, Y., Gu, Z., (2023), Microscopic modeling of magnetorheological fluids containing spherical and ellipsoidal ferromagnetic particles, Journal of Magnetism and Magnetic Materials, 586, 171204. 3. Ashtiani, M., Hashemabadi, S.H., Ghaffari, A., (2015), A review on the magnetorheological fluid preparation and stabilization, Journal of Magnetism and Magnetic Materials, 374, 716–730. 4. Kariganaur, A.K., Kumar, H., Arun, M., (2022), Effect of temperature on sedimentation stability and flow characteristics of magnetorheological fluids with damper as the performance analyser, Journal of Magnetism and Magnetic Materials, 555, 169342.
Magnetorheological fluids (MRFs) are fluids suspension composed by micron magnetic particles dispersed in non-magnetic carrier fluid [1]. These intelligent materials respond to applied magnetic fields by changing the rheological behaviour, developing a yield stress that increases with the applied magnetic field [2]. MRFs are visible in a variety of applications in science and engineering [3]. The rheological properties of MRFs are determined by concentration of magnetic particles, their size, shape and magnetic properties [4]. This study investigates the influence of the surface characteristics of the magnetic nickel particles on the performances of MR fluids. Micrometric Ni powders, with spherical and similar size particles, with different surface roughness (smooth-MRF1 vs. high surface roughness-MRF2) were used for the preparation of the MRFs. Engine oil was used as carrier fluid for the dispersed phase. The particles were characterized by SEM and VSM, while the magnetorheological properties have been studied using a magneto-rheometer. Ni particles (Fig.1) have similar sizes, same saturation magnetization and soft magnetic properties but they differ on the surface. The share stress vs. share rate curves were plotted with the magnetic field as a parameter. From these flow curves the yield stress corresponding to different values of the magnetic field were calculated according to the Bingham model. Fig. 2 shows that MRF1 based on smooth surface particles exhibits much higher yield stresses. To explain this behaviour, we performed oscillation tests to investigate the internal structure of MRFs. Although the surface roughness is expected to increase the friction forces between particles and create stronger particle chains, it seems that the roughness of the particles negatively impacts the formation of the chains. In conclusion, the surface has a significant influence on the performance of MRFs. A higher roughness negatively impacts the flow behaviour in magnetic field. Acknowledgements. Financial support from NUCLEU Programme - Contract No. 18N/01.01.2023, project PN 23 11 01 01 is highly acknowledged.References: 1. Sun, Y., Wang, Y., Deng, H., Sang, M., Gong, X., (2022), Effect of MXene nanosheets attached to carbonyl iron microspheres on the performance and stability of magnetorheological fluid, Journal of Industrial and Engineering Chemistry, 114, 508–517. 2. Zhang, L., Luo, Y., Ren, H., Wang, Y., Gu, Z., (2023), Microscopic modeling of magnetorheological fluids containing spherical and ellipsoidal ferromagnetic particles, Journal of Magnetism and Magnetic Materials, 586, 171204. 3. Ashtiani, M., Hashemabadi, S.H., Ghaffari, A., (2015), A review on the magnetorheological fluid preparation and stabilization, Journal of Magnetism and Magnetic Materials, 374, 716–730. 4. Kariganaur, A.K., Kumar, H., Arun, M., (2022), Effect of temperature on sedimentation stability and flow characteristics of magnetorheological fluids with damper as the performance analyser, Journal of Magnetism and Magnetic Materials, 555, 169342.