High-Performance Magnetorheological Suspensions of Fe 3 O 4 -deposited Carbon Nanotubes with Enhanced Stability
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.109
High-Performance Magnetorheological Suspensions of Fe3O4-deposited Carbon Nanotubes with Enhanced Stability Hoyeon Kim1, Sehyun Kim2*, Yongsok Seo1* 1
RIAM, Department of Material Science and Engineering, Seoul National University, Kwanakro-1, Kwanakgu, Seoul 08826, Republic of Korea
2 Polymer Processing Technology Team, LG Chemical Ltd./Tech Center, Moonjidong 104-1, Yousungku, Daejon, 34114, Republic of Korea
*Corresponding Author: [email protected] (Y.S.), [email protected] (S.K)
Abstract The magnetorheological (MR) performance of suspensions based on the Fe 3O4-deposited carbon nanotubes (CNTs) was investigated by using a vibrating sample magnetometer (VSM) and a rotational rheometer. The Fe3O4-deposited CNTs were synthesized by the reduction process in which nano-Fe3O4 nanoparticles were generated and adsorbed on the surface of CNTs. All tested suspensions displayed excellent MR behaviors with high yield strengths. The morphology was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). It was revealed that Fe3O4 particles adsorbed on the surface of CNT particles led to make the surface topology bumpy and rough which decreased the particle sedimentation velocity. Finally, Turbiscan apparatus was used to test the sedimentation properties of Fe3O4-deposited CNTs suspensions. The suspensions showed excellent stability against sedimentation, much better than bare Fe3O4 particle suspension due to the inherent low density of CNT and its inside pore which can reduce the density mismatch between the nanoparticles and the carrier medium as well as the surface topology change due to the adsorption of Fe3O4.
INTRODUCTION Magnetorheological (MR) fluids which are suspensions of fine particles in a magnetically insulating fluid are kind of smart materials because they can form a solidlike structure of fibril shapes along the magnetic field direction upon application of a
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magnetic field [1]. When the magnetic field is applied, randomly dispersed particles can rapidly form fibril shapes (meso-structure) along the field direction due to polarization between the suspended particles. Reverse structural transition happens once the applied field is removed. The structural changes occur very quickly, on the order of milliseconds [2]. The meso-structure formed in response to a magnetic field enable the apparent viscosities of the MR fluids to be increased by 3 to 4 orders of magnitude. The properties of magnetorheological (MR) fluids can be controlled over a wide range by varying the magnetic field intensity. The field-responsive properties of MR fluids are quite useful for a variety of mechanical systems. In the automotive industry, for example, the variable properties of MR f
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