Synergistic Effects of Nonmagnetic Carbon Nanotubes on the Performance and Stability of Magnetorheological Fluids Containing Carbon Nanotube-Co<sub>0.4</sub>Fe<sub>0.4</sub>Ni<sub>0.2</sub> Nanocomposite Particles.

Choi, Junsok; Nam, Ki Tae; Kim, Sehyun; Seo, Yongsok · Nano Lett · 2021

basic_science · Level V

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Abstract

We investigated the magnetorheological (MR) properties of the carbon nanotube (CNT)-Co<sub>0.4</sub>Fe<sub>0.4</sub>Ni<sub>0.2</sub> composite suspension to find a high-performance MR fluid with excellent stability. The composites were fabricated by chemical reduction of Co<sub>0.4</sub>Fe<sub>0.4</sub>Ni<sub>0.2</sub> on the surface of amine-functionalized CNTs. A synergistic effect between the high aspect ratio of the CNTs and the strong magnetic polarization of the Co<sub>0.4</sub>Fe<sub>0.4</sub>Ni<sub>0.2</sub> led to stronger MR performance of the nanocomposite particle suspension. The MR fluid exhibits an unexpected high yield stress value that is 13 times greater than that of a CNT-Fe<sub>3</sub>O<sub>4</sub> suspension at a magnetic field strength of 343 kA/m. Nonmagnetic CNTs form a three-dimensional networklike structure, imparting surprisingly large additional yield stress to the CNT-Co<sub>0.4</sub>Fe<sub>0.4</sub>Ni<sub>0.2</sub> nanocomposite MR suspension. The low density of the CNTs resulted in much better long-term stability for the CNT-Co<sub>0.4</sub>Fe<sub>0.4</sub>Ni<sub>0.2</sub> nanocomposite suspension than the MR fluid containing only Co<sub>0.4</sub>Fe<sub>0.4</sub>Ni<sub>0.2</sub>.