Synergistic Effects of Nonmagnetic Carbon Nanotubes on the Performance and Stability of Magnetorheological Fluids Containing Carbon Nanotube-Co_0.4Fe_0.4Ni_0.2 Nanocomposite Particles

Abstract

We investigated the magnetorheological (MR) properties of the carbon nanotube (CNT)-Co 0.4 Fe 0.4 Ni 0.2 composite suspension to find a high-performance MR fluid with excellent stability. The composites were fabricated by chemical reduction of Co 0.4 Fe 0.4 Ni 0.2 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 0.4 Fe 0.4 Ni 0.2 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 3 O 4 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 0.4 Fe 0.4 Ni 0.2 nanocomposite MR suspension. The low density of the CNTs resulted in much better long-term stability for the CNT-Co 0.4 Fe 0.4 Ni 0.2 nanocomposite suspension than the MR fluid containing only Co 0.4 Fe 0.4 Ni 0.2 .

Non‐Settling Super‐Strong Magnetorheological Fluids

“…The frequency sweep results in Figure 5b show that the storage modulus is greater than the loss modulus by more than three orders of magnitude, indicating the dominance of the solidlike properties. [21][22][23][24] This behavior confirms again that the solidlike elastic properties imparted by the chain-like structures overwhelm the liquid-like viscous properties and that the mesostructures are strong enough not to be disturbed by external stresses at all over the entire angular frequency range. The storage modulus decreased with the addition of silicone oil.…”

“…[ 42,43 ] Under a fixed particle concentration, the master curve for the specific viscosity (i.e., the ratio of the apparent viscosity and the medium viscosity) and the volume fraction correction versus $$\dot{\gamma }$$/ μ 2 at different magnetic field strengths can be obtained. [ 22–24 ] The behaviors of different MR fluids are compared for pure CI, 95% CI, and 90% CI fluids at two different magnetic field strengths, as shown in Figure 6b. All six curves overlap well with each other, which means the behaviors of the three fluids were the same because they followed the same scaling law ( Figure a) and therefore the same particle magnetization model.…”

“…All six curves overlap well with each other, which means the behaviors of the three fluids were the same because they followed the same scaling law ( Figure a) and therefore the same particle magnetization model. [ 22–24 ] A negligible difference observed at high shear rates and weaker magnetic fields is ascribable to the relatively weaker magnetic polarization force of the 90% CI particles as a result of the inclusion of the magnetically inactive silicone oil. [ 4,5 ]…”

“…As a solution to this problem, researchers have attempted to fabricate magnetic composites by combining magnetic particles with low‐density materials. [ 17–38 ] However, the use of composite particles to reduce the density mismatch inevitably degrades the MR performance of composite particle‐based fluids because non‐magnetic materials are added. [ 1,2 ] As an alternative, researchers have tried to solve the sedimentation problem by using surfactants.…”

Molecular Dynamics Simulations and Experimental Studies of the Microstructure and Mechanical Properties of a Silicone Oil/Functionalized Ionic Liquid-Based Magnetorheological Fluid

“…As clearly observed in the storage modulus curves (Figure 10c), G′ was independent of shear strain under the external magnetic field (0.12−0.55 T) at the low strain amplitude stage (0.005−1.0%), and the strain amplitude range is termed the linear viscoelastic (LVE) region. 52,70 In the LVE region, G′ was higher than G″ at the same magnetic field strength. It can be speculated that the formation of a chainlike structure under the magnetic field results in the MR fluid exhibiting solid-like properties, and thereby, it has obvious LVE behavior.…”