Reversible, voluminous and tunable patterning of multiwalled carbon nanotubes in ferrofluid: Partial or complete?

A new kind of hybrid fluids showing multiwalled carbon nanotubes (MWCNTs) coupled with magnetic nanoparticles have been synthesized and investigated for their structural, magnetic, and magneto-viscoelastic properties. The experimental results confirmed the cooperative coupling between MWCNTs and Fe₃O₄ nanoparticles forming the basis of magnetorheological mechanism which narrates the rheological properties. The molecular dynamics (MD) simulation and interaction calculations for particle-particle, particle-tube and tube-tube have been described and explained comprehensively in view of the interface properties of nanoparticles and nanotubes. The whole of the experimental and theoretical investigations confirms the bulk alignment of bent MWCNTs in ferrofluidic system which can be tuned with an applied magnetic field. The MD simulation predicts a weak and short-range molecular ordering mediated via free oleic acid molecules between MWCNTs and coated nanoparticles of ferrofluid. The interparticle interaction calculations (van der Waals, steric and magnetic energies) showed that the surface coated magnetic nanoparticles are kinetically stable in the fluid while the MWCNTs form chain-like aggregates. Moreover, by application of classical beam theory, a thermodynamic energy barrier comparison was made for the unbending of particle impregnated MWCNTs. Thus, considering the dimensional compatibility of nanotubes and nanoparticles, a field-induced partial alignment of MWNCTs by virtue of their bent form in ferrofluidic system is proposed. A partial or complete accomplishment of the reversibility and tunability of the patterning of MWCNTs on a large scale in ferrofluid has been investigated in detail.