Enhanced rheological properties of dilute suspensions of magnetic nanoparticles in a concentrated amphiphilic surfactant solution

Abstract

We present an experimental study of the magnetorheological response of dilute suspensions of magnetic nanoparticles in concentrated amphiphilic surfactant solutions. Low particle content (<0.4% v/v) induced significant increase in viscosity, enhancing the shear thinning behavior observed in the absence of the nanoparticles. A magnetic field induced yield stress of up to 10 Pa at magnetic fields of up to 0.4 T was also observed. Experiments under small amplitude oscillatory shear indicate a transition from viscous to elastic behavior at a critical magnetic field which depends on the frequency of the oscillatory shear. At low applied magnetic fields loss and storage moduli are independent of the magnetic field and increase with the frequency of the oscillatory shear. At high applied magnetic fields both the loss and storage moduli seem to asymptote to a power law dependence on the magnetic field magnitude. These results illustrate the possibility of inducing dramatic changes in the rheological properties of complex fluids by addition of minute amounts of magnetic nanoparticles and application of magnetic fields.

Self-assembly and rheology of dipolar colloids in simple shear studied using multi-particle collision dynamics

“…However, the collapse can be achieved with ad- λ Fig. 15 The experimental viscometric curves reported in the literature sources summarized in Table 1, plotted in the coordinates of reduced shear rate (Mason number Mn) and intrinsic viscosity [η]. The color code corresponds to the estimated dipole interaction parameter λ .…”

“…b University of Latvia, Raina bulvaris 19, LV-1586 Riga, Latvia. E-mail: dmitrijs.zablockis@lu.lv terials with customized physical properties [13][14][15] also exhibiting viscoelastic behavior 16,17 . The new generation of magnetic colloids based on nanoparticles with accurately tailored size and/or oxide-free magnetic materials feature greatly enhanced interaction strength [18][19][20][21][22] .…”

“…Symbols correspond to simulations, dashed lines are intended to guide the eye. The solid line corresponds to the theoretical prediction of the chain model(10) and(15). The left inset shows a detailed view of the initial region.…”

Soft magnetic nanocomposites based on adaptive matrix of wormlike surfactant micelles

“…Usually, in MRFs, the aggregation of magnetized particles is observed already at rather small concentrations of particles: 0.1-5 vol%. 5,[13][14][15] However, these uids suffer from some drawbacks. One of them is the nonlinear rheological response, which comes out with increasing strain amplitude.…”

Sistemas de nanopartículas magnéticas: estudos experimentais e simulações Monte Carlo

“…Como em um ferrofluido as partículas magnéticas estão dispersas em líquido comum, como água e óleo, esperamos que todas as propriedades magnéticas que aparecem devido à aplicação de um campo magnético são devido a presença e interações destas partículas, o que faz com que a concentração seja um fator importante para observar o efeito magnetoviscoso. No entanto isto não é mais verdadeiro quando as partículas magnéticas estão diluídas em um meio que pode ser afetado pela sua presença e sua interação com o campo magnético, como soluções anfifílicas de surfactantes [70], ferronemáticos [14,60] e cristais líquidos. Estas interações dinâmicas das partículas magnéticas com o meio e com o campo aplicado levam à diferentes propriedades físicas na presença do campo aplicado, como mudanças no comportamento ótico [71] e reológico [70], mesmo em concentrações de partículas tão pequenas quanto uma a quatro ordens de grandezas menores do que a concentração típica de ferrofluidos.…”