Dynamic and rate-dependent yielding behavior of Co0.9Ni0.1 microcluster based magnetorheological fluids

Abstract

Abstract:In this paper we performed steady shear and oscillatory magnetorheological (MR) studies in magnetic fluids containing CoNi nanoclusters of 450 nm in diameter. Co-rich nanoclusters were synthesized by conventional homogeneous nucleation without any external surfactant or reducing agent in liquid polyol at elevated temperature. The x-ray diffraction, energy dispersive X-Ray analysis, scanning and transmission electron microscopy studies were done for analyzing the sample composition and morphology. Two variants of fluid samples were prepared by dispersing 15 vol% and 20 Vol% of CoNi powders in castor oil. Room temperature steady magnetoshear studies indicate viscoplastic behavior with stronger dependence of static yield stress on magnetization than a dipolar coupling that was operational in the dynamic yield stress. Magnetosweep measurements at constant shear rate showed interesting relaxation at high magnetic fields. We also explored dynamical elastic behavior through oscillatory magnetorheological studies under both strain sweep and frequency sweep modes, and showed glass transition like phenomenon occurring in them above critical shear amplitudes.

Tuning Electromagnetic Interference Shielding Performance through Controlled Alignment of Ni Nanowires in Soft PDMS Composites

“…For small-angle oscillatory strain (SAOS), both the aligned and nonaligned composites demonstrated typically uncharacteristic behavior. The response of storage and loss moduli as functions of frequency was predictable and as expected, G ′ of the aligned composites displayed nearly frequency-independent behavior owing to stronger interparticle attraction under low strain, exacerbated by aligned magnetic reinforcement . Therefore, the slope of G ′ curve for sample S5 was higher compared to that of sample S6 .…”

Magnetorheology: a review

“…Noma et al 34 used arc plasma to fabricate spherical crystalline Fe nanoparticles of 100 nm diameter and a saturation magnetization of 190 emu g À1 . Arief and Mukhopadhyay used polyol methods to synthesize Co 0.9 Ni 0.1 particles of 450 nm diameter 35 and hydrothermal reduction to fabricate CoNi nanoplatelets. 36 Nickel nanowires were fabricated by Xia et al 37,38 using a one-step synthesis method.…”

Polymer-Magnetic Composite Particles of Fe3O4/Poly(o-anisidine) and Their Suspension Characteristics under Applied Magnetic Fields

“…When the external field is being removed again, it returns back to a liquid state, showing the characteristics of Newtonian fluid [ 6 , 7 , 8 , 9 ]. These properties have been used in a variety of industrial applications such as brakes, dampers, clutches, and shock absorbers due to their excellent mechanical properties with large yield stresses [ 10 , 11 ].…”