1. Dynamic and rate-dependent yielding behavior of Co0.9Ni0.1 microcluster based magnetorheological fluids
- Author
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Arief, Injamamul, Sahoo, Rasmita, and Mukhopadhyay, P. K.
- Subjects
Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Viscoplasticity ,Relaxation (NMR) ,Nucleation ,FOS: Physical sciences ,02 engineering and technology ,Condensed Matter - Soft Condensed Matter ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Shear rate ,Shear (sheet metal) ,Magnetization ,Nuclear magnetic resonance ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Magnetorheological fluid ,Soft Condensed Matter (cond-mat.soft) ,Composite material ,0210 nano-technology ,Glass transition - 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., Comment: Keywords: CoNi nanoclusters, magnetorheology, viscoplastic behavior, yield stress, viscous relaxation, multipolar interaction. 21 pages, 11 figures
- Published
- 2016