Materials Research Centre, Indian Institute of Science, 560012 Bangalore, India.
Soft Matter. 2018 Jul 4;14(26):5407-5419. doi: 10.1039/c8sm00807h.
We report the magnetic field and particle-concentration dependent steady-state shear-responses of rod shaped Li-Zn ferrite particle based magnetorheological fluids (MRFs). Rod-shaped soft ferrimagnetic Li-Zn ferrite (Li0.4Zn0.2Fe2.4O4) particles were synthesized using the combustion synthesis method. MRFs of three different particle-concentrations (φ = 0.1, 0.2 and 0.4, in weight fraction) were prepared using silicone oil. Their yield strength and dynamic viscosity were studied at different applied magnetic fields (B). With an increase in B and φ, the yield strength (τY) of the MRFs increases. This behaviour is assigned to the formation of stronger columnar structures of the magnetically interacting particles which resist the flow (shear) of the MRF. For the MRF with φ = 0.4 and B = 1.2 T, we observed a maximum τY value of ∼1.25 kPa. Furthermore, we observed that, based on the on-state to off-state viscosity ratio (ηon/ηoff) at a particular operating B value, the optimum particle concentration required for energy- and cost-efficient operation of the MRFs can be chosen. The absence of a stabilizing-agent or de-agglomerating-coating, the low density, and the excellent oxidation- and corrosion-resistance of the soft ferrimagnetic rod-shaped Li-Zn ferrite particles make this MRF-system highly versatile and economical for many magneto-mechanical applications.
我们报告了基于棒状 Li-Zn 铁氧体颗粒的磁流变液（MRF）在磁场和颗粒浓度依赖的稳态剪切响应。棒状软铁磁性 Li-Zn 铁氧体（Li0.4Zn0.2Fe2.4O4）颗粒采用燃烧合成法合成。使用硅油制备了三种不同颗粒浓度（φ=0.1、0.2 和 0.4，重量分数）的 MRF。在不同的外加磁场（B）下研究了它们的屈服强度和动态粘度。随着 B 和 φ 的增加，MRF 的屈服强度（τY）增加。这种行为归因于磁相互作用颗粒形成更强的柱状结构，这些结构抵抗 MRF 的流动（剪切）。对于 φ=0.4 和 B=1.2 T 的 MRF，我们观察到最大 τY 值约为 1.25 kPa。此外，我们观察到，基于特定工作 B 值下的开启状态到关闭状态的粘度比（ηon/ηoff），可以选择用于 MRF 能量和成本高效操作的最佳颗粒浓度。这种 MRF 系统没有稳定剂或去团聚涂层、低密度以及软铁磁性棒状 Li-Zn 铁氧体颗粒优异的抗氧化性和耐腐蚀性，使其在许多磁机械应用中具有高度的多功能性和经济性。
