Ghasemi E, Mirhabibi A, Edrissi M, Aghababazadeh R, Brydson R M
Advanced Ceramics and Metallic Centre of Excellence, Iran University of Science and Technology (LUST), Tehran 16844, Iran.
J Nanosci Nanotechnol. 2009 Jul;9(7):4273-8. doi: 10.1166/jnn.2009.m45.
As the ferrofluids are synthesized in a controlled atmosphere to Prevent oxidation of the magnetite phase; most reports of rheological properties have been derived from magnetite based ferrofluids. In this paper a ferrofluid based on iron oxide was synthesized by co-precipitation with air. Lauric acid was used to coat magnetic nanoparticles in the kerosene. The microstructural features of the ferrofluid and the variation with time and temperature of its rheologic and magnetic properties were investigated. The results indicated that the magnetic particles had an average size of 10.6 nm consisting of maghemite as the major phase. Viscosity of ferrofluid showed considerable variation with time and temperature. It was specified that the time dependency of the magnetoviscousity is related to particle size and rearrangement of nanoparticles of product is independent from the magnetic field. Moreover at low shear rates (< 0.1 s(-1)) the interaction of nanoparticles is related to the van der waals forces which cause the increase of the viscosity with time. The temperature effect showed that the magnetoviscosity decreases considerably above 45 degrees C.
由于铁磁流体是在可控气氛中合成以防止磁铁矿相氧化，大多数流变学性质的报告都来自基于磁铁矿的铁磁流体。本文通过在空气中共沉淀合成了一种基于氧化铁的铁磁流体。月桂酸用于在煤油中包覆磁性纳米颗粒。研究了铁磁流体的微观结构特征及其流变和磁性性质随时间和温度的变化。结果表明，磁性颗粒的平均尺寸为10.6nm，主要相为磁赤铁矿。铁磁流体的粘度随时间和温度有显著变化。明确指出磁粘性的时间依赖性与颗粒尺寸有关，产物纳米颗粒的重排与磁场无关。此外，在低剪切速率（<0.1 s(-1)）下，纳米颗粒的相互作用与范德华力有关，这导致粘度随时间增加。温度效应表明，在45℃以上磁粘性显著降低。
