Sedlacik Michal, Pavlinek Vladimir, Peer Petra, Filip Petr
Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Nad Ovcirnou 3685, 760 01, Zlin, Czech Republic.
Dalton Trans. 2014 May 14;43(18):6919-24. doi: 10.1039/c4dt00166d.
Magnetic nanoparticles of spinel nanocrystalline cobalt ferrite were synthesized via the sol-gel method and subsequent annealing. The influence of the annealing temperature on the structure, magnetic properties, and magnetorheological effect was investigated. The finite crystallite size of the particles, determined by X-ray diffraction and the particle size observed via transmission electron microscopy, increased with the annealing temperature. The magnetic properties observed via a vibrating sample magnetometer showed that an increase in the annealing temperature leads to the increase in the magnetization saturation and, in contrast, a decrease in the coercivity. The effect of annealing on the magnetic properties of ferrite particles has been explained by the recrystallization process at high temperatures. This resulted in grain size growth and a decrease in an imposed stress relating to defects in the crystal lattice structure of the nanoparticles. The magnetorheological characteristics of suspensions of ferrite particles in silicone oil were measured using a rotational rheometer equipped with a magnetic field generator in both steady shear and small-strain oscillatory regimes. The magnetorheological performance expressed as a relative increase in the magnetoviscosity appeared to be significantly higher for suspensions of particles annealed at 1000 °C.
通过溶胶-凝胶法及随后的退火处理合成了尖晶石纳米晶钴铁氧体磁性纳米颗粒。研究了退火温度对结构、磁性能和磁流变效应的影响。通过X射线衍射确定的颗粒有限微晶尺寸以及通过透射电子显微镜观察到的颗粒尺寸随退火温度的升高而增大。通过振动样品磁强计观察到的磁性能表明，退火温度的升高导致饱和磁化强度增加，相反，矫顽力降低。高温下的再结晶过程解释了退火对铁氧体颗粒磁性能的影响。这导致晶粒尺寸增大，与纳米颗粒晶格结构缺陷相关的外加应力降低。使用配备磁场发生器的旋转流变仪在稳态剪切和小应变振荡模式下测量了铁氧体颗粒在硅油中的悬浮液的磁流变特性。对于在1000℃退火的颗粒悬浮液，以磁粘度相对增加表示的磁流变性能似乎明显更高。
