Katiyar Ajay, Dhar Purbarun, Das Sarit K, Nandi Tandra
Research and Innovation Centre (DRDO), Indian Institute of Technology Madras Research Park, Chennai-600 113, India.
Soft Matter. 2015 Feb 28;11(8):1614-27. doi: 10.1039/c4sm02458c.
Magnetic nanocolloids consisting of synthesized superparamagnetic iron(II,III) oxide nanoparticles (SPION) (5-15 nm) dispersed in poly(ethylene glycol) (PEG) and a nano-silica complex have been synthesized. The PEG-nano-silica complex physically encapsulates the SPIONs, ensuring that there is no phase separation under high magnetic fields (∼1.2 T). Exhaustive magneto-rheological investigations have been performed to understand the structural behavior and response of the ferrocolloids. Remarkable stability and reversibility have been observed under magnetic field for concentrated systems. The results show the impact of particle concentration, size and encapsulation efficiency on parameters such as shear viscosity, yield stress, viscoelastic moduli, magneto-viscous hysteresis, and so on. Analytical models to reveal the system mechanism and mathematically predict the magneto-viscosity and magneto-yield stress have been developed. The mechanistic approach based on near-field magnetostatics and Néel-Brownian interactivities could predict the colloidal properties under the effect of the magnetic field accurately. The colloid exhibits amplified storage and loss moduli together with a highly augmented linear viscoelastic region under magnetic stimuli. The transition of the colloidal state from the fluidic phase to the soft condensed phase and its viscoelastic stimuli under the influence of a magnetic field has been explained based on the mathematical analysis. The remarkable stability, magnetic properties and accurate physical models reveal promise for the colloids in transient situations, namely, magneto-microelectromechanical/nanoelectromechanical devices, anti-seismic damping, biomedical invasive treatments, and so on.
已合成了磁性纳米胶体，其由分散在聚乙二醇（PEG）中的合成超顺磁性铁（II,III）氧化物纳米颗粒（SPION）（5 - 15纳米）和纳米二氧化硅复合物组成。PEG - 纳米二氧化硅复合物物理包裹着SPION，确保在高磁场（约1.2特斯拉）下不会发生相分离。已进行了详尽的磁流变研究，以了解铁胶体的结构行为和响应。在磁场作用下，对于浓缩体系观察到了显著的稳定性和可逆性。结果显示了颗粒浓度、尺寸和包裹效率对诸如剪切粘度、屈服应力、粘弹性模量、磁粘性滞后等参数的影响。已开发出分析模型以揭示系统机制并从数学上预测磁粘度和磁屈服应力。基于近场静磁学和奈尔 - 布朗相互作用的机理方法能够准确预测磁场作用下的胶体性质。在磁刺激下，该胶体表现出增强的储能模量和损耗模量以及高度增大的线性粘弹性区域。基于数学分析解释了在磁场影响下胶体状态从流体相到软凝聚相的转变及其粘弹性刺激。显著的稳定性、磁性和精确的物理模型表明这些胶体在瞬态情况下具有应用前景，即磁微机电/纳米机电装置、抗震阻尼、生物医学侵入性治疗等。
