搅拌轴磁性流体密封结构可靠性实验研究

根据纳米磁性流体密封原理,设计了搅拌轴纳米磁性流体密封结构,对搅拌轴长径比、转速、励磁电流大小与密封性能关系进行理论计算和实验研究。理论计算表明所设计的搅拌轴纳米磁性流体密封结构是可靠的。实验结果表明:当磁性流体初始密封压差比较大时,随轴长径比的增大,密封压差迅速减小,而当初始密封压差较小时,轴长径比的增大对密封压差的影响较小;当轴的转速较低时,轴的转速对磁性流体密封性能影响不大;励磁电流大小与密封性能成正比,但随着电流的进一步增加,密封压差的增加变得不明显。     

Smart Ferrofluid with Quick Gel Transformation in Tumors for MRI‐Guided Local Magnetic Thermochemotherapy

Improved techniques for local administration of anticancer drugs are needed to reduce the side effects of chemotherapy owing to leakage of anticancer drugs from tumors and to enhance therapeutic efficacy. This study presents the development of smart ferrofluid that transforms immediately into a gel in tumors and generates heat in response to an alternating magnetic field (AMF), simultaneously releasing the anticancer drug. The smart ferrofluid, which is synthesized using less toxic magnetic materials (Fe₃O₄ nanoparticles), natural polysaccharides (alginate), and amino acids (cysteine), can also act as a contrast agent for magnetic resonance imaging (MRI). The ferrofluid also incorporates an anticancer drug (i.e., doxorubicin, DOX) via hydrogen bonds. AMF causes heating of gels prepared from the DOX‐containing ferrofluid, resulting in gel shrinkage and DOX release. In vivo experiments demonstrated that the ferrofluid transforms into a gel in the tumor, with the gel remaining in the tumor. Furthermore, magnetic thermochemotherapy using this ferrofluid inhibited tumor growth, while magnetic hyperthermia alone had only a marginal effect. Thus, the combination of magnetic hyperthermia and chemotherapy may be important for suppressing tumor growth. In summary, the ferrofluid presented here has the potential to facilitate MRI‐guided magnetic thermochemotherapy through a combination of endoscopic technologies in the future.     

Euler‐Lagrangian Simulation of Magnetic Field Effects on the Mixed Convection of Ferrofluid

In this article, the hydro‐thermal behavior of a ferrofluid flow (kerosene and 4 vol% Fe₃O₄) in a vertical tube in the presence of different magnetic field gradients using a two‐phase Euler–Lagrange model and control volume technique has been reported. Two cases for the magnetic field gradients have been considered to affect the mixed convection of the ferrofluid: non‐uniform axial negative and positive field gradients. Unlike our previous studies instead of uniform nanoparticle distribution within the flow, it has been considered as non‐uniform (maximum concentration profile is at the flow centerline). Based on the obtained results in this case, the velocity profiles in the negative magnetic field gradients are more affected than our previous studies. Also the time variations of the Nusselt number and skin friction factor have been presented. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res 43(2): 148‐166, 2014; Published online 12 September 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21069     

铁磁流体互易性磁致旋光效应的传输特性及数值模拟

对水基铁磁流体在外加磁场作用下的磁致旋光效应的传输特性进行实验和数值模拟研究.在构建铁磁流体纵向磁光效应测试平台的基础上,对铁磁流体在恒定磁场、单个脉冲磁场以及连续方渡脉冲磁场作用下的磁致旋光效应进行了研究.结果表明,铁磁流体对偏振光振动方向的旋转与纵向调制磁场的方向无关;铁磁流体对于快脉冲磁场的响应是一个双指数弛豫过...     

水基铁磁流体磁致凝聚行为的三维耗散粒子动力学研究

用耗散粒子动力学方法对铁磁流体在外加恒定磁场作用下的凝聚行为进行了三维模拟.基于Flory-Huggins相混理论得到包括磁性颗粒珠子间的通常意义上的相互作用参数;利用Ewald方法把单磁畴结构的磁性颗粒长程的磁性相互作用转换成短程加和形式,从而得到磁偶极子的磁性相互作用参数.模拟结果表明,外加磁场强度是形成凝聚结构的...     

基于铁磁性液体的微差压传感器研究

差压是一种重要的力学参数,为了提高差压的测量精度,应用新型纳米材料--磁性液体设计了一种微差压传感器,建立了传感器的理论模型并对其输入输出关系进行了理论推导.该传感器采用螺线管式差动变压器的工作原理,其核心部分是可变互感,利用磁性液体兼具磁性和流动性的特点实现微差压的测量.实验表明,该种磁性液体微差压传感器具有工作压力范围大、线性度好、灵敏度高、稳定可靠等优点,可以广泛应用于工业过程控制、机械制造、生物医学工程等许多领域.     

A Liquid Gripper Based on Phase Transitional Metallic Ferrofluid

Magnetic fields enable dexterous, precise, and real-time control of ferromagnetic materials. However, most materials, including glasses, organics, and metals, are nonmagnetic and often do not respond to a magnetic field. Here, a transitional ferrofluid (TF) made by embedding magnetic iron particles into pure gallium through the treatment of highly concentrated HCl solutions, as well as its switchable interlocking force to objects during the phase change, is introduced to achieve magnetic manipulation of non-magnetic objects. A gripper made by liquid TF enables intimate contact with arbitrarily shaped objects and then generates a strong interlocking force of as high as 1168 N (using only 10 g TF) upon solidification at room temperature, which can be reversibly eliminated (F < 0.01 N) through melting. Owing to electrical conductivity and magnetism, a solid TF can be melted through electromagnetic induction heating. By coupling the switchable physical force during the phase transition and magnetism of TF, embedded non-magnetic objects can be manipulated using an applied magnetic field and become impervious to magnetic stimuli again after heating and releasing the TF. This study is expected to inspire numerous potential applications in the reversible magnetic actuation of soft robotics, remote operation systems, drug delivery, and liquid grippers.     

热疗用磁流体的热磁稳定性研究

采用两步法制备了环糊精(β-Cyclodextrin)改性纳米四氧化三铁(Fe3O4)磁流体.通过在交变磁场下感应加热对其磁热稳定性进行了研究,在交变磁场下加热后悬浮裸磁颗粒或改性颗粒的磁性液体最高升温分别达到63℃和53℃,感应加热实验结果表明所制磁流体可用于肿瘤的热疗研究.     

Ferrofluid lubrication of finite journal bearings using Jenkins model

The present study investigates hydrodynamic lubrication by ferrofluids of finite journal bearings using the Jenkins model. A magnetic field created by displaced finite wire is used. A numerical solution for the modified Reynolds equation using the finite difference method is obtained. Static characteristics of finite journal bearings are analyzed using 2 control parameters: magnetic force coefficient and Jenkins viscosity. The obtained results are compared to those from Neurenger‐Rosensweig model. It is shown that pressure, load capacity, attitude angle, and side leakage increase and friction factor decreases when increasing the value of each control parameter at low and medium eccentricity ratios. However, the Jenkins viscosity parameter decreases the load capacity and increases the friction factor at high eccentricity ratios.     

硅油基磁性液体

共沉淀法制备的磁性颗粒经分散剂处理后悬浮于硅油中得到了硅油基磁性液体。为了得到稳定的胶体，合成了一系列与硅油匹配很好的有机硅膦酸分散剂，其化学通式为XPS表面分析表明磁性颗粒与分散剂之间的作用为化学吸附。本文还测试了磁性液体的一些物理性能以及粘度随温度的变化情况。