一种新型的基于磁性液体的光纤Sagnac磁场传感器

提出一种使用磁性液体的新型光纤Sagnac磁场传感器.磁性液体具有磁致可变双折射效应和二向色性,在外加磁场作用下,液体中的磁性纳米粒子沿磁场方向结链规则排列,形成各向异性.将其制成液体薄膜,放入具有一段保偏光纤的Sagnac环中,使光纤Saganc干涉仪的正弦形状干涉光谱可随外磁场变化.光纤中传输光垂直经过磁性液体薄膜...     

煤油基Fe_3O_4磁性液体薄层的光学特性研究

为研究煤油基Fe3O4磁性液体在磁场作用下的双折射效应和二向色性特性,根据振荡磁偶极子模型进行了理论分析和模拟计算,并设计了用于测试磁性液体光学特性的实验平台,测量了不同体积密度下的光学特性.通过理论分析和模拟计算发现,不同方向偏振光的折射系数和消光系数随磁场的变化相反,平行偏振光的折射系数和消光系数随外加磁场的增大而...     

磁性液体在磁场中产生光的双折射效应机理

磁性液体是一种特殊的高分子稳定胶体,在磁场中会产生光的双折射效应,对磁性液体在胶体学科方面展开研究,发现磁性液体在磁场中的弱絮凝行为表现异常明显,显示出特有的方向性,且又不至胶体系统失稳,证明了磁性液体中的磁性微粒在磁场中聚集成方向性的链状而又不失稳的临界状态存在。从而揭示了方向性弱絮凝是磁性液体在磁场中产生光的双折射效应的机理。     

W片的双折射

具有维格特效应的Ｗ片所显示的光学各向生中同时具备二向色性和双折射两个因素，两者均与波长有关，通常在双折射很微弱时予以忽略。本文提供了二向色性很强时双折射相当显著的实验结果，获得了一系列实验数据及曲线。本文还提供了一种同时测定一块Ｗ片的二向色性与双折射的原理及实验方法。     

磁性液体磁表面张力测试及其液膜拉脱过程受力分析

使用拉脱法测量了磁性液体的磁表面张力,根据计算机实时采集电压随时间的变化数据得到U-t曲线,进而将液膜拉脱过程分为6个阶段,分别研究了每个阶段的电压变化原因.无外加磁场作用时2F号磁性液体存在一电压变化较平缓的阶段,而白油和1F磁性液体并未出现此现象,这主要是因为白油和1F磁性液体表面张力较大,2F号磁性液体的表面张力较小造成.有外加磁场作用时,磁性液体的磁表面张力增加,主要是由于外加磁场增强了磁性颗粒之间的相互作用.     

磁光晶体Bi-YIG的磁致退偏效应

建立了磁光晶体磁致偏振特性测试系统。对Bi YIG晶体样品在大范围磁场下的退偏现象进行了测试。结果表明,达到磁饱和或接近磁饱和时,Bi YIG晶体的偏振性能最优;达到磁饱和后,随着磁场的增强,出现了磁致退偏效应。根据实验结果分析了磁致退偏效应的产生机理,并说明了磁致圆二向色性及磁致线双折射是产生退偏的原因。     

磁性液体薄膜的折射率在外加磁场作用下的变化特性研究

用两块玻璃夹持一层几个μm厚的磁性液体薄膜.将这一磁性液体薄膜垂直放置于由亥姆霍兹线圈建立的均匀磁场中.在迈克尔孙干涉仪上用对比测量法测量在不同外加磁场强度作用下磁性液体薄膜的折射率.实验发现, 磁性液体薄膜的折射率随外加磁场强度的变化而变化.结合实验研究, 提出了外加磁场改变了磁性液体颗粒链的大小, 改变了磁性颗粒链的大小和入射光波波长的比值, 从而改变了磁性液体的折射率的设想.初步建立起了磁性液体薄膜的折射率和外加磁场强度之间的关联式.为磁场测量、光学阀门等新型磁光器件的开发提供了新的技术.     

喇曼感生克尔效应光谱的琼斯矩阵分析

介绍喇曼感生克尔效应光谱(RIKES)的琼斯(Jones)矩阵分析方法.探测光束的传输强度不仅由所经过的每一个光学器件的琼斯矩阵所决定,而且还受到强的泵波在非线性介质样品中感生依赖于强度的二向色性和双折射(克尔效应)对琼斯矩阵的影响.同时计及样品和光学器件由强泵波作用下感生应力和其他外部产生的线双折射对喇曼感生克尔效应光谱观察的不利影响,导出测量系统的功率传输函数的完整表达式和喇曼感生克尔效应光谱的实现观察条件,最后简述以甲笨(C_7H_8)液体为试样的喇曼感生克尔效应光谱实验结果分析.     

磁性液体一阶磁浮力原理实验研究

基于伯努利方程推导了磁性液体的一阶磁浮力,实验研究了不同轴线上一阶磁浮力的变化规律,便于学生理解一阶磁浮力变化的本质原因.磁性液体一阶磁浮力受磁场强度、磁场梯度,以及磁性液体的饱和磁化强度和磁化率影响.沿z轴方向随磁场强度和磁场梯度减弱,一阶磁浮力逐渐变小并趋于零,磁性液体悬浮能力变弱.MFP-1磁性液体的饱和磁化强度和磁化率大于MFP-2磁性液体,其一阶磁浮力较大;电流为3.00 A时,MFP-1磁性液体将玻璃、铝、黄铜、紫铜和铅球悬浮,并出现Rosensweig尖峰,而MFP-2磁性液体仅将玻璃、铝和黄铜球悬浮.沿r轴方向不同高度处磁场强度和磁场梯度变化规律不同,随高度增加,磁场梯度逐渐趋于零,此时一阶磁浮力主要受磁场强度影响,测试杯壁处一阶磁浮力最小,出现了非磁性测试球上升过程中向测试杯壁移动现象.     

均匀磁场中磁性液体的磁表面张力系数实验研究

基于特殊性能的磁性液体增设了综合性设计性实验项目,根据项目式教学法初步实现了以学生自我训练为主的教学模式.本文设计了磁性液体磁表面张力系数智能测试仪,研究了均匀磁场中4种不同类型磁性液体的磁表面张力系数随磁感应强度的变化规律.随外加磁场磁感应强度的增强,磁性液体的磁表面张力系数增大,主要是磁场增强了磁性颗粒之间的相互作用力.磁感应强度相同时,载液质量对磁性液体的磁表面张力系数影响较大,载液质量越小,单位体积内融入的磁性颗粒数量越多,导致磁性液体的磁表面张力系数越大.表面活性剂种类对磁性液体磁表面张力系数的影响也较大,由于油酸对磁性颗粒的吸附作用比PBSI-941表面活性剂强,油酸官能团较早吸附在磁性颗粒表面,限制了磁性颗粒进一步长大,导致MFO-4磁性液体磁表面张力系数较小.     

Concurrent measurement of linear birefringence and dichroism in ferrofluids using rotating-wave-plate Stokes polarimeter

In this study, an optical scheme based on Stokes–Mueller Formalism and rotating-wave-plate Stokes polarimeter is successfully developed for obtaining concurrent measurements of the linear birefringence and dichroism. For a quarter-wave plate sample, the measured values of the principal axis angle and retardance are found to have average absolute and normalized errors of 0.0859° and 0.76%, respectively, while the measured dichroism of the quarter-wave plate has an average value of 0.0203. When analyzing ferrofluid film samples with concentrations ranging from 2 to 6%, it was found that for a given concentration of ferrofluid, retardance increases with applied magnetic fields and tends to saturate at high levels. Additionally, under the condition of the same magnetic field, the experimental results show that retardance is proportional to the concentration; the higher concentration will result in more retardance and absorption. Consequently, the derived algorithm for concurrent measurements of the linear birefringence and dichroism is feasible, and the relation between the concentration and magneto-optical effect was successfully investigated.     

磁流体磁光特性的研究及其应用

研究稀磁液磁致双折射效应与磁液各参量及磁场的关系，并基于其磁光弛豫特性与载液粘度的关系（爱因斯坦方程）初步分析了磁液光纤磁光粘地性及其应用的可行性。     

非磁性微球掺杂对纳米磁流体场诱导双折射特性的影响

利用二氧化硅和聚苯乙烯非磁性微球掺入铁氧体纯磁流体中,制得了复合磁流体.定性地研究了复合磁流体在外磁场作用下的双折射与非磁性微球的种类、掺杂浓度以及纯磁流体自身浓度的关系.研究表明,不同浓度的纯磁流体掺杂等量的聚苯乙烯微球对其双折射随磁场的变化趋势影响不同|同一浓度的纯磁流体掺杂不同种类的非磁性微球,对其双折射的影响也不同|掺杂等量但不同比例的两种非磁性混合微球所形成的复合磁流体中,其中一种非磁性微球对其双折射的影响起主导作用,使得该复合磁流体双折射随磁场的变化趋势与起主导作用的非磁性微球单独掺杂时相似.     

Preparation of composite with silica-coated nanoparticles of iron oxide spinels for applications based on magnetically induced hyperthermia

It is reported a novel method to prepare magnetic core (iron oxide spinels)–shell (silica) composites containing well-dispersed magnetic nanoparticles in aqueous solution. The synthetic process consists of two steps. In a first step, iron oxide nanoparticles obtained through co-precipitation are dispersed in an aqueous solution containing tetramethylammonium hydroxide; in a second step, particles of this sample are coated with silica, through hydrolyzation of tetraethyl orthosilicate. The intrinsic atomic structure and essential properties of the core–shell system were assessed with powder X-ray diffraction, Fourier transform infrared spectrometry, Mössbauer spectroscopy and transmission electron microscopy. The heat released by this ferrofluid under an AC-generated magnetic field was evaluated by following the temperature evolution under increasing magnetic field strengths. Results strongly indicate that this ferrofluid based on silica-coated iron oxide spinels is technologically a very promising material to be used in medical practices, in oncology.     

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Based on the superparamagnetism of the ferrofluid which can receive the magnetic force after magnetization by the magnetic field, and there is no magnetic hysteresis after demagnetization, this paper presents a dynamic control method of the ferrofluid. The electromagnetic field is directly added to ferroliquid-column in the air domain to achieve the dynamic deflection. The surface tension, gravity force and magnetic force are added to the modified N-S control equation, and the magnetic induction equation is combined. The ferrohydrodynamics (FHD) model is established. The model of volume of fluid (VOF) is presented to describe ferrofluid jetting in the air domain with the secondary development of fluent. The liquid phase distribution and dispersion of ferrofluid are simulated under different magnetic field intensity. The effect of magnetism on its dynamical behavior is analyzed. The results show that with the increase of magnetic field intensity and jet distance, the ferrofluid velocity along the magnetic field direction and the offset increase, and its dispersion is gradually obvious.     

空气域中铁磁流体动态控制研究

根据铁磁流体磁化后会受到磁力,退磁后不存在任何磁滞的超顺磁性质,提出了铁磁流体的动态控制方法,对喷射在空气域中的铁磁流体液柱直接添加电磁场实现其动态偏转驱动。在修正后的纳维-斯托克斯(N-S) 控制方程中加入表面张力、重力及磁力,并结合磁感应方程,建立了铁磁流体动力学(FHD)模型。利用二次开发的Fluent流体仿真软件建立了铁磁流体在空气域中喷射的流体体积函数(VOF)多相流模型,仿真了在不同磁场强度下铁磁流体的液相分布及分散状况,分析了磁性对其动力学行为的影响。结果表明,随着磁场强度和喷射距离的增大,铁磁流体沿磁场方向速度及偏移量增大,其发散情况逐渐明显。     

Reciprocity of Faraday effect in ferrofluid: Comparison with magneto-optical glass

The transmission light intensity method is carried out on a classical platform to study the reciprocity of Faraday effect in water-based Fe₃O₄ ferrofluid and its diluents. Setting the polarization direction of the analyzer at an angle of 45° to that of the polarizer, the switchable DC magnetic field and the alternating magnetic field are imposed to ferrofluid. The ferrofluid film is replaced by magneto-optical glass for contrastive experiments. The results indicate that ferrofluid is different with magneto-optical glass. Even though the direction of magnetic field is reversed, the rotation direction of the polarized light does not change for ferrofluid. The theoretical model of magneto-optical rotation was used to describe the origin of the reciprocity of Faraday effect in ferrofluid and the non-reciprocity in magneto-optical glass. These findings suggest that the magnetic moments of nanoparticles in ferrofluid tend to the same orientation with the magnetic field because of the rotation of particles.     

梯度磁场作用下光纤中磁流体光透射特性研究的建模与分析

对光纤中磁流体在梯度磁场作用下的光透射特性进行了研究,提出光纤中磁流体的光透射率变化主要来源于梯度磁场引起的磁流体密度分布变化。根据郎之万函数和流体理论,推导了光纤中磁流体在梯度磁场作用下的密度分布,并根据Beer-Lambert定律,得到磁流体光功率透射衰减和纳米粒子局部密度的关系,从而建立光纤中磁流体在梯度磁场作用下光透射特性的理论模型。进而对光纤中磁流体在不同梯度磁场作用下的光透射功率进行数值分析,得到不同磁场强度和磁场梯度下光纤中磁流体透射功率的变化规律。最后将数值分析的结果和实验数据进行对比,验证了模型的合理性, 同时也验证了梯度磁场作用下磁流体光透射功率的变化主要来源于磁流体密度分布变化的推论。     

The measurements of anisotropy of ultrasound propagation and magnetic susceptibility in viscous ferrofluid

Results of experimental study of anisotropy of ultrasound propagation and anisotropy of magnetic susceptibility in a ferrofluid of considerable viscosity are reported. The dependence of the propagation velocity and absorption coefficient of ultrasonic wave on the angle between the direction of measurement and that of the magnetic field provides important information on the ferrofluid structure in a magnetic field. The results show that the ultrasonic absorption coefficient of a wave propagating in a viscous ferrofluid in a DC magnetic field depends mainly on the rotational degree of freedom. Measurements of the anisotropy of the magnetic susceptibility of a ferrofluid bring the information on the magnetic moment of the magnetic particles and their mean radius.     

Magneto-optical study of the orientation confinement of particles in ferrolyotropic systems

Ferrosmectics and ferrohexagonals are magnetic liquid crystals which consist of a lamellar and a hexagonal phase in which magnetic nanoparticles are incorporated. The magnetic field variation and the relaxation of the linear optical birefringence of ferrosmectics and ferrohexagonals and its time relaxation are measured in different geometries and compared with that of a ferrofluid sample. We interpret our data by the existence of a mean orientation of the magnetic particles in the lyotropic structure, which appears to be non-random in zero field. We conclude that the magnetic moments of the particles are preferentially aligned in the plane of the ferrosmectic layers and along the axis of the ferrohexagonal cylinders, respectively. To account for this preferred alignment, we propose that some of the particles in the ferrosmectic are adsorbed on the surfactant layers with their moment aligned in the lamellar plane, while the orientation of the moments in the ferrohexagonal is restricted to a cone around the cylinder axis. Received 31 December 1998 and Received in final form 22 September 1999