磁力旋流器磁系的磁场分析

设计了一种中心吸附铁化合物的磁力旋流器，利用试验和数值模拟的方法，对比分析了磁力旋流器磁场强度和分离性能。在试验中，简化了磁力旋流器磁系的结构，改变导磁铁片厚度、铁芯结构、磁系结构等参数，分析磁系对含铁化合物的吸附能力。利用数值模拟方法得到磁系的磁场强度，为分离能力预测提供依据。结果表明：磁场强度与导磁铁片的厚度成反比，随着导磁铁片厚度增大，磁场强度减小，磁力旋流器对铁化合物颗粒的吸附能力减弱，试验中导磁铁片的厚度为2mm时分离效果最好；铁棒铁芯磁系与铁管铁芯磁系相比具有更大的磁场强度；挤压式磁系与普通磁系相比具有更大的磁场强度。导磁铁片厚度的增大会使磁系端面漏磁量减少，铁芯侧面漏磁量增大；铁棒铁芯磁系的漏磁量相对较小，挤压式磁系的漏磁相对较小。     

Preparation and characterization of magnetic nanofibers with iron oxide nanoparticles and poly(ethylene terephthalate)

Iron oxide nanoparticle/Poly(ethylene terephthalate) (PET) nanowebs were obtained by electrospinning. To achieve superparamagnetic properties, iron oxide nanoparticles with diameters below 25 nm were used. Diameter distribution of iron oxide nanoparticles was measured by a particle size analyzer. Iron oxide nanoparticles were added into 16 wt % PET solution in the ratio of 5, 10, and 15 wt % to PET. The morphology of iron oxide nanoparticle/PET nanowebs was observed using field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The nanofiber diameter increased as increasing iron oxide nanoparticle concentration. The superparamagnetic behavior of iron oxide nanoparticle/PET nanofiber was confirmed using superconducting quantum interference device (SQUID). The degree of crystallinity of iron oxide nanoparticle/PET nanowebs was calculated from a differential scanning calorimeter (DSC) results. The change of flexural rigidity and tensile properties of electrospun iron oxide nanoparticle/PET nanowebs with the external magnetic field were examined ISO 9073-7 testing method, universal testing machine and an appropriate magnet. Also, the elastic modulus of iron oxide nanoparticle/PET nanofiber was measured using nanoindentation. With applying magnetic field, the improvement in mechanical properties of field-responsive magnetic nanofibers and nanowebs was confirmed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

横向旋转磁场作用下的液固流态化

利用横向旋转磁场发生器研究了铁颗粒以及铁－不锈钢混合颗粒的流态化特征．在一定条件下,实现了铁颗粒成链自旋．研究表明,旋转频率、磁场强度和添加铁颗粒的比例是影响流化质量的主要因素．实验表明,横向旋转磁场的旋转频率和磁场强度对铁颗粒及铁－不锈钢混合颗粒的最小流化速度影响很小     

磁化复混肥料的磁化工艺及磁性稳定性研究

实验室条件下以粉煤灰、钢渣粉、选铁尾矿粉为磁性材料,研究了磁性材料的磁化性能、生产磁化复混肥的磁化工艺及肥料磁性的稳定性,并测定了磁化复混肥料的重金属含量。结果表明,磁化工艺以先造粒后磁化为佳;以选铁尾矿粉为磁性材料,在磁化场强为8 000 mT下磁化10 s生产的磁化复混肥料磁化效果最佳,且放置时间对肥料的磁感应强度影响弱;以三种磁性材料制成的磁化复混肥料的重金属含量均低于国家标准,使用安全。     

Magnetic field effect on the anodic behaviour of a ferromagnetic electrode in acidic solutions

The magnetization of a ferromagnetic electrode in an external homogeneous magnetic field leads to a stray field in front of the electrode. This stray and its gradients can alter the anodic behaviour of the electrode significantly. Potentiodynamic polarisation measurements of an iron wire in a 0.5 M sulfuric acid solution (pH 0.25) and in a 0.5 M phthalate buffer solution (pH 5) without and with applied magnetic fields up to 0.6 T in different orientations to the electrode surface were performed. In sulfuric acid solution an increase of the diffusion-limited dissolution current density and a shift of the active-passive transition potential to more noble potentials was observed when the magnetic field was applied parallel to the electrode surface. In contrast, in perpendicular field configuration the diffusion-limited current density is lowered and the active-passive transition potential is shifted to less noble values. In phthalate buffer no significant influence of the magnetic field on the current density was observed in the active region, but a shift of the active-passive transition to less noble potentials occurred irrespective of the magnetic field configuration.The observed effects of a superimposed magnetic field on the anodic behaviour of iron are discussed with respect to an increase of the mass transport due to the Lorentz-force-driven magnetohydrodynamic (MHD) effect, the magnetic field gradient force and its interaction with the paramagnetic iron ions. The results of this paper show that the effect of the field gradient force can become very important due to the high magnetic field gradient at ferromagnetic electrodes.     

A Comparison Study on the Magneto-Responsive Properties and Swelling Behaviors of a Polyacrylamide-Based Hydrogel Incorporating with Magnetic Particles

This work investigates the mechanical properties, microstructures, and water-swelling behavior of a novel hydrogel filled with magnetic particles. The nanoparticles of magnetite (Fe₃O₄) and the micro-particles of carbonyl iron (CI) were selected and filled into a polyacrylamide (PAAM) hydrogel matrix to create two types of magnetic hydrogels. The isotropy and anisotropy of magnetic hydrogels are also presented in this study. The isotropic samples were cured without applying a magnetic field (MF), and the anisotropic samples were cured by applying an MF in the direction perpendicular to the thickness of the samples. The effects of the size, content, and inner structures of magnetic particles on the magneto-responsive and swelling properties of magnetic hydrogels were investigated. It was found that the magnetorheological (MR) effect of anisotropic samples was apparently higher than that of isotropic samples, and the hydrogels with CI exhibited a noticeable MR effect than those with Fe₃O₄. The storage modulus can be enhanced by increasing the filler content and size, forming an anisotropic structure, and applying an external MF. In addition, the magnetic hydrogels also have a swelling ability that can be tuned by varying the content and size of the particle fillers.     

Magnetic field sensitive functional elastomers with tuneable elastic modulus

The main purpose of the present work was to establish the effect of external magnetic field on the elastic modulus. We have prepared poly(dimethyl siloxane) networks loaded with randomly distributed carbonyl iron particles. It was found, that the elastic modulus of magnetoelasts could be increased by uniform magnetic field. In order to enhance the magnetic reinforcement effect, we have prepared anisotropic samples under uniform magnetic field. This procedure results in formation of chain-like structures from the carbonyl iron particles aligned parallel to the field direction. The effect of particle concentration, the intensity of uniform magnetic field as well as the spatial distribution of particles on the magnetic field induced excess modulus were studied. It was established that the uniaxial field structured composites exhibit larger excess modulus compared to the random particle dispersions. The most significant effect was found if the applied field is parallel to the particle alignment and to the mechanical stress. A phenomenological approach was proposed to describe the dependence of elastic modulus on the magnetic induction. The magnetic field sensitive soft materials with tuneable elastic properties may find usage in elastomer bearings and vibration absorber.     

The magnetic-nanofluid heat pipe with superior thermal properties through magnetic enhancement

This study developed a magnetic-nanofluid (MNF) heat pipe (MNFHP) with magnetically enhanced thermal properties. Its main characteristic was additional porous iron nozzle in the evaporator and the condenser to form a unique flowing pattern of MNF slug and vapor, and to magnetically shield the magnet attraction on MNF flowing. The results showed that an optimal thermal conductivity exists in the applied field of 200 Oe. Furthermore, the minor thermal performance of MNF at the condenser limited the thermal conductivity of the entire MNFHP, which was 1.6 times greater than that filled with water for the input power of 60 W. The feasibilities of an MNFHP with the magnetically enhanced heat transfer and the ability of vertical operation were proved for both a promising heat-dissipation device and the energy architecture integrated with an additional energy system.     

磁场调控磁性纳米流体流动和传热研究进展

磁性纳米流体在实现能量高效和可控传递领域极具发展潜力。本文综述了磁场作用下磁性纳米流体对流换热及沸腾换热的最新进展,主要包括强制对流换热、混合对流换热、自然对流换热、池沸腾换热及管内沸腾换热等方面的实验研究,分析了磁场类型、强度、梯度、频率、方向及磁铁位置等对磁性纳米流体流动和热传输特性的影响,指出可通过改变外加磁场来实现对磁性纳米流体流动和传热的控制,并探讨了磁性纳米流体流-磁耦合作用下的传热机理以及目前所面临的挑战。在此基础上,提出了未来磁场调控磁性纳米流体对流换热和沸腾换热的主要发展方向：制备稳定的磁性纳米流体,建立系统有效的流动和传热理论模型,并从微介观尺度诠释热-流-磁耦合协同换热机理。     

磁性液体在外施磁场下的方向性弱絮凝行为

磁性液体是一种高分子稳定胶体,实验观察发现磁性液体在外施磁场作用下,磁性颗粒沿着外磁场方向形成一定有序排列的球链簇,却又不是絮凝使胶体系统失稳,显示出与其它胶体系统的不同之处。在一般胶体系统中弱絮凝行为表现不明显,不引起重视,通过计算分析发现磁性液体在外加磁场下弱絮凝行为表现却异常明显,而且弱絮凝行为存在着方向性,又不使胶体系统失稳,与实验和实际应用相符。从而揭示了磁性液体在外施磁场作用下各向异性的机理,并且很好地解释了光波在在外施磁场作用下的磁性液体中会产生光的双折射效应等现象。     

磁场对电解法处理垃圾渗滤液的影响

以经过混凝处理后的新鲜垃圾渗滤液为研究对象,试验研究了恒定磁场和交变磁场对电解法处理垃圾渗滤液的影响.结果表明,恒定磁场与交变磁场都能使垃圾渗滤液COD降低;使用恒定磁场和交变磁场处理垃圾渗滤液30min后再进行电解处理,相比单独用电解处理,COD去除率分别提高了约17%和12%,恒定磁场的效果优于交变磁场;在电解的同时施加0.2970T的恒定磁场和交变磁场,相比单独使用电解处理,COD去除率分别提高了约20%和25%,交变磁场的效果优于恒定磁场.     

原位复合法制备磁性纤维素纤维及其性能研究

以天然棉纤维为基材,用原位复合法在上沉积磁性Fe3O4纳米粒子,制备出磁性纤维素纤维,利用X射线衍射仪、傅立叶变换红外光谱仪、扫描电子显微镜等方法对所得产物中磁性粒子进行表征。探究了预处理方法以及铁离子（Fe^3＋/Fe^2＋=2）浓度对制得的纤维磁性能的影响,并对磁性纳米粒子与纤维的结合牢度进行了讨论。结果表明：两个因素均会对纤维的磁性能产生影响,当用5%Na OH处理棉纤维原料,在铁离子总浓度为0.10 mol/L（Fe^3＋/Fe^2＋=2）反应时,最有利于磁性纳米颗粒在其表面的沉积,制得棉纤维复合材料的磁性能可以达到11.90 eum/g;经多次洗涤后磁性纤维的磁性能稍有下降,说明磁性纳米粒子对纤维附着力较好,期望被用作功能材料。     

Enhanced field emission properties of films consisting of Fe-core carbon nanotubes prepared under magnetic field

Films consisting of carbon nanotubes containing iron (CNTs-Fe) were prepared on tungsten substrates for electron field emission. The films were prepared by drying the mixture of the CNTs-Fe with poly [3-octyl-thiophene] (P3OT) or toluene under a magnetic field using a permanent magnet of surface magnetic flux 340 mT. The field emission properties of the films were measured in comparison with the films prepared without the magnetic field. The films prepared under the magnetic field showed better field emission characteristics than those without the magnetic field, and the electric field to generate the required field emission current was significantly decreased by applying the magnetic field in the film preparation process. Microscopic analyses indicated that the magnetic field had the effect of forcing the CNTs-Fe to stand perpendicular to the substrate, which causes the enhanced field emission properties.     

永磁梯度磁场布置方式对空气自然对流换热的影响

梯度磁场可用于控制非导电弱磁性介质的自然对流换热过程。利用钕-铁-硼永磁系统的不同空间布置，构建了具有不同磁场强度分布的梯度磁场，通过数值模拟得到了不同永磁梯度磁场的磁场强度和磁加速度。对不同梯度磁场作用下的二维封闭腔内的空气自然对流换热过程进行了数值研究，获得了空气自然对流的流场和温度场，以及壁面局部Nusselt数和平均Nusselt数并进行了比较。结果表明：空气自然对流换热可以通过施加具有不同磁加速度的梯度磁场得到强化或控制。     

Development of magnetoactive elastomers for sealing eye retina detachments

Magnetoactive elastomers (MAEs) on the basis of a silicone matrix filled with carbonyl iron microparticles are developed for an envisaged application in eye surgery for treatment of complicated retinal detachments. The proposed magnetic fixator of an eye retina consists of an MAE seal placed inside an eye in the area of a retinal break, and an external silicone sponge with embedded permanent magnets which can be sutured to the sclera to provide magnetic field acting on the internal MAE seal. For MAE seal development, MAEs of various compositions (containing 52–76 mass% of ferromagnetic iron microparticles) are synthesized and their surface, magnetic, mechanical, and rheological properties are investigated in external magnetic fields. To demonstrate MAEs efficacy as an element of the retina magnetic fixator, magnetic forces acting between MAE samples and systems of permanent magnets were measured in the curved configuration corresponding to the human eye geometry. It has been demonstrated that the pressure produced within the fixator can be varied in a wide range by tuning the MAE composition and MAE seal dimensions as well as by optimizing the size and configuration of permanent magnets within the external silicone sponge. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47425.     

Using the external magnetic field of composites to control fiber orientation and enhancement of electrical conductivity

The industrial developments have led to more applications of various composites. Since fiber orientation and distribution will influence product performance in composites, controlling said orientation and distribution is of critical importance. This study used external magnetic fields to control the fiber orientation and distribution in a polymer. The orientation of the actual fibers under magnetic field control during flowing was observed using a visualization system, which was made by PMMA and transparent epoxy as an upper cover and filling polymer. In order to clearly observe and calculate, 0.1 wt% fiber content was used, and 0.3 wt% fiber content was used to measure conductivity. Fiber distribution angles without a magnetic field concentrate parallel to the flow direction (0° ~ 30° and 151° ~ 180°) while distribution angles under magnetic field control were concentrated along the magnetic field direction, which was perpendicular to the flow direction (61° ~ 120°). The higher the magnetic flux density, the larger the torque of the electromagnetic field on the fibers and the higher the orientation of fibers was with the magnetic field. The electrical conductivity was 12.23 times higher for 1 mm fibers in an external magnetic field versus no magnetic field.     

Optimal conditions for labelling of 3T3 fibroblasts with magnetoliposomes without affecting cellular viability

A comparative study that deals with the internalisation of different types of magnetoliposomes (MLs) by 3T3 fibroblasts revealed that cationic MLs proved to be superior to neutral and anionic ones. Internalisation was visualised both by optical light and transmission electron microscopy. The latter showed that the cationic MLs ultimately ended up in lysosomal structures. The effect of increasing 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) concentrations in the cationic ML coat has been elucidated. High uptake efficiency was only achieved with MLs that carry a high DOTAP payload. However, these structures also demonstrated toxic effects. The use of the saturated distearoyl analogue (DSTAP) at identical concentrations led to improved uptake efficiency and lower toxicity. By using iron-oxide-free vesicles, it was shown that the toxicity was due to lipid bilayer constituents and not the iron oxide. In conclusion, the use of DMPC-DSTAP (96.67:3.33; molar ratio) MLs results in an extremely high labelling of 3T3 fibroblasts with iron oxides (47.66 pg Fe per cell) without evoking any influence on cell viability.     

Investigation into recovery of iron values from red mud dumps

The waste generated during the alumina production by Bayer’s process is popularly called red mud. This red mud is a rich source of iron values. Generally, the iron content in the red mud varies between 20% and 45% depending on the bauxite source. The present investigation was carried out to recover iron values from red mud. Red mud contains ultrafine particles and is highly alkaline in nature because of which it is difficult to recover the iron values from it using conventional beneficiation techniques. In the present investigation, the iron values were successfully recovered by reduction roasting followed by magnetic separation. During the process, the hematitic and goethitic iron-phase minerals present in the red mud sample are converted into magnetite and metallic irons, which are subsequently recovered using low-intensity magnetic separator. The results showed that an iron recovery of 61.85% with an iron content of 65.93% of iron concentrate could be obtained at roasting temperature of 1150°C, roasting time of 60 min, and magnetic field intensity of 0.18 Tesla.     

交变外磁场对硫酸钙垢溶解行为的影响及其机理

为阐明交变外磁场对硫酸钙垢溶解行为的影响规律,采用离子浓度、电导率和红外光谱等手段检测硫酸钙垢溶解液的性质,并利用X射线衍射（XRD）和检测硫酸钙垢溶解量等方法对硫酸钙垢进行表征和分析。结果表明,交变外磁场对硫酸钙垢的溶解有明显的促进作用。与无磁场作用的硫酸钙垢溶解液相比,交变外磁场作用60 min后硫酸钙垢溶解液的硫酸根质量浓度由2.41 g/L增大至3.52 g/L,电导率由5.85 mS/cm增大至7.24 mS/cm,硫酸钙垢的溶解量增加了40%。外加交变磁场可以促进硫酸钙垢溶解的原因是,外加交变磁场可以使蒸馏水中亲水性羟基的比例增加,促进水分子与硫酸钙垢的分子亲合力。此外,交变外磁场的作用还导致硫酸钙垢的结晶度减小、主晶面的面间距增大,最终有利于垢与水的接触和溶解。此研究可为利用交变外磁场调控硫酸钙垢的溶解行为提供理论依据。