垂直梯度磁场作用下水平薄层磁性液体自然对流传热

１前言磁性液体是吸附着表面活性剂的固体磁性颗粒（如Ｆｅ３Ｏ４）分散于基液（如水）中而形成的稳态胶体溶液。它能在重力、磁力及离心力等外力场的作用下不凝聚、不沉淀,是一种集流动性。强磁性于一体的新型材料。磁性液体在化工、机械、电子、动力及航天航空等领域有...     

磁性液体的应用

磁性液体是一种特殊的新型纳米功能材料,是由磁性纳米微粒(一般要求小于10m)均匀弥散于某种液体基液中所构成的稳定的胶体体系。磁性纳米微粒和基液浑成一体,因此,具有将磁性和流动性两者合而为一的特性,从而衍生出一系列新颖奇异的性质。本文简要介绍了磁性液体应用领域的最新进展。     

磁场强化磁性液体自然对流传热的机理

在重力场中流体密度变化产生自然对流,在磁力场中磁性液体的表观密度随外加磁场强度的变化而明显变化,磁场可以改变磁性液体的自然对流.通过对磁场中的磁性液体的静力学计算和分析,建立一个由均匀磁场和均匀梯度磁场同轴叠加的合成磁场,合成磁场使磁场引起的磁性液体密度变化各处均等,各处的自然对流传热均等,从而使磁性液体的表观密度和自然对流传热系数得以准确测量,由此建立起磁性液体的磁场强度、表观密度、Grashof数之间的关联式.磁场强度的增大使磁性液体表观密度增大,使磁性液体处于超重状态,是磁场强化磁性液体自然对流传热的机理.     

磁性液体及其应用

综合评述磁性液体的制备及其应用     

磁性液体的研究现状

综述了磁性液体的研究现状,并对其种类、特性、应用范围以及制备和表征方法作了较为详细地介绍。     

磁性离子液体的应用研究进展

磁性离子液体是功能化离子液体,有很广阔的应用前景。目前磁性离子液体的研究很热门,但是很多内容并不完善,需要研究者更加努力地探索出具有强大功能的化合物。作者研究室最近报道的新型磁性离子液体双水相体系具有很强的优势,其在分离、分析领域具有很广的应用潜力。     

磁性液体密封在机械和化工行业的应用

磁性液体是由纳米级的强磁性粒子高度分散于基液之中所形成的稳定的胶体体系。介绍了磁性液体的性质及其在机械和化工行业中在动态密封方面的应用     

己二酸双轴混合器用磁性液体密封设计

传统的己二酸双轴混合器采用四氟填料进行密封,使用时间过长后容易发生泄漏,己二酸粉末会随着泄漏通道进入轴承箱,破坏轴承,影响正常生产。对新型己二酸混合器用磁性液体密封进行了设计,该密封具有无泄漏、寿命长、体积小等特点,其密封效果优于四氟填料密封,可保证生产安全,具有较高的推广价值。     

碳包裹磁性颗粒对离子液体的吸附研究

以Fe_3O_4为载体,通过浓硫酸蔗糖碳化法制备出Fe_3O_4/C复合材料,并通过X射线粉末衍射(XRD)和扫描电镜(SEM)对磁性复合材料进行表征,考察了其对水中5种咪唑离子液体的吸附性能。结果表明,Fe_3O_4/C可以有效脱除水中的离子液体,其饱和吸附容量为0.31⁰.41 mmol/g,随着离子液体烷基链的增长,吸附容量增加;吸附过程符合准二级动力学及Langmuir模型。Fe_3O_4/C经硫酸或丙酮溶液解吸之后可以多次重复利用。     

纳米水基磁性液体在肿瘤治疗领域的研究进展

结合作者在纳米磁性液体方面的研究经历,介绍了生物医学应用领域纳米磁性粒子的组成结构及特点,指出高分子改性纳米磁性粒子具有生物相容性好、稳定性强、载药量高的优点,并对目前高分子改性纳米四氧化三铁颗粒的制备方法及特点进行了对比分析。指出进一步研制磁响应性强、载药量高、粒度分布均匀的纳米磁性粒子,使之对癌细胞具有亲和作用,尽量避免对毛细血管网状内皮系统的清除,是未来肿瘤治疗领域纳米磁性粒子的研发目标,并对目前制备方法中存在的不足提出了改进的建议。     

Separation of Phosphorus and Magnetic Mineral Fines from Siderite Reductive Ore by Applying Magnetic Flocculation

The characteristics of siderite reductive ore and the ultrafine grinding-magnetic flocculation separation (MFS) of this ore were investigated in the present work. The results indicated that the iron phase in the raw ore was predominantly metallic iron with an iron particle size below 30 μm, and the phosphorus compound was apatite. By applying MFS to siderite reductive ore containing 37.14% Fe and 0.52 P, a concentrate assaying 66.37% Fe and 0.19 P with 74.32% recovery was produced. The iron recovery increased by 5.77% compared with the results of the conventional magnetic separation. The high efficiency in phosphorus removal and iron recovery achieved by the MFS process may be attributed to the adequate liberation of iron particles and the increase in magnetic force on the iron mineral fines in the form of flocs in a magnetic field.     

Instability of a Magnetic Fluid Jet in a Transverse Magnetic Field

The instability behavior of moving magnetic fluid jet in the presence of a constant uniform transverse magnetic field is investigated theoretically within the framework of linear stability analysis. The corresponding dispersion relation between the wave growth rate of instability and the magnitude of its wavenumber is obtained. The dependence of the wave growth rate on the polar angle in the presence of magnetic field is found. The influence of the magnetic field on the length of undisturbed jet section and the instability wavelength is studied. The correlation with the experimental results is demonstrated.     

醇-水共热法制备Fe3O4磁流体

报道了采用醇-水共热法制备稳定Fe3O4磁流体的工艺条件。应用透射电镜。X射线衍射仪。古埃磁天平对所制备的磁流体中的磁性颗粒的粒径。形貌，磁性等进行了表征。并分析了试验条件对制备的影响。     

纳米磁流体及其在癌症治疗中的应用研究进展

对纳米磁流体的组成、制备、应用进行了详细的综述。对纳米磁流体的制备方进行了评价,着重介绍了国内外纳米磁流体在癌症治疗中的应用研究进展。     

Velocity Field Structure and Flocculation Efficiency in Taylor-Couette Flow

Velocity field data were acquired for Taylor-Couette flow in the annulus gap between a rotating inner cylinder and a fixed concentric outer cylinder by using particle image velocimetry. The flocculation efficiencies were also obtained in the same Taylor-Couette flow under the conditions corresponding to the velocity field measurement. The flocculation efficiencies reached the maximum values due to the closed vortices, their contraction and expansion with time in wavy vortex flow. But out of the wavy vortex flow range, the comparatively low flocculation efficiencies were obtained due to the no-closed vortices which connected with each other.     

热疗用葡聚糖磁流体的制备及表征

用化学共沉淀法,以不同浓度的葡聚糖40000和20000水溶液作为分散剂,制备纳米铁氧体磁流体。铁氧体粒子的平均直径为15 nm左右,其分散主要依靠空间位阻作用维持。葡聚糖磁流体中铁氧体粒子与葡聚糖以氢键、范德华力结合,葡聚糖包覆量约为8%。随葡聚糖相对分子质量和浓度的升高,磁流体(2.45%)的稳定性上升,用50%葡聚糖40000水溶液制备的磁流体,在室温静置72 h以上,没有分层现象。     

掺Dy3+铁氧体硅油基磁流体磁特性与温度的相关性研究

利用液相共沉淀法制备了纳米掺Dy3+铁氧体磁颗粒,用表面活性剂修饰后,在超声振荡下分散在硅油中制得磁流体.分别用TEM、XRF、XRD、SQUID分析手段对样品进行了表征,在203 ～358 K范围内,研究了温度变化对磁流体磁特性和粘度的影响.结果表明:制备的磁颗粒平均粒径约16.3 nm、物相主要是Fe2O3、Dy2O3,结构为面心立方尖晶石型.通过磁性能测试发现,磁流体的饱和磁化强度(MS)、矫顽力(HC)和粘度随温度(T)的降低,呈现出增大的变化规律;并且还发现,298 K≤T≤358 K时,温度降低对矫顽力和粘度的影响较小;T＜298 K时,温度降低,矫顽力和粘度明显增大.     

磁粉-弱磁场耦合活性污泥系统深度处理电镀废水的研究

为提高电镀废水生物处理系统的稳定性,采用磁粉-弱磁场强化污泥系统。结果表明,实验系统COD_(Cr)、NH_3-N、Cu~(2+)和Ni~(2+)去除率分别比对照系统高12.55%、23.32%、21.13%和26.39%,污泥MLSS、FA(絮凝能力)和PN/PS(蛋白质/多糖)值也分别高出对照系统65.08%、68.48%和23.66%,强化后出水指标均达到电镀污染物排放新标准要求。     

Bending of Layer-by-Layer Films Driven by an External Magnetic Field

We report on optimized architectures containing layer-by-layer (LbL) films of natural rubber latex (NRL), carboxymethyl-chitosan (CMC) and magnetite (Fe₃O₄) nanoparticles (MNPs) deposited on flexible substrates, which could be easily bent by an external magnetic field. The mechanical response depended on the number of deposited layers and was explained semi-quantitatively with a fully atomistic model, where the LbL film was represented as superposing layers of hexagonal graphene-like atomic arrangements deposited on a stiffer substrate. The bending with no direct current or voltage being applied to a supramolecular structure containing biocompatible and antimicrobial materials represents a proof-of-principle experiment that is promising for tissue engineering applications in biomedicine.     

Experimental and Theoretical Study of an Autowave Process in a Magnetic Fluid

Magnetic fluid (MF) is a colloidal system consisting of ferromagnetic particles (magnetite) with a diameter of ~10 nm suspended in a dispersion medium of a carrier fluid (for example, kerosene). A distinctive feature of magnetic fluid is the fact that when an electric field is applied to it using two electrodes, thin layers consisting of close-packed particles of the dispersed phase are formed in the regions near the surface of both electrodes. These layers significantly affect the macroscopic properties of the colloidal system. In this work, the interpretation of the near-electrode layer is for the first time given as a new type of liquid membrane, in which the particles of the dispersed phase become charged with the opposite sign. On the basis of experimental studies, we propose a physicochemical mechanism of the autowave process in a cell with a magnetic fluid. It is based on the idea of oppositely recharging colloidal particles of magnetite in a liquid membrane. A mathematical model of an autowave process, which is described by a system of coupled partial differential equations of Nernst–Planck–Poisson and Navier–Stokes with appropriate boundary conditions, is proposed for the first time. One-dimensional, two-dimensional, and three-dimensional versions of the model are considered. The dependence of the frequency of concentration fluctuations on the stationary voltage between the electrodes was obtained, and the time of formation of a liquid membrane was estimated. Qualitative agreement between theoretical and experimental results has been established.