磁性液体磁特性的Monte Carlo方法模拟研究

探讨了利用Monte Carlo方法模拟研究磁性液体磁性能的物理模型与计算方法;并通过对一个含有32个磁性颗粒三维体系相对磁化强度的模拟与计算,定量地分析了磁性液体浓度、温度及所分散磁性颗粒的大小对磁性液体磁性能的影响。     

磁性液体的制备方法

本文介绍了磁性液体的组成,合成磁性液体的方法以及不同基体的磁性液体的制备。     

磁场下氮化铁磁性液体的表观密度研究

根据Bernoulli方程研究氮化铁磁性液体的表观密度，将磁性液体置于由FD-FM-A磁天平的两个励磁线圈产生的磁场下进行实验研究。在不同的磁场强度下，利用流体静力称衡法，用电子分析天平测量沉浸在磁性液体中测锤的质量，计算出不同高度下磁性液体的表观密度，来研究磁性粒子分布规律。实验结果表明：只有外磁场H具有梯度时，磁场才对氮化铁磁性液体中粒子的重新排布有贡献；Bernoulli方程中关于磁性液体的修正项μ0∫0^HMdH是合理的，否则密度将会出现负值。     

浅谈磁性液体

磁性材料是利用物质的磁性、各种磁效应以及它的声、光电、热特性来满足各方面技术要求的材料。磁性材料的种类很多 ,通常是以固态形式存在。随着科学技术的发展 ,固态形式的磁性材料已经不能满足高技术的特殊要求 (如宇航服的转动密封、传感器等 )。为此 ,科学家们研究开发了即具有磁性又具有流动性质的新型磁性材料———磁性液体。1　磁性液体的基本概念1 .1　什么是磁性液体磁性液体 (ＭａｇｎｅｔｉｃＬｉｑｕｉｄｓ) ,又称磁流体(ＭａｇｎｅｔｉｃＦｌｕｉｄｓ)、铁磁性流体 (Ｆｅｒｒｏｍａｇｎｅｔｉｃｆｌｕｉｄｓ)、磁性胶体 (Ｍ…     

浅谈磁性液体(续)

3　磁性液体的基本特性磁性液体的特性是磁性颗粒、界面活性剂及载液性能的综合表征。作为一种特殊的胶体体系 ,磁性液体同时兼有软磁性和流动性 ,因此它具有特殊的物理特性、化学特性及流体特性。3 .1　特殊的物理特性3 .1 .1　磁化特性磁性液体中的磁性颗粒平均为十几个纳米 ,比单畴临界尺寸还小 ,因此它能够自发磁化达到饱和 ,由于颗粒内磁矩在热运动的影响下任意取向 ,磁性颗粒处于超顺磁状态 ,因此磁性液体也呈超顺磁性。当磁性液体置于磁场中时 ,分子电流磁矩整齐排列 ,微粒中各磁矩的矢量之和不等于零 ,显示出磁性。3 .1 .2　热效应…     

纳米磁性液体的制备方法及应用

介绍了纳米磁性液体的组成、分类以及相关特性,重点阐述了纳米磁性液体的几种基本制备技术,探讨了磁性流体的相关应用,并对今后的发展方向进行了展望。     

新型功能材料——磁性液体

概述了磁性液体的特性、制备方法及其在不同方面的应用，其中又重点介绍了磁性液体密封技术和浮动选矿技术的特点。     

磁性液体的制备及应用

本文介绍了金属氧化物、金属、氧化铁磁性液体的制备方法和磁性液体应用的工作原理 ,以及磁性液体在密封、轴承、研磨、阻尼、潜艇推进器、分离技术(选矿 )、生物医学等方面的应用。     

胶溶法制备磁性液体工艺的研究

探讨了胶溶法制备磁性液体的工艺过程和影响因素。以Ｆｅ３Ｏ４超微粒子作核心磁性材料，油酸作为界面活性剂，通过溶法成功地制取了稳定性，流动民生，磁性能良好的油基磁性液体，并对其稳定性，流动性、磁性能作了分析讨论。     

液晶铁磁流体

把粒度１００Ａ的磁性颗粒掺到溶胀的层状相态中。据知，把固体晶粒稳定地存在于有序的液相中，这是首次。而且，当晶粒是磁性的时候，这种复合体系实现了二维磁性液体与非磁性流体交替周期性填充，并在磁场下显示出其特殊性能。     

A Mathematical model for prediction of currents,magnetic fields,melt velocities,melt topography and current efficiency in Hall-Héroult cells

The magnetic fields, current densitites, metal and electrolyte velocities, current efficiencies and topography of the electrolyte-metal interface within the Hall-Héroult cell used to produce aluminum have been predicted from first principles. The computation of current densities was carried out by solving Ohms law enabling the calculation of magnetic field vectors from the Biot-Savart law. The cross product of the current densities and magnetic fields then yielded the electromagnetic stirring forces acting on the molten metal and electrolyte. By employing a turbulence model and the time averaged Navier-Stokes equations, velocities within these two liquids could be calculated. The solution of the fluid flow equations yielded the pressure distribution within both elecrolyte and metal, permitting the calculation of the shape of the interface between these two liquids.     

Finely divided Fe-Co-Ni powders made by a thermochemical method

It is shown to be possible to make finely divided Fe-Co-Ni powders with given physicochemical properties. Iron, cobalt, and nickel oxalates have been made by chemical methods. Hydrogenous media have been used in the thermal decomposition of the iron oxalates to give finely divided powder that are nonpyrophoric and corrosion resistant and which have high contents of the metallic phase and given magnetic properties. These powders have been used in sealing composites for pipelines, and also as fillers in lacquers and magnetic liquids for general purposes.Institute for Colloid Chemistry and Water Chemistry, Ukrainian National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(384), pp. 111–113, March–April, 1996. Original article submitted June 20, 1994.     

Translational diffusion of liquids at surface of microporous materials: new theoretical analysis of field cycling magnetic relaxation measurements

1H spin-lattice relaxation rates of several aprotic polar liquids on calibrated microporous chromatographic glass beads that have paramagnetic ion impurities are recorded over magnetic field strengths using a field-switched magnetic relaxation dispersion spectrometer. The typical bilogarithmic magnetic field dependence of these rates supports quantitatively our theory of nuclear paramagnetic relaxation and gives the translational diffusion at the surface of nanopores. Our results demonstrate that magnetic relaxation dispersion at low magnetic field strengths in high surface area heterogeneous systems may be quantitatively understood in terms of the parameters of the spatial confinement and the local translational dynamics.     

Magnetic Resonance Imaging of Hydrocarbon-Contaminated Porous Media

Nuclear magnetic resonance response measurement is a nondestructive and nonintrusive technique, which is potentially useful for in situ characterization, mapping, and diagnostic purposes in hydrocarbon-contaminated subsurface, including rock. Magnetic resonance measurements of a porous medium allow the determination of necessary parameters to evaluate permeability and porosity of the medium and the type of hydrocarbons present in the pore fluid. This information is of particular importance in evaluation of hydrocarbon transport in contaminated soils. This paper presents the results of a preliminary study intended to evaluate the robustness of the magnetic resonance imaging technology using well-characterized laboratory specimens of porous material containing hydrocarbon liquids. First, a dry uniform sand pack impregnated with an aqueous coal tar mixture was imaged to evaluate discernable hydrocarbon distribution in the pore space of the sand column. Then, packed columns of glass beads of various sizes, permeated with distilled water and trichloroethylene, were imaged. The discernable images of the pore space and the interface of the two liquids in the pore space indicated that magnetic resonance imaging could be a viable tool to determine spatial distribution and mass fraction of hydrocarbon liquids in contaminated subsurface.     

离子液体电解质体系铝及铝合金电沉积与铝精炼研究进展

传统上,铝、稀土和碱金属及碱土金属等活泼金属主要是通过高温熔盐电解法得到,其电解工艺流程能耗高.近几年来,对离子液体的不断深入研究,提出离子液体为电解质体系用于金属铝、铝精炼和铝合金.综述目前采用离子液体体系进行铝及铝合金电沉积,粗铝、铝合金和铝基复合材料电解精炼回收铝的研究现状和研究进展.介绍和评述离子液体电解质电沉积、精炼铝的应用情况和所取得的研究成果,探讨离子液体电解质用于铝行业的发展趋势和研究动向.      

低温电镀铝的研究进展

综述了分别由有机溶剂、低温无机熔盐和离子液体构成的低温电镀铝体系的研究进展.有机溶剂和低温无机熔盐电镀铝各有优点,但前者的稳定性差,对水和氧敏感,电导率低;而后者较高的电镀温度限制了基体材料的选择.性能优异的离子液体备受青睐,研究最多的是以卤族为阴离子的离子液体,但是其在空气和水中易氧化和易吸潮变质而不稳定.稳定性更好的新型离子液体不断涌现,但缺乏系统研究.目前,除了电镀单一铝镀层之外,为了获得铝合金的特殊性能,电镀铝合金镀层越来越受到关注.对铝及铝合金镀层的巨大需求和远景期待将促使镀铝体系的推陈出新和镀铝工艺的不断进步,进而降低镀铝体系的成本,低温电镀铝的工业化应用将成为现实.     

离子液体在电沉积钛及其合金中的应用

离子液体作为一类新型绿色溶剂在电沉积活泼金属及合金方面具有重要作用,本文介绍离子液体在电沉积钛及钛合金方面的应用,探讨了钛及钛合金在离子液体中电解的电化学行为。用钛的卤化物为钛源,由于低价的钛氯化物在离子液体中的溶解度较低,在现有的离子液体中电沉积金属钛非常困难,需要继续寻找新的钛源及合适的离子液体。以二氧化钛为钛源,在离子液体中可以电积出部分金属钛。在离子液体中可以沉积出钛合金,但总的电流效率偏低。     

Mixing characteristics of a rotary tubular reactor used for processing slimy ores

A baffled rotary tubular reactor has been designed for hydrometallurgical processing of slimy ores. The mixing characteristics of the coarse solids, slimes, and liquids continuously fed into the reactor have been evaluated through residence time distribution studies. All three phases have similar mixing patterns in the reactor, as shown by similar vessel dispersion numbers.     

Behavior of Conducting Liquid within an Arc Furnace in a Vertical Magnetic Field

In a vertical magnetic field, bulk electromagnetic forces arise in conducting melt within the bath of a dc arc furnace. As a result, the melt is set in motion. The flow of slag and metal in the furnace bath may lead to effective mixing but may also have negative consequences, such as increased lining wear in the region of the hearth electrode. There has been little research on conductive mixing in the bath of a dc arc furnace. Theoretical concerns include the character of the flow in the bath under the action of magnetic fields of specific magnitude; practical considerations include the lack of simple and reliable sources of magnetic fields. In the present work, the utility of a transparent physical model in studying the flow of conducting liquid in an external vertical magnetic field is investigated. The applicability of the modeling results to processes in the 5-t bath of an industrial dc arc furnace is analyzed. It proves possible in principle to study the flow of conducting melt in external vertical magnetic fields on models based on transparent nonmetallic conducting liquids. The use of an aqueous solution of table salt permits assessment of the liquid velocity at its free surface and close to the hearth electrode by video recording. By physical modeling of the flow of conducting fluid in the bath under the action of an external vertical magnetic field, with different switching sequences of the hearth electrode and different currents in the bath, it is possible to establish the character of the liquid flow when the hearth electrode is at the center of the bath or somewhat displaced. The mean rate of liquid rotation in the horizontal plane is increased when the hearth electrode is at some distance from the bath axis. The strength of the vertical magnetic field producing conductive motion in the metal bath of a 5-t dc arc furnace is estimated: around 5 kA/m.