Techniques and Apparatus for Measuring Rotational Core Losses of Soft Magnetic Materials

In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux density vector is rotating. Therefore, the magnetic properties of the core materials under the rotating flux density vector excitation should be properly measured, modeled and applied in the design and analysis of these electromagnetic devices. This paper presents an extensive review on the development of techniques and apparatus for measuring the rotational core losses of soft magnetic materials based on the experiences of various researchers in the last hundred years.

Study on magnetic memory signals of medium carbon steel specimens with surface crack precut during loading process

Static tensile test and tensile-tensile fatigue test of medium carbon steel sheet specimens with surface crack precut were performed on MTS810 hydraulic testing machine to clear the meaning of the point of Hp(y) value zero. Magnetic memory signals were measured during the test process. The results show that only one point of Hp(y) zero value exists in all measured magnetic signal curves during the loading process, which should be a sign of intersection of positive-negative magnetic poles after magnetic ordered state appears and does not indicate the position of surface crack precut. The analysis shows that the surface crack precut can not interrupt the magnetic ordered state occurred during the test completely, hence its Hp(y) value is not zero. However, the crack extending to a penetrated defect at the instant of specimen′s fracture leads to the discontinuance of magnetic ordered state.

Enhancing magnetic properties of anisotropic NdDyFeCoNbCuB powder by applying magnetic field at high temperature during hydrogen desorption

Anisotropic powder was prepared with precursor （NdDy）-（FeCoNbCu）-B sintered magnets by hydrogen decrepitation, desorption, and subsequent annealing treatment. The hydrogen desorption was performed in magnetic fields of 0, 1, 3, and 5 T. The orientation of tetragonal phase grains of the powder was evaluated from the hysteresis loops measured by extraction magnetometer. Residual hydrogen content of the powder was evaluated by thermal-magnetic analysis. The powder with Hcj, Br, and （BH）max of 1138 kA.m^-1, 1.029 T, and 172.5 kJ.m^-3, respectively, was achieved under the condition of the magnetic field of 3 T. Magnetic properties of the powder, especially, the remanence of the powder, are enhanced upon magnetic fields, which is due to better orientation of powder particles and less residual hydrogen in the powder resulted from the magnetic field during the hydrogen desorption process.

Effect of Plastic Deformation on Magnetic Properties of Fe-40%Ni-2%Mn Austenitic Alloy

The effects of plastic deformation on the magnetic properties of austenite structure in an Fe-40% Ni-2 % Mn alloy is investigated by using Mossbauer spectroscopy and Differential Scanning Calorimetry （DSC） techniques The morphology of the alloy has been obtained by using Scanning Electron Microscopy （SEM）. The magnetic behaviour of austenite state is ferromagnetic. After plastic deformation, a mixed magnetic structure including both paramagnet- ic and ferromagnetic states has been obtained at the room temperature. The volume fraction changes, the effective hyperfine fields of the ferromagnetic austenite phase and isomery shift values have also been determined by Mossbauer spectroscopy. The Curie point （Tc） and the Neel temperature （TN） have been investigated by means of DSC system for non-deformed and deformed Fe-Ni-Mn alloy. The plastic deformation of the alloy reduces the TN and enhances the paramagnetic character of austenitic Fe-Ni-Mn alloy.

Renormalization of spin polarised itinerant electron bands in the normal state of a model ferromagnetic superconductor

This paper studies the normal state properties of itinerant electrons in a toy model, which is constructed according to the model for coexisting ferromagnetism and superconductivity proposed by Suhl [Suhl H 2001 Phys. Rev. Lett. 87 167007]. In this theory with ferromagnetic ordering based on localized spins, the exchange interaction J between conduction electrons and localized spin is taken as the pairing glue for s-wave superconductivity. It shows that this J term will first renormalize the normal state single conduction electron structures substantially. It finds dramatically enhanced or suppressed magnetization of itinerant electrons for positive or negative J. Singlet Cooper pairing can be ruled out due to strong spin polarisation in the J 〉 0 case while a narrow window for s-wave superconductivity is opened around some ferromagnetic J.

Structural Dependence of Magnetic and Transport Properties in Doped Manganite Perovskites

In this paper, the magnetic and transport properties in ABO3-type perovskite-like manganites as functions of the structure have been discussed from the viewpoints of A- and B-site doping, respectively. For the A-site doping, two simple parameters, tolerance factor t and variance of the A-cation radius distribution s, can be used to characterize the magnetic/resistive phase diagram. For the B-site doping, the case is complicated due to the direct action to the center of double exchange. However, the dopant-size-induced local strain effect plays an important role in the physical properties besides the size mismatch between A- and B-site ions.

Magnetic, dielectric and luminescence synergetic switchable effects in molecular material [Et_(3)NCH_(2)Cl]_(2)[MnBr_(4)]

The application of multifunctional materials in various fields such as electronics and signal processors has attracted massive attention. Herein, a new organic-inorganic hybrid material [Et_(3)NCH_(2)Cl]_(2)[MnBr_(4)](1) is reported, which contains two organic amines cations and one [MnBr_(4)] tetrahedral ion. Compound 1 has a dielectric anomaly signal at 338 K, which proves its thermodynamic phase transition. The single crystal measurements at 200 K and 380 K show that the phase transition of compound 1 is caused by the thermal vibration of organic amine cations in the lattice. Moreover, compound 1 shows yellow-green luminescence under UV light irradiation. The magnetism measurements indicate that compound 1 shows switchable magnetic properties. This organic–inorganic material is a multifunctional material with dielectric, optical, and magnetic synergetic switchable effects, which expands a new direction for designing multifunctional materials.

星载材料极弱剩磁测量方法研究

为解决科学探测卫星星载材料微弱磁性测量难题,本文提出了一种卫星部件极弱剩磁的测量方法,并研制了测量系统。利用屏蔽技术去除外界磁场干扰,在屏蔽系统内搭建了测量系统,使用零场原子磁力仪采集旋转试件的磁场频谱信息,通过小波多分辨分析方法处理得到试件的磁特征数据。研究表明:本文方法可有效提取极弱剩磁信号,且系统稳定度优于1×10^(-12) T/30 min,磁场分辨率优于1×10^(-12) T,磁矩提取分辨量级可达10^(-6) A·m^(2),为整星磁洁净控制和空间磁场高精度探测提供了途径。

氧化物中存在O2p空穴的典型实验结果和磁性氧化物的O2p巡游电子模型

负二价氧离子具有满壳层价电子结构(2s^(2)2p^(6)).负一价氧离子的价电子结构为2s^(2)2p^(5),相当于存在1个O2p空穴.传统的凝聚态物理和材料化学研究中都假设氧化物中的氧离子全部为负二价离子,在迄今为止的绝大多数研究氧化物磁性和电输运性质的报道中,采用关于磁有序的超交换和双交换作用模型,都没有考虑O2p空穴的影响.然而,许多价电子状态实验证明,在氧化物中存在不可忽略的O2p空穴,即存在不可忽略的负一价氧离子,其占比可达30%或更多.基于这些实验结果,对传统磁有序模型进行改进,英美学者首先进行了探讨,笔者所在课题组与中国科学院物理研究所磁学国家重点实验室合作进行了系统的研究.介绍了相关的典型实验结果和理论模型.

光纤磁场传感器研究进展与发展趋势

磁场传感器在资源勘探、工业生产及地磁检测等多个领域有着广泛的应用。传统电类磁场传感器稳定性好,但存在易受化学腐蚀、成本高、体积大,以及抗干扰能力差等缺点;相比之下,光纤磁场传感器具有结构紧凑、高精度、体积小和抗电磁干扰能力强等优点。现有的光纤磁场传感器根据基本原理主要包括以下4类:基于磁致伸缩材料、基于磁流体材料、基于法拉第效应、基于光纤激光器。特别是基于磁致伸缩效应的光纤磁场传感器,在制造工艺和应用方面具有更多优势。本文介绍了用于磁场测量的光纤传感技术的发展,分析了4种不同类型传感器的原理、优缺点及研究现状。同时,还介绍了光纤磁场传感器在地磁监测方面的应用。最后,分析了光纤磁场传感器面临的挑战和未来发展趋势。

软磁不锈钢环样和棒样磁性能测量结果差异及其机理分析

随着自动控制领域对软磁不锈钢磁性能和综合性能的要求越来越高,软磁不锈钢的磁性能检测变得越来越重要。首先介绍了软磁材料的起始磁化曲线和正常磁化曲线,然后对软磁不锈钢磁性能检测中标准规定的环样法和棒样法(磁导计法)的磁性能测试结果进行比较和分析,对存在差异的原因进行了探讨,并对以后在测量中可能采取的措施进行了介绍。实验证明,环样法和棒样法间磁性能的差异是普遍存在的一种现象。受测试方法的限制,只有采取合理的措施,才能得到供需双方都能认可的测量结果。

Magnetic field measurement on ^(87)Rb atomic fountain clock

An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of 87Rb hyperfine transition is presented.By mu-metal shielding and coils compensating,the magnetic fluctuations resulting from asymmetry and instability are less than 10 and 0.025 nT,respectively.The relative frequency uncertainty of atomic fountain clock caused by the magnetic field is less than 5.4×10-16.

Ferromagnetic–paramagnetic transition temperature in bulk and nanostructured La_(0.7)Sr_xCa_(0.3-x)MnO_3(x=0.10, 0.15, and 0.20) manganite materials

Series of bulk and nanostructured La0.7SrxCa0.3-xMnO3（x = 0.10, 0.15, and 0.20） manganites were synthesized and characterized using different techniques. In the series, both the bulk and nanostructured La0.7Sr0.10Ca0.20MnO3 and La0.7Sr0.20Ca0.10MnO3 manganites have orthorhombic and rhombohedral structures, whereas La0.7Sr0.15Ca0.15MnO3 manganite has rhombohedral and orthorhombic structures, respectively. Online ultrasonic velocity and attenuation measurements were taken through an indigenously designed ultrasonic setup, and the analysis was done from 300 to 400 K during the aging of the samples to explore the structural/phase transitions. The bulk and nanocrystalline La0.7SrxCa0.3-xMnO3 perovskite samples show the particle size distribution in the range of 197-943 and 24-93 nm, respectively. The addition of Sr^2＋ alters the size of particles, which decrease in size. The observed anomaly in ultrasonic velocities, attenuations, and elastic moduli is correlated with the ferromagnetic-paramagnetic（FM-PM） transition temperature（TC） in both bulk and nanocrystalline perovskites. In addition, the shift in TC and the magnitude and width of observed anomaly are correlated with the value of x to study the behavior of TC.

预加热-碳热还原-磁选法提取煤矸石中的铁

中国是全球最大的煤炭生产与消费国之一,每年的煤炭生产及消费总量平均达到3×10^(8)t。目前,我国累计堆积煤矸石总量已达5×10^(9)t,其中规模较大的矸石山有1900座,占用土地15×10^(7)m^(2),并且每年以1.5×10^(8)—2.0×10^(8)t的速度递增。如果能找到科学的利用方法,将这些大量存在的煤矸石变废为宝,则会产生重大的经济效益。煤矸石资源综合利用在中国尚处于发展阶段,主要集中在建筑材料领域方面,如制砖、生产水泥和其他建筑材料。此外,煤矸石也被用于发电和化工领域,如提取氧化铝和白炭黑等,但提取技术和利用率有限。目前,亟需开发煤矸石高值化的应用技术,以进一步提高其利用价值。煤矸石中除了含有大量硅铝外,还含有一定量的硫铁矿。考虑到铁的市场价值,可以采用碳热还原的方法还原出铁单质。然而,煤矸石中的碳大多以有机物的形式存在,不仅还原无法起到作用,还会在加热过程中导致煤矸石粉末黏连,以至于影响到铁的回收率。因此,提出先在空气气氛中焙烧煤矸石,以去除其中的有机物并将硫铁矿氧化为氧化铁,然后在焙烧后的物料中加入适量的碳,在氮气气氛中高温焙烧还原出铁粉,最后采用磁选法提取磁性铁。最佳还原条件为空气氛围中1000℃下预焙烧1 h,再在氮气气氛中1100℃下碳热还原1.5 h,其中碳氧摩尔比为2.0,煤矸石粒度为48μm。经过碳热还原后,TFe的回收率达到71.3%。除铁后的煤矸石含铁量低,适合做分子筛,以及掺杂于水泥、砖瓦、路基填料等,增加这些材料的强度。

单分子磁体

单分子磁体是涉及合成化学、材料科学和凝聚态物理等边缘学科的一个新颖课题。本文对单分子磁体的主要性质、功能、研究方法和最新进展做了评述。重点介绍了含Mn和Fe这两类重要的单分子磁体。

拉伸载荷作用下中碳钢磁记忆信号的机理

测量了中碳钢试件表面各点的磁记忆信号,并观察断口的组织,研究了外载荷对磁记忆信号的影响和金属磁记忆的微观机理．结果表明:在弹性变形阶段内,随着载荷的增加中碳钢试件表面各点磁信号值由初始无规律分布逐渐向磁有序状态转变;进入塑性变形阶段后,位错对磁畴运动的钉扎使磁有序转变过程停止,磁信号几乎不再随载荷而变化．对于在弹性和塑性加载范围内卸载的两个试件,表面磁信号均具有不同程度的时效现象,试件的断口呈现韧窝及准解理混合断裂形式．

单分子磁体及其磁学表征

单分子磁体是介于分子基磁体和纳米磁性材料的学科交叉点。对其不同寻常磁特性的研究不仅有助于纳米磁性离子物理学和化学的发展 ,而且有望最终用于高密度信息储存设备。本文就单分子磁体的研究背景和意义、单分子磁体的种类、结构及磁学表征作一概述。

异步起动稀土永磁同步电机电抗参数准确计算

采用修正软磁材料相对磁导率μr的二维有限元法来计算异步起动永磁同步电机的交直轴同步电抗.该方法综合考虑了交直轴电枢反应共磁路的问题以及永磁体励磁的饱和影响问题.通过对电抗参数的精确计算,达到对该种电机准确进行电磁设计的目的.同时亦可较为准确地进行起动设计.而缩短设计周期.本文最后通过测功机稳态实验并结合磁路计算结果,验证了该种方法的准确性.

高精度空间磁通门磁力计

基于软磁材料磁化饱和时的非线性特性研制了空间磁通门磁力计,用以精确测量大小为1 mT以下的稳定或者低频交变的磁场,其应用范围涉及深空探测和地球物理学等许多领域.磁通门磁力计信号处理系统应用了相关检测原理,完成了一维空间磁通门磁力计原理样机研制.对样机进行了灵敏度、线性度、噪声和分辨率的测试.实验结果表明,该原理样机的分辨率优于5.2 nT,线性动态范围达到12μT.其关键指标达到空间应用的要求.

基于分子印迹磁性复合材料的基质分散-固相萃取/液相色谱法测定海水中的氯酚类污染物

建立了一种快速、高效、灵敏的基质分散-磁性固相萃取/液相色谱（d MSPE-HPLC）方法,用于海水中5种氯酚类（CPs）污染物残留量的测定。样品用五氯酚分子印迹氨基功能化磁性复合材料富集,在C8反相液相色谱柱（250 mm×4.6 mm×5.0μm）上分离,以甲醇-5 mmol/L乙酸铵水溶液（体积比70∶30）为流动相,230 nm处检测。考察了样品p H值、萃取时间和洗脱剂的种类与用量对CPs富集回收率的影响。结果表明,在最佳实验条件下,5种CPs在1~5 000 ng/L浓度范围内呈良好的线性关系,相关系数（r2）均大于0.998 9;平均回收率为86.5%~98.8%,相对标准偏差（RSDs）为0.8%~8.6%;检出限（LODs）为0.18~1.20 ng/L,定量下限（LOQs）为0.6~4.0 ng/L。方法可用于海水中CPs类化合物的快速筛查和确证分析。