Cu及Mn掺杂NiZn铁氧体的合成及磁性能研究

利用溶胶-凝胶法制备尖晶石结构的Ni0.7-yZn0.3CuyFe2O4(y=0,0.1,0.2及0.3)。经微结构以及磁性能的研究发现,铜掺杂使样品在700℃时就形成了完全的尖晶石相,并且当铜掺入量为y=0.1时,样品的晶粒最大,最大值Ms达到66.7(A·m2)/kg。在此基础上,研究Mn掺杂对制备的样品(Ni0.6Zn0.3Cu0.1)1-xMnxFe2O4(x=0,0.01,0.02,0.03)的磁性能以及微观结构的影响。结果发现,铁氧体粉体的Ms随着Mn的增加基本保持不变;而环状样品的Bs,Br和Hc与锰含量以及烧结温度有着明显的变化关系,Bs和Br随着锰含量的增大先减小后增大,最小值分别达到Bs=305mT,Br=242mT。而矫顽力随锰含量的增大而增大。另外,Br与Bs都随着烧结温度的增大而增加,Hc减小。当烧结温度达到1050℃时,Hc,Bs和Br都趋于一个恒定的值。     

CeO2对Zn-Ni/CeO2复合镀层的影响

采用电沉积方法,通过向镀液中加入不同粒径的CeO2颗粒,制得Zn-Ni/微米CeO2复合镀层和Zn-Ni/纳米CeO2复合镀层,研究了CeO2粒子的大小和加入量对镀层微观形貌、相组成、CeO2在镀层中的复合量以及镀层耐蚀性的影响.结果表明:大量加入CeO2,可使镀层呈现块状的“饼干”结构,并能提高镀层的耐蚀性,此外还可以抑制Ni的沉积,加入10 g/L纳米CeO2时,镀层的合金相主要为Ni2Zn11相,其它Zn-Ni合金相则较少;相比之下,在提高镀层CeO2复合量方面,微米级CeO2效果较好,在提高镀层耐蚀性方面,纳米级CeO2的效果较好.     

Magnetic properties of tin-doped ferrites nanoparticles SnxFe3-xO4

Nanoparticles of tin-doped ferrites SnxFe3-xO4(x=0, 0.1, 0.2, 0.3, 0.4, 1.0) were prepared by the precipitation exchange method. The particles of all specimens are crystalline with mean diameter in the range of 4-8 nm, and the lattice parameters enlarge with increasing tin content. Magnetization and Mssbauer data indicate that the specimens are paramagnetic. The saturation magnetization decreases, as well as the magnetization and the coercive field increase, with increasing tin-content, the possible causes of which were discussed.     

一步合成法制备Al~(3+)掺杂Ni-Zn铁氧体的烧结制度研究

以分析纯Fe_2O_3、NiO、ZnO、Al_2O_3为原料,并适量配以烧结助剂,掺杂试剂、粘接剂和分散剂,磨细过筛后干压成陶瓷素坯,并一次烧结合成Ni-Zn铁氧体.研究了不同浓度Al3+掺杂Ni-Zn铁氧体的合成与烧结制度.发现Al~(3+)掺杂Ni-Zn铁氧体的合成和烧结具有很强的组成依赖性:随着掺杂Al3+浓度升高,铁氧体形成和烧结的温度升高;含锌铁氧体在相同掺杂Al~(3+)浓度下比纯镍铁氧体更容易烧结,且在更高温度下后者易形成新的非尖晶石相结构.随Al~(3+)掺杂浓度不同,Al~(3+)掺杂Ni-Zn铁氧体在1150～1550 ℃范围内可分别实现一次合成和烧结.     

MnO_2掺杂Ni-Zn铁氧体的微观结构及磁性能

为了改善Ni-Zn铁氧体材料的功率损耗特性,基于固相反应烧结法研究MnO2掺杂对Ni-Zn铁氧体综合性能的影响。研究发现,在0～2.0%（质量分数）掺杂范围内,MnO2不会影响铁氧体的单相结构。而Ni-Zn铁氧体的平均晶粒尺寸、烧结密度以及磁导率都随着MnO2掺杂量的增加而逐渐下降,同时,铁氧体的电阻率持续上升。饱和磁化强度（单位质量产生的磁矩）先随着0.4%MnO2的掺入略有上升,而后随着MnO2掺杂量的增加持续下降,这主要是受金属离子占位及超交换作用力变化的影响。当测试频率低于1MHz时,铁氧体的功耗（Pcv）随着MnO2掺杂量的增加持续上升,而当测试频率超过1MHz后,涡流损耗在总损耗中逐渐占主导地位,电阻率越高的样品越有利于获得低功耗,但这一规律对于2.0%MnO2掺杂的样品不适用。总体而言,当频率低于1MHz时,不掺杂MnO2的Ni-Zn铁氧样品能够获得更低的功耗;而当频率超过1MHz后,掺杂1.6%MnO2的Ni-Zn铁氧体能够获得最低的功耗。     

THE MAGNETIC PROPERTIES AND MOSSBAUER SPECTRA OF Y_2(Fe_(1-x)Ni_x)_(17)

实验发现,三元化合物Y_2(Fe_(1-x)Ni_x)_(17)的居里温度T_c随镍含量x变化,当x=0.3时,居里温度呈现极值,T_c=625K。为了研究镍原子部分地替代铁原子后对磁性的影响,取不同镍含量的样品,用X射线测定了易磁化方向,并在高于70千奥斯特的强磁场下,测量了饱和磁化强度随镍含量x的变化。为了研究镍原子在此种晶体中是否有序分布在特定位置上,观测和对比了Y_2Fe_(17)和Y_2(Fe_(0.9)Ni_(0.1))_(17)的穆斯保尔谱线。根据所得的实验结果,分析了居里温度随镍含量变化的原因。     

制备条件对NiZn铁氧体纳米晶材料磁性能的影响

利用溶胶-凝胶法制备尖晶石结构的Ni1-xZnxFe2O4铁氧体纳米粉体材料,同时系统研究Ni/Zn比、溶液pH值以及煅烧温度对制备的Ni1-xZnxFe2O4铁氧体纳米材料微结构及磁性能影响。结果表明,随着Ni含量的增加,生成物中未反应的氧化铁不断增多。当x=0.3时,NiZn铁氧体的饱和磁化强度(Ms)最大。但随着温度的增加,氧化铁的含量减少,NiZn铁氧体的生成量增加。同时发现溶液pH值对Ni0.7Zn0.3Fe2O4铁氧体微结构及性能影响较大,当溶液的pH=5时,Ni0.7Zn0.3Fe2O4纳米材料的Ms最大。实验得到了NiZn铁氧体的最佳制备条件:Ni/Zn比为0.7/0.3,溶液pH值为5,最佳烧结温度为900℃。     

STRUCTURAL AND MAGNETIC PROPERTIES OF Ho_2AlFe_(16x) Mn_xCOMPOUNDS

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Synthesis and characterization of MWCNTs/Co1−xZnxFe2O4 magnetic nanocomposites and their use in hydrogels

A novel magnetic nanocomposite of multiwalled carbon nanotubes (MWCNTs) decorated with Co_1−xZn_xFe₂O₄ nanocrystals was synthesized successfully by an effective solvothermal method. The as-prepared MWCNTs/Co_1−xZn_xFe₂O₄ magnetic nanocomposite was used for the functionalization of P/H hydrogels as a prototype of device to show the potential application of the nanocomposites. The nanocomposites were characterized by X-ray diffraction analysis, transmission electron microscopy and vibrating sample magnetometer. The results show that the saturation magnetization of the MWCNTs/Co_1−xZn_xFe₂O₄ magnetic nanocomposites increases with x when the Zn²⁺ content is less than 0.5, but decreases rapidly when the Zn²⁺ content is more than 0.5. The saturation magnetization as a function of Zn²⁺ substitution reaches a maximum value of 57.5 emu g⁻¹ for x = 0.5. The probable synthesis mechanism of these nanocomposites was described based on the experimental results.     

Ni_（50）Mn_（25＋x）Ga_（25-x）Tb_（0.5）（x=0,1.5,3,4.5,6）合金马氏体相变与磁性能

研究了Ni50Mn25＋xGa25-xTb0.5（x=0,1.5,3,4.5,6）磁性记忆合金马氏体相变行为、饱和磁化强度和磁感生应变。结果表明,随着Mn含量的增加、Ga含量的降低,合金的马氏体相变温度从202 K升高到416 K,饱和磁化强度从700 mT降低到400 mT,最大磁感生应变达到1870ppm。     

CuO掺杂Ni0.4Zn0.6Fe2O4铁氧体的组织与性能探讨

采用传统球磨法制备了Ni0.4-xCu_xZn0.6Fe₂O₄（x＝0,0.12,0.20,0.28）铁氧体,并通过扫描电镜（SEM）、X-ray衍射（XRD）、综合热分析（TG-DSC）和振动样品磁强计（VSM）等手段研究掺杂CuO对Ni-Zn铁氧体的显微组织、相组成和磁性能。结果表明,随着CuO含量的增加,第二相Ni-Cu-Zn相生成,且 Ni-Cu-Zn铁氧体衍射峰强度逐渐增强;从显微组织形貌和能谱可以看出,Cu ^2＋参与了铁氧体的反应,CuO含量增加得越多,样品烧结性能越好,并促使Ni-Cu-Zn铁氧体的晶化温度降低;磁滞回线显示了Ni0.4-xCu_xZn0.6Fe₂O₄（x＝0,0.12,0.20,0.28）铁氧体的软磁特性,CuO原子分数x为0.2时的铁氧体的饱和磁化强度（Ms）最高,且具有较低的矫顽力（Hc）。     

Effects of ferrites on magnetic transport properties in La2/3Sr1/3MnO3/ferrites composites

Effects of soft-magnetic MnZn ferrite (Mn0.5Zn0.5Fe2O4, MZF) and hard-magnetic Ba ferrite (BaO·6Fe2O3, BaM) on the structure and magnetic transport properties of [La2/3Sr1/3MnO3] (LSMO)/(x) [ferrites] (ferrites=MZF, BaM) composites have been investigated. It was found that the inclusion of MZF phase reduces magnetization and ferromagnetic-paramagnetic transition temperature (Tc) of the composites. With increasing the content of the dopants, the high-temperature magnetoresistance (MR) decreases, whereas low-...     

Effect of heat treatment on the magnetic properties of nanocrystalline spinel Li–Ni ferrite prepared by a simple soft chemistry route

A simple soft chemistry route was developed to synthesize nanocrystalline Li–Ni ferrite (Li_0.25Ni_0.5Fe_2.25O₄). The as-prepared ferrite samples were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The effects of the annealing temperature on the particle sizes and magnetic properties of the synthesized Li–Ni ferrites were investigated. The results indicated that the ferrite samples obtained by this method had the single-phase spinel structure. Particle sizes estimated from Scherrer's formula increased with the annealing temperature. The magnetic properties of the ferrite samples showed strong dependence on the annealing temperature. The coercivity initially increased and then decreased with increasing annealing temperature whereas the saturation magnetization continuously increased.     

Soft magnetic properties of (Ni50Fe50)SiO2 granular thin films for high frequency application

series of (Ni50Fe50)x(SiO2)(1-x) films with different volume fraction x was fabricated by magnetron co-sputtering technique. The microstructure, magnetic and electrical properties were investigated systematically by using X-ray diffraction, transmission electronic microscope, vibrating sample magnetometer and the traditional four point measurement method of resistivity. The results show that the samples consist of nano-scaled Ni50Fe50metallic particles with fcc structure uniformly embedded in amorphous insulating SiO2 matrix, and the particle size decreases with the decrease of x . The rapid change of coercivity with x is observed, and a minimum value 160 A·m-1 of Hc was obtained for the sample of x =0.83 with film thickness of 180 nm, which can be contributed to the exchange coupling between nano-scaled Ni50Fe50 particles. At the frequency lower than 1 GHz, the real part μ' of complex permeability keeps about 110 and the image part μ" is less than 15. Besides, this film exhibits high resistivity ρ=263 μΩ·cm, high saturation magnetization 4π Ms=1.25 T, high in-plane magnetic anisotropy field Hk=6.37 kA·m-1 , and the ferromagnetic resonance (FMR) frequency is estimated to be 2.8 GHz. Therefore, this film can be used in high frequency devices operating over 2 GHz.     

Ni45．4＋xMn41．5-xSn13．1（x=0，1．5，3．0）合金的结构和磁熵变研究

铁磁形状记忆合金Ni45.4-xMn41.5-xSn13.1（x=0,1．5,3．0）（分别定义为样品1、2、3）系列通过电弧熔炼法制备得到。在1173K下真空退火24h,自然冷却至室温。利用X射线衍射仪和振动样品磁强计研究了合金的结构、磁性和磁熵变。等温磁化曲线和Arrott曲线表明合金在马氏体转变温度附近合金为典型的亚磁性状态。在1．2T的外场下样品2和3在马氏体转变温度附近发生大的磁熵变大小分别为3．8和3．7J／kgK。样品1在磁性转变温度附近的磁熵变大小为2．24J／kg·K。     

Effect of manganese substitution on the magnetic properties of nickel-zinc ferrite

The effect of manganese (Mn)-ion substitution on the structural, magnetic, and electrical properties of nickel-zinc (Ni-Zn) ferrite of chemical formula Ni_0.6−t Mn _t Zn_0.4Fe₂O₄ (t=0.0, 0.1, 0.2, 0.3, 0.4, 0.45, 0.5, 0.55, 0.6) has been studied. It was found that Mn ion substitution increases the average grain diameter and improves the magnetization as well as the initial permeability. At the same time, the direct current (dc) resistivity at room temperature was found to increase with Mn ion substitution. The increase of both magnetization and dc resistivity due to the Mn substitution in a Ni-Zn ferrite is a promising result for applications in high-frequency fields.     

微波LTCC环行器用热压烧结SrFe12O19铁氧体的低温烧结特性

为了与低温共烧陶瓷（LTCC）技术兼容,本文采用热压烧结工艺在870 °C制备了添加不同Bi2O3含量的SrFe12O19铁氧体材料,着重研究了材料的晶相组成、烧结密度、气孔率和磁性能等低温烧结特性。研究结果表明,材料在870 °C烧结时,Bi2O3的添加促进了SrFe12O19晶相结构的形成,提高了材料的烧结致密度和磁性能。当Bi2O3的添加量为2～4 wt %,材料可以获得致密的结构,烧结密度达到4.65 g?cm-3以上,气孔率低于10%,材料的饱和磁化强度Ms和内禀矫顽力Hci较高,分别达到252.4 kA?m-1和312.9 kA?m-1以上。此外,基于SrFe12O19材料的低温烧结特性讨论了该材料在微波LTCC环行器当中的应用。     

MAGNETIC PROPERTIES OF Nd_2(Fe_(1-x)M_x)_(14)B(M=C,Si)ALLOYS

The magnetic properties of Nd_2(Fe_(1-x)M_x)_(14)B(M=C and Si) compounds have been investi-gated.Substituting Fe by small amount of metalloid C and Si atoms,the compounds are intetragonal structure and have uniaxial anisotropy.The substitution of C for part of Fe de-creases the Curie temperature of the compounds and the intrinsic coercivity of bond samples atlow temperature.The replacement of Fe by Si makes the Curie temperature increase with amaximum at the vicinity of x=0.15.When the range of the content of Si is 0≤x≤0.10,thecoercivity distinctly increases at room temperature.from 62.7 kA/m at x=0 to138.7kA/m at x=0.06,where the residual magnetization has a maximum:in the mean timethe saturation magnetization decreases only by a small amount.     

A new ferromagnetic shape memory alloy system

It is shown that the alloys Co₂Ni_1−xGa_1+x, x = 0.06, 0.09, 0.12, 0.15, are ferromagnetic shape memory alloys. In the as-solidified state their martensite start temperatures vary in the range 20 °C<T<60 °C as the concentration parameter x decreases. The high and low temperature phases are body centered cubic and orthorhombic and/or monoclinic, respectively, The transformation hysteresis, i.e. the difference between the martensite and austenite start temperatures, equals approximately 30 degrees. The saturation magnetization of the alloys resembles that of nickel while their coercive force is of the order of 100mT.     

Chemical synthesis of SmCo_5/Co magnetic nanocomposites

A three-step chemical synthesis of SmCo_5/Co nanocomposites was developed. Firstly, the Co-Sm(OH)_3-Ca(OH)_2 precursors were prepared by co-precipitation.Secondly, SmCo_5 particles were obtained by reductive annealing of the precursors. At last, the SmCo_5/Co nanocomposites were achieved by chemical deposition based on SmCo_5 particles. The SmCo_5/Co nanocomposites contain hard magnetic phase of SmCo_5 with about 100 nm in size and soft magnetic phase of Co with about 8 nm in size,exhibiting independent two-phase structure without alloying. Compared to that of single-phase SmCo_5 particles, the saturation magnetization of SmCo_5/Co nanocomposites is increased by 27.5%. The synthesis provides a new route to fabricate SmCo-based nanocomposites.