一次回火温度对烧结NdFeB永磁材料组织和性能的影响

探讨了880~900℃、910~930℃、940~960℃温度区间下1h回火处理对Nd30Dy3.5Al0.2B1合金显微组织和磁性能的影响。研究表明,温度低于910℃时,晶界富Nd带过厚且积聚,主相体积分数小,矫顽力、磁能积低;温度高于930℃时,晶粒尺寸过大,晶界面积变小,晶界富Nd带加厚,矫顽力、磁能积均下降;910~930℃时晶粒尺寸趋向均匀,晶界富Nd带呈薄层状分布,磁性能最佳。     

低温烧结Cu、Zn掺杂Co2-Y平面六角铁氧体及其频率特性

报道了通过BiO3的掺杂而获得的较低温度（870℃左右）下烧成的Y型平面六角结构软磁铁氧体的烧结工艺,结构特征及其磁导率和介电常数的频率特性,研究发现Cu,Zn掺杂的Co2Y型软磁铁氧体材料（Ba2Co1.2-xZnxCu0.8Fe12O22)在甚高频段具有良好的磁性能和介电性能,且此种材料烧结温度低,易于实现低温烧结,是一种可以用于甚高频段的理想的软磁材料。     

Growth-Temperature Dependence of Magnetic and Magneto-Transport Properties of Epitaxially Grown MnAs/GaAs Hybrid Multilayers

We successfully fabricated epitaxial MnAs/GaAs multilayers with a total thickness of 300 nm using molecular beam epitaxy. The periodicity of the samples was fixed at 5 nm/5 nm and the growth-temperature dependence of the magnetic and magneto-transport properties were studied. All samples studied exhibited ferromagnetism above room temperature. The magnetic anisotropy and magnetoresistance are strongly dependent on the growth temperature. These results indicate that it is possible to manipulate the magnetic and magneto-transport properties by changing the growth temperature.     

自蔓延高温合成Ni-Zn铁氧体的研究

采用SHS方法合成Ni0.35Zn0.65Fe2O4铁氧体 ,取代了传统铁氧体工艺耗能、耗时的预烧环节。以XRD、SEM、阻抗分析仪等对铁氧体的微观结构、磁性能进行表征,并与传统工艺对比,获得了性能优良的铁氧体。     

预烧温度对高导磁率MnZn铁氧体微结构和磁性能的影响

研究了预烧温度对高导MnZn铁氧体微结构和主要磁性能的影响,研究表明,由于预烧温度对粉体的活性产生很大影响,所以适宜的预烧温度是良好显微结构和高性能铁氧体的必要保证.适当降低预烧温度可以提高材料的磁导率,而提高预烧温度能够获得较好的频率特性.     

Electroless deposition of CoPtWP magnetic thin films

CoPtWP magnetic thin films were prepared by electroless deposition. The influence of bath pH, deposition temperature and bath composition on the deposition speed, alloy content, microstructure, and magnetic properties of CoPtWP thin films were investigated. It was found that deposition speed increased gradually with the bath pH and deposition temperature. The cobalt content in the CoPtWP thin films varied from 77 at.% to 85 at.% by controlling the bath pH. The microstructure of CoPtWP thin films was dependent on bath pH and deposition temperature: two mixed structures, face centered cubic (fcc) and hexagonal close packed (hcp), were observed at low pH values and low deposition temperature. With the increase of pH values and deposition temperature, the intensity of fcc (111) peak suppressed gradually. The surface morphology was markedly influenced by bath pH, deposition temperature and bath composition. VSM and MFM measurements revealed that perpendicular coercivity had been increased with the bath pH. Unique hard magnetic properties of CoPtWP thin films with large perpendicular magnetic anisotropy were obtained at 90 °C and bath pH 13.0.     

Fe-Si-Al复合磁粉芯制备工艺的研究

模压成型制备Fe-Si-Al复合磁粉芯,研究了热处理条件及绝缘包覆处理对复合磁粉芯磁性能的影响.实验结果表明:压制后的退火处理能够有效地提高Fe-Si-Al磁粉芯的磁性能;增加退火温度能够提高样品的有效磁导率,减少磁滞损耗;过高的退火温度(＞660℃) 能够恶化粒子间的绝缘层,降低磁特性;Fe-Si-Al磁粉芯的最佳退...     

电沉积软磁铁箔性能的研究

为优化电沉积制备软磁铁箔的工艺条件,研究电解液温度和阴极电流密度对铁箔的磁学、力学和电学性能的影响规律,采用软磁材料测试仪、直流电阻电桥和显微硬度计研究了工艺条件变化时对铁箔的磁参数、电阻率和显微硬度的影响,并对铁箔的金相显微组织进行分析.结果表明:阴极电流密度增大时,铁箔的矫顽力增大,最大磁导率降低,显微硬度值及电阻率均提高;电解液温度提高时,铁箔的矫顽力降低,最大磁导率增大,显微硬度值下降,而电阻率提高;在650℃经过真空退火后的铁箔矫顽力降低,最大磁导率提高,其电阻率和硬度都下降,韧性明显提高.电沉积工艺条件改变时,薄膜的晶粒尺寸影响铁箔性能的变化.     

Soft Magnetic Properties of Fe-5wt%Al Alloy

In this investigation, a new soft magnetic material (iron with 5 wt% aluminum) has been developed using powder metallurgy processing. The microstructure and the magnetic properties of this new P/M alloy have been characterized at both room and elevated temperatures (up to 500°C). The influence of post-sintering (after initial processing) on the porosity and magnetic properties of this material has also been examined.

Test results show that the room temperature soft magnetic properties of this alloy are comparable to other commercially available soft magnetic materials such as P/M pure Fe, Fe-Si, Fe-P, etc. Post-sintering at 1316°C resulted in significant grain growth and lower porosity with more rounded pore morphology and improved the magnetic properties. While the magnetic induction of the alloy was essentially constant from room temperature to 500°C, the coercivity of the material decreased significantly at elevated temperature. This new P/M alloy may be a suitable soft magnetic material for high temperature (up to 500°C) applications.     

基于磁流体独有特性的各种潜在传感器

详细分析磁流体所具有的磁通门原理、粘度智能性、液体流动性、可浸泡性、磁光效应等各种独有特性,探讨基于上述特性的潜在传感机理及应用方向,将上述特性单独或组合使用,将可以开发出各类新型磁流体传感器,具有用于倾斜、速度、加速度、体积、流量、非磁性体或磁流体密度、磁场以及磁流体磁化强度等传感的潜在可能性,对磁流体传感器研究具有指导意义.     

沉积厚度对L10-FePd颗粒膜结构和磁性能的影响

采用直流磁控溅射法在石英玻璃基片上制备不同厚度的FePd纳米颗粒膜,利用X射线衍射仪、X射线能谱仪、扫描电子显微镜、原子力显微镜和振动样品磁强计表征薄膜的结构和磁性能。结果表明,经过550℃热处理3h后,薄膜的X射线衍射谱中出现(002)超晶格衍射峰,表明薄膜中出现了四方有序结构。随着薄膜厚度的减小其有序化程度增加,在膜厚为47nm时,样品矫顽力达到3.5kOe,剩磁比达到0.94,最大磁能积((BH)_(max))达到17.6 MGOe。FePd薄膜的相转变温度降低,磁性能较好。     

粘结剂对粘结钕铁硼/锶铁氧体复合磁体磁性能的影响

为获得磁性能适中的磁体,采用流动温压成型技术制备了各向同性粘结Nd Fe B/锶铁氧体复合磁体.利用振动样品磁强计(VSM)研究了不同粘结剂对粘结Nd Fe B/锶铁氧体复合磁体磁性能的影响.研究表明:环氧值适中的酚醛环氧树脂制备的磁体具有较好的磁性能;当采用环氧值为0.480 mol/100 g酚醛环氧树脂BPANE8200H做粘结剂时,粘结Nd Fe B/锶铁氧体复合磁体获得了最佳的磁性能:Br=0.55 T,Hcj=620.6 k A/m,(BH)max=45.6 k J/m3.在保证磁体磁性能的前提下兼顾力学性能,粘结磁体流动温压成型温度参数的设置必须考虑粘结剂的软化点温度.     

Facile synthesis of nanocrystalline spinel NiFe2O4 via a novel soft chemistry route

A novel soft chemistry route (rheological phase reaction method) was developed to synthesize nanocrystalline NiFe₂O₄. The as-prepared samples were characterized by powder X-ray diffractometer (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The effects of the calcination temperature on the particle sizes and magnetic properties of the samples were investigated. The results indicated that the samples obtained by this method had the single-phase spinel. Particle sizes estimated from Scherrer's formula increased with the calcination temperature, which were consistent with the results of TEM. The magnetic properties of the samples were strongly affected by the calcination temperature. The coercivity initially increased and then decreased with increasing calcination temperature whereas the saturation magnetization continuously increased.     

Effect of rapid recurrent thermal annealing on the soft magnetic behaviour of Co85.5Nb8.9Zr5.6 nanocrystalline thin films

The rapid recurrent thermal annealing (RRTA) method has been used to crystallize-amorphous Co_85.5Nb_8.9Zr_5.6 soft magnetic thin films, which were fabricated by DC magnetron sputtering onto glass-ceramic substrates directly at room temperature. As a result, crystalline grains with diameter of about 10 nm were formed and a partiall nanocrystallization of the films was obtained. The soft magnetic properties of the Co-based nanocrystalline thin films were largely improved after RRTA. The resistivity is decreased by a quarter and the coercivity is also decreased. The magnetic and electrical properties were investigated using the RRTA method with varied parameters such as annealing temperature, annealing time and repeat cycle. The experimental results revealed that the RRTA is an effective method to control the magnetic and electrical properties of Co_85.5Nb_8.9Zr_5.6 thin films.     

Nickel and iron nano-particles in natural rubber composites

In this work, the mechanical, electrical, and magnetic properties of natural rubber (NR) composites containing iron or nickel nanoparticles at different percentage varying from 0 to 120 phr (part of magnetic particle per hundred rubber) have been investigated at room temperature. It was found that the optimum concentration of magnetic fillers in NR is 30 phr, which improve the rheometric characteristics and physico-mechanical properties. Magnetic properties of the rubber composites have been investigated using vibrating sample magnetometer (VSM) at room temperature. The magnetic measurements show superparamagnetic behavior for all Ni and Fe nanoparticles percentage. The electrical measurements show a strong dependency of the conductivity on the percentage of magnetic nanoparticles.     

High-density perpendicular magnetic recording media of granular-type (FePt/MgO)/soft underlayer

Perpendicular magnetic recording media, composed of granular-type FePt-MgO films on Fe-Ta-C soft magnetic underlayer (SUL), have been fabricated on to 2.5-in glass disks. [001] textured FePt granular films with high-perpendicular magnetic anisotropy were obtained by annealing the FePt/MgO multilayer films. The FePt grain size, perpendicular coercivity, magnetic activation volume, and the exchange coupling between the FePt grains were found to be strongly dependent on the initial multilayer structures and the annealing conditions. The recording performance of the disks was evaluated by a spin-stand. The obtained results reveal a close correlation between the recording performance and magnetic properties. The thermal stability of the granular-type FePt media was studied using high-temperature magnetic force microscopy (MFM) technique, equipped with in situ sample heating, in the temperature range 25/spl deg/C-200/spl deg/C. The estimated signal decay at high temperature is ascribed to the temperature dependent magnetic anisotropy behavior.     

Synthesis of nickel–rubber nanocomposites and evaluation of their dielectric properties

Nanocomposites based on natural rubber and nano-sized nickel were synthesized by incorporating nickel nanoparticles in a natural rubber matrix for various loadings of the filler. Structural, morphological, magnetic and mechanical properties of the composites were evaluated along with a detailed study of dielectric properties. It was found that nickel particles were uniformly distributed in the matrix without agglomeration resulting in a magnetic nanocomposite. The elastic properties showed an improvement with increase in filler content but breaking stress and breaking strain were found to decrease. Dielectric permittivity was found to decrease with increase in frequency, and found to increase with increase in nickel loading. The decrease in permittivity with temperature is attributed to the high volume expansivity of rubber at elevated temperatures. Dielectric loss of blank rubber as well as the composites was found to increase with temperature.     

诱导磁场对化学沉积Co-Ni-P薄膜磁性能的影响

采用化学湿法沉积技术制备了CoNiP磁性薄膜,研究了施镀过程中的诱导磁场对CoNiP薄膜磁性能和结构的影响。研究结果表明,随着施加诱导场强度的增加,CoNiP薄膜的矫顽力先增加,然后减小;当磁场强度为1300 Oe时,薄膜的矫顽力达到了751.7 Oe,比未施加磁场时提高了约28%。X射线衍射结果表明,Co-N-i P薄膜晶粒沿磁场方向生长,其c轴沿薄膜的轴向形成了很强的Co(002)织构。扫描电子显微镜表面形貌观察表明,随着磁场强度的增加,胞状颗粒逐渐增多,晶粒尺寸变小,颗粒之间结合紧密。诱导磁场对CoNiP薄膜的磁性能有良好的促进作用,这为进一步开发高性能的磁电传感器奠定了一定基础。     

Fe3B基纳米复合永磁材料的微结构和性能

利用差热(扫描)分析、X射线、透射电镜、振动样品磁强计研究了添加Co、Dy对Fe3B／Nd2Fe14B 纳米复合永磁材料的微结构和性能的影响．结果表明：添加适当的微量元素可以提高Nd4．5Fe77B18．5纳米复合永磁材料的内禀磁性，改进微结构，从而提高材料的永磁性能．在Nd4．5Fe77B18．5中添加1％-3％(原子分数)的Co、Dy明显地降低材料的晶化温度和最佳热处理温度、提高了2：14：1相的居里温度、改善了纳米复合永磁材料的微观结构，从而提高材料的永磁性能．与Nd4．5Fe77B18．5相比，Nd3．5Fe74Co3DylBl8.5的永磁性能为：Br=1.06T，jHc=328kA／m，(BH)max=108．9kJ／m^3，分别提高了26％，17％和104％．     

添加剂粒度细化对锶铁氧体结构和磁性能的影响

研究了添加剂粒度对锶铁氧体永磁材料结构和磁性能的影响.结果表明,添加剂粒度的细化使锶铁氧体的晶粒细化,提高了磁性相的取向度,改善了磁体的综合磁性能,特别是显著改善了剩磁和最大磁能积.添加剂粒度的细化使烧结温度对磁性能的影响更敏感,降低了最佳烧结温度,有利于实现低能耗下高性能产品的生产.