驱动电流对复合结构丝GMI效应的影响

通过化学镀方法在直径为90μm的铜丝上制备了NiCoP/Cu复合结构丝,研究了驱动电流幅值和频率对复合丝的巨磁阻抗效应和磁场灵敏度的影响.研究发现驱动电流幅值增加时能显著增强复合丝巨磁阻抗效应和增加磁场灵敏度.电流大小和频率会改变GMI曲线峰值对应磁场Hp.结果可以用磁化过程和非线性效应来解释.     

玻璃包覆钴基非晶丝巨磁阻抗效应(英文)

本文讨论了长度对玻璃包覆钴基非晶丝巨磁阻抗效应的影响.通过测量不同频率下(0.1～1MHz)以及不同长度样品的巨磁阻抗效应,结果表明,长度对玻璃包覆钴基非晶丝巨磁阻抗效应有显著影响.通过计算样品的环向磁导率,发现样品的磁畴结构和饱和磁化后的退磁场影响着环向磁导率变化大小.没有加入恒定磁场时,特殊的磁畴结构决定了不同长度样品的环向磁导率近似相等.饱和磁化后,较长的样品的环向磁导率较小,其环向磁导率的变化较大,从而导致相应的巨磁阻抗效应增强.     

化学镀CoP/Insulator/BeCu复合结构丝的巨磁阻抗效应研究

采用含复合络合剂的碱性镀液,改变镀液配方组分和工艺条件在绝缘层上合成软磁性良好的CoP合金镀层,制备出CoP/Insulator/BeCu复合结构的巨磁阻抗效应材料.样品采用电流退火进行焦耳热处理.电流退火后,在较低频率下观察到显著的磁阻抗效应,在97kHz时最大磁阻抗效应为991%,磁场灵敏度高达2.78%/(A·m-1);在3kHz～30MHz的频率范围内,磁阻抗比率都在50%以上,具有很宽的频率应用范围.利用复数磁导率探讨材料的磁化特性,发现有效磁导率实部和虚部的频率特性在退火后发生了很大变化.     

BeCu/绝缘层/NiCoP复合结构丝巨磁阻抗效应的研究

利用化学镀方法制备了BeCu/绝缘层/NiCoP复合丝,对细丝在200℃进行热处理以改善铁磁层的磁性,并首次研究了巨磁阻抗效应.结果表明该复合丝在较低频率下有较大的巨磁阻抗效应,在1kHz时磁阻抗比为-3.32%,300kHz时磁阻抗比获得最大值108%.研究了样品退火前后的巨磁阻抗效应和镀层厚度对巨磁阻抗效应的影响.研究表明磁阻抗比不仅取决于△R/R和△X/X,还和R与X的比值相关.     

Co—Fe—Si—B非晶丝的巨磁阻抗效应研究

用旋转水中纺丝法制成几种不同直径的（Ｃｏ０．９４Ｆｅ０．０６）７２．５Ｓｉ１２．５Ｂ１５非晶丝,对丝进行张力退火后,测试了非晶丝热处理前后的磁阻抗性能。结果表明制成的非晶丝具有明显的巨磁阻抗效应,且巨磁阻抗效应随电流频率不同而表现出正磁阻抗和负磁阻抗两种规律。张力退火对正磁阻抗效应有明显改善,而且对直径小的试样,阻抗对轴向外磁场变化的灵敏度更高。实验得到的最大灵敏度为１２４％／Ｏｅ。     

化学镀带绝缘层LC共振型复合结构丝的巨磁阻抗效应

研究了LC共振型复合结构丝的巨磁阻抗效应并作了机理分析.用化学镀的方法制备了BeCu/绝缘层/NiCoP复合结构丝,由其自身构成串联LCR共振回路.该LC共振型复合结构丝的巨磁阻抗效应比一般型大幅度增加,长度为11cm的复合结构丝在频率f=24MHz时由一般型的54.7%增加到254.3%,增加了4.65倍.共振频率随复合结构丝长度的增加而减小.巨磁阻抗效应在共振频率附近迅速增强,而远离该频率则明显减小,具有很好的频率选择性.     

磁控溅射制备Cu/FeNi复合丝的巨磁阻抗效应

采用磁控溅射法制备了Cu/FeNi复合结构丝,并对其结构及巨磁阻抗(GMI)效应进行了研究.结果表明,Cu/FeNi复合结构丝具有良好的GMI效应,在较低频率下观察到的最大磁阻抗变化可达247.4%,同时发现FeNi铁磁层厚度对复合结构丝的软磁性能有重要影响,找到了复合结构丝铁磁层最佳厚度的范围,当厚度达到一定值时铁磁层内磁矩方向由环向分布转向复合丝长轴方向,表现出不同的GMI行为.     

高磷含量CoP-Cu复合丝巨磁阻抗效应的频谱特性

控制电化学工艺条件在直径为200μm的铜丝表面合成CoP磁性镀层成功地制备出高磷含量CoP—Cu复合丝巨磁阻抗效应材料。当磷含量为20%（原子分数）时,复合丝巨磁阻抗效应非常显著,达80%以上。本文详细研究了复合丝材料的频谱及巨磁阻抗效应频谱,指出复合丝巨磁阻抗具有较低的特征频率及较宽的频率使用范围与此新型结构有关,本文还发现,随频率的增加,最大负巨磁阻抗比对应的外加直流磁场也在增加,并且在高频与低频时,巨磁阻抗效应随磁场的响应曲线明显不同。     

溅射工艺对Cu/SiO_2/Ni_(80)Fe_(20)复合结构丝形貌及磁性能影响

利用射频磁控溅射方法在自旋的Cu上制备了Cu/SiO2和Cu/SiO2/Ni80Fe20两个系列复合结构丝。利用扫描电镜、阻抗分析仪分析了溅射SiO2时基底丝旋转速率对复合结构丝的表面微观结构和巨磁阻抗效应的影响。实验结果表明,镀层表面颗粒大小随着制备SiO2时转速的增加先减小后增大,Cu/SiO2/Ni80Fe20复合结构丝的巨磁阻抗效应则随着转速的增加先增大后减小。     

同轴电缆结构复合丝巨磁阻抗效应的研究

采用脉冲电沉积工艺在直径为200μm的铜丝表面沉积铁镍合金镀层,形成具有同轴电缆结构的巨磁阻抗复合丝材料。分别改变复合丝磁性外壳厚度与铜丝直径,研究复合丝结构对巨磁阻抗效应的影响。发现巨磁阻抗比值随磁性外壳厚度的增大及铜丝直径的增大而增大,特征频率则向低频端移动。本文还发现在外加直流磁场低于5．57kA／m时,驱动交流电幅值增大,巨磁阻抗效应增大;高于5．57kA／m时,驱动交流电幅值的大小几乎不再影响复合丝的巨磁阻抗效应。在驱动电流上叠加20mA以下的直流偏置对巨磁阻抗效应没有影响。     

Effects of thickness and heat treatments on giant magnetoimpedance of electrodeposited cobalt on silver wires

We studied the effects of thickness and heat treatments on giant magnetoimpedance (GMI) of cobalt-coated silver wires from 1 kHz to 100 MHz, under axial static magnetic field of 2 kOe. Cobalt, of thickness ranging from 1 to 25 /spl mu/m, was electro-deposited on 47.7-/spl mu/m-diameter silver wires. The frequency dependence of GMI varied with cobalt thickness with a maximum of 176% in 10-/spl mu/m-thick cobalt at the characteristic frequency 2 MHz. The characteristic frequency decreased with increasing thickness of cobalt layer but it was rather insensitive to dc Joule heating and conventional furnace annealing. However, both heat treatments led to magnetic hardening and decrease in GMI ratio. Joule heating also induced anisotropy in wire structures normally dominated by axial anisotropy.     

退火处理对含纳米陶瓷粉电弧喷涂层组织结构与高温冲蚀性能的影响

开发含纳米组分的粉芯丝材,采用超音速电弧喷涂技术获得复合涂层,对涂层进行退火处理,结合金相、硬度、X射线衍射、扫描电镜、透射电镜等分析方法对喷涂层的组织结构和高温冲蚀性能进行表征.结果表明:喷涂过程中粉芯丝材的表皮材料和芯粉材料能相互熔解和融合形成较均匀的固溶体;涂层中硬度分布较均匀;退火处理使涂层缺陷减少,应力消除,亚稳相分解,同时结晶度提高,从而显著提高涂层硬度;退火处理后涂层耐高温冲蚀性显著提高.     

低温应力退火Fe基合金薄带巨磁阻抗特性的研究

通过同步辐射X射线衍射技术,观测Fe73.5Cu1Nb3Si13.5B9非晶薄带经过不同温度和不同应力退火60 min后样品的微观结构,利用HP4294A型阻抗分析仪测量相应样品的巨磁阻抗比与磁各向异性。研究结果表明,在450℃下施加不同应力退火的样品仍然处于非晶结构状态,并且在应力为112.1 MPa的条件下产生优异的磁性能,样品的最大巨磁阻抗比达到了1818.7%,是自由退火条件下最大巨磁阻抗比的1.9倍,同时能够改变巨磁阻抗曲线的形状,使Fe基合金薄带的巨磁阻抗曲线具有宽线性的特性。对实验数据进行拟合后发现,样品的最大巨磁阻抗比和磁各向异性场与外加应力都具有线性关系,磁感灵敏度与外加应力具有负指数关系。通过探究发现具有非晶结构的Fe基合金薄带的磁学性能对应力敏感,可以作为研究非晶纳米晶合金材料应力敏感问题的另一个新方向。     

Magneto-Impedance Effect of Composite Wires Prepared by Chemical Plating under DC Current

Nano-Micro Letters - CuBe composite wires of 100 μm in diameter coated with a layer of NiCoP were prepared by a chemical plating method under DC current (CPUDC). The influences of DC current...     

A three-dimensional model describing stress-temperature induced solid phase transformations: thermomechanical coupling and hybrid composite applications

Between composite materials, shape memory alloy (SMA) composites are having a more and more relevant role. Typically, SMA wires are embedded in a metallic or a polymeric matrix to obtain materials with native multi-functionality and adaptive properties. This work approaches the computational study of the mechanical response of a composite in which SMA wires, previously deformed, are activated by electrical current heating, and accordingly try to recover the original shape inducing a shape change or a prestress in the structure. In particular, since the SMA behaviour is strongly affected by the thermo-mechanical coupling, in the first part of this work we present a 3D phenomenological model able to take into account this aspect. The model time-discrete counterpart is used to develop a 3D solid finite element able to describe the thermo-electro-mechanical coupled problem due to shape memory alloy response and to Joule effect. Finally, in the second part of the paper, we employ the developed computational tool to simulate different feasible SMA composite applications. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermomigration and electromigration in Sn8Zn3Bi solder joints

Individual effect of thermomigration (TM) and combined effect of TM and electromigration (EM) on the microstructural variation in Sn8Zn3Bi was investigated by stressing line-type Au/Ni–P/Cu-Sn8Zn3Bi-Au/Ni–P/Ni solder joints with a 5 × 10³ A/cm² alternating current (AC) or direct current (DC) at 110°C. Due to the different thermoelectric characteristics of Cu and Ni wires, a thermal gradient of 196°C/cm could be established across the solder joints according to the finite element simulation. In AC current stressing, there is no EM effect and only TM dominates the migration. Microstructural study shows that Zn atoms migrate towards the lower temperature side during TM. In DC current stressing, it is found that both EM and TM play important roles depending various experimental conditions. And the energy change during the EM and the TM is estimated to be ∆ω_em 3.2 × 10⁻²⁸ Joule and ∆ω_em 2.2 × 10⁻²⁸ Joule, respectively. Upon different current directions in DC current stressing, there is a counteractive or accelerated effect between TM and EM on Zn migration, resulting different microstructures at the cathode side in the solder joints.     

淬态FeNiCrSiB薄带的磁特性和纵向巨磁阻抗效应

采用单辊快淬法制备了(Fe50Ni50)77.5Cr0.5Si11B11合金薄带,测试了淬态薄带样品的微结构、静磁性能、磁导率和磁阻抗。研究结果表明,未经热处理的淬态(Fe50Ni50)77.5Cr0.5Si11B11合金薄带便具有良好的软磁性能和显著的巨磁阻抗效应,在7MHz频率下,纵向最大阻抗比达到31%。同时分析了几个典型频率下的纵向磁阻抗比、电阻比、电抗比和有效磁导率比随外磁场的变化行为,发现薄带样品的电抗比和有效磁导率比之间存在密切联系。由于内部结构的不均匀性,使得样品的横向各向异性场随驱动电流频率增大向高场方向移动。     

A simulation study on the thermal buckling behavior of laminated composite shells with embedded shape memory alloy (SMA) wires

In this paper, numerical simulation analyses of the thermal buckling behavior of laminated composite shells with embedded shape memory alloy (SMA) wires were performed to investigate the effect of embedded SMA wires on the characteristics of thermal buckling. In order to simulate the thermomechanical behavior of SMA wires, the constitutive equation of the SMA wires was formulated in the form of an ABAQUS user subroutine. The computational program was verified by showing the response of the pseudoelasticity and shape memory effect (SME) at various temperatures and stress levels. Modeling of the laminated composite shells with embedded SMA wires and thermal buckling analyses were performed with the use of the ABAQUS code linked with the subroutine of the formulated SMA constitutive equations. The thermal buckling analyses of the composite shells with embedded SMA wires show that the critical buckling temperature can be increased and the thermal buckling deformation can be decreased by using the activation force of embedded SMA wire actuators.