复合焦耳处理对Co68.15Fe4.35Si12.5B15非晶薄带巨磁阻抗效应的影响

本文研究了复合焦耳处理对Co68.15Fe4.35Si12.5B15非晶薄带巨磁阻抗效应的影响。实验结果表明：经前段电流密度10A／mm^2,后段电流密度30A／mm^2的复合焦耳处理后样品获得了最大的GMI效应。在8MHz的交变电流频率下,最大磁阻抗比为217％,灵敏度为114％／Oe,比淬态下的最大磁阻抗比和灵敏度均有明显提高。复合焦耳处理是提高材料GMI效应的一种新型的而且十分有效的方法。     

脉冲电流退火对Fe73.5Cu1Nb3Si13.5B9合金薄带巨应力阻抗效应的影响

研究了脉冲电流退火工艺对非晶Fe73.5Cu1Nb3Si13.5B9合金薄带巨应力阻抗（GSI）效应的影响。结果表明，在外加100MPa拉应力下对非晶合金进行脉冲电流退火后，巨应力阻抗效应显著提高，并且△Z／Z最大值随退火电流密度的增加而增加，当退火电流密度为930A／mm^2时，阻抗的最大相对变化达到350％。     

处理电流密度对钴基非晶薄带巨磁阻抗效应的影响

本文研究了焦耳处理工艺的处理电流密度对Co68.15Fe4.35Si12.5B15和Co71．8Fe4．9Nb0.8Si7．5B15非晶薄带巨磁阻抗效应的影响。样品在不同电流密度下进行了处理。实验结果表明：焦耳处理存在最佳电流密度,对Co68.15Fe4.35Si12.5B15窄带来说,最佳处理电流密度为30A／mm^2,处理后样品的阻抗变化率峰值和灵敏度分别为119％和73％／Oe;对Co71．8Fe4．9Nb0.8Si7．5B15窄带来说,最佳处理电流密度为35A／mm^2,处理后的阻抗变化率峰值为232％,灵敏度在30A／mm^2时达到42％／Oe。处理后样品的内应力得到有效释放,软磁性能提高,使薄带的巨磁阻抗效应较淬态时有了明显提高。处理电流密度是焦耳处理方法中影响钴基非晶薄带巨磁阻抗效应的一个重要参数。     

磁场退火对CoFeNiNbSiB薄带巨磁阻抗的影响

本文研究了磁场退火对CoFeNiNbSiB非晶薄带巨磁阻抗（GMI）效应的影响，样品在不同条件下进行了退火热处理，结果表明，在300℃下经横向磁场退火处理后获得了最佳的软磁特性，从而得到了最大的GMI效应，在800KHz的交变电流频率下，得到了236%的最大磁阻抗比，在低场下，材料的磁阻抗磁场灵敏度达到1152%/mT。     

矩形脉冲电流退火与激励电流对Co基非晶带巨磁阻抗效应的影响

利用矩形脉冲电流对Co_(66.3)Fe_(3.7)Si_(12)B_(18)非晶带进行退火处理,研究了退火电流密度对非晶带巨磁阻抗效应的影响,同时研究了激励电流频率对退火处理后的非晶带巨磁阻抗效应的影响。结果表明,该非晶带的特征频率为1.4 MHz。最大巨磁阻抗所对应的磁场随激励电流频率的增加逐渐向高磁场方向移动。     

Co-Fe-Ni-Nb-Si-B非晶软磁合金薄带巨磁阻抗效应

研究了Ｃｏ－Ｆｅ－Ｎｉ－Ｎｂ－Ｓｉ－Ｂ非晶软磁合金薄带的磁性和巨磁阻抗（ＧＭＩ）效应。样品在３５０℃下退火６０ｍｉｎ后获得了最佳的软磁特性,并表现出优良的ＧＭＩ效应。在１．４ＭＨｚ的交变电流频率下,获得了最大的ＧＭＩ效应,磁阻抗比ΔＺ／ＺＳ＝（Ｚ０－ＺＳ）／ＺＳ最高可达１９２％。在低频下得到了显著的巨磁电感效应,在１００ｋＨｚ下,磁电感比达到７６９％。在高频下,材料表现出优良的巨磁电阻效应,在１３     

Co67.5Fe4.5Ni3Si10B15非晶丝巨磁阻抗性能及其温度稳定性研究

研究了Co67.5Fe4.5Ni3Si10B15非晶丝巨磁阻抗性能及其温度特性。该非晶丝采用内圆水纺法制备,并在氮气保护下进行直流应力退火。在氮气中退火的非晶丝样品具有良好的表面光洁度以及较好的软磁性能和巨磁阻抗效应(GMI)。在激励功率6dBm、激励频率70MHz的测试条件下,磁阻抗变化率高达125%,巨磁阻抗最大灵敏度达3.92%/A·m-1。该非晶丝的巨磁阻抗性能在233～353K温度范围内具有优异的温度稳定性,为非晶丝应用于工业磁传感器等领域奠定了基础。     

低频脉冲电流退火对CoFeSiB非晶薄带巨磁阻抗效应的影响

研究了经不同低频脉冲电流密度退火的Co66.3Fe3．7Si12B18非晶薄带的巨磁阻抗（GMI）效应。结果表明，在低频脉冲电流下，巨磁阻抗效应的大小与退火电流密度密切相关。非晶带的GMI变化率△Z／Z先随退火电流密度的增加而增强，当电流密度为104A／mm^2时，△Z／Z达到最大值53．8％，此后随电流密度增大，GMI变化率开始减小。对脉冲电流退火影响巨磁阻抗效应的机制作了定性分析。并分析了由脉冲电流退火在材料内感生的横向各向异性场凤对GMI效应的影响，发现HK有利于提高GMI效应的峰值，但同时存在一个临界值，当超过这个值时，GMI效应的峰值减弱。     

FeSiB非晶薄带的磁阻抗效应

研究了频率、磁场强度、线圈匝数以及退火对Fe78Si9B13非晶薄带的磁阻抗效应的影响。结果表明:阻抗随频率的升高和线圈匝数的增多而增大,随磁场强度的增大而减小;阻抗变化幅度随频率的升高、磁场强度的增大和线圈匝数的增多而增大;退火可以提高阻抗及阻抗变化幅度。     

直流偏置电流对钴基非晶带环形磁芯巨磁阻抗效应的影响

将近零磁致伸缩系数的Co66.3Fe3.7Si12B18非晶薄带卷成环形后,在200Gs横磁场作用下,用密度为25A/mm2的脉冲电流退火30s,在穿过环形薄带圆心的直流电流产生的圆周磁场作用下的巨磁阻抗效应.激励电流频率f＞100kHz时,阻抗随圆周磁场的变化呈现对称双峰曲线;最大阻抗变化率（GMI）max随频率的升高而增大,当频率f=2MHz,幅值Ip=10mA时,（GMI）max=57%.直流偏置电流改变了非晶带横向磁导率,造成阻抗变化的不对称.偏置电流较小时,阻抗变化曲线的一边峰值得到加强,另一边峰值减弱;偏置电流较大时,两峰值都被削弱.阻抗变化的不对称性与激励电流的频率和直流偏置电流大小有紧密联系.     

Co71.8Fe4.9Nb0.8Si7.5B15玻璃包覆非晶丝巨磁阻抗效应研究

本文研究了直流焦耳处理对Co71.8Fe4.9Nb0.8Si7.5B15玻璃包覆非晶丝巨磁阻抗效应的影响.随着处理电流的增大,阻抗最大变化率随之增加,直到最佳处理条件为70mA,阻抗最大变化率为282%.处理电流值进一步提高,阻抗最大变化率下降.本文还研究了偏置电流对经过70mA直流焦耳处理的C021.8Fe4.9Nb0.8Si7.5B15玻璃包覆非晶丝巨磁阻抗效应的影响.随着偏置电流的增加,非对称性逐渐增强,直到偏置电流为2mA;当偏置电流继续增大时,非对称性逐渐减弱.     

Effect of glass removal on the GMI effect of Co71.8Fe4.9Nb0.8Si7.5B15 amorphous glass-covered wires

During the past several years, giant magneto-impedance effect (GMI) in amorphous wires has generated growing interest in the science community because of theirapplications in sensors. The giant magneto-impedance effect in Co71.8Fe4.9Nb0.8Si7.5B15 amorphous glass-covered wires (AGCW) consists of strong changes in the high frequency impedance with a small DC magnetic field. When f =1 MHz, there is no GMI effect due to the fact that the magnetic penetration depth is higher than their radius. As the frequency increases, the GMI effect becomes important in both the glass-covered wire and the wire afterglass removal. Field dependence of the impedance has a similar behaviour to the AGCW ones, when a tensile stress is applied to the wire without glass cover.     

Bulk soft magnetic materials from ball-milled Fe77Nb7B15Cu1 amorphous ribbons

The production of bulk amorphous and nanocrystalline samples with nominal composition Fe₇₇Nb₇B₁₅Cu₁ by compaction of ball milled amorphous melt-spun ribbons has been studied. The ribbons were pre-annealed at different temperatures, below and above the nanocrystallization onset. Powders were produced in a planetary mill, for various parameters such as the mass quantity in the vials, the ball-to-powder ratio and the milling time. Increased brittleness and coercivity reduction induced in the ribbons by pre-annealing treatment were examined. Hot-pressing consolidation has been used to obtain bulk materials. The influence of both compaction temperature and time on the magnetic properties of the compacted disks or toroids was also explored. The results indicate that the morphology of the powder is a key factor for the formation of bulk materials. Large particle size improves densification and magnetic softness. Post-annealing of bulk disks enhances the soft magnetic properties by reducing coercivity and enhancing saturation magnetization.     

脉冲电流处理对Fe73.5Cu1Nb3Si13.5B9非晶薄带晶化和显微硬度的影响

脉冲频率为50 Hz、电流密度为1750 A/mm2的高强脉冲电流使Fe73.5Cu1Nb3Si13.5B9非晶薄带在低于非晶转变温度100 K的条件下实现了短时晶化.脉冲电流能促进原子迁移,加速原子和原子团扩散,使Fe73.5Cu1Nb3Si13.5B9非晶薄带发生结构弛豫,使显微硬度由原始态非晶的8.2逐渐增至约9.0.进一步延长脉冲电流作用时间,非晶薄带发生显著晶化,大量析出平均尺寸约为8.5 nm的α-Fe(Si)相,其显微硬度则急剧增至12.4以上,增幅约达50%.在高强脉冲电流作用下,Fe73.5Cu1Nb3Si13.5B9非晶薄带可在约30 s的时间内基本完成纳米晶化过程,而等温退火晶化则需要约1 h.     

Effects of temperature and pH level on the corrosion behavior of amorphous Co69Fe4.5Nb1.5Si10B15 alloy

The corrosion behavior of the amorphous Co₆₉Fe_4.5Nb_1.5Si₁₀B₁₅ (at.%) alloy ribbon in H₂SO₄ solutions (0.001 M or 0.07 M), NaCl solution (0.07 M), and HCl + NaOH solution were examined as functions of solution temperature and pH. The corrosion potential decreased when either the temperature or pH of the solutions increased. The corrosion resistance of the Co₆₉Fe_4.5Nb_1.5Si₁₀B₁₅ alloy in the 0.07 M NaCl solution was higher than the 0.001 M or 0.07 M H₂SO₄ solutions for a given temperature. The corrosion rate increased exponentially with an increase in temperature and was inversely proportional to the pH in the range of 10^?6 A/cm²～10^?4 A/cm².     

退火工艺对Fe73.5Cu1Nb3Si13.5B9纳米晶带材耐腐蚀性能的影响

采用电化学方法研究了退火工艺对Fe73.5Cu1Nb3Si13.5B9纳米晶带材耐腐蚀性能的影响.用差热分析仪分析了该纳米晶带材的晶化过程,利用X射线衍射仪对经不同温度退火后的非晶带材的晶态结构进行了分析,并用恒电位法测试了样品在3.5%NaCl溶液中的耐腐蚀性能.结果表明,在3.5%NaCl溶液中,经过不同温度退火后的Fe73.5Cu1Nb3Si13.5B9纳米晶带材的耐腐蚀性能随退火温度的升高呈先增加后降低的趋势,其中530 ℃退火后的样品具有最好的耐蚀性.     

Magnetic properties of Fe75Si10B15 amorphous metallic wires

Effects of the temperature of a preliminary treatment, specimen length, and elastic tensile stresses on magnetic properties of amorphous metallic wires of composition Fe₇₅Si₁₀B₁₅ have been investigated. It has been revealed that the temperature of the pretreatment and the length of the wires have important influence on their magnetic properties. As the wire length decreases, a segment appears in the functional dependence of the differential magnetic permeability of the wire on the external magnetic field where the permeability remains constant, which indicates a change in the fundamental mechanism of magnetization of the wire. It has been shown that the behavior of the experimental functional dependence of the coercive force and differential permeability on applied tensile stresses may be explained in the context of the model of propagation of domain walls that separate oppositely magnetized domains in the core of the wire with allowance for the dissipative term.     

Fe4.5Co67.5Nb0.5Mn0.5Si12B15丝材中的巨磁阻抗效应

报道了淬火态Fe4.5Co67.5Nb0.5Mn0.5Si12B15丝中GMI效应,发现淬火态非晶丝GMI(Z)＝|(Z(65Oe)-Z(0))/Z(0)|可高达73%.我们也对简单退火下对Fe4.5Co67.5Nb0.5Mn0.5Si12B15钴基材料中GMI效应的影响也进行了深入细致的研究,发现GMI峰值随退火温度从300℃增加到450℃而先上升,达到一个最大值,然后下降.350℃退火的效果较佳.同时发现低于1MHz时,淬火态对应的GMI效应优于退火态的值,而高于1MHz时,350℃退火材料的GMI(Z)值相应的要高.     

Thermally induced crystallization of Fe73.5Cu1Nb3Si15.5B7 amorphous alloy

Thermally induced crystallization of Fe_73.5Cu₁Nb₃Si_15.5B₇ amorphous alloy occurs in two well-separated stages: the first, around 475 °C, corresponds to formation of α-Fe(Si)/Fe₃Si and Fe₂B phases from the amorphous matrix, while the second, around 625 °C, corresponds to formation of Fe₁₆Nb₆Si₇ and Fe₂Si phases out of the already formed α-Fe(Si)/Fe₃Si phase. Mössbauer spectroscopy suggests that the initial crystallization occurs through formation of several intermediate phases leading to the formation of stable α-Fe(Si)/Fe₃Si and Fe₂B phases, as well as formation of smaller amounts of Fe₁₆Nb₆Si₇ phase. X-ray diffraction (XRD) and electron microscopy suggest that the presence of Cu and Nb, as well as relatively high Si content in the as-prepared alloy causes inhibition of crystal growth at annealing temperatures below 625 °C, meaning that coalescence of smaller crystalline grains is the principal mechanism of crystal growth at higher annealing temperatures. The second stage of crystallization, at higher temperatures, is characterized by appearance of Fe₂Si phase and a significant increase in phase content of Fe₁₆Nb₆Si₇ phase. Kinetic and thermodynamic parameters for individual steps of crystallization suggest that the steps which occur in the same temperature region share some similarities in mechanism. This is further supported by investigation of dimensionality of crystal growth of individual phases, using both Matusita–Sakka method of analysis of DSC data and texture analysis using XRD data.