Stress tunable microwave absorption of ferromagnetic microwires for sensing applications

In the present work, we have studied the low field absorption (LFA) at 9 GHz of a set of Co-based glass-coated microwires in the presence of tensile stresses along the wire axis. The results reveal that the absorption profiles bear valve-like features associated with microwave magnetoimpedance effect. The stress applied along the wire axis compensates the reverse effect of magnetic field on absorption. The peak shown in the derivative LFA spectra becomes wider with increasing stress and moves to higher field, corresponding to the magnetization process. A larger ratio of metal to total diameter was found to be favorable to microwave absorption due to the smaller anisotropy and also gave rise to a larger magnetostriction constant. The influences of stress/magnetic field on the absorption as well as the shift of feature stress with wire geometry were discussed in the context of an effective microwire-based sensor design. Calculations of magnetostriction constant by the derived field dependence of anisotropy field were also performed to demonstrate the usefulness of stress tunable microwave absorption characteristics as a research tool.     

玻璃包覆纯铜微丝耐腐蚀性能及电学性能

制备硼硅酸盐玻璃包覆纯铜微丝,其主要尺寸范围为：铜丝直径4-30μm,玻璃包覆层厚度2-8μm;对微丝的耐腐蚀性能和电学性能进行评价。结果表明：玻璃包覆纯铜微丝在中性盐雾实验条件下,抗潮热盐雾腐蚀时间在240 h以上;对于外径25μm、包覆层厚度3.2μm和外径18μm、包覆层厚度2.5μm玻璃包覆纯铜微丝,平均击穿电压分别达到1 174 V和774 V,耐击穿电压分别在1 050 V和660 V以上;外径25μm、包覆层厚度3.2μm的玻璃包覆纯铜微丝抗软化击穿温度大于400℃。     

Theoretical and experimental investigation on giant magnetoresistive materials with amorphous ferromagnetic layer

Pseudo-spin-valve （PSV） sandwiches using amorphous CoNbZr alloy as soft magnetic layer were fabricated by magnetron sputtering. The giant magnetoresistance （GMR） and its dependence on the thickness of magnetic layer were investigated. Anti-parallel magnetization alignments were observed in the samples with very thin CoNbZr thickness （2-4 nm） and a maximum GMR ratio of 6.5% was obtained. The Camley-Barnas semiclassical model was extended for amorphous layer based ：nagnetic sandwiches by considering that the mixed layers exist between the ferromagnetic and nonmagnetic layer. The calculated results agree with the experimental results very well, indicating that the new model gives a more realistic picture of the physical processes that take place in the magnetic sandwiches. Moreover, the calculated results for amorphous sandwiches also clarify that the occurrence of maximum GMR at very small thickness of amorphous layer is ascribed to the short mean-flee-path in amorphous materials.     

固化剂对非晶纳米晶铁芯磁性能的影响

研究了固化剂对非晶纳米晶带材制作的铁芯磁性能的影响规律。结果表明,在不同粘度条件下,固化剂的热膨胀系数随温度的增加而增加,但存在两个转折点,这与其中发生的晶型转变有十分密切的关系;随着固化剂粘度增加,非晶铁芯和纳米晶铁芯的损耗变化率增加,磁导率变化率先增大后减小,这主要是由于在不同粘度下固化剂的膨胀系数不同导致铁芯内应力不同而引起铁芯磁性能的变化。本研究中,非晶和纳米晶铁芯在粘度为90 MPa·s时,损耗及磁导率变化值较低。     

FeCoNiSiB非晶合金感生各向异性对磁性能的影响

研究了恒温张力退火和横磁退火工艺对FeCoNiSiB非晶合金各向异性及磁性能的影响。结果表明,合金经恒温张力退火后表现出高直流偏置性能和高损耗的特点,而经横磁退火后具有优异的综合软磁性能,即具有高直流偏置能力的同时具有低损耗的特点。其中,恒温张力退火过程中提高退火温度时合金直流偏置能力增加,550 ℃下张力退火5 min的直流偏置场强度H_0.98为195 A/m,对应的损耗值P_cm为7255 W/kg;而经450 ℃横磁退火后,合金直流偏置场强度H_0.98可达374 A/m,对应的损耗值P_cm仅为200 W/kg。除此之外,经恒温张力退火和横磁退火后FeCoNiSiB非晶合金内部均形成180°条形磁畴结构,但其磁化矢量方向分别平行和垂直于磁化方向。     

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 研究了不同的磁场退火方式对非晶合金铁芯磁性能的影响。结果表明,纵向磁场退火后非晶合金铁芯的剩磁、最大磁导率和损耗增加;横向磁场处理后非晶合金铁芯的剩磁、最大磁导率、损耗和矫顽力减小;先加横向磁场后加纵向磁场退火,非晶合金铁芯可同时获得高的剩磁和低的损耗。     

等温热处理对(Fe_(0.58)Co_(0.42))_(73)Cr_(17)Zr_(10)非晶合金组织结构及磁性能的影响

采用单辊急冷法制备了(Fe0.58Co0.42)73Cr17Zr10非晶薄带,并对该合金进行等温退火。用XRD、AFM、VSM研究退火温度对(Fe0.58Co0.42)73Cr17Zr10非晶合金的组织结构和磁性能的影响。结果表明:该合金晶化析出过程为:Am→α-Fe(Co)+Am'→α-Fe(Co)+Cr Fe4+Fe3Ni2+Cr2Zr+未知相。500℃和610℃退火后薄带表面的AFM观察表明:AFM图片所呈现的颗粒尺寸要比用Scherrer法测得的α-Fe(Co)纳米晶尺寸大得多,这是典型的包裹晶粒现象。在低于晶化峰值温度(Tp)退火,由于铁磁性α-Fe(Co)相的析出,合金的饱和磁化强度Ms随退火温度的升高大幅上升;当退火温度高于Tp时,由于α-Fe(Co)相的粗化和析出相的析出和长大,Ms急剧下降,在635℃退火能获得最好磁性能,其Ms=126.2 emu/g。     

新型Fe80.5Si7.2B12.3非晶合金带材的退火工艺与磁性能

研究了新型Fe80.5Si7.2B12.3非晶合金带材在不同退火工艺下的磁性能及磁损耗特性,并与传统的铁基非晶合金Fe80Si9B11进行了对比.结果表明:新型Fe80.5Si7.2B12.3非晶合金带材比Fe80Si9B11具有更高的饱和磁感应强度,在励磁磁场强度为3500 A/m下其磁通密度值为1.607 T;在f...     

(Fe1-xCox)84Zr3.5Nb3.5B8Cu1非晶合金的高温和低温磁性

用磁天平（MB）及提拉样品磁强计（ESM）研究了（Fe1-xCox）84Zr3.5Nb3.5B8Cu1（x＝0－0．8）非晶合金高温与低温磁性的变化，结果表明，该非晶态合金加热到800－900℃后，除x＝0．8的合金外，，合金的室温饱和磁化强度均比淬态有所提高；X射线衍射的结果表明，x＝0，0．2，0．4，0．6的合金中析出单一的a-Fe（Co）相，x＝0．8的合金中析出Co3B，FeB相，当x＝1．0时合金中析出单一的fccCo相。该非晶合金在1．5K时的饱和磁化强度σs随Co含量的增加先增大，当x＝0．2时达到最大值，然后随着x的增大，合金的σs逐渐下降。     

In situ structural investigation of amorphous and nanocrystalline Fe40Co38Mo4B18 microwires

Thermal evolution of the structure of glass-coated nanocrystalline FeCoMoB microwire during its devitrification has been studied. It is shown that annealing at the temperature above 411 °C leads to the formation of crystalline α-FeCo grains with diameter ∼12 nm. Annealing at higher temperature increases the crystalline weight fraction up to 40% at 565 °C. However, crystalline grains size increases very weakly to ∼13 nm. The thermal expansion coefficient of nanocrystalline microwire decreases by one half comparing to that of the amorphous precursor.     

冷却速度对快淬Fe-Si-B-Cu合金结构和磁性能的影响

采用单辊旋淬法,以不同的轮辊转速(50、40、30和25 m/s)制备高Fe含量Fe_(82.65)Cu_(1.35)Si_2B_(14)非晶合金薄带,研究了冷却速度对快淬合金结构和性能的影响.结果表明:随冷却速度的降低,淬态Fe_(82.65)Cu_(1.35)Si_2B_(14)合金的条带厚度逐渐增大,合金由完全的非晶态结构转变为非晶与纳米晶的混合结构;同时,随冷却速度的降低,一次晶化温度下降,材料的饱和磁感应强度逐渐增加,在轮辊转速为25 m/s时,淬态合金的饱和磁感应强度达到1.4 T.     

Fe44Co20Nd7Nb4B25大块非晶合金磁性及热稳定性研究

采用铜模吸铸法制备了Fe44Co20Nd7Nb4B25大块非晶合金,利用差示扫描量热仪(DSC)、X射线衍射仪(XRD)、高分辨透射电镜(HRTEM)和振动样品磁强计(VSM)研究了该合金的结构、非晶形成能力、热稳定性及磁性能.结果表明:该合金为完全非晶结构,在室温下表现为良好的软磁性,并具有较好的非晶形成能力和热稳定性,晶化激活能Ep为642 kJ/mol.退火后该合金表现为硬磁性,退火温度为1003 K时,内禀矫顽力iHc达到最大值,为l164kA/m;退火温度为963 K时,剩余磁感应强度研和最大磁能积(BH)max的值最大,分别为0.27 T和15.79 kJ/m3.     

非晶颗粒增强纯铝基复合材料的组织与性能

采用机械合金化制备了Al70Ni17Ti13非晶粉末,在450℃下采用无压烧结-热压工艺烧结制备了铝基复合材料,研究了不同含量的非晶粉末的加入对纯铝基复合材料显微组织及力学性能的影响。结果表明:复合材料的硬度随着增强体含量的增加逐渐增加,但其抗拉强度随着增强体含量的增加呈现出先上升后下降的趋势。复合材料的显微硬度由纯铝的46 HV0.01提高到195.3 HV0.01,效果显著。当非晶粉末颗粒体积分数为10%时,抗拉强度达到最大值为196.6 MPa,相比纯铝抗拉强度性能提升了113%。当非晶粉末颗粒体积分数为15%时,复合材料的耐蚀性能最佳。     

Corrosion Resistance of FeSiB and FeCuNbSiB Alloys and Its Influence on Their Soft Magnetic Properties in NaOH Solution

非晶Fe78Si9B13和纳米晶Fe73.5Cu1Nb3Si13.5B9合金由于具有低矫顽力、高磁导率和高饱和磁通密度等特点而受到广泛关注。研究了Fe78Si9B13及Fe73.5Cu1Nb3Si13.5B9合金在NaOH(pH=9~10)溶液中的耐腐蚀性能,及其对软磁性能的影响。分析了经腐蚀后合金的有效磁导率、矫顽力和饱和磁感应强度等软磁性能的改变。样品用X射线衍射和3D高景深显微镜进行表征。结果显示:腐蚀后溶液中有橙色铁的氧化物产生,合金结构保持不变。经腐蚀后Fe78Si9B13及Fe73.5Cu1Nb3Si13.5B9合金的软磁性能下降,且Fe78Si9B13非晶合金的有效磁导率ue和饱和磁感应强度Bs比Fe73.5Cu1Nb3Si13.5B9纳米晶合金下降快。     

退火对非晶合金磁特性及铁心磁致振动的影响

为研究退火处理对非晶合金磁特性及非晶铁心振动的影响,采用磁特性测量设备对退火前非晶带材及退火后非晶铁心的磁化特性和磁致伸缩特性进行了测量,基于测量数据建立了非晶合金卷形铁心磁-机械多物理场耦合模型,计算得出退火前后两种状态铁心各处的磁通密度分布及振动情况,并与样机振动测量数据进行了比较。结果表明:退火可提高非晶合金饱和磁感应强度,改善磁导率,并可减小磁致伸缩系数,从而有效地抑制变压器铁心的振动。     

富铁Fe-Nd-Al系大块非晶合金的制备及其性能

利用普通的铜模铸造制备了一系列富Fe的Fe-Nd-Al块状非晶合金,采用X射线衍射仪、差示量热扫描仪、振动样品磁场仪和Instron万能材料试验机研究了Fe-Nd-Al块状非晶合金的热稳定性、室温磁性和力学性能。结果表明：Fe50Nd35Al15、Fe45Nd40Al15和Fe42.5Nd42.5Al15块状非晶合金的△Tm（△Tm=Tm-Tx）和晶化开始温度（Tx）与熔点（Tm）的比值分别为106、90和64K及0.88、0.90和0.93;其临界尺寸分别为1.5、3和4mm。此外,随Fe含量的减少,大块非晶的非晶形成能力和硬磁性能提高,但其力学性能有所下降。     

玻璃包覆FeSiBNbCu非晶丝的微波吸收性能(英文)

制备以石蜡为基体并具有玻璃包覆Fe73.5Si13.5B9Nb3Cu1非晶丝不同填充比的同轴介电样品,在相对较高的微波吸收频段(2~18 GHz)下研究短丝填充比(质量分数3%~9%)和样品厚度(1~7 mm)对同轴介电样品的微波吸收性能的影响规律。采用X射线衍射谱(XRD)、差示扫描量热分析(DSC)、扫描电子显微分析(SEM)和矢量网格分析仪(SNA)表征材料的微结构并评价其吸波性能。结果表明,不同填充比的同轴介电样品的复磁导率和复介电常数存在重要的频率范围(6~18 GHz)。模拟结果显示,具有3 mm厚度和7%填充比的样品具有较好的微波吸收性能,其反射率在14 GHz时达到峰值-34 dB。这对于开发具有更宽微波吸收范围应用的微丝介电材料是十分有益的。     

Influence of High-temperature Oxidation on Soft Magnetic Properties of Fe78Si9B13 Amorphous Alloy

研究了高温氧化对铁基非晶Fe78Si9B13合金软磁性能的影响。结果表明:非晶Fe78Si9B13合金带材经高温氧化处理后,在其表面形成了一层厚度约为10μm的高电阻率铁的氧化物层;Fe78Si9B13合金高温氧化磁化变得困难,且饱和磁感应强度Bs由氧化前的Bs=1.42~1.46 T下降到氧化后的Bs=1.29~1.38 T。同时,对非晶Fe78Si9B13合金带材经高温氧化处理后磁化困难的原因进行了讨论。     

交流磁场处理对Fe78Si9B13非晶合金结构和性能影响的研究

利用X射线衍射仪(XRD)、振动样品磁强计(VSM)和差示扫描量热仪(DSC)对交流磁场处理前后Fe78Si9B13非晶合金条带的结构和性能进行了分析研究。XRD和VSM结果显示,随着交流电流的增大,合金的近邻原子间距离(d)和矫顽力(Hc)先减小后增大,但饱和磁感应强度则随交变电流的增大而变化幅度不大。d和Hc的变化是由合金中不均匀特征结构在结构磁驰豫过程中的相互作用所导致。由DSC曲线计算获得的表观激活能、局域激活能和局域Avrami指数显示,交流磁场处理提高了合金的初始晶化激活能和晶化反应的Avrami指数,降低了晶化反应的表观生长激活能。合金晶化行为的改变与磁后效导致的团簇原子对有序以及溶质原子与自由体积的扩散有关。     

Mechanical properties and structure of zirconia-mullite ceramics prepared by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk

Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk, which were first treated at 900-1 000 ℃ for nucleation, then treated at higher temperature for crystallization to obtain ultra-fine zirconia-mullite composite ceramics. The effects of treating temperature and ZrO2 addition on mechanical properties and microstructure were analyzed. A unique structure in which there are a lot of near equiaxed t-ZrO2 grains and fine yield-cracks has been developed in the samples with 15% zirconia addition treated at 1 150 ℃. This specific microstructure is much more effective in toughening ceramics matrix and results in the best mechanical properties. The flexural strength and fracture toughness are 520 MPa and 5.13 MPa·m1/2, respectively. Either higher zirconia addition or higher crystallization temperature will produce large size rod-like ZrO2 and mullite grains, which are of negative effect on mechanical properties of this new composite ceramics.