玻璃包覆铁基微丝的微波电磁特性

本文研究了玻璃包覆非晶微丝FeCoMnSiB在微波频段的电磁特性用x射线衍射技术分析了退火前微丝和不同温度退火后微丝的组织结构分析结果表明，铁基微丝在退火前的组织是由纳米晶和非晶混合组成的，经过465～550℃等温退火1h后，微丝内部组织和电磁特性都发生了改变．把退火前和经过不同温度退火处理过的微丝按一定配比分别散乱混合在石蜡基体里制成同轴样品，采用矢量网络分析仪测试微丝在2GHz到18GHz频段的复介电常数和复磁导率，同时模拟计算不同厚度单层吸波涂层的反射吸收率．由退火前微丝填充组成的涂层中，最小反射率可达一30dB；当微丝经过490℃等温退火后，不同厚度涂层的反射率曲线出现了不止一个吸收峰，而且有的曲线上的吸收峰同时都小于-10dB，吸波的频率范围变宽．结果表明，玻璃包覆铁基微丝可作为电磁损耗材料，具有良好的微波吸收特性．     

玻璃包覆铁基合金微丝的微结构与吸波性能

采用熔融纺丝工艺制备了玻璃包覆Fe基非晶合金微丝,通过X射线衍射分析研究了工艺条件对其微结构的影响,采用扫描电子显微镜分析了拉丝速度对微丝直径、玻璃包覆层厚度等结构参数和形貌的影响,利用微波矢量分析仪测量了2～18GHz的复磁导率和复介电常数,计算模拟了1mm厚度单层吸波材料的吸波性能.结果表明,通过冷却水急冷淬火可以获得非晶态结构,氩气保护可以防止合金氧化;拉丝速度提高有利于减小微丝直径,但玻璃包覆层的体积含量也随之增加;由该玻璃包覆Fe基非晶合金微丝设计的薄层吸波材料,在3～18GHz的宽频段内可以获得＜-2.5dB的微波吸收性能.     

微遗传算法优化多层ZnOw雷达吸波涂层

采用微遗传算法对以四针状ZnOw为主要成分的多层雷达吸波材料(RAM)进行优化设计.在给定最大厚度的情况下,在2～18GHz频率范围内,采用对不同频段给定不同吸收率的方案,对多层吸波涂层建立了快速优化设计方法.讨论了吸波涂层的厚度、层数对吸收效果的影响.此外,对于不同频段改变给定的吸收率,分析对于优化结果的影响.     

铁铬铝网栅吸波性能的研究

采用涂覆法制备了FeCrAl金属网栅吸波材料。研究了FeCrAl丝的不同丝长度、不同丝间距排布对2～18GHz范围内吸波性能的影响规律。研究表明,连续FeCrAl丝网栅材料不具备吸波性能;随FeCrAl丝长度的减小,材料最大吸收峰向高频方向移动,且最大吸收峰绝对值也随丝长度的减小而增大;随FeCrAl丝间距的减小,最大吸收峰向低频方向移动,且最大吸收峰绝对值也随丝间距的减小而增大。     

FeCo/石墨烯的制备和吸波性能

用共沉淀和高温退火相结合的方法制备了晶态FeCo/石墨烯吸波粒子,使用XRD、FESEM和TEM等手段对其晶体结构和微观形貌进行了表征。结果表明,向石蜡中添加不同质量的FeCo/石墨烯吸波粒子可制备不同含量吸波粒子的复合材料。使用微波矢量网络分析仪对不同含量吸波粒子的复合材料的电磁参数的测试和不同厚度吸波性能的模拟结果表明,吸波粒子含量为50%的材料,其吸波性能最优;厚度仅为1.6 mm的材料,有效吸收带宽为5.0 GHz(12.3~17.3 GHz)。吸波粒子优异的吸波性能,源于介电损耗和磁损耗的协同作用以及合适的阻抗匹配率和衰减常数。     

多壁碳纳米管复合材料在8 mm波段的吸波性能

将相同厚度不同碳纳米管含量, 以及不同厚度相同碳纳米管含量的多壁碳纳米管加入玻璃纤维增强复合材料中, 并研究了其在26. 5～40. 0 GHz 频段的吸波性能。结果发现, 多壁碳纳米管具有吸波性能, 而且吸波性能随着多壁碳纳米管含量的增加而提高。多壁碳纳米管/ 玻璃纤维/ 环氧树脂复合材料层板在26. 5～40. 0 GHz频段表现出较好的吸收效果, 其吸波性在于碳纳米管本身具有吸波性能, 此外还与吸波材料的谐振吸波原理有关。通过对该复合材料的电磁参数的测定并计算, 证明实验结果与吸波原理相符合。      

蚁群算法结合微遗传算法优化设计多层雷达吸波涂层

针对多层雷达吸波涂层的结构特点,提出蚁群算法结合微遗传算法的全新优化设计方案.在给定最大厚度的约束条件下,在2～18GHz频率范围内,采用对不同频段给定不同吸收率的方案,对多层雷达吸波涂层进行了优化设计.实验数据表明,该融合算法获得的解比微遗传算法更为精确.这种融合算法为求解类似的组合约束优化问题提供了一种新的方法.     

羰基铁/三元乙丙橡胶复合材料的吸波性能

为了探明吸波材料的厚度、吸收剂的含量与吸波性能之间的关系,以羰基铁为吸收剂、三元乙丙橡胶为基体制备了复合橡胶吸波材料,采用矢量网络分析仪研究了在2.6~18 GHz范围内羰基铁含量和吸波材料厚度对吸波性能的影响,并利用电磁理论分析了吸波材料的吸波性能.对于3 mm吸波材料,当羰基铁体积分数为45%时,在3.5 GHz处其反射率的最小值达-21.7 dB;在羰基铁含量一定的条件下,微波吸收性能与吸波材料的厚度并不成正比关系,当厚度<2 mm时,吸波材料的吸波效果较差;当厚度>2 mm时,随着吸波材料厚度的增加,最大吸收峰的位置向低频移动,并且最大吸收峰的峰值和指定反射率的频率带宽也呈减小的趋势.在相同厚度下,随着羰基铁含量的增加,吸波材料在电磁波吸收峰处的反射率不断减小,而且吸波材料吸收峰的位置也向低频移动;输入阻抗与空气阻抗越接近,吸波材料的吸波性能越好.     

二氧化锰涂覆EPS方法与效能分析

采用直接涂覆法将二氧化锰涂覆在EPS表面制成吸波球体。实验证实，这种方法有能力涂覆大密度导电粉末，且效果良好。在反射阻抗的测试中，当试样厚度为10mm时，其反射损耗在8～18GHz频率范围内为-7～-15dB，发现随着吸波颗粒中二氧化锰含量和试样厚度的增加，在8～18GHz频段内，试样的反射损耗增加。二氧化锰层吸波球体效能略低于同等导电层厚度的炭粉层吸波球体。     

吸波材料电磁参数频率跟踪逼近优化方法

首先介绍了单层吸波材料的吸波机理，然后提出了一种电磁参数频率跟踪逼近优化方法，并用该方法设计了单层吸波材料，得到了电磁参数的最佳配合下的吸波材料的幅频特征。分析讨论了电磁参数的频散效应对吸波材料的吸波性能的影响，得到了同时考虑电磁参数与频率和吸收剂厚度组合匹配是解决吸波材料优化的根本途径的结论。     

Measuring the impedance of magnetic microwires in a rectangular waveguide

A method of determining the impedance of magnetic microwires in the microwave frequency range is proposed that is based on the measurement of a complex coefficient of microwave reflection from a sample placed into a shorted rectangular waveguide. The proposed method has been applied to the investigation of the effect of an external constant magnetic field on the impedance of a cobalt-rich microwire.     

玻璃包覆金属微丝的快速凝固制备及应用

玻璃包覆金属微丝具有耐蚀、耐高温、抗辐照及高绝缘性等特点,作为精密电子元器件用电磁线,具有重要的应用前景.综述了玻璃包覆金属微丝制备技术的发展现状、基本工艺原理、主要工艺参数以及玻璃包覆金属微丝材料的种类、微丝的形状尺寸与组织,介绍了玻璃包覆金属微丝在电气、电子工业以及复合材料制备等领域的用途.     

玻璃包覆Co68Fe4.5Si13.5B14非晶微丝的力学性能

以玻璃包覆Co68Fe4.5Si13.5B14非晶微丝为研究对象,对经氢氟酸溶液腐蚀不同时间的微丝和不同直径的原丝进行了力学性能评价和断口形貌分析。结果表明,玻璃包覆非晶微丝的断裂过程是弹性变形。外径为28μm、内径为8.8μm的微丝经氢氟酸溶液腐蚀,刚去掉玻璃包覆层时裸丝的抗拉强度最大,可达到3545MPa,应变量为1.96%;若微丝经酸液腐蚀仍存在玻璃层,当腐蚀时间为40s时,抗拉强度和延伸率达到该阶段的最大值,分别为724MPa和1.3%;同时玻璃包覆Co68Fe4.5Si13.5B14非晶微丝具有尺寸效应,微丝的抗拉强度随直径的减小而增大。     

Synthesis of Au microwires by selective oxidation of Au–W thin-film composition spreads

Abstract

We report on the stress-induced growth of Au microwires out of a surrounding Au–W matrix by selective oxidation, in view of a possible application as ‘micro-Velcro’. The Au wires are extruded due to the high compressive stress in the tungsten oxide formed by oxidation of elemental W. The samples were fabricated as a thin-film materials library using combinatorial sputter deposition followed by thermal oxidation. Sizes and shapes of the Au microwires were investigated as a function of the W to Au ratio. The coherence length and stress state of the Au microwires were related to their shape and plastic deformation. Depending on the composition of the Au–W precursor, the oxidized samples showed regions with differently shaped Au microwires. The Au₄₈W₅₂ composition yielded wires with the maximum length to diameter ratio due to the high compressive stress in the tungsten oxide matrix. The values of wire length (35 μm) and diameter (2 μm) achieved at the Au₄₈W₅₂ composition are suitable for micro-Velcro applications.     

直径对玻璃包覆非晶合金微丝磁性的影响

采用Taylor-Ulitovsky方法制备了直径分别在6.3～28.0μm、20.2～28.0μm和14.0～35.2μm之间的玻璃包覆非晶态FeCuNbVSiB、FeBSiCMn和CoNiFeSiB微丝。通过X射线衍射、扫描电镜、振动样品磁强计分别测试了玻璃包覆微丝的组织结构、微观形貌和磁性,研究了不同成分玻璃包覆磁性合金微丝的玻璃包覆层厚度、合金芯直径对微丝磁性能的影响。结果表明了,玻璃包覆磁性合金微丝的磁性能的影响因素由大到小依次为：饱和磁致伸缩系数、微丝成分和微丝尺寸。轴向磁化时随着微丝直径及玻璃包覆层厚度的增大,3 种微丝的径向饱和场强度降低,FeCuNbVSiB和FeBSiCMn微丝的轴向矫顽力先分别由508 A/m和390 A/m降低到486 A/m和278 A/m后再升高到2570 A/m和342 A/m,CoNiFeSiB微丝的轴向矫顽力由171 A/m降低到63 A/m。     

不同直径玻璃包覆非晶微丝的制备及其磁性能

采用熔融拉丝法制备了直径范围分别在6.1～28.0μm和14.0～35.2μm之间的玻璃包覆非晶Fe基和Co基合金微丝, 测试了不同合金直径和不同玻璃包覆层厚度的玻璃包覆合金微丝样品的静磁性能. 结果表明: 轴向矫顽力和轴向剩磁比随着微丝直径的增大而降低, 随着玻璃包覆层的增大而升高; 径向剩磁比的变化趋势则相反. 微丝合金直径和玻璃包覆层厚度改变, 静磁性能变化的主要原因是作用在合金芯上的内应力的变化, 导致了具有不同磁畴结构的合金内芯区和合金外壳区体积比的改变.     

From Manipulation of Giant Magnetoimpedance in Thin Wires to Industrial Applications

We present results on our studies of soft magnetic properties and Giant magnetoimpedance, GMI, effect in thin microwires at elevated frequencies paying special attention to tailoring the GMI effect and achievement of high GMI effect with low hysteretic behavior. We measured magnetic field, H, dependence of real part, of the longitudinal wire impedance up to frequency, f, 4 GHz in Co-rich microwires. Amorphous microwires of appropriate composition exhibit extremely soft magnetic properties with low coercivity (generally below 10 A/m) with well defined magnetic anisotropy field, H _k . We report a number of interesting for sensor applications phenomena such as stress-impedance effect and stress sensibility of overall hysteresis loop shape. Field dependence of the off-diagonal voltage response of pulsed GMI effect in nearly-zero magnetostriction (λ _s≈?3×10^?7) microwires exhibits anti-symmetrical shape, suitable for industrial applications. We observed that the magnetic field dependence of GMI ratio can be tailored either controlling magnetoelastic anisotropy of as-prepared microwires or by heat treatment. Composite character of such microwires results in the appearance of additional magnetoelastic anisotropy. We found that if the surface anisotropy is not circumferential, then the magnetization, and consequently, the MI curve Z(H) present hysteresis. This hysteresis can be suppressed by application of sufficiently high DC bias current I _B that creates a circumferential bias field H _B.     

A study of the mechanical and fatigue properties of metallic microwires

There is an increasing necessity to record the deformation characteristics of microelements containing freestanding bond wires. The data required are either mechanical or thermal such as Young's moduli, stress–strain values, fatigue‐ and thermal‐strain data, but the nominal strength of a structure changes by scaling its size. Due to this size effect, material data cannot be taken from macrospecimens, thus special testing procedures were introduced. Laser optical sensors based on the speckle correlation technique were applied to determine non‐contacting strain values with high strain resolution. For the mechanical properties tensile tests were used. A special ultrasonic resonance fatigue system is described for testing freestanding microwires. In this study the stress–strain and fatigue response of microwires of Cu with a purity of 99.99+% with diameters between 10 and 125 μm with a typical bamboo structure have been investigated. A size dependence of the yield strength which increased with decreasing diameter was observed, while the fracture elongation showed contrary behaviour. Fatigue life also decreased with reduced diameters. An explanation is presented based on formed oxide layers, strengthening effects by dislocation pile‐ups and a pronounced localization of formed slip steps acting as notches being most dominant in the very thin microwires.