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1.
用原位乳液聚合法在碳纳米管表面包覆聚苯胺,制备出了碳纳米管/聚苯胺一维纳米复合管.复合管的直径为50—80 nm,聚苯胺包覆层的厚度为20—30 nm,聚苯胺在碳纳米管表面以层状和枝晶状两种形态生长.研究了碳纳米管/聚苯胺复合管在2—18 GHz的微波介电特性.与纯碳纳米管相比,碳纳米管/聚苯胺复合管的介电常数的实部ε′和虚部ε″在2—18 GHz随频率变化较小,在低频波段介电常数值较小,作为微波吸收剂容易实现与自由空间的阻抗匹配,而且它的介电损耗角正切(tanδ=ε″/ε′)较高,是一种很好的微波吸收剂.
关键词:
碳纳米管
聚苯胺
微波介电特性
微波吸收剂 相似文献
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在具有纳米级孔洞的多孔氧化铝模板上,用电沉积方法成功地制备出α-Fe纳米线有序阵列组装膜.分别用透射电子显微镜(TEM)、穆斯堡尔谱仪(MS)和振动样品磁强计(VMS)对样品进行了测试分析.TEM和电子衍射的结果显示,阵列中的纳米线均匀有序,彼此独立,由一串α-Fe单晶磁性颗粒构成.VSM测试结果表明,这种纳米阵列结构具有高度垂直磁各向异性.当外磁场垂直磁化时,磁滞回线具有很高矩形比(0.98)和矫顽力(1.76×105A/m).尤其MS的测试结果显示,阵列中的每根纳米线的总磁矩都沿
关键词: 相似文献
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用原子力显微镜(AFM)观测了不同张应力退火的Fe基纳米晶(Fe73.5Cu1Nb3Si13.5B9)薄带横断面的形貌,并结合X射线衍射(XRD)图谱对不同张应力退火的Fe基纳米晶薄带的介观结构进行分析;测量了不同张应力退火Fe基纳米晶薄带的纵向驱动巨磁阻抗(LDGMI)曲线及横向磁各向异性场;认为张应力退火Fe基纳米晶薄带感生横向磁各向异性场的介观结构机理,是由于外加张应力退火产生由非晶相包裹着的α-Fe(Si)纳米晶粒(包裹晶粒)的横向优势团聚.
关键词:
应力退火
介观结构
AFM
团聚 相似文献
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对可见光在酞菁钴(CoPc)薄膜中的折射率、吸收率和吸收系数作了理论计算。理论结果和文献[1]的实验测量值符合得很好。并对光在介质中吸收、色散随频率变化的理论公式作了深入的分析。 相似文献
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利用高压X射线衍射和高压原位电化学阻抗谱法研究了AlN纳米线的高压结构和电学性质.研究结果表明:AlN纳米线的电学参数均在22.6 GPa发生了突变,该突变与样品发生了从纤锌矿到岩盐矿的结构相变相关.岩盐相中晶格对电子的散射在电传导中起主导作用;不同于纤锌相中的长程传导,岩盐相中存在短程传导,且其作用随压力增加而增大;纤锌相的介电损耗峰在1Hz且不受压力影响;岩盐相的介电损耗峰随压力减小且向低频方向移动.本研究将为AlN及其相关材料的进一步研究和应用提供实验依据. 相似文献
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由于X射线吸收谱中的总电子产额(TEY)和荧光产额(FLY)具有不同的取样探测深度,分别对样品的表面和体内敏感,因而两者的综合应用为纳米材料的整体分析提供了有力的依据,是透射电子显微镜(TEM)、X射线衍射(XRD)等传统方法分析纳米材料时的补充。同时,通过对TEY和FLY记录的X射线吸收谱的评述,作者认为X射线吸收谱可以准确、可靠地用来进行纳米线和纳米管的生长及其机理、取向、化学键合、缺陷与螺旋性等方面的研究。因此X射线吸收谱具有传统方法无法比拟的优势,是纳米材料研究领域强有力的表征工具。 相似文献
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Amorphous Ni-P nanotubes are fabricated through electroless chemical deposition inside an anodic aluminum oxide template. The hysteresis loops of Ni-P nanotube arrays are each found to exhibit an unusual isotropic behaviour, which is believed to be due to the competition results between the shape anisotropy and the magnetostatic interaction among nanotubes. The dynamic dependence of permittivity on the frequency spectrum is fitted to the Lorentzian-type dispersion law. The permeability dispersion behaviours have been fitted based on the Kittel equation. Electromagnetic wave absorption properties of Ni-P nanotubes/paraffin composites with different values of thickness (t) are clearly shown by a three-dimensional graph. Furthermore, the bandwidths of composites with different "t" values can be well presented by a two-dimensional contour graph, which is a novel presentation form. The results show that the composites each have a good microwave absorption performance with t larger than 5.5 mm and with the frequency around 8 gigahertz. 相似文献
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Annealing effects on the microwave permittivity and permeability properties of Fe79Si16B5 microwires and their micowave absorption performances 下载免费PDF全文
This paper reports that amorphous magnetic microwires(Fe79Si16B5) have been fabricated by a melt-extraction technique and have been annealed at 600°C and 750°C respectively.Differential scanning calorimeter measurements show that nanocrystalline magnetic phase(α-Fe) has been formed in the amorphous matrix when it was annealed at 600°C.Hard magnetic phase(Fe2B) was formed in the microwires annealed at 750°C,which increases the magnetic coercivity.Microwave permittivity and permeability are found to be dependent on the microstructures.The permittivity fitting results show that multi Lorentzian dispersion processes exist.For microwires annealed at 750°C,their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600°C.The microwave absorption performance of microwires annealed at 600°C is found better than microwires annealed at 750°C. 相似文献
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The reflection properties of planar anisotropy Fe50Ni50 powder/paraffin composites have been studied in the microwave frequency range.The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by introducing the planar anisotropy,and can be further enhanced by using a rotational orientation method.The complex permeability can be considered as the superposition of two types of magnetic resonance.The resonance peak at high frequency is attributed to the natural resonance,while the peak at low frequency is attributed to the domain-wall resonance.The simulated results of the microwave reflectivity show that the matching thickness,peak frequency,permeability,and permittivity are closely related to the quarter wavelength matching condition.The Fe50Ni50 powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band(1-2 GHz). 相似文献
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根据强扰动理论,在长波长近似条件下推导出蜂窝结构吸波材料等效介电常数和等效磁导率的计算公式.电磁参数计算结果表明,蜂窝结构吸波材料等效介电常数和等效磁导率均小于吸收层的介电常数和磁导率,但等效介电常数的降幅更大,从而使等效介电常数更接近于等效磁导率,这正是吸波材料波阻抗匹配设计所需要的.反射率计算结果表明,不同的蜂窝高度,吸收层对应一最优厚度,使蜂窝结构吸波材料的反射率最低.这些结果对于蜂窝结构吸波材料设计具有一定的意义.
关键词:
蜂窝结构吸波材料
等效介电常数
等效磁导率
反射率 相似文献
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The reflection properties of planar anisotropy Fe50Ni50 powder/paraffin composites have been studied in the microwave frequency range. The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by introducing the planar anisotropy, and can be further enhanced by using a rotational orientation method. The complex permeability can be considered as the superposition of two types of magnetic resonance. The resonance peak at high frequency is attributed to the natural resonance, while the peak at low frequency is attributed to the domain-wall resonance. The simulated results of the microwave reflectivity show that the matching thickness, peak frequency, permeability, and permittivity are closely related to the quarter wavelength matching condition. The Fe50Ni50 powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band (1-2 GHz). 相似文献
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Sun Chang Sun Kangning Chui Pengfei 《Journal of magnetism and magnetic materials》2012,324(5):802-805
Ce-substituted barium ferrite with chemical composition BaCe0.05Fe11.95O19 has been prepared by the citrate sol-gel method. The phase composition of BaCe0.05Fe11.95O19 was characterized by X-ray powder diffraction analysis (XRD). The complex permittivity and complex permeability, microwave absorption properties of the resulting powder were measured by the transmission/reflection coaxial line method in the range of 8-13 GHz. The results show that the resulting powder has a minimum reflection loss value of - 37.4 dB at 12.8 GHz with a matching thickness of 3.5 mm. 相似文献
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Yasemin ?engün 《Physica A》2010,389(15):2945-2950
We have calculated local vibrational density of states (LDOS) of a center atom (CA) of a rectangular Cu nanowire with the axial orientation of 〈100〉, using a real space Green’s function approach with force constants extracted from interaction potentials based on the embedded atom method. The LDOS of a center atom of a strained nanowire is found to exhibit quite distinctive characteristics as compared to that of a strain-free nanowire, the most striking feature of which is the existence of high frequency modes above the bulk band even for small strain of 2.5%. We further find that these high frequency modes are shifted to even higher frequencies when the nanowire is exposed to an increasing axial strain. 相似文献
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Templated synthesis of highly ordered mesoporous cobalt ferrite and its microwave absorption properties 下载免费PDF全文
Based on the nanocasting strategy, highly ordered mesoporous CoFe2O4 is synthesized via the ‘two-solvent’ impregnation method using a mesoporous SBA-15 template. An ordered two-dimensional(P6mm) structure is preserved for the CoFe2O4/SBA-15 composite after the nanocasting. After the SBA-15 template is dissolved by NaOH solution, a mesoporous structure composed of aligned nanoparticles can be obtained, and the P6 mm structure of the parent SBA-15is preserved. With a high specific surface area(above 90 m2/g) and ferromagnetic behavior, the obtained material shows potential in light weight microwave absorption application. The minimum reflection loss(RL) can reach-18 dB at about16 GHz with a thickness of 2 mm and the corresponding absorption bandwidth is 4.5 GHz. 相似文献
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Microwave absorption properties of double-layer absorbers made of NiCoZn ferrites and hollow glass microspheres electroless plated with FeCoNiB 总被引:1,自引:0,他引:1
Amorphous FeCoNiB coatings were deposited by an electroless plating technique on the hollow glass microspheres. NiCoZn spinel ferrites sintered show two dispersion peaks (1.81 and 6.98 GHz). By fitting its permeability dispersion spectra, the one at low frequency is believed to be due to the domain wall movement mechanism, the other one is due to the spin rotation mechanism. Used in a single-layer absorber structure, neither the hollow glass microspheres coated nor the NiCoZn could meet the demand of light weight. However, if a double-layer absorber structure is used, not only the total weight of an absorber is reduced, but also the microwave absorption performance is enhanced. 相似文献