Microwave Absorbing Materials： Solutions for Real Functions under Ideal Conditions of Microwave Absorption

We present general equations for metal-substrate single-layer microwave absorbing materials. The optimum electromagnetic parameters and matching thicknesses for electric-loss, magnetic-loss, and electromagnetic-loss materials are given, and possible solutions for the equations and the corresponding theoretic curves are discussed as well. The results may be helpful for designing high-performance microwave absorbing materials.     

Effects of substitution of group-V atoms for carbon or silicon atoms on optical properties of silicon carbide nanotubes

Silicon carbide nanotubes (SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of SiCNTs where C atom or Si atom is replaced by group-V element is studied. The results show that the optical absorptions of SiCNTs doped by different elements are significantly different in the band of 600 nm-1500 nm. The differences in photoconductivity, caused by different doping elements, are reflected mainly in the band above 620 nm, the difference in dielectric function and refractive index of SiCNTs are reflected mainly in the band above 500 nm. Further analysis shows that SiCNTs doped with different elements change their band structures, resulting in the differences among their optical properties. The calculation of formation energy shows that SiCNTs are more stable when group-V element replaces Si atom, except N atom. These research results will be beneficial to the applications of SiC nanomaterials in optoelectronic devices and provide a theoretical basis for selecting the SiCNTs' dopants.     

Dielectric Response and Broadband Microwave Absorption Properties of Three-Layer Graded ZnO Nanowhisker/Polyester Composites

We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measured. Experimental results have shown that the graded dispersion with ZnO nanowhiskers contributes to broadband microwave absorption. In other words, the absorption band depends on the graded dispersion configuration of ZnO nanowhiskers in polyester matrix.     

化学气相法制备纳米级氮化铁超细粉末

采用化学气相法制备了纳米级氮化铁超细粉末，利用ＸＲＤ、ＴＥＭ、ＸＰＳ和ＶＳＭ测试了粉末的基本物性，初步表征了粉末的物相、形貌、粒度、成分及相应的磁性．实验结果表明，化学气相法可以制备出均匀、链状、超细的氮化铁粉末，并且该粉末的磁性指标优于γ－Ｆｅ２Ｏ３和田中隆夫的同类研究结果．     

激光三维加速度传感器的结构设计

目前的研究及工程场合对三维加速度的测量提出更高要求,针对于此提出了一种新型加速度光纤传感器的设计,它以弹性平膜片与角锥棱镜的组合作为敏感元件,利用二维角度激光测量及迈克尔逊干涉原理,可以在较高精度下同时提取并实时测量三维加速度信号.对该传感器进行了系统的理论研究,给出了该三维加速度传感器的结构设计、测量原理以及其参数和性能指标.这种新结构的激光加速度传感器,可望在较恶劣工作环境下的发动机故障检测,运动制导等领域中发挥重要作用.     

Orientation-dependent electromagnetic properties of basalt fibre/nickel core--shell heterostructures

The influence of orientation on electromagnetic properties of basalt fibre/nickel core--shell heterostructures prepared by a simple electroless plating method is investigated. For comparison, the same investigation is also performed on naked basalt fibres. For electromagnetic measurement, the directions of basalt fibre/nickel and naked basalt fibres are parallel, random and perpendicular to the direction of external electric field, termed E_\vert\vert sample, random sample and E_⊥ sample, respectively. Electromagnetic anisotropy can be clearly observed in the basalt fibre/nickel core--shell heterostructures, while electromagnetic properties of naked basalt fibres are unrelated to the orientation. The E_⊥ basalt fibre/nickel shows the highest dielectric loss but the lowest magnetic loss, and E_|| basalt fibre/nickel exhibits the highest magnetic loss but the lowest dielectric loss. The dielectric loss of E_⊥ basalt fibre/nickel is several times as large as that of E_|| basalt fibre/nickel, which could be attributed to the increase of polarization relaxation time as a consequence of the nanosize-confinement effect. The magnetic loss of E_|| basalt fibre/nickel is even one order of magnitude higher than that of E_⊥ basalt fibre/nickel, which originates mainly from the natural magnetic resonance of basalt fibre/nickel core--shell heterostructures.     

电磁波在损耗介质中的准驻波效应

讨论了正入射的电磁波在损耗介质界面上反射而形成准驻波的一般规律。     

多涂层吸波体的计算机智能化设计

介绍了用于均匀介质电磁波多层吸波体设计的一种智能化CAD系统。利用该系统，可以对入射波进行模拟跟踪计算，并采用单纯形法对计算结果进行自动优化，完成对多层吸波材料的优选、分层组配，也可以对现有材料进行理论预测。     

First Principle Study on Optical Properties of Tri-Group Doped(6,6) SiC Nanotubes

The optical properties of tri-group(B, Al, Ga, In) doped(6,6) SiC nanotubes(SiCNTs) are studied from first principles. The results show that the main absorption and dispersion of SiCNTs caused by the intrinsic transition appear in the ultraviolet-visible region(below 500 nm), and the tri-group doping increases the minimum dielectric constant value resulting in enhanced transmittance. In addition, the tri-group doping can introduce a weak absorption and dispersion region in the near-mid-infrared region, and the response peak blue shifts as the diameter of the doping atom increases. Comparative studies of reflectance, absorptivity, and transmittance show that the key factors affecting the transmittance of SiCNTs are reflectance(or refractive index) rather than absorption coefficient.