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1.
《Ceramics International》2022,48(3):3059-3069
In this work, an ultralight nanocomposite of graphene oxide aerogels as a matrix and nickel-zinc ferrite (Ni0.7Zn0.3Fe2O4) nanoparticles as a second phase for the absorption of electromagnetic waves in the frequency of 1–18 GHz were fabricated by the hydrothermal - freeze-drying method. α-Al2O3 nanoparticles were used for further impedance matching for applications in electromagnetic wave absorption. XRD, SEM, EDS, and VNA analyses were used to characterize the sample. The effects of the amount of Ni0.7Zn0.3Fe2O4 (NZF) nanoparticles (GO: NZF volume percent ratio = 5:1 and 2:1) on the absorption of electromagnetic waves were investigated.  相似文献   
2.
Rare earths(REs) play a key role in distorting spinel structure by creating some defects at the lattice sites and make them suitable for magnetodielectric applications.In the present study,the nanoferrites of CuRE_(0.02)Fe_(1.98)O_4,where REs=Y~(3+),Yb~(3+),Gd~(3+),were prepared using one step sol-gel method.The prepared samples are copper ferrite(CFO),yttrium doped copper ferrite(Y-CFO),ytterbium doped copper ferrite(Yb-CFO) and gadolinium doped copper ferrite(Gd-CFO),respectively.The single-phase structure of all the REs doped nanoferrites was determined by X-ray diffraction(XRD) analysis.The porosity,agglomerations and grain size of the REs doped copper ferrite were examined using field emission scanning electron microscopy(FESEM) analysis.Fourier transform infrared spectroscopy(FTIR)elaborates the phase formation and environmental effects on the REs doped nanoparticles(NPs).The recorded room temperature M-H loops from a vibrating sample magnetometer(VSM) elucidate the magnetic properties of the REs doped spinel nanoferrites.The magnetic saturation(M_s) was calculated in the range of 23.08 to 51.78 emu/g.The calculated coercivity values(272.6 to 705.60 Oe) confirm the soft magnetic behavior of REs doped copper ferrites.Furthermore,the electromagnetic and dielectric properties were assessed using a Vector network analyzer(VNA) from 1 to 6 GHz.The permeability,permittivity,dielectric tangent loss and electric modulus of the REs doped spinel ferrites illustrate that the prepared NPs may be suitable for microwave and high frequency applications.  相似文献   
3.
《Ceramics International》2022,48(20):29561-29571
Currently, materials with outstanding absorption abilities, such as thin size, better absorbing power, and light weight are the need of industry to resolve the electromagnetic issues. However, the research on optimizing the composition of the material, microstructure and the structure of the absorber are also the important factors for enhancing the absorption features. A metamaterial microwave absorber (MMA) based on nano ferrites with desirable absorption peaks is proposed and simulated. Sol-gel auto combustion route is used to prepare the nanosized Sm doped Co ferrite with Co1+xSmxFe2-2xO4 at x = 0.00, 0.03, 0.06, 0.09, respectively. XRD, VSM, FESEM, and VNA were employed to evaluate the structural, magnetic, morphological, and dielectric features. Rietveld refinement of the XRD patterns of samples was evaluated. Refined parameters show the spinel phase's emergence and the Fe2O3 phase. Grain size and crystallite size were increased with Sm doping in Co ferrite. Electromagnetic studies depicted that the highest dielectric constant value was found at x = 0.09 and the minimum value at x = 0.03, respectively. Sm doped Co ferrite at x = 0.09 depicted high Q values at higher frequencies. The coercivity values first decreased and then increased. All samples exhibit variations in coercivity and magneto-crystalline anisotropy constant. This variation was attributed to the super-exchange interactions and strong LS coupling of the cations. The multiple absorption peaks are attained for TE-polarization, and the absorptivity is considerably improved for x = 0.09. The proposed absorber simulated from CST depicted the absorption peaks of the S-band and C-band of the microwave regime. The synergistic effects among the metamaterial and ferrite layers may enhance the absorption feature and would be useful for satellite communication applications.  相似文献   
4.
如何实现非同轴微波器件S参数的精确测量一直是业界的技术难题,制作、使用微波夹具是实现其网络参数直接测量的主要途径之一。文章介绍了传统夹具测试方法,重点论述了运用TRL校准技术进行夹具测量的解决方案,并给出夹具TRL校准件设计方法和注意事项。通过具体夹具校准件的设计和测量试验完成了设计验证,该技术方案能够很好地去除夹具误差、显著提高测试精度, 并具有较强的可操作性。  相似文献   
5.
信号完整性是高速PCB的核心参数之一,材料是影响高速PCB信号完整性的主要因素。从信号完整性的检测原理出发,对矢量网络分析仪在高速PCB材料评估中的应用进行了介绍。  相似文献   
6.
介绍基于矢量网络分析仪对变频器件的群时延进行测量的方法,以RS公司生产的ZVA和Agilent公司生产的PNA矢量网络分析仪为代表,分别对外接本振变频器件和嵌入式本振变频器件的群时延测量原理进行了阐述,可根据不同的测试需求选择有效的测试方法。  相似文献   
7.
矢量网络分析仪主要用于射频微波器件的驻波、衰减等参数的测试.传统的失量网络分析仪通过人工操作记录,测试结果不能编辑,使得测试不灵活,效率低.文中设计了基于GPIB中断请求的数据获取模式,通过主控计算机处理GPIB中断请求,完成对多台矢量网络分析仪的控制,自动处理记录响应,存储记录文件,多台计算机通过网络共享记录,可对记录结果编辑,修改.提高了批量射频器件的测试效率,同时可根据用户需求生成自定义测试记录.系统已通过长期使用,结果表明系统稳定可靠,请求响应处理准确率达99%以上.  相似文献   
8.
The presence of multiple microcracks in a structural component causes material degradation such as reduction in the stiffness or reduction in the fracture toughness of the component. In this paper, the homogenization method is used to evaluate mechanical properties of the damaged material. The adaptation of the superposition method to the homogenization method is also presented. The proposed method makes use of the finite element solution of uncracked solid and the analytical solution. The effective elastic moduli of damaged materials containing lattice-distribution microcracks are estimated by the proposed method. Furthermore, the stress fields and the stress intensity factors of the elliptical microcracks in the damaged material at a micro-mechanics scale are evaluated to illustrate microscopic behavior such as crack interaction.  相似文献   
9.
矢量网络分析仪时域功能分析   总被引:2,自引:1,他引:1  
矢量网络分析仪采用时频变换及时域选通方法来获得待测器件真实的频率响应。文中给出上述方法理论依据和实现步骤,介绍了不同窗函数对变换结果的影响和基于Chirp-Z变换的时域测量算法,推导出时域选通门的数学表达式,解释了理论结果出现失真的原因。并采用Visual Basic结合Measurement Studio语言编写相关软件实现时域测量功能,最后给出实际测量和变换结果,对结果进行分析后提出下一步的工作方向。  相似文献   
10.
黄凯冬  尹仲琪  胡勇 《电讯技术》2007,47(1):193-195
解释了无线射频系统时延指标测量的意义及重要性,介绍了使用矢量网络分析仪进行时延指标测量的基本原理,归纳了网络分析仪进行线性器件、变频器件时延测量的测量方法,重点分析了变频器件时延测量的三种方法的原理、步骤和准确度.  相似文献   
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