共查询到20条相似文献,搜索用时 109 毫秒
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为了研究电磁参数和涂层的厚度对单/双层吸波材料的吸收性能的影响,以期制备出具有良好的电磁匹配特征的吸波材料,利用通过单/双层吸波涂层内电磁波传播的理论机制,计算机模拟技术,分析了涂层厚度、电磁参数及频率变化对材料的电磁波吸收性能影响的规律.同时提出了双层吸波材料设计中厚度匹配和阻抗匹配等基本原则.结果显示,随着厚度的增加,吸波材料对电磁波的吸收峰向低频移动,并且相继出现多个吸收峰.当电磁匹配常数M=0.25时,涂层材料展现了很好的吸波性能.对于双层吸波材料,阻抗渐变原则和厚度匹配规律直接影响到其吸收性能. 相似文献
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利用对环境造成污染的废弃物粉煤灰中富铁空心微珠的电磁参数曲线设计了一种优化的球形堆积结构堆积吸波材料.电磁参数测试曲线表明,富铁空心微珠为一种介电性损耗材料.首先建立了球形不同堆积结构形成的吸波材料的模型并进行仿真,通过优化设计调整模型结构及其尺寸,获得混合半径的三层堆积结构为最优堆积结构,采用该堆积结构吸波材料的吸波效能在1~26GHz频段内最高为-9dB,且-5dB以上吸波效能的带宽为17GHz.将富铁空心微珠的电磁参数应用于该堆积结构中发现,采用富铁空心微珠制备球形颗粒时,该堆积结构的吸波材料厚度为6.5cm,吸波效能在1~18GHz频段内最高为-23dB,且-10dB以上吸波效能的带宽为14GHz. 相似文献
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提出多层吸波预浸料层和吸波阻尼层相互嵌合的结构,研发了一种兼具优良电磁吸波性能、高阻尼性能以及其他优良静力学和动力学性能的嵌入式共固化高阻尼电磁吸波复合材料,探索其制备工艺,推导了这种结构的电磁反射损失的理论表达式,并根据理论计算表达式编写Matlab程序理论分析了该结构的吸波性能。电磁吸波的实验结果,验证了该分析结果的有效性。模态实验、自由衰减实验和层间剪切实验结果给出了模态参数、阻尼性能以及层间剪切性能与阻尼层电磁吸波材料含量的关系。结果表明:随着试件电磁吸波材料含量的提高试件的反射损失变小,电磁吸收频宽增大,模态固有频率降低,模态阻尼比增加,阻尼损耗因子增加,层间剪切应力增强。 相似文献
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Jean‐François Semblat Luca Lenti Ali Gandomzadeh 《International journal for numerical methods in engineering》2011,85(12):1543-1563
The numerical analysis of elastic wave propagation in unbounded media may be difficult due to spurious waves reflected at the model artificial boundaries. This point is critical for the analysis of wave propagation in heterogeneous or layered solids. Various techniques such as Absorbing Boundary Conditions, infinite elements or Absorbing Boundary Layers (e.g. Perfectly Matched Layers) lead to an important reduction of such spurious reflections. In this paper, a simple absorbing layer method is proposed: it is based on a Rayleigh/Caughey damping formulation which is often already available in existing Finite Element softwares. The principle of the Caughey Absorbing Layer Method is first presented (including a rheological interpretation). The efficiency of the method is then shown through 1D Finite Element simulations considering homogeneous and heterogeneous damping in the absorbing layer. 2D models are considered afterwards to assess the efficiency of the absorbing layer method for various wave types and incidences. A comparison with the PML method is first performed for pure P‐waves and the method is shown to be reliable in a more complex 2D case involving various wave types and incidences. It may thus be used for various types of problems involving elastic waves (e.g. machine vibrations, seismic waves, etc.). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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以2种织物材料为基材,采用化学镀铜的方法,进行铜镀层和吸波涂层复合材料的试验研究。分析了铜镀层的成分结构、织物种类、叠层顺序等因素对复合材料在9. 35 GHz下反射率的影响规律,并探讨了铜镀层对吸波特性的影响机制。研究表明,对于织物基材先涂敷吸波涂层再化学镀铜的复合结构,与未氧化的铜镀层相比,空气中氧化8天的铜镀层使无纺布吸波复合材料的反射率峰值由 - 11 dB降低至 - 13. 2 dB。对于织物基材先化学镀铜再涂敷吸波涂层的复合结构,40℃ 镀铜与常温镀铜相比,在反射率曲线峰值接近的情况下,吸波材料总厚度下降了约 1. 4 mm,说明铜镀层可用于改进吸波材料的微波吸收效果。 相似文献
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SiC(N)/LAS吸波材料吸波性能研究 总被引:6,自引:2,他引:6
研究了由SiC(N)纳米吸收剂制备的SiC(N)/LAS吸波材料的介电性能,对影响介电性能的吸收剂的含量、吸波材料烧结温度和碳界面层等因素进行了较为全面的研究。结果表明,在1080℃以下烧结温度对陶瓷致密度的影响较大而对陶瓷介电常数的影响较小;在1080℃以上烧结温度对烧结致密度的影响较小,对陶瓷介电常数的影响较大,吸波材料介电常数的实测值与计算值之间存在很大的差异,这种差异是吸波材料制备过程中纳米级的SiC(N)促进了碳界面层形成,导致了在较高温度烧结时吸波材料介电常数对温度的敏感性,使吸波材料介电常数的实测值与计算值之间出现了很大的差异,形成的碳界面层复介电常数的虚部较高,使吸波材料对电磁波的损耗进一步升高,从而使吸波材料的吸波性能得到增强。 相似文献
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Puthucheri Smitha Isha Singh Mohd Najim Ravi Panwar Dharmendra Singh Vijaya Agarwala Ghanshyam Das Varma 《Journal of Materials Science: Materials in Electronics》2016,27(8):7731-7737
Stealth applications now emphasise on development of efficient Radar Absorbing Materials of light weight, less coating thickness, broad bandwidth of absorption along with cost effective raw materials and manufacturing techniques. Therefore, in this paper an attempt has been made to develop such an efficient cost effective radar absorbing material which possesses broad band absorption with less coating thickness. Unconventionality of acquiring impedance match for a double layer absorber of nanostructured nickel ferrite (NF) with reasonably good dielectric properties and its cation substituted counterpart, nickel zinc ferrite (NZF) with enhanced magnetic properties has been thoroughly investigated for radar wave absorption for very low coating thickness. Complex permittivity and permeability of NF and NZF with crystallite sizes of 10.0 and 16.0 nm, respectively, are measured and used as the data bases. The microwave absorption properties of the ferrites are correlated with their size, morphology, permittivity, permeability, thickness and bandwidth of absorption. Multilayering has been performed using the optimization through Genetic Algorithm in order to attain suitable impedance matching layer for minimum reflection loss (RL) at lower thickness. The results indicate an enhancement in the absorption with RL value of ?45.0 dB for a moderately low coating thickness of 1.72 mm. Single layers NF, NZF and multilayer NF–NZF are fabricated over the aluminium sheets and the results are experimentally verified. 相似文献
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吸收剂颗粒界面效应对电磁波吸收性能影响的理论研究 总被引:4,自引:0,他引:4
针对含夹杂颗粒的电磁吸波复合材料,探讨了颗粒界面对电磁波吸波性能的影响.首先给出了表征电磁波吸收层吸波性能的场强反射率及其功率反射率的计算公式,在此基础上结合颗粒夹杂复合吸波材料含界面效应的等效介电常数和等效磁导率的预测公式与电磁波吸波层的功率反射率的基本理论,给出了电磁波吸收层的功率反射率与颗粒尺寸,以及颗粒界面效应之间的关系.进而从数值角度展示了颗粒界面效应与电磁波吸收的最佳频率和电磁波吸收层厚度的影响,以及颗粒界面对电磁波功率反射率的尺度效应等.分析结果表明,当电磁波吸收剂的颗粒尺寸较小时,颗粒界面效应对电磁波功率反射率的影响是明显的. 相似文献
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Neeraj Gill Smitha Puthucheri Dharmendra Singh Vijaya Agarwala 《Journal of Materials Science: Materials in Electronics》2017,28(2):1259-1270
Radar wave absorbers are important for the reduction of radar cross section of the target for stealth applications. Earlier the radars were available in the frequency range 8–12 GHz (X-band) and 12–18 GHz (Ku-Band). Due to recent advancement in radar technology, radars are now available from 2 to 18 GHz frequency range. So there is an urgent need to develop such a material that can work as radar wave absorber in the lower frequency band of the microwave spectrum i.e., 2–8 GHz. For this purpose the selection of material is an important criterion as the radar wave absorption depends primarily upon the material characteristics i.e., complex permittivity and complex permeability. For lower frequency radar wave absorption, the material must also possess the conducting property along with dielectric and magnetic properties. Therefore, an attempt has been made to develop a radar wave absorbing nano-composite material by selecting constituent materials with such inherent properties that can work for the absorption of radar wave in the lower frequency range. It is observed that the developed composite give good absorption in the lower frequency range but with narrow radar wave absorption bandwidth (4–7 GHz). So we have explored the possibility of the efficient use of an advanced electromagnetic technique like frequency selective surface to enhance the radar wave absorption bandwidth in the lower frequency region of the microwave frequency spectrum and precaution has been taken such that complexity due to FSS can be avoided. It has been observed that the synthesised single layer absorber with single square loop, cross dipole and Jerusalem cross FSSs provides radar wave absorption bandwidth in the frequency range 2–8 GHz. 相似文献