排序方式: 共有92条查询结果,搜索用时 31 毫秒
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针对羰基铁粉吸收剂在温度较高时易被氧化的问题,采用水热法制备了氧化锌包覆羰基铁粉核壳结构复合粒子,并分别将羰基铁粉和氧化锌/羰基铁粉核壳粒子与石蜡混合,制备复合材料。结果表明,氧化锌纳米棒致密的包覆在羰基铁粉颗粒表面形成海胆状核壳结构复合粒子,正是这种结构将羰基铁粉颗粒与空气隔绝,使得复合粒子的抗氧化性能得到显著改善。与羰基铁粉复合吸波材料相比,氧化锌/羰基铁粉核壳粒子的复合材料吸收峰稍向低频移动,反射损耗小于-5 d B的带宽几乎保持不变,在不改变电磁吸波性能的前提下,提高了羰基铁粉粒子的使用温度。 相似文献
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通过将单回路镜像对称开口金属环结构印制在高介电常数基板上,实现了一种金属含量比传统负折射材料更少,"双负"通带比全介质负折射材料更宽的负折射材料.分析了高介电常数基板产生负介电常数以及"双负"通带形成的机理,通过仿真实验分析了影响"双负"通带的因素.通过制作样品验证了这一机理实现"双负"的可行性,理论分析与实验结果都表明这种方法可实现较宽频段内的"双负"通带.
关键词:
负折射材料
负介电常数
负磁导率
介质谐振器原理 相似文献
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Experimental Verification of Left-Handed Metamaterials Composed of Coplanar Electric and Magnetic Resonators 下载免费PDF全文
We verified experimentally left-handed metamaterials (LHM) composed of coplanar electric and magnetic resonators. A typical LHM sample composed of coplanar resonator unit cells was fabricated, investigated and tested. The experimental results show that the tested sample has a left-handed band of width 1.4 GHz in the X band. The experimental results agree quite well with the simulation ones. Moreover, both the simulation and experimental results show that the LHM under study can automatically achieve good impedance-matching in the left-handed band. 相似文献
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由于具有优异的压电性能,弛豫铁电单晶自上世纪90年代问世以来即成为了铁电压电领域研究的热点材料,并被认为是研发下一代高性能换能器、传感器等器件的重要压电材料。弛豫铁电单晶不但压电常数可达2500 pC/N,约为软性Pb(Zr,Ti)O3(PZT)陶瓷的5倍,而且其电致应变滞后也远小于软性PZT陶瓷。因此,弛豫铁电单晶高压电性能的产生机理一直是铁电压电领域的研究热点。本文主要介绍了弛豫铁电单晶材料在近些年的发展,从本征压电效应(晶格压电畸变)的角度归纳总结了弛豫铁电单晶高压电效应的产生机理,着重探讨了弛豫铁电单晶的重要特点—剪切压电效应。在本征效应的基础上,本文对弛豫铁电单晶压电效应与晶体组分、切向以及温度的关系进行了分析。需要指出的是,目前基于本征角度对弛豫铁电单晶高压电效应的分析仍处于定性的阶段,因而还不能完全排除一些可能导致弛豫铁电单晶高压电效应的非本征物理机制。 相似文献
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Based on the substrate integrated waveguide technology,we present a dual-band frequency selective surface(FSS) with a quasi-elliptic bandpass response.The characteristics of the quasi-elliptic bandpass response are realized by shunting two substrate integrated waveguide cavities of different sizes,with the same slots on both sides of the metal surfaces.Four cavities of different sizes and two slots of different sizes are used to design the novel FSS.Every bandpass response with sharp sidebands is induced by two transmission nulls that are generated by the coupling between the slot aperture resonance and the cavity resonance.The simulation results show that such dual-band FSS has the advantages of high selectivity and stable performance at different oblique incident angles.Moreover,it is easy to fabricate. 相似文献
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Effects of (LiCe) co-substitution on the structural and electrical properties of CaBi2Nb209 ceramics 下载免费PDF全文
The piezoelectric,dielectric,and ferroelectric properties of the(LiCe) co-substituted calcium bismuth niobate(CaBi2Nb2O9,CBNO) are investigated.The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tan δ decreased.This makes poling using(LiCe) co-substitution easier.The ceramics(where represents A-site Ca2+ vacancies,possess a pure layered structure phase and no other phases can be found.The Ca0.88(LiCe)0.04 0.04Bi2Nb2O9 ceramics possess optimal piezoelectric properties,with piezoelectric coefficient(d 33) and Curie temperature(TC) found to be 13.3 pC/N and 960 C,respectively.The dielectric and piezoelectric properties of the(LiCe) co-substituted CBNO ceramics exhibit very stable temperature behaviours.This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications. 相似文献
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A chiral metasurface is proposed to realize a tri-band polarization angle insensitive cross-polarization converter. The unit cell of the chiral metamaterial is composed by four twisted anisotropic structure pairs in four-fold rotation symmetry.The simulation results show that this device can work at 9.824 GHz, 11.39 GHz, and 13.37 GHz with low loss and a high polarization conversion ratio(PCR) of more than 99%. The proposed design can transmit the co-polarization wave at14.215 GHz, like a frequency selective surface. The study of the current and electric fields distributions indicates that the cross-polarization transmission is due to electric dipole coupling. 相似文献