棒束花状α-Fe_2O_3的制备及其气敏特性

以FeCl_3·6H_2O为前驱体,聚乙烯基吡咯烷酮(PVP,分子量为8 000)为表面活性剂,先通过水热反应,再经高温煅烧制备具有棒束花状多级结构的α-Fe_2O_3,并用场发射扫描电子显微镜(FESEM)和透射电子显微镜(TEM)表征样品结构.结果表明:样品结构由棒束以自组装的方式形成,每个棒束由多个单晶纳米棒构成;由该结构制成的传感器件在200℃对丙酮具有良好的选择性及较高的灵敏度.     

柔性透明雷达-红外兼容隐身超材料设计

基于透明导电膜氧化铟锡和高透光聚氯乙烯,设计了一种柔性透明雷达-红外兼容隐身的超材料吸收器.采用氧化铟锡容性频率选择表面,实现了雷达波的高效透过和红外频段的低发射.利用表面电流和功率分布探讨了内部吸收机理,提取等效参数揭示了拟议结构的单负特性.模拟结果表明,在4.58～28.95 GHz的工作频段内实现了吸收率大于90...     

A flexible ultra-broadband metamaterial absorber working on whole K-bands with polarization-insensitive and wide-angle stability

For potential military applications, a flexible metamaterial absorber (MMA) working on whole K-bands with total-thickness of 3.367 mm, ultra-broadband, polarization-insensitive, and wide-angle stability is presented based on frequency-selective surface (FSS). The absorber is composed of polyvinyl chloride (PVC) layer, polyimide (PI) layer, and poly tetra fluoro ethylene (PTFE) layer, with a sandwich structure of PVC-PI-PTFE-metal plate. Periodic conductive patterns play a crucial role in the absorber, and in traditional, it is designed on the upper surface of PI layer to form LC resonance. Different from commonly absorber, all the patterns are located on the lower surface of the PI layer in this work, and hence the impedance matching and absorptivity are improved in this purposed absorber. The flexible absorber with patterns on lower surface of the PI layer is compared with that on upper surface of the PI layer, the difference and the reasons are explained by absorption mechanism based on equivalent circuit model, and surface current density and electric field distribution are used to analyze resonance peaks. Absorptivity is greater than 90% in a frequency range of 10.47 GHz-45.44 GHz with relative bandwidth of 125.1%, covering the whole Ku, K, Ka, and some of X, U bands, especially containing the whole K bands from 12 GHz to 40 GHz. Radar cross section (RCS) is reduced at least 10 dB in 11.48 GHz-43.87 GHz frequency ranges, and absorption remained about 90% when the incident angle changed from 0° to 55°. The purposed absorber is fabricated, measured, and experiment results show good agreement with theoretical analysis and numerical simulation. After bonded on outer surface of different cylinders with diameters of 200 mm and 100 mm, the absorption of MMA is approximately reduced 10% and 20% respectively, which shows good conformal character with surface of various curvatures. Due to the attractive performance on strong absorption in the whole K-bands, flexible and easy conformal, our design exhibits broad potential application in radar stealth and sensors.