Laser absorption and infrared stealth properties of Al/ATO composites

In this work, an Al powder was coated with antimony-doped tin oxide (ATO) to obtain an infrared-laser compatible stealth material. The composites are prepared via a coprecipitation method, characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and measured by ultraviolet spectrophotometer and dual band infrared emissometer. The morphology and microstructure show that the flaky Al powder was coated by the ATO nanoparticles and doped into the SnO₂ rutile structure by an Sb⁵⁺ ion_. The optimal Al content was 20%, and the optimized Sn/Sb molar ratio was 10: 1. Meanwhile, the reflectivity of the composites was 43.454%, and the infrared emissivity in 8–14 μm far infrared waveband range was 0.708. It may shed light on a new material design orientation to obtain high performance laser-infrared compatible stealth materials.     

Laser stealth and laser protection properties of oxide-carbide coatings prepared by atmospheric plasma spraying

With the development of laser technology, laser-related materials have been widely studied. Both laser stealth coatings and laser protective coatings are currently the focus of attention. However, less research has been done on laser stealth and protective integrated coatings. In this paper, plasma-sprayed Y₂O₃–Ti₃AlC₂ coatings were prepared with low-power (LP) and high-power (HP) parameters, and their laser stealth and laser protection properties were characterized. The LP coating and HP coating appeared to have lower reflectivity at 1064 nm because a low-reflectivity second phase and many loose flocs on the surface are introduced, which indicates excellent laser stealth performance. When irradiated by a laser, the LP coating exhibited excellent laser protection ability, and its reflectivity increased after irradiation because Ti₃AlC₂ oxidized and decomposed and densely arranged small particles formed on the surface. The LP coating perfectly protected the 500-W laser irradiation for 20 s. In addition, the laser damage threshold of the LP coating was 5.599 s at 1000-W laser irradiation, which indicates that the LP Y₂O₃–Ti₃AlC₂ coating is a potential material with laser stealth and laser protection integration.     

水性红外隐身涂料制备工艺优化

目的优化水性红外隐身涂层材料制备工艺,提高低发射率红外隐身涂料隐身性能。方法采用红外辐射率测量仪、红外光谱吸收仪等,研究涂层固化温度、涂层表面粗糙度和涂层厚度对低发射率红外隐身涂料隐身性能的影响。结果固化温度对涂层红外发射率和基体树脂红外吸收光谱影响不大,但随着固化温度升高,涂层固化时间明显缩短;随着涂层表面粗糙度的增加,涂层红外发射率增加;表面粗糙材料红外发射率受测试角度影响小于表面光滑材料;在基材上制备不同厚度的涂层,当涂层厚度小于30μm时,涂层红外发射率受基材表面红外发射率影响较大,当大于30μm时,影响较小。结论可以根据实际时间需求选择合适的涂层固化温度,宜选择刮涂方式使涂层表面保持一定的粗糙度,涂层厚度宜为30~40μm。     

FDTD simulations on radar cross sections of metal cone and plasma covered metal cone

Electromagnetic wave interaction with a plasma covered metal surface has been studied using the Radar Cross Section (RCS) changes of a 10 cm diameter and 30 cm height metal cone with and without plasma coverage. A Finite-Difference-Time-Difference (FDTD) method was use to calculate the case of a cone with and without a covering of a 1 cm thick sheet plasma for both S Band (2,3, and 4 GHz) and X Band (8, 10, and 12 GHz) frequencies. The characteristic plasma frequency ω_pe was set at 10 GHz, and electron-neutral collision frequency ν_en chosen to be 20 GHz. The results indicate that the metal cone has very small RCS at head-on direction, and a large RCS looking from the back end. A Plasma covered metal cone was shown to achieve head-on direction monostatic RCS changes between −0.47 and −7.2 dBm² from 2 to 4 GHz, and −11 to −3.2 dBm² RCS changes from 8 to 12 GHz, but at the back end the RCS increases between 2.2 and 2.6 dBm² from 2 to 4 GHz, and varies between −0.9 and 0 dBm² from 8 to 12 GHz. In the two frequency bands investigated, maximum RCS reduction of −15 dBm² occurs at 8 GHz at the same direction as the incident electromagnetic wave polarization. Plasma stealth offers advantages like frequency tunability, but the challenge is establishing an adaptive feedback mechanism that can main a constant plasma density and thus a constant RCS by adjusting the power supplied to plasma generator while monitoring the changes in air speed, altitude, and humidity.     

直升机红外隐身技术研究进展

在阐述直升机红外辐射特征和面临的威胁基础上,对直升机红外辐射特性抑制的原理进行了阐述。回顾了直升机红外辐射抑制技术的研究进展,详细分析了各种红外辐射抑制技术的特点和适用范围。直升机红外辐射特性抑制技术主要有红外抑制器抑制技术、红外诱饵弹等干扰技术、热红外隐身涂料涂层技术、地面停放伪装遮障隐蔽技术等。其中,红外抑制器抑制技术采取混流装置以降低热空气温度,采用耐高温隔热遮挡装置隔绝高温部位等。红外诱饵弹等干扰技术利用其中的烟火剂燃烧产生高温时释放出的大量红外特征信号,达到干扰红外侦察和红外制导武器打击的目的。热红外隐身涂料涂层技术通过涂层自身较低的红外发射率,有效降低直升机表面红外辐射特性,实现与空地背景的较好融合。地面停放伪装遮障隐蔽技术采用具有光学、红外、雷达等隐身性能的伪装器材,实现直升机多波段隐身和防风、防雨、防沙尘等性能。最后,对未来红外隐身技术的研究进行了展望。     

Study of plasma-based stable and ultra-wideband electromagnetic wave absorption for stealth application

A plasma-based stable,ultra-wideband electromagnetic (EM) wave absorber structure is studied in this paper for stealth applications.The stability is maintained by a multi-layer structure with several plasma layers and dielectric layers distributed alternately.The plasma in each plasma layer is designed to be uniform,whereas it has a discrete nonuniform distribution from the overall view of the structure.The nonuniform distribution of the plasma is the key to obtaining ultra-wideband wave absorption.A discrete Epstein distribution model is put forward to constrain the nonuniform electron density of the plasma layers,by which the wave absorption range is extended to the ultra-wideband.Then,the scattering matrix method (SMM) is employed to analyze the electromagnetic reflection and absorption of the absorber structure.In the simulation,the validation of the proposed structure and model in ultra-wideband EM wave absorption is first illustrated by comparing the nonuniform plasma model with the uniform case.Then,the influence of various parameters on the EM wave reflection of the plasma are simulated and analyzed in detail,verifying the EM wave absorption performance of the absorber.The proposed structure and model are expected to be superior in some realistic applications,such as supersonic aircraft.     

VHF频段隐身目标缩比模型的雷达散射截面测量

介绍了甚高频(VHF)频段、工作在水平(H)或垂直(V)极化发射-接收组合(即HH、VV、HV、VH)情况下隐身目标缩比模型的雷达散射截面积(RCS)测量方法;给出了低频段RCS测量与计算的详细过程,采用背景杂波对消和时域加窗处理的方法减少了低频段RCS测量的误差;并给出了两种隐身目标缩比模型的RCS测量结果。测量结果表明:由于谐振效应,在VHF下端的低频段,隐身目标的RCS在平方米的量级,远大于在微波段的测量值;在部分频点,交叉极化的RCS甚至比同极化还强。这为利用隐身目标在频率域的谐振效应和极化域的极化特征,设计具有探测隐身目标能力的现代雷达提供了理论依据。     

基于仿真计算的飞行器雷达隐身性能评估

从飞行器雷达散射截面的计算机仿真出发,对运动飞行器的RCS动态特性和复杂电磁环境下的隐身性能进行研究.基于运动目标姿态参数的转换原理,得到运动目标的动态RCS特性,通过相对计算方法计算雷达的瞬时探测概率,并给出有源和无源干扰条件下探测概率的计算方法;以单部雷达的目标检测准则为基础,给出了雷达组网模式下的综合检测准则;考...     

光谱选择性激光隐身材料研究现状

综述了稀土上转换、光子晶体和有机体系光谱选择性激光隐身材料的光谱选择吸收机理,稀土上转换材料通过上转换原理、光子晶体材料通过膜系材料结构设计、有机体系材料通过特定官能团振动均可实现特定波段光谱能量的选择性吸收。分析了三种光谱选择吸收材料应用于激光隐身的可行性和激光隐身的实现方式,综述了材料的研究现状。指出,光谱选择性激...     

吸波和防红外迷彩涂料在某型号产品上的应用

通过对隐身涂层施工各个环节应该注意的事项进行阐述,指出了隐身涂层施工的关键在于涂层基体的清洁度和控制隐身涂层的厚度,而且通过实际操作以及对施工结果进行分析,进一步指出了在隐身涂层的施工中应该关注的细节,如保护、厚度测量等问题,为保障隐身涂层的施工质量起到了较好的指导作用.