3D Printed Meta‐Helmet for Wide‐Angle Thermal Camouflages

Thermal camouflage utilizes the manipulation of heat fluxes to conceal an arbitrary object in various environments from being detected via thermography. In the past decade, the field of thermal metamaterials and the technique of 3D printing have been rapidly developed, which makes nonintuitive heat flux manipulation feasible. However, when thermal metamaterials are applied to the thermal camouflaging, their conductivities are dependent on the properties of background, leading to the damage of background integrality. Moreover, previous thermal camouflaging schemes have mostly worked in the 2D regime, largely restricting their functional angles and application scenarios, especially in complex environments. Here, wide‐angle radiative thermal camouflaging is realized by using a 3D‐printed meta‐helmet of extremely anisotropic thermal conductivities. Based on 3D coordinate transformation, this meta‐helmet directly maps temperature distributions from the background to the metamaterial surface without damaging background integrity. The non‐invasive device is efficient in wide‐angle thermal camouflage by rendering the same emissivity to the background medium and can self‐adjust to various even unknown background thermal fields, which is demonstrated in numerical simulations and experiments. This work opens a door to the 3D transformation‐thermotics‐based devices for versatile practical applications in thermal infrared stealth of macro‐sized objects and others.     

Ultrathin Titanium Carbide (MXene) Films for High-Temperature Thermal Camouflage

Thermal camouflage has attracted increasing attention owing to the rapid development of infrared (IR) surveillance technologies. Various materials and systems have been developed to date, but the realization of high-temperature thermal camouflage using ultrathin film/coating remains a great challenge; this is of great significance, especially for IR stealth in military equipment. This work demonstrates a series of ultrathin Ti₃C₂T_x MXene films (as low as 1 µm) with superior high-temperature indoor/outdoor thermal camouflage performance: wide camouflage temperature range (from below −10 °C to over 500 °C), large reduction in radiation temperature (exceeding 300 °C for objects with temperatures over 500 °C), long-term high-temperature or fire stability, multifunctionality including disguised Joule heating capability, and high electromagnetic interference shielding efficiency. The superior high-temperature thermal camouflage performance of the ultrathin MXene film is attributed to its low mid-IR emissivity (0.19), which is comparable to that of stainless steel but far below that of other 2D nanomaterials, such as graphene. The multifunctional ultrathin MXene films prepared through simple vacuum-assisted filtration provide a feasible method for efficient high-temperature thermal camouflage using ultrathin films, demonstrating the great promise of MXene materials for thermal camouflage, IR stealth, counter-surveillance, and security protection.     

新型热红外伪装体系

针对热红外成像侦察技术对军事目标形成的严重威胁，介绍了三种新机理型热红外伪装体系：1）三色涂料体系，三色涂料以一定形式叠加在军事目标上，利用涂层和孔洞的明暗实现目标与背景在红外及可见光区的融合。2）相变材料体系，将相变材料以微胶囊的形式分散在基体中，利用其发生相变时伴随的吸热效应，对目标产生的热量和目标温度加以控制。3）簇饰物伪装体系，选用低发射率的聚合物薄层材料做成叶簇状物附在常规伪装网上，在移动目标的周围产生空气流，从而达到散热和抑制目标红外辐射的目的。     

Long-Term Infrared Stealth by Sandwich-Like Phase-Change Composites at Elevated Temperatures via Synergistic Emissivity and Thermal Regulation

The rapid development of infrared surveillance technologies has attracted great attention for scientists to design advanced functional materials with prominent infrared stealth and thermal camouflage effectiveness. In the current study, a sandwich-like functional composite based on a crosslinked polyimide aerogel, a meso-erythritol (mE)-based phase-change composite, and an MXene film has been developed to achieve long-term thermal camouflage at elevated temperatures. In this composite system, the lower aerogel layer can act as a barrier to insulate heat transfer through its layer-stacking structure under ultralow directional thermal conduction. The introduction of the middle phase-change composite layer ensures that the composite system obtains a dynamical temperature-regulation capability through sensible and latent heat absorption of mE as a phase change material, while the upper MXene layer provides a very low emissivity surface for the system. As a result, the developed composite achieves a significant reduction in the thermal radiation temperature of a high-temperature target. Moreover, the MXene film exhibits good electromagnetic interference shielding effectiveness, making the sandwich-like composite obtain a thermal camouflage capability in various complicated scenarios. This work provides a promising approach for the design of advanced functional materials to realize long-term infrared stealth and thermal camouflage of high-temperature targets in security protection and counter-surveillance.     

林地型背景热红外伪装的温差阈值试验研究

针对热红外伪装的温差阈值影响因素多的问题,提出了利用背景温度起伏的统计特性计算背景热红外伪装的温差阈值的方法.通过一种典型的南方林地型背景温度野外测量试验,研究分析背景的热红外特性及其变化规律,得到了该地域热红外伪装的温差阈值.计算结果表明该方法的有效性.     

伪装网平均热红外辐射透过率指标的确定方法

从红外物理基本定律出发，结合空中光电侦察原理和地面背景温度起伏状况，提出了由工作波段内目标和背景的辐射亮度以及背景的辐射亮度起伏幅度来确定伪装网平均热红外透过率指标的方法。     

A General Model for the Electric Power and Energy Efficiency of a Solar Thermoelectric Generator

A general model for the electric power and energy efficiency of a solar thermoelectric generator is discussed, considering the influences of the input energy, the thermal conductivity, the absorptivity and emissivity of the heat collector, and the cooling water. The influences of these factors on the performance of the thermoelectric device are discussed, considering the thermoelectric generator as a whole, including the heat collector, the thermoelectric device, and the cooling. Results show that high input energy, and high absorptivity and low emissivity of the heat collector, are helpful for obtaining a high-performance thermoelectric generator. A high thermal transfer coefficient of the cooling water can increase the temperature difference across the thermoelectric device but results in greater accessory power requirements if increased further.     

红外迷彩伪装涂料发射率对目标伪装效率的影响

伪装效率是衡量涂料的红外伪装效果的重要指标,它取决于涂料本身的红外发射率、特定的环境背景和气候条件等多种因素。在一种典型的南方草地背景下,随着阳光辐射和昼夜环境温度的变化,研究了不同发射率涂料样品的红外伪装效率;并对不同发射率的样品进行组合,研究比较复杂的红外迷彩伪装目标的伪装效率,在此基础上,讨论了发射率对红外迷彩伪装目标的伪装效率的影响。     

用于红外焦平面阵列非均匀性校正的辐射参考源

概述了4种红外焦平面阵列非均匀性过程中使用到的参考源。成为产品前,通常使用面源黑体作为参考源对红外焦平面阵列进行非均匀性校正;在热成像系统应用中动态非均匀性校正中,普遍使用的辐射挡板由于没有连有控温装置,只能进行一点校正,在场景温度偏离校正温度时,校正效果会受到影响;美国第三代前视红外成像系统中使用连有热电制冷器的热电参考源,利用热电制冷器对发射表面进行控温,可实现两点校正算法;为基于边框的SBNUC校正算法设计的U型边框黑体光阑,对视场中心没有遮挡,利用半导体制冷器对U型边框黑体光阑的进行控温,能根据场景信息自适应地实现的两点校正。     

Thermally Controlled,Active Imperceptible Artificial Skin in Visible‐to‐Infrared Range

Cephalopods’ extraordinary ability to hide into any background has inspired researchers to reproduce the intriguing ability to readily camouflage in the infrared (IR) and visible spectrum but this still remains as a conundrum. In this study, a multispectral imperceptible skin that enables human skin to actively blend into the background both in the IR‐visible integrated spectrum only by simple temperature control with a flexible bi‐functional device (active cooling and heating) is developed. The thermochromic layer on the outer surface of the device, which produces various colors based on device surface temperature, expands the cloaking range to the visible spectrum (thus visible‐to‐IR) and ultimately completes day‐and‐night stealth platform simply by controlling device temperature. In addition, the scalable pixelization of the device allows localized control of each autonomous pixel, enabling the artificial skin surface to adapt to the background of the sophisticated pattern with higher resolution and eventually heightening the level of imperceptibility. As this proof‐of‐concept can be directly worn and conceals the human skin in multispectral ranges, the work is expected to contribute to the development of next‐generation soft covert military wearables and perhaps a multispectral cloak that belongs to cephalopods or futuristic camouflage gadgets in the movies.     

一种基于灰度直方图的热红外迷彩伪装设计方法

直接模拟侦察环境,从背景的热红外图像出发,运用灰度直方图从整体分析背景热红外特征,根据物体热红外图像亮度与其视在温度的对应的关系,提出一种热红外迷彩伪装设计方法,减小了背景温度测量统计方法所存在的误差.     

Wearable Janus-Type Film with Integrated All-Season Active/Passive Thermal Management,Thermal Camouflage,and Ultra-High Electromagnetic Shielding Efficiency Tunable by Origami Process

Multifunctional films with integrated temperature adjustment, electromagnetic interference (EMI) shielding, and thermal camouflage are remarkably desirable for wearable products. Herein, a novel Janus-type multifunctional ultra-flexible film is fabricated via continuous electrospinning followed by spraying. Interestingly, in the polyvinyl alcohol (PVA)/phase change capsules (PCC) layer (P₁), the PCC is strung on PVA fibers to form a stable “candied haws stick” structure that obviates slipping or falling off. The film with sufficient melting enthalpy (141.4 J g⁻¹) guarantees its thermoregulation capability. Simultaneously, its high mid-IR emissivity (90.15%) endows the film with radiative cooling properties (reducing temperature by 10.13 °C). Mechanical strength is significantly improved by superimposing a polylactic acid (PLA) layer (P₂) on its surface. By spraying a thin MXene layer on the PLA surface of P₂P₁ film, the obtained (MXene/P₂P₁) MP₂P₁ film is endowed with satisfactory low-voltage heating, photo-thermal and superior thermal camouflage performance, achieving all-season thermal comfort. Impressively, the flexible MP₂P₁ film achieves enhanced EMI shielding effect from 50.3 to 87.8 dB through a simple origami process, which simplifies the manufacturing process of high-performance EMI shielding materials. In brief, the multifunctional Janus-type MP₂P₁ film is an attractive candidate for future wearable products with personalized thermal management and anti-electromagnetic radiation.     

地物目标热红外光谱发射率的野外测量方法研究

在航天红外遥感应用中,地物目标光谱发射率是卫星遥感测量地面温度的一个重要参数。野外测量的大气环境、目标背景和地物的热力学特性等因素的影响,使得野外测量地物目标表面光谱发射率变得较为复杂。重点讨论了利用傅里叶变换红外光谱仪野外测量地物目标光谱发射率的方法和程序,介绍了几种正确分离目标温度与发射率的方法。野外测量实验结果表明,按照文中所述的测量方法,测量得到的地物热红外光谱发射率具有良好的一致性,发射率测量误差小于0．02。     

Li4Ti5O12: A Visible‐to‐Infrared Broadband Electrochromic Material for Optical and Thermal Management

Broadband electrochromism from visible to infrared wavelengths is attractive for applications like smart windows, thermal camouflage, and temperature control. In this work, the broadband electrochromic properties of Li₄Ti₅O₁₂ (LTO) and its suitability for infrared camouflage and thermoregulation are investigated. Upon Li⁺ intercalation, LTO changes from a wide bandgap semiconductor to a metal, causing LTO nanoparticles on metal to transition from a super‐broadband optical reflector to a solar absorber and thermal emitter. Large tunabilities of 0.74, 0.68, and 0.30 are observed for the solar reflectance, mid‐wave infrared (MWIR) emittance, and long‐wave infrared (LWIR) emittance, respectively, with a tunability of 0.43 observed for a wavelength of 10 µm. The values exceed, or are comparable to notable performances in the literature. A promising cycling stability is also observed. MWIR and LWIR thermography reveal that the emittance of LTO‐based electrodes can be electrochemically tuned to conceal them amidst their environment. Moreover, under different sky conditions, LTO shows promising solar heating and subambient radiative cooling capabilities depending on the degree of lithiation and device design. The demonstrated capabilities of LTO make electrochromic devices based on LTO highly promising for infrared‐camouflage applications in the defense sector, and for thermoregulation in space and terrestrial environments.     

Rapid thermal processing of silicon wafers with emissivity patterns

Fabrication of devices and circuits on silicon wafers creates patterns in optical properties, particularly the thermal emissivity and absorptivity, that lead to temperature nonuniformity during rapid thermal processing (RTP) by infrared heating methods. The work reported in this paper compares the effect of emissivity test patterns on wafers heated by two RTP methods: (1) a steadystate furnace or (2) arrays of incandescent lamps. Method I was found to yield reduced temperature variability, attributable to smaller temperature differences between the wafer and heat source. The temperature was determined by monitoring test processes involving either the device side or the reverse side of the wafer. These include electrical activiation of implanted dopants after rapid thermal annealing (RTA) or growth of oxide films by rapid thermal oxidation (RTO). Temperature variation data are compared with a model of radiant heating of patterned wafers in RTP systems.     

相变材料及其在热红外伪装领域的应用研究

综述了各种相变材料(PCM)的性能特点及研究现状,研究分析了相变材料在军事热红外伪装领域中的应用机理及其在伪装纺织品和假目标中的应用,最后探讨了将相变材料应用于热红外伪装需要解决的问题.     

Optical Design of Silica Aerogels for On-Demand Thermal Management

Silica aerogels, a type of porous material featuring extra low density and thermal conductivity, have drawn increasing interest from both academia and industry owing to their excellent thermal insulation performance. However, thermal insulation is always the single consideration when silica aerogels are used for thermal management. In this study, the on-demand thermal management (ODTM) of silica aerogel with either passive thermal insulation, passive heating, or passive cooling in different environments is revealed. The ODTM behavior of silica aerogels can be simply fulfilled through their optical property variations such as solar light transparency and infrared emissivity, which are controllable via the microstructures of the building blocks and surface composition design. Robust solar heating of 25 °C higher than the ambient in the daytime and sub-ambient cooling of 7 °C at night is achieved with the traditional transparent silica aerogel. Interestingly, sub-ambient cooling of 5 °C in the daytime and a warmer state on cold nights is achieved by modifying its solar transmittance and infrared emissivity. This study guides a comprehensive understanding of the thermal management behavior of silica aerogels and leads to ODTM applications of silica aerogels by tailoring their optical and thermal conductivity properties.     

热像仪在机舱蒸汽管路巡检中的应用

舰船机舱蒸汽管破损是常见的故障,使用热像仪进行蒸汽管破损监测具有重要的应用价值。阐述了日常工作中用热像仪对蒸汽管路进行巡检时的判定标准、监测流程、舱内环境因素对监测的影响及应对措施。日常工作中主要采用直接比较法进行定性判别。监测时,热像仪与被测目标的距离、角度和舱室环境温度对结果判定的影响较小;而其他热源和物体的发射率对结果判定的影响较大。     

Stretchable Skin‐Like Cooling/Heating Device for Reconstruction of Artificial Thermal Sensation in Virtual Reality

Along with visual and tactile sensations, thermal sensation by temperature feeling on the skin can provide rich physical information on the environment and objects. With a simple touch of objects, relative temperature can be sensed and even objects can be differentiated with different thermal properties without any visual cue. Thus, artificially reproducing accurate/controllable thermal sensation haptic signals on human epidermis will certainly be a major research area to reconstruct a more realistic virtual reality (VR) environment. In this study, for the first time, a skin‐like, highly soft and stretchable and bi‐functional (both cold and hot sensation) thermo‐haptic device is reported for wearable VR applications with a single device structure (not separate heater and cooler). The skin‐like thermo‐haptic (STH) device can actively cool down and heat up deformable skin surfaces with instantaneous and accurate adjustment of temperature based upon a feedback control algorithm to mimic desirable thermal sensation with 230% stretchability. As a proof‐of‐concept, the STH device is integrated with a finger‐motion tracking glove to provide artificial thermal sensation information to the skin in various situations such as touching cold beer bottles and hot coffee cups in virtual space. This new type of STH device can offer potential implications for next‐generation haptic devices to provide unique thermal information for a more realistic virtual‐world field and medical thermal treatment.     

新型多波段复合植被伪装材料

为满足多波段兼容伪装的需求,采用多种材料合理匹配与多功能层组合结构的方法,制备了一种可实现可见光、红外和雷达多波段兼容的新型复合植被伪装材料.用雷达波屏蔽效能和反射率测试实验对伪装材料的吸波性能进行了测试,用成像法对伪装材料的可见光和热红外伪装性能进行了试验检测.结果表明,研制的伪装材料有良好的雷达波衰减性能,大于5 ...