Research ArticleMATERIALS SCIENCE

Manipulating metals for adaptive thermal camouflage

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Science Advances  27 May 2020:
Vol. 6, no. 22, eaba3494
DOI: 10.1126/sciadv.aba3494
  • Fig. 1 IR modulation potentials.

    (A) Schematics of a nanoscopic Pt film–based RSE device (left) before and (right) after electrodeposition. (B) Sheet resistance of the evaporated Pt films for different Pt thicknesses. The inset shows photographs of (left) the 1-nm Pt film and (right) the 2-nm Pt films after electrodeposition in an RSE three-electrode system, and the light-reflecting plate is the Pt counter electrode in the three-electrode system. (C) Volmer-Weber growth of noble metals on heterogeneous surfaces. The inset shows the highly magnified surface morphologies of the evaporated Pt films on BaF2 substrate with Pt thickness of 4 nm. (D) Spectral refractive index of BaF2 substrate and Pt film. (E) The ratio of average IR transmittance (T%), average IR reflectance (R%), average Pt-induced IR absorbance (PA%), and average substrate-induced IR absorbance (SA%) of the Pt evaporated BaF2 substrates in the range of 3 to 14 μm. (F) Total IR reflectance spectra of the 3 nm Pt/BaF2 substrate before and after Ag electrodeposition (15 s) in an RSE three-electrode system. The total IR reflectance spectrum of the BaF2 substrate covered standard gold (Au) film represents an ideal case, in which the Pt-induced IR absorption part and the IR transmission part of the 3-nm Pt/BaF2 substrate have been totally converted to IR reflection. (G) Schematics and surface morphologies of electrodeposited Ag films on (left) a commercial ITO electrode and (right) a 3-nm Pt film. Photo credit: Mingyang Li, National University of Defense Technology.

  • Fig. 2 Dynamic IR performance.

    (A and B) Real-time MWIR and LWIR images of device-2 and device-3 during the electrodeposition process, respectively. (C and D) Apparent temperature curves (central region) of the assembled devices in the MWIR and LWIR images during the electrodeposition process. (E) Apparent temperature difference curves between the central and peripheral regions of the assembled devices in the LWIR images during the electrodeposition process. (F) “Real-time” total IR reflectance spectra of device-3. (G) Maximum emittance tunability ranges of device-3, device-4, and device-5 in the MWIR and LWIR ATWs. (H) Cycling performance of device-3 (monitored by the apparent temperature curves at its central and peripheral regions in the LWIR images). (I) Total IR reflectance spectra of device-3 (in low-emittance state) and a nonspectrally selective low-emittance surface in the range of 2.5 to 25 μm. The yellow shaded region indicates the thermal radiation of a 330 K blackbody. The percentages (3, 15, 43.3, and 38.6%) shown in the figure represent the proportion of radiant energy in the range of 3 to 5 μm (MWIR), 5 to 7.5 μm, 7.5 to 13 μm (LWIR), and 13 to 25 μm, respectively. (J) Real temperature variations of device-3 (in low-emittance state) and a nonspectrally selective low-emittance surface during thermal measurements. Photo credit: Mingyang Li, National University of Defense Technology.

  • Fig. 3 Multiplexed and enlarged adaptive devices.

    (A) LWIR images of a three-by-three multiplexed array (left) before and (right) after selective electrodeposition of different pixels for different times. (B) LWIR images of an enlarged independent device (left) before and (right) after electrodeposition for different times. Photo credit: Mingyang Li, National University of Defense Technology.

  • Fig. 4 Multisubstrate compatibility.

    (A) Schematics of the IR reflection mode of (left) the flat surface–based and (right) the rough surface–based adaptive devices under external thermal flux in their low-emittance state. (B and C) “Real-time” IR reflectance spectra of the polished BaF2-based device (device-3) and the rough BaF2-based device before and after electrodeposition. The total reflectance spectra (solid lines) are shown along with their specular (dashed lines) and diffuse (dotted lines) components. (D) Real-time LWIR images of the polished BaF2-based device (device-3) and the rough BaF2-based device under different external thermal flux during the electrodeposition process. (E) Schematic of a flexible surface–based adaptive device. (F) LWIR images of the flexible PP–based device on a curved cup surface (left) before and (right) after electrodepositing for 25 s. (G) “Real-time” total IR reflectance spectra of the flexible PP–based device. Photo credit: Mingyang Li, National University of Defense Technology.

  • Fig. 5 Visible compatibility.

    (A) Schematics of a visible-wavelength-scale-thick Cr2O3 layer decorated adaptive device (left) before and (right) after electrodeposition. (B) Photographs and “real-time” visible reflectance spectra of the Cr2O3 decorated adaptive devices before and after electrodeposition (15 s). (C) Total visible-to-IR transmittance spectra of the Cr2O3-coated BaF2 substrates. (D) “Real-time” total IR reflectance spectra of the Cr2O3 decorated adaptive devices before and after electrodeposition (15 s). (E) Maximum emittance tunability ranges of the undecorated adaptive device (device-3) and the Cr2O3 decorated adaptive devices. Photo credit: Mingyang Li, National University of Defense Technology.

Supplementary Materials

  • Supplementary Materials

    Manipulating metals for adaptive thermal camouflage

    Mingyang Li, Dongqing Liu, Haifeng Cheng, Liang Peng, Mei Zu

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