Infrared thermochromic properties of monoclinic VO2 nanopowders using a malic acid-assisted hydrothermal method for adaptive camouflage

Abstract

Monoclinic VO₂ nanopowders were synthesized using a malic acid-assisted hydrothermal method. The derived VO₂ nanopowders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscopy. The phase transition properties of the monoclinic VO₂ nanopowders were studied using differential scanning calorimetry, which displayed an obvious phase transition at 67.2 °C with a narrow thermal hysteresis width of 4.9 °C. Also, the resistance–temperature relationship and the thermal infrared images in the waveband 7.5–13 μm were analyzed. The results showed that the VO₂ samples have excellent electrical properties with resistance changes as large as two orders of magnitude. The VO₂ nanopowders obtained can control their infrared radiation intensity actively and lower their radiation temperature. Furthermore, the stability of the VO₂ nanopowders was investigated. The results showed that the VO₂ nanopowders have good thermal stability, oxidation resistance below 375 °C in an air atmosphere and humidity resistance, which has great application prospects in adaptive infrared camouflage technology.