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

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 degrees C with a narrow thermal hysteresis width of 4.9 degrees C. Also, the resistance-temperature relationship and the thermal infrared images in the waveband 7.5-13 mm 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 degrees C in an air atmosphere and humidity resistance, which has great application prospects in adaptive infrared camouflage technology.