Research On Thermal Infrared Camouflage Technology Based On VO₂

Thermal infrared camouflage technology can be used in various military fields.At present,the common methods to achieve thermal infrared camouflage are to reduce the surface emissivity and surface temperature of objects,and to achieve dynamic thermal camouflage by modulating the emissivity.According to Stefan-Boltzmann law,the radiation energy of the object is positively correlated with its own temperature and emissivity.We can realize thermal camouflage by accurately controlling emissivity of sample when its temperature rises.VO₂ performs phase transformation at a certain temperature,which making its emissivity in the infrared band decrease with temperature.However,the phase transition temperature range of VO₂ is narrow（60-80℃）,making it difficult to achieve thermal camouflage in a large temperature range.Therefore,gradient doping W was used to widen the temperature range of VO₂ phase transition,and a 3-layer W-VO₂ film structure was used to achieve thermal infrared camouflage in a large temperature range in this thesis.After exploring the performance of doped VO₂film,this thesis further proposed the idea of infrared thermal coding,and realized the effect of information loading by temperature-controlled infrared pattern and temperature-controlled infrared transmittance.Specifically,the main work and innovations of this thesis are summarized as follows:（1）Firstly,We grown VO₂ thin films on quartz substrate by PLD process,and the W ratio of doping was determined to be 0%,0.8%,1.7%,so as to form three W-VO₂thin films with composition gradient.Then,three kinds of thin films were prepared on quartz substrate,and their microstructure,electrical,infrared and other properties were characterized.The doping of W changes the crystal lattice constant of VO₂,effectively reduces the phase transition temperature of VO₂,and broadens the phase transition interval.（2）A multilayer film structure was designed by using the prepared three kinds of films to achieve infrared camouflage in wide temperature region.The surface emissivity of 8-14μm multilayer structures prepared by step annealing decreases with increasing temperature in the range of 40-80℃.The decrease of emissivity counterbalances the increase of radiation energy caused by its own temperature rise by precise emissivity design.The radiation temperature of the sample is kept at about 41.5℃in this temperature range,so we realized the dynamic thermal infrared camouflage.According to the principle of infrared thermal imager,the radiation temperature is calculated and the influence of testing environment on the camouflage effect of multilayer film is quantitatively measured.（3）The doped W-VO₂ film has the property of gradient phase transition.The phase transition temperatures of three kinds of films were obtained by taking the derivative method of emissivity,and a temperature-controlled infrared thermal imaging pattern structure was designed by using the different phase transition temperatures in this thesis.The samples show the numbers"1","4"and"9"under the infrared thermal imager from no pattern when its temperature rises.In addition,a series of temperature-controlled infrared transmittance metamaterials are designed and optimized according to the phase difference theory,then we proposed the application of these metamaterials in temperature-controlled hologram transformation and thermal logic operation.