| Infrared thermal radiation is a kind of ubiquitous natural phenomenon in life.It spreads in the form of electromagnetic wave and carries the function of heat transfer.Many organisms in nature（such as Saharan silver ants and fire beetles）use their ability to adjust infrared radiation to play the role of communication,detection,camouflage and thermal management.Inspired by this,scientists developed infrared smart materials,that is,the use of external fields（electric,magnetic,optical,mechanical force,etc.）to control the optical properties of the infrared band of materials（such as emissivity,reflectivity,transmittance）,has broad application prospects in intelligent Windows,thermal control spacecraft,intelligent cooling clothing and other fields.At present,infrared smart materials mainly rely on the material itself to change its infrared characteristics based on photosensitive characteristics,phase transformation and other reactions under the control of the external field,and its control range is still limited.This study focuses on infrared emissivity and infrared transmittance regulation.The specific research object is patterned electroemissivity material polyaniline and silver-coated nylon fabric.Based on the shape change of smart material,the infrared control ability is improved.Polyaniline is a widely studied electroemissivity material,which has the advantages of fast response rate and high chemical stability.However,the small emissivity modulation range limits its application to a certain extent.In this paper,patterned electrochromic polyaniline films were prepared by chronocurrent deposition combined with laser etching,and their morphology,structure and properties were characterized.The experimental results show that the emissivity of the prepared polyaniline film is 0.87 and 0.53,respectively,and the emissivity change value is0.34.It also has a fast response rate and good cyclic stability.In order to further improve the emissivity modulation range of pan I thin films,the pan I thin films were deformed by applying stress.The effective radiation area of different emissivity regions will change with the change of observation direction and deformation mode,and the overall emissivity of the film can be controlled in a large range without changing the intrinsic emissivity of the constituent materials,and the change value can reach 0.57.By combining polyaniline thin film with shape memory Nitinol wire,the self-deforming bilayer polyaniline thin film with variable emissivity was prepared.The film can change into any shape at room temperature and return to its original shape at more than 50℃.At 70℃,the recovery from folded state to tiled state can be completed within 15s,and the transition from low emissivity to high emissivity can be completed within 30s,and the emissivity change value is 0.49.In order to solve the problem of high emissivity of traditional fabric and serious inhibition of heat loss of human body,Ag@PA fiber bundle was obtained by electroless silver coating on the whole surface of traditional nylon fiber bundle.Experiments and simulations verify that Ag@PA fiber bundles have higher infrared reflectance and lower infrared emissivity than PA fiber bundles.The infrared transmittance of Ag@PA fiber bundle knitted fabric is increased by 150%due to the multistage reflection of silver coating on the surface.Compared with traditional PA textiles,the skin can be cooled by 1.1℃in the indoor environment,realizing"passive cooling"of human body.In addition,different tensile methods and applied stress can change the void size of Ag@PA fabric,thus regulating the infrared transmittance of the fabric.Unidirectional stretching decreases the size of interfabric void,while bidirectional stretching increases the size of interfabric void.When the stretching rate is 15%,the infrared energy of the former decreases from 4.33 m W/cm~2·sr to 4.17m W/cm~2·sr.The latter increases to 4.57 m W/cm~2·sr.In conclusion,the variable-emissivity polyaniline thin films and silver-coated fabrics designed and prepared in this paper can respond to multiple external field stimuli（including temperature,current and stress）and adjust their infrared properties,making them suitable for a variety of complex environments. |
