Preparation And Structural Regulation Of Thermochromic Nano-VO₂

Vanadium dioxide(VO2)is a thermochromic material with reversible metal-insulator phase transition characteristics.As a temperature-controlled packaging material,it can intelligently adjust the transmittance of solar radiation light,thus controlling the temperature inside the packaging container and prolonging the storage time of the product.The size and structure of VO2 crystal are important factors affecting its thermochromic performance.It is an important part of developing VO2 thermochromic materials to regulate these factors by optimizing the preparation process.At present,the research on the growth mechanism,morphology,structure and phase transformation characteristics of nano-VO2 is still insufficient,which restricts the large-scale development and application of the thermochromic materials of VO2.In this paper,the precipitation-hydrothermal method was firstly adopted to prepare rod-shaped,snowflake and granular powders of VO2 with vanadium pentoxide(V2O5)as the vanadium source by changing the hydrothermal reaction conditions.The morphology,structure and phase of three VO2 products were studied by SEM,XRD,TEM,Raman and other characterization methods.The results showed that the formation mechanism of different VO2 forms was different.DSC was used to analyze the phase transition temperature of three kinds of VO2 annealed products.The results show that the phase transition temperature of nanoparticle VO2 is the lowest,and the thermal hysteresis temperature range of reversible phase transition is the lowest.Secondly,the preparation process of nanoparticle VO2 was optimized.Using V2O5 as raw material,ascorbic acid(C6H8O6)as reducing agent and NaOH as precipitator,VO2 particles with particle size of 30?60 nm were prepared.The microstructure and phase of the prepared nanometer VO2 were analyzed by XRD,FT-IR and other means,and the effects of reaction conditions on the morphology,structure and phase transformation characteristics of the synthesized nanometer VO2 were studied.The results showed that the optimal process parameters were hydrothermal temperature 260?,hydrothermal time 18 h and the dosage of surfactant 1.5 mmol.The nanoparticle VO2 particles with particle size of about 60 nm,uniform distribution and phase transition temperature 68.7? were obtained by precipitation and hydrothermal method.In this paper,the rational regulation of the morphology,structure and properties of VO2 can be realized by optimizing the process conditions,and help to improve the growth mechanism and structure control theory of VO2 crystal,so as to provide experimental basis and experimental basis for the application of VO2 thermochromic materials in the field of intelligent packaging.