Preparation and properties of W-VO2@SiO2 thermotropic phase change materials
In order to enhance the stability of VO2(M)while reducing its phase transition temperature,the hydrother-mal synthesis process of VO2(M)was optimized in this paper using vanadium pentoxide(V2O5)as the vanadium source and hydrazine hydrate(N2H4·H2O)as the reducing agent.By doping W6+and depositing SiO2 on the surface,stability is improved while phase transition performance is guaranteed.The results show that there is a VO2(A)-VO2(M)mutu-al transformation process during the hydrothermal process,and the adjustment of the hydrothermal reaction conditions can lead to VO2(M)with good crystallinity,a phase transition temperature of 66.3 ℃ and a thermal hysteresis width of 9.2 ℃.With the increase of W doping amount(expressed by atomic fraction),the Tc of W-VO2(M)@SiO2 decreases,and ΔT=7.2 ℃ when W doping amount is 1.0 at％.After accelerated test,the VO2 of W-VO2(M)@SiO2 composite still exists as V4+,which has good thermal stability.
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