| Nano VO2 has excellent thermochromic properties and other changes in optical,magnetic,and electrical properties during the phase change.These properties have made it widely used in many fields.The phase transition temperature of VO2 is 68?,the temperature can be reduced to 38??50? by W doping,which is close to room temperature.Therefore,nano VO2 has great development prospects in the field of phase change thermal coatings.However,VO2 is nanoparticle,which is easy to agglomerate in the coating.This article modified it with organic grafting and inorganic coating,respectively,to improve the dispersion stability in the coating.This paper first characterizes the raw materials VO2 and W-VO2.The analysis results show that W-VO2 and VO2 have the same surface structure,while the phase temperature of W-VO2 is lower,and the particle size distribution is more uniform.In the subsequent experiments,WVO2 was used as the research object to study the effect of surface organic graft modification and inorganic coating modification on the dispersion of W-VO2 in the coating.Among these modification methods,W-VO2 with better modification effect was selected to be added to the epoxy resin,and its influence on the corrosion resistance and heat transfer performance of the epoxy coating was studied.(1)Surface modification of W-VO2 by using silane coupling agents KH-550 and KH-560 as surface modifiers.FTIR and DSC analysis results show that KH-550 can undergo grafting reaction on W-VO2 surface,while KH-560 has almost no grafting reaction on W-VO2 surface.The results of the dispersion experiment show that:the W-VO2 modified by KH-550 and KH560 is deposited in an epoxy solution(E-44 epoxy resin:xylene:n-butanol mass ratio of 10:7:3).No significant change in time.Titanate coupling agents TC-WH and HY-311 are used as surface modifiers to surface organically modify W-VO2.FTIR and DSC analysis results show that both TC-WH and HY311 can be grafted with organics on the surface of W-VO2,and the phase transition temperature of the modified W-VO2 is reduced from 48? to 44?.The contact angle test of W-VO2 showed that the contact angle of the modified W-VO2 increased from 40.2° to 92.4° and 80.7°,respectively.The results of the dispersion experiment showed that the stability of the W-VO2 modified by the two coupling agents in the epoxy solution was greatly improved,and the sedimentation time was increased from 36 hours before the modification to 200 hours without completely sinking.(2)The surface of W-VO2 was coated with SiO2 and TiO2 by Stober method.mechanochemical method,coupling agent method,and St?ber-like method.TEM and sedimentation experiment results show that:Stober method was successfully used to coat SiO2 inorganic microspheres on W-VO2,and the sedimentation time was increased to 96 h.In addition to coating SiO2 inorganic microspheres on W-VO2 It also accompanied by the production of flocculent TEOS hydrolysis by-products and did not sink significantly in the epoxy solution for 200 h;the coupling agent coating method connected the SiO2 and W-VO2 through the coupling agent,which improved the W-VO2 Dispersibility,did not completely sink to the bottom in 200 hours in epoxy solution;St?ber-like method failed to achieve effective coating of W-VO2.(3)Based on the above modification results,W-VO2/HY-311 has good grafting effect,stable dispersion in epoxy solution,and the phase transition temperature of W-VO2 is close to room temperature.It is selected as a filler with a mass fraction of 0,1,2.5,5,7.5are added to the epoxy resin to prepare W-VO2/epoxy resin heat transfer coating.With the addition of W-VO2/HY-311,the adhesion of the W-VO2/epoxy resin heat transfer coating increases,the saturated salt water absorption rate decreases,and the corrosion resistance improves.When the added amount of W-VO2 reaches 5,W-VO2/HY-311 is continuously added,and the change of adhesion and saturated salt absorption becomes gentle.After immersion in 3.5%NaCl solution for 264 hours,the impedance modulus of the epoxy varnish coating at 0.01 Hz decreased from 6.24Χ1010?·cm2 at 4 hours to 2.64Χ108 ?·cm2;The WVO2/HY-311 with the added amount of 1,2.5,5,and 7.5 of the W-VO2/epoxy resin heat transfer coating at 0.01 Hz has an impedance mode of 1010 after 264 hours.The resalt shows the coating's corrosion resistance has been improved.(4)After 30 minutes of exposure to a 500 W iodine-tungsten lamp,the internal temperature measurement results of the self-made device showed that:when the W-VO2/HY-311 was added at 1,2.5,5,and 7.5.Compared with the addition amount of 0,it was reduced by 0.5%,36.8%,48%and 57%,respectively.When the amount of W-VO2/HY-311 is more than 2.5,the heat transfer effect of the coating is significantly improved. |
PDF Full Text Request