Large-scale Construction And Application Of Hot Liquid Super-repellency Surface

It is common that evaporation-condensation is one of the phenomena in the natural world.Its essence is the behavior of gas-liquid phase change caused by heat transfer when hot vapor comes in contact with a cold surface,which brings a lot of inconvenience to the life and production of human society,such as dewing,frosting,icing,scalding,scaling and fouling.The controllable construction of superhydrophobic surface to effectively reduce the gas-liquid phase change behavior of surface has been widely studied.However,the hot liquid super-repellency ability is still extremely limited due to the high flux evaporation-condensation behavior of hot liquid.Therefore,it has become one of the most important topics in surface protection field that effectively solve the problems of scalding and scaling through the controllable construction of hot liquid super-repellency surface.In this paper,we propose a general strategy to achieve superhydrophobic hot liquid on various solid surfaces by constructing micro-nano binary topography.By establishing the Cassie-Baxter model and evaporation-condensation model,the surface hydrothermal repulsion synergistic mechanism of the intrinsic wetting effect of nanostructures and condensates carrying effect of micron-structure is indicated.Based on this,the large-scale construction of hot liquid super-repellency properties was realized on fabrics and rigid substrates,which expounded the application advantages of superhydrophobic surfaces in scald prevention,scaling prevention,self-cleaning,and provided a new strategy for surface protection for the environment of hot liquid erosion with great development and application prospects.The specific research contents and results are as follows:(1)Micro-nano binary topography was constructed on typical micron-structures(2D-wire mesh,3D-foam metal and planar sand array)by low surface energy modification and one-step spraying.The static and dynamic wettability of droplets at different temperatures showed that the high-temperature droplets(95?water/150?oil)maintain the Cassie state on the surface of micro-nano binary topography,and change to Wenzel state on the surface of single micron structure and single nano structure.Through the establishment of Cassie-Baxter wetting model and evaporation-condensation model,it is proved that the key of micro-nano binary topography for hot liquid super-repellency is the synergistic effect of intrinsic wetting based on nano-structure and condensation load of micron-structure,which provides theoretical basis and technical guidance for the construction of universal superphobic hot liquid surface.For example,the micro-nano binary synergistic structure constructed with copper foam and carbon modified nano-silica exhibits superhydrophobic and oleophylic characteristics,which can maintain a separation efficiency of more than 98%after 20 cycles of hot-oil separation.The micro-nano binary topography constructed with foamed concrete and nano-silica modified with fluorine showed superhydrophobic and superhydrophobic properties,and the weight gain rate was only 36%of that of the original foamed concrete after boiling water for 72 h.(2)Hot liquid super-repellency surfaces were prepared on 8 kinds of representative fabrics by dip-rolling and spraying method.Based on maintaining excellent permeability,superhydrophobic hot liquid surface also showed excellent thermal stability,mechanical wear resistance and corrosion resistance,laying a foundation for long-term protective use.After 30 min of hot steam injection,the weight gain rate of the hot liquid super-repellency clothe was only 32%of that of the original clothe.After 20 min of concentrated sulfuric acid or 12 h of aqua regia erosion,most of the superhydrophobic fabrics still maintained their excellent hot liquid repulsive properties,that is,the rolling angle of hot water was less than10°.In the anti-scald test without emergency reaction,the time over 60?on the back of the hot liquid super-repellency fabric was 0.00 s(curtain),0.00 s(lab gown),0.00 s(baby bib),4.17 s(denim),0.00 s(non-woven)and 4.00 s(sleepwear),respectively.In the anti-scald test with stress capability,the time for the back of hot liquid super-repellency fabric exceeding60?was 1.70 s(cotton gloves)and 1.80 s(yarn gloves)respectively,and all the above temperatures were far below the scalding standard(the time over 60?was more than 5 s).It is confirmed that the superhydrophobic hot liquid fabric can greatly reduce the incidence of thermal and chemical scald,and significantly reduce the severity of scald,and greatly reduce the physical pain,psychological shadow and economic loss caused by scald.(3)Epoxy@SiO₂ composite primer was prepared by epoxy resin and micron SiO₂,and the micron rough structure was uniformly sprayed on the surface.Then,fluorine modified chain SiO₂ nanoparticles were used to construct fluorine modified micro-nano binary topography,showing excellent hot liquid repulsion.The prepared coating not only integrates high temperature stability,mechanical wear resistance and chemical stability,but also has excellent anti-scaling and self-cleaning characteristics.The sliding angles of 95?water and150?oil are still below 10°after sufferance of the tape peeling for 30 cycles,ultrasonic processing for 30 min,water washing for 30 min,water-boiling for 12 h,hot steam injecting for 720 min,stuffy steaming for 180 min,concentrated sulfuric acid corroding for 20 min,or aqua regia corroding for 720 min.Meanwhile,it can be found from the results after 5 times of rapid scaling test,the mass change of the original sample,single nano-structure and enhanced nano-structure is 10.32 g/m~2 10.23 g/m~2 and 10.58 g/m~2,respectively,while the surface mass change of hot liquid super-repellency coating is 0.00 g/m~2.In addition,after 12min thermal steam treatment,the hot liquid super-repellency coating remains as clean as before.