| The ice/frost accumulation on the surfaces of aircraft wing,wind turbine blades may causes various problems in our daily life.It is therefore highly desirable to develop new strategies for preventing ice formation and deicing efficiently.Compared with the chemical and mechanical methods for deicing,the photothermal deicing has the advantages of high efficiency,environmentally friendly and causing no damage to the surface.In this dissertation,the micro-/nano structured replicas with higher passive anti-icing and active deicing functions were rapidly prepared by injection-compression molding(ICM).Then,The light trapping effects of the micro-/nano structures on replica surface were investigated and explored its influence on the photothermal conversion efficiency of the replica,while the photothermal deicing/defrosting performances of the replica surface were also investigated.The beryllium-copper alloy plate with nano-sheets on its surface was prepared by chemical deposition,which was used as the mold template.The polypropylene/multi-walled carbon nanotubes(PP/MWCNTs)composite replicas with densely distributed nanohairs on their surfaces were rapidly prepared by ICM.It was demonstrated that the nanohairs endowed the replica surface with superhydrophobicity(a contact angle of 159.2°)and extremely low adhesion(a roll angle of less than 3°).Both the MWCNTs and nanohairs effectively reduced the reflectance on the replica surface(the average reflectivity was only 5.5%in the wavelength range of 300～800 nm)and promoted the replica to absorb sunlight(its average surface temperature was raised from 0°C to 77.4°C under 1 sun(1 k W/m~2)illumination for 300 s).Both the wetting state and efficient photothermal conversion endowed the replica with higher anti-icing and deicing/defrosting abilities.The freezing time of water droplet on the replica surface was prolonged significantly and the ice droplet was quickly removed under 1 sun illumination.During photothermal defrosting,the frost fragments on the replica surface curled into spherical melting droplets,and melting droplets spontaneously slid.The surface coverage fraction of the melting droplets was only 7.5%at the end of fully defrosting.The hierarchical pyramid beryllium-copper plate was prepared by precision milling and chemical deposition,which was used as the mold template.And then,the hierarchically structured PP/MWCNTs replica with inverted pyramid were rapidly molded by ICM.It was demonstrated that the reflectance on the replica surface was effectively reduced(the average reflectivity on replica surface with 0.5 wt%MWCNTs was only 2.2%in the wavelength range of 300～800 nm)and the photothermal conversion performance was improved(its average surface temperature was raised from 0°C to 85.4°C under 1 sun illumination for 300 s)under the combined effects of the MWCNTs and the hierarchical structure with inverted pyramid.Both the increase of MWCNTs contents and illumination intensities can effectively improve photothermal conversion of the replica.The hierarchical structure with inverted pyramid endowed the replica surface with superhydrophobicity(a contact angle of 163.0°),extremely low adhesion(a roll angle of less than 2°)and stable anti-wetting properties.The replica surface remained superhydrophobic after compressed for 10 cycles under 100 N pressure or abrased by sandpaper for 2000 mm under 3 k Pa pressure.Both the stable wetting state and efficient photothermal conversion endowed the hierarchically structured PP/MWCNTs replicas with higher anti-icing/anti-frost and deicing/defrosting functiones.The freezing time of water droplet and frosting time on the replica surface was prolonged significantly.Water droplet can rebound off the surface of the replica at–20℃.The ice layer with thickness of 3 mm was melted within 17.1 min under 1sun illumination.During photothermal defrosting,the frost fragments on the replica surface curled into spherical melting droplets,and melting droplets spontaneously rotated and slid.The diameter of the melting droplets gradually decreased and spontaneously slid and jumped during the photothermal evaporation process,and the melting droplets completely evaporated under 1sun illumination 8.2 min. |
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