Synthesis And Properties Of Superhydrophilic And Superhydrophobic Thin Films Used In Reflector Of Concentrating Solar Power

Inexhaustible solar energy resources will play an important role to solve the energy problem in the future.Reflector is the core component of concentrating solar power.However,Dust from atmospheric can deposite on the surface of the reflector easily because the reflector is exposed to the atmospheric conditions directly,which reduce the reflectivity,and then increase the cost.It is very important to keep the reflector clean.Titanium dioxide porous films with natural super-hydrophilic performance were successfully deposited on glass slides through the neutralization of ammonia and nitric acid which drived phase separation by sol–gel spin coating method.The relationship between natural hydrophilic property and sol composition as well as heat treatment processing was studied in detail.The surface morphology,phase structure transmittance and hydrophilicity of the films were characterized by super depth of field microscopy,X-ray diffractometer,UV-VIS-NIR spectrophotometer and water contact angle apparatus.Besides,thin films for self-cleaning and antifog performance were studied.The results of this study indicate:?1?TiO₂ thin film without ammonia or nitric acid did not exhibit superhydrophilic characteristic with flat surface,Meanwhile,the pore TiO₂ thin film showed super-hydrophicity;?2?the TiO₂ porous thin films annealed over 450?for 60 min with good crystalline anatase structure exhibited a natural super-hydrophilic property with the water contact angles less than 5°without UV irradiation;?3?the transmittance of porous TiO₂ films decreased with the increases of pore size.Superhydrophobic films were successfully deposited on glass slides after silicon dioxide films were modified by trimethylchlorosilane?CTMS?,octadecyltrichlorosilane?OTS?and perfluoroaltrichlorosilane?PTFS?.The relationship between natural hydrophobic property and.the surface modification time was studied in detail.The surface morphology,surface chemical composition and hydrophobic of the films were characterized by field-emission scanning electron microscope,Fu Liye transform infrared spectrometer,UV-VIS-NIR spectrophotometer and water contact angle apparatus.The results of this study indicate:?1?before modified,SiO₂ thin films had obvious porous structure which is 50-70 nm by sol–gel spin coating method,and after modified,SiO₂ thin films had rearranged which can decreas the surface energy;?2?the SiO₂ thin films modified over 3h by OTS exhibited superhydrophobic property with the water contact angles more than 150°and roll angle less than 5°.Besides,the water contact angles of SiO₂ films modified over 1h by PTFS also more than 150°,but unfortunately the rolling angle more than 10 degrees.Furthermore,it did not exhibited superhydrophobic property modified by CTMS with the water contact angles just122°;?3?The transmittance of SiO₂ films increased for the nano-pore structure.Finally,superhydrophilic TiO₂ porous films and superhydrophobic OTS-SiO₂films were deposited on surface reflector.The effect of self clean film on reflectivity was studied.It was found that super-hydrophilic TiO₂ porous films can reduce the reflectivity.However,the superhydrophobic OTS-SiO₂ films increase the reflectivity.