Study On Preparation And Properties Of Close Pore Sol-gel Antireflective Coatings

The requirement of energy is increasing as the decrease of the non-renewable resources,the attention of the explore and utilize of renewable resources was caused.The solar energy was concerned as a clean and renewable sources,especially the effective utilization of solar energy.The biggest challenge of the using of solar energy is the energy loss caused by the reflect of components.In order to decrease energy loss coursed by reflection of components,the antireflective technology often was applied to increase the transfer efficiency of photovoltaic or optothermal.The study of antireflective?AR?coatings has been a significant research subject for the effective utilization of solar energy.In this paper,the hollow silica nanospheres?HSNs?and HSNs sols were prepared by sol-gel using PAA as template.The high transmittance,scratch resistance and weather ability AR coatings using HSNs sols mixed with acid-catalyzed silica?ACS?sols.The ACS sols was modified in order to form bigger pores,but the size of pores under moisture absorption threshold value,the transmittance of AR coatings was improved.In this paper,the template was removed by centrifugal washing which is different with what have been reported that the template was removed by calcine.The template could be removed totally.The preparation of hollow silica nanospheres?HSNs?,the preparation of acid-catalyzed silica?ACS?sols and modified ACS sols,the preparation of AR coatings using HSN sols mixed with ACS sols and the preparation of AR coatings using HSN sols mixed with modified ACS sols were studied.In this paper,the influence factors of the forming of HSNs were studied,the main factors were the dosage of NH₃·H₂O,the dosage and molecular weight?Mw?of PAA and the dosage of TEOS.The HSNs prepared using different Mw PAA were compared,the quality was best when the HSNs were prepared using Mw 50000 PAA as templates.The ACS sols and modified ACS sols were made,the AR coatings were made using ACS sols or modified ACS sols,the influence factors of sols preparation were analyzed by analyzing the transmittance of AR coatings.According to the analysis,the thickness of AR coatings increased as the amounts of HCl increasing,which indicated the amounts of HCl would influence the viscosity of sols.The amounts of precursor also could affect the viscosity of sols,because it was only the thickness of AR coatings increased,the transmittance of AR coatings did not change.The wavelength corresponding to the peak transmittance changed,but the transmittance value did not change under different aging time,it could be known that the aging time only affected the viscosity of solsIn this paper,the HSN AR coatings were prepared using HSN sols hybridized ACS sols.The influence of the amount of ACS sols on transmittance,uniformity,mechanical performance,durability and antifogging characteristics of the HSN AR coatings were investigated systematically.When the ratio of HSN sols to ACS sols was 9:2,the performances of the HSN AR coatings was the best as a whole.The transmittance was 97.7%at peak value and the mechanical performance was 6H pencil hardness.It could resistant high moisture and high temperature,and the transmittance decreased to 98.8%of the initial value after the temperature and humidity stress test?HAST?.It also possessed good hydrophilic and antifogging characteristic.The water contact angle?WAC?declined from 13.1°to approximately 5.8^o only after 0.47s.This kind of HSN AR coatings had a potential to be applied in outdoor photo-voltaic and photo-thermal area.In this paper,the AR coatings were prepared using HSN sols hybridized modified ACS sols.The HSNs were obtained by optimal experiment,so that the transmittance of HSN AR coatings have been the highest value.However,the transmittance of AR coatings decreased obviously when HSN sols mixed with ACS sols for the low porosity of ACS sols.It is possible to improve the transmittance of mixed sol AR coatings by modifying the ACS sols.The modified ACS sols were made using tetraethoxysilane?TEOS?as the silica inorganic precursor,methyltrimethoxysilane?MTMS?as the silica organic precursor and N,N-dimethylformamide?DMF?as the chemical additive.The transmittance of AR coatings were improved markedly when the AR coatings were prepared using HSN sols hybridized modified ACS sols compared with that prepared using the HSN sols hybridized unmodified ACS sols.The transmittance peak value were increased to 99.1%,98.4%and 97.4%respectively with the ratio of 9:1,9:2and 9:3 that HSN sols to modified ACS sol.The hardness,durability and antifogging characteristic of AR coatings with different ratios almost did not be influenced when the transmittance was improved.This kind of AR coatings is more suitable to be used in outdoor photo-voltaic and photo-thermal area.