Preparation, durability and thermo stability of hydrophobic antireflective coatings for solar glass covers

In this paper, SiO2 coatings were prepared with sol gel method based on base catalysis. The optical transmittance of the soda-lime glass was improved more than 7% by optimizing sol concentration and aging time while the refraction index and thickness of anti-reflecfive coatings (ARCs) were 1.227 and 107 nm, respectively. The surface modification of the coatings with Hexamethyldisilazane (HMDS) was investigated. The static contact angle values increase from 22 degrees to 130 degrees after the modification, while the average transmittance decreases slightly. The SEM images show agglomeration significantly reduced after modification while silica particle size and structure changed little. FT-IR spectra show -CH3 in HMDS was covalently bonded to silica particles in the covalent reaction with Si-OH resulting in the improvement of hydrophobicity. The STA-IR analysis shows modified SiO2 ought to be annealed at 300 degrees C to eliminate metal alkoxide and solvent. And the -CH3 covalently bonded to silica particles began to be destroyed about 350 degrees C and severe damaged at 450 degrees C. Finally, brine pollution and corrosion resistance tests show that ARCs modified by HMDS have better self-cleaning ability and brine corrosion resistance than usual porous SiO2 coatings. (C) 2015 Elsevier Ltd. All rights reserved.