Transparent and Hydrophilic TiO₂ Anatase as Top-Protective Layer for CSP Reflectors

Abstract:

Titanium Dioxide is an important material that is used in many industrial applications such as photo-catalysis, glass-defogging, self-cleaning, waste water purification and anti-bacterial sterilization. The strong photo-catalysis of TiO₂, and therefore its ability to decompose dirt and organic contaminants makes it an excellent top-protective layer candidate for CSP reflectors. The aim of this study consists of the deposition of a transparent and hydrophilic TiO₂ layer on top of the Concentrated Solar Power (CSP) mirrors without altering their specular reflectance. The strong photo-catalysis and hydrophilicity of TiO₂ will decompose the dirt and organic matter on the surface of the mirrors, which would be cleaned away from the reflectors’ surface by rain, therefore minimizing the use of water for cleaning the CSP mirrors.In this study, polycrystalline anatase TiO₂ layers were deposited on glass substrates with different thicknesses. The contact angle measurements show that the hydrophilicity of TiO₂ increases with increasing surface roughness, with Water Contact Angle (WCA) of 52°and 30° for 48 nm and 100 nm, respectively. Super-hydrophilicity (WCA < 5°) was achieved for thicker TiO₂ layers, with WCA of 8° and 1° for 177 nm and 220 nm, respectively. The deposition of a 48 nm-thick TiO₂ layer on glass showed a high transmittance in the visible and Near Infrared (NIR) range (75%), whereas the transmission decreased with increasing thicknesses of TiO₂. Therefore, a TiO₂ layer of 48 nm thickness is suggested in this study as a hydrophilic top-protective layer since it preserved the specular reflectance of the mirrors (97.5%) in the NIR range, compared to 98.6% without the TiO₂ layer.

• Periodical: Advanced Materials Research (Volume 1119)
• Pages: 355-359
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1119.355
• Online since: July 2015
• Authors: Houda Ennaceri*, Asmae Khaldoun, Abdelilah Benyoussef, Tristan Köhler, Rodrigo Sáez-Araoz, Ahmed Ennaoui
• Keywords: CSP, Hydrophilicity, Self-Cleaning, Specular Reflectance, TiO₂ Anatase

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