DEVELOPMENT OF ALUMINUM 1ST SURFACE MIRRORS FOR SOLAR-ENERGY APPLICATIONS

The progress in obtaining first surface mirrors by using Si2O3 and SiO films as the front surface over aluminum films thermally evaporated over soda lime glass substrates is given in this study. The size of the mirrors is 30 x 30 cm with a 3-mm substrate thickness. A glow discharge produced during 20 min (3 kV and 250 mA) was sufficient to clean the substrate. An aluminum film was deposited after this cleaning. Two types of first surface mirrors were formed. One with SiO, and the other one with Si2O3 as the front surface, each one with a thickness of about 3000-angstrom. The reflectances were 0.82 and 0.86, respectively. After one year of exposure to the environment, no degradation was detected, but after two years, a slight amount of corrosion appeared. Some alternatives are being studied in order to minimize or eliminate this corrosion.