Atmospheric pressure air plasma treatment of glass substrates for improved silver/glass adhesion in solar mirrors

摘要

Atmospheric pressure air plasma treatment was applied to glass substrates to improve the adhesion of the reflective silver layer of mirrors used in solar power systems. This treatment attempts to prevent problems related to the detachment of this layer that affect its energy performance. Untreated and plasma treated glass substrates were subjected to a spray coating process to fabricate mirrors. Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and measurements of the water contact angle (WCA) were undertaken on the glass substrates before the plating process. The reflectivity of the mirrors was studied by spectrophotometry in the wavelength range of 280-2500 nm, and the adhesion between the glass substrates and the silver layers was measured by pull-off tests. In order to determine the relationship between the parameters of the plasma treatment and the adhesion and reflectivity of the mirrors, different combinations of treatment speeds and gap distances between the glass substrates and the plasma nozzle were used. It was observed that the plasma treatment has a cleaning effect and forms oxygen-based functional groups that promote the hydrophilicity of the glass substrates. This double effect resulted in improved adhesion of the silver layer to the plasma treated substrates, with no significant loss of solar reflectance of the mirrors. The plasma treatment with the lowest gap distance (2 mm) and the lowest speed (1 m/min) achieved the best results in this work. It brought an improvement of 85.8% in the breaking strength of the untreated glass mirror and no significant variation in the solar reflectance in as-fabricated conditions. After accelerated aging, it maintained an improvement of 27.2% in the breaking strength and showed higher solar reflectance than the untreated glass mirror.