The LIMES project (Light Innovative Materials for Enhanced Solar Efficiency), a Solar-ERA.NET project, have been a fruitful collaboration project to optimize many different properties in state-of-the-art solar glasses for photovoltaic (PV) modules. Here, we present results related to the effectiveness of reactive gas strengthening and its improvement of the physical properties of thin glasses. Novel thermo-chemical strengthening has been created using reactive chemicals that react with the glass surface during the thermal strengthening process. The glass surface gets a markedly increase of Al₂O₃, which in previous studies has been shown to have a beneficial effect on the mechanical properties. Successful thermo-chemical strengthening of 4 and 2 mm glasses to a similar strengthening level have repeatedly been performed, polariscope images in Figure 1. The strengthening level has been quantified using SCALP (Scattered Light Polariscope) and were found to be in the range of 85-110 MPa of compressive stresses in the surface which are comparable to values for conventional thermally strengthened glass.

The strength of the glasses was quantified using the ring-on-ring method and the surface mechanical properties were evaluated by means of nano/microindentation. UV-Vis spectroscopy measurements have also been performed.

Results for the ring-on-ring tests show that the 2 mm thin glass were positively affected by the while 4 mm did not show any significant change as compared to thermally strengthened. The thermo-chemically strengthened glasses have a significantly higher crack resistance than both the reference float glass and the traditionally thermally strengthened glass. The hardness results show that for low loads, ≥1 mN, the hardness follow the order thermo-chemically strengthened glass > thermally strengthened glass > annealed float glass. The scratch resistance for thermo-chemically strengthened glass is increased as compared to ordinary float glass. In addition, the transmission is not markedly reduced.