Thin Solid Films, Vol.669, 487-493, 2019
Simultaneous chemical vapor deposition and thermal strengthening of glass
In the current paper we present a concept combining metal organic chemical vapor deposition with thermal strengthening process of flat glass. As the flat glass is heated to be thermally strengthened, which takes up to 20 minutes, there is an opportunity for performing a surface modification. We describe the application of transparent and amorphous Al2O3 thin films during the thermal strengthening process. Al2O3 was chosen due to the following desirable properties: increased surface mechanical properties and increased chemical durability, the latter has not been investigated in the current paper. The residual surface compressive stresses after performed strengthening of the coated glasses were quantified to be in the range of 80-110 MPa. The Al2O3 content in the surface was measured using the Surface Ablation Cell employed with Inductively Coupled Plasma Atomic Emission Spectroscopy and found to be at least doubled at the surface and having an increased Al2O3 content at least 0.5 mu m underneath the glass surface. During the surface reaction, sodium is migrating to the surface giving a hazy salt layer on the glass which can easily be washed off with water. The applied coatings are transparent and provide increased surface hardness and crack resistance at low indentation loads. At higher indentation loads the interaction volume is larger and displays the same effect on the surface mechanical properties as for thermally strengthened glass. The contact angle with water compared to annealed float glass is significantly increased from 5 degrees to 45 degrees due to the different surface chemistry and surface topography.