Vickers Crack Nucleation of Glass Sheets Coated by Thin Silica Gel Layers

SiO₂ gel layers of different thickness have been deposited on glass sheets by dipping from gelling solutions with different concentrations of silicon alkoxide. Some mechanical properties of the coated samples such as hardness (H), elastic modulus (E), crack formation tendency, and tensile stress in the film (σ) have been measured by microindentation techniques and slide deflection. SiO₂ films deposited from more dilute solutions had lower H, E, and σ values, accounting for the observed higher resistance to crack nucleation in comparison with that found for samples prepared from more concentrated solutions.