Improvement of the surface state of a sandblasted glass by deposing a thin layer of SiO2 using sol-gel technique

In Sahara, sandstorms are responsible for the surface degradation of a great number of objects in particular brittle materials such as ceramics and glasses. In the case of glass for example, impacts induced by sand particles on the surface causes a more or less severe damage. Generally, there is formation of surface microcracks, similar to those induced by Vickers indentation. When the sandstorms duration increases, it produces erosion that leads to the formation of damaged zones. This latter greatly reduces the optical transmission by scattering the incident light. Previous works [1,2] have shown that the glass surface state plays an important role in the various uses of glass sheets (vehicles windshields, planes sensors, various glazing, . . . ), because it affects their mechanical and physical properties [2]. In most applications, the glass surface is exposed to a variety of external aggressive conditions such as corrosion, chemical reactions and mechanical damage. Ruff and Wiederhorn [3], Hutchings [4] and other authors have reported that the erosion of brittle materials, such as glasses, is affected by many factors: the properties of incident particles (i.e. size, shape, density, hardness and fracture toughness); the properties of target materials (i.e. hardness, fracture toughness and surface state), and test conditions (i.e. impact velocity, impact angle and temperature). During sandstorms, all these different parameters are involved at the same time and with a very randomly manner (wide range of grains size, shape of the grains highly variable, variable velocities during the same storm, variable impact angles...). This makes the erosion process very complex. These parameters are governed by the winds turbulence recorded at ground level. Indeed, the presence of dunes with variable sizes or sometimes habitations leads to random blasts of wind. Different techniques have been proposed to reduce the surface roughness of glasses. Among these techniques, one can include [5]: mechanical polishing, fire polishing, chemical polishing by HF acid. Coating techniques were also deposited on glass and ceramics (polymer layers, metal oxides) [6].