Optimization of synthesis parameters of mesoporous silica sol–gel thin films for application on 2024 aluminum alloy substrates

Silica mesoporous films were synthesized via Evaporation Induced Self-Assembly (EISA) using Pluronic P123 as templating agent and were applied on 2024 aluminum alloy for surface treatment applications. The removal of the P123 from the film required to convert the mesostructured film into a mesoporous film was particularly studied and optimized in order to be compatible with the use of an aluminum substrate. In this work, two different kinds of removal treatments were compared: calcination at high temperatures and UV/ozone treatment. Indeed, a minimum temperature of 275 °C has to be reached to completely remove the templating agent from the film. However, this treatment also leads to a decrease in mechanical properties of the aluminum substrate. In opposition, the removal by UV/ozone illumination allows getting mesoporous films at room temperature with important pore volume and high specific surface area without impacting mechanical properties of the aluminum. The effect of these treatments on mechanical properties of bare aluminum was followed by microhardness. The development of the porosity inside the film due to the elimination of the P123 was measured by combining analytical techniques (Fourier transform infrared spectroscopy FTIR, radio-frequency glow discharge optical emission spectroscopy RF-GDOES), electrochemical impedance spectroscopy (EIS) and adsorption porosimetry using a quartz crystal microbalance.