Experimental and Computational Synthesis of TiO2 Sol-Gel Coatings.

During the experimental formation of sol-gel coatings, the colloid dispersions go through a drying process, and the structure of the coatings is formed as a result of complex chemical, colloidal, and capillary interactions. While computer simulations provide guidelines to tune and even design the nanomaterials synthesis, simulations of coating structure formation are hitherto unknown in the literature. Based on real experiments, we establish here a ReaxFF reactive force field-based molecular dynamics simulation protocol in order to investigate and determine the role of the experimental conditions on the pore structure formation in the coatings. Anatase TiO2 sol-gel coatings with a thickness of 50 nm, 7% open porosity, and a 2.4 nm pore radius were prepared on solid substrates using the dip-coating method. In the computational synthesis of porous TiO2 layers, the attractive capillary forces present during the drying step were accounted for by applying an external pressure, and their effect on the coatings' pore structure was investigated. It was found that the TiO2 layer structure corresponding to an external pressure of 10,000 atm in the simulations exhibited a porosity comparable to that determined by experimental methods. This demonstrates the impact of immersion capillary forces on sol-gel layer formation. The created computer model accurately describes the layer structure using real parameters, making it suitable for designing the coating structure through computer simulation.